Organic light-emitting diode including multi-layered hole transporting layer, and flat display device including the organic light-emitting diode

1. An organic light-emitting diode comprising:

a first electrode;

a second electrode facing the first electrode;

an emission layer between the first electrode and the second electrode;

a first mixed layer between the emission layer and the first electrode and comprising a first compound and a second compound;

a second mixed layer between the emission layer and the first mixed layer and comprising a third compound and a fourth compound;

a first charge generation layer between the first mixed layer and the first electrode and comprising the first compound, the second compound, and a first charge generation material;

a second charge generation layer between the first mixed layer and the second mixed layer and comprising the third compound, the fourth compound, and a second charge generation material; and

a buffer layer between the emission layer and the second mixed layer,

wherein the first compound and the third compound are each independently a compound represented by Formula 1 below, and the second compound and the fourth compound are each independently a compound represented by Formula 2 below:

wherein in Formula 1,

Ar 11 and Ar 12 are each independently a substituted or unsubstituted C 6 -C 60 arylene group;

e and f are each independently an integer of 0 to 5;

R 51 to R 58 and R 61 to R 69 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, or substituted or unsubstituted C 6 -C 60 arylthio group; and

R 59 is a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, or a pyridyl group or is a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, or a pyridyl group, of which at least one hydrogen atom is each independently substituted with a deuterium atom; a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 20 alkyl group, or a substituted or unsubstituted C 1 -C 20 alkoxy; and

wherein in Formula 2,

Ar 1 to Ar a are each independently a substituted or unsubstituted C 6 -C 60 arylene group;

a and b are each independently an integer of 0 to 5;

c is an integer of 1 to 5;

R 1 to R 5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof; a phosphoric acid group or salt thereof; a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, —Si(R 31 )(R 32 )(R 33 ), —N(R 34 )(R 35 ), or a nitrogen atom-containing group, and at least one of R 1 to R 5 is a nitrogen atom-containing group;

d is an integer of 0 to 5;

R 11 to R 23 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, —Si(R 36 )(R 37 )(R 38 ), or —N(R 39 )(R 40 ); and

R 31 to R 40 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, or a substituted or unsubstituted C 2 -C 60 heteroaryl group;

wherein the nitrogen atom-containing group is a 5-membered aromatic ring group comprising a nitrogen atom as a ring atom, a 6-membered aromatic ring group comprising a nitrogen atom as a ring atom, or a 9-membered aromatic ring group comprising a nitrogen atom as a ring atom and is formed by fusing a 5-membered aromatic group and a 6-membered aromatic group.

2. The organic light-emitting diode of claim 1 , wherein a highest occupied molecular orbital (HOMO) energy level of the second compound is 0.1 eV to 0.2 eV lower than a HOMO energy level of the first compound, and a lowest unoccupied molecular orbital (LUMO) energy level of the second compound is 0.1 eV to 0.2 eV lower than a LUMO energy level of the first compound.

3. The organic light-emitting diode of claim 1 , wherein a hole mobility of the first compound is higher than a hole mobility of the second compound.

4. The organic light-emitting diode of claim 1 , wherein the first compound and the third compound are each independently a compound represented by Formula 1A:

wherein in Formula 1A,

R 51 , R 59 , R 61 , and R 62 are the same as with respect to Formula 1.

5. The organic light-emitting diode of claim 1 , wherein the first compound and the third compound are each independently Compound 301 below:

6. The organic light-emitting diode of claim 1 , wherein the second compound and the fourth compound are each independently at least one of compounds represented by Formulae 2A to 2K below:

wherein in Formulae 2A to 2K,

Ar 1 and Ar 2 are each independently a substituted or unsubstituted C 6 -C 60 arylene group;

a and b are each independently an integer of 0 to 5;

R 1a , R 1b , and R 3 are each independently a nitrogen atom-containing group;

R 11 , R 19 and R 20 are each independently a substituted or unsubstituted C 1 -C 60 alkyl group, or a substituted or unsubstituted C 6 -C 60 aryl group;

Z 1 to Z 4 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, —Si(Q 1 )(Q 2 )(Q 3 ), or —N(Q 4 )(Q 5 ), and if x or y is 2 or more, a plurality of Z 1 or Z 2 are identical to or different from each other;

Q 1 to Q 5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, hydrazine, hydrazone, a carboxylic group or salt thereof, a sulfonic acid group or salt thereof, a phosphoric acid group or salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, or a substituted or unsubstituted C 2 -C 60 heteroaryl group;

X is an integer of 1 to 8; and

y is an integer of 1 to 3.

7. The organic light-emitting diode of claim 1 , wherein the second compound and the fourth compound are each independently at least one selected from Compounds 2, 8, 14, 15, 16, 20, 31, and 35 below:

8. The organic light-emitting diode of claim 1 , wherein the first charge generation material and the second charge generation material are each independently at least one selected from Compound 501 and 502 below:

9. The organic light-emitting diode of claim 1 , wherein a mixed weight ratio of the first compound and the second compound is in a range of 6:4 to 8:2.

10. The organic light-emitting diode of claim 1 , wherein a mixed weight ratio of the third compound and the fourth compound is in a range of 6:4 to 8:2.

11. The organic light-emitting diode of claim 1 , wherein a thickness of each of the first mixed layer and the second mixed layer is in a range of 40 nm to 60 nm.

12. The organic light-emitting diode of claim 1 , wherein an amount of the first charge generation material is in a range of 1 to 3 parts by weight based on 100 parts by weight of the first charge generation layer.

13. The organic light-emitting diode of claim 1 , wherein an amount of the second charge generation material is in a range of 1 to 3 parts by weight based on 100 parts by weight of the second charge generation layer.

14. The organic light-emitting diode of claim 1 , wherein a thickness of each of the first charge generation layer and the second charge generation layer is in a range of 10 nm to 20 nm.

15. The organic light-emitting diode of claim 1 , wherein the buffer layer comprises the compound represented by Formula 1.

16. The organic light-emitting diode of claim 1 , wherein a thickness of the buffer layer is in a range of 0.1 nm to 30 nm.

17. The organic light-emitting diode of claim 1 , wherein the first mixed layer contacts the first charge generation layer.

18. The organic light-emitting diode of claim 1 , wherein the second mixed layer contacts the second charge generation layer.

19. The organic light-emitting diode of claim 1 , wherein the organic light-emitting diode comprises at least one layer selected from a hole blocking layer, an electron transporting layer, an electron injection layer, and a functional layer having an electron transport function and an electron injection function, the at least one layer being between the emission layer and the second electrode.

20. A flat display device comprising: a transistor comprising a source, a drain, a gate, and an active layer; and the organic light-emitting diode of claim 1 ,

wherein the first electrode of the organic light-emitting diode is electrically connected to the source or the drain.