Abstract: A novel light-receiving device that is highly convenient, useful, or reliable is provided. A light-receiving device including a light-receiving layer (203) between a pair of electrodes (201, 202) is provided. The light-receiving layer 203 includes an active layer. The active layer includes a first organic compound. An SP value of the first organic compound is greater than or equal to 9.0 [(cal/cm3)1/2] and less than or equal to 11.0 [(cal/cm3)1/2]. Alternatively, a light-receiving device including a light-receiving layer (203) between a pair of electrodes (201, 202) is provided. The light-receiving layer (203) includes an active layer. The active layer includes a first organic compound. An absolute value of a difference in an SP value between the first organic compound and an oxygen-containing solvent except for alcohol is less than or equal to 1.0 [(cal/cm3)1/2].

Abstract: A light-emitting device with high emission efficiency is provided. The light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a light-emitting layer and an electron-transport layer; the light-emitting layer includes a light-emitting material; the electron-transport layer includes an organic compound having an electron-transport property and a metal complex of an alkali metal; the ordinary refractive index of the organic compound having an electron-transport property in a peak wavelength of light emitted from the light-emitting material is greater than or equal to 1.50 and less than or equal to 1.75; and the ordinary refractive index of the metal complex of an alkali metal in the peak wavelength of the light emitted from the light-emitting material is greater than or equal to 1.45 and less than or equal to 1.70.

Abstract: A novel high molecular compound is provided. The high molecular compound includes a repeating unit. The repeating unit has a fluorenediyl group, a hole-transport skeleton, and an electron-transport skeleton. The hole-transport skeleton is bonded to the fluorenediyl group through a substituted or unsubstituted first arylene group. The electron-transport skeleton is bonded to the fluorenediyl group through a substituted or unsubstituted second arylene group. In an excited state, intramolecular charge transfer occurs between the hole-transport skeleton and the electron-transport skeleton.

Abstract: The reliability of a light-emitting device is improved. Provided is a light-emitting device including a light-emitting layer between a first electrode and a second electrode. The light-emitting layer contains a light-emitting substance and a first organic compound. A difference between a sum of energy of the first organic compound in a ground state and energy of an oxygen molecule in a ground state and energy of a transition state formed by the first organic compound and the oxygen molecule is greater than or equal to 1.84 eV. A difference between the energy of the transition state formed by the first organic compound and the oxygen molecule and energy of an oxygen adduct of the first organic compound in a ground state is less than or equal to 0.87 eV.

Abstract: A light-emitting device with high emission efficiency is provided. The light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a light-emitting layer and an electron-transport layer; the light-emitting layer includes a light-emitting material; the electron-transport layer includes an organic compound having an electron-transport property and a metal complex of an alkali metal; the ordinary refractive index of the organic compound having an electron-transport property in a peak wavelength of light emitted from the light-emitting material is greater than or equal to 1.50 and less than or equal to 1.75; and the ordinary refractive index of the metal complex of an alkali metal in the peak wavelength of the light emitted from the light-emitting material is greater than or equal to 1.45 and less than or equal to 1.70.

Abstract: A novel light-emitting device that is highly convenient, useful, or reliable is provided. The light-emitting device includes a first electrode, a second electrode, and a first unit. The first unit is located between the first electrode and the second electrode, and the first unit has a function of emitting light. The first unit contains a light-emitting organic compound and an organic compound HRM. The organic compound HRM has four or more rotatable bonds and a principal moment of inertia. The principal moment of inertia includes a first normalized principal moment of inertia NPR1 and a second normalized principal moment of inertia NPR2 in a predetermined region.

Abstract: A novel light-emitting device, a novel light-emitting apparatus, a novel electronic device, a novel display device, and a novel lighting device which are highly convenient, useful, or reliable are provided. The light-emitting device includes a first electrode, a second electrode, a first layer, and a second layer. The second electrode includes a region overlapping with the first electrode, the first layer includes a region sandwiched between the first electrode and the second electrode, the first layer includes a light-emitting material, the light-emitting material has a function of emitting photoluminescent light in a solution, the photoluminescent light has a first spectrum, the first spectrum has a maximum peak at a wavelength ?1, and the wavelength ?1 is in the range greater than or equal to 440 nm and less than or equal to 470 nm.

Abstract: A light-emitting device with high emission efficiency is provided. The light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a light-emitting layer and an electron-transport layer; the light-emitting layer includes a light-emitting material; the electron-transport layer includes an organic compound having an electron-transport property and a metal complex of an alkali metal; the ordinary refractive index of the organic compound having an electron-transport property in a peak wavelength of light emitted from the light-emitting material is greater than or equal to 1.50 and less than or equal to 1.75; and the ordinary refractive index of the metal complex of an alkali metal in the peak wavelength of the light emitted from the light-emitting material is greater than or equal to 1.45 and less than or equal to 1.70.

Abstract: A light-emitting device material with a low refractive index is provided. The light-emitting device material contains an organic compound which has a pyridine skeleton, a diazine skeleton, or a triazine skeleton and in which the proportion of carbon atoms forming a bond by sp3 hybrid orbitals is within a certain range. The light-emitting device material contains an organic compound including at least one six-membered heteroaromatic ring having 1 to 3 nitrogen atoms and a plurality of aromatic hydrocarbon rings each having 6 to 14 carbon atoms in a ring. At least two of the plurality of aromatic hydrocarbon rings are benzene rings. The organic compound has a plurality of hydrocarbon groups forming a bond by the sp3 hybrid orbitals. The ordinary refractive index of a layer containing the organic compound with respect to light with a wavelength in the range from 455 nm to 465 nm is 1.5 to 1.75.