Organic electroluminescent device comprising an electron buffer layer and an electron transport layer

1. An organic electroluminescent device comprising a first electrode, a second electrode facing the first electrode, a light-emitting layer between the first electrode and the second electrode, and an electron transport layer and an electron buffer layer between the light-emitting layer and the second electrode, wherein the electron buffer layer comprises a compound represented by the following formula 1, and the electron transport layer comprises a compound represented by the following formula 2:

wherein

X 1 to X 5 each independently represent CR 1 or N;

R 1 represents hydrogen, a substituted or unsubstituted (C1-C30)alkyl, a substituted or unsubstituted (C3-C30)cycloalkyl, a substituted or unsubstituted (C6-C30)aryl, a substituted or unsubstituted (5- to 30-membered)heteroaryl, a substituted or unsubstituted tri(C1-C30)alkylsilyl, a substituted or unsubstituted tri(C6-C30)arylsilyl, a substituted or unsubstituted di(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted (C1-C30)alkyldi(C6-C30)arylsilyl, a substituted or unsubstituted mono- or di-(C1-C30)alkylamino, or a substituted or unsubstituted mono- or di-(C6-C30)arylamino; or may be linked to an adjacent substituent to form a substituted or unsubstituted, mono- or polycyclic, (C3-C30) alicyclic, aromatic, or a combination of alicyclic and aromatic ring, whose carbon atom(s) may be replaced with at least one heteroatom selected from nitrogen, oxygen, and sulfur;

L represents a single bond, a substituted or unsubstituted (C6-C50)arylene, or a substituted or unsubstituted (5- to 50-membered)heteroarylene;

Ar represents a substituted or unsubstituted (C6-C50)aryl, or a substituted or unsubstituted (5- to 50-membered)heteroaryl;

Ar 1 and Ar 2 each independently represent a substituted or unsubstituted (C6-C30)aryl;

L 1 represents a naphthylene;

ring A and ring B each independently represent a benzene, a phenylbenzene, or a naphthalene, with a proviso that at least one of ring A and ring B represent naphthalene;

n represents an integer of 1 to 3; and

the heteroaryl(ene) contains at least one heteroatom selected from B, N, O, S, Si, and P.

2. The organic electroluminescent device according to claim 1 , wherein formula 1 is represented by the following formula 3 or 4:

wherein

Ar 3 and Ar 4 are identical to the definition of R 1 ; and

L, Ar, and n are as defined in claim 1 .

3. The organic electroluminescent device according to claim 1 , wherein formula 2 is represented by the following formula 5 or 6:

wherein

X 1 , L 1 , Ar 1 , and Ar 2 are as defined in claim 1 ; and

m represents 0 or 1.

4. The organic electroluminescent device according to claim 1 , wherein in formula 2, L 1 is represented by any one of the following formulae 8 to 10:

wherein

represents a bonding site.

5. The organic electroluminescent device according to claim 1 , wherein the compound represented by formula 1 is selected from the group consisting of:

6. The organic electroluminescent device according to claim 1 , wherein the compound represented by formula 2 is selected from the group consisting of:

7. The organic electroluminescent device according to claim 1 , wherein the light-emitting layer comprises a host compound and a dopant compound, the LUMO (lowest unoccupied molecular orbital) energy level of the electron buffer layer is higher than the LUMO energy level of the host compound, and the LUMO energy level of the electron transport layer is higher than the LUMO energy level of the electron buffer layer.

8. The organic electroluminescent device according to claim 1 , wherein the LUMO energy level of the electron transport layer (Ae) and the LUMO energy level of the light-emitting layer (Ah) satisfy the following equation:

Ae≤Ah+ 0.5 eV.

9. The organic electroluminescent device according to claim 1 , wherein the LUMO energy level of the electron transport layer (Ae) and the LUMO energy level of the electron buffer layer (Ab) satisfy the following equation:

Ae≤Ab+ 0.2˜0.3 eV.

10. The organic electroluminescent device according to claim 1 , wherein the electron transport layer further comprises a reductive dopant.