Top-emitting white organic light-emitting diodes having improved efficiency and stability

1. An emissive construct comprising:

a second fluorescent blue emissive layer comprising a second fluorescent emitter having a second T1, wherein T1 is the energy of the lowest energy triplet state;

a first fluorescent blue emissive layer contacting the second fluorescent emissive layer, said first fluorescent blue emissive layer comprising a first fluorescent emitter having a first T1, said second T1 less than said first T1;

a blocking layer comprising hole blocking material having a third T1, said third T1 higher than or equal to said first T1;

a first phosphorescent emissive layer contacting said blocking layer; and

a second phosphorescent emissive layer contacting said first phosphorescent emissive layer;

wherein the first phosphorescent emissive layer has a fourth T1 and the second phosphorescent emissive layer has a fifth T1, and wherein the first T1 is greater than the fourth T1 and the fifth T1.

2. The emissive construct of claim 1 , which is configured to allow triplet excitons to be transferred from the first fluorescent emissive layer to the second fluorescent emissive layer.

3. The emissive construct of claim 1 , wherein the first phosphorescent emissive layer contacts the second phosphorescent emissive layer.

4. The emissive construct of claim 1 , wherein the first phosphorescent emissive layer contacts the blocking layer.

5. The emissive construct of claim 1 , which is configured to allow triplet excitons to be transferred from the blocking layer to the first fluorescent emissive layer.

6. The emissive construct of claim 1 , which is configured to allow triplet excitons to be transferred from the blocking layer to the first phosphorescent emissive layer.

7. The emissive construct of claim 1 , wherein the second fluorescent emissive layer, the first fluorescent emissive layer, the first phosphorescent emissive layer, and the second phosphorescent emissive layer comprise a host material.

8. The emissive construct of claim 7 , wherein the second fluorescent emissive layer, the first fluorescent emissive layer, the first phosphorescent emissive layer, and the second phosphorescent emissive layer have the same host material.

9. The emissive construct of claim 8 , wherein the host material is

10. The emissive construct of claim 1 , wherein the first phosphorescent emissive layer has a fourth T1 and the second phosphorescent emissive layer has a fifth T1, and wherein the first T1 is less than the fourth T1 and the fifth T1.

11. The emissive construct of claim 1 , wherein the first and the second phosphorescent emissive layers emit at wavelengths that are complementary to the blue emissive layer emissive wavelengths to generate a perceived white light with the blue emissive layer.

12. The emissive construct of claim 1 , wherein the first phosphorescent emissive layer comprises a dopant that is a phosphorescent red emitter.

13. The emissive construct of claim 12 , wherein the dopant is

14. The emissive construct of claim 1 , wherein the second phosphorescent emissive layer comprises dopant that is a phosphorescent yellow emitter.

15. The emissive construct of claim 14 , wherein the phosphorescent yellow emitter is

16. The emissive construct of claim 1 , wherein the hole blocking material is 1,3,5-tris[2-N-phenylbenzimidazole-2-yl]benzene.

17. An emissive construct comprising:

a second fluorescent emissive layer comprising a second fluorescent emitter having a second T1;

a first fluorescent emissive layer disposed over the second fluorescent emissive layer, said first fluorescent emissive layer comprising a first fluorescent emitter having a first T1;

wherein the second T1 is less than the first T1;

wherein the emissive construct is configured to allow holes to be transferred from the second fluorescent emissive layer to the first fluorescent emissive layer;

a blocking layer comprising hole blocking material having a third T1, and disposed over the first fluorescent emissive layer;

wherein the third T1 is higher than or equal to said first T1;

a first phosphorescent emissive layer disposed over the blocking layer;

wherein the emissive construct is configured to allow electrons to be transferred from the first phosphorescent emissive layer to the blocking layer; and

a second phosphorescent emissive layer disposed over said first phosphorescent emissive layer;

wherein the emissive construct is configured to allow electrons to be transferred from the second phosphorescent emissive layer to the first phosphorescent emissive layer;

wherein the first phosphorescent emissive layer has a fourth T1 and the second phosphorescent emissive layer has a fifth T1, and wherein the first T1 is greater than the fourth T1 and the fifth T1.

18. The emissive construct of claim 17 , wherein the second fluorescent emissive layer contacts the first fluorescent emissive layer.

19. An emissive construct comprising:

a second fluorescent emissive layer comprising a second fluorescent emitter having a second T1;

a first fluorescent emissive layer disposed over the second fluorescent emissive layer, said first fluorescent emissive layer comprising a first fluorescent emitter having a first T1;

wherein the second T1 is less than the first T1;

wherein the emissive construct is configured to allow holes to be transferred from the second fluorescent emissive layer to the first fluorescent emissive layer;

a blocking layer comprising hole blocking material having a third T1, and disposed over the first fluorescent emissive layer;

wherein the third T1 is higher than or equal to said first T1; and

a first phosphorescent emissive layer disposed over the blocking layer;

wherein the emissive construct is configured to allow electrons to be transferred from the first phosphorescent emissive layer to the blocking layer;

wherein the first phosphorescent emissive layer has a fourth T1 and the second phosphorescent emissive layer has a fifth T1, and wherein the first T1 is greater than the fourth T1 and the fifth T1.