Light-emitting element

Abstract

To provide a multicolor light emitting element that is advantageous for practical use in a light emitting element using fluorescence emission and phosphorescence emission.SOLUTION: A light emitting element has a laminated structure of a first light emitting layer including a host material and a fluorescent emissive material, and a second light emitting layer containing two kinds of organic compounds forming an exciplex and a substance capable of converting triplet excitation energy into light emission. It is more useful to use a light emitting element in which the emission from the first light emitting layer has a peak of the emission spectrum on the shorter wavelength side than the light emitted from the second light emitting layer.SELECTED DRAWING: Figure 1

Claims

[Claim 1] Having a first electrode and a second electrode, Between the first electrode and the second electrode, there is a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer. The first light-emitting layer comprises a fluorescent light-emitting material and a host material, The singlet excitation level of the host material is higher than the singlet excitation level of the fluorescent material. The triplet excitation level of the host material is lower than the triplet excitation level of the fluorescent material. The second light-emitting layer comprises a phosphorescent material, a first organic compound, and a second organic compound. The first organic compound and the second organic compound are a combination capable of forming an excited complex. The difference between the energy value of the peak wavelength of the emission spectrum of the excited complex and the energy value of the peak wavelength of the lowest energy absorption band of the phosphorescent material is within 0.2 eV. The triplet excitation level of the host material is lower than the triplet excitation level of the first organic compound. The triplet excitation level of the host material is lower than the triplet excitation level of the second organic compound. A light-emitting element in which the emission peak from the first light-emitting layer is located on the shorter wavelength side than the emission peak from the second light-emitting layer.

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