Display panel and display device

1 . A display panel, comprising a planar display area and a curved display area disposed on at least one side of the planar display area, wherein the display panel comprises:

a light emitting layer;

a cathode layer disposed on the light emitting layer and covering the light emitting layer, wherein the cathode layer has a substantially uniform thickness throughout the planar display area in a direction; and

an optical coupling layer disposed on a side of the cathode layer away from the light emitting layer,

wherein the cathode layer in the curved display area has a thickness less than the substantially uniform thickness of the cathode layer in the planar display area and the optical coupling layer in the curved display area has a thickness greater than or equal to a thickness of the optical coupling layer in the planar display area, so that the light emitting layer in the curved display area has a light-emitting efficiency greater than a light-emitting efficiency of the light emitting layer in the planar display area;

the cathode layer comprises: a first cathode sub-layer disposed in the planar display area and the curved display area; and a second cathode sub-layer disposed between the first cathode sub-layer and the optical coupling layer and disposed in the planar display area; and

the first cathode sub-layer has a material different from the second cathode sub-layer, and a refractive index of the first cathode sub-layer is less than or equal to a refractive index of the second cathode sub-layer or the refractive index of the first cathode sub-layer is greater than or equal to the refractive index of the second cathode sub-layer.

2 . The display panel according to claim 1 , wherein a difference between the thickness of the cathode layer in the planar display area and the thickness of the cathode layer in the curved display area is greater than or equal to 2 nm and less than or equal to 10 nm.

3 . The display panel according to claim 1 , wherein the cathode layer has a recess in the curved display area.

4 . The display panel according to claim 1 , wherein the material of the first cathode sub-layer includes at least one of ytterbium, calcium, magnesium or silver, and the material of the second cathode sub-layer includes at least one of ytterbium, calcium, magnesium or silver.

5 . The display panel according to claim 1 , wherein a difference between the thickness of the optical coupling layer in the curved display area and the thickness of the optical coupling layer in the planar display area is greater than or equal to 10 nm.

6 . The display panel according to claim 1 , wherein the optical coupling layer has a protrusion on a side away from the cathode layer in the curved display area.

7 . The display panel according to claim 1 , wherein the optical coupling layer comprises:

a first optical coupling sub-layer disposed in the curved display area and not in the planar display area; and

a second optical coupling sub-layer disposed in both the curved display area and the planar display area,

wherein the first optical coupling sub-layer is disposed between the second optical coupling sub-layer and the cathode layer, or the first optical coupling sub-layer is disposed on a side of the second optical coupling sub-layer away from the cathode layer.

8 . The display panel according to claim 7 , wherein the first optical coupling sub-layer has a thickness greater than or equal to 10 nm and less than or equal to 60 nm, and the second optical coupling sub-layer has a thickness greater than or equal to 50 nm and less than or equal to 200 nm.

9 . The display panel according to claim 7 , wherein the first optical coupling sub-layer has a material same as the second optical coupling sub-layer.

10 . The display panel according to claim 9 , wherein each of the first optical coupling sub-layer and the second optical coupling sub-layer has an organic small molecule hole transport material.

11 . The display panel according to claim 7 , wherein the first optical coupling sub-layer has a material different from the second optical coupling sub-layer, a refractive index of the first optical coupling sub-layer is greater than or equal to a refractive index of the second optical coupling sub-layer, or the refractive index of the first optical coupling sub-layer is less than or equal to the refractive index of the second optical coupling sub-layer.

12 . The display panel according to claim 1 , wherein a thickness of the first cathode sub-layer is greater than or equal to 8 nm and less than or equal to 20 nm, and a thickness of the second cathode sub-layer is greater than or equal to 2 nm and less than or equal to 10 nm.

13 . A display device, comprising a display panel, the display panel comprising a planar display area and a curved display area disposed on at least one side of the planar display area, wherein the display panel comprises:

a light emitting layer;

a cathode layer disposed on the light emitting layer and covering the light emitting layer, wherein the cathode layer has a substantially uniform thickness throughout the planar display area in a direction; and

an optical coupling layer disposed on a side of the cathode layer away from the light emitting layer,

wherein the cathode layer in the curved display area has a thickness less than the substantially uniform thickness of the cathode layer in the planar display area and the optical coupling layer in the curved display area has a thickness greater than or equal to a thickness of the optical coupling layer in the planar display area, so that the light emitting layer in the curved display area has a light-emitting efficiency greater than a light-emitting efficiency of the light emitting layer in the planar display area;

the cathode layer comprises: a first cathode sub-layer disposed in the planar display area and the curved display area; and a second cathode sub-layer disposed between the first cathode sub-layer and the optical coupling layer and disposed in the planar display area; and

the first cathode sub-layer has a material different from the second cathode sub-layer, and a refractive index of the first cathode sub-layer is less than or equal to a refractive index of the second cathode sub-layer or the refractive index of the first cathode sub-layer is greater than or equal to the refractive index of the second cathode sub-layer.

14 . The display device according to claim 13 , wherein a difference between the thickness of the cathode layer in the planar display area and the thickness of the cathode layer in the curved display area is greater than or equal to 2 nm and less than or equal to 10 nm.

15 . The display device according to claim 13 , wherein the cathode layer has a recess in the curved display area.

16 . The display device according to claim 13 , wherein the optical coupling layer comprises:

a first optical coupling sub-layer disposed in the curved display area and not in the planar display area; and

a second optical coupling sub-layer disposed in both the curved display area and the planar display area,

wherein the first optical coupling sub-layer is disposed between the second optical coupling sub-layer and the cathode layer, or the first optical coupling sub-layer is disposed on a side of the second optical coupling sub-layer away from the cathode layer.