Phosphors with narrow green emission

A 1:2.133:0.567:4.4 ratio of Eu:Al:B:S was ground in an argon filled glovebox and sealed in a fused silica tube. The sample was heated at 400° C. for 6 hours, then the temperature was increased and held at 800° C. for 12 hours. The sample was cooled to room temperature at about 130° C./hour. The sample was opened in an argon filled glovebox, ground with an additional 10 wt % sulfur and sealed in a fused silica tube and heated a second time with the same heating profile.

FIG. 2A shows an emission spectrum from this sample with excitation at 395 nm. FIG. 2B shows an excitation spectrum for this sample with emission detected at 510 nm. FIG. 2C shows a powder x-ray diffraction (XRD) measurement for this sample, which matches the XRD pattern for EuAl 2 S 4 (standard PDF #01-081-2821). This suggests that some of the excess Al, excess B, and excess S may be present in one or more a binary chalcogenide phases.

A 1:2.322:0.378:4.4 ratio of Eu:Al:Lu:S was ground in an argon filled glovebox and sealed in a fused silica tube. The sample was heated at 400° C. for 6 hours, then the temperature was increased and held at 800° C. for 12 hours. The sample was cooled to room temperature at about 130° C./hour. The sample was opened in an argon filled glovebox, ground with an additional 10 wt % sulfur and sealed in a fused silica tube and heated a second time with the same heating profile.

FIG. 3A shows an emission spectrum from this sample with excitation at 395 nm. FIG. 3B shows an excitation spectrum for this sample with emission detected at 505 nm.

Example 3 EuAl 08 Ga 1.2 S 4 , (Sample Number KB3-125-488), x=0, Comparative Example

Eu, Al 2 S 3 , Ga 2 S 3 , and S were mixed in a stoichiometric ratio and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.116 g Eu, 0.046 g Al 2 S 3 , 0.108 g Ga 2 S 3 , 0.031 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.

Eu, Al 2 S 3 , Ga 2 S 3 , and S were mixed in a stoichiometric ratio and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.113 g Eu, 0.047 g Al 2 S 3 , 0.110 g Ga 2 S 3 , 0.030 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0.1) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0.1) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.1.

Eu, Al 2 S 3 , Ga 2 S 3 , and S were mixed in a stoichiometric ratio, and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.108 g Eu, 0.049 g, Al 2 S 3 , 0.115 g Ga 2 S 3 , 0.028 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0.3) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0.3) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.3.

Eu, Al 2 S 3 , Ga 2 S 3 , and S were mixed in a stoichiometric ratio, and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.103 g Eu, 0.051 g Al 2 S 3 , 0.120 g Ga 2 S 3 , 0.027 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0.5) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0.5) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.5.

Eu, Al 2 S 3 , Ga 2 S 3 , and S were mixed in a stoichiometric ratio, and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.098 g Eu, 0.052 g Al 2 S 3 , 0.124 g Ga 2 S 3 , 0.026 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0.7) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0.7) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.7.

Eu, Al 2 S 3 , Ga 2 S 3 , and S, were mixed in a stoichiometric ratio and an additional 0.25 sulfur per formula unit and 7.5 wt % AlCl 3 were added (0.094 g Eu, 0.054 g Al 2 S 3 , 0.127 g Ga 2 S 3 , 0.025 g S, 0.023 g AlCl 3 ). The mixture was ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The sample was cooled to room temperature at 50° C./hour.

FIG. 4A shows the emission spectrum for this sample (labeled x=0.9) with excitation at 395 nm. FIG. 4B shows the excitation spectrum for this sample (labeled x=0.9) with emission detected at 535 nm. FIG. 4C shows a powder x-ray diffraction (XRD) measurement for this sample, labeled x=0.9.

XRD Data for Examples 3-8

In FIG. 4C the major phase in each XRD pattern matches EuGa 2 S 4 (standard PDF#01-071-0588). Ga 2 S 3 (PDF #00-054-0415) is also present (peaks are marked with stars), and the amount increases as “x” increases. The peaks for both phases are shifted to slightly higher angle than the database patterns, likely due to incorporation of aluminum.

This sample was prepared using an AlF 3 flux, rather than an AlCl 3 flux as in example 7. Eu, Al 2 S 3 , Ga 2 S 3 , and S, were mixed in a stoichiometric ratio. An additional 0.25 sulfur per formula unit and 7.5 wt % AlF 3 were added. The mixture was ground in an argon filled glovebox and sealed in a carbon coated fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 800° C. for 6 hours. The samples were cooled to room temperature at 50° C./hour.

This sample was prepared using an AlF 3 flux, rather than an AlCl 3 flux as in example 3. Eu, Al 2 S 3 , Ga 2 S 3 , and S, were mixed in a stoichiometric ratio. An additional 0.25 sulfur per formula unit and 7.5 wt % AlF 3 were added. The mixture was ground in an argon filled glovebox and sealed in a carbon coated fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 800° C. for 6 hours. The samples were cooled to room temperature at 50° C./hour.

Stoichiometric amounts of Eu, Al, and Se were thoroughly ground in a mortar with a pestle in the glove box. The mixture was placed in dried, carbon coated silica tubes, which were evacuated and sealed at a length of about 5 in. The reaction was carried out in a box furnace. The temperature was raised to 400° C. and held for 6 hours and raised again to 800° C. and held for 6 hours, then cooled to room temperature for 6 hours.

FIG. 5A shows the emission spectrum for this sample (labeled “a”) for excitation at 395 nm. The relative intensity of the emission peak is 100% compared to the other emission spectra in this figure. FIG. 5B shows the excitation spectrum for this sample (labeled “a”) with emission detected at 490 nm.

Stoichiometric amounts of Eu, Al, and Se were thoroughly ground in a mortar with a pestle in the glove box. The mixture was placed in dried, carbon coated silica tubes, which were evacuated and sealed at a length of about 5 in. The reaction was carried out in a box furnace. The temperature was raised to 400° C. and held for 6 hours and raised again to 800° C. and held for 6 hours, then cooled to room temperature for 6 hours.

FIG. 5A shows the emission spectrum for this sample (labeled “b”) for excitation at 395 nm. The relative intensity of the emission peak is 144% compared to the other emission spectra in this figure. FIG. 5B shows the excitation spectrum for this sample (labeled “b”) with emission detected at 490 nm.

Stoichiometric amounts of Eu, Al, Se, and S were thoroughly ground in a mortar with a pestle in the glove box. The mixture was placed in dried, carbon coated silica tubes, which were evacuated and sealed at a length of about 5 in. The reaction was carried out in a box furnace. The temperature was raised to 400° C. and held for 6 hours and raised again to 800° C. and held for 6 hours, then cooled to room temperature for 6 hours.

FIG. 5A shows the emission spectrum for this sample (labeled “c”) for excitation at 395 nm. The relative intensity of the emission peak is 117% compared to the other emission spectra in this figure. FIG. 5B shows the excitation spectrum for this sample (labeled “c”) with emission detected at 490 nm.

Stoichiometric amounts of Eu, Al, and Se were thoroughly ground in a mortar with a pestle in the glove box. The mixture was placed in dried, carbon coated silica tubes, which were evacuated and sealed at a length of about 5 in. The reaction was carried out in a box furnace. The temperature was raised to 400° C. and held for 6 hours and raised again to 800° C. and held for 6 hours, then cooled to room temperature for 6 hours.

FIG. 5A shows the emission spectrum for this sample (labeled “d”) for excitation at 395 nm. The relative intensity of the emission peak is 224% compared to the other emission spectra in this figure. FIG. 5B shows the excitation spectrum for this sample (labeled “d”) with emission detected at 490 nm.

Eu, Al 2 S 3 , In 2 S 3 , and S were mixed in a stoichiometric ratio. The mixtures were ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The samples were cooled to room temperature at 50° C./hour.

FIG. 6 shows the emission spectrum for this sample for excitation at 405 nm.

Eu, Al 2 S 3 , In 2 S 3 , and S were mixed in a stoichiometric ratio. The mixtures were ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The samples were cooled to room temperature at 50° C./hour.

FIG. 7 shows the emission spectrum for this sample for excitation at 405 nm.

Eu, Al 2 S 3 , Ga 2 S 3 , In 2 S 3 , and S were mixed in a stoichiometric ratio. The mixtures were ground in an argon filled glovebox and sealed in a fused silica tube. The samples were heated at 400° C. for 1 hour, then the temperature was increased and held at 900° C. for 6 hours. The samples were cooled to room temperature at 50° C./hour.

FIG. 8 shows the emission spectrum for this sample for excitation at 405 nm.

A 1.2 g mixture of stoichiometric amounts of Eu, Al 2 S 3 , Ga 2 S 3 and S was prepared under Ar. The mixture was combined with 20 wt % excess S, and separated into five 200 mg portions for use in this example and in examples 19-22. For this example one 200 mg portion of the mixture was thoroughly mixed with 30 mg (15 wt %) of an AlBr 3 flux and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 2 hours, dwelled for 1 hour at that temperature, and then was heated to 900° C. over 1.5 hours and dwelled at that temperature for 6 h before being slowly cooled to room temperature at 50° C./hr.

A 200 mg portion of the 1.2 g mixture of stoichiometric amounts of Eu, Al 2 S 3 , Ga 2 S 3 and S prepared in Example 18 was thoroughly mixed with 30 mg (15 wt %) of a GaBr 3 flux and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 2 hours, dwelled for 1 hour at that temperature, and then was heated to 900° C. over 1.5 hours and dwelled at that temperature for 6 h before being slowly cooled to room temperature at 50° C./hr.

A 200 mg portion of the 1.2 g mixture of stoichiometric amounts of Eu, Al 2 S 3 , Ga 2 S 3 and S prepared in Example 18 was thoroughly mixed with 30 mg (15 wt %) of a GaCl 3 flux and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 2 hours, dwelled for 1 hour at that temperature, and then was heated to 900° C. over 1.5 hours and dwelled at that temperature for 6 h before being slowly cooled to room temperature at 50° C./hr.

A 200 mg portion of the 1.2 g mixture of stoichiometric amounts of Eu, Al 2 S 3 , Ga 2 S 3 and S prepared in Example 18 was thoroughly mixed with 30 mg (15 wt %) of a EuCl 3 flux and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 2 hours, dwelled for 1 hour at that temperature, and then was heated to 900° C. over 1.5 hours and dwelled at that temperature for 6 h before being slowly cooled to room temperature at 50° C./hr.

A 200 mg portion of the 1.2 g mixture of stoichiometric amounts of Eu, Al 2 S 3 , Ga 2 S 3 and S prepared in Example 18 was thoroughly mixed with 30 mg (15 wt %) of a EuI 2 flux and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 2 hours, dwelled for 1 hour at that temperature, and then was heated to 900° C. over 1.5 hours and dwelled at that temperature for 6 h before being slowly cooled to room temperature at 50° C./hr.

Example 23 Eu 0.97 Gd 0.03 Al 0.92 Ga 1.38 S 4.45 (Sample Number YBG-170424-2)

Stoichiometric amount of Eu, Al, Ga 2 S 3 , Gd 2 O 3 , S, and 5 wt % excess S were thoroughly ground in a mortar with a pestle in the glove box. The mixtures were placed in dried silica tubes, which were evacuated and sealed at a length of about 5 in. Reactions were carried out in a box furnace. The temperature was raised to 900° C. for 4 hours and held for 12 hours then cooled to room temperature for 6 hours.

A mixture of stoichiometric amounts of Eu, Al, S, and a few wt. % excess of S was thoroughly mixed under argon and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 6 hours, dwelled for 6 hours at that temperature, and then was heated to 800° C. and dwelled at that temperature for 24 hours before being cooled to room temperature over 9 hours. The sample was thoroughly mixed under argon and sealed in an evacuated quartz tube. The heating step was repeated.

A mixture of stoichiometric amounts of Eu, Al, S, and a few wt. % excess of S was thoroughly mixed under argon and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 6 hours, dwelled for 6 hours at that temperature, and then was heated to 800° C. and dwelled at that temperature for 24 hours before being cooled to room temperature over 6 hours. The sample was thoroughly mixed under argon and sealed in an evacuated quartz tube. The heating step was repeated.

A mixture of stoichiometric amounts of Eu, Al, S, and a few wt. % excess of S was thoroughly mixed under argon and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 6 hours, dwelled for 6 hours at that temperature, and then was heated to 800° C. and dwelled at that temperature for 120 hours before being cooled to room temperature over 6 hours. The sample was thoroughly mixed under argon and sealed in an evacuated quartz tube. The heating step was repeated with the dwell step at 800° C. for 48 hours.

A mixture of stoichiometric amounts of Eu, Al, S, and a few wt. % excess of S was thoroughly mixed under argon and sealed in an evacuated quartz tube. The ampoule was heated to 400° C. over 6 hours, dwelled for 6 hours at that temperature, and then was heated to 800° C. and dwelled at that temperature for 48 hours before being cooled to room temperature over 6 hours. The sample was thoroughly mixed under argon and sealed in an evacuated quartz tube. The heating step was repeated.

Relative photoluminescent intensities were compared for EuAl 2 S 4 , EuAl 2.33 S 4.28 , EuAl 2.7 S 5.05 , and EuAl 2.9 S 5.35 using 395 nm excitation. Setting EuAl 2 S 4 as 100%, EuAl 2.33 S 4.28 was more intense at 109%, EuAl 2.7 S 5.05 was the most intense at 378% and EuAl 2.9 S 5.35 was also more intense than the comparative example by 292%.

Stoichiometric amounts of Eu, Ga 2 S 3 and S, with 20 wt % excess S were homogenized under argon. The mixture was combined with 136 mg (6 mg/cm 3 ) I 2 prior to sealing in an approx. 8 in evacuated quartz tube. The ampoule was placed in a horizontal tube furnace with a natural gradient and heated to 400° C. over 6 h, dwelled for 6 h, then heated to 900° C. over 2.5 h and dwelled for 72 h before being slowly cooled to room temperature over 24 h. The phosphor powder had a peak emission wavelength of 549 nm and a full width at half maximum of 43 nm when excited with 405 nm light from an LED.

Stoichiometric amounts of Eu, Ga 2 S 3 and S, with 20 wt % excess S were homogenized under argon. The mixture was combined with 60 mg (15 wt %) GaCl 3 prior to sealing in an approx. 8 in evacuated quartz tube. The ampoule was placed in a horizontal tube furnace with a natural gradient and heated to 400° C. over 6 h, dwelled for 6 h, then heated to 900° C. over 2.5 h and dwelled for 72 h before being slowly cooled to room temperature over 24 h. The phosphor powder had a peak emission wavelength of 551 nm and a full width at half maximum of 39 nm when excited with 405 nm light from an LED.

Stoichiometric amounts of Eu, Ga 2 S 3 and S, with 20 wt % excess S were homogenized under argon. The mixture was combined with 136 mg (6 mg/cm 3 ) I 2 prior to sealing in an approx. 8 in evacuated quartz tube. The ampoule was placed in a horizontal tube furnace with a natural gradient and heated to 400° C. over 6 h, dwelled for 6 h, then heated to 900° C. over 2.5 h and dwelled for 72 h before being slowly cooled to room temperature over 24 h. The phosphor powder had a peak emission wavelength of 549 nm and a full width at half maximum of 41 nm when excited with 405 nm light from an LED, and appeared visibly brighter than the comparative example 28.

Stoichiometric amounts of Eu, Ga 2 S 3 and S, with 20 wt % excess S were homogenized under argon. The mixture was combined with 60 mg (15 wt %) GaCl 3 prior to sealing in an approx. 8 in evacuated quartz tube. The ampoule was placed in a horizontal tube furnace with a natural gradient and heated to 400° C. over 6 h, dwelled for 6 h, then heated to 900° C. over 2.5 h and dwelled for 72 h before being slowly cooled to room temperature over 24 h. The phosphor powder had a peak emission wavelength of 550 nm and a full width at half maximum of 39 nm when excited with 405 nm light from an LED, and appeared visibly brighter than the comparative example 29.

Phosphor Converted LED Examples

A phosphor slurry was created by combining 21.40 mg Dow Corning OE-6550 2 part silicone, 0.98 mg red phosphor, BR101J and 2.67 mg of a green phosphor of the present invention (example 5, EuAl 0.92 Ga 1.38 S 4.45 , x=0.3). Phosphor converted LEDs 1-3 (examples 24-26 below) were fabricated using portions of this slurry, and vary from each other only in the amount of slurry deposited on the LED.

The phosphor slurry described above was applied on top of a blue emitting InGaN based LED mounted in a 2835 PLCC package from Power Opto Co., and the silicone was cured overnight at ca. 100° C. The emission spectrum of this LED, shown in FIG. 9 , was measured with an Ocean Optics spectrometer. The phosphor converted LED of this example was measured to have a correlated color temperature (CCT) of 4625K, a duv of 0.0046, and a CRI of 83, corresponding to a neutral white.

The phosphor slurry described above was applied on top of a blue emitting InGaN based LED mounted in a 2835 PLCC package from Power Opto Co., and the silicone was cured overnight at ca. 100° C. The emission spectrum of this LED, shown in FIG. 10 , was measured with an Ocean Optics spectrometer. The cured layer of slurry on the LED in this example was thinner than that in Example 25 (phosphor converted LED 1). The phosphor converted LED of this example was measured to have a correlated color temperature (CCT) of 6575K, a duv of 0.0045, and a CRI of 85, corresponding to a cool white.

The phosphor slurry described above was applied on top of a blue emitting InGaN based LED mounted in a 2835 PLCC package from Power Opto Co., and the silicone was cured overnight at ca. 100° C. The emission spectrum of this LED, shown in FIG. 11 , was measured with an Ocean Optics spectrometer. The cured layer of slurry on the LED in this example was thinner than that in Example 26 (phosphor converted LED 2). The phosphor converted LED of this example was measured to have CIE xy coordinates of 0.253, 0.250, suitable for backlighting applications. FIG. 12 shows the emission (solid line) from this phosphor converted LED overlaid with an example set of LCD color filters: blue (long dash), green (alternating dash and dot), and red (short dash). The emission spectrum is a good match for the example color filters shown in the figure.

Various embodiments are described in the following clauses.

Clause 1. A luminescent composition of matter characterized by the formula REM 2+x E y , wherein:

RE is one or more rare earth elements;

M is one or more elements selected from the group Al, Ga, B, In, Sc, Lu, and Y;

E is one or more elements selected from the group S, Se, O, and Te;

x is greater than zero; and

y has the value that achieves charge balance in the formula assuming that E has a charge of −2.

Clause 2. The luminescent composition of matter of clause 1, wherein RE is Eu.

Clause 3. The luminescent composition of matter of clause 1, wherein RE comprises Eu and Gd.

Clause 4. The luminescent composition of matter of clause 1, having exclusively an EuM 2 E 4 . pseudoorthorhombic crystal structure.

Clause 5. The luminescent composition of matter of clause 1, having a mixture of predominantly an EuM 2 E 4 pseudoorthorhombic crystal structure and one or more binary chalcogenide crystal structures.

Clause 6. The luminescent composition of matter of any of clauses 1-5, wherein the composition is characterized by the formula Eu(Al 0.4 Ga 0.6 ) 2+x S y , where x is greater than zero.

Clause 7. The luminescent composition of matter of any of clauses 1-5, wherein:

M is Al; and

E is S, Se, or a mixture of S and Se.

Clause 8. The luminescent composition of matter of any of clauses 1-7, wherein x is greater than or equal to 0.5.

Clause 9. The luminescent composition of matter of any of clauses 1-8, wherein x is greater than or equal to 0.7.

Clause 10. The luminescent composition of matter of any of clauses 1-5, wherein the composition is characterized by the formula EuAl 1.08 Ga 1.62 S 5.05 .

Clause 11. A light emitting device comprising a phosphor of any of clauses 1-10.

Clause 12. A phosphor converted light emitting diode comprising:

a light emitting diode emitting light over a first wavelength range; and

a phosphor of any of clauses 1-10 arranged to be excited by emission from the light emitting diode and in response emit light over a second wavelength range.

This disclosure is illustrative and not limiting. Further modifications will be apparent to one skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.