Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

• US 7,579,773 B2
• Filed: 06/05/2006
• Issued: 08/25/2009
• Est. Priority Date: 06/05/2006
• Status: Active Grant

• Current Assignee: The Trustees of Princeton University (Princeton University)
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Forrest, Stephen, Kanno, Hiroshi
• Primary Examiner(s): Patel; Vip
• Application Number:
  US11/447,473
• Publication Number:
  US 20070278937A1
• Time in Patent Office: 1,177 Days
• Field of Search: 313/504, 313/506, 313/509
• US Class Current: 313/504
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/131 with spacer layers between the electroluminescent layers
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• 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 85/653 comprising only oxygen as heteroatom
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons

Abstract

The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

Claims

1. An organic light emitting device comprising:

a cathode,

an emissive region, and

an anode

wherein,

the emissive region comprises a fluorescent layer comprising a first fluorescent emitting material as a dopant in a host material;

a phosphorescent-sensitized fluorescent layer comprising a second fluorescent emitting material and a phosphorescent emitting material as dopants in a host material; and

a spacer layer between the fluorescent layer and the phosphorescent-sensitized fluorescent layer.

2. The device of claim 1, wherein the host material for the fluorescent layer, the host material for the phosphorescent-sensitized layer and the spacer layer are comprised of the same material.

3. The device of claim 2, wherein the host material for the fluorescent layer, the host material for the phosphorescent-sensitized layer and the spacer layer are comprised of CBP.

4. The device of claim 1, wherein the first fluorescent emitting material is a blue emitting fluorescent material.

5. The device of claim 4, wherein the fluorescent emitting material is BCzVBi.

6. The device of claim 1, wherein the first fluorescent emitting material is a blue emitting material, the second fluorescent emitting material is a red emitting material and the phosphorescent emitting material is a green emitting material.

7. The device of claim 1, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration such that the there is partial transfer of triplet excitons from the phosphorescent emitting material to the second fluorescent emitting material.

8. The device of claim 1, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration of less than about 0.5%.

9. The device of claim 8, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration of less than about 0.1%.

10. The device of claim 1, wherein essentially all singlet excitons are utilized by the fluorescent layer and essentially all triplet excitons are utilized by the phosphorescent-sensitized fluorescent layer.

11. An organic light emitting device comprising:

a cathode,

an emissive region comprising the following layers in sequence

a fluorescent layer comprising a first fluorescent emitting material as a dopant in a host material;

an optional spacer layer;

a phosphorescent-sensitized fluorescent layer comprising a second fluorescent emitting material and a phosphorescent emitting material as dopants in a host material;

an optional spacer layer; and

a fluorescent layer comprising the first fluorescent emitting material as a dopant in a host material; and

an anode.

12. The device of claim 11, wherein the emissive region comprising the following layers in sequence:

the fluorescent layer, the spacer layer;

the phosphorescent-sensitized fluorescent layer;

the spacer layer; and

the fluorescent layer.

13. The device of claim 11, wherein the host material for the fluorescent layers, the host material for the phosphorescent-sensitized layer and the spacer layers are comprised of the same material.

14. The device of claim 13, wherein the host material for the fluorescent layer, the host material for the phosphorescent-sensitized layer and the spacer layer are comprised of CBP.

15. The device of claim 11, wherein the first fluorescent emitting material is a blue emitting fluorescent material.

16. The device of claim 15, wherein the fluorescent emitting material is BCzVBi.

17. The device of claim 11, wherein the first fluorescent emitting material is a blue emitting material, the second fluorescent emitting material is a red emitting material and the phosphorescent emitting material is a green emitting material.

18. The device of claim 11, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration such that the there is partial transfer of triplet excitons from the phosphorescent emitting material to the second fluorescent emitting material.

19. The device of claim 11, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration of less than about 0.5%.

20. The device of claim 19, wherein the second fluorescent emitting material is present in the phosphorescent-sensitized fluorescent layer at a concentration of less than about 0.1%.

21. The device of claim 11, wherein essentially all singlet excitons are utilized by the fluorescent layers and essentially all triplet excitons are utilized by the phosphorescent-sensitized fluorescent layer.