Light-emitting element including a carrier transport controlling layer, light-emitting device and electronic device
View Patent ↗A light-emitting element is provided, which includes a light-emitting layer and a control layer between a first electrode and a second electrode, wherein the control layer includes a first organic compound and a second organic compound, the first organic compound is included in the control layer more than the second organic compound, the second organic compound has a property of trapping carriers having the same polarity as carriers transported by the first organic compound, and the concentration and the carrier-trapping property of the second organic compound included in the control layer satisfy certain conditions.
1. A light-emitting element comprising:
a first electrode;
a second electrode; and
a light-emitting layer and a control layer between the first electrode and the second electrode, the control layer being in contact with the light-emitting layer,
wherein:
the control layer includes a first organic compound and a second organic compound;
the first organic compound is included more than the second organic compound;
the first organic compound is an organic compound having an electron-transporting property;
a lowest unoccupied molecular orbital level (LUMO level) of the second organic compound is deeper than the lowest unoccupied molecular orbital level (LUMO level) of the first organic compound;
a value of a parameter X obtained by an expression (1) is in the range of from 5×10 −4 to 2×10 −2 ; and
X
=
1
L
{
exp
(
-
Δ
E
kT
)
}
C
3
(
1
)
ΔE is an energy difference [eV] between the LUMO level of the first organic compound and the LUMO level of the second organic compound, C is a molar fraction [dimensionless term] of the second organic compound in the control layer, L is a thickness [nm] of the control layer, k is a Boltzmann constant (=8.61×10 −5 [eV·K −1 ]), and T is a temperature (=300[K]),
wherein the second organic compound is a quinoxaline derivative.
2. The light-emitting element according to claim 1 , wherein the thickness L of the control layer is from 5 nm to 20 nm.
3. The light-emitting element according to claim 1 , wherein a carrier mobility of the first organic compound is in the range of from 10 −7 [m 2 /Vs] to 10 −3 [m 2 /Vs].
4. The light-emitting element according to claim 1 , wherein an energy difference ΔE between the LUMO level of the first organic compound and the LUMO level of the second organic compound is in the range of from 0.2 [eV] to 0.6 [eV].
5. The light-emitting element according to claim 1 , wherein the light-emitting layer has an electron-transporting property.
6. The light-emitting element according to claim 1 , wherein:
the light-emitting layer includes a third organic compound and a fourth organic compound;
the third organic compound is included more than the fourth organic compound; and
the third organic compound has an electron-transporting property.
7. The light-emitting element according to claim 1 , wherein:
the light-emitting layer includes a third organic compound and a fourth organic compound;
the third organic compound is included more than the fourth organic compound;
the third organic compound has an electron-transporting property; and
the first organic compound is different from the third organic compound.
8. A light-emitting element comprising:
a first electrode;
a second electrode; and
a light-emitting layer and a control layer between the first electrode and the second electrode,
wherein:
the control layer includes a first organic compound and a second organic compound;
the first organic compound is included more than the second organic compound;
the first organic compound is an organic compound having an electron-transporting property;
a lowest unoccupied molecular orbital level (LUMO level) of the second organic compound is deeper than the lowest unoccupied molecular orbital level (LUMO level) of the first organic compound;
a value of a parameter X obtained by an expression (1) is in the range of from 5×10 −4 to 2×10 −2 ; and
X
=
1
L
{
exp
(
-
Δ
E
kT
)
}
C
3
(
1
)
ΔE is an energy difference [eV] between the LUMO level of the first organic compound and the LUMO level of the second organic compound, C is a molar fraction [dimensionless term] of the second organic compound in the control layer, L is a thickness [nm] of the control layer, k is a Boltzmann constant (=8.61×10 −5 [eV·K −1 ]), and T is a temperature (=300[K]),
wherein the second organic compound is a quinoxaline derivative.
9. The light-emitting element according to claim 8 , wherein the thickness L of the control layer is from 5 nm to 20 nm.
10. The light-emitting element according to claim 8 , wherein a carrier mobility of the first organic compound is in the range of from 10 −7 [m 2 /Vs] to 10 −3 [cm 2 /Vs].
11. The light-emitting element according to claim 8 , wherein an energy difference ΔE between the LUMO level of the first organic compound and the LUMO level of the second organic compound is in the range of from 0.2 [eV] to 0.6 [eV].
12. The light-emitting element according to claim 8 , wherein the light-emitting layer has an electron-transporting property.
13. The light-emitting element according to claim 8 , wherein:
the light-emitting layer includes a third organic compound and a fourth organic compound;
the third organic compound is included more than the fourth organic compound; and
the third organic compound has an electron-transporting property.
14. The light-emitting element according to claim 8 , wherein:
the light-emitting layer includes a third organic compound and a fourth organic compound;
the third organic compound is included more than the fourth organic compound;
the third organic compound has an electron-transporting property; and
the first organic compound is different from the third organic compound.