Abstract: A novel light-emitting device that is highly convenient, useful, or reliable is provided. The light-emitting device includes a function of emitting light, a first electrode, a second electrode, and a unit. The light has the maximum peak at a wavelength (lambda). The second electrode includes a region overlapping with the first electrode. The unit includes a region positioned between the first electrode and the second electrode. The unit includes a first layer, a second layer, and a third layer. The first layer includes a region positioned between the second layer and the third layer. The first layer contains a light-emitting material. The second layer includes a fourth layer and a fifth layer. The fifth layer includes a region positioned between the fourth layer and the first layer. The fourth layer contains a first organic compound. The first organic compound has a first refractive index with respect to light having the wavelength (lambda). The fifth layer is in contact with the fourth layer.

Abstract: To provide a light-emitting element with high emission efficiency and low driving voltage. The light-emitting element includes a guest material and a host material. A LUMO level of the host material is higher than a LUMO level of the host material, and a HOMO level of the guest material is lower than a HOMO level of the host material. The guest material has a function of converting triplet excitation energy into light emission. The difference between a singlet excitation energy level and a triplet excitation energy level of the host material is greater than 0 eV and less than or equal to 0.2 eV. The energy difference between the LUMO level and the HOMO level of the host material is larger than or equal to light emission energy of the guest material.

Abstract: Provided is an inexpensive light-emitting device with high emission efficiency. Provided is a light-emitting device including an anode, a cathode, an EL layer positioned between the anode and the cathode; the EL layer includes a hole-transport region, a light-emitting layer, and an electron-transport region; the hole-transport region is positioned between the anode and the light-emitting layer; the electron-transport region is positioned between the cathode and the light-emitting layer; the hole-transport region contains any one of a sulfonic acid compound, a fluorine compound, and a metal oxide; the electron-transport region contains an organic compound having an electron-transport property; and an ordinary refractive index of the organic compound having an electron-transport property with respect to light with a wavelength greater than or equal to 455 nm and less than or equal to 465 nm is higher than or equal to 1.50 and lower than or equal to 1.75.

Abstract: An inexpensive light-emitting device with high emission efficiency is provided. A light-emitting device including an anode, a cathode, and an EL layer positioned between the anode and the cathode is provided. The EL layer includes a hole-transport region, a light-emitting layer, and an electron-transport region. The hole-transport region is positioned between the anode and the light-emitting layer. The electron-transport region is positioned between the cathode and the light-emitting layer. The hole-transport region contains a heteropoly acid and an organic compound having a ?-electron rich aromatic ring or contains a heteropoly acid and an organic compound having a ?-electron rich heteroaromatic ring. The electron-transport region contains an organic compound with an electron-transport property. The ordinary refractive index of the organic compound with an electron-transport property is higher than or equal to 1.50 and lower than or equal to 1.

Abstract: A light-emitting device with high emission efficiency is provided. A light-emitting device with a low driving voltage is provided. The light-emitting device includes a first electrode, a first layer over the first electrode, a second layer over the first layer, a light-emitting layer over the second layer, and a second electrode over the light-emitting layer. The first layer includes a first organic compound, and the second layer includes a second organic compound. The proportion of carbon atoms forming bonds by the sp3 hybrid orbitals to the total number of carbon atoms in the first organic compound is higher than or equal to 23 percent and lower than or equal to 55 percent. The second organic compound contains fluorine.

Abstract: To provide a light-emitting element with high emission efficiency and low driving voltage. The light-emitting element includes a guest material and a host material. A HOMO level of the guest material is higher than a HOMO level of the host material. An energy difference between the LUMO level and a HOMO level of the guest material is larger than an energy difference between the LUMO level and a HOMO level of the host material. The guest material has a function of converting triplet excitation energy into light emission. An energy difference between the LUMO level of the host material and the HOMO level of the guest material is larger than or equal to energy of light emission of the guest material.

Abstract: A novel display apparatus that is highly convenient, useful, or reliable is provided. The display apparatus includes a first electrode, a second electrode, a first unit, a second unit, and a first intermediate layer; the first unit is located between the second electrode and the first electrode; and the first unit contains a first light-emitting material EM1. The second unit is located between the second electrode and the first unit and contains a second light-emitting material EM2. The first intermediate layer is located between the second unit and the first unit.

Abstract: A composite material with a low refractive index that can be used for a light-emitting device, a light-receiving device, a light-emitting and light-receiving device, and the like is provided. The composite material includes a first organic compound and a second organic compound, the proportion of carbon atoms forming bonds by the sp3 hybrid orbitals in the total number of carbon atoms of the first organic compound is greater than or equal to 23% and less than or equal to 55%, and the second organic compound contains fluorine. Alternatively, an optical device including an anode, a cathode, and a first layer, in which the composite material is included in the first layer, is provided.

Abstract: To provide a light-emitting element in which an organic compound layer can be processed at once by a photolithography technique. A first electrode and an organic compound layer including an electron-injection layer are formed over an insulating surface. The electron-injection layer is the outermost layer of the organic compound layer and contains an organic compound having a basic skeleton and an acid dissociation constant pKa of greater than or equal to 1. A sacrificial layer and a mask are formed over the electron-injection layer and the sacrificial layer is processed into an island shape using the mask. With use of the island-shaped sacrificial layer as a mask, the organic compound layer is processed into an island shape to cover the first electrode. Part of the island-shaped sacrificial layer is removed with an acidic chemical solution to expose the electron-injection layer. A second electrode is formed to cover the electron-injection layer.

Abstract: A plurality of light-emitting elements having a structure in which an organic compound layer as a whole is processed with a photolithography technique is provided. A light-emitting element is formed over an insulating layer and includes a first electrode, a second electrode, and an organic compound layer. The organic compound layer is positioned between the first electrode and the second electrode. The organic compound layer includes a light-emitting layer and an electron-injection layer. The electron-injection layer is in contact with the second electrode, and the electron-injection layer includes an organic compound having a basic skeleton and an acid dissociation constant pKa of 1 or more. Layers included in the organic compound layer have substantially the same contour, and the organic compound layer is separated from organic compound layers of the other light-emitting elements of the plurality of light-emitting elements.

Abstract: A light-emitting device with high emission efficiency is provided. An electronic device including an anode, a cathode, and an EL layer positioned between the anode and the cathode is provided. The EL layer includes a first layer, a second layer, and a third layer; the first layer is positioned between the anode and the second layer; the third layer is positioned between the second layer and the cathode; the first layer includes an organic compound having a hole-transport property; the third layer includes an organic compound having an electron-transport property; the organic compound having a hole-transport property and the organic compound having an electron-transport property have specific structures; the ordinary refractive index of each of the organic compound having a hole-transport property and the organic compound having an electron-transport property with respect to light with a wavelength greater than or equal to 455 nm and less than or equal to 465 nm is higher than or equal to 1.

Abstract: An organic semiconductor element with low driving voltage is provided. The organic semiconductor element includes a first electrode, a second electrode, and a hole-transport layer and an active layer between the first electrode and the second electrode. The hole-transport layer includes a first hole-transport layer and a second hole-transport layer. The first hole-transport layer is closer to the substrate than the second hole-transport layer is. The first hole-transport layer and the second hole-transport layer are in contact with each other. A value obtained by subtracting GSP_slope (mV/nm) of the second hole-transport layer from GSP_slope (mV/nm) of the first hole-transport layer is less than or equal to 10 (mV/nm). Note that GSP_slope (mV/nm) is a parameter represented by V/d when surface potential and thickness of a film are V (mV) and d (nm), respectively.

Abstract: A light-emitting element having low driving voltage and high emission efficiency is provided. In the light-emitting element, a combination of a guest material and a host material forms an exciplex. The guest material is capable of converting triplet excitation energy into light emission. Light emission from the light-emitting layer includes light emission from the guest material and light emission from the exciplex. The percentage of the light emission from the exciplex to the light emission from the light-emitting layer is greater than 0 percent and less than or equal to 60 percent. The energy after subtracting the energy of light emission from the exciplex from the energy of light emission from the guest material is greater than 0 eV and less than or equal to 0.23 eV.

Abstract: Provided is a light-emitting element with high emission efficiency. The light-emitting element includes a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound, and the HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of a guest material is higher than that of the first organic compound, and the HOMO level of the guest material is lower than that of the second organic compound. The guest material has a function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound form an exciplex.

Abstract: Provided is a light-emitting element including a fluorescence-emitting material with high emission efficiency. The light-emitting element includes a pair of electrodes and an EL layer between the pair of electrodes. The EL layer includes a first organic compound, a second organic compound, and a guest material. The first organic compound has a function of emitting a thermally activated delayed fluorescence at room temperature. The guest material has a function of emitting fluorescence. A HOMO level of the first organic compound higher than or equal to a HOMO level of the second organic compound. A LUMO level of the first organic compound is lower than or equal to a LUMO level of the second organic compound.

Abstract: To increase emission efficiency of a fluorescent light-emitting element by efficiently utilizing a triplet exciton generated in a light-emitting layer. The light-emitting layer of the light-emitting element includes at least a host material and a guest material. The triplet exciton generated from the host material in the light-emitting layer is changed to a singlet exciton by triplet-triplet annihilation (TTA). The guest material (fluorescent dopant) is made to emit light by energy transfer from the singlet exciton. Thus, the emission efficiency of the light-emitting element is improved.

Abstract: A light-emitting apparatus with low power consumption is provided. A light-emitting apparatus including a first light-emitting device and a first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a layer including a material with a refractive index lower than or equal to 1.75 at 467 nm. The first color conversion layer includes a first substance capable of emission by absorbing light. Light emitted from the first light-emitting device enters the first color conversion layer.

Abstract: A near-infrared organic EL device with favorable efficiency is provided. A light-emitting device including a first electrode, a second electrode, and an EL layer is provided; in which the EL layer is positioned between the first electrode and the second electrode; in which the EL layer emits light having a peak of an emission spectrum in a wavelength range of greater than or equal to 750 nm and less than or equal to 1000 nm; in which one of the first electrode and the second electrode is an electrode having a transmitting property with respect to light with a peak wavelength of the emission spectrum of the EL layer; in which a first layer is provided in contact with a surface of the electrode having a transmitting property, which is opposite to a surface facing the EL layer; in which the first layer contains an organic compound; and in which the first layer has the local maximum value of an extinction coefficient k in the visible light region.

Abstract: An organic semiconductor device with low driving voltage is provided. The light-emitting device includes an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes a hole-transport layer and alight-emitting layer. The hole-transport layer is positioned between the anode and the light-emitting layer. The hole-transport layer is not in contact with the anode. The hole-transport layer includes a transport layer material for a light-emitting device and the GSP_slope that is a potential gradient of a surface potential of an evaporated film of the material is higher than or equal to 20 (mV/nm).

Abstract: An EL layer includes a low refractive index layer comprising an organic compound and a light-emitting layer comprising a light-emitting substance. The organic compound has an ordinary refractive index of 1.50 to 1.75 with respect to light at 455 nm to 465 nm, or an ordinary refractive index of 1.45 to 1.70 with respect to light at 633 nm. Given that a wavelength corresponding to an intensity 1/e times a maximum peak intensity in an emission spectrum of the light-emitting substance is ?n, a shortest ?n in a range of wavelengths longer than a maximum peak wavelength ?max of the light-emitting substance is ?1, and a longest ?n in a range of wavelengths shorter than ?max is ?2, a difference between ?1 and ?2 is greater than or equal to 5 nm and less than or equal to 45 nm.