Electron impeding layer for high efficiency phosphorescent OLEDs

• US 20070075631A1
• Filed: 10/04/2005
• Published: 04/05/2007
• Est. Priority Date: 10/04/2005
• Status: Active Grant

• Current Assignee: Universal Display Corporation
• Original Assignee: Universal Display Corporation
• Inventors: D'Andrade, Brian, Esler, James, Weaver, Michael, Tung, Yeh
• Granted Patent: US 8,148,891 B2
• Time in Patent Office: Days
• US Class Current: 313/504
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/18 Carrier blocking layers
• CPC Class Codes: H10K 85/311 Phthalocyanine
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

The present invention relates to OLEDs comprising an electron impeding layer between the cathode and the emissive layer. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.

Claims

1. An organic light emitting device, comprising:

a) an anode;

b) a hole transport layer;

c) an organic emissive layer comprising an emissive layer host and an emissive dopant;

d) an electron impeding layer;

e) an electron transport layer; and

f) a cathode

disposed, in that order, over a substrate.

2. The device of claim 1, wherein the HOMO of the emissive layer host is at least about 0.5 eV lower than the HOMO of the emissive dopant.

3. The device of claim 2, wherein the HOMO of the emissive layer host is about 0.5 eV to about 0.8 eV lower than the HOMO of the emissive dopant.

4. The device of claim 1, wherein the emissive dopant has a HOMO that is about −

5 eV or higher.

5. The device of claim 4, wherein the emissive dopant is selected from the group consisting of compounds 1-5.

6. The device of claim 5, wherein the emissive dopant is compound 1.

7. The device of claim 1, wherein the electron impeding layer consists essentially of a material having a hole mobility greater than its electron mobility.

8. The device of claim 7, wherein the electron impeding layer consists essentially of a material selected from the group consisting of TCTA, Irppz, NPD, TPD, mCP, and derivatives thereof.

9. The device of claim 1, wherein the electron impeding layer consists essentially of an ambipolar material.

10. The device of claim 9, wherein the ambipolar material is mCBP.

11. The device of claim 1, wherein the electron impeding layer consists essentially of the same material as the emissive layer host.

12. The device of claim 1, wherein the electron impeding layer is a neat layer.

13. The device of claim 1, wherein the electron impeding layer has a thickness of about 20 Å

to about 75 Å

.

14. The device of claim 13, wherein the electron impeding layer has a thickness of about 50 Å

.

15. The device of claim 1, wherein the HOMO of the electron impeding layer material is at least about 0.5 lower than the HOMO of the emissive dopant.

16. The device of claim 1, wherein the band gap of the electron impeding layer material is larger than the band gap of the emissive dopant.

17. The device of claim 1, wherein the emissive dopant has a peak in the emission spectra that is less than about 500 nm.

18. The device of claim 1, wherein the organic emissive layer emits light with CIE coordinates of (X≦

0.2, Y≦

0.3).

19. The device of claim 1, wherein the device is used in an active-matrix organic light emitting device display.

20. The device of claim 1, wherein the device exhibits increased efficiency relative to an otherwise equivalent device wherein the electron impeding layer is replaced with an electron transport layer.

21. The device of claim 20, wherein the device exhibits increased efficiency, increased voltage, and a lifetime that is the same or better relative to an otherwise equivalent device wherein the electron impeding layer is replaced with an electron transport layer.

22. The device of claim 1, wherein the unmodified external quantum efficiency is greater than about 5%.

23. An organic light emitting device comprising:

a) an anode;

b) a cathode;

c) an organic emissive layer disposed between the anode and the cathode, the organic emissive layer comprising an emissive layer host and an emissive dopant, wherein the HOMO of the emissive layer host is at least about 0.5 eV lower than the HOMO of the emissive dopant;

d) a first organic layer disposed between the organic emissive layer and the cathode;

e) a second organic layer disposed between, and in direct contact with, the organic emissive layer and the first organic layer;

wherein the second organic layer consists essentially of a hole transporting material or an ambipolar material.

24. The device of claim 23, wherein the HOMO of the emissive layer host is about 0.5 eV to about 0.8 eV lower than the HOMO of the emissive dopant.

25. The device of claim 23, wherein the emissive dopant has a HOMO that is about −

5 eV or higher.

26. The device of claim 25, wherein the emissive dopant is selected from the group consisting of compounds 1-5.

27. The device of claim 26, wherein the emissive dopant is compound 1.

28. The device of claim 23, wherein the second organic layer consists essentially of a material having a hole mobility greater than its electron mobility.

29. The device of claim 28, wherein the second organic layer consists essentially of a material selected from the group consisting of TCTA, Irppz, NPD, TPD, mCP, and derivatives thereof.

30. The device of claim 23, wherein the second organic layer consists essentially of an ambipolar material.

31. The device of claim 30, wherein the ambipolar material is mCBP.

32. The device of claim 23, wherein the second organic layer consists essentially of the same material as the emissive layer host.

33. The device of claim 23, wherein the second organic layer is a neat layer.

34. The device of claim 23, wherein the second organic layer has a thickness of about 20 Å

to about 75 Å

.

35. The device of claim 34, wherein the second organic layer has a thickness of about 50 Å

.

36. The device of claim 23, wherein the HOMO of the second organic layer material is at least about 0.5 lower than the HOMO of the emissive dopant.

37. The device of claim 23, wherein the band gap of the second organic layer material is larger than the band gap of the emissive dopant.

38. The device of claim 23, wherein the emissive dopant has a peak in the emission spectra that is less than about 500 nm.

39. The device of claim 23, wherein the organic emissive layer emits light with CIE coordinates of (X≦

0.2, Y≦

0.3).

40. The device of claim 23, wherein the device is used in an active-matrix organic light emitting device display.

41. The device of claim 23, wherein the device exhibits increased efficiency relative to an otherwise equivalent device wherein the second organic layer consists essentially of an electron transporting material.

42. The device of claim 41, wherein the device exhibits increased efficiency, increased voltage, and a lifetime that is the same or better relative to an otherwise equivalent device wherein the second organic layer consists essentially of an electron transporting material.

43. The device of claim 23, wherein the unmodified external quantum efficiency is greater than about 5%.

44. An organic light emitting device comprising:

a) an anode;

b) a cathode;

c) an organic emissive layer disposed between the anode and the cathode, the organic emissive layer comprising an emissive layer host and an emissive dopant, wherein the HOMO of the emissive layer host is at least about 0.5 eV lower than the HOMO of the emissive dopant;

d) a first organic layer disposed between the organic emissive layer and the cathode;

e) a second organic layer disposed between, and in direct contact with, the organic emissive layer and the first organic layer;

wherein the second organic layer has a relative electron mobility not more than 0.001 of the electron mobility of Bphen.

45. The device of claim 44, wherein the second organic layer has a relative electron mobility not more than 0.0005 of the electron mobility of Bphen.

46. The device of claim 45, wherein the second organic layer has a relative electron mobility not more than 0.0001 of the electron mobility of Bphen.

47. The device of claim 44, wherein the second organic layer consists essentially of a material, such that when said material is used in a device of claim 44 wherein the first organic layer is Alq₃, increasing the thickness of the second organic layer will cause emission from the first organic layer.

48. An organic light emitting device comprising:

a) an anode;

b) a cathode;

c) an organic emissive layer disposed between the anode and the cathode, the organic emissive layer comprising an emissive layer host and an emissive dopant, wherein the HOMO of the emissive layer host is at least about 0.5 eV lower than the HOMO of the emissive dopant; and

d) a means for accumulating electrons between the cathode and the emissive layer.