Light-emitting device, display apparatus, and electronic system
A light-emitting device includes a cathode, an anode, a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color, a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color, and an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material different from the first material. The light-emitting device satisfies inequality (1): LL A −LL B ≧0.4 [eV] (1) wherein LL A [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL B [eV] is the energy level of the lowest unoccupied molecular orbital of the second material.
1. A light-emitting device comprising:
a cathode;
an anode;
a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color;
a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color; and
an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material different from the first material;
wherein the light-emitting device satisfies inequality (1):
LL A −LL B ≧0.4[eV] (1)
wherein LL A [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL B [eV] is the energy level of the lowest unoccupied molecular orbital of the second material.
2. The light-emitting device according to claim 1 , wherein
the second light-emitting layer contains a light-emitting material and a host material that supports the light-emitting material; and
the light-emitting device satisfies inequality (2):
LL D −LL B ≧0.3[eV] (2)
wherein LL D [eV] is the energy level of the lowest unoccupied molecular orbital of the host material.
3. The light-emitting device according to claim 1 , wherein
the second light-emitting layer contains a light-emitting material and a host material that supports the light-emitting material; and
the light-emitting device satisfies inequality (3):
| LL A −LL D |≦0.2[eV] (3)
wherein LL D [eV] is the energy level of the lowest unoccupied molecular orbital of the host material.
4. The light-emitting device according to claim 1 , wherein the light of the second color has a shorter wavelength than the light of the first color.
5. The light-emitting device according to claim 1 , wherein the first material has a higher electron mobility than the second material.
6. The light-emitting device according to claim 1 , further comprising a third light-emitting layer that is disposed between the first light-emitting layer and the anode or between the second light-emitting layer and the cathode and that emits light of a third color different from the first and second colors.
7. A display apparatus comprising the light-emitting device according to claim 1 .
8. An electronic system comprising the display apparatus according to claim 7 .
9. A light-emitting device comprising:
a cathode;
an anode;
a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color, the first light-emitting layer containing a first light-emitting material that emits the light of the first color and a first host material that supports the first light-emitting material as a guest material;
a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color; and
an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material having a higher hole mobility than the first material;
wherein the light-emitting device satisfies inequalities (4) and (5):
| HL B −HL C |<|HL A −HL C | (4)
| HL A −HL C |≧0.3[eV] (5)
wherein HL A [eV] is the energy level of the highest occupied molecular orbital of the first material, HL B [eV] is the energy level of the highest occupied molecular orbital of the second material, and HL C [eV] is the energy level of the highest occupied molecular orbital of the first host material.
10. The light-emitting device according to claim 9 , wherein the second material and the first host material satisfy inequality (6):
| HL B −HL C |≦0.2[eV] (6).
11. The light-emitting device according to claim 9 , wherein the first material has a higher electron mobility than the second material.
12. The light-emitting device according to claim 9 , wherein the light of the second color has a shorter wavelength than the light of the first color.
13. The light-emitting device according to claim 9 , wherein the light-emitting device satisfies inequality (7):
LL A −LL B ≧0.4[eV] (7)
wherein LL A [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL B [eV] is the energy level of the lowest unoccupied molecular orbital of the second material.
14. The light-emitting device according to claim 9 , wherein
the second light-emitting layer contains a second light-emitting material that emits the light of the second color and a second host material that supports the second light-emitting material; and
the light-emitting device satisfies inequality (8):
| LL A −LL D |≦0.2[eV] (8)
wherein LL A [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL D [eV] is the energy level of the lowest unoccupied molecular orbital of the second host material.
15. The light-emitting device according to claim 9 , further comprising a third light-emitting layer that is disposed between the first light-emitting layer and the anode or between the second light-emitting layer and the cathode and that emits light of a third color different from the first and second colors.
16. A display apparatus comprising the light-emitting device according to claim 9 .
17. An electronic system comprising the display apparatus according to claim 16 .