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

摘要

A light-emitting element which has low driving voltage and high emission efficiency is provided. The light-emitting element includes, between a pair of electrodes, a hole-transport layer and a light-emitting layer over the hole-transport layer. The light-emitting layer contains a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a light-emitting third organic compound converting triplet excitation energy into light emission. A combination of the first organic compound and the second organic compound forms an exciplex. The hole-transport layer contains at least a fourth organic compound whose HOMO level is lower than or equal to that of the second organic compound and a fifth organic compound whose HOMO level is higher than that of the second organic compound.

主权项

1. A light-emitting element comprising:
a hole-transport layer; and a light-emitting layer over the hole-transport layer, wherein the light-emitting layer includes a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a third organic compound converting triplet excitation energy into light emission, wherein a combination of the first organic compound and the second organic compound forms an exciplex, wherein the hole-transport layer includes a fourth organic compound and a fifth organic compound, wherein a HOMO level of the fourth organic compound is lower than or equal to a HOMO level of the second organic compound, and wherein a HOMO level of the fifth organic compound is higher than the HOMO level of the second organic compound.