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

摘要

Disclosed is a light-emitting element comprising a plurality of light-emitting units which are separated from one another by a charge generation layer. The light-emitting units each have a light-emitting layer which is featured by a stack of two layers. Each of the two layers includes a host material and a phosphorescent material where the phosphorescent material in one of the two layers is blue emissive while the phosphorescent material in the other of the two layers exhibits a maximum emission peak in a range from 500 nm to 700 nm. The phosphorescent material exhibiting a maximum emission peak in a range from 500 nm to 700 nm may be different from light-emitting unit to light-emitting unit. An additive may be included in at least one of the two layers so that an exciplex is formed with the host material.

主权项

1. A light-emitting element comprising:
a first electrode; a first light-emitting unit over the first electrode, the first light-emitting unit comprising a first light-emitting layer; a second light-emitting unit over the first light-emitting unit, the second light-emitting unit comprising a second light-emitting layer; and a second electrode over the second light-emitting unit, wherein: the first light-emitting layer comprises:
a first layer comprising a first host material and a first phosphorescent substance which exhibits a maximum emission peak in a range from 500 nm to 700 nm; anda second layer in contact with the first layer, the second layer comprising a second host material and a second phosphorescent substance which exhibits a maximum emission peak in a range from 400 nm to 500 nm; the second light-emitting layer comprises:
a third layer comprising a third host material and a third phosphorescent substance which exhibits a maximum emission peak in a range from 500 nm to 700 nm and is different from the first phosphorescent substance; anda fourth layer in contact with the third layer, the fourth layer comprising a fourth host material and a fourth phosphorescent substance which exhibits a maximum emission peak in a range from 400 nm to 500 nm; at least one of the first to fourth layers further comprises an additive; and the additive is capable of forming an exciplex with at least one of the first to fourth host materials which is included in the one of the first to fourth layers.