US Patent 11864403 Light-emitting device comprising first to third light-emitting layers

Provided is a light-emitting element which includes a first electrode, a second electrode over the first electrode, and first and second light-emitting layers therebetween. The first light-emitting layer contains a first host material and a first light-emitting material, and the second light-emitting layer contains a second host material and a second light-emitting material. The first light-emitting material is a fluorescent material, and the second light-emitting material is a phosphorescent material. The level of the lowest triplet excited state (T