Patent ID: 11917840
Assignee: SEMICONDUCTOR ENERGY LABORATORY CO., LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  G | IPC H

Claim 14:
15. A light-emitting device comprising:
a first electrode;
a second electrode; and
an EL layer between the first electrode and the second electrode,
wherein the first electrode and the second electrode overlap each other,
wherein one of the first electrode and the second electrode is a reflective electrode and the other is a semi-transmissive and semi-reflective electrode,
wherein the EL layer comprises a light-emitting layer,
wherein the light-emitting layer comprises an emission center substance,
wherein an average value of photon energy of light emitted by the emission center substance in a solution state is denoted by Eave [eV],
wherein emission edge energy on a short wavelength side of an emission spectrum of the emission center substance in the solution state is denoted by Eedge [eV],
wherein photon energy corresponding to a light having a wavelength λ is denoted by Eem [eV],
wherein the wavelength λ is longer than a peak wavelength of the emission spectrum of the emission center substance in the solution state,
wherein an optical path length between the reflective electrode and the light-emitting layer is configured to (2n−1)λ/4 where n is a natural number, and
wherein Eem [eV] is expressed by the following formula (1):

Eave≤Eem≤0.95Eedge  (1).