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 which has an anode, a light-emitting layer over the anode, an electron-transport layer over and in contact with the light-emitting layer, an electron-injection layer over and in contact with the electron-transport layer, and a cathode over and in contact with the electron-injection layer. The light-emitting layer has an electron-transport property, and the electron-transport layer includes an anthracene derivative. The light-emitting layer further includes a phosphorescent substance. This device structure allows the formation of a highly efficient blue-emissive light-emitting element even though the phosphorescent substance has higher triplet energy than the anthracene derivative which directly contacts with the light-emitting layer.

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 novel compound or a light-emitting element with high emission efficiency. The provided novel compound includes a bicarbazole skeleton and a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton. The provided light-emitting element includes the compound.

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 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: A novel light-emitting element or a highly reliable light-emitting element is provided. The light-emitting element includes an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes at least a light-emitting layer. The light-emitting layer includes at least a first organic compound and a second organic compound. The energy for liberating halogen from a halogen-substituted product of the first organic compound in a radical anion state and in a triplet excited state is less than or equal to 1.00 eV. The amount of halogen-substituted product in the second organic compound is not increased with an increase in driving time of the light-emitting element.

Abstract: Provided is a light-emitting element having a light-emitting layer which contains at least a host material and a plurality of guest materials, where the host material has a lower T1 level than that of at least one of the plurality of guest materials. The emission of the one of the plurality of guest materials exhibits a multicomponent decay curve, and the lifetime thereof is less than or equal to 15 ?sec, preferably less than or equal to 10 ?sec, more preferably less than or equal to 5 ?sec, where the lifetime is defined as a time for the emission to decrease in intensity to 1/100 of its initial intensity.

Abstract: Provided is a novel compound or a light-emitting element with high emission efficiency. The provided novel compound includes a bicarbazole skeleton and a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton. The provided light-emitting element includes the compound.

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: 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: Providing a light-emitting element emitting light in a broad emission spectrum. A combination of a first organic compound and a second organic compound forms an exciplex. The first organic compound has a function of converting triplet-excitation energy into light emission. The lowest triplet excitation level of the second organic compound is higher than or equal to the lowest triplet excitation level of the first organic compound, and the lowest triplet excitation level of the first organic compound is higher than or equal to the lowest triplet excitation level of the exciplex. Light emission from a light-emitting layer includes light emission from the first organic compound and light emission from the exciplex.

Abstract: A novel light-emitting element or a highly reliable light-emitting element is provided. The light-emitting element includes an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes at least a light-emitting layer. The light-emitting layer includes at least a first organic compound and a second organic compound. The energy for liberating halogen from a halogen-substituted product of the first organic compound in a radical anion state and in a triplet excited state is less than or equal to 1.00 eV. The amount of halogen-substituted product in the second organic compound is not increased with an increase in driving time of the light-emitting element.

Abstract: Provided is a novel substance that can be used in an element capable of emitting phosphorescence, a novel substance that contributes to high emission efficiency, or a novel substance that contributes to light emission with high color purity. A light-emitting element includes a pair of electrodes and an EL layer between the pair of electrodes. The EL layer includes a substance including a carbazole skeleton. The substance is bonded to a substituted or unsubstituted first arylene group through a nitrogen atom included in the carbazole skeleton. The first arylene group is bonded to a substituted or unsubstituted benzofuropyridyl group or a substituted or unsubstituted benzothienopyridyl group. The first arylene group includes 1 to 5 substituted or unsubstituted second arylene groups which are bonded to one another. The EL layer may further include a layer including an emission center substance, specifically an iridium 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: Providing a light-emitting element emitting light in a broad emission spectrum. A combination of a first organic compound and a second organic compound forms an exciplex. The first organic compound has a function of converting triplet-excitation energy into light emission. The lowest triplet excitation level of the second organic compound is higher than or equal to the lowest triplet excitation level of the first organic compound, and the lowest triplet excitation level of the first organic compound is higher than or equal to the lowest triplet excitation level of the exciplex. Light emission from a light-emitting layer includes light emission from the first organic compound and light emission from the exciplex.

Abstract: To provide a novel light-emitting element or a highly reliable light-emitting element. To provide a light-emitting device, a display device, an electronic device, and a lighting device each of which can be manufactured at a low cost. To provide a light-emitting element including an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes a light-emitting layer and an electron injection transport layer between the light-emitting layer and the cathode, and the amount of a halogen detected from a material forming the electron injection transport layer is less than or equal to 30 ppm.

Abstract: A light-emitting element that emits light with high color purity, a light-emitting element that emits light at high emission efficiency, or a light-emitting element with reduced power consumption. The light-emitting element includes a first electrode, a second electrode, and an EL layer. The first electrode is configured to reflect light. The second electrode is configured to reflect light and transmit light. The EL layer is between the first electrode and the second electrode. The EL layer includes a guest material. The guest material is configured to convert triplet excitation energy into light emission. The emission spectrum of the guest material in a dichloromethane solution has a peak in a wavelength region ranging from 440 nm to 470 nm and has a full width at half maximum of greater than or equal to 20 nm and less than or equal to 80 nm.

Abstract: A novel light-emitting material is provided. A novel orgnometallic complex is provided. An orgnometallic complex having a high carrier-transport property is provided. An orgnometallic complex having a deep HOMO level and/or a deep LUMO level is provided. An orgnometallic complex having a high charge-injection property is provided. Another object is to provide an organometallic complex that can exhibit yellow to blue phosphorescence. An organometallic complex that has a high carrier-transport property and exhibits green to blue phosphorescence is provided. An organometallic complex including a ligand having a structure of 5-(2-pyridinyl)-5H-benzimidazo[1,2-a]benzimidazole and a light-emitting material including the organometallic complex are provided.

Abstract: A light-emitting element of the present invention can have sufficiently high emission efficiency with a structure including a host material being able to remain chemically stable even if a phosphorescent compound having higher emission energy is used as a guest material. The relation between the relative emission intensity and the emission time of light emission obtained from the host material and the guest material contained in a light-emitting layer is represented by a multicomponent decay curve. The relative emission intensity of the slowest component of the multicomponent decay curve becomes 1/100 for a short time within a range where the slowest component is not interfered with by quenching of the host material (the emission time of the slowest component is preferably less than or equal to 15 ?sec); thus, sufficiently high emission efficiency can be obtained.