Patent ID: 7777408

Claim:
An organic light-emitting device comprising: an anode; a hole transport layer; a light-emitting layer; an electron transport layer; a cathode; and at least one of a first buffer layer interposed between the light-emitting layer and the hole transport layer and a second buffer layer interposed between the light-emitting layer and the electron transport layer, wherein the first buffer layer comprises a light-emitting material and a hole transport material, the first buffer layer is formed as a gradient layer of the light emitting material and the hole transport material, and the concentration of the light-emitting material increases towards the light-emitting layer, the concentration of the light-emitting material decreases away from the light-emitting layer, the concentration of the hole transport material increases towards the hole transport layer, and the concentration of the hole transport material decreases away from the hole transport layer; wherein the second buffer layer comprises a light-emitting material and an electron transport material, the second buffer layer is formed as a gradient layer of the light-emitting material and the electron transport material and the concentration of the light-emitting material increases towards the light-emitting layer, the concentration of the light-emitting material decreases away from the light-emitting layer, the concentration of the electron transport material increases towards the electron transport layer, and the concentration of the electron transport material decreases away from the electron transport layer, wherein a mass ratio of the light-emitting material to the hole transport material in the first buffer layer is from 1:9 to 9:1 edge to edge.