Increased emission efficiency in organic light-emitting devices on high-index substrates

• US 20040007969A1
• Filed: 11/27/2002
• Published: 01/15/2004
• Est. Priority Date: 11/29/2001
• Status: Active Grant

• Current Assignee: The Trustees of Princeton University (Princeton University), Universal Display Corporation
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Kwong, Raymond, Madigan, Conor Francis, Lu, Min-Hao Michael, Sturm, James C.
• Granted Patent: US 7,053,547 B2
• Time in Patent Office: Days
• US Class Current: 313/501
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/80 Constructional details
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses

Abstract

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.

Claims

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 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.

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 substrate has a non-planar surface on a side of the substrate opposite to the first electrode.

4. The device of claim 3, further comprising a lens attached to the substrate, on a side of the substrate opposite to the first electrode.

5. The device of claim 3, further comprising a shaped element attached to the substrate and having a periodicity equal to that of the device.

6. The device of claim 4, 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.

7. The device of claim 4, wherein the lens and the substrate are made of the same material and have the same index of refraction.

8. The device of claim 1, wherein the first index of refraction is at least 1.85.

9. The device of claim 1, wherein the second index of refraction is at least 1.8.

10. 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.

11. The device of claim 1, wherein the coupling efficiency is 36% or greater.

12. 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; 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%.

13. 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 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.

14. The device of claim 13, 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.

15. The device of claim 13, 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.

16. The device of claim 13, wherein the organic emissive layer includes a bulky dopant.

17. The device of claim 13, wherein the first index of refraction is at least 0.14 greater than the second index of refraction.

18. The device of claim 13, wherein the substrate has a non-planar surface on a side of the substrate opposite to the first electrode.

19. The device of claim 18, further comprising a lens attached to the substrate, on a side of the substrate opposite to the first electrode.

20. The device of claim 19, 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.

21. The device of claim 19, wherein the lens and the substrate are made of the same material and have the same index of refraction.

22. The device of claim 13, wherein the device further comprises one or more additional organic layers disposed between the first electrode and the second electrode.

23. The device of claim 13, wherein the coupling efficiency is 36% or greater.

24. 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 material including a bulky substituent or a bulky dopant.

a second electrode disposed over the organic emissive layer.