Phosphor layer for micro-LED applications
Embodiments include a device having a micro-LED that includes at least two, individually addressable light emitting diodes on a same substrate; a phosphor converter layer disposed on the micro-LED, the phosphor converter layer including phosphor particles having a D50 of greater than 1 μm and less than 10 μm.
1. A device comprising:
a micro-LED comprising at least two individually addressable light emitting diodes on a same substrate; and
a phosphor converter layer disposed on the micro-LED and extending over the at least two light emitting diodes and across a gap therebetween, the phosphor converter layer comprising a plurality of phosphor particles having an average particle size or median diameter (D50) of greater than 1 μm and less than 10 μm, wherein a thickness of the phosphor converter layer is greater than 4 μm and less than 20 μm, wherein the phosphor converter layer further comprises a thin layer of non-luminescent material coating on the phosphor particles, and wherein the thin layer has a thickness of less than 200 nm,
the at least two light emitting diodes exhibiting a contrast ratio greater than 1:18, said contrast ratio resulting at least in part from the D50 of the phosphor particles and the thickness of the phosphor converter layer.
2. The device of claim 1 , wherein the plurality of phosphor particles has a D50 of greater than 2 μm and less than 7 μm.
3. The device of claim 2 , wherein the plurality of phosphor particles has a D50 of greater than 3 μm and less than 5 μm.
4. The device of claim 1 , wherein the thickness of the phosphor converter layer is greater than 8 μm and less than 15 μm.
5. The device of claim 1 , wherein the thickness of the phosphor converter layer is greater than 10 μm and less than 13 μm.
6. The device of claim 1 , wherein the phosphor converter layer further comprises a matrix, and the matrix has a refractive index of 1 or greater and less than or equal to 1.5.
7. The device of claim 6 , wherein the matrix has a refractive index of 1 or greater and less than 1.4.
8. The device of claim 7 , wherein the matrix has a refractive index of 1 or greater and less than 1.2.
9. The device of claim 1 , wherein the thin layer comprises a metal oxide.
10. The device of claim 9 , wherein the thin layer comprises at least one of Al 2 O 3 , HfO 2 , Ta 2 O 5 , ZrO 2 , TiO 2 , and SiO 2 .
11. The device of claim 1 , wherein the thin layer has a thickness between 40-150 nm.
12. The device of claim 1 , the contrast ratio being greater than 1:100.
13. A method for making the device of claim 1 , the method comprising:
depositing the plurality of phosphor particles in a layer that extends over the at least two light emitting diodes on the substrate and across the gap between the at least two light emitting diodes; and
forming the thin layer of non-luminescent material so as to coat the phosphor particles.
14. The method of claim 13 , wherein the phosphor converter layer is deposited by spray coating or sedimentation.
15. The method of claim 13 , wherein the thin layer is formed by atomic layer deposition.
16. The method of claim 13 , wherein the thin layer comprises a metal oxide.
17. The method of claim 16 , wherein the thin layer comprises at least one of Al 2 O 3 , HfO 2 , Ta 2 O 5 , ZrO 2 , TiO 2 , and SiO 2 .
18. The method of claim 13 , wherein the plurality of phosphor particles has a D50 of greater than 2 μm and less than 7 μm.
19. The method of claim 13 , wherein the thickness of the phosphor converter layer is greater than 8 μm and less than 15 μm.
20. The method of claim 13 , wherein the phosphor converter layer further comprises a matrix, and the matrix has a refractive index of 1 or greater and less than or equal to 1.5.