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

摘要

A light-emitting element includes a first electrode; a first light-emitting layer over the first electrode, containing a first phosphorescent compound and a first host material; a second light-emitting layer over the first light-emitting layer, containing a second phosphorescent compound and a second host material; a third light-emitting layer over the second light-emitting layer, containing a third phosphorescent compound and a third host material; and a second electrode over the third light-emitting layer. Between peaks of emission spectra of the first, second, and third phosphorescent compounds, the peak of the emission spectrum of the second phosphorescent compound is on the longest wavelength side and that of the emission spectrum of the third phosphorescent compound is on the shortest wavelength side. The third host material has higher triplet excitation energy than the first host material and the second host material.

主权项

1. A light-emitting element comprising:
a first electrode: a first light-emitting layer over the first electrode, the first light-emitting layer comprising a first phosphorescent compound and a first host material; a second light-emitting layer over the first light-emitting layer, the second light-emitting layer comprising a second phosphorescent compound and a second host material; a third light-emitting layer over the second light-emitting layer, the third light-emitting layer comprising a third phosphorescent compound and a third host material; and a second electrode over the third light-emitting layer, wherein between a peak of an emission spectrum of the first phosphorescent compound, a peak of an emission spectrum of the second phosphorescent compound, and a peak of an emission spectrum of the third phosphorescent compound, the peak of the emission spectrum of the second phosphorescent compound is on a longest wavelength side and the peak of the emission spectrum of the third phosphorescent compound is on a shortest wavelength side, and wherein the third host material has higher triplet excitation energy than the first host material and the second host material.