Light-emitting element, light-emitting device

Patent metadata

Field	Value
Publication number	US-12289936-B2
Application number	US-201917760556-A
Country	US
Kind code	B2
Filing date	Sep 30, 2019
Priority date	Sep 30, 2019
Publication date	Apr 29, 2025
Grant date	Apr 29, 2025

Abstract

A light-emitting element includes a first light-emitting layer including a first quantum dot and a second light-emitting layer including a second quantum dot provided between the cathode electrode and an anode electrode in order from the cathode electrode, the first quantum dot has a core-shell structure including a first core and a first shell, the second quantum dot has a core-shell structure including a second core and a second shell, and an energy level at a lower end of a conduction band of the first core is higher than an energy level at a lower end of a conduction band of the second core.

First claim

The invention claimed is:

1. A light-emitting element comprising:
a cathode electrode;
an anode electrode; and
a first light-emitting layer including a first quantum dot and a second light-emitting layer including a second quantum dot provided between the cathode electrode and the anode electrode in this order from the cathode electrode,
wherein the first quantum dot has a core-shell structure including at least a first core and a first shell, and the second quantum dot has a core-shell structure including at least a second core and a second shell,
a level at a lower end of a conduction band of the first core is higher than a level at a lower end of a conduction band of the second core, and
the first light-emitting layer and the second light-emitting layer are in direct contact with each other.

2. The light-emitting element according to claim 1 ,
wherein a level at an upper end of a valence band of the first core is higher than a level at an upper end of a valence band of the second core.

3. The light-emitting element according to claim 1 ,
wherein the first shell is an outermost shell of the first quantum dot, and the second shell is an outermost shell of the second quantum dot, and
a level at a lower end of a conduction band of the first shell is lower than a level at a lower end of a conduction band of the second shell.

4. The light-emitting element according to claim 3 ,
wherein a level at an upper end of a valence band of the first shell is lower than a level at an upper end of a valence band of the second shell.

5. The light-emitting element according to claim 1 ,
wherein a wavelength of light from the first light-emitting layer and a wavelength of light from the second light-emitting layer are substantially identical.

6. The light-emitting element according to claim 1 ,
wherein a wavelength of light from the first light-emitting layer is longer than a wavelength of light from the second light-emitting layer.

7. The light-emitting element according to claim 6 ,
wherein a plurality of light-emitting elements, including the light-emitting element, is provided, and the plurality of light-emitting elements includes at least a blue light-emitting element configured to emit blue light, a green light-emitting element configured to emit green light, and a red light-emitting element configured to emit red light, and
in the red light-emitting element, the wavelength of the light from the first light-emitting layer is longer than the wavelength of the light from the second light-emitting layer.

8. The light-emitting element according to claim 6 ,
wherein a plurality of light-emitting elements, including the light-emitting element, is provided, and the plurality of light-emitting elements includes at least a blue light-emitting element configured to emit blue light, a green light-emitting element configured to emit green light, and a red light-emitting element configured to emit red light, and
in the green light-emitting element, the wavelength of the light from the first light-emitting layer is longer than the wavelength of the light from the second light-emitting layer.

9. The light-emitting element according to claim 6 ,
wherein a plurality of light-emitting elements, including the light-emitting element, is provided, and the plurality of light-emitting elements includes at least a blue light-emitting element configured to emit blue light, a green light-emitting element configured to emit green light, and a red light-emitting element configured to emit red light, and
in the blue light-emitting element, the wavelength of the light from the first light-emitting layer is longer than the wavelength of the light from the second light-emitting layer.

10. The light-emitting element according to claim 6 ,
wherein the second core of the second quantum dot included in the second light-emitting layer includes Cd, and the first core of the first quantum dot included in the first light-emitting layer is free of Cd.

11. The light-emitting element according to claim 1 ,
wherein the first core includes InP, and the second core includes CdSe.

12. The light-emitting element according to claim 11 ,
wherein the first shell includes ZnS, and the second shell includes at least one of CdS, CdZnS, ZnSe, ZnS, and ZnSeS.

13. The light-emitting element according to claim 11 ,
wherein the first shell includes ZnSeS, and the second shell includes at least one of CdS, CdZnS, ZnSe, and ZnSeS.

14. The light-emitting element according to claim 11 ,
wherein the first shell includes ZnSe, and the second shell includes at least one of CdS, CdZnS, and ZnSe.

15. A light-emitting device comprising:
the light-emitting element according to claim 1 .

16. The light-emitting element according to claim 1 ,
wherein the first light-emitting layer and the second light-emitting layer are in contact with each other.

17. The light-emitting element according to claim 1 ,
wherein an outflow of electrons from the first light-emitting layer to the anode electrode is suppressed.

18. The light-emitting element according to claim 1 ,
wherein the first light-emitting layer and the second light-emitting layer form a function layer.

19. The light-emitting element according to claim 1 ,
wherein an entirety of one main surface of the first light-emitting layer and an entirety of one main surface of the second light-emitting layer are in direct contact with each other.

20. The light-emitting element according to claim 1 ,
wherein the first light-emitting layer and the second light-emitting layer suppress an outflow of electrons from the first light-emitting layer to the anode electrode by being in direct contact with each other.

Assignees

• Sharp Kk

Inventors

• Sakuma Jun
• Asaoka Yasushi

Classifications

• H10H29/142

  Two-dimensional arrangements, e.g. asymmetric LED layout · CPC title

• H10H20/8512

  Wavelength conversion materials · CPC title

• H10H20/8514 Primary

  characterised by their shape, e.g. plate or foil · CPC title

• H10K50/115

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

• H05B33/14

  characterised by the chemical or physical composition or the arrangement of the electroluminescent material {, or by the simultaneous addition of the electroluminescent material in or onto the light source} · CPC title