High efficiency and brightness fluorescent organic light emitting diode by triplet-triplet fusion

• US 8,952,362 B2
• Filed: 08/31/2012
• Issued: 02/10/2015
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Forrest, Stephen, Zhang, Yifan
• Primary Examiner(s): Nguyen, Thanh T
• Application Number:
  US13/600,651
• Publication Number:
  US 20140061594A1
• Time in Patent Office: 893 Days
• Field of Search: 257/40, 257/144
• US Class Current: 257/40
• CPC Class Codes: H10K 2101/00 Properties of the organic materials covered by group H10K85/00
• CPC Class Codes: H10K 2101/20 Delayed fluorescence emission
• CPC Class Codes: H10K 2101/60 Up-conversion, e.g. by triplet-triplet annihilation
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers

Abstract

A first device is provided. The first device further comprises an organic light emitting device. The organic light emitting device further comprises an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer may include an organic host compound and at least one organic emitting compound capable of fluorescent emission at room temperature. Various configurations are described for providing a range of current densities in which T-T fusion dominates over S-T annihilation, leading to very high efficiency fluorescent OLEDs.

Claims

1. An organic light emitting device, comprising:

an anode;

a cathode; and

an emissive layer disposed between the anode and the cathode, the emissive layer including an organic host compound and at least one fluorescent organic emitting compound capable of fluorescent emission at room temperature and generates both radiative singlet excitons and non-radiative triplet excitons as a result of electron-hole recombination;

wherein;

the overlap between the singlet emission spectrum of the fluorescent organic emitting compound and the triplet absorption spectrum of the host compound is less than 20 percent;

wherein the host compound has a triplet energy and a singlet energy; and

wherein twice the host compound triplet energy plus 0.3 eV is greater than the host compound singlet energy and twice the host compound triplet energy minus 0.5 eV is less than the host compound singlet energy.

2. The device of claim 1, wherein the exciton diffusion length is at least greater than half the thickness of the emissive layer.

3. The device of claim 1, wherein the emissive layer has a thickness of about of about 100 nm to about 10 nm.

4. The device of claim 3, wherein the emissive layer has a thickness of about 75 nm to about 25 nm.

5. The device of claim 4, wherein the emissive layer has a thickness of about 50 nm to about 25 nm.

6. The device of claim 1, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 50%.

7. The device of claim 1, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 60%.

8. The device of claim 1, wherein the emissive layer includes tetraphenyldibenzoperiflanthene doped in rubrene.

9. The device of claim 8, wherein the tetraphenyldibenzoperiflanthene is doped at 1 vol %.

10. The device of claim 1, wherein the emissive layer includes a dopant selected from the group consisting of:

anthracene, tetracene, rubrene, and perylene and their derivatives.

11. The device of claim 1, wherein the emissive layer includes a host selected from the group consisting of:

anthracene, tetracene, rubrene, and perylene and their derivatives.

12. The device of claim 1, wherein the device is a consumer product.

13. An organic light emitting device, comprising:

an anode;

a cathode; and

an emissive layer disposed between the anode and the cathode, the emissive layer including an organic host compound and at least one fluorescent organic emitting compound capable of fluorescent emission at room temperature and generates both radiative singlet excitons and non-radiative triplet excitons as a result of electron-hole recombination;

wherein;

the overlap between the singlet emission spectrum of the fluorescent organic emitting compound and the triplet absorption spectrum of the host compound is less than 20 percent;

wherein the at least one fluorescent organic compound has a triplet energy and a singlet energy; and

wherein twice the triplet energy of the at least one fluorescent organic emitting compound plus 0.3 eV is greater than the singlet energy of the at least one fluorescent organic emitting compound and twice the at least one fluorescent organic emitting compound triplet energy minus 0.5 eV is less than the at least one fluorescent organic emitting compound singlet energy.

14. The device of claim 13, wherein the emissive layer has a thickness of about of about 100 nm to about 10 nm.

15. The device of claim 14, wherein the emissive layer has a thickness of about 75 nm to about 25 nm.

16. The device of claim 14, wherein the emissive layer has a thickness of about 50 nm to about 25 nm.

17. The device of claim 13, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 50%.

18. The device of claim 13, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 60%.

19. The device of claim 13, wherein the emissive layer includes a dopant selected from the group consisting of:

anthracene, tetracene, rubrene, and perylene and their derivatives.

20. The device of claim 13, wherein the emissive layer includes a host selected from the group consisting of:

anthracene, tetracene, rubrene, and perylene and their derivatives.

21. The device of claim 13, wherein the device is a consumer product.

22. An organic light emitting device, comprising:

an anode;

a cathode; and

an emissive layer disposed between the anode and the cathode, the emissive layer consisting essentially of one type of fluorescent molecule having a triplet energy and a singlet energy, and generates both radiative singlet excitons and non-radiative triplet excitons as a result of electron-hole recombination;

wherein;

twice the triplet energy of the fluorescent molecule plus 0.3 eV is greater than the singlet energy of the molecule.

23. The device of claim 22, wherein the emissive layer has a thickness of about of about 100 nm to about 10 nm.

24. The device of claim 23, wherein the emissive layer has a thickness of about 75 nm to about 25 nm.

25. The device of claim 23, wherein the emissive layer has a thickness of about 50 nm to about 25 nm.

26. The device of claim 22, wherein the emissive molecule is selected from the group consisting of:

anthracene, tetracene, rubrene, and perylene and their derivatives.

27. The device of claim 22, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 50%.

28. The device of claim 22, wherein the electroluminescent internal quantum efficiency of the emitter is greater than 60%.

29. The device of claim 22, wherein the device is a consumer product.