Light-emitting element, light-emitting device, and method for manufacturing light-emitting element
A light-emitting layer of a light-emitting element contains halogen ligands and organic ligands coordinated to each of quantum dots. The light-emitting layer includes: a first region toward a hole-transport layer; and a second region toward an electron-transport layer. In the first region, a concentration of the halogen ligands is higher than a concentration of the organic ligands, and, in the second region, the concentration of the halogen ligands is lower than the concentration of the organic ligands.
1. A light-emitting element comprising:
a cathode; an anode; a light-emitting layer provided between the cathode and the anode and containing quantum dots; an electron-transport layer provided between the light-emitting layer and the cathode; and a hole-transport layer provided between the light-emitting layer and the anode,
the light-emitting layer containing halogen ligands and organic ligands coordinated to each of the quantum dots,
the light-emitting layer including: a first region toward the hole-transport layer; and a second region toward the electron-transport layer, and
in the first region, a concentration of the halogen ligands being higher than a concentration of the organic ligands, and, in the second region, the concentration of the halogen ligands being lower than the concentration of the organic ligands.
2. The light-emitting element according to claim 1 , wherein
the halogen ligands contain halogens selected from among at least one or more of F, Cl, Br and I.
3. The light-emitting element according to claim 1 , wherein
of ligands coordinated to the quantum dots contained in the first region, a proportion of the halogen ligands is higher than a proportion of the organic ligands.
4. The light-emitting element according to claim 1 , wherein
of ligands coordinated to the quantum dots contained in the second region, a proportion of the organic ligands is higher than a proportion of the halogen ligands.
5. The light-emitting element according to claim 1 , wherein
the light-emitting layer contains quantum dots provided between the hole-transport layer and the first region, and having the halogen ligands alone.
6. The light-emitting element according to claim 1 , wherein
the light-emitting layer contains quantum dots provided between the electron-transport layer and the second region, and having the organic ligands alone.
7. The light-emitting element according to claim 1 , wherein
the organic ligands contained in the first region are smaller in quantity than the organic ligands contained in the second region.
8. The light-emitting element according to claim 1 , wherein
in the light-emitting layer, a concentration of halogens gradually decreases from toward the hole-transport layer to toward the electron-transport layer.
9. The light-emitting element according to claim 1 , wherein
the light-emitting layer includes: a red light-emitting layer; and a green light-emitting layer, and
in a thickness direction of the light-emitting layer, a proportion of the first region in the green light-emitting layer is larger than a proportion of the first region in the red light-emitting layer.
10. The light-emitting element according to claim 9 , wherein
the first region in the green light-emitting layer is thicker than the first region in the red light-emitting layer.
11. The light-emitting element according to claim 9 , wherein
the light-emitting layer further includes a blue light-emitting layer, and
in the thickness direction of the light-emitting layer, the proportion of the first region in the green light-emitting layer is smaller than a proportion of the first region in the blue light-emitting layer.
12. The light-emitting element according to claim 11 , wherein
the first region in the blue light-emitting layer is thicker than the first region in the red light-emitting layer.
13. The light-emitting element according to claim 11 , wherein
the first region in the blue light-emitting layer is thicker than the first region in the green light-emitting layer.
14. The light-emitting element according to claim 9 , wherein
a thickness of the first region in the red light-emitting layer is greater than or equal to one-fifth of, and smaller than or equal to one-third of, a thickness of the red light-emitting layer.
15. The light-emitting element according to claim 9 , wherein
a thickness of the first region in the green light-emitting layer is greater than or equal to one-fourth of, and smaller than or equal to three-fourth of, a thickness of the green light-emitting layer.
16. The light-emitting element according to claim 11 , wherein
a thickness of the first region in the blue light-emitting layer is greater than or equal to one-half of, and smaller than or equal to four-fifth of, a thickness of the blue light-emitting layer.
17. The light-emitting element according to claim 1 , wherein
the light-emitting layer includes: a red light-emitting layer; and a green light-emitting layer, and
a proportion of a thickness of the first region in the red light-emitting layer to a thickness of the red light-emitting layer is equal to a proportion of a thickness of the first region in the green light-emitting layer to a thickness of the green light-emitting layer, and the thicknesses of the first regions in the red light-emitting layer and in the green light-emitting layer are greater than or equal to one-fifth of, and smaller than or equal to one-half of, the thicknesses of the red light-emitting layer and the green light-emitting layer, and
the concentration of the halogen ligands in the first region of the green light-emitting layer is higher than the concentration of the halogen ligands in the first region of the red light-emitting layer.
18. The light-emitting element according to claim 17 , wherein
the light-emitting layer further includes a blue light-emitting layer, and
a proportion of the thickness of the first region in the green light-emitting layer to the thickness of the green light-emitting layer is equal to a proportion of a thickness of the first region in the blue light-emitting layer to a thickness of the blue light-emitting layer, and the thicknesses of the first regions in the green light-emitting layer and in the blue light-emitting layer are greater than or equal to one-fifth of, and smaller than or equal to one-half of, the thicknesses of the green light-emitting layer and the blue light-emitting layer, and
the concentration of the halogen ligands in the first region of the blue light-emitting layer is higher than the concentration of the halogen ligands in the first region of the green light-emitting layer.
19. A light-emitting device including at least one light-emitting element according to claim 1 .
20. A method for manufacturing a light-emitting element including: a cathode; an anode; a light-emitting layer provided between the cathode and the anode and containing quantum dots; an electron-transport layer provided between the light-emitting layer and the cathode; and a hole-transport layer provided between the light-emitting layer and the anode, the method comprising
forming the light-emitting layer above the electron-transport layer,
the forming of the light-emitting layer including:
stacking the light-emitting layer above the electron-transport layer, the light-emitting layer containing the quantum dots having organic ligands;
impregnating a surface of the light-emitting layer with a halogen agent toward the electron-transport layer; and
heating the light-emitting layer after the impregnating.