Light-emitting element

摘要

Provided is a light-emitting element with high external quantum efficiency, or a light-emitting element with a long lifetime. The light-emitting element includes, between a pair of electrodes, a light-emitting layer including a guest material and a host material, in which an emission spectrum of the host material overlaps with an absorption spectrum of the guest material, and phosphorescence is emitted by conversion of an excitation energy of the host material into an excitation energy of the guest material. By using the overlap between the emission spectrum of the host material and the absorption spectrum of the guest material, the energy smoothly transfers from the host material to the guest material, so that the energy transfer efficiency of the light-emitting element is high. Accordingly, a light-emitting element with high external quantum efficiency can be achieved.

主权项

1. A light-emitting element comprising:
a pair of electrodes; and a light-emitting layer comprising a guest material and a host material between the pair of electrodes, wherein an emission spectrum of the host material overlaps with a longest-wavelength-side absorption band in an absorption spectrum of the guest material, wherein phosphorescence is emitted by conversion of an excitation energy of the host material into an excitation energy of the guest material, wherein a molar absorption coefficient of the longest-wavelength-side absorption band in the absorption spectrum is 5000 M−1·cm−1 or higher, and wherein the guest material is an organometallic complex which is a phosphorescent material.