Light-emitting device and lighting device

摘要

To improve power efficiency of a light-emitting element for white emission even when light in a wavelength range of low luminosity is utilized. As a light-emitting element for white emission, three light-emitting layers are stacked. In such a light-emitting element, the three light-emitting layers are included between a light-transmitting electrode and a light-reflecting electrode, and light emitted from each light-emitting layer is reflected on the light-reflecting electrode and is transmitted through the light-transmitting electrode. In addition, the light-emitting layer closer to the light-reflecting electrode has a shorter optical path length. Thus, the position of each light-emitting layer is limited depending on the distance from the light-reflective electrode, and the optical path length of each light-emitting layer is adjusted; therefore the light-emitting element with high power efficiency can be provided.

主权项

1. A light-emitting element comprising:
a light-transmitting electrode; a first light-emitting layer over the light-transmitting electrode; a first intermediate layer over the first light-emitting layer; a second light-emitting layer over the first intermediate layer; a second intermediate layer over the second light-emitting layer; a third light-emitting layer over the second intermediate layer; and a light-reflecting electrode over the third light-emitting layer, wherein a peak of a spectrum of light emitted from the first light-emitting layer is located on a longer wavelength side as compared to a peak of a spectrum of light emitted from the second light-emitting layer and a peak of a spectrum of light emitted from the third light-emitting layer, wherein the peak of the spectrum of light emitted from the second light-emitting layer is located on a shorter wavelength side as compared to the peak of the spectrum of light emitted from the first light-emitting layer and the peak of the spectrum of light emitted from the third light-emitting layer, wherein an optical path length between the light-reflecting electrode and the first light-emitting layer is three fourths of a peak wavelength of light emitted from the first light-emitting layer, wherein an optical path length between the light-reflecting electrode and the second light-emitting layer is three fourths of a peak wavelength of light emitted from the second light-emitting layer, and wherein an optical path length between the light-reflecting electrode and the third light-emitting layer is one fourth of a peak wavelength of light emitted from the third light-emitting layer.