Light-emitting element, light-emitting device, electronic device, and lighting device

摘要

An object is to provide a light-emitting element capable of emitting light with a high luminance even at a low voltage, and having a long lifetime. The light-emitting element includes n EL layers between an anode and a cathode (n is a natural number of two or more), and also includes, between m-th EL layer from the anode and (m+1)-th EL layer (m is a natural number, 1≦m≦n−1), a first layer including a first donor material in contact with the m-th EL layer, a second layer including an electron-transport material and a second donor material in contact with the first layer, and a third layer including a hole-transport material and an acceptor material in contact with the second layer and the (m+1)-th EL layer.

主权项

1. A light-emitting device comprising:
a substrate having a light-transmitting property; a transparent conductive layer over the substrate; a light-emitting material layer over the transparent conductive layer; and a conductive layer over the light-emitting material layer, wherein the light-emitting material layer comprises:
n light-emitting layers (n is a natural number of two or more);a first layer over an m-th light-emitting layer (m is a natural number, 1≦m≦n−1);a second layer over the first layer; anda third layer over the second layer, wherein the first layer, the second layer, and the third layer are positioned between the m-th light-emitting layer and (m+1)-th light-emitting layer, wherein the first layer comprises a first donor material, wherein the second layer comprises an electron-transport material and a second donor material, wherein the third layer comprises an acceptor material, and wherein a LUMO level of the second layer is between a LUMO level of the first layer and an acceptor level of the third layer.