Light-emitting element and light-emitting device employing the same
View Patent ↗An object is to provide a white light-emitting element which emits broad white light which is close to natural light and covers a wide wavelength range; that is, a white light-emitting element which has a broad spectrum waveform. Further, there are various different kinds of white light; however, in particular, an object is to provide a white light-emitting element which emits white light which is close to the standard white color of the NTSC. Over a substrate 100 , a second light-emitting element 110 and a first light-emitting element 120 are stacked in series. The first light-emitting element 120 exhibits a light emission spectrum having two peaks (two peaks in the blue to green wavelength range) and is disposed close to a film of light-reflecting material. The second light-emitting element 110 exhibits a light emission spectrum having a peak in the orange to red wavelength range, and is disposed in a position which is not close to the film of light-reflecting material.
1. A light-emitting element which exhibits white light emission, comprising:
a substrate having a light-transmitting property,
a first light-emitting element; and
a second light-emitting element,
wherein the first light-emitting element and the second light-emitting element are stacked in series over the substrate having a light-transmitting property;
wherein the first light-emitting element comprises a first anode, a first cathode, and a first light-emitting layer including a light-emitting organic compound, which is interposed between the first anode and the first cathode;
wherein the second light-emitting element comprises a second anode, a second cathode, and a second light-emitting layer and a third light-emitting layer which each include a light-emitting organic compound, which are interposed between the second anode and the second cathode;
wherein the first cathode is in contact with the second anode;
wherein the first light-emitting element exhibits a first light emission spectrum having a peak in a red wavelength range, and the second light-emitting element exhibits a second light emission spectrum having a peak in a blue wavelength range and a peak in a green wavelength range, and
wherein the second light-emitting layer comprises:
a host material comprising an electron transporting anthracene derivative.
2. The light-emitting element according to claim 1 , wherein the first light-emitting layer comprises:
a guest material comprising a 4H-pyran derivative; and
a host material comprising a mixture of a metal complex and a tetracene derivative.
3. The light-emitting element according to claim 1 , wherein the second light-emitting layer comprises:
a guest material comprising an anthracene derivative in which an amino group is substituted into a 2-position.
4. The light-emitting element according to claim 1 , wherein the third light-emitting layer comprises:
a guest material comprising a styryl amine derivative; and
a host material comprising an electron transporting anthracene derivative.
5. The light-emitting element according to claim 1 , wherein the first light-emitting layer comprises:
a guest material comprising {2-isopropyl-6-[2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile or {2,6-bis[2-(2,3,6,7-tetrahydro-8-methoxy-1,1,7,7-tetramethyl-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile; and
a host material comprising a mixture of tris(8-quinolinolato)aluminum and rubrene.
6. The light-emitting element according to claim 1 , wherein the second light-emitting layer comprises:
a guest material comprising N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine; and
a host material comprising 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl.
7. The light-emitting element according to claim 1 , wherein the third light-emitting layer comprises:
a guest material comprising N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine; and
a host material comprising 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole.
8. A light-emitting device comprising the light-emitting element according to claim 1 , wherein the third light-emitting layer comprises:
a host material comprising an electron transporting anthracene derivative.
9. A light-emitting element comprising:
a first light-emitting element; and
a second light-emitting element,
wherein the first light-emitting element and the second light-emitting element are stacked in series;
wherein the first light-emitting element comprises a first anode, a first cathode, and a first light-emitting layer and a second light-emitting layer which each include a light-emitting organic compound, which are interposed between the first anode and the first cathode;
wherein the second light-emitting element comprises a second anode, a second cathode, and a third light-emitting layer and a fourth light-emitting layer which each include a light-emitting organic compound, which are interposed between the second anode and the second cathode;
wherein the first light-emitting element exhibits a first light emission spectrum, and the second light-emitting element exhibits a second light emission spectrum which is different to the first light emission spectrum;
wherein the first light emission spectrum of the first light-emitting element and the second light emission spectrum of the second light-emitting element are synthesized to form white light emission, and
wherein the second light-emitting layer comprises:
a host material comprising an electron transporting anthracene derivative.
10. The light-emitting element according to claim 9 , wherein the first light-emitting layer comprises:
a guest material comprising a 4H-pyran derivative; and
a host material comprising an aromatic amine compound.
11. The light-emitting element according to claim 9 , wherein the second light-emitting layer comprises:
a guest material comprising an anthracene derivative.
12. The light-emitting element according to claim 9 , wherein the third light-emitting layer comprises:
a guest material comprising a tetracene derivative; and
a host material comprising an aromatic amine compound.
13. The light-emitting element according to claim 9 , wherein the fourth light-emitting layer comprises:
a guest material comprising a styryl amine derivative; and
a host material comprising an anthracene derivative.
14. The light-emitting element according to claim 9 , wherein the first light-emitting layer comprises:
a guest material comprising {2,6-bis[2-(2,3,6,7-tetrahydro-8-methoxy-1,1,7,7-tetramethyl-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile; and
a host material comprising 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl.
15. The light-emitting element according to claim 9 , wherein the second light-emitting layer comprises:
a guest material comprising 9,10-bis{4-[N-(4-diphenylamino)phenyl-N-phenyl]aminophenyl}-2-tert-butylanthracene; and
a host material comprising 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole.
16. The light-emitting element according to claim 9 , wherein the third light-emitting layer comprises:
a guest material comprising rubrene; and
a host material comprising 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl.
17. The light-emitting element according to claim 9 , wherein the fourth light-emitting layer comprises:
a guest material comprising N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′diphenylstilbene-4,4′-diamine; and
a host material comprising 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole.
18. The light-emitting element according to claim 9 , wherein the light-emitting element exhibits white light emission having a light emission spectrum with a trapezoidal shape.
19. A light-emitting device comprising the light-emitting element according to claim 9 , further comprising a color filter.
20. A light-emitting device comprising the light-emitting element according to claim 9 , wherein the third light-emitting layer comprises:
a host material comprising an electron transporting anthracene derivative.