Organic light emitting element, organic light emitting display device, and method of manufacturing the organic light emitting display device

This application claims priority to and the benefit of Korean Patent Application No. 2012-0155868, filed on Dec. 28, 2012, the disclosure of which is incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates to an organic light emitting element (referred hereinafter as “OLED element”) with improved light output rate, power consumption and lifespan and organic light emitting device employing the OLED element, as well as a method of manufacturing such OLED element and device.

2. Discussion of Related Art

An organic light emitting diode device (sometimes referred to as OLED device) is a self-emitting display device. Unlike the liquid crystal display (LCD) display device, it does not require an additional light source, and thus the OLED device can have much thinner and lighter profile than the LCD display device. Not only is the OLED device consumes less power than the typical LCD based display device, it provides better color accuracy, faster response rate, greater viewing angle, and higher contrast ratio (CR). Accordingly, a lot of research has been performed into developing more efficient emissive materials and OLED structures.

An OLED device commonly includes a substrate, an anode, a hole-transporting layer made of an organic compound, an organic luminescent layer with suitable dopants, an organic electron-transporting layer, and a cathode. When current is applied, electrons flow from the cathode to the anode. That is, the cathode provides electrons into the electroluminescent layer (EL layer), while the anode removes electrons from the EL layer, leading to holes in the EL layer. The electrons provided from the cathode combine with the holes in the EL layer and create excitons. This process releases photons, and thus light is generated. Different types of emissive materials can be used to change the color of the light. The intensity of the light is controlled by the amount of current applied.

Some OLED device employs organic light emitting elements configured with different luminescent layer(s) to emit a designated color of light (e.g., red, green, or blue) at a corresponding sub pixel region. In such OLED device, each OLED element emits designated color without using color filter elements, high luminance can be obtained from the OLED element. However, this type of OLED device (referred hereinafter as “RGB type”) requires the OLED elements to be disposed according to the sub pixel design of the display device, thereby severely limiting its application.

Unlike the RGB type, some OLED device employs white light producing luminescent layer in conjunction with red, green and blue color filter elements at the red, green and blue sub pixel regions (referred hereinafter as “RGBW type”). This configuration makes it easy to fabricate the OLED device for a variety of applications.

There is a tradeoff between the color saturation, the driving current, the luminance and the lifetime of the OLED device. In case of RGBW type OLED, the luminance of the OLED element is sacrificed as the white light from the OLED element passes through the color filter elements. In order to compensate the reduced luminance, higher current density is provided. Such increase in current density, however, leads to shortened lifetime of OLED element and undesirable color shifts as the display device ages.

Further, the color coordinates of the white light emitted from the OLED element can be distorted if the luminance of a certain emission layer becomes lower than the luminance of the other emission layers or the color coordinate of a certain emission layer deviates from its initial preferred setting. For example, if the luminance of an EL layer that emits blue light is lower than that of the other EL layers that emit other colored light, the OLED element may not emit the white light with the ideal color coordinate.

The driving voltage of the OLED element can be adjusted to correct such color coordinate shift caused by a certain emission layer. However, not only is the algorithm for correcting color coordinates require very complicated arithmetic operations, this method often involves increasing the current level at the white sub pixel region as well as some of the other pixel regions in order to correct the overall color saturation. This results in increased power consumption of the entire panel and reduced lifespan of the EL layer. Using a low-power driving algorithm following the aforementioned calibration significantly complicates the overall operation. Even if such algorithms can be performed, other side effects may occur.

Accordingly, there remains a need for white OLEDs having excellent emission efficiency and long life-spans.

A white OLED element can be designed with two or more EL layers. Lights emitted from a plurality of EL layers are combined to form white light. The inventors of the present invention has recognized that when white light passes through color filters, the white light is absorbed by the color filter elements, thereby lowering the efficiency of an OLED element. In particular, in the case of white light passing through a blue color filter element, the inventor has recognized that efficiency of the blue light is sharply decreased according to the transmittance of the color filter element.

Accordingly, a display device with improved emission efficiency and increased life-span is provided. The display device includes a multi-layered emission layer structure having a blue electroluminescent (EL) layer and a complementary EL layer. The blue EL layer is configured to emit substantially blue light (e.g., light with a wavelength between from about 380 nm to about 495 nm, more preferably from about 450 nm to about 495 nm, referred hereinafter as “blue light”) at one part of the multi-layered emission layer structure, and the complementary EL layer is configured to emit light that complements the blue light such that the blue light from the blue EL layer and the light emitted from the complementary EL layer collectively form substantially white light at another part of the multi-layered emission layer structure. The complementary EL layer is not disposed in the part of the multi-layered emission layer structure relative to the blue pixel of the display device. The order in which the blue EL layer and the complementary EL layer are disposed within the multi-layered emission layer structure can vary depending on the emission type of the OLED element (e.g., top-emission, bottom-emission) employed by the display device.

The display device further includes a red color filter element and a green color filter element that are positioned to filter the white light from multi-layered emission layer structure to generate red and green light, respectively. The display device has a plurality of pixels such as one or more of red pixels, one or more of green pixels and one or more of blue pixels. The white light emitted from the part of the multi-layered emission layer structure is filtered through the red color filter element and transmitted at the red pixel(s) of the display device. Similarly, the white light emitted from the part of the multi-layered emission layer structure is filtered through the green color filter element and transmitted at the green pixel(s) of the display device. At the blue pixel(s), however, the blue light emitted from the part of the multi-layered emission layer structure is transmitted.

In this setting, the blue pixel of the display device does not transmit blue light generated by filtering the white light from the multi-layered emission layer structure. Instead, the blue light from the blue EL layer of the multi-layered emission layer structure can be transmitted at the blue pixel of the display device without being filtered by a color filter element, and thereby increase the luminance of the blue light without increasing the driving voltage/current.

Further, some embodiments of the display device may include a blue color filter element that filters the blue light emitted from the blue EL layer and transmit the filtered light at the blue pixel(s) of the display device. By using the blue color filter element, the saturation and/or color coordinate of the blue light from the blue EL layer can be adjusted more precisely. This also provides greater flexibility in pixel layout designs as well as improvement in overall color accuracy of the white OLED element. Unlike the situation where white light is filtered by a blue color filter element to generate blue colored light, the luminance of the blue light is substantially maintained because the blue light from the blue EL layer is being filtered by the blue color filter element.

In some embodiments, the complementary EL layer is disposed in the part of the multi-layered emission layer structure relative to the red and green pixels. The blue EL layer is disposed on the complementary EL layer to overlap with the complementary EL layer and extends further into the other part of the multi-layered emission layer structure. In other words, the part of the multi-layered emission layer structure that emits the white light has the blue EL layer disposed on top of the complementary EL layer while the part that emits the blue light has does not have complementary EL layer disposed therein.

Alternatively, in some other embodiments, the blue EL layer is disposed in both parts of the multi-layered emission layer structure, and the complementary EL layer is disposed on a part of the blue EL layer. The overlapping part of the multi-layered emission layer structure emits light from the blue and complementary EL layers to collectively form the white light, whereas the non-overlapping part of the multi-layered emission layer structure emit the blue light from the blue EL layer.

The blue EL layer as well as the complementary EL layer of the multi-layered emission layer structure may be formed of one or more of EL layers with one or more of organic materials. In some embodiments, the complementary EL layer includes a host doped with a red dopant and a green dopant. In some other embodiments, the complementary EL layer is made of a stack of a red EL layer and a green EL layer. Also, in some other embodiments, the complementary EL layer is made of a stack of an EL layer doped with a red phosphor dopant and another EL layer doped with a yellow phosphor dopant, whereas the blue EL layer of the multi-layered emission layer structure is doped with a blue fluorescent dopant.

In some embodiments, the multi-layered emission layer structure may include a charge generation layer (CGL) interposed between the blue EL layer and the complementary EL layer. The CGL may be composed of an n-doped layer and a p-doped layer for injection of electrons and holes, respectively. When the OLED element of the display device is turned on, electrons and holes are supplied from the CGL to start the EL layers for electroluminescence. At the subsequent stage, the consumed electrons and holes in the CGL are refilled by the electrons and holes injected from the cathode and anode, respectively.

The plurality of pixels employed by some embodiments of the display device may include one or more of white pixels. In the white pixels, the white light emitted from the part of the multi-layered emission layer structure is transmitted without being filtered by color filter elements. In some embodiments, however, the white light from the multi-layered emission layer structure may be passed through a transparent resin layer, which may protect the EL layers and/or planarize the surface of the multi-layered emission layer structure. Similar to the unfiltered blue light transmitted at the blue pixel of the display device, unfiltered white light transmitted at the white pixel may be utilized in calibrating the overall luminance and the color saturation of the display device.

Also, in some embodiments, the display device may include individually addressable anode in each of the plurality of pixels so that the part of the multi-layered emission layer structure relative to a specific pixel of the display device can be separately driven.

In another aspect, the present invention is directed to a white OLED element with improved emission efficiency and increased life-span. The white OLED element includes at least two areas. In each of the areas, at least one anode is disposed therein. The anodes in the first and second areas are individually addressable such that the part of the white OLED element at each of the anodes can be separately controlled (e.g., EL layers on the individual anode can be separately activated to emit light). Further, a blue EL layer for emitting substantially blue light is disposed on the first and second areas of the white OLED element. Additionally, a complementary EL layer, which is configured to emit light complementary to the blue light, is disposed on the first area of the white OLED element. Accordingly, in the first area, the light from the blue EL layer and the light from the complementary EL layer are combined to form white light. The white OLED element further includes a cathode disposed in both the first and second areas to provide electrons to the EL layer(s) in the respective area of the white OLED element. At least one color filter element is included in the white OLED element to filter at least some of the combination of light from the blue and complementary EL layers (i.e., the white light), and transmit colored light corresponding to the color filter element. In the second area, the blue light emitted from the blue EL layer is substantially unaffected by the light emitted from the complementary EL layer disposed in the first area of the white OLED element. That is, the shift in the wavelength value of the blue light emitted at the second area is less than 100 nm, more preferably by less than 50 nm, more preferably by less than 30 nm, and even more preferably by less than 10 nm.

In some other embodiments, the complementary EL layer is made of multiple EL layers that include a red EL layer that emits substantially red light (e.g., light with a wavelength between from about 580 nm to about 750 nm, more preferably from about 590 nm to about 750 nm, and more preferably from about 620 nm to about 750 nm), and a green EL layer that emits substantially green light (e.g., light with a wavelength between from about 496 nm to about 579 nm and more preferably from about 496 nm to 570 nm). In this setting, the combination of the red light from the red EL layer, the green light from the EL layer and the blue light from the blue EL layer, collectively, forms the white light. This white light is utilized in all pixels except the blue pixel of a display device where the complementary EL layer is not disposed thereon.

Also, in some other embodiments, the complementary El layer is made of multiple EL layers that include an EL layer doped with a red phosphor dopant and an EL layer doped with a yellow phosphor dopant. The blue light EL layer is doped with a blue fluorescent dopant, and the light emitted from these EL layers are combined to form the white light at the pixels excluding the blue pixel.

Some embodiments of the white OLED element include a white pixel, which is configured to transmit the white light from the multi-layered emission layer structure. As mentioned above, the white light at the white pixel can be utilized in correcting various properties of the white OLED element.

Further, some embodiments of the white OLED element include a blue color filter element that filters the blue light emitted from the blue EL layer. By using the blue color filter element, the saturation and/or color coordinate of the blue light from the blue EL layer can be adjusted more precisely. This provides greater flexibility in pixel layout designs as well as improvement in overall color accuracy of the white OLED element. Unlike the situation where white light is filtered by a blue color filter element to generate blue colored light, the luminance of the blue light is substantially maintained because the blue light from the blue EL layer is being filtered by the blue color filter element.

The white OLED element may be configured as a bottom emission type OLED element. In this setting, the lights from the blue EL layer and the complementary EL layer exit through the anodes disposed in the first and the second areas of the white OLED element. Alternatively, the white OLED element is configured as a top emission type OLED element. In this setting, the light from the blue EL layer and the complementary EL layer exits from the white OLED element through the cathode disposed in the first and the second areas of the white OLED element. Further, in some embodiments, the white OLED element may be configured to emit light in both top and bottom directions. The improved luminance and color saturation achieved by the white OLED of the present disclosure can be especially useful in a transparent display device, which may employ such dual emission type white OLED element.

The configuration of EL layers in the multi-layered emission layer structure is not limited to the specific exemplary embodiments of the present disclosure, but may vary by considering various properties of the EL layers that form the multi-layered emission layer structure without departing the spirit of the present invention. The properties of the EL layers that can be considered in configuring the EL layers within the multi-layered emission layer structure may include, but are not limited to, the luminance, the color accuracy, the power consumption, the life span and various other factors of the individual EL layers and/or the multi-layered emission layer as a whole.

Accordingly, in one other aspect, the present invention is directed to a display device having a multi-layered emission layer structure including at least a part being configured to emit a light from a principal EL layer and at least at one other part configured to emit a combination of light emitted from the principal EL layer and the complementary EL layer. The light from the principal EL layer has a wavelength value of a predetermined range. The light from the complementary EL layer is complementary relative to the light emitted from the principal EL layer so that the combination of light from the principal EL layer and the complementary EL layer is substantially white light. One or more of color filter elements are used to filter the white light emitted from the part of the multi-layered emission layer structure. At least one of a red pixel, a green pixel and a blue pixel is configured to transmit the white light that is filtered through a corresponding color filter element. For instance, the principal EL layer may be configured to emit red colored light and transmitted at the red pixel of the display device. In this setting, the white light generated by combining the light emitted from the principal EL layer and the light emitted from the complementary EL layer is filtered through blue and green color filter elements to generate blue and green light to be transmitted at the blue and green pixels of the display device, respectively.

As mentioned, the principal EL layer may emit other colored light, such as green or blue colored light. It is sufficient that the principal EL layer covers larger area in the multi-layered emission layer than the complementary EL layer such that the portion of the principal EL layer being extended out from the area covered by the complementary EL layer can emit the principal EL layer's constituent colored light without being substantially affected by the light from the complementary EL layer. That is, the shift in the wavelength value of the blue light emitted at the second area is 100 nm, more preferably less than 50 nm, more preferably less than 30 nm, and even more preferably by less than 10 nm.

In yet another aspect, the present invention is directed to a method of manufacturing a display device with improved emission efficiency and increased life-span. First, a plurality of anodes is formed on a substrate so that each of the anodes is individually addressable. Then, a first electroluminescent (EL) layer and a second electroluminescent (EL) layer are formed on the anodes such that at least a part of the first EL layer and the second EL layer are overlapped at the first area (e.g., an area for emitting substantially white light) of the display device. Here, at least one of the first EL layer or the second EL layer should be formed such that it is extended out to a second area (e.g., an area for emitting constituent colored light of the EL layer) without being overlapped with the other EL layer. A cathode is formed on both the first area and the second area so that the first EL layer and the second EL layer are interposed between the plurality of anodes and the cathode. Then, one or more of color filter elements are arranged to filter the light emitted from the first area.

In this setting, the EL layer being extended out to the second area may emit its own colored light without being filtered by a color filter element while the stack of the first and second EL layers in the first area emits substantially white light, which is to be filtered by one or more of the color filter elements to generate colored light corresponding to the color filter element.

When forming the first and second EL layers, one of the first and second EL layers, which is to be extended out into the second area may be formed first. Then a photoresist may be formed on the EL layer in the second area. The photoresist in the second area is then developed. Following the development of the photoresist, the other EL layer that is to be left in the first area (i.e., complementary EL layer) is formed in the first and second areas. When the photoresist formed in the second area is stripped, the complementary EL layer formed in the second area is also stripped, thereby forming a multi-layered emission layer structure having the first area for emitting white light and the second area for emitting colored light of the EL layer. In some embodiments of the method, the photoresist developing solution and/or the photoresist stripper used in the process of forming the multi-layered emission layer structure contain fluorine, which may reduce the damage to the EL layers during the formation of the multi-layered emission layer structure.

As an alternative way of forming the multi-layered emission layer structure, one of the first and second EL layers can be formed in the first area, and the other EL layer can be formed on the EL layer in both the first and second areas. This method also results in a multi-layered emission layer structure with a stack of the first and second EL layers disposed in the first area for emitting the substantially white light and one of the first and second EL layers being extended into the second area for emitting colored light of the EL layer in the second area.

In one embodiment, the EL layer being extended out into the second area is an EL layer configured to emit substantially blue light, and the other EL layer, which is contained within the first area, is an EL layer configured to emit light having a color complementary to the blue light from the other EL layer. Accordingly, these two EL layers overlap at the first area and collectively emit substantially white light. In this embodiment, the plurality of color filter elements comprises a red color filter element and a green color filter element that are configured to filter the white light to generate red and green light, respectively. In other embodiments, the EL layer being extended out into the second area may be configured to emit substantially red or substantially green colored light, and the other EL layer being contained within the first area may be configured to emit light that is complementary to the red or green colored light. As such, the display device having a multi-layered emission layer structure with improved luminance, color accuracy, power consumption as well as the longer life span can be provided.

Additional features of the invention will be set forth in the description, which follows, and in part will be apparent from the description, or may be learned by practice of the invention.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

The accompanying drawings, which constitute a part of this specification, illustrate various embodiments of the present invention.

FIGS. 1A to 1C , each illustrates a cross-sectional view of an exemplary white OLED element according to an embodiment of the present invention.

FIGS. 2A to 2E , each illustrates a cross-sectional view of an exemplary white OLED element according to an embodiment of the present invention.

FIGS. 3A to 3F , each illustrates a cross-sectional view of an exemplary display device according to an embodiment of the present invention.

FIGS. 4A to 4D , each illustrates a cross-sectional view of an exemplary display device according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating steps for manufacturing an organic light emitting display device according to an exemplary embodiment of the present invention.

FIGS. 6A and 6B illustrate cross-sectional views of the exemplary display device during the steps of manufacturing such organic light emitting display device according to an exemplary embodiment of the present invention.

FIGS. 7A and 7C illustrate cross-sectional views of the exemplary display device during the steps of manufacturing such organic light emitting display device according to an exemplary embodiment of the present invention.

FIGS. 8A and 8C illustrate cross-sectional views of the exemplary organic light emitting display device during the steps of manufacturing such organic light emitting display device according to an exemplary embodiment of the present invention.

It is noted that the drawings of the present application are provided for illustrative purposes only and, as such, the drawings are not drawn to scale. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements.

The present invention, which provides an organic light emitting element with improved luminance efficiency and lifetime, and methods of fabricating such an organic light emitting element, will now be described in greater detail by referring to the following discussion and drawings that accompany the present application.

In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps and techniques, in order to provide an understanding of the various embodiments of the present disclosure. In other instances, well-known structures or processing steps have not been described in detail in order to avoid obscuring the present disclosure.

It will be understood that when an element as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

Further, it will be understood that when an element is referred to as being “overlapped” with another element, one element can be positioned above the other element or below the other element. Moreover, although some of the elements are designated with numerical terms (e.g., first, second, third, etc.), it should be understood that such designations are only used to specify one element from a group of similar elements, but not to limit the element in any specific order. As such, an element designated as a first element could be termed as a second element or as third element without departing from the scope of exemplary embodiments.

In the present disclosure, the organic light emitting display device includes one or more OLED elements, which can be configured to operate in one of a top, bottom or dual emission mode, depending on the direction light exits the OLED element. Accordingly, in the present disclosure, an OLED element is classified as bottom emission mode OLED element if the light emitted from the OLED element passes through a transparent or a semi-transparent bottom electrode and substrate on which the panel was manufactured. Also, an OLED element is classified as a top emission mode OLED element if the light emitted from the OLED element exits through a transparent or a semi-transparent top electrode. An OLED element can be classified as a dual emission mode OLED element if the light emitted from the OLED element exits through both the top and bottom electrodes to emit light on both sides of the OLED element. The components of the organic light emitting display device including, but not limited to, a thin film transistor, an anode, and a cathode as well as the structure of organic EL layer design, may be configured differently based on the aforementioned emission modes without departing from the spirit of the present invention.

Exemplary embodiments of the present application will now be described in greater detail by referring to the following discussion and drawings that accompany the present application.

FIG. 1A is a pictorial representation (through a cross sectional view) depicting a white OLED element 140 A that can be employed in one embodiment of the present application. FIG. 1A illustrates the white OLED element 140 A, which includes a plurality of anodes 141 A 1 , 141 A 2 and 141 A 3 (collectively denoted as 141 A), a multi-layered emission layer structure 144 A having a plurality of EL layers 144 A 1 and 144 A 2 , and a cathode 145 A.

The anode is an electrode configured to provide holes in the EL layers, and may also be referred to as a positive electrode, a pixel electrode or a first electrode. The white OLED element 140 A is configured to emit light when holes supplied from the anode 141 A and electrons supplied from the cathode 145 A are recombined in the EL layer(s) ( 144 A 1 , 144 A 2 ). As described above, the anode 141 A is configured to supply holes, and is thus formed of a conductive material having a high work function. Specifically, a material of the anode may depend on a light emission mode of the OLED element 140 A. For example, in a top emission mode OLED element, the anode 141 A can be formed of a material having high light reflective property, or formed with a material having transparent property with a reflective metal layer formed thereunder. In contrast, in a bottom emission mode OLED element, the anode 141 A is formed as a transparent electrode without the reflective metal layer.

As mentioned above, the white OLED element 140 A includes a first anode 141 A 1 , a second anode 141 A 2 and a third anode 141 A 3 . In this example, the first anode 141 A 1 is formed in an area relative to the first pixel region R, the second anode 141 A 2 is formed in an area relative to the second pixel region G, and the third anode 141 A 3 is formed in an area relative to the third pixel region B. The first anode 141 A 1 , the second anode 141 A 2 , and the third anode 141 A 3 are individually addressable. In other words, each anode can be independently driven to emit light in the corresponding pixel region. The one or more of the first, second and third pixels may form a unit pixel of the display device. Although the configuration of the pixels R, G and B are shown as in the specific order in linear fashion, it should be noted that the configuration (e.g., order, location, shape, etc.) of the pixels R, G and B may vary in a number of ways according to the display device employing the white OLED element.

The cathode 145 A is formed on the multi-layered light emission layer structure 144 A. The cathode 145 A may be also referred to as a negative electrode, a common electrode, or a second electrode. The cathode 145 A is formed on each of the first, second and the third pixel regions. The cathode 145 A is connected to an additional voltage wire to apply the same voltage to all the sub pixel regions. The cathode 145 A may or may not be patterned in units of the sub pixel regions.

As described above, the cathode 145 A is configured to supply electrons and is thus formed of a material having high electrical conductivity and a low work function, i.e., a material of a cathode. Similar to the anode 141 A, the material of the cathode 145 A can vary depending on the light emission type of an OLED element. For example, in a top emission type OLED element, the cathode 145 A may be formed of a very thin metal material having a low work function. In a bottom emission type OLED element, the cathode 145 A may be formed of a conductive material having a low work function and high reflectivity.

The multi-layered emission layer structure 144 A may have a structure including a hole injection layer (HIL), a hole transport layer (HTL), a plurality of EL layers, an electron transport layer (ETL), and an electron injection layer (EIL) that are sequentially stacked. Each EL layer within the multi-layered emission layer structure 144 A emits light having a different wavelength such that the light of the individual EL layers collectively form white light. In this case, the plurality of EL layers are arranged to overlap each other at a part of the OLED element 140 A except excluding at least one part of the OLED element 140 A.

The multi-layered emission layer structure 144 A includes a first EL layer 144 A 1 and a second EL layer 144 A 2 . The first EL layer 144 A 1 emits first colored light, and the second EL layer 144 A 2 emits second colored light. In the present disclosure, the example shown in FIG. 1A will be described as if the light emitted from the second EL layer 144 A 2 is blue. Since a part of the multi-layered emission layer structure 144 A emits substantially white light, the first color emitted from the first EL layer 144 A 1 is a color that can form white light when it is combined with the blue light of the second EL layer 144 A 2 . In other words, the wavelength of the light from the first EL layer 144 A 1 and the wavelength of the light from the second EL layer 144 A 2 complement each other. In the present disclosure, the term “substantially white light” refers to light that is a mixture of wavelengths of various colors and is perceived as colorless, which may be referred hereinafter as “white light”.

For convenience of explanation, white OLED element 140 A of the present disclosure is illustrated with only the first EL layer 144 A 1 and the second EL layer 144 A 2 that emit light that collectively form the white light. Also, in FIG. 1A , the first EL layer 144 A 1 is illustrated as a single EL layer emitting the first colored light (e.g., light with a color complementary to the second colored light). However, it should be appreciated that the first EL layer 144 A 1 can be formed with multiple layers, which emit distinct colors of lights to form the first colored light. Accordingly, in some embodiments, the first EL layer 144 A 1 may be an EL layer in which a host is doped with a red dopant and a green dopant, and the second EL layer 144 A 2 is a blue EL layer. Here, the host means a material that generates excitons from electrons and holes and that does not emits light but delivers energy to the dopant, and the dopant means a material that is added in a small amount to the host and that receives energy from the host to transforms the energy into light.

In some embodiments, the first EL layer 144 A 1 includes a stack of a yellow EL layer and a green EL layer, and the second EL layer 144 A 2 is a blue EL layer. The yellow EL layer of the first EL layer 144 A 1 may be disposed above or below the green EL layer of the first EL layer 144 A 1 . Also, in some embodiments, the first EL layer 144 A 1 includes a stack of a red EL layer 144 A 11 and a green EL layer 144 A 12 , and the second EL layer 144 A 2 is a blue EL layer. Within the first EL layer 144 A 1 , the red EL layer may be formed above or below the green EL layer. In some embodiments, the first EL layer 144 A 1 includes a stack of an EL layer doped with a red phosphor dopant and an EL layer doped with a yellow phosphor dopant. The second EL layer 144 A 2 is an EL layer doped with a blue phosphor dopant. In the first EL layer 144 A 1 , the EL layer doped with the red phosphor dopant may be formed above or below the EL layer doped with the yellow phosphor dopant.

In all of the aforementioned embodiments, light emitted from the first and second EL layers 144 A 1 and 144 A 2 are combined to form substantially white light in the area where the first and second EL layers 144 A 1 and 144 A 2 overlap each other. That is, the light emitted from the part of the OLED element relative to the first and second pixels R and G is the white light. The second EL layer emits substantially blue light at another part of the white OLED element 140 A, where only the second EL layer 144 A 2 is formed. That is, the light emitted from the part of the OLED element 140 A relative to the third pixel area B is the blue light.

To put it in other words, the first EL layer 144 A 1 is formed on the first anode 141 A 1 and the second anode 141 A 2 . The second EL layer 144 A 2 is formed on the first anode 141 A 1 , the second anode 141 A 2 , and the third anode 141 A 3 . The first EL layer 144 A 1 is formed on the second EL layer 144 A 2 . That is, the second EL layer 144 A 2 is formed on a surface of the first anode 141 A 1 , a surface of the second anode 141 A 2 , and a surface of the third anode 141 A 3 , and the first EL layer 144 A 1 is formed on over the second EL layer 144 A 2 that corresponds to the first anode 141 A 1 and the second anode 141 A 2 .

The cathode 145 A is disposed in both the first and second areas of the OLED element 140 A, and disposed on the first EL layer 144 A 1 and the second EL layer 144 A 2 . More particularly, the cathode 145 A is formed on the first EL layer 144 A 1 in the first pixel R and the second pixel G, and on the second EL layer 144 A 2 in the third pixel B.

Accordingly, the multi-layered emission layer structure 144 A emits white light in area relative to the first pixel R (e.g., red sub pixel region) and the second pixel G (e.g., green sub pixel region) where both the first and second EL layers 144 A 1 and 144 A 2 are formed. In the third pixel region B (e.g., blue sub pixel region), however, the first EL layer 144 A 1 is not disposed, and the second EL layer 144 A 2 emits blue light in the third pixel B without being combined with the light from the first EL layer 144 A 1 .

As shown in FIG. 1A , a red color filter element and green color filter element is disposed in the respective pixels to filter the white light from the multi-layered emission layer structure to generate substantially red light and green light, and to transmit the filtered light at the corresponding pixels. In the white OLED element of the present disclosure, there is no blue color filter element for filtering the white light for generating blue light. Instead, the blue light is emitted from the second EL layer 144 A 2 disposed in the third pixel B. Since the blue light transmitted at the third pixel B is not the light generated by filtering the white light, the luminance of the blue light at the third pixel B is significantly improved without having to increase the driving current density at the blue pixel of the display device. Also, the same level of blue luminance as the blue luminance from conventional white OLED element can be obtained at lower current density, and thus the power consumption of the OLED element 140 A can be decreased. Of course, the lower driving current density also leads to increase in the lifespan of the OLED element 140 A.

FIG. 1B is a pictorial representation (through a cross sectional view) depicting an OLED element 140 B that can be employed in one embodiment of the present application. Referring to FIG. 1B , the first EL layer 144 B 1 is formed on the first anode 141 B 1 and the second anode 141 B 2 . In some embodiments, the first EL layer 144 B 1 includes a stack of a red EL layer 144 B 11 and a green EL layer 144 B 12 . The second EL layer 144 B 2 , which emits blue light, is formed on the first anode 141 B 1 , the second anode 141 B 2 and the third anode 141 B 3 . That is, the first organic EL layer 144 B 1 is formed on a surface of the first anode 141 B 1 and a surface of the second anode 141 B 2 , and the second EL layer 144 B 2 is formed on the first EL layer 144 B 1 and a surface of the third anode 141 B 3 .

To simply put, the order in which the EL layers are disposed in the white OLED element 140 B is different from order of the EL layers in the white OLED element 140 A depicted in FIG. 1A . Despite being disposed in a different order, the first EL layer 144 B 1 and the second EL layer 144 B 2 of the OLED element 140 B are arranged to be overlap each other on the first anode 141 B 1 and the second anode 141 B 2 . Accordingly, the white light is emitted in the part of the multi-layered emission layer structure 140 B relative to the first pixel R and the second pixel G. Further, the EL layer emitting blue light (i.e., second EL layer 144 B 2 ) of the OLED element 140 B is extended further out to the part of the multi-layered emission layer structure 144 B relative to the third pixel B. The blue light from the second EL layer 144 B 2 is substantially unaffected by the light emitted from the other EL layer(s) (e.g., the first emission layer 144 B 1 ) of the multi-layered emission layer structure 144 B, and be transmitted at the third pixel B (e.g., blue sub pixel region). As such, the luminance and the improved lifespan of the display device can be achieved in a more efficient way.

FIG. 1C is a pictorial representation (through a cross sectional view) depicting an OLED element 140 C that can be employed in one embodiment of the display device. Referring to FIG. 1C , the OLED element 140 C includes four pixels, including a first pixel R, a second pixel G, a third pixel B and a fourth pixel W. The first pixel R can be a red sub pixel region, the second pixel G can be a green sub pixel region, the third pixel B can be a blue sub pixel region, and the fourth pixel W can be a white sub pixel region. The white pixel can be used to further reduce the power consumption and improve the luminance of the OLED element.

An anode 141 C is disposed in each of the sub pixel region. For instance, a first anode 141 C 1 , a second anode 141 C 2 , a third anode 141 C 3 and a fourth anode 141 C 4 are disposed in the first pixel R, the second pixel G, the third pixel B and the fourth pixel W, respectively. Although the first anode 141 C 1 , the second anode 141 C 2 , the third anode 141 C 3 , and the fourth anode 141 C 4 are illustrated to be in contact with adjacent anode, it should be appreciated that each anode is configured to operate separately with discrete signal supplied to each of the anodes in the pixel regions.

A cathode 145 C is formed on the anode 141 C. The cathode 145 C is formed on the entire multi-layered emission layer structure 144 C. The cathode 145 C is connected to an additional voltage wire to supply a common voltage to all sub pixel regions. Also, the cathode 145 C can be patterned so long as the cathode 145 C is configured to supply a common voltage to all four sub pixel regions.

In this example, the first EL layer 144 C 1 is formed on the first anode 141 C 1 , the second anode 141 C 2 , and the fourth anode 141 C 4 . The second EL layer 144 C 2 is formed on the first anode 141 C 1 , the second anode 141 C 2 , the third anode 141 C 3 , and the fourth anode 141 C 4 . Accordingly, the first EL layer 144 C 1 is formed in the first pixel R (red sub pixel region), the second pixel G (green sub pixel region), and the fourth pixel W (white sub pixel region), whereas the second EL layer 144 C 2 is formed in the first pixel R (red sub pixel region), the second pixel G (green sub pixel region), the third pixel B (blue sub pixel region), and the fourth pixel W (white sub pixel region). As described above, the multi-layered emission layer structure 144 C emits white light in the pixels having both the first and second EL layers. Accordingly, white light is emitted from the first pixel R, the second pixel G, and the fourth pixel W. In contrast, blue light is emitted from the third pixel B, where only the second EL layer 144 C 2 is disposed. In some embodiments, the first EL layer 144 C 1 includes a stack of a red EL layer 144 C 11 and a green EL layer 144 C 12 , and the second EL layer 144 C 2 is a blue EL layer.

As described, red and green color filter elements can be disposed in the first pixel R and the second pixel G, respectively. By filtering the white light from the multi-layered emission layer structure 144 C, red colored light is transmitted at the red sub pixel region and green light is transmitted at the green sub pixel region. The blue light emitted from the second EL layer 144 C 2 is transmitted at the blue sub pixel region. In the white sub pixel region, the white light from the multi-layered emission structure 144 C is transmitted.

In FIG. 1C , the first EL layer 144 C 1 is illustrated to be disposed on the second EL layer 144 C 2 to form the multi-layered light emitting layer structure 140 C. In some embodiments, however, the second EL layer 144 C 2 may be disposed on the first EL layer 144 C 1 . In such cases, the second EL layer 144 C 2 (e.g., the EL layer for emitting blue light) should be disposed the part of the multi-layered emission layer structure relative to all four pixels described above, and the first EL layer 144 C 1 should be disposed in the part of the multi-layered emission layer structure relative to the pixels except the blue pixel.

FIG. 2A is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 200 A according to an exemplary embodiment of the present invention. Referring to FIG. 2A , the organic light emitting display device 200 A includes a first substrate 210 A, an white OLED element 240 A, a plurality of color filter elements 290 A, and a second substrate 215 A. The white OLED element 240 A includes a plurality of anodes 241 A, a multi-layered emission layer structure 244 A and a cathode 245 A that are substantially the same as the OLED element 140 A described above.

The first substrate 210 A is a substrate configured to support various elements of the organic light emitting display device 200 A. The first substrate 210 A is a support substrate disposed at a bottom of the organic light emitting display device 200 A, and may be also referred to as a substrate, a support member, a support substrate, a lower substrate, a thin film transistor (TFT) substrate, a lower support member, etc. The support member may be formed of an insulating material, e.g., glass or plastic, but is not limited thereto and may be formed of any of various other materials.

A material of the first substrate 210 A may depend on a light-emitting manner of the organic light emitting display device 200 A. For example, when the organic light emitting display device 200 A is a top emission type organic light emitting display device, the first substrate 210 A may be formed of an insulating material but does not always need to be formed of a transparent material. When the organic light emitting display device 200 A is a bottom emission type organic light emitting display device, the first substrate 210 A may be formed of a transparent insulating material.

When the organic light emitting display device 200 A is a flexible organic light emitting display device, the first substrate 210 A may be formed of a flexible insulating material. Here, flexible insulating materials available may include polyimide (PI), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), styrene acrylonitrile (SAN) polymer, silicon-acryl resin, etc. When the organic light emitting display device 200 A is a transparent organic light emitting display device, the first substrate 210 A may be formed of a transparent insulating material.

The organic light emitting display device 200 A may include a plurality of unit pixels. When the first substrate 210 A includes a plurality of unit pixels, the plurality of unit pixels may be arranged in a matrix. Each of the plurality of unit pixels may include a plurality of sub pixel regions. The plurality of sub pixel regions may include a first sub pixel region R, a second sub pixel region G, and a third sub pixel region B. Here, the first sub pixel region R, the second sub pixel region G, and the third sub pixel region B are sub pixel regions that emit different colors. The first sub pixel region R may be a red sub pixel region, the second sub pixel region G may be a green sub pixel region, and the third sub pixel region B may be a blue sub pixel region. In the present disclosure, the red sub pixel region, the green sub pixel region, and the blue sub pixel region are illustrated as the first sub pixel region R, the second sub pixel region G, and the third sub pixel region B, respectively. In the present disclosure, the sub pixel region may also be referred to as a pixel, and the sub pixel region may also be referred to as a sub pixel.

As shown in FIG. 2A , the organic light emitting display device 200 A includes a first area X and a second area Y. The second area Y includes the third sub pixel region B, which is a blue sub pixel region. The first area X includes the first sub pixel region R and the second sub pixel region G, which are remaining sub pixel regions excluding the blue sub pixel region.

The plurality of anodes 241 A includes a first anode 241 A 1 , a second anode 241 A 2 , and a third anode 241 A 3 . The first anode 241 A 1 is disposed on a region corresponding to the first sub pixel region R, the second anode 241 A 2 is disposed on a region corresponding to the second sub pixel region G, and the third anode 241 A 3 is disposed on a region corresponding to the third sub pixel region B. Although the first, second and third anodes are illustrated as being in contact with one another, each of the anode is individually addressable such that signals can be provided on individual basis to drive the first, second and third anodes 214 A 1 , 214 A 2 and 242 A 3 in the sub pixel regions.

The multi-layered emission layer structure 244 A that includes the first EL layer 244 A 1 and the second EL layer 244 A 2 are formed on the anode 241 A. In the multi-layered emission layer structure 244 A, the first EL layer 244 A 1 is formed in the first area X of the first substrate 210 A and the second EL layer 244 A 2 is formed in the first area X and the second area Y of the first substrate 210 A. Here, the first area X includes the first sub pixel region R and the second sub pixel region G, and the second area Y includes the third sub pixel region B. Thus, in the multi-layered emission layer structure 244 A, the second EL layer 244 A 2 is formed on the first anode 241 A 1 corresponding to the first sub pixel region R, the second anode 241 A 2 corresponding to the second sub pixel region G, and the third anode 241 A 3 corresponding to the third sub pixel region B, and the first EL layer 244 A 1 is formed on the first anode 241 A 1 corresponding to the first sub pixel region R and the second anode 241 A 2 corresponding to the second sub pixel region G. The first EL layer 244 A 1 is formed on the second EL layer 244 A 2 . That is, the second EL layer 244 A 2 is formed on a surface of the first anode 241 A 1 , a surface of the second anode 241 A 2 , and a surface of the third anode 241 A 3 , and the first EL layer 244 A 1 is formed on a surface of the second EL layer 244 A 2 corresponding to the first anode 241 A 1 and the second anode 241 A 2 .

Light emitted from the first EL layer 244 A 1 and light emitted from the second EL layer 244 A 2 are different, and are combined to form white light. Specifically, the second EL layer structure 244 A 2 may be a blue EL layer that emits blue light, and the first EL layer structure 244 A 1 may be an EL layer that emits light of another colored light that, in combination with the blue light, form the white light.

In some embodiments, the first EL layer 244 A 1 may be an EL layer in which a host is doped with a red dopant and a green dopant, and the second EL layer 244 A 2 may be a blue EL layer. Lights emitted from the first and second EL layers 244 A 1 and 244 A 2 are mixed to transmit white colored light in the area where the first and second EL layers 244 A 1 and 244 A 2 overlap one another. The second EL layer emits blue colored light at another area where only the second EL layer 144 A 2 is formed.

In some embodiments, the first EL layer 244 A 1 includes a stack of a yellow EL layer and a green EL layer, and the second EL layer 244 A 2 is a blue EL layer. The yellow EL layer of the first EL layer 244 A 1 may be disposed above or below the green EL layer of the first EL layer 244 A 1 . Also, in some embodiments, the first EL layer 244 A 1 includes a stack of a red EL layer and a green EL layer, and the second EL layer 244 A 2 is a blue EL layer. Within the first EL layer 244 A 1 , the red EL layer may be formed above or below the green EL layer. In some embodiments, the first EL layer 244 A 1 includes a stack of an EL layer doped with a red phosphor dopant and an EL layer doped with a yellow phosphor dopant. The second EL layer 244 A 2 is an EL layer doped with a blue phosphor dopant. In the first EL layer 244 A 1 , the EL layer doped with the red phosphor dopant may be formed above or below the EL layer doped with the yellow phosphor dopant.

In all of the aforementioned embodiments, light emitted from the first and second EL layers 244 A 1 and 244 A 2 are combined to form the white light in the area where the first and second EL layers 244 A 1 , 244 A 2 overlap each other. The second EL layer emits blue colored light at another area where only the second EL layer 244 A 2 is formed.

The cathode 245 A is formed on the first EL layer 244 A 1 in the first area X, and is formed on the second EL layer 244 A 2 in the second area Y. That is, the cathode 245 A is formed on the first EL layer 244 A 1 in the first sub pixel region R and the second sub pixel region G, and is formed on the second EL layer 244 A 2 in the third sub pixel region B.

The cathode 245 A is configured to supply electrons and is thus formed of a material having high electrical conductivity and a low work function, i.e., a material of a cathode. Specifically, a material of the cathode 245 A may vary depending on the light-emitting mode of the organic light emitting display device 200 A. When the organic light emitting display device 200 A is a top emission type organic light emitting display device as illustrated in FIG. 2A , the cathode 245 A may be formed of a material having a low work function to discharge light emitted from the multi-layered emission layer structure 244 A to the top of the organic light emitting display device 200 A.

The second substrate 215 A is a substrate configured to support and to protect various elements of the organic light emitting display device 200 A, and is disposed opposite the first substrate 210 A. The second substrate 215 A is a support substrate disposed on the top of the organic light emitting display device 200 A and may be referred to as an upper substrate, a protective substrate, a color filter substrate, a cover substrate, an upper support member, etc.

The second substrate 215 A may be formed of an insulating material such as glass or plastic, but is not limited thereto and may be formed of any of various other materials. When the organic light emitting display device 200 A is a top emission type organic light emitting display device as illustrated in FIG. 2A , the second substrate 215 A may be formed of a transparent insulating material. In some embodiments, the second substrate 215 A may be formed of a material that is substantially the same as the material of the first substrate 210 A.

Although note shown in FIG. 2A , a black matrix may be formed on the second substrate 215 A. The black matrix may be formed at a boundary between sub pixel regions. The black matrix may be formed of chromium (Cr) or another non-transparent metal film, or may be formed of resin. The black matrix may separate the sub pixel regions and the color filter 290 A formed on the sub pixel regions.

A plurality of color filter elements 290 A is arranged relative to the first area X. More specifically, the red color filter element 291 A formed in the red sub pixel region R within the first area X, and a green color filter element 292 A formed in the green sub pixel region G within the first area X. These color filter elements are positioned such that the white colored light generated from the multi-layered emission layer structure 244 A is passed through and transformed into red colored light at the red sub pixel area R and green colored lights at the green sub pixel area G.

Color filter element needs not be arranged relative to the second area Y. Since the part of the multi-layered emission layer structure 244 A arranged at the second area Y (i.e., the third sub pixel region B) is the second EL layer 244 A 2 (i.e., a blue EL layer), blue colored light can be transmitted at the third sub pixel region B (i.e., blue sub pixel region B) without any color filter element. To planarize the sub pixel areas, however, a transparent member (e.g., transparent resin layer) having the same thickness as the plurality of color filter elements 290 A may be disposed at the second area Y. In this configuration, improvement in the efficiency, power consumption and the lifespan of the organic light emitting element 240 A can be obtained.

The organic light emitting display device 200 A in FIG. 2A has been illustrated as a top emission type organic light emitting display device and the plurality of color filter elements 290 A has been shown as being formed on the cathode 245 A.

Although for convenience of explanation, FIG. 2A illustrates that the color filter elements 290 A and the cathode 245 A contact each other, the cathode 245 A and the color filter elements 290 A may be disposed spaced from each other and an encapsulating unit may be disposed in a space between the cathode 245 A and the color filter elements 290 A. The encapsulating unit will be described in detail below.

FIG. 2B is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 200 B according to an exemplary embodiment of the present invention. Referring to FIG. 2B , except for the multi-layered emission layer structure 240 A, all of the components are same as the organic light emitting display device 200 A. In the organic light emitting display device 200 A, the second EL layer 244 B 2 is formed on the first EL layer 244 B 1 . In other words, the first EL layer 244 B 1 is formed on a surface of the first anode 241 B 1 and a surface of the second anode 241 B 2 , and the second EL layer 244 B 2 is formed on a surface of the first EL layer 244 B 1 and a surface of the third anode 241 B 3 .

FIG. 2C is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 200 C according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 2C are substantially the same as those in FIG. 2A with like numerals assigned thereto (except for alphabets).

In this example, the plurality of color filter elements 290 C further includes a third color filter element 293 C. The third color filter element 293 C is disposed in the second area Y. Specifically, the third color filter element 293 C is a blue color filter element formed in a third sub pixel region B, which is a blue sub pixel region.

Since only the second EL layer 244 C 2 is formed in the second area Y, which includes the third sub pixel area B, blue light emitted from second EL layer 244 C is transmitted at the third sub pixel region B. Thus, there is no need for the blue color filter element 293 C to represent blue color in the third sub pixel region B. When white light emitted from a white EL layer passes through the blue color filter element, only the light in certain wavelength range is passed through, thereby substantially decreasing the luminance. When the blue light emitted from the second EL layer 244 C 2 passes through the blue color filter element 293 C, however, large part of the blue light can be passed through the color filter element 293 C without being absorbed by the color filter element 293 C. As such, even if the third color filter 293 C is disposed in the third sub pixel region B, the luminance efficiency is hardly reduced. Furthermore, blue color coordinates are easier to match and a contrast ratio (CR) may be improved in the blue sub pixel region B by filtering the blue light through the blue color filter.

FIG. 2D is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 200 D according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 2D are substantially the same as those in FIG. 2A with like numerals assigned thereto (except for alphabets). Referring to FIG. 2D , a charge generation layer (CGL) 246 D is formed between a first EL layer 244 D 1 and a second EL layer 244 D 2 . The charge generation layer 246 D is a layer configured to generate electric charges (i.e., electrons and holes) therein. The charge generation layer 246 D is present in a structure that connects the first EL layer 244 D 1 and the second EL layer 244 D 2 in series, and increases the efficiency of current generated between the first EL layer 244 D 1 and the second EL layer 244 D 2 .

As shown in FIG. 2D , the charge generation layer 246 D is formed between the first EL layer 244 D 1 and the second EL layer 244 D 2 in a first area X. Since the charge generation layer 246 D is formed between the first EL layer 244 D 1 and the second EL layer 244 D 2 to increase the efficiency of current generated between the first EL layer 244 D 1 and the second EL layer 244 D 2 , the charge generation layer 246 D is formed in the first area X including the first sub pixel region R and the second sub pixel region G where both the first EL layer 244 D 1 and the second EL layer 244 D 2 are formed. However, the present invention is not limited thereto, and the charge generation layer 246 D may be formed in both the first area X and a second area Y, especially when the first and/or the second EL layer itself is formed of multiple EL layers.

FIG. 2E is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 200 E according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 2E are substantially the same as those in FIG. 2A with like numerals assigned thereto (except for alphabets).

Referring to FIG. 2E , the organic light emitting display device 200 E may include pixel regions, and each of the pixel regions may include a plurality of sub pixel regions. For example, each of the plurality of pixel regions may include a first sub pixel region R, a second sub pixel region G, a third sub pixel region B, and a fourth sub pixel region W. Here, it is defined that the first sub pixel region R is a red sub pixel region, the second sub pixel region G is a green sub pixel region, the third sub pixel region B is a blue sub pixel region, and the fourth sub pixel region W is a white sub pixel region configured to reduce power consumption and improves brightness. Also, it is defined that a second area Y of the first substrate 210 E is the third sub pixel region B which is the blue sub pixel region, and a first area X of the first substrate 210 E includes the first sub pixel region R, the second sub pixel region G, and the fourth sub pixel region W which are the other sub pixel regions except for the blue sub pixel region.

An anode 241 E includes a first anode 241 E 1 , a second anode 241 E 2 , a third anode 241 E 3 , and a fourth anode 241 E 4 . It is defined that the first anode 241 E 1 is formed on a region corresponding to the first sub pixel region R, the second anode 241 E 2 is formed on a region corresponding to the second sub pixel region G, the third anode 241 E 3 is formed on a region corresponding to the third sub pixel region B, and the fourth anode 241 E 4 is formed on a region corresponding to the fourth sub pixel region W. Although for convenience of explanation, FIG. 2E illustrates that the first anode 241 E 1 , the second anode 241 E 2 , the third anode 241 E 3 , and the fourth anode 241 E 4 contact one another, the first anode 241 E 1 , the second anode 241 E 2 , the third anode 241 E 3 , and the fourth anode 241 E 4 may be formed to be separated from one another so that signals may be independently supplied to the sub pixel regions to independently drive these anodes in units of the sub pixel regions.

A cathode 245 E is formed on the anode 241 E. The cathode 245 E may be formed on the entire anode 241 E. That is, since the cathode 245 E is connected to an additional voltage wire to supply the same voltage to all the sub pixel regions, the cathode 245 E may not be patterned in units of the sub pixel regions and may be formed to cover the entire anode 241 E.

A first EL layer 244 E 1 is formed on the first anode 241 E 1 , the second anode 241 E 2 , and the fourth anode 241 E 4 , and a second EL layer 244 E 2 is formed on the first anode 241 E 1 , the second anode 241 E 2 , the third anode 241 E 3 , and the fourth anode 241 E 4 . That is, the first EL layer 244 E 1 is formed on the red sub pixel region, the green sub pixel region, and the white sub pixel region, whereas the second EL layer 244 E 2 is formed on the red sub pixel region, the green sub pixel region, the blue sub pixel region, and the white sub pixel region. Thus, the multi-layered emission layer structure 244 E emits white light in the red sub pixel region R, the green sub pixel region G, and the white sub pixel region W in which both the first and second EL layers 244 E 1 and 244 E 2 are formed. The multi-layered emission layer structure 244 E emits blue light in the blue sub pixel region B in which only the second EL layer 244 E 2 is disposed.

The first EL layer 244 E 1 is formed on the first anode 241 E 1 , the second anode 241 E 2 , and the fourth anode 241 E 4 . The second EL layer 244 E 2 is formed on the first anode 241 E 1 , the second anode 241 E 2 , the third anode 241 E 3 , and the fourth anode 241 E 4 . The first EL layer 244 E 1 is formed on the second EL layer 244 E 2 . That is, the second EL layer 244 E 2 is formed on a surface of the first anode 241 E 1 , a surface of the second anode 241 E 2 , a surface of the third anode 241 E 3 , and a surface of the fourth anode 241 E 4 , and the first EL layer 244 E 1 is formed on a surface of the second EL layer 244 E 2 corresponding to the first anode 241 E 1 , the second anode 241 E 2 , and the fourth anode 241 E 4 . A process of forming the first and second EL layers 244 E 1 and 244 E 2 according to a manner of stacking the first and second EL layers 244 E 1 and 244 E 2 will be described below. In some embodiments, as illustrated in FIG. 2B , the first EL layer 244 E 1 may be formed on the surface of the first anode 241 E 1 , a surface of the second anode 241 E 2 , and a surface of the fourth anode 241 E 4 , and the second EL layer 244 E 2 may be formed on a surface of the first EL layer 244 E 1 and a surface of the third anode 241 E 3 .

The cathode 245 E is formed on the first EL layer 244 E 1 and the second EL layer 244 E 2 . Specifically, the cathode 245 E is formed on the first EL layer 244 E 1 in the first sub pixel region R, the second sub pixel region G, and the fourth sub pixel region W, and on the second EL layer 244 E 2 in the third sub pixel region B.

FIG. 3A is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 A according to an exemplary embodiment of the present invention.

Referring to FIG. 3A , the organic light emitting display device 300 A includes a first substrate 310 A, a thin film transistor 320 A, an organic light emitting element 340 A, an encapsulating unit 360 A, a color filter 390 A, and a second substrate 315 A. The first substrate 310 A, the color filter 390 A, and the second substrate 315 A are substantially the same as the first substrate 210 A, the color filter 290 A, and the second substrate 215 A of FIG. 2A , and are not redundantly described here.

An active layer 321 A is formed on the first substrate 310 A. The active layer 321 A may include a channel region in which a channel is formed, and a source region and a drain region that contact a source electrode 323 A and a drain electrode 324 A, respectively. The active layer 321 A may be formed of amorphous silicon, polycrystalline silicon, or an oxide semiconductor. In the case of a thin film transistor using polycrystalline silicon as an active layer, an ion injection process is performed to adjust a resistance of the active layer and an additional mask may be used to define an ion injection region. Since the ion injection process is added, the thin film transistor using polycrystalline silicon as an active layer is disadvantageous in terms of a manufacturing process. In contrast, a thin film transistor using an oxide semiconductor as an active layer has higher mobility than a thin film transistor using amorphous silicon as an active layer, has a much lower amount of leak current than the thin film transistor using amorphous silicon as an active layer and a thin film transistor using polycrystalline silicon as an active layer, and satisfies high reliability test conditions. Also, the thin film transistor using an oxide semiconductor as an active layer has a regular distribution of threshold voltages, compared to the thin film transistor using polycrystalline silicon as an active layer.

The active layer 321 A may include an oxide semiconductor. As a material of the oxide semiconductor included in the active layer 321 A, an indium-tin-gallium-zinc oxide (InSnGaZnO)-based material which is a quaternary metal oxide; an indium-gallium-zinc oxide (InGaZnO)-based material, an indium-tin-zinc oxide (InSnZnO)-based material, an indium-aluminum-zinc oxide (InAlZnO)-based material, a tin-gallium-zinc oxide (SnGaZnO)-based material, an aluminum-gallium-zinc oxide (AlGaZnO)-based material, or a tin-aluminum-zinc oxide (SnAlZnO)-based material which is a ternary metal oxide; an indium zinc oxide (InZnO)-based material, a tin zinc oxide (SnZnO)-based material, an aluminum zinc oxide (AlZnO)-based material, a zinc magnesium oxide (ZnMgO)-based material, a tin magnesium oxide (SnMgO)-based material, an indium magnesium oxide (InMgO)-based material, or an indium gallium oxide (InGaO)-based material which is a binary metal oxides; an indium oxide (InO)-based material, a tin oxide (SnO)-based material, a zinc oxide (ZnO)-based material, etc. may be used. The composition ratio of the elements included in each of the oxide semiconductors described above is not limited and may be variously adjusted.

In some embodiments, a buffer layer may be formed on the entire first substrate 310 A. The buffer layer may prevent inflow of moisture or impurities via the first substrate 310 A, and provide a flat surface on the first substrate 310 A. However, the buffer layer is optional and may be selectively formed according to the type of the first substrate 310 A or the type of the thin film transistor 320 A used in the organic light emitting display device 300 A. For example, the buffer layer is optional when the thin film transistor 320 A uses an oxide semiconductor as the active layer 321 A but may be indispensable to improving interface characteristics of the active layer 321 A when the thin film transistor 320 A uses amorphous silicon or polycrystalline silicon as the active layer 321 A. If the buffer layer is used, the buffer layer may be formed of a silicon oxide film, a silicon nitride film, or a multi-layer film thereof.

A gate insulating film 332 A is formed on the active layer 321 A. The gate insulating film 332 A insulates the active layer 321 A and a gate electrode 322 A from each other. The gate insulating film 332 A may be formed of a silicon oxide film, a silicon nitride film, or a multi-layer film thereof, but is not limited thereto and may be formed of any of other various materials. The gate insulating film 332 A may be formed on the entire first substrate 310 A including the active layer 321 A but may be formed only on the active layer 321 A as illustrated in FIG. 3A since it is sufficient for the gate insulating film 332 A to insulate the active layer 321 A and the gate electrode 322 A from each other. When the gate insulating film 332 A is formed on the entire first substrate 310 A, the gate insulating film 332 A may be formed to have contact holes via which some regions of the active layer 321 A is exposed. Some regions of the source region and the drain region of the active layer 321 A may be exposed via the contact holes.

The gate electrode 322 A is formed on the gate insulating film 332 A. At least a portion of the gate electrode 322 A overlaps with the active layer 321 A, and particularly, the channel region of the active layer 321 A. The gate electrode 322 A may be formed of at least one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), but is not limited thereto and may be formed of any of other various materials. Also, the gate electrode 322 A may be a multilayer film including at least one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu).

An interlayer insulating film 333 A is formed on the gate electrode 322 A. The interlayer insulating film 333 A may be formed of a material used to form the gate insulating film 332 A and formed of a silicon oxide film, a silicon nitride film, or a multilayer film including these films, but is not limited thereto and may be formed of any of other various materials. The interlayer insulating film 333 A may be formed on the entire first substrate 310 A, and may have contact holes via which some regions of the active layer 321 A are exposed. Some regions of the source and drain regions of the active layer 321 A may be exposed via the contact holes.

The source electrode 323 A and the drain electrode 324 A are formed on the interlayer insulating film 333 A. The source electrode 323 A and the drain electrode 324 A may be electrically connected to the source and drain regions of the active layer 321 A via the contact holes formed in the interlayer insulating film 333 A and/or the gate insulating film 332 A, respectively. The source electrode 323 A and the drain electrode 324 A may be each formed of at least one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), but is not limited thereto and may be formed of any of other various materials. Also, the source electrode 323 A and the drain electrode 324 A may be each a multilayer film including at least one selected from the group consisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu).

A passivation film 334 A is formed on the source electrode 323 A and the drain electrode 324 A. The passivation film 334 A may have a contact hole via which the source electrode 323 A or the drain electrode 324 A is exposed. The passivation film 334 A is a protective layer, may be formed of the material used to form the interlayer insulating film 333 A and/or the gate insulating film 332 A, and may be formed to be a single or multiple layer including one of a silicon oxide film, a silicon nitride film, etc., but is not limited thereto and may be formed of any of other various materials. Although FIG. 3A illustrates that the organic light emitting display device 300 A includes the passivation film 334 A, the passivation film 334 A is not an indispensable element and is thus optional.

An over-coating layer 335 A is formed on the source electrode 323 A and the drain electrode 324 A. The over-coating layer 335 A may be also referred to as a planarizing film. When the passivation film 334 A is formed, the over-coating layer 335 A may be formed on the passivation film 334 A. The over-coating layer 335 A provides a flat surface on the first substrate 310 A. Also, the over-coating layer 335 A may have a contact hole via which the source electrode 323 A or the drain electrode 324 A is exposed. The over-coating layer 335 A may be formed of at least one material among polyacrylates resin, epoxy resin, phenolic resin, polyamides resin, polyimides resin, unsaturated polyesters resin, poly-phenylenethers resin, poly-phenylenesulfides resin, and benzocyclobutene, but is not limited thereto and may be formed of any of various other materials.

The thin film transistor 320 A includes the active layer 321 A, the gate electrode 322 A, the source electrode 323 A, and the drain electrode 324 A formed as described above. The thin film transistor 320 A may be formed on the first substrate 310 A in units of pixel regions or sub pixel regions, and enable the pixel regions or the sub pixel regions to be independently driven. The structure of the thin film transistor 320 A is, however, not limited to the above description and may be modified to any of well-known various thin film transistor structures that those of ordinary skill would easily achieved.

The thin film transistor 320 A may be formed on the first substrate 310 A to cause a multi-layered emission layer structure 344 A to emit light. In general, a switching thin film transistor and a driving thin film transistor are used to cause the multi-layered emission layer structure 344 A to emit light based on image information of a data signal input according to a scan signal.

When the scan signal is supplied to the switching thin film transistor via a gate wire, the switching thin film transistor transmits the data signal received via a data wire to a gate electrode of the driving thin film transistor. The driving thin film transistor delivers current supplied via a power supply wire to an anode, based on the data signal received from the switching thin film transistor, and light emission of an EL layer of a corresponding pixel or sub pixel is controlled using the current supplied to the anode.

The organic light emitting display device 300 A may further include a thin film transistor for a compensation circuit designed to prevent abnormal driving of the organic light emitting display device 300 A. In the present disclosure, only the driving thin film transistor among various thin film transistors that may be included in the organic light emitting display device 300 A is illustrated for convenience of explanation.

Thin film transistors may be classified into an inverted-staggered type thin film transistor and a coplanar type thin film transistor according to the location of elements thereof. The inverted-staggered type thin film transistor means a thin film transistor in which a gate electrode is disposed opposite a source electrode and a drain electrode with respect to an active layer. The coplanar type thin film transistor means a thin film transistor in which a gate electrode is disposed at the same side as a source electrode and a drain electrode with respect to an active layer. In the present disclosure, the coplanar type thin film transistor is illustrated for convenience of explanation, but the present invention is not limited thereto and the inverted-staggered type thin film transistor may be employed.

The organic light emitting element 340 A including the anodes 341 A, the multi-layered emission layer structure 344 A, and a cathode 345 A is formed on the first substrate 310 A. The organic light emitting element 340 A is driven to form an image according to the principle that holes supplied from the anodes 341 A and electrons supplied from the cathode 345 A are recombined in the EL layer(s) to emit light.

The organic light emitting display device 300 A may be an independent driving display device, and is each of the sub pixel regions may be driven separately. Thus, the thin film transistor 320 A and the organic light emitting element 340 A described above may be disposed in the sub pixel regions to cause the thin film transistor 320 A disposed in each of the sub pixel regions to independently drive the organic light emitting element 340 A.

The anodes 341 A are formed on the over-coating layer 335 A. The anodes 341 A may be connected to the source electrode 323 A of the thin film transistor 320 A via the contact hole formed in the over-coating layer 335 A. In the present disclosure, it has been described that the anodes 341 A are connected to the source electrode 323 A on an assumption that the thin film transistor 320 A is an N-type thin film transistor. However, when the thin film transistor 320 A is a P-type thin film transistor, the anodes 341 A may be connected to the drain electrode 324 A. The anodes 341 A may directly contact the multi-layered emission layer structure 344 A or may contact the multi-layered emission layer structure 344 A via a conductive material to be electrically connected to the EL layer 344 A.

Since the anodes 341 A should supply holes, the anodes 341 A are formed of a material having a high work function. The anodes 341 A may each include a transparent conductive layer 343 A having a high work function. The transparent conductive layer 343 A may be formed of a transparent conductive oxide (TCO), such as indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), zinc oxide (Zinc Oxide), or tin oxide (Tin Oxide).

When the organic light emitting display device 300 A is a top emission type organic light emitting display device as illustrated in FIG. 3A , the anodes 341 A each include a reflective layer 342 A formed below the transparent conductive layer 343 A. The multi-layered emission layer structure 344 A emits light in a forward direction. However, when the organic light emitting display device 300 A is a top emission type organic light emitting display device, light emitted from the multi-layered emission layer structure 344 A should be discharged to the top of the organic light emitting display device 300 A. However, as described above, when the anodes 341 A each include only the transparent conductive layer 343 A, light emitted from the multi-layered emission layer structure 344 A toward the anodes 341 A may be reflected upward by other elements disposed below the anodes 341 A but may also be discharged below the first substrate 310 A and thus be lost. In this case, the luminance efficiency of the organic light emitting display device 300 A is low. Thus, each of the anodes 341 A may further include an additional low-resistance reflective layer 342 A to discharge light, which is emitted from the multi-layered emission layer structure 344 A toward the anodes 341 A, to the top of the organic light emitting display device 300 A. The reflective layer 342 A may be formed of a conductive layer having high reflectivity, e.g., silver (Ag), nickel (Ni), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), or molybdenum/aluminum neodymium (Mo/AlNd). Although it has been defined in the present disclosure that the anodes 341 A each include the transparent conductive layer 343 A and the reflective layer 342 A, it may be defined that the anodes 341 A each include only the transparent conductive layer 343 A and the reflective layer 342 A is separately disposed. Also, it has been described in the present disclosure that the anodes 341 A each include a transparent conductive material having a high work function and a reflective metal layer, but the anodes 341 A may be formed of a conductive material having a high work function and high reflectivity.

Among the transparent conductive layer 343 A and the reflective layer 342 A that constitute each of the anodes 341 A, the transparent conductive layer 343 A may be electrically connected to the source electrode 323 A. Referring to FIG. 3A , the reflective layer 342 A may be formed on the over-coating layer 335 A and a contact hole may be formed in the over-coating layer 335 A so as to electrically connect the transparent conductive layer 343 A and the source electrode 323 A. Although for convenience of explanation, FIG. 3A illustrates that the transparent conductive layer 343 A is electrically connected to the source electrode 323 A, the reflective layer 342 A may be electrically connected to the source electrode 323 A via the contact hole formed in the over-coating layer 335 A and the transparent conductive layer 343 A may be formed on the reflective layer 342 A to be electrically connected to the source electrode 323 A via the reflective layer 342 A.

The anodes 341 A are formed to be divided in units of the sub pixel regions. In other words, the anode 341 A formed in a red sub pixel region, the anode 341 A formed in a green sub pixel region, and the anode 341 A formed in a blue sub pixel region may individually and electrically drive the corresponding sub pixel regions through the thin film transistor.

A bank layer 336 A is formed on the over-coating layer 335 A and the anode 341 A. The bank layer 336 A divides adjacent sub pixel regions and may be disposed between adjacent sub pixel regions. Also, the bank layer 336 A may be formed such that a portion of the anode 341 A is open. The bank layer 336 A may be formed of an organic insulating material, e.g., any one of polyimide, photo acryl, and benzocyclobutene (BCB). The bank layer 336 A may be formed in a taper. When the bank layer 336 A has a taper form, the bank layer 336 A may be formed using a positive type photoresist. The bank layer 336 A may be formed to a thickness appropriate to divide adjacent sub pixel regions.

The multi-layered emission layer structure 344 A including the first EL layer 344 A 1 and the second EL layer 344 A 2 is formed on the anode 341 A. In the EL layer 344 A, the first EL layer 344 A 1 is formed in the first sub pixel region R and the second sub pixel region G of the first substrate 310 A, and the second EL layer 344 A 2 is formed in the first sub pixel region R, the second sub pixel region G and the third sub pixel region B of the first substrate 310 A. Thus, in the EL layer 344 A, the second EL layer 344 A 2 is formed on the first anode 341 A 1 corresponding to the first sub pixel region R, the second anode 341 A 2 corresponding to the second sub pixel region G, and the third anode 341 A 3 corresponding to the third sub pixel region B, and the first EL layer 344 A 1 is formed on the first anode 341 A 1 corresponding to the first sub pixel region R and the second anode 341 A 2 corresponding to the second sub pixel region G. The first EL layer 344 A 1 is formed on the second EL layer 344 A 2 . That is, the second EL layer 344 A 2 is formed on a surface of the first anode 341 A 1 , a surface of the second anode 341 A 2 , and a surface of the third anode 341 A 3 , and the first EL layer 344 A 1 is formed on a surface of the second EL layer 344 A 2 corresponding to the first and second anodes 341 A 1 and 341 A 2 .

Lights emitted from the respective first and second EL layers 344 A 1 and 344 A 2 are different and are mixed to form white light. Specifically, the second EL layer 344 A 2 may be a blue emission layer that emits blue light, and the first EL layer 344 A 1 may be a multi-layered emission layer structure 344 A that emits various other color lights that are mixed with the blue light to form white light. The first EL layer 344 A 1 and the second EL layer 344 A 2 are substantially the same as the first multi-layered emission layer structure 244 A 1 and the second multi-layered emission layer structure 244 A 2 described above with reference to FIG. 2A , and are thus not redundantly described here.

The second EL layer 344 A 2 may be formed to a thickness appropriate to form a micro-cavity in the third sub pixel region B. The micro-cavity means that light having a particular wavelength is amplified by constructive interference when lights are repeatedly reflected between two layers spaced by an optical length from each other. The micro-cavity may also be referred to as a fine cavity effect or a fine resonance effect. To form the micro-cavity, a resonance distance should be set in units of wavelengths of lights emitted from the respective sub pixel regions. The resonance distance may be set to a multiple of a half-wavelength of light emitted. As described above, when a resonance distance is set with respect to light with a particular wavelength, the amplitudes of lights having the particular wavelength among lights emitted increase to be discharged to the outside due to constructive interference as these lights are repeatedly reflected between the anode 341 A and the cathode 345 A, thereby improving luminance.

In contrast, as the other lights not having the particular wavelength among the emitted lights are repeatedly reflected between the anode 341 A and the cathode 345 A, the amplitudes of the lights not having the particular wavelength decrease due to destructive interference. Thus, in order to form the micro-cavity in the third sub pixel region B, the distance between the anode 341 A and the cathode 345 A in the third sub pixel region B should be adjusted. Specifically, the distance between the anode 341 A and the cathode 345 A in the third sub pixel region B should be equal to a multiple of a half-wavelength of blue visible light. In the organic light emitting display device 300 A according to another exemplary embodiment of the present invention, the thickness of the second EL layer 344 A 2 disposed between the anode 341 A and the cathode 345 A may be set to a multiple of the half-wavelength of blue visible light, thereby forming the micro-cavity in the third sub pixel region B.

The cathode 345 A is formed on the EL layer 344 A. Since the cathode 345 A should supply electrons, the cathode 345 A is formed of a material having high electrical conductivity and a low work function, i.e., a material of a cathode. Specifically, a material of the cathode 345 A may depend on the light-emitting manner of the organic light emitting display device 300 A. When the organic light emitting display device 300 A is a top emission type organic light emitting display device as illustrated in FIG. 3A , the cathode 345 A may be formed of a very thin metal material having a low work function. For example, when the cathode 345 A is formed of a metal material having a low work function, the cathode 345 A may be obtained by forming a metal material such as silver (Ag), titanium (Ti), aluminum (Al), molybdenum (Mo), or an alloy of silver (Ag) and magnesium (Mg) to a thickness of several hundreds of Å or less, e.g., 200 Å or less. In this case, the cathode 345 A becomes a substantial semi-transmissive layer to be substantially used as a transparent cathode.

Even if a material of the cathode 345 A is a non-transparent material having high reflectivity, when the cathode 345 A becomes thinner to a predetermined thickness or less, e.g., 200 Å of less, the transparency of the cathode 345 A gradually increases. The cathode 345 A having such a thickness may be referred to as a substantial transparent cathode. Also, a carbon nano tube and graphene to which much attention has been paid as new materials may also be used as a material of the cathode 345 A.

The encapsulating unit 360 A formed as a sealing member for covering the organic light emitting element 340 A is formed on the organic light emitting element 340 A including the cathode 345 A. The encapsulating unit 360 A may protect internal elements of the organic light emitting display device 300 A, such as the thin film transistor 320 A and the organic light emitting element 340 A, against external moisture, air, shocks, etc.

The structure of the encapsulating unit 360 A may depend on a method of sealing the internal elements of the organic light emitting display device 300 A such as the thin film transistor 320 A and the organic light emitting element 340 A. Examples of the method of sealing the organic light emitting display device 300 A include metal can encapsulation, glass can encapsulation, thin film encapsulation (TFE), face sealing, etc.

The second substrate 315 A is a substrate configured to support and to protect various elements of the organic light emitting display device 300 A, and is disposed opposite the first substrate 310 A. The color filter 390 A is formed on the second substrate 315 A. The color filter 390 A includes a first color filter 391 A formed in the first sub pixel region R, and a second color filter 392 A formed in the second sub pixel region G. The first color filter 391 A is a red color filter formed in the first sub pixel region R that is a red sub pixel region, and the second color filter 392 A is a green color filter formed in the second sub pixel region G that is a green sub pixel region. Thus, white light passing through the first sub pixel region R and the second sub pixel region G among white lights emitted from the multi-layered emission layer structure 344 A that emits white light passes through the color filter 390 A. In detail, white light passing through the first color filter 391 A is transformed into red light, and white light passing through the second color filter 392 A is transformed into green light.

The color filter 390 A is not formed on the second substrate 315 A corresponding to the third sub pixel region B. However, a portion of the multi-layered emission layer structure 344 A formed in the third sub pixel region B is the second EL layer 344 A 2 corresponding to a blue emission layer. Thus, even if the color filter 390 A is not formed in the third sub pixel region B, blue light may be emitted from the third sub pixel region B. In some embodiments, a transparent resin layer having the same thickness as the color filter 390 A may be formed on the second substrate 315 A corresponding to the third sub pixel region B.

FIG. 3D is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 B according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 3B are substantially the same as those in FIG. 3A when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here. FIG. 3B illustrates that the organic light emitting display device 300 B is a bottom emission type organic light emitting display device.

When the organic light emitting display device 300 B is a bottom emission type organic light emitting display device, an anode 341 B may be formed of transparent conductive material having a high work function, e.g., indium tin oxide (ITO), indium zinc oxide (IZO), indium-tin-zinc oxide (ITZO), zinc oxide, or tin oxide.

When the organic light emitting display device 300 B is a bottom emission type organic light emitting display device, a cathode 345 B may be formed of a conductive material having a low work function and high reflectivity, e.g., a metal material such as silver (Ag), titanium (Ti), aluminum (Al), molybdenum (Mo), or an alloy of silver (Ag) and magnesium (Mg).

When the organic light emitting display device 300 B is a bottom emission type organic light emitting display device, a color filter 390 B may be formed between a first substrate 310 B and an organic light emitting element 340 B. Although FIG. 3B illustrates that the color filter 390 B is formed on the passivation film 334 B, the color filter 390 B may be formed in an arbitrary space between the first substrate 310 B and the organic light emitting element 340 B. For example, the color filter 390 B may be formed on the interlayer insulating film 333 B or the first substrate 310 B.

FIG. 3C is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 C according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 3C are substantially the same as those in FIG. 3A when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here.

A color filter 390 C formed on a second substrate 315 C includes a third color filter 393 C. Specifically, the third color filter 393 C serving as a blue color filter is formed in a third sub pixel region B that is a blue sub pixel region.

As described above, since a second EL layer 344 C 2 is formed in the third sub pixel region B, which is a blue sub pixel region, blue light is emitted from the EL layer 344 C in the third sub pixel region B that is a blue sub pixel region. Thus, blue light may be transmitted in the third sub pixel region B even if an additional color filter is disposed. In the third sub pixel region B, which is a blue sub pixel region, the EL layer 344 C emits blue light. Luminance efficiency is hardly degraded when the blue light passes through the third color filter 393 C which is a blue color filter. Thus, even if the third color filter 393 C is disposed in the third sub pixel region B, not only the luminance efficiency is hardly degraded but also a contrast ratio may be improved in the third sub pixel region B which is a blue sub pixel region.

FIG. 3D is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 D according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 3D are substantially the same as those in FIG. 3B when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here.

A color filter 390 D formed between a first substrate 310 D and an organic light emitting element 340 D includes a third color filter 393 D. In detail, the third color filter 393 D serving as a blue color filter is formed in a third sub pixel region B which is a blue sub pixel region. Thus, white light passing through the third sub pixel region B among white lights emitted from an EL layer 344 D that emits white light passes through the third color filter 393 D and is then transformed into blue light.

As described above, since only a second EL layer 344 D 2 is formed in the third sub pixel region B which is a blue sub pixel region, blue light is emitted from the EL layer 344 D in the third sub pixel region B which is a blue sub pixel region. Thus, blue color may be represented in the third sub pixel region B even when an additional color filter is installed. The EL layer 344 D emits blue light in the third sub pixel region B that is a blue sub pixel region. Since luminance efficiency is hardly degraded when the blue light passes through the third color filter 393 D which is a blue filter, not only the luminance efficiency is hardly degraded even when the third color filter 393 D is disposed in the third sub pixel region B but also a contrast ratio may be improved in the second area Y including the third sub pixel region B.

FIG. 3E is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 E according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 3E are substantially the same as those in FIG. 3A when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here.

An EL layer 344 E including a first EL layer 344 E 1 and a second EL layer 344 E 2 is formed on an anode 341 E. In the EL layer 344 E, the first EL layer 344 E 1 is formed in the first sub pixel region R and the second sub pixel region G of a first substrate 310 E and the second EL layer 344 E 2 is formed in t the first sub pixel region R, the second sub pixel region G and the third sub pixel region B of the first substrate 310 E. Thus, in the EL layer 344 E, the first EL layer 344 E 1 is formed on a first anode 341 E 1 corresponding to the first sub pixel region R and the second anode 341 E 2 corresponding to the second sub pixel region G, and the second EL layer 344 E 2 is formed on the first EL layer 344 E 1 corresponding to the first sub pixel region R and the second sub pixel region G and a third anode 341 E 3 corresponding to the third sub pixel region B. A process of forming the first and second EL layers 344 E 1 and 344 E 2 according to a manner of stacking the first and second EL layers 344 E 1 and 344 E 2 will be described below.

Lights emitted from the respective first and second EL layers 344 E 1 and 344 E 2 are different and are mixed to form white light. Specifically, the second EL layer 344 E 2 may be a blue emission layer that emits blue light, and the first EL layer 344 E 1 may be EL layer that emits other various color lights that are mixed with the blue light to form white light. The first and second EL layers 344 E 1 and 344 E 2 are substantially the same as the first and second EL layers 244 A 1 and 244 A 2 of FIG. 2A and are thus not redundantly described here.

FIG. 3F is a pictorial representation (through a cross sectional view) depicting an organic light emitting display device 300 F according to an exemplary embodiment of the present invention. Elements illustrated in FIG. 3F are substantially the same as those in FIG. 3A when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here.

The organic light emitting display device 300 F may include pixel regions. Each of the pixel regions is a region for representing one color and may include a plurality of sub pixel regions. For example, each of the plurality of pixel regions may include a first sub pixel region R, a second sub pixel region G, a third sub pixel region B, and a fourth sub pixel region W. Here, it is defined that the first sub pixel region R is a red sub pixel region, the second sub pixel region G is a green sub pixel region, the third sub pixel region B is a blue sub pixel region, and the fourth sub pixel region W is a white sub pixel region configured to reduce power consumption and improve brightness.

An anode 341 F is formed in the fourth sub pixel region W of the first substrate 310 F. An EL layer 344 F including a first EL layer 344 F 1 and a second EL layer 344 F 2 is formed on the anode 341 F. A cathode 345 F is formed on the EL layer 344 F. Since both the first EL layer 344 F 1 and the second EL layer 344 F 2 are formed in the fourth sub pixel region W, lights emitted from the respective first and second EL layers 344 F 1 and 344 F 2 are mixed to emit white light in the fourth sub pixel region W.

Since the fourth sub pixel region W is a white sub pixel region, a color filter 390 F is not formed on a second substrate 315 F corresponding to the fourth sub pixel region W. However, the present invention is not limited thereto and a transparent resin layer having the same thickness as the color filter 390 F may be disposed on a location on the second substrate 315 F corresponding to the third sub pixel region B.

FIGS. 4A and 4B are conceptual diagrams illustrating organic light emitting display devices 400 A and 400 B according to various exemplary embodiments of the present invention.

First, referring to FIG. 4A , the organic light emitting display device 400 A includes a first substrate 410 A and an organic light emitting element 440 A. The first substrate 410 A is substantially the same as the first substrate 310 A of FIG. 3A and is not redundantly described here.

The first substrate 410 A includes a first sub pixel region R which is red sub pixel region, a second sub pixel region G which is a green sub pixel region, and a third sub pixel region B which is a blue sub pixel region. The organic light emitting element 440 A includes a first organic light emitting element 440 A 1 and a second organic light emitting element 440 A 2 . The first organic light emitting element 440 A 1 is formed in the first sub pixel region R, which is a red sub pixel region and the second sub pixel region G, which is a green sub pixel region, and emits white light. The second organic light emitting element 440 A 2 is formed in the third sub pixel region B, which is a blue sub pixel region, and emits blue light.

Next, referring to FIG. 4B , the organic light emitting display device 400 B includes a first substrate 410 B and an organic light emitting element 440 B. The first substrate 410 B is substantially the same as the first substrate 310 A of FIG. 3A and is thus not redundantly described here.

The first substrate 410 B includes a first sub pixel region R which is red sub pixel region, a second sub pixel region G which is a green sub pixel region, a third sub pixel region B which is a blue sub pixel region, and a fourth sub pixel region W which is a white sub pixel region. The organic light emitting element 440 B includes a first organic light emitting element 440 A 1 and a second organic light emitting element 440 A 2 . The first organic light emitting element 440 A 1 is formed in the first sub pixel region R, which is red sub pixel region, the second sub pixel region G that is a green sub pixel region, and the fourth sub pixel region W that is a white sub pixel region, and emits white light. The second organic light emitting element 440 A 2 is formed in the third sub pixel region B, which is a blue sub pixel region, and emits blue light.

The first organic light emitting elements 440 A 1 and 440 B 1 and the second organic light emitting elements 440 A 2 and 440 B 2 will be described in greater detail with reference to FIGS. 4B and 4C below.

FIG. 4C is a conceptual diagram illustrating an organic light emitting display devices 400 C according to another exemplary embodiments of the present invention.

A first organic light emitting element is a portion of an organic light emitting element 440 C formed in a first sub pixel region R which is a red sub pixel region, a second sub pixel region G which is a green sub pixel region, and a fourth sub pixel region W which is a white sub pixel region. The first organic light emitting element includes an anode 441 C, an EL layer 444 C, and a cathode 445 C. The EL layer 444 C includes a first EL layer 444 C 1 and a second EL layer 444 C 2 . The second EL layer 444 C 2 may be an emission layer that emits blue light, and the first EL layer 444 C 1 may be an emission layer that emits other various color lights that are mixed with the blue light to emit white light. The first EL layer 444 C 1 and the second EL layer 444 C 2 are substantially the same as the first EL layer 244 C 1 and the second EL layer 244 C 2 of FIG. 2A , and are thus not redundantly described here. Since FIG. 4C illustrates that the organic light emitting display device 400 C is a top emission type organic light emitting display device, the anode 441 C includes a transparent conductive layer 443 C and a reflective layer 442 C.

A second organic light emitting element is a portion of the organic light emitting element 440 C formed in a third sub pixel region B, which is a blue sub pixel region. The second organic light emitting element includes the anode 441 C, the EL layer 444 C, and the cathode 445 C, and the EL layer 444 C includes the second EL layer 444 C 2 . The second EL layer 444 C 2 is an emission layer that emits blue light. Since FIG. 4C illustrates that the organic light emitting display device 400 C is a top emission type organic light emitting display device, the anode 441 C includes a transparent conductive layer 443 C and a reflective layer 442 C.

The anodes 441 C, the second EL layers 444 C 2 , and the cathodes 445 C of the respective first and second organic light emitting elements may be simultaneously formed in the same process. Specifically, the anodes 441 C of the first and second organic light emitting elements may be simultaneously formed of the same material and to the same thickness in the same process. The second EL layers 444 C 2 of the first and second organic light emitting elements may be simultaneously formed of the same material and to the same thickness in the same process. The cathodes 445 C of the first and second organic light emitting elements may be simultaneously formed of the same material and to the same thickness in the same process.

Although for convenience of explanation, the organic light emitting display devices 400 C of FIG. 4C has been described relating to the organic light emitting display device 400 B of FIG. 4B , the organic light emitting display devices 400 C is substantially the same as the organic light emitting display device 400 A of FIG. 4A except for the fourth sub pixel region W.

FIG. 4D is a conceptual diagram illustrating an organic light emitting display device 400 D according to another exemplary embodiment of the present invention. Elements illustrated in FIG. 4D are substantially the same as those in FIG. 4A when numbers assigned thereto (except for alphabets) are the same and are thus not redundantly described here.

Referring to FIG. 4D , a color filter 490 D including a first color filter 491 D and a second color filter 492 D is formed on a second substrate 415 D corresponding to a first sub pixel region R which is a red sub pixel region and a second sub pixel region G which is a green sub pixel region. The first color filter 491 D corresponds to the first sub pixel region R that is a red sub pixel region, and the second color filter 492 D corresponds to the second sub pixel region G that is a green sub pixel region. Thus, white light emitted from the first organic light emitting element 440 D 1 passes through the first color filter 491 D and is then transformed into red light, and passes through the second color filter 492 D and is then transformed into green light. The color filter 490 D and the second substrate 415 D are substantially the same as the color filter 390 A and the second substrate 315 A of FIG. 3A and are thus not redundantly described here.

FIG. 5 is a flowchart illustrating a method of manufacturing an organic light emitting display device according to an exemplary embodiment of the present invention. FIGS. 6A and 6B are cross-sectional views sequentially illustrating a method of manufacturing an organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 5 , first, a plurality of anodes is formed on a substrate so that each of the anodes is individually addressable. Then, a first electroluminescent (EL) layer and a second electroluminescent (EL) layer are formed on the anodes such that at least a part of the first EL layer and the second EL layer are overlapped at the first area (e.g., an area for emitting substantially white light) of the display device. Here, at least one of the first EL layer or the second EL layer should be formed such that it is extended out to a second area (e.g., an area for emitting constituent colored light of the EL layer) without being overlapped with the other EL layer. A cathode is formed on both the first area and the second area so that the first EL layer and the second EL layer are interposed between the plurality of anodes and the cathode. Then, one or more of color filter elements are arranged to filter the light emitted from the first area.

In this setting, the EL layer being extended out to the second area may emit its own colored light without being filtered by a color filter element while the stack of the first and second EL layers in the first area emits substantially white light, which is to be filtered by one or more of the color filter elements to generate colored light corresponding to the color filter element.

When forming the first and second EL layers, one of the first and second EL layers, which is to be extended out into the second area may be formed first. Then a photoresist may be formed on the EL layer in the second area. The photoresist in the second area is then developed. Following the development of the photoresist, the other EL layer that is to be left in the first area (i.e., complementary EL layer) is formed in the first and second areas. When the photoresist formed in the second area is stripped, the complementary EL layer formed in the second area is also stripped, thereby forming a multi-layered emission layer structure having the first area for emitting white light and the second area for emitting colored light of the EL layer. In some embodiments of the method, the photoresist developing solution and/or the photoresist stripper used in the process of forming the multi-layered emission layer structure contain fluorine, which may reduce the damage to the EL layers during the formation of the multi-layered emission layer structure.

As an alternative way of forming the multi-layered emission layer structure, one of the first and second EL layers can be formed in the first area, and the other EL layer can be formed on the EL layer in both the first and second areas. This method also results in a multi-layered emission layer structure with a stack of the first and second EL layers disposed in the first area for emitting the substantially white light and one of the first and second EL layers being extended into the second area for emitting colored light of the EL layer in the second area.

In one embodiment, the EL layer being extended out into the second area is an EL layer configured to emit substantially blue light, and the other EL layer, which is contained within the first area, is an EL layer configured to emit light having a color complementary to the blue light from the other EL layer. Accordingly, these two EL layers overlap at the first area and collectively emit substantially white light. In this embodiment, the plurality of color filter elements comprises a red color filter element and a green color filter element that are configured to filter the white light to generate red and green light, respectively. In other embodiments, the EL layer being extended out into the second area may be configured to emit substantially red or substantially green colored light, and the other EL layer being contained within the first area may be configured to emit light that is complementary to the red or green colored light. As such, the display device having a multi-layered emission layer structure with improved luminance, color accuracy, power consumption as well as the longer life span can be provided.

The forming of the first EL layer in the first region of the substrate and the forming of the second EL layer in the second region of the substrate will be described in more detail with reference to FIGS. 6A to 6C .

As depicted in FIG. 6A , a first anode 641 A 1 and a second anode 641 A 2 are formed in a first sub pixel region R and a second sub pixel region G corresponding to a first region of a substrate 610 A, respectively, and a third anode 641 A 3 is formed in a third sub pixel region B corresponding to a second region of the substrate 610 A.

Next, a second EL layer 644 A 2 is formed on a first anode 641 A 1 , a second anode 641 A 2 , and a third anode 641 A 3 . The forming of the second EL layer 644 A 2 includes forming a blue emission layer.

Next, a first EL layer 644 A 1 is formed on the second EL layer 644 A 2 . The forming of the first EL layer 644 A 1 includes forming an EL layer 644 A that emits various color lights that are mixed with blue light to form white light. The first EL layer 644 A 1 is substantially the same as the first multi-layered emission layer structure 244 A 1 of FIG. 2A and is thus not redundantly described here.

The forming of the first EL layer 644 A 1 may include forming the first EL layer 644 A 1 using photolithographic process. When the photolithographic process is used, first, a photoresist is formed on the second EL layer 644 A 2 corresponding to the third sub pixel region B. The forming of the photoresist 670 A may include applying a photoresist on the entire second EL layer 644 A 2 , and performing exposure and development on the photoresist to form the photoresist 670 A on the second EL layer 644 A 2 corresponding to the third sub pixel region B. In this case, since the second EL layer 644 A 2 is formed below the photoresist 670 A, the second EL layer 644 A 2 may be damaged during the exposure and development of the photoresist 670 A. In the method of manufacturing an organic light emitting display device according to an exemplary embodiment of the present invention, the photoresist 670 A, a developing solution, and a stripper may be formed of a material containing fluorine to minimize damage to the EL layer 644 A when the photoresist 670 A is developed and removed.

In some embodiments, before the photoresist 670 A is formed, a protective layer may be formed on the second EL layer 644 A 2 to protect the second EL layer 644 A 2 during the photolithographic process. A charge generation layer may be used as the protective layer. By forming the charge generation layer on the second EL layer 644 A 2 , damage to the EL layer 644 A that may occur during the photolithography may be minimized.

Then, a first EL layer 644 A 1 is formed on the second EL layer 644 A 2 on which the photoresist 670 A is formed. Since the first EL layer 644 A 1 is formed by depositing an organic light emitting material 649 A and the photoresist 670 A is formed in the third sub pixel region B, the organic light emitting material 649 A is formed on the second EL layer 644 A 2 in the first sub pixel region R and in the second sub pixel region G and on the photoresist 670 A and in the third sub pixel region B.

Then, referring to FIG. 6B , the photoresist 670 A is removed from the third sub pixel region B. When the photoresist 670 A is removed, the organic light emitting material 649 A formed on the photoresist 670 A is also removed. As described above, the photoresist 670 A may be formed of a material containing fluorine, and a developing solution and a stripper may also be formed of a material containing fluorine. By using the developing solution and the stripper that contain fluorine, damage to the EL layer 644 A may be minimized during the developing and removing of the photoresist 670 A.

FIGS. 7A to 7C are cross-sectional views sequentially illustrating a method of manufacturing an organic light emitting display device according to another exemplary embodiment of the present invention.

First, referring to FIG. 7A , a first anode 741 A 1 and a second anode 741 A 2 are formed in a first sub pixel region R and a second sub pixel region G corresponding to a first region of a substrate 710 A, respectively, and a third anode 741 A 3 is formed in a third sub pixel region B corresponding to a second region of the substrate 710 A.

A first EL layer 744 A 1 is formed on the first anode 741 A 1 and the second anode 741 A 2 . The forming of the first EL layer 744 A 1 includes forming an EL layer 744 A that emits various color lights that are mixed with blue light to form white light. The first EL layer 744 A 1 is substantially the same as the first multi-layered emission layer structure 244 A 1 of FIG. 2A and is thus not redundantly described here.

The forming of the first EL layer 744 A 1 may include forming the first EL layer 744 A 1 according to the photolithographic process. When the photolithographic process is used, first, a photoresist 770 A is formed on the third anode 741 A 3 corresponding to the third sub pixel region B. The forming of the photoresist 770 A may include applying a photoresist on the entire third anode 741 A 3 and performing exposure and development on the photoresist to form the photoresist 770 A on the second EL layer 744 A 2 corresponding to the third sub pixel region B.

Next, a first EL layer 744 A 1 is formed on an anode 741 A on which the photoresist 770 A is formed. The first EL layer 744 A 1 is formed by depositing an organic light emitting material 749 A. Since the photoresist 770 A is formed in the third sub pixel region B, the organic light emitting material 749 A is formed on the anode 741 A in the first sub pixel region R and the second sub pixel region G and on the photoresist 770 A in the third sub pixel region B.

Next, referring to FIG. 7B , the photoresist 770 A is removed from the third sub pixel region B. When the photoresist 770 A is removed, the organic light emitting material 749 A formed on the photoresist 770 A is also removed. The photoresist 770 A may be formed of a material containing fluorine, and a developing solution and a stripper may also be formed a material containing fluorine. By using the developing solution and the stripper that contain fluorine, damage to the EL layer 744 A may be minimized during the developing and removing of the photoresist 770 A.

Then, referring to FIG. 7C , a second EL layer 744 A 2 is formed on the first EL layer 744 A 1 and the third anode 741 A 3 .

FIGS. 8A to 8C are cross-sectional views sequentially illustrating a method of manufacturing an organic light emitting display device according to another exemplary embodiment of the present invention.

First, referring to FIG. 8A , a first anode 841 A 1 and a second anode 841 A 2 are formed in a first sub pixel region R and a second sub pixel region G corresponding to a first region of a substrate 810 A, respectively, and a third anode 841 A 3 is formed in a third sub pixel region B corresponding to a second region of the substrate 810 A.

Next, a first EL layer 844 A 1 is formed on the first anode 841 A 1 and second anode 841 A 2 . The forming of the first EL layer 844 A 1 includes forming an EL layer 844 A that emits various color lights that are mixed with blue light to form white light. The first EL layer 844 A 1 is substantially the same as the first multi-layered emission layer structure 244 A 1 of FIG. 2A and is thus not redundantly described here.

The forming of the first EL layer 844 A 1 may include forming the first EL layer 844 A 1 using laser induced thermal imaging (LITI). Specifically, referring to FIG. 8A , in order to form the first EL layer 844 A 1 using LITI, a base substrate 850 A on which a photoelectric conversion layer 851 A and an organic light emitting material 849 A which is to be transferred are formed is disposed on the first substrate 810 A on which an anode 841 A is formed.

Then, when a laser beam is irradiated onto the first sub pixel region R which is a red sub pixel region and the second sub pixel region G which is a green sub pixel region, photoelectric conversion occurs in the irradiated regions to weaken adhesion between the photoelectric conversion layer 851 A and the organic light emitting material 849 A and to transfer the organic light emitting material 849 A to the first substrate 810 A. As a result, as illustrated in FIG. 8B , the first EL layer 844 A 1 is formed in the first sub pixel region R and the second sub pixel region G.

Then, referring to FIG. 8C , a second EL layer 844 A 2 is formed on the first EL layer 844 A 1 and the third anode 841 A 3 .

According to the one or more embodiments of the present invention, the following effects may be derived.

With a novel organic light emitting element, organic light emitting display device, and method of manufacturing the organic light emitting display device according to the present invention, the efficiency of the organic light emitting element may be improved to increase the lifespan thereof and reduce power consumption therein.

Also, according to the present invention, the efficiency of blue light may be improved using an organic light emitting element that employs a blue emission layer with an improved structure.

The above-described effects according to the present invention are not intended to limit the contents used herein, and further effects may be encompassed in this specification.

It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents.