Abstract: The fuel cell system includes a water electrolysis device, a first gas-liquid separator, an oxygen tank, a fuel cell, a second gas-liquid separator, and a controller. When the level of water in the first gas-liquid separator becomes lower than a predetermined threshold value, the controller supplies oxygen gas having a pressure higher than the internal pressure of the first gas-liquid separator to the second gas-liquid separator and opens the first on-off valve.

Abstract: A light-emitting device with low power consumption is provided. The 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 between the anode and the cathode. The EL layer includes a layer including a material with an ordinary refractive index higher than or equal to 1.50 and lower than 1.75 with respect to light with a wavelength longer than or equal to 455 nm and shorter than or equal to 465 nm. The first color conversion layer includes a first substance that absorbs light and emits light. An ordinary refractive index of the first color conversion layer with respect to light with a wavelength longer than or equal to 455 nm and shorter than or equal to 465 nm is higher than or equal to 1.40 and lower than or equal to 2.10. The first color conversion layer is on an optical path of the light emitted from the first light-emitting device to an outside of the light-emitting apparatus.

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 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 first electrode, a second electrode, a unit, and a first layer. The unit is positioned between the first electrode and the second electrode and includes a second layer, a third layer, and a fourth layer. The second layer is positioned between the third layer and the fourth layer and contains a light-emitting material. The third layer is positioned between the second layer and the second electrode, is in contact with the second layer, and contains a first material, and an organometallic complex of an alkali metal or an organometallic complex of an alkaline earth metal. The fourth layer is positioned between the first electrode and the second layer and contains a second material. The first layer is positioned between the first electrode and the unit and contains a second material and a material having an electron acceptor property. The second material has a first refractive index.

Abstract: A novel organometallic complex with high heat resistance is provided. The organometallic complex includes a structure represented by General Formula (G1) below, in which iridium and a ligand are included, the ligand includes a pyrazine skeleton, iridium is bonded to nitrogen at the 1-position of the pyrazine skeleton, an aryl group including a cyano group as a substituent is bonded at the 5-position of the pyrazine skeleton, and each of the 3-position and the 6-position of the pyrazine skeleton is independently bonded to any one of hydrogen, an alkyl group, and an alkoxy group. (In the formula, A represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 25 carbon atoms. In addition, Ar represents an aryl group having 6 to 25 carbon atoms and at least one cyano group as a substituent. Each of R1 and R2 independently represents any one of hydrogen, an alkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms.

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: 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: 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. 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 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 organic compound having a hole-transport property and a low refractive index is provided. An organic compound represented by General Formula (G1) is provided. In the formula, Ar12 represents an aryl group having 6 to 10 carbon atoms in a ring and includes at least one branched-chain or cyclic alkyl group having 3 to 12 carbon atoms. The total number of carbon atoms of the branched-chain or cyclic alkyl group having 3 to 12 carbon atoms in Ar12 is 6 to 36. Ar11 and Ar21 each represent a substituted or unsubstituted arylene group having 6 to 13 carbon atoms in a ring. Ar22 represents a substituted or unsubstituted aryl group having 6 to 10 carbon atoms in a ring. In addition, n and m each independently represent an integer of 0 or 1. Ar1 represents a phenyl group including at least one alkyl group having 1 to 6 carbon atoms. Ar2 represents a phenyl group including at least one alkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 4 carbon atoms.

Abstract: An organic compound having a hole-transport property and a low refractive index is provided. An organic compound represented by General Formula (G1) shown below is provided. In General Formula (G1), Ar1 represents a substituted or unsubstituted arylene group having 6 to 13 carbon atoms in a ring, n represents an integer of 0 or 1, and Ar2 represents an aryl group having 6 to 10 carbon atoms in a ring and includes at least one branched-chain or cyclic alkyl group having 3 to 12 carbon atoms. The total number of carbon atoms of the branched-chain or cyclic alkyl group in Ar2 is more than or equal to 6. R1 to R4 each independently represent an alkyl group having 1 to 6 carbon atoms. R11 to R14 and R21 to R24 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Any one of R15 to R18 and any one of R25 to R28 each represent a bond directly bonded to a nitrogen atom, and the others each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

Abstract: A light-emitting device with high emission efficiency is provided. The light-emitting device includes an EL layer and a light-transmitting electrode. The EL layer includes a light-emitting layer and a low refractive index layer. The low refractive index layer is positioned between the light-emitting layer and the light-transmitting electrode. A cap layer is in contact with a surface of the light-transmitting electrode on the side opposite to the EL layer. The cap layer includes a high refractive index material having an ordinary refractive index of higher than or equal to 1.90 and lower than or equal to 2.40 and an ordinary extinction coefficient of higher than or equal to 0 and lower than or equal to 0.01. The low refractive index layer includes a low refractive index material having an ordinary refractive index of higher than or equal to 1.60 and lower than or equal to 1.70.

Abstract: To provide a light-emitting device not only including a light-emitting layer in which energy is efficiently transferred from a host material to a guest material but also having high reliability. In the light-emitting device, the light-emitting layer includes an organic compound having a specific naphthofuropyrazine skeleton as a host material and a light-emitting substance (e.g., an organometallic complex) whose T1 level (TG) is within a certain range as a guest material, thereby increasing not only the efficiency of energy transfer from the host material to the guest material but also the reliability.

Abstract: A light-emitting device with high emission efficiency is provided. The light-emitting device includes a first electrode, a second electrode, and an EL layer positioned between the first electrode and the second electrode. The EL layer includes at least a light-emitting layer, a first layer, a second layer, and a third layer. The first layer is positioned between the first electrode and the light-emitting layer. The third layer is positioned between the first layer and the light-emitting layer. The second layer is positioned between the first layer and the third layer. The first layer includes a first organic compound. The second layer includes a second organic compound. The third layer includes a third organic compound. The ordinary refractive index of the second organic compound is higher than the ordinary refractive indices of the first organic compound and the third organic compound.

Abstract: An electron-transport layer material with a low refractive index is provided. An organic compound represented by General Formula (G1) is provided. In General Formula (G1), one to three of Q1 to Q3 represent N and when one or two of Q1 to Q3 represent N, the remaining two or one of Q1 to Q3 represent CH. Furthermore, R0 represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and a group represented by Formula (G1-1). At least one of R1 to R15 represents a substituted or unsubstituted group including any one of a pyrimidinyl group, a pyrazinyl group, and a triazinyl group, and the others each independently represent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 14 carbon atoms forming a ring, and a substituted or unsubstituted pyridinyl group.

Abstract: An organic semiconductor device with low driving voltage is provided. The organic semiconductor device includes a layer containing an organic compound between a pair of electrodes. The layer containing an organic compound includes a hole-transport region. The hole-transport region includes a first layer and a second layer. The first layer is positioned between the anode and the second layer. When a potential gradient of a surface potential of an evaporated film is set as GSP (mV/nm), a value obtained by subtracting GSP of an organic compound in the second layer from GSP of an organic compound in the first layer is less than or equal to 20 (mV/nm).

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 benzofuropyrimidine derivative or benzothienopyrimidine derivative that is a novel organic compound is provided. An organic compound represented by General Formula (G1) below. Q represents oxygen or sulfur. Ar1, Ar2, Ar3, and Ar4 each independently represent an aromatic hydrocarbon ring, and the number of carbon atoms included in the aromatic hydrocarbon ring is 6 to 25. m and n are each 0 or 1. A is a group having 12 to 100 carbon atoms in total and includes one or more of a benzene ring, a naphthalene ring, a fluorene ring, a phenanthrene ring, a triphenylene ring, a heteroaromatic ring including a dibenzothiophene ring, a heteroaromatic ring including a dibenzofuran ring, a heteroaromatic ring including a carbazole ring, a benzimidazole ring, and a triphenylamine structure.