A heterocyclic compound represented by the following formula 1: wherein n is 2, X 1 to X 3 are the same or different, and are each independently N or CH, and at least one of X 1 to X 3 is N, Ar 1 and Ar 2 are the same or different, and are each independently a substituted or unsubstituted aryl group or a heterocyclic group, L is an unsubstituted phenylene group, and Ar 3 is any one selected from among the following structures: wherein a, c, d and e are each an integer ranging from 1 to 6, and R1, R4, R5 and R6 are the same or different, and are each independently hydrogen, deuterium, a halogen group, a nitrile group, a nitro group, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthioxy group, a substituted or unsubstituted arylthioxy group, a substituted or unsubstituted alkylsulfoxy group, a substituted or unsubstituted arylsulfoxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted silyl group, a substituted or unsubstituted boron group, a substituted or unsubstituted amine group, a substituted or unsubstituted alkylamine group, a substituted or unsubstituted aralkylamine group, a substituted or unsubstituted arylamine group, a substituted or unsubstituted heteroarylamine group, a substituted or unsubstituted aryl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazole group, or a substituted or unsubstituted heterocyclic group containing at least one heteroatom selected from among N, O, S and P. n is 2, X 1 to X 3 are the same or different, and are each independently N or CH, and at least one of X 1 to X 3 is N, Ar 1 and Ar 2 are the same or different, and are each independently a substituted or unsubstituted aryl group or a heterocyclic group, L is an unsubstituted phenylene group, and Ar 3 is any one selected from among the following structures: wherein a, c, d and e are each an integer ranging from 1 to 6, and R1, R4, R5 and R6 are the same or different, and are each independently hydrogen, deuterium, a halogen group, a nitrile group, a nitro group, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthioxy group, a substituted or unsubstituted arylthioxy group, a substituted or unsubstituted alkylsulfoxy group, a substituted or unsubstituted arylsulfoxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted silyl group, a substituted or unsubstituted boron group, a substituted or unsubstituted amine group, a substituted or unsubstituted alkylamine group, a substituted or unsubstituted aralkylamine group, a substituted or unsubstituted arylamine group, a substituted or unsubstituted heteroarylamine group, a substituted or unsubstituted aryl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazole group, or a substituted or unsubstituted heterocyclic group containing at least one heteroatom selected from among N, O, S and P.