Organic light emitting device having multiple separate emissive layers

• US 8,143,613 B2
• Filed: 11/27/2007
• Issued: 03/27/2012
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: University of Michigan
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Forrest, Stephen R.
• Primary Examiner(s): Pert, Evan
• Assistant Examiner(s): Wilson, Scott R
• Application Number:
  US11/945,910
• Publication Number:
  US 20110215301A1
• Time in Patent Office: 1,582 Days
• Field of Search: 257/13, 257/76, 257/78, 257 79-103, 257/918, 257/40, 313/504
• US Class Current: 257/13
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light

Abstract

An organic light emitting device having multiple separate emissive layers is provided. Each emissive layer may define an exciton formation region, allowing exciton formation to occur across the entire emissive region. By aligning the energy levels of each emissive layer with the adjacent emissive layers, exciton formation in each layer may be improved. Devices incorporating multiple emissive layers with multiple exciton formation regions may exhibit improved performance, including internal quantum efficiencies of up to 100%.

Claims

1. A device comprising:

an anode;

a cathode; and

a stacked emissive region disposed between the anode and the cathode, the stacked emissive region comprising;

a first organic emissive layer comprising a first dopant and a first host;

a second organic emissive layer comprising a second dopant and a second host; and

a third organic emissive layer comprising a third dopant and a third host;

wherein;

the first host, second host, and third host are different from each other; and

the first organic emissive layer has an emission peak different from at least one of the second emissive layer and the third emissive layer.

2. The device of claim 1, wherein the HOMO of each host is aligned to the HOMO of an adjacent dopant.

3. The device of claim 2, wherein the HOMO of at least one host is within 5 kT-10 kT of the HOMO of an adjacent dopant.

4. The device of claim 3, wherein the LUMO of at least one host is within 5 kT-10 kT of the HOMO of an adjacent dopant.

5. The device of claim 3, wherein the LUMO of each host is within 5 kT-10 kT of the HOMO of an adjacent dopant.

6. The device of claim 2, wherein the HOMO of each host is within 5 kT-10 kT of the HOMO of an adjacent dopant.

7. The device of claim 2, wherein the first dopant, second dopant, and third dopant are different from each other.

8. The device of claim 1, wherein the LUMO of each host is aligned to the LUMO of an adjacent dopant.

9. The device of claim 1, wherein:

the HOMO of the second dopant is between the HOMO of the first host and the HOMO of the first dopant; and

the HOMO of the second dopant is aligned to the HOMO of the first host and to the HOMO of the first dopant.

10. The device of claim 1, wherein:

the LUMO of the second host is between the LUMO of the first host and the LUMO of the first dopant; and

the LUMO of the second host is aligned to the LUMO of the first host and to the LUMO of the first dopant.

11. The device of claim 1, wherein, for each emissive layer, the HOMO of the host is aligned to the HOMO of each adjacent emissive layer host and to the HOMO of each adjacent emissive layer dopant.

12. The device of claim 1, wherein, for each emissive layer, the LUMO of the host is aligned to the LUMO of each adjacent emissive layer host and to the LUMO of each adjacent emissive layer dopant.

13. The device of claim 1, wherein at least one of the dopants is a phosphorescent dopant.

14. The device of claim 1, wherein at least one of the dopants is a fluorescent dopant.

15. The device of claim 1, wherein a combined emission of the organic emissive layers sufficiently spans the visible spectrum to produce white light.

16. The device of claim 15, wherein the white light has a CRI of at least about 80.

17. The device of claim 15, wherein the white light has CRE coordinates in the range (0.33±

0.05, 0.33±

0.05).

18. The device of claim 1, wherein at least one organic emissive layer comprises a non-polymeric material.

19. The device of claim 1, wherein at least one organic emissive layer comprises a polymer.

20. The device of claim 1, wherein each of the organic emissive layers defines an exciton formation region.

21. An organic optoelectronic device, comprising:

a first organic emissive layer comprising a first host and a first dopant adapted to emit light having a first spectrum;

a second organic emissive layer comprising a second host and a second dopant adapted to emit light having a second spectrum, the second host having a LUMO between and aligned to the LUMO of the first host and the LUMO of the first dopant; and

a third organic emissive layer comprising a third host and a third dopant adapted to emit light having a third spectrum, the third host having a LUMO between and aligned to the LUMO of the second host and the LUMO of the second dopant.

22. The device of claim 21, wherein a combined emission of the emissive layers sufficiently spans the visible spectrum to produce white light.

23. The device of claim 21, wherein:

the second host has a HOMO between and aligned to the HOMO of the first host and the HOMO of the first dopant; and

the third host has a HOMO between and aligned to the HOMO of the second host and the HOMO of the second dopant.

24. The device of claim 21, wherein the first host, second host, and third host are different from each other.

25. A method of fabricating an optoelectronic device, comprising:

obtaining a substrate;

depositing a first electrode over the substrate;

depositing a first doped organic emissive layer comprising a first dopant and a first host over the first electrode;

depositing a second doped organic emissive layer comprising a second dopant and a second host over the first emissive layer;

depositing a third doped organic emissive layer comprising a third dopant and a third host over the second emissive layer; and

depositing a second electrode over the third emissive layer;

wherein the first host, second host, and third host are different from each other.

26. The method of claim 25, wherein a combined emission of the emissive layers sufficiently spans the visible spectrum to produce white light.

27. The method of claim 25, wherein each emissive layer host has an energy level aligned to a corresponding energy level of a dopant in an adjacent emissive layer.

28. The method of claim 27, wherein the first dopant, second dopant, and third dopant are different from each other.

29. The method of claim 25, wherein each of the organic emissive layers defines an exciton formation region.