Abstract: A novel optical functional device that is highly convenient, useful, or reliable is provided. A light-emitting device includes a first electrode, a second electrode, and an EL layer. The first electrode has a first transmittance; the second electrode overlaps with the first electrode. The second electrode has a second transmittance higher than the first transmittance. The EL layer is interposed between the first electrode and the second electrode and includes a first region, a second region, and a third region. The first region is interposed between the second region and the third region. The second region is interposed between the first electrode and the first region and has a first refractive index. The third region is interposed between the first region and the second electrode and has a second refractive index. The second refractive index is lower than the first refractive index. The EL layer includes a first unit, a second unit, and an intermediate layer.

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: A novel compound is provided. The compound is represented by General Formula (G1). In General formula (G1), each of Z1 to Z4 independently has a structure represented by General formula (Z-1) or General formula (Z-2). In General Formula (Z-1), each of X1 and X2 independently represents any one of an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a cycloalkyl group with a bridge structure having 7 to 10 carbon atoms, and a trialkylsilyl group having 3 to 12 carbon atoms. Moreover, each of Ar1 and Ar2 independently represents an aromatic hydrocarbon group having 6 to 13 carbon atoms, and at least one of Ar1 and Ar2 includes a substituent that is the same as X1.

Abstract: A light-emitting element includes an EL layer between a pair of electrodes. The EL layer contains a first compound and a second compound. The first compound is a phosphorescent iridium metal complex having a LUMO level of greater than or equal to ?3.5 eV and less than or equal to ?2.5 eV, and the second compound is an organic compound having a pyrimidine skeleton. The light-emitting element includes an EL layer between a pair of electrodes. The EL layer contains a first compound and a second compound. The first compound is a phosphorescent iridium metal complex having a diazine skeleton, and the second compound is an organic compound having a pyrimidine skeleton.

Abstract: A novel organic compound having an emission spectrum peak at a wavelength longer than 850 nm and an absorption spectrum peak at a wavelength longer than 600 nm is provided. The organic compound is represented by General Formula (G1). In General Formula (G1), Ar1 to Ar4 each independently represent an aryl group having 6 to 13 carbon atoms in a ring. R1 to R8 each independently represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 13 carbon atoms in a ring, and a heteroaryl group having 3 to 13 carbon atoms in a ring. Q1 and Q2 each independently represent a group having a carbazole skeleton or a group having a triarylamine skeleton and having 18 to 30 carbon atoms in a ring. Furthermore, m and n each independently represent 0 or 1.

Abstract: A triarylamine derivative represented by a general formula (G1) given below is provided. Note that in the formula, Ar represents either a substituted or unsubstituted phenyl group or a substituted or unsubstituted biphenyl group; ? represents a substituted or unsubstituted naphthyl group; ? represents either hydrogen or a substituted or unsubstituted naphthyl group; n and m each independently represent 1 or 2; and R1 to R8 each independently represent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, or a phenyl group.

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: To provide a light-emitting device with high emission efficiency and high reliability. A light-emitting layer of the light-emitting device includes a first substance emitting light from a doublet excited state based on f-d transition and a second substance that is a fluorescent substance. The longest-wavelength absorption edge among absorption edges in the absorption spectrum of the first substance is positioned at a wavelength shorter than the wavelength of the longest-wavelength absorption edge among absorption edges in the absorption spectrum of the second substance. The first substance has a short exciton lifetime and high exciton generation efficiency, and efficient energy transfer occurs between the first substance and the second substance; thus, the light-emitting device can have high emission efficiency and high reliability.

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: A light-emitting element having high emission efficiency is provided. The light-emitting element includes a first organic compound, a second organic compound, and a third organic compound. The first organic compound has a function of converting triplet excitation energy into light emission. The second organic compound is preferably a TADF material. The third organic compound is a fluorescent compound. Light emitted from the light-emitting element is obtained from the third organic compound. Triplet excitation energy in a light-emitting layer is transferred to the third organic compound by reverse intersystem crossing caused by the second organic compound or through the first organic compound.

Abstract: The transistor includes a first gate electrode, a first insulating film over the first gate electrode, an oxide semiconductor film over the first insulating film, a source electrode over the oxide semiconductor film, a drain electrode over the oxide semiconductor film, a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode, and a second gate electrode over the second insulating film. The first insulating film includes a first opening. A connection electrode electrically connected to the first gate electrode through the first opening is formed over the first insulating film. The second insulating film includes a second opening that reaches the connection electrode. The second gate electrode includes an oxide conductive film and a metal film over the oxide conductive film. The connection electrode and the second gate electrode are electrically connected to each other through the metal film.

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: A reliable light-emitting element with low driving voltage is provided. The light-emitting element includes an electron-injection layer between a cathode and a light-emitting layer. The electron-injection layer is a mixed film of a transition metal and an organic compound having an unshared electron pair. An atom of the transition metal and the organic compound form SOMO.

Abstract: An object is to provide a light-emitting element with high emission efficiency. The light-emitting element contains first to third organic compounds. The first organic compound has a function of converting triplet excitation energy into light. The second organic compound has a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton. The third organic compound is a fluorescent compound. Light emitted from the light-emitting element is light emitted from the third organic compound that receives excitation energy from the first organic compound or from an exciplex formed by the first and second organic compounds.

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: 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: To inhibit an increase in voltage of an organic semiconductor device manufactured by a method including a step of forming an aluminum oxide film over and in contact with an organic semiconductor layer. An organic semiconductor device including a first electrode, a second electrode, an organic semiconductor layer, and a buffer layer is provided. The organic semiconductor layer is positioned between the first electrode and the second electrode. The buffer layer is positioned between the organic semiconductor layer and the second electrode. A side surface of the organic semiconductor layer and a side surface of the buffer layer are substantially aligned.

Abstract: The transistor includes a first gate electrode, a first insulating film over the first gate electrode, an oxide semiconductor film over the first insulating film, a source electrode over the oxide semiconductor film, a drain electrode over the oxide semiconductor film, a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode, and a second gate electrode over the second insulating film. The first insulating film includes a first opening. A connection electrode electrically connected to the first gate electrode through the first opening is formed over the first insulating film. The second insulating film includes a second opening that reaches the connection electrode. The second gate electrode includes an oxide conductive film and a metal film over the oxide conductive film. The connection electrode and the second gate electrode are electrically connected to each other through the metal film.