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

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
• X1 to X5 each independently represent CR1 or N;
• R1 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;
• Ar1 and Ar2 each independently represent a substituted or unsubstituted (C6-C30)aryl;
• L1 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.