Abstract: A light-emitting layer, which is a stack of a first light-emitting layer and a second light-emitting layer, is provided between an anode and a cathode. The first light-emitting layer is formed on the anode side and contains a first light-emitting substance converting triplet excitation energy into light emission, a first organic compound having an electron-transport property, and a second organic compound having a hole-transport property. The second light-emitting layer contains a second light-emitting substance converting triplet excitation energy into light emission, the second organic compound, and a third organic compound having an electron-transport property. The first organic compound has a higher LUMO level than the third organic compound. The first light-emitting substance emits light with a wavelength shorter than that of light emitted from the second light-emitting substance. The first and the second organic compounds form an exciplex. The second and the third organic compounds form an exciplex.

Abstract: Provided is a light-emitting element in which an adverse effect by halides in an EL layer is suppressed and which can be provided with low cost. The light-emitting element including at least two layers between an anode and a light-emitting layer. One of the two layers which is closer to the anode has higher concentration of halides and halogen elements than the other layer closer to the light-emitting layer.

Abstract: Provided as a novel substance is a long-lifetime organometallic iridium complex emitting yellow light with high emission efficiency. The organometallic iridium complex is represented by General Formula (G1) and has a structure in which a phenyl group whose 2-position and 6-position are each substituted by an alkyl group is bonded to the 4-position of pyrimidine. In General Formula (G1), R1 and R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

Abstract: To provide a light-emitting element which uses a fluorescent material as a light-emitting substance and has higher luminous efficiency. To provide a light-emitting element which includes a mixture of a thermally activated delayed fluorescent substance and a fluorescent material. By making the emission spectrum of the thermally activated delayed fluorescent substance overlap with an absorption band on the longest wavelength side in absorption by the fluorescent material in an S1 level of the fluorescent material, energy at an S1 level of the thermally activated delayed fluorescent substance can be transferred to the S1 of the fluorescent material. Alternatively, it is also possible that the S1 of the thermally activated delayed fluorescent substance is generated from part of the energy of a T1 level of the thermally activated delayed fluorescent substance, and is transferred to the S1 of the fluorescent material.

Abstract: A light-emitting element having high external quantum efficiency is provided. A light-emitting element having a long lifetime is provided. A light-emitting element includes a light-emitting layer between a pair of electrodes. The light-emitting layer contains at least a phosphorescent compound, a first organic compound (host material) having an electron-transport property, and a second organic compound (assist material) having a hole-transport property. The light-emitting layer has a stacked-layer structure including a first light-emitting layer and a second light-emitting layer, and the first light-emitting layer contains a higher proportion of the second organic compound than the second light-emitting layer. In the light-emitting layer (the first light-emitting layer and the second light-emitting layer), a combination of the first organic compound and the second organic compound forms an exciplex.

Abstract: As a novel substance having a novel skeleton, a novel organometallic complex that can emit phosphorescence in the green to red wavelength region and has high emission efficiency and a high yield of synthesis is provided. One embodiment of the present invention is an organometallic complex in which a diketone having a five-membered or six-membered alicyclic structure composed of carbon and hydrogen is a ligand. In the formula, L represents a bidentate aromatic ligand and has at least a bond between carbon of an aromatic ring in the aromatic ligand and Ir. X represents a five-membered or six-membered alicycle composed of carbon and hydrogen. Further, R1 represents a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms.

Abstract: As a novel substance having a novel skeleton, an organometallic complex with high emission efficiency which achieves improved color purity by a reduction of half width of an emission spectrum is provided. One embodiment of the present invention is an organometallic complex in which a ?-diketone and a six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom are ligands. In General Formula (G1), X represents a substituted or unsubstituted six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom. Further, R1 to R4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

Abstract: Provided is a novel heterocyclic compound, a novel heterocyclic compound that can be used in a light-emitting element, or a highly reliable light-emitting device, electronic device, and lighting device in each of which the light-emitting element using the novel heterocyclic compound is used. One embodiment of the present invention is a heterocyclic compound represented by General Formula (G1). In General Formula (G1), each of A1 and A2 independently represents nitrogen or carbon bonded to hydrogen, and at least one of A1 and A2 represents nitrogen; Ar represents a substituted or unsubstituted arylene group having 6 to 18 carbon atoms; B represents a substituted or unsubstituted fluorenyl group; and R1 represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 13 carbon atoms.

Abstract: A novel method includes a synthetic pathway in which ?-diketone and a 1-(haloaryl)ethane-1,2-diamine derivative are cyclized to each other to form a 2-(haloaryl)pyrazine derivative. Further, a 2-arylpyrazine derivative having an aryl group or a heteroaryl group as a substituent is synthesized by coupling the 2-(haloaryl)pyrazine derivative obtained by the above synthetic pathway and an arylboronic acid or a heteroarylboronic acid. The 2-arylpyrazine derivative obtained by the novel method is useful for a light-emitting element, a light-emitting device, an electronic device, or a lighting device with high emission efficiency.

Abstract: To provide a novel compound which can be used as a host material in which a light-emitting substance is dispersed. To provide a light-emitting element having a long lifetime. A compound represented by General Formula (G0). In the formula, A1 represents a dibenzo[f,h]quinoxalinyl group, A2 represents a benzo[b]naphtho[2,3-d]furanyl group, and Ar represents an arylene group having 6 to carbon atoms. The dibenzo[f,h]quinoxalinyl group, the benzo[b]naphtho[2,3-d]furanyl group, and the arylene group are separately unsubstituted or substituted by any one of an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 13 carbon atoms.

Abstract: A light-emitting element which has low driving voltage and high emission efficiency is provided. The light-emitting element includes, between a pair of electrodes, a hole-transport layer and a light-emitting layer over the hole-transport layer. The light-emitting layer contains a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a light-emitting third organic compound converting triplet excitation energy into light emission. A combination of the first organic compound and the second organic compound forms an exciplex. The hole-transport layer contains at least a fourth organic compound whose HOMO level is lower than or equal to that of the second organic compound and a fifth organic compound whose HOMO level is higher than that of the second organic compound.

Abstract: A novel heterocyclic compound is provided. A novel heterocyclic compound that can be used for a light-emitting element is provided. A novel heterocyclic compound that can improve the reliability of a light-emitting element when used for a light-emitting element is provided. A light-emitting element, a light-emitting device, an electronic appliance, or a lighting device which includes the novel heterocyclic compound and is highly reliable is provided. One embodiment of the present invention is a heterocyclic compound represented by a general formula (G0). In the general formula (G0), A represents a dibenzo[f,h]quinoxalinyl group, B represents a substituted or unsubstituted fluorenyl group, and Ar represents a substituted or unsubstituted arylene group having 6 to 25 carbon atoms.

Abstract: To provide a novel compound which can be used as a host material in which a light-emitting substance is dispersed. To provide a light-emitting element having a long lifetime. A compound represented by General Formula (G0). In the formula, A represents any one of a substituted or unsubstituted dibenzothiophenylene group and a substituted or unsubstituted dibenzofuranylene group, X represents a substituted or unsubstituted fluorenyl group, E represents a substituted or unsubstituted dibenzo[f,h]quinoxalinyl group, and Ar represents a substituted or unsubstituted arylene group having 6 to 30 carbon atoms.

Abstract: A light-emitting element which has low driving voltage and high emission efficiency is provided. The light-emitting element includes, between a pair of electrodes, a hole-transport layer and a light-emitting layer over the hole-transport layer. The light-emitting layer contains a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a light-emitting third organic compound converting triplet excitation energy into light emission. A combination of the first organic compound and the second organic compound forms an exciplex. The hole-transport layer is formed using two or more kinds of organic compounds and contains at least the second organic compound.

Abstract: A multicolor light-emitting element using fluorescence and phosphorescence, which has a small number of manufacturing steps owing to a relatively small number of layers to be formed and is advantageous for practical application can be provided. In addition, a multicolor light-emitting element using fluorescence and phosphorescence, which has favorable emission efficiency is provided. A light-emitting element which includes a light-emitting layer having a stacked-layer structure of a first light-emitting layer exhibiting light emission from a first exciplex and a second light-emitting layer exhibiting phosphorescence is provided.

Abstract: A light-emitting layer, which is a stack of a first light-emitting layer and a second light-emitting layer, is provided between an anode and a cathode. The first light-emitting layer is formed on the anode side and contains a first light-emitting substance converting triplet excitation energy into light emission, a first organic compound having an electron-transport property, and a second organic compound having a hole-transport property. The second light-emitting layer contains a second light-emitting substance converting triplet excitation energy into light emission, the first organic compound, and a third organic compound having a hole-transport property. The second organic compound has a lower HOMO level than the third organic compound. The first light-emitting substance emits light with a wavelength shorter than that of light emitted from the second light-emitting substance. The first and the second organic compounds form an exciplex. The first and the third organic compounds form an exciplex.

Abstract: A light-emitting element having high external quantum efficiency is provided. A light-emitting element having a long lifetime is provided. A light-emitting element includes a light-emitting layer between a pair of electrodes. The light-emitting layer contains at least a phosphorescent compound, a first organic compound (host material) having an electron-transport property, and a second organic compound (assist material) having a hole-transport property. The light-emitting layer has a stacked-layer structure including a first light-emitting layer and a second light-emitting layer, and the first light-emitting layer contains a higher proportion of the second organic compound than the second light-emitting layer. In the light-emitting layer (the first light-emitting layer and the second light-emitting layer), a combination of the first organic compound and the second organic compound forms an exciplex.

Abstract: A light-emitting element with high emission efficiency is provided. A light-emitting element with a long lifetime is provided. The light-emitting element includes an anode; a hole-transport layer over the anode, containing a hole-transport compound and a compound; a light-emitting layer over the hole-transport layer, containing a host material and a guest material; and a cathode over the light-emitting layer. The host material is an electron-transport compound. The guest material and the compound are each independently a phosphorescent compound or a thermally activated delayed fluorescence material. A peak of an emission spectrum of the compound is on a shorter wavelength side than a peak of an emission spectrum of the guest material. Only the guest material emits light.

Abstract: A new light-emitting device utilizing phosphorescence is provided. Further, an electronic device and a lighting device which utilize phosphorescence are provided. One embodiment of the present invention is a light-emitting device including a phosphorescent organometallic iridium complex comprising iridium and either pyrimidine having an aryl group at the 4-position or 1,3,5-triazine having an aryl group at the 2-position. One of nitrogen in the pyrimidine or 1,3,5-triazine is coordinated to the iridium. Also, each of the pyrimidine and 1,3,5-triazine has a substituent such as an alkyl group or an aryl group. Further the ortho position of the aryl group which is bonded to the 4-position of the pyrimidine or the 2-position of the 1,3,5-triazine is bonded to the iridium.

Abstract: As a novel substance having a novel skeleton, an organometallic complex with high emission efficiency which achieves improved color purity by a reduction of half width of an emission spectrum is provided. One embodiment of the present invention is an organometallic complex in which a ?-diketone and a six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom are ligands. In General Formula (G1), X represents a substituted or unsubstituted six-membered heteroaromatic ring including two or more nitrogen atoms inclusive of a nitrogen atom that is a coordinating atom. Further, R1 to R4 each represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.