Organic light emitting diode
An organic light emitting diode includes a first electrode, a hole transport region disposed on the first electrode, an emission layer disposed on the hole transport region, an electron transport region disposed on the emission layer, and a second electrode disposed on the electron transport region. The hole transport region includes a first hole transport layer which is directly disposed on the lower portion of the emission layer and has a first refractive index, and a second hole transport layer which is disposed on the lower portion of the first hole transport layer and has a second refractive index, thereby exhibiting an improved luminous efficiency characteristic.
1. An organic light emitting diode comprising:
a first electrode;
a hole transport region disposed on the first electrode;
an emission layer disposed on the hole transport region;
an electron transport region disposed on the emission layer; and
a second electrode disposed on the electron transport region,
wherein the hole transport region comprises:
a first hole transport layer having a first refractive index; and
a second hole transport layer having a second refractive index greater than the first refractive index and being disposed under the first hole transport layer,
wherein the first hole transport layer comprises a fluorene compound represented by Formula 1 below:
wherein, in Formula 1 above,
R 1 and R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms,
n is an integer of 1 to 3, and
Ar 1 to Ar 4 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted amino group, a substituted or unsubstituted aryl group having 6 to 60 carbon atoms, a substituted or unsubstituted heterocyclic group having 2 to 60 carbon atoms, or are bonded to an adjacent group to form a ring, and
wherein R 1 and R 2 are each independently an unsubstituted n-butyl group or a n-pentyl group substituted with CF 3 , when n is 1.
2. The organic light emitting diode of claim 1 , wherein the first hole transport layer is directly disposed under the emission layer.
3. The organic light emitting diode of claim 1 , wherein a ratio of a thickness T 1 of the first hole transport layer and a thickness T 2 of the second hole transport layer satisfies a relationship of Expression 1 below:
1≤ T 2 /T 1 ≤3. [Expression 1]
4. The organic light emitting diode of claim 1 , wherein a difference between the first refractive index and the second refractive index is at least 0.2.
5. The organic light emitting diode of claim 4 , wherein the first refractive index is from 1.2 to 1.7, and the second refractive index is from 1.7 to 1.9.
6. The organic light emitting diode of claim 1 , wherein the fluorene compound is any one among the compounds represented by Compound Group 1 below:
7. The organic light emitting diode of claim 1 ,
wherein the second hole transport layer comprises a compound represented by Formula 2 below:
wherein, in Formula 2 above,
Ar 1 and Ar 2 are a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or bonded to an adjacent group to form a ring,
a to c are each independently an integer of 0 to 5,
L 1 and L 2 are each independently a substituted or unsubstituted cycloalkylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted heterocycloalkylene group having 2 to 10 ring-forming carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 60 ring-forming carbon atoms,
L 3 is a substituted or unsubstituted cycloalkyl group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 2 to 10 ring-forming carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 ring-forming carbon atoms,
p and s are each independently an integer of 0 to 3,
q and r are each independently an integer of 0 to 4, and
R 3 to R 7 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxy group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, a substituted or unsubstituted alkyl group having 1 to 60 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 3 to 60 ring-forming carbon atoms, a substituted or unsubstituted aryl group having 6 to 60 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 ring-forming carbon atoms.
8. The organic light emitting diode of claim 7 , wherein the compound represented by Formula 2 above is any one among the compounds represented by Compound Group 2 below:
9. The organic light emitting diode of claim 1 , wherein the hole transport region further comprises a third hole transport layer disposed under the second hole transport layer, and the third hole transport layer comprises a p-dopant.
10. The organic light emitting diode of claim 1 , wherein a difference of a refractive index between the emission layer and the first hole transport layer is at least 0.2.
11. An organic light emitting diode comprising:
a first electrode;
a hole transport region disposed on the first electrode;
an emission layer disposed on the hole transport region;
an electron transport region disposed on the emission layer; and
a second electrode disposed on the electron transport region,
wherein the hole transport region comprises a plurality of hole transport layers having different refractive indexes, and
a layer, among the plurality of the hole transport layers, which is adjacent to the emission layer comprises a fluorene compound represented by Formula 1 below:
wherein, in Formula 1 above,
R 1 and R 2 are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms,
n is an integer of 1 to 3, and
Ar 1 to Ar 4 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted amino group, a substituted or unsubstituted aryl group having 6 to 60 carbon atoms, a substituted or unsubstituted heterocyclic group having 2 to 60 carbon atoms, or are bonded to an adjacent group to form a ring, and
wherein R 1 and R 2 are each independently an unsubstituted n-butyl group or a n-pentyl group substituted with CF 3 , when n is 1.
12. The organic light emitting diode of claim 11 , wherein the hole transport region comprises:
a first hole transport layer having a first refractive index; and
a second hole transport layer which has a second refractive index greater than the first refractive index and is disposed under the first hole transport layer.
13. The organic light emitting diode of claim 12 , wherein a ratio of a thickness T 1 of the first hole transport layer and a thickness T 2 of the second hole transport layer satisfies a relationship of Expression 1 below:
1≤ T 2 /T 1 ≤3. [Expression 1]
14. The organic light emitting diode of claim 12 , wherein a minimum value of a difference between the first refractive index and the second refractive index is 0.2.
15. The organic light emitting diode of claim 14 , wherein the first refractive index is from 1.2 to 1.7, and the second refractive index is from 1.7 to 1.9.
16. The organic light emitting diode of claim 12 , wherein the second hole transport layer comprises a compound represented by Formula 2 below:
wherein, in Formula 2 above,
Ar 1 and Ar 2 are a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or bonded to an adjacent group to form a ring,
a to c are each independently an integer of 0 to 5,
L 1 and L 2 are each independently a substituted or unsubstituted cycloalkylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted heterocycloalkylene group having 2 to 10 ring-forming carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 60 ring-forming carbon atoms,
L 3 is a substituted or unsubstituted cycloalkyl group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 2 to 10 ring-forming carbon atoms, a substituted or unsubstituted cycloalkenyl group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 ring-forming carbon atoms,
p and s are each independently an integer of 0 to 3,
q and r are each independently an integer of 0 to 4, and
R 3 to R 7 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxy group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, a substituted or unsubstituted alkyl group having 1 to 60 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having 3 to 60 ring-forming carbon atoms, a substituted or unsubstituted aryl group having 6 to 60 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 ring-forming carbon atoms.
17. The organic light emitting diode of claim 12 , wherein the hole transport region further comprises a third hole transport layer disposed under the second hole transport layer, and the third hole transport layer comprises a p-dopant.