Organic electroluminescence device

1. An organic electroluminescence device comprising:

a first electrode;

a hole transport region disposed on the first electrode;

an exciton diffusion layer disposed on the hole transport region and comprising a first host;

an emission layer disposed on the exciton diffusion layer and comprising a second host, a third host, and a phosphorescent dopant;

an electron transport region disposed on the emission layer; and

a second electrode disposed on the electron transport region, wherein

a thickness of the exciton diffusion layer is less than or equal to a triplet exciton diffusion length of the first host, and

the first host is represented by Formula 1:

wherein in Formula 1,

L 1 is a substituted or unsubstituted ring-forming arylene group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroarylene group having 2 to 30 carbon atoms,

R a1 to R a4 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

m1 is 1 or 2; and

n1 to n4 are each independently an integer from 0 to 5.

2. The organic electroluminescence device of claim 1 , wherein an absolute value of a highest occupied molecular orbital (HOMO) energy level of the first host is in a range of about 4.7 eV to about 5.1 eV.

3. The organic electroluminescence device of claim 1 , wherein

an absolute value of a difference between a highest occupied molecular orbital (HOMO) energy level of the first host and a highest occupied molecular orbital (HOMO) energy level of the second host is in a range of about 0.2 eV to about 1.5 eV, and

an absolute value of a difference between the highest occupied molecular orbital (HOMO) energy level of the first host and a highest occupied molecular orbital (HOMO) energy level of the third host is in a range of about 0.2 eV to about 1.5 eV.

4. The organic electroluminescence device of claim 1 , wherein the hole transport region comprises:

a hole injection layer disposed on the first electrode;

a hole transport layer disposed on the hole injection layer; and

an electron blocking layer disposed on the hole transport layer.

5. The organic electroluminescence device of claim 1 , wherein the phosphorescent dopant comprises an organometallic complex containing Pt as a central metal atom.

6. The organic electroluminescence device of claim 1 , wherein

L 1 in Formula 1 is represented by one of Formula 2-1 to Formula 2-3:

 and

in Formula 2-1 to Formula 2-3,

* indicates a binding site to a neighboring atom.

7. The organic electroluminescence device of claim 1 , wherein the second host is represented by one of Formula 3-1 to Formula 3-4:

wherein in Formula 3-1 to Formula 3-4,

R b1 and R b2 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted phosphine oxide group, a substituted or unsubstituted silyl group, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms, or are combined with an adjacent group to form a ring,

L 2 is a direct linkage, a substituted or unsubstituted ring-forming arylene group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroarylene group having 2 to 30 carbon atoms,

Ar 1 is a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted ring-forming hydrocarbon ring group having 4 to 30 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms, or combined with an adjacent group to form a ring,

R b3 to R b6 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted silyl group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

X is O or S,

R b7 and R b8 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted phosphine oxide group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

R b9 is a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

R b10 and R b11 are each independently a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

m2 is an integer from 0 to 4,

n11, n12, and n17 to n19 are each independently an integer from 0 to 4, and

n13 to n16 are each independently an integer from 0 to 5.

8. The organic electroluminescence device of claim 1 , wherein the third host is represented by Formula 4:

wherein in Formula 4,

Ar 2 to Ar 4 are each independently a direct linkage, a substituted or unsubstituted ring-forming arylene group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroarylene group having 2 to 30 carbon atoms, and

R c1 to R c3 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted amine group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms.

9. The organic electroluminescence device of claim 1 , wherein the phosphorescent dopant is represented by Formula 5:

MT 1 (T 2 ) d   [Formula 5]

wherein in Formula 5,

M is Pt,

T 1 is a group represented by Formula 5-1 or Formula 5-2,

T 2 is monovalent ligand, and

d is 0 or 1:

wherein in Formula 5-1 and Formula 5-2,

X 1 to X 4 are each independently N or C,

A1 to A4 are each independently a substituted or unsubstituted ring-forming monocyclic or polycyclic hydrocarbon ring group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming monocyclic or polycyclic heterocyclic group having 2 to 30 carbon atoms,

L 3 to L 5 are each independently a direct linkage, O, or S, and

* 1 to * 4 are each independently a binding site to M.

10. The organic electroluminescence device of claim 9 , wherein A1 to A4 are each independently represented by one of Formula 6-1 to Formula 6-6:

wherein in Formula 6-1 to 6-6,

R e1 to R e8 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms, or are combined with an adjacent group to form a ring,

n31 and n35 are each independently an integer from 0 to 3,

n32, n33, and n37 are each independently an integer from 0 to 2,

n34 and n36 are each independently an integer from 0 to 4,

—* indicates a binding position to a Pt atom, and

 indicates a binding position to an adjacent group.

11. The organic electroluminescence device of claim 1 , wherein the first host is one selected from Compound Group 1:

12. The organic electroluminescence device of claim 1 , wherein the second host is one selected from Compound Group 2:

13. The organic electroluminescence device of claim 1 , wherein the third host is one selected from Compound Group 3 below:

[Compound Group 3]

14. The organic electroluminescence device of claim 1 , wherein the phosphorescent dopant is one selected from Compound Group 4 below:

15. The organic electroluminescence device of claim 1 , wherein a content of the phosphorescent dopant is in a range of about 10 wt % to about 16 wt % based on the total weight of the second host, the third host, and the phosphorescent dopant.

16. An organic electroluminescence device comprising:

a first electrode;

a hole injection layer disposed on the first electrode;

a hole transport layer disposed on the hole injection layer;

an electron blocking layer disposed on the hole transport layer;

an exciton diffusion layer disposed on the electron blocking layer and comprising a first host that transports holes;

an emission layer disposed on the exciton diffusion layer and comprising:

a second host that transports holes;

a third host that transports electrons; and

a phosphorescent dopant comprising Pt;

an electron transport layer disposed on the emission layer;

an electron injection layer disposed on the electron transport layer; and

a second electrode disposed on the electron injection layer;

wherein an absolute value of a highest occupied molecular orbital (HOMO) energy level of the first host is in a range of about 4.7 eV to about 5.1 eV.

17. The organic electroluminescence device of claim 16 , wherein the first host is represented by Formula 1:

wherein in Formula 1,

L 1 is a substituted or unsubstituted ring-forming arylene group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroarylene group having 2 to 30 carbon atoms,

R a1 to R a4 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted ring-forming aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted ring-forming heteroaryl group having 2 to 30 carbon atoms,

m1 is 1 or 2; and

n1 to n4 are each independently an integer from 0 to 5.

18. The organic electroluminescence device of claim 16 , wherein a thickness of the exciton diffusion layer is less than or equal to a triplet exciton diffusion length of the first host.

19. The organic electroluminescence device of claim 16 , wherein:

an absolute value of a difference between the highest occupied molecular orbital (HOMO) energy level of the first host and the highest occupied molecular orbital (HOMO) energy level of the second host is in a range of about 0.2 eV to about 1.5 eV; and

an absolute value of a difference between the highest occupied molecular orbital (HOMO) energy level of the first host and the highest occupied molecular orbital (HOMO) energy level of the third host is in a range of about 0.2 eV to about 1.5 eV.