Light-emitting element

摘要

To provide a light-emitting element which uses a fluorescent material as a light-emitting substance and has higher luminous efficiency. To provide a light-emitting element which includes a mixture of a thermally activated delayed fluorescent substance and a fluorescent material. By making the emission spectrum of the thermally activated delayed fluorescent substance overlap with an absorption band on the longest wavelength side in absorption by the fluorescent material in an S1 level of the fluorescent material, energy at an S1 level of the thermally activated delayed fluorescent substance can be transferred to the S1 of the fluorescent material. Alternatively, it is also possible that the S1 of the thermally activated delayed fluorescent substance is generated from part of the energy of a T1 level of the thermally activated delayed fluorescent substance, and is transferred to the S1 of the fluorescent material.

主权项

1. A light-emitting element comprising:
a pair of electrodes; and an EL layer between the pair of electrodes, wherein the EL layer comprises a light-emitting layer, wherein the light-emitting layer comprises a first organic compound, a second organic compound, and a fluorescent material, wherein the first organic compound and the second organic compound form an exciplex which exhibits thermally activated delayed fluorescence, and wherein, in the exciplex, a difference between levels of a triplet excited state and a singlet excited state is 0.2 eV or less.