Quantum dot light emitting device with electron auxiliary layer and display device including the same

Patent metadata

Field	Value
Publication number	US-11659725-B2
Application number	US-202016921188-A
Country	US
Kind code	B2
Filing date	Jul 6, 2020
Priority date	Jul 5, 2019
Publication date	May 23, 2023
Grant date	May 23, 2023

Abstract

A light emitting device includes: a first electrode and a second electrode with a surface facing the first electrode; an emission layer disposed between the first electrode and the second electrode and including a quantum dot (e.g., a plurality of quantum dots); and an electron auxiliary layer disposed between the emission layer and the second electrode. The electron auxiliary layer includes a first layer including a first metal oxide, and a second layer disposed on the first layer and including a second metal oxide. A roughness of an interface between the second layer and the second electrode is less than about 10 nm as determined by an electron microscopy analysis. An absolute value of a difference between a conduction band edge energy level of the second layer and a work function of the second electrode may be less than or equal to about 0.5 eV, and a conduction band edge energy level of the first layer may be less than the conduction band edge energy level of the second layer.

First claim

What is claimed is:

1. A light emitting device, comprising:
a first electrode and a second electrode with a surface facing the first electrode;
an emission layer disposed between the first electrode and the second electrode and comprising a quantum dot; and
an electron auxiliary layer disposed between the emission layer and the second electrode,
wherein the electron auxiliary layer comprises a first layer proximate to the emission layer and comprising a plurality of nanoparticles comprising a first metal oxide, and a second layer disposed on the first layer and proximate to the second electrode, the second layer comprising a second metal oxide,
wherein an interface roughness between the second layer and the surface of the second electrode is less than about 10 nanometers as determined by an electron microscopy analysis,
wherein the first metal oxide is represented by Chemical Formula 1:
Zn 1−x M x O  Chemical Formula 1

in the above formula, M is Mg, Ca, Zr, W, Li, Ti, Y, Al, or a combination thereof, and x is greater than 0 and less than or equal to 0.5, and
wherein the second layer does not include a metal oxide nanoparticle.

2. The light emitting device of claim 1 , wherein the emission layer does not comprise cadmium.

3. The light emitting device of claim 1 , wherein an amount of carbon in the first layer is greater than an amount of carbon in the second layer.

4. The light emitting device of claim 1 , wherein an amount of carbon in the first layer is greater than about 6 mole percent based on a total mole amount of elements in the first layer.

5. The light emitting device of claim 1 , wherein the first metal oxide has a composition different from the second metal oxide.

6. The light emitting device of claim 1 , wherein the first metal oxide and the second metal oxide comprises zinc, and a presence density of zinc in the second layer is greater than a presence density of zinc in the first layer.

7. The light emitting device of claim 1 , wherein the second metal oxide comprises a zinc oxide, a zinc magnesium oxide, a tin oxide, a titanium oxide, or a combination thereof.

8. The light emitting device of claim 1 , wherein the second metal oxide is represented by Chemical Formula 1:
Zn 1−x M x O  Chemical Formula 1

in the above formula, M is Mg, Ca, Zr, W, Li, Ti, Y, Al, or a combination thereof, and x is greater than or equal to 0 and less than or equal to 0.5.

9. The light emitting device of claim 1 , wherein the second layer comprises a vapor deposited film of the second metal oxide.

10. The light emitting device of claim 9 , wherein an average particle size of the nanoparticles of the first metal oxide is greater than or equal to about 1 nanometer and less than or equal to about 10 nanometers.

11. The light emitting device of claim 1 , wherein a surface of the second layer is disposed directly on a surface of the first layer.

12. The light emitting device of claim 11 , wherein an interface roughness between the surface of the second layer and a surface of the first layer is less than or equal to about 12 nanometers as determined by an electron microscopy.

13. The light emitting device of claim 1 , wherein an interface roughness between the second layer and the surface of the second electrode is less than or equal to about 5 nanometers.

14. The light emitting device of claim 1 , wherein a thickness of the second layer is greater than or equal to about 1 nanometer and less than or equal to about 20 nanometers.

15. The light emitting device of claim 1 , wherein an absolute value of a difference between a conduction band edge energy level of the second layer and a work function of the second electrode is less than or equal to about 0.5 electron volts or
wherein a conduction band edge energy level of the first layer is less than the conduction band edge energy level of the second layer and a difference between the conduction band edge energy level of the first layer and the conduction band edge energy level of the second layer is greater than or equal to about 0.05 electron volts.

16. The light emitting device of claim 1 , wherein the light emitting device further comprises a buffer layer disposed on an opposite surface of the second electrode, and the buffer layer comprises an organic metal compound, a metal fluoride, or a combination thereof.

17. The light emitting device of claim 16 , wherein a metal of the organic metal compound or the metal fluoride comprises lithium, aluminum, or a combination thereof;
and an organic moiety of the organic metal compound comprises an aromatic cyclic moiety, a heteroaromatic cyclic moiety, or a combination thereof.

18. The light emitting device of claim 1 , wherein the light emitting device further comprises an organic polymer layer disposed on an opposite surface of the second electrode.

19. The light emitting device of claim 18 , wherein the organic polymer layer comprises a polymerization product of a monomer combination comprising a compound having at least one carbon-carbon double bond, and optionally a thiol compound.

20. The light emitting device of claim 1 , wherein the light emitting device emits blue light, and a T50 of the light emitting device is greater than or equal to about 10 hours.

21. A display device comprising the light emitting device of claim 1 .

Assignees

• Samsung Electronics Co Ltd

Inventors

• Lee Heejae
• Kim Sung Woo
• Jang Eun Joo
• Chung Dae Young
• Han Moon Gyu

Classifications

• H10K50/844

  Encapsulations · CPC title

• H10K50/115 Primary

  comprising active inorganic nanostructures, e.g. luminescent quantum dots · CPC title

• H10K50/11 Primary

  characterised by the electroluminescent [EL] layers · CPC title

• H10K50/171

  Electron injection layers · CPC title

• H10K30/865

  Intermediate layers comprising a mixture of materials of the adjoining active layers · CPC title