Light-Emitting Element, Light-Emitting Device, Display Device, Electronic Device, and Lighting Device

A light-emitting device comprising a light-emitting layer,

• the light-emitting layer comprising:
• a phosphorescent compound as a guest material;
• and
• a first organic compound and a second organic compound as a host material,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein an emission spectrum of the exciplex has an overlap with a wavelength of a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.

A light-emitting device comprising a light-emitting layer,

• the light-emitting layer comprising:
• a phosphorescent compound as a guest material;
• and
• a first organic compound and a second organic compound as a host material,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein a band having a maximum value of an emission spectrum of the exciplex has an overlap with a band having a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.

A light-emitting device comprising a light-emitting layer,

• the light-emitting layer comprising:
• a phosphorescent compound as a guest material;
• and
• a first organic compound and a second organic compound as a host material,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein a wavelength range having half of intensity of a maximum value of an emission spectrum of the exciplex has an overlap with a wavelength range having half of intensity of a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.

A material comprising a first organic compound and a second organic compound,

• wherein the material is used in a light-emitting layer including a phosphorescent compound,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein an emission spectrum of the exciplex has an overlap with a wavelength of a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.

A material comprising a first organic compound and a second organic compound,

• wherein the material is used in a light-emitting layer including a phosphorescent compound,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein a band having a maximum value of an emission spectrum of the exciplex has an overlap with a band having a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.

A material comprising a first organic compound and a second organic compound,

• wherein the material is used in a light-emitting layer including a phosphorescent compound,
• wherein the first organic compound and the second organic compound are configured to form an exciplex,
• wherein a wavelength range having half of intensity of a maximum value of an emission spectrum of the exciplex has an overlap with a wavelength range having half of intensity of a longest-wavelength-side peak of a function ε(λ)λ4 of the phosphorescent compound,
• wherein λ denotes a wavelength, and
• wherein ε(λ) denotes a molar absorption coefficient of the phosphorescent compound and is a function of the wavelength λ.