Light-emitting element and display device and lighting device using same
View Patent ↗A light-emitting element is provided having a layered structure composed of at least a light-emitting layer having a light-emitting region and a reflective layer for reflecting light emitted from the light-emitting region. Light emitted from the light-emitting region is extracted from a light-extracting surface distanced from the light-emitting region. A light-scattering portion is present in a part of the reflective layer.
1. A light-emitting element comprising:
a reflective layer having a light-scattering portion with an irregular surface;
a planarizing layer deposited on the reflective layer, the planarizing layer planarizing the irregular surface of the reflective layer;
a transparent first electrode deposited on the planarizing layer;
a light-emitting layer deposited on the first electrode, the light-emitting layer having a light-emitting region; and
a transparent second electrode deposited on the light-emitting layer.
2. The light-emitting element according to claim 1 , wherein the planarizing layer comprises an insulating material.
3. The light-emitting element according to claim 1 , wherein the reflective layer is in a form of an island or lattice.
4. The light-emitting element according to claim 3 , wherein when the reflective layer is in the form of an island, there are a plurality of the reflective layers in the form of an island.
5. The light-emitting element according to claim 3 ,
wherein when there is an interface, at which a refractive index decreases in a direction from the light-emitting layer to the light-extracting surface, between the light-emitting layer and the light-extracting surface, the following Equation (1) is satisfied:
t<(n cos θ/2)× L (1),
where t is a distance between the reflective layer and the interface, L is a longest distance between any two points in an in-plane direction of the light-emitting element, θ is a critical angle for the interface, and n is a refractive index of the light-emitting layer.
6. The light-emitting element according to claim 4 ,
wherein when there is an interface, at which a refractive index decreases in a direction from the light-emitting layer to the light-extracting surface, between the light-emitting layer and the light-extracting surface, the following Equation (1) is satisfied:
t<(n cos θ/2)×L (1),
where t is a distance between the reflective layer and the interface, L is a longest distance between any two points in an in-plane direction of the light-emitting element, θ is a critical angle for the interface, and n is a refractive index of the light-emitting layer.
7. The light-emitting element according to claim 1 , wherein a maximum value (Rmax) of surface roughness of the irregular surface is ¼ or more of a peak wavelength of light.
8. The light-emitting element according to claim 1 , wherein the planarizing layer is made of a polymer.
9. The light-emitting element according to claim 1 , wherein the planarizing layer is made of a conductive polymer.
10. The light-emitting element according to claim 1 , wherein an aerogel layer is used as the layer with a refractive index of approximately 1.
11. A display device comprising the light-emitting element in accordance with claim 1 .
12. A lighting device comprising the light-emitting element in accordance with claim 1 .