| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-lifetime organic EL element with high efficiency which does not have a layer for preventing the penetration of holes and electrons into a counter electrode.SOLUTION: The organic EL element includes a positive electrode, three or more hole-injection/transport layers formed over the positive electrode, a light-emitting layer formed over the hole-injection/transport layers, and a negative electrode formed over the light-emitting layer. The three or more hole-injection/transport layers are defined as a first, a second, ..., and an nth (n is an integer equal to or larger than 3) hole-injection/transport layer from the positive electrode side. If the electron affinity of a constituent material of the light-emitting layer is Eaand the electron affinity of a constituent material of an xth (x is an integer between 1 and n) is defined as Ea, Ea≤Eais satisfied, and Ea≤Eais satisfied for all values of x between 2 and n. Furthermore, when the ionization potential of the constituent material of the light-emitting layer is Ipand the ionization potential of the constituent material of the xth hole-injection/transport layer is Ip, Ip≥Ipis satisfied, and Ip>Ipis satisfied for all values of x between 2 and n. |
