Light-emitting element, light-emitting device, electronic device, and lighting device
A novel light-emitting element is provided. Alternatively, a novel light-emitting element which can achieve both high efficiency and a long lifetime is provided. The light-emitting element includes a light-emitting layer between a pair of electrodes. The light-emitting element includes a first light-emitting layer and a second light-emitting layer. The first light-emitting layer includes a fluorescent material. The second light-emitting layer includes a phosphorescent material. A difference in peak value between a first emission spectrum of light from the first light-emitting layer and a second emission spectrum of light from the second light-emitting layer is 30 nm or less.
1. A light-emitting element comprising:
a pair of electrodes; and
a first light-emitting layer and a second light-emitting layer provided between the pair of electrodes,
wherein the first light-emitting layer comprises a fluorescent material and a first host material,
wherein the second light-emitting layer comprises a phosphorescent material,
wherein the first host material has one of an anthracene skeleton and a tetracene skeleton,
wherein a S 1 level of the first host material is higher than the S 1 level of the fluorescent material,
wherein that the T 1 level of the first host material is lower than the T 1 level of the fluorescent material,
wherein light emitted from the first light-emitting layer comprises light emitted from the fluorescent material,
wherein light emitted from the second light-emitting layer comprises light emitted from the phosphorescent material,
wherein a difference in peak wavelength between a first emission spectrum of light from the first light-emitting layer and a second emission spectrum of light from the second light-emitting layer is larger than or equal 0 nm and smaller than or equal to 30 nm, and
wherein a peak wavelength of the first emission spectrum is shorter than or equal a peak wavelength of the second emission spectrum.
2. The light-emitting element according to claim 1 ,
wherein the second light-emitting layer further comprises a second host material comprising a first organic compound and a second organic compound, and
wherein a combination of the first organic compound and the second organic compound can form an exciplex.
3. The light-emitting element according to claim 1 , wherein the first emission spectrum and the second emission spectrum each have the peak wavelength in a blue wavelength range.
4. A light-emitting device comprising:
the light-emitting element according to claim 1 ; and
a color filter.
5. A lighting device comprising:
the light-emitting element according to claim 1 ; and
a housing.
6. The light-emitting element according to claim 1 , wherein a ratio of excitons generated in the first light-emitting layer to excitons generated in the second light-emitting layer is in a range of 0.9:0.1 to 0.5:0.5.
7. A light-emitting element comprising:
a pair of electrodes; and
a first EL layer and a second EL layer provided between the pair of electrodes,
wherein the first EL layer comprises a first light-emitting layer and a second light-emitting layer,
wherein the first light-emitting layer comprises a fluorescent material and a first host material,
wherein the second light-emitting layer comprises a first phosphorescent material,
wherein the first host material has one of an anthracene skeleton and a tetracene skeleton,
wherein a S 1 level of the first host material is higher than the S 1 level of the fluorescent material,
wherein that the T 1 level of the first host material is lower than the T 1 level of the fluorescent material,
wherein the second EL layer comprises a third light-emitting layer,
wherein the third light-emitting layer comprises a second phosphorescent material,
wherein light emitted from the first light-emitting layer comprises light emitted from the fluorescent material,
wherein light emitted from the second light-emitting layer comprises light emitted from the first phosphorescent material,
wherein a difference in peak wavelength between a first emission spectrum of light from the first light-emitting layer and a second emission spectrum of light from the second light-emitting layer is larger than or equal 0 nm and smaller than or equal to 30 nm and,
wherein a peak wavelength of the first emission spectrum is shorter than or equal a peak wavelength of the second emission spectrum.
8. The light-emitting element according to claim 7 ,
wherein the second light-emitting layer further comprises a second host material comprising a first organic compound and a second organic compound, and
wherein a combination of the first organic compound and the second organic compound can form an exciplex.
9. The light-emitting element according to claim 7 , wherein the first emission spectrum and the second emission spectrum each have the peak wavelength in a blue wavelength range.
10. A light-emitting device comprising:
the light-emitting element according to claim 7 ; and
a color filter.
11. A lighting device comprising:
the light-emitting element according to claim 7 ; and
a housing.
12. The light-emitting element according to claim 7 , wherein a ratio of excitons generated in the first light-emitting layer to excitons generated in the second light-emitting layer is in a range of 0.9:0.1 to 0.5:0.5.
13. A light-emitting element comprising:
a pair of electrodes; and
a first EL layer and a second EL layer provided between the pair of electrodes,
wherein the first EL layer comprises a first light-emitting layer and a second light-emitting layer,
wherein the first light-emitting layer comprises a fluorescent material and a first host material,
wherein the second light-emitting layer comprises a first phosphorescent material,
wherein the second EL layer comprises a third light-emitting layer and a fourth light-emitting layer,
wherein the third light-emitting layer comprises a second phosphorescent material,
wherein the fourth light-emitting layer comprises a third phosphorescent material,
wherein the first host material has one of an anthracene skeleton and a tetracene skeleton,
wherein a S 1 level of the first host material is higher than the S 1 level of the fluorescent material,
wherein that the T 1 level of the first host material is lower than the T 1 level of the fluorescent material,
wherein light emitted from the first light-emitting layer comprises light emitted from the fluorescent material,
wherein light emitted from the second light-emitting layer comprises light emitted from the first phosphorescent material,
wherein a difference in peak wavelength between a first emission spectrum of light from the first light-emitting layer and a second emission spectrum of light from the second light-emitting layer is larger than or equal 0 nm and smaller than or equal to 30 nm and,
wherein a peak wavelength of the first emission spectrum is shorter than or equal a peak wavelength of the second emission spectrum.
14. The light-emitting element according to claim 13 ,
wherein the second light-emitting layer further comprises a second host material comprising a first organic compound and a second organic compound, and
wherein a combination of the first organic compound and the second organic compound can form an exciplex.
15. The light-emitting element according to claim 13 , wherein the first emission spectrum and the second emission spectrum each have the peak wavelength in a blue wavelength range.
16. A light-emitting device comprising:
the light-emitting element according to claim 13 ; and
a color filter.
17. A lighting device comprising:
the light-emitting element according to claim 13 ; and
a housing.
18. The light-emitting element according to claim 13 , wherein a ratio of excitons generated in the first light-emitting layer to excitons generated in the second light-emitting layer is in a range of 0.9:0.1 to 0.5:0.5.