Phosphors and visible and UV light emitting devices utilizing the same

This Application claims priority of Taiwan Patent Application No. 100132977, filed on Sep. 14, 2011, the entirety of which is incorporated by reference herein.

1. Field of the Invention

The disclosure relates to a phosphor, and in particular relates to a light emitting device utilizing the same.

2. Description of the Related Art

Excitation and emission properties of inorganic phosphors are mainly determined by host materials, activators, and other dopants. Phosphors composed of different host materials, activators or other dopants may have different luminescent properties, such that the composition is the most important factor to tune optoelectronic properties of the phosphors. Mainstream host materials of inorganic phosphors are sulfides, oxides, oxysulfides, or other complex oxides such as silicates, aluminates, phosphates, and the likes. Recently, phosphor development of host materials has been partly moved towards nitrides and oxynitrides. The major activators being used are ions of transition metal elements or rare-earth elements.

A future light source should meet environmental protection requirements of mercury-less/mercury-free, such that a Xe 2 * excimer lamp and light emitting diode (LED) with high efficiency will possibly become a mainstream future light source. Whether the Xe 2 * excimer lamp or the LED is adopted, it should probably collocate with a phosphor to convert light from being a short wavelength to being a long wavelength. For example, the Xe 2 * excimer lamp emits a vacuum ultraviolet (VUV) light having a wavelength of 172 nm, which can be converted by an appropriate phosphor to emit a UV-C light having a wavelength of 200 nm to 280 nm, which may be applied in disinfection, purification, TOC (total organic compounds) reduction, and the likes. The LED has a narrow emission band, which can be converted by an appropriate phosphor to complete a white light emitting diode, which may be applied in illumination, displays, and the likes. Accordingly, the Xe 2 * excimer lamp and the LED need appropriate phosphors. However, conventional phosphors excitable by the VUV light from the Xe 2 * excimer lamp are rare, and conventional phosphors excitable by the LED are bounded by patents, respectively. Accordingly, developments of novel phosphors are still called for.

One embodiment of the disclosure provides a phosphor, having a formula: M(M′ 1-y-z Eu y Mn z )(M″ 1-x Pr x )(PO 4 ) 2 , wherein M is a monovalent metal element selected from Li, Na, K, or combinations thereof, M′, Eu, and Mn are divalent metal elements, and M′ is selected from Ca, Sr, Ba, Mg, Zn, or combinations thereof, M″ and Pr are trivalent metal elements, and M″ is selected from Sc, Y, La, Lu, Al, Ga, In, or combinations thereof, wherein 0≦x≦0.2, 0≦y≦0.1, 0≦z≦0.2, and x+y+z≠0.

One embodiment of the disclosure provides an ultraviolet light emitting device, comprising: an excitation light source; and the described phosphor, wherein the excitation emits a light having a wavelength of 140 nm to 240 nm.

One embodiment of the disclosure provides a visible light emitting device, comprising: an excitation light source, and the described phosphor, wherein the excitation emits a light having a wavelength of 250 nm to 450 nm.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

The disclosure can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 shows an ultraviolet light emitting device according to one embodiment of the disclosure;

FIG. 2 shows a visible light emitting device according to one embodiment of the disclosure;

FIG. 3 shows an X-ray diffraction spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 according to one embodiment of the disclosure;

FIG. 4 shows a photoluminescence excitation (PLE) spectrum and a photoluminescence (PL) spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 according to one embodiment of the disclosure;

FIG. 5 shows emission spectra of the phosphors KCa(Y 1-x Pr x )(PO 4 ) 2 having different doping ratios of the activator Pr 3+ , wherein x was 0.01, 0.02, 0.05, 0.1, and 0.15, respectively, according to one embodiment of the disclosure;

FIG. 6 shows a distribution of emission intensities at 253 nm of the phosphor KCa(Y 1-x Pr x )(PO 4 ) 2 , having different doping ratios of the activator Pr 3+ , excited by an excitation light source of 172 nm according to one embodiment of the disclosure;

FIG. 7 shows a wide band type emission spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 excited by an excitation light source of 172 nm;

FIG. 8 shows an emission spectra comparison of the phosphors KCa(M″ 0.9 Pr 0.1 )(PO 4 ) 2 (M″=Y, La, or Lu) and CYP according to one embodiment of the disclosure;

FIG. 9 shows an emission spectra comparison of the phosphors KSr(M″ 0.9 Pr 0.1 )(PO 4 ) 2 (M″=Y, La, or Lu) according to one embodiment of the disclosure;

FIG. 10 shows an emission spectra comparison of the phosphor NaCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 according to one embodiment of the disclosure;

FIG. 11 shows an X-ray diffraction spectrum of the phosphor K(Ca 0.98 Eu 0.01 Mn 0.01 )Y(PO 4 ) 2 according to one embodiment of the disclosure;

FIG. 12 shows a photoluminescence excitation (PLE) spectrum and a photoluminescence (PL) spectrum of the phosphor K(Ca 0.99 Eu 0.01 )Y(PO 4 ) 2 , according to one embodiment of the disclosure;

FIG. 13 shows an emission spectrum of Eu 2+ and an excitation spectrum of Mn 2+ in the phosphors K(Ca 1-y-z Eu y Mn z )Y(PO 4 ) 2 according to one embodiment of the disclosure;

FIG. 14 shows an emission spectra comparison of the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 having different doping ratios of the activator Mn 2+ according to one embodiment of the disclosure;

FIG. 15 shows CIE coordinates of the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 having different doping ratios of the activator Mn 2+ according to one embodiment of the disclosure; and

FIG. 16 shows an emission spectrum of a white light emitting diode manufactured of the phosphor K(Ca 0.94 Eu 0.01 Mn 0.05 )Y(PO 4 ) 2 collocated with a near-UV LED chip having an emission wavelength of 380 nm according to one embodiment of the disclosure.

The following description is of the best-contemplated mode of carrying out the disclosure. This description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims.

In general, phosphors with a phosphate host material have a wide band gap, and can be doped with different activators to exhibit different excitation and emission characteristics. In short, the phosphate is a multi-purpose host material system. In embodiments of the disclosure, the phosphate MM′M″(PO 4 ) 2 is selected as a host material doped with the activators Pr 3+ , Eu 2+ , and Mn 2+ . M is a monovalent metal element selected from Li, Na, K, or combinations thereof. M′ is a divalent metal element selected from Ca, Sr, Ba, Mg, Zn, or combinations thereof. M″ is a trivalent metal element selected from Sc, Y, La, Lu, Al, Ga, In, or combinations thereof. Because a Pr 3+ ion has a suitable energy level to emit UV-C light, it can be doped into the phosphate host material MM′M″(PO 4 ) 2 to be applied as a UV light emitting phosphor. As such, the phosphate doped with Pr 3+ can be collocated with an Xe 2 * excimer lamp to complete a UV-C light source free of mercury. On the other hand, the sensitizer-activator pair of Eu 2+ and Mn 2+ has energy transfer effect while co-doping with Eu 2+ and Mn 2+ . The doping ratio of Eu 2+ and Mn 2+ can be changed to modify the visible emission light color of the phosphate phosphor MM′M″(PO 4 ) 2 , which may serve as a color tunable phosphor in a white light emitting diode applied in the illumination or display fields.

According to one embodiment of the disclosure, the phosphate phosphor has a formula as below:

M(M′ 1-y-z Eu y Mn z )(M″ 1-x Pr x )(PO 4 ) 2   (Formula 1)

In Formula 1, M is a monovalent metal element selected from Li, Na, K, or combinations thereof. M′, Eu, and Mn are divalent metal elements, and M′ is selected from Ca, Sr, Ba, Mg, Zn, or combinations thereof. M″ and Pr are trivalent metal elements, and M″ is selected from Sc, Y, La, Lu, Al, Ga, In, or combinations thereof. 0≦x≦0.2, 0≦y≦0.1, 0≦z≦0.2, and x+y+z≠0.

If y and z in Formula 1 are equal to 0 (y=z=0), the phosphor will have a formula of MM′(M″ 1-x Pr x )(PO 4 ) 2 and x≠0, wherein the phosphor can be excited by a light having a wavelength of 140 nm to 240 nm to emit an ultraviolet light having a major emission peak of 240 nm to 320 nm. The phosphor MM′ (M″ 1-x Pr x )(PO 4 ) 2 can be applied in an ultraviolet light emitting device. According to one embodiment, the ultraviolet light emitting device 10 includes a lamp 12 , an excitation light source 16 , electrodes 18 , and the phosphor 14 (MM′(M″ 1-x Pr x )(PO 4 ) 2 ) coated on the inner side of the lamp 12 , as shown in FIG. 1 . The excitation light source 16 can be a Xe 2 * excimer lamp or other light source emitting a light having a wavelength of 140 nm to 240 nm.

If x in Formula 1 is equal to 0 (x=0), the phosphor will have a formula of M(M′ 1-y-z Eu y Mn z )M″(PO 4 ) 2 and y+z≠0, wherein the phosphor can be excited by a light having a wavelength of 250 nm to 450 nm to emit a visible light having a major emission peak of 450 nm to 750 nm. The phosphor M(M′ 1-y-z Eu y Mn z )M″(PO 4 ) 2 can be applied in a visible light emitting device. According to one embodiment, the visible light emitting device 100 includes an excitation light source 102 having positive and negative electrodes electrically connected to lead frames 104 of opposite voltages, respectively. The phosphor 106 (M(M′ 1-y-z Eu y Mn z )M″(PO 4 ) 2 ) is mixed into a transparent resin 108 , and the mixture is then applied to encapsulating the excitation light source 102 . Thereafter, the described structure is sealed by a sealing material 110 to complete the visible light emitting device as shown in FIG. 2 . The excitation light source 102 can be an LED, laser diode, or other light source emitting a light having a wavelength of 250 nm to 450 nm.

In addition, the disclosure also provides a method to manufacturing the described phosphate phosphors. First, (1) a compound containing M and oxygen, (2) a compound containing M′ and oxygen, (3) (NH 4 ) 2 HPO 4 or (NH 4 )H 2 PO 4 , and (4) a compound containing Pr (or Eu and Mn) and oxygen were mixed to obtain a mixture. The mixture is then sintered at a temperature of 950° C. to 1250° C. After the mixture is heated to the sintering temperature, the mixture is sintered at the sintering temperature for eight hours to thirty-two hours. According to the embodiments, the compounds containing M and oxygen can be metal oxides, metal carbonates, or metal nitrates of Li, Na, or K. In addition, the compound containing M′, Pr (or Eu and Mn) and oxygen can be metal oxides or metal nitrites.

According to molar ratios of KCa(Y 1-x Pr x )(PO 4 ) 2 , wherein x was 0.01, 0.02, 0.05, 0.1, and 0.15, respectively, appropriate stoichiometry of K 2 CO 3 , CaCO 3 , Y 2 O 3 , Pr 2 O 3 , and (NH 4 ) 2 HPO 4 were evenly mixed and ground for ten minutes, and charged into a crucible. The crucible was then heated in a high temperature furnace. After sintering at 950° C.-1250° C. in air, the phosphors KCa(Y 1-x Pr x )(PO 4 ) 2 having different Y/Pr ratios were prepared.

FIG. 3 shows an X-ray diffraction spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 , which has excellent crystallinity. As shown in FIG. 3 , a small amount of doping Pr 3+ did not influence the crystal structure of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 .

FIG. 4 shows a photoluminescence excitation (PLE) spectrum and a photoluminescence (PL) spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 . As shown in FIG. 4 , the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 has an excitation band of 140 nm to 240 nm, and an emission band of 240 nm to 320 nm.

FIG. 5 shows emission spectra of the phosphors KCa(Y 1-x Pr x )(PO 4 ) 2 having different doping ratios of the activator Pr 3+ , wherein x was 0.01, 0.02, 0.05, 0.1, and 0.15, respectively.

FIG. 6 shows a distribution of emission intensities at 253 nm of the phosphor KCa(Y 1-x Pr x )(PO 4 ) 2 , having different doping ratios of the activator Pr 3+ , excited by an excitation light source of 172 nm. As shown in FIG. 6 , the preferred doping ratio of the activator Pr 3+ is about 10% (x≈0.1).

For determining whether the phosphor KCa(Y 1-x Pr x )(PO 4 ) 2 has excellent ultraviolet light emitting property, the wide band type emission spectra of the phosphors were further analyzed. FIG. 7 shows a wide band type emission spectrum of the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 excited by an excitation light source of 172 nm. As shown in FIG. 7 , the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 emits a trace amount of a visible light around 550 nm, and emits a great amount of ultraviolet lights of 240 nm to 320 nm. As such, the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 is an excellent ultraviolet light emitting phosphor.

Similarly, the ultraviolet light emitting phosphor MM′(M″ 1-x Pr x )(PO 4 ) 2 having different cations may be synthesized by different raw materials (with corresponding stoichiometry) and similar processes. FIG. 8 shows an emission spectra comparison of the phosphors KCa(M″ 0.9 Pr 0.1 )(PO 4 ) 2 (M″=Y, La, or Lu) and CYP (Ca 9 (Y 1-x Pr x ) (PO 4 ) 7 , prepared by Example 23 in Taiwan Application No. 98134483). FIG. 9 shows an emission spectra comparison of the phosphors KSr(M″ 0.9 Pr 0.1 )(PO 4 ) 2 (M″=Y, La, or Lu). FIG. 10 shows an emission spectra comparison of the phosphor NaCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 . As shown in FIGS. 8-10 , the phosphors KCa(Lu 0.9 Pr 0.1 )(PO 4 ) 2 and KSr(Y 0.9 Pr 0.1 ) (PO 4 ) 2 have similar ultraviolet light emitting efficiency as the phosphor KCa(Y 0.9 Pr 0.1 )(PO 4 ) 2 .

According to molar ratios of K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 , wherein z was 0, 0.01, 0.02, 0.04, 0.05, 0.07, and 0.10, respectively, appropriate stoichiometry of K 2 CO 3 , CaCO 3 , Y 2 O 3 , EuO, MnO, and (NH 4 ) 2 HPO 4 were evenly mixed and ground for ten minutes, and charged into a crucible. The crucible was then heated in a high temperature furnace. After sintering at 950° C.-1250° C. under air, the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 having different Ca/Mn ratios were prepared.

FIG. 11 shows an X-ray diffraction spectrum of the phosphor K(Ca 0.98 Eu 0.01 Mn 0.01 )Y(PO 4 ) 2 , which has excellent crystallinity. As shown in FIG. 3 , a small amount of doping Eu 2+ and Mn 2+ did not influence the crystal structure of the phosphor K(Ca 0.98 Eu 0.01 Mn 0.01 )Y(PO 4 ) 2 .

FIG. 12 shows a photoluminescence excitation (PLE) spectrum and a photoluminescence (PL) spectrum of the phosphor K(Ca 0.99 Eu 0.01 )Y(PO 4 ) 2 . As shown in FIG. 12 , the phosphor K(Ca 0.99 Eu 0.01 )Y(PO 4 ) 2 has an excitation band of 250 nm to 450 nm, an emission band of 425 nm to 700 nm, and an emission peak of about 480 nm.

FIG. 13 shows an emission spectrum of Eu 2+ and an excitation spectrum of Mn 2+ in the phosphors K(Ca 1-y-z Eu y Mn z )Y(PO 4 ) 2 , wherein y+z≠0. As shown in FIG. 13 , the emission spectrum of Eu 2+ overlaps with the excitation spectrum of Mn 2+ , thereby causing energy transfer. In other words, Eu 2+ may serve as a sensitizer of Mn 2+ .

FIG. 14 shows an emission spectra comparison of the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 having different doping ratios of the activator Mn 2+ , wherein the doping ratio of Eu 2+ was 1%.

FIG. 15 shows CIE coordinates of the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 having different doping ratios of the activator Mn 2+ , wherein the doping ratio of Eu 2+ was 1%. As shown in FIG. 15 , the CIE coordinates of the phosphor K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 shift from green blue to red purple when the doping ratio of the activator Mn 2+ increases. The detailed CIE coordinates of the phosphors K(Ca 0.99-z Eu 0.01 Mn z )Y(PO 4 ) 2 are shown in Table 1.

FIG. 16 shows an emission spectrum of a white light emitting diode fabricated by the phosphor K(Ca 0.94 Eu 0.01 Mn 0.05 )Y(PO 4 ) 2 collocated with a near-UV LED chip having an emission wavelength of 380 nm. As shown in FIG. 16 , the single phosphor K(Ca 0.94 Eu 0.01 Mn 0.05 )Y(PO 4 ) 2 having two emission peaks may be collocated with the near-UV LED chip to complete the white light emitting diode, which emitted a light having a color temperature of 7325K and a CIE coordinate of (0.314, 0.277).

While the disclosure has been described by way of example and in terms of the preferred embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.