Electroluminescent devices with organic transport layers

1. An electroluminescent device comprising:

a substrate;

a first electrode;

a hole transport layer;

an emission layer comprising luminescent nanostructures directly disposed on the hole transport layer, wherein the luminescent nanostructures directly contact the hole transport layer;

an electron transport layer comprising an organic layer, wherein a first portion of the organic layer of the electron transport layer is disposed on the emission layer and a second portion of the organic layer of the electron transport layer is directly disposed on the hole transport layer in the region where the hole transport layer, the emission layer and the electron transport layer are stacked, wherein the second portion of the organic layer of the electron transport layer is disposed within gaps between the hole transport layer and portions of the luminescent nanostructures, and wherein a composition of the first portion of the organic layer and a composition of the second portion of the organic layer are the same; and

a second electrode.

2. The electroluminescent device of claim 1 , wherein surfaces of the luminescent nanostructures are covered by the organic layer of the electron transport layer.

3. The electroluminescent device of claim 1 , wherein an organic material of the organic layer is soluble in a polar organic solvent.

4. The electroluminescent device of claim 1 , wherein an organic material of the organic layer is soluble in alcohol, acetone, or acetonitrile.

5. The electroluminescent device of claim 1 , wherein the organic layer comprises an organic material with two or more phosphonic oxide functional groups (P═O).

6. The electroluminescent device of claim 1 , wherein the organic layer comprises (1,3,5-Triazine-2,4,6-triyl) tris (benzene-3,1-diyl) tri s (diphenylphosphine oxide), or 2,4,6-Tris[3-(diphenylphosphinyl) phenyl]-1,3,5-triazine.

7. The electroluminescent device of claim 1 , wherein a turn-on voltage of the electroluminescent device ranges between about 0.7 V to about 1 V.

8. The electroluminescent device of claim 1 , wherein the luminescent nanostructures comprise indium phosphide (InP).

9. The electroluminescent device of claim 1 , wherein the luminescent nanostructures comprise quantum dots configured to emit light in a visible spectrum.

10. The electroluminescent device of claim 1 , wherein the luminescent nanostructures comprise a first population of quantum dots configured to emit red light and a second population of quantum dots configured to emit green light.

11. The electroluminescent device of claim 1 , wherein the second portion of the organic layer of the electron transport layer is directly disposed on the hole transport layer, and wherein the hole transport layer does not comprise the luminescent nanostructures.

12. The electroluminescent device of claim 1 , wherein area of direct contact between the electron transport layer and the hole transport layer is larger than area of direct contact between the emission layer and the hole transport layer.

13. A display device comprising:

an array of pixels; and

a display screen disposed on the array of pixels,

wherein each pixel of the array of pixel comprises first and second electroluminescent devices,

wherein each of the first and second electroluminescent devices comprises:

a hole transport layer,

an emission layer comprising luminescent nanostructures directly disposed on the hole transport layer, wherein the luminescent nanostructures directly contact the hole transport layer, and

an electron transport layer comprising an organic layer, wherein a first portion of the organic layer of the electron transport layer is disposed on the emission layer and a second portion of the organic layer of the electron transport layer is directly disposed on the hole transport layer in the region where the hole transport layer, the emission layer and the electron transport layer are stacked, wherein the second portion of the organic layer of the electron transport layer is disposed within gaps between adjacent the luminescent nanostructures, and wherein a composition of the first portion of the organic layer and a composition of the second portion of the organic layer are the same,

wherein the emission layer of the first electroluminescent device is configured to emit a first light having a first peak wavelength, and

wherein the emission layer of the second electroluminescent device is configured to emit a second light having a second peak wavelength that is different from the first peak wavelength.

14. The display device of claim 13 , wherein surfaces of the luminescent nanostructures are covered by the organic layer of the electron transport layer.

15. The display device of claim 13 , wherein the organic layer does not include an inorganic material.

16. The display device of claim 13 , wherein the organic layer comprises an organic material with two or more phosphonic oxide functional groups (P═O).

17. The display device of claim 13 , wherein the organic layer comprises (1,3,5-Triazine-2,4,6-triyl) tris (benzene-3,1-diyl) tris (diphenylphosphine oxide), or 2,4,6-Tris[3-(diphenylphosphinyl) phenyl]-1,3,5-triazine.

18. The display device of claim 13 , wherein the second portion of the organic layer of the electron transport layer is directly disposed on the hole transport layer, and wherein the hole transport layer does not comprise the luminescent nanostructures.

19. A method of fabricating an electroluminescent device, the method comprising:

providing a substrate with a layer of anode material;

forming a hole transport layer on the layer of anode material;

forming a layer of quantum dots on the hole transport layer, wherein the quantum dots directly contact the hole transport layer;

forming an electron transport layer comprising an organic layer on the layer of quantum dots using a solution process, wherein the organic layer comprises organic material and the solution process allows the organic material to diffuse through the layer of quantum dots to fill gaps between the quantum dots and directly contact the hole transport layer in the region where the hole transport layer, the layer of quantum dots, and the electron transport layer are stacked, wherein a portion of the organic layer of the electron transport layer is disposed within gaps between the hole transport layer and portions of the quantum dots, and wherein the organic material on the layer of quantum dots and the organic material directly contacting the hole transport layer are the same; and

forming a cathode on the electron transport layer.

20. The method of claim 19 , wherein the forming the electron transport layer comprises preparing a solution with the organic material in a polar organic solvent.

21. The method of claim 19 , wherein the forming the electron transport layer comprises preparing a solution with the organic material, the organic material comprising two or more phosphonic oxide functional groups (P═O).

22. The method of claim 19 , wherein the forming the electron transport layer comprises preparing a solution with (1,3,5-Triazine-2,4,6-triyl) tris (benzene-3,1-diyl) tris (diphenylphosphine oxide), 2,4,6-Tris[3-(diphenylphosphinyl) phenyl]-1,3,5-triazine, which has three phosphonic oxide functional groups (P═O).

23. The method of claim 19 , wherein the portion of the organic layer of the electron transport layer is directly disposed on the hole transport layer, and wherein the hole transport layer does not comprise the quantum dots.

24. The method of claim 19 , wherein forming the layer of quantum dots on the hole transport layer comprises forming the layer of quantum dots directly disposed on the hole transport layer; and wherein the solution process allows the organic material to cover surfaces of the quantum dots, wherein the organic material of the organic layer on the surfaces of quantum dots and the organic material directly contacting the hole transport layer are the same.