Optoelectronic device including ultrathin dopant layers

1. An organic electroluminescent device, comprising:

a first electrode;

a first neat host material layer positioned over the first electrode;

a second neat host material layer positioned over the first host material layer;

at least one ultrathin dopant layer positioned between the first and second host material layers, the at least one ultrathin dopant layer having a thickness of less than 2 Å, positioned at a distance of 20-200 nm from a bottom surface of the first host material layer or a top surface of the second host material layer; and

a second electrode positioned over the second host material layers.

2. The organic electroluminescent device of claim 1 , further comprising:

a third host material layer positioned between the second host material layer and the second electrode; and

at least one second ultrathin dopant layer positioned between the second and third host material layers.

3. The organic electroluminescent device of claim 1 , further comprising a hole transport layer positioned between the first electrode and the first host material layer.

4. The organic electroluminescent device of claim 1 , wherein the first host material layer has a thickness different from a thickness of the second host material layer.

5. The organic electroluminescent device of claim 1 , wherein the first or second host material layer comprises CBP.

6. The organic electroluminescent device of claim 1 , wherein the at least one ultrathin dopant layer comprises a first ultrathin dopant layer and a second ultrathin dopant layer.

7. The organic electroluminescent device of claim 6 , wherein the first ultrathin dopant layer and a second ultrathin dopant layer comprise different dopant materials.

8. The organic electroluminescent device of claim 6 , wherein the first ultrathin dopant layer is in contact with the second ultrathin dopant layer.

9. The organic electroluminescent device of claim 1 , wherein the first electrode is an anode and the anode is a transparent anode.

10. The organic electroluminescent device of claim 1 , wherein the at least one dopant layer has a thickness of less than 1 Å.

11. The organic electroluminescent device of claim 1 , further comprising a first emissive layer positioned over the first electrode, comprising an emissive layer host material and an emissive layer dopant material, wherein the emissive layer dopant material is different than a dopant in the at least one ultrathin dopant layer.

12. The organic electroluminescent device of claim 11 , wherein the first emissive layer is positioned between the first electrode and the first host material layer.

13. The organic electroluminescent device of claim 11 , wherein the emissive layer dopant material and the at least one ultrathin dopant layer are each independently selected from the group consisting of a red emissive layer, a blue emissive layer, and a green emissive layer.

14. The organic electroluminescent device of claim 1 , wherein the first host material layer has a thickness of between 3 nm and 4 nm.

15. The organic electroluminescent device of claim 1 , wherein the at least one ultrathin dopant layer is positioned at a distance of 20-50 nm from the bottom surface of the first host material layer or the top surface of the second host material layer.

16. An organic electroluminescent device, comprising:

a first electrode;

a first neat host material layer comprising a first host material positioned over the first electrode,

a light emitting layer positioned over the first host material; and

a second neat host material layer comprising a second host material positioned over the light emitting layer;

wherein the light emitting layer comprises:

n ultrathin dopant layers, each dopant layer having a thickness of at less than 2 Å and comprising a dopant material, wherein at least one of the ultrathin dopant layers is positioned at a distance of 20-50 nm from a bottom surface of the first host material layer; and

m additional host material layers, each additional host material layer comprising an additional host material;

wherein n is an integer of at least 1; and

wherein m=n−1 and when m>0, each additional host material layer is positioned between two ultrathin dopant layers.

17. The organic electroluminescent device of claim 16 , wherein n is at least 2 and at least one dopant material is different from at least one other dopant material.

18. The organic electroluminescent device of claim 16 , wherein n is at least 2, and each dopant material is the same.

19. An organic electroluminescent device, comprising:

a first electrode;

a second electrode positioned over the first electrode;

a neat layer of host material positioned between the first electrode and the second electrode, having a bottom surface facing the first electrode and a top surface facing the second electrode; and

a thin layer of dopant material positioned within the layer of host material, the layer of dopant material having a thickness of less than 2 Å, and positioned at a distance of 20-50 nm from the bottom surface of the layer of host material.

20. The organic electroluminescent device of claim 19 , further comprising a second thin layer of dopant material positioned within the layer of host material, the second layer of dopant material having a thickness of less than 2 Å and positioned at a distance of 20-50 nm from the top surface of the layer of host material.