Increased emission efficiency in organic light-emitting devices on high-index substrates
View Patent ↗A device is provided. The device includes a substrate, a first electrode disposed over the substrate, a small molecule organic emissive layer disposed over the first electrode, and a second electrode disposed over the organic emissive layer. The substrate has a first index of refraction, and the organic emissive layer has a second index of refraction. The first index of refraction is higher than the second index of refraction. The device may have an external electroluminescent efficiency of at least about 56%. Bulky substituents or dopants may be used to decrease the index of refraction and/or the density of the organic emissive layer.
1. A device, comprising:
(a) a substrate having a first index of refraction;
(b) a first electrode disposed over the substrate;
(c) an organic emissive layer disposed over the first electrode, the organic emissive layer comprising a small molecule organic material, the organic emissive layer having a second index of refraction; and
(d) a second electrode disposed over the organic emissive layer;
(e) wherein the first index of refraction is higher than the second index of refraction; and
(f) further comprising a lens disposed on a side of the substrate opposite to the first electrode.
2. The device of claim 1 , wherein the first index of refraction is at least 0.14 greater than the second index of refraction.
3. The device of claim 1 , wherein the lens has a third index of refraction, and wherein the difference between the first index of refraction and the third index of refraction is less than 0.1.
4. The device of claim 1 , wherein the lens and the substrate are made of the same material and have the same index of refraction.
5. The device of claim 1 , wherein the first index of refraction is at least 1.85.
6. The device of claim 1 , wherein the second index of refraction is at least 1.8.
7. The device of claim 1 , wherein the device further comprises one or more additional organic layers disposed between the first electrode and the second electrode.
8. The device of claim 1 , wherein the coupling efficiency is 36% or greater.
9. The device of claim 1 , wherein the small molecule organic material includes a bulky substituent.
10. An organic light emitting device, comprising:
a substrate;
a first electrode disposed over the substrate, the first electrode having a thickness of at least 120 nm;
an organic emissive layer disposed over the first electrode, the organic emissive layer comprising a small molecule organic material including a bulky substituent; and
a second electrode disposed over the organic emissive layer;
wherein all of the organic layers in the device have a combined thickness of at least 140 nm; and
wherein the device has an external electroluminescent efficiency of at least 56%.
11. A device, comprising:
(a) a substrate having a first index of refraction, the first index of refraction being at most 1.51;
(b) a first electrode disposed over the substrate
(c) an organic emissive layer disposed over the first electrode, the organic emissive layer comprising a small molecule organic material, the organic emissive layer having a second index of refraction; and
(d) a second electrode disposed over the organic emissive layer;
(e) wherein the first index of refraction is higher than the second index of refraction.
12. The device of claim 11 , wherein the organic emissive layer comprises a first small molecule organic material, wherein the first small molecule organic material is an emissive material that includes a bulky substituent.
13. The device of claim 11 , wherein the organic emissive layer further comprises a second small molecule organic material, wherein the second small molecule organic material is a host material that includes a bulky substituent.
14. The device of claim 11 , wherein the organic emissive layer includes a bulky dopant.
15. The device of claim 11 , wherein the first index of refraction is at least 0.14 greater than the second index of refraction.
16. The device of claim 11 , wherein the substrate has a non-planar surface on a side of the substrate opposite to the first electrode.
17. The device of claim 16 , further comprising a lens disposed on the substrate, on a side of the substrate opposite to the first electrode.
18. The device of claim 17 , wherein the lens has a third index of refraction, and wherein the difference between the first index of refraction and the third index of refraction is less than 0.1.
19. The device of claim 17 , wherein the lens and the substrate are made of the same material and have the same index of refraction.
20. The device of claim 11 , wherein the device further comprises one or more additional organic layers disposed between the first electrode and the second electrode.
21. The device of claim 11 , wherein the coupling efficiency is 36% or greater.
22. An organic light emitting device, comprising:
a substrate;
a first electrode disposed over the substrate;
a small molecule organic emissive layer disposed over the first electrode, the organic emissive layer including a small molecule organic material including a bulky substituent;
a second electrode disposed over the organic emissive layer.
23. The device of claim 22 , wherein the small molecule organic material including the bulky substituent is a host.
24. The device of claim 22 , wherein the small molecule organic material including the bulky substituent is a dopant.
25. A device, comprising:
(a) a substrate having a first index of refraction;
(b) a first electrode disposed over the substrate;
(c) an organic emissive layer disposed over the first electrode, the organic emissive layer comprising a small molecule organic material, the organic emissive layer having a second index of refraction; and
(d) a second electrode disposed over the organic emissive layer;
(e) wherein the first index of refraction is higher than the second index of refraction; and
(f) further comprising a shaped element disposed on a side of the substrate opposite to the first electrode, and having a periodicity equal to that of the device.
26. The device of claim 25 , wherein the first index of refraction is at least 0.14 greater than the second index of refraction.
27. The device of claim 25 , wherein the first index of refraction is at least 1.85.
28. The device of claim 25 , wherein the second index of refraction is at least 1.8.
29. The device of claim 25 , wherein the device further comprises one or more additional organic layers disposed between the first electrode and the second electrode.
30. The device of claim 25 , wherein the coupling efficiency is 36% or greater.
31. The device of claim 25 , wherein the small molecule organic material includes a bulky substituent.