Light-emitting element

Abstract

This invention provides a light-emitting element with high external quantum efficiency. Furthermore, this invention provides a light-emitting element with long lifetime. The light-emitting element includes: a light-emitting layer comprising a phosphorescent compound, a first organic compound, and a second organic compound between a pair of electrodes, wherein the combination of the first organic compound and the second organic compound forms an excimer complex. This light-emitting element achieves high energy transfer efficiency by utilizing the overlap between the emission spectrum of the excimer complex and the absorption spectrum of the phosphorescent compound for energy transfer. Therefore, a light-emitting element with high external quantum efficiency can be realized.

Claims

1. A light-emitting element, comprising: A pair of electrodes; The light-emitting layer between the pair of electrodes comprises a first organic compound, a second organic compound, and a phosphorescent compound, wherein the first organic compound and the second organic compound form an excimer complex, wherein the energy difference between the peak energy of the emission spectrum of the excimer complex and the peak energy of the absorption band on the lowest energy side of the absorption spectrum of the phosphorescent compound is within 0.2 eV, wherein the first organic compound is a carbazole compound, and wherein the T1 energy levels of the first organic compound and the second organic compound are higher than the T1 energy level of the phosphorescent compound.

2. A light-emitting element, comprising: A pair of electrodes; The light-emitting layer between the pair of electrodes comprises a first organic compound, a second organic compound, and a phosphorescent compound, wherein the first organic compound and the second organic compound form an excimer complex, wherein the energy difference between the peak energy of the emission spectrum of the excimer complex and the peak energy of the absorption band on the lowest energy side of the absorption spectrum of the phosphorescent compound is within 0.1 eV, wherein the first organic compound is a carbazole compound, and wherein the T1 energy levels of the first organic compound and the second organic compound are higher than the T1 energy level of the phosphorescent compound.

3. A light-emitting element, comprising: A pair of electrodes; The light-emitting layer between the pair of electrodes comprises a first organic compound, a second organic compound, and an iridium complex, wherein the first organic compound and the second organic compound form an excimer complex, wherein the energy difference between the peak energy of the emission spectrum of the excimer complex and the peak energy of the absorption band on the lowest energy side of the absorption spectrum of the iridium complex is within 0.2 eV, wherein the first organic compound is a carbazole compound, and wherein the T1 energy levels of the first organic compound and the second organic compound are higher than the T1 energy level of the iridium complex.

4. A light-emitting element, comprising: A pair of electrodes; The light-emitting layer between the pair of electrodes comprises a first organic compound, a second organic compound, and an iridium complex, wherein the first organic compound and the second organic compound form an excimer complex, wherein the energy difference between the peak energy of the emission spectrum of the excimer complex and the peak energy of the absorption band on the lowest energy side of the absorption spectrum of the iridium complex is within 0.1 eV, wherein the first organic compound is a carbazole compound, and wherein the T1 energy levels of the first organic compound and the second organic compound are higher than the T1 energy level of the iridium complex.

5. A light-emitting element according to any one of claims 1 to 4, wherein, The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted.

6. A light-emitting element according to any one of claims 1 to 4, wherein, The first organic compound is a carbazole compound in which two carbazole rings are linked together at the 3-position.

7. A light-emitting device comprising a light-emitting element according to any one of claims 1 to 4.

8. A lighting device including the light-emitting device according to claim 7.

9. An electronic device including the light-emitting device according to claim 7.

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