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