A heterocyclic compound represented by Formula 1 below: wherein X is *-Ar 1 or wherein Ar 1 is a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, or a substituted or unsubstituted C 2 -C 60 heteroaryl group,; Ar 2 is a substituted or unsubstituted C 5 -C 60 arylene group, a substituted or unsubstituted C 5 -C 60 aryleneoxy group, a substituted or unsubstituted C 5 -C 60 arylenethio group, or a substituted or unsubstituted C 2 -C 60 heteroarylene group,; * indicates a binding site; Y 1, Y 2, Y 3 and Y 4 are each independently NR 7, O, or S; a, b, c and d are each independently an integer of 0 or 1, wherein a+b=1 and c+d=1; and R 1, R 2, R 3, R 4, R 5, R 6 and R 7 are each independently a hydrogen atom, a deuterium, a tritium, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a silyl group, a substituted or unsubstituted C 1 -C 50 alkyl group, a substituted or unsubstituted C 2 -C 50 alkenyl group, a substituted or unsubstituted C 2 -C 50 alkynyl group, a substituted or unsubstituted C 1 -C 50 alkoxy group, a substituted or unsubstituted C 3 -C 50 cycloalkyl group, a substituted or unsubstituted C 3 -C 50 cycloalkenyl group, a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, a substituted or unsubstituted C 2 -C 60 heteroaryl group, or N(Q 1)(Q 2), and Q 1 and Q 2 are each independently a hydrogen atom, a deuterium, a tritium, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a silyl group, a substituted or unsubstituted C 1 -C 50 alkyl group, a substituted or unsubstituted C 2 -C 50 alkenyl group, a substituted or unsubstituted C 2 -C 50 alkynyl group, a substituted or unsubstituted C 1 -C 50 alkoxy group, a substituted or unsubstituted C 3 -C 50 cycloalkyl group, a substituted or unsubstituted C 3 -C 50 cycloalkenyl group, a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, and a substituted or unsubstituted C 2 -C 60 heteroaryl group, wherein optionally at least two of R 1, R 2, R 3, R 4, R 5, R 6, and R 7 which are adjacent to each other bind to each other to form a saturated or unsaturated ring. wherein Ar 1 is a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, or a substituted or unsubstituted C 2 -C 60 heteroaryl group,; Ar 2 is a substituted or unsubstituted C 5 -C 60 arylene group, a substituted or unsubstituted C 5 -C 60 aryleneoxy group, a substituted or unsubstituted C 5 -C 60 arylenethio group, or a substituted or unsubstituted C 2 -C 60 heteroarylene group,; * indicates a binding site; Y 1, Y 2, Y 3 and Y 4 are each independently NR 7, O, or S; a, b, c and d are each independently an integer of 0 or 1, wherein a+b=1 and c+d=1; and R 1, R 2, R 3, R 4, R 5, R 6 and R 7 are each independently a hydrogen atom, a deuterium, a tritium, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a silyl group, a substituted or unsubstituted C 1 -C 50 alkyl group, a substituted or unsubstituted C 2 -C 50 alkenyl group, a substituted or unsubstituted C 2 -C 50 alkynyl group, a substituted or unsubstituted C 1 -C 50 alkoxy group, a substituted or unsubstituted C 3 -C 50 cycloalkyl group, a substituted or unsubstituted C 3 -C 50 cycloalkenyl group, a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, a substituted or unsubstituted C 2 -C 60 heteroaryl group, or N(Q 1)(Q 2), and Q 1 and Q 2 are each independently a hydrogen atom, a deuterium, a tritium, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a silyl group, a substituted or unsubstituted C 1 -C 50 alkyl group, a substituted or unsubstituted C 2 -C 50 alkenyl group, a substituted or unsubstituted C 2 -C 50 alkynyl group, a substituted or unsubstituted C 1 -C 50 alkoxy group, a substituted or unsubstituted C 3 -C 50 cycloalkyl group, a substituted or unsubstituted C 3 -C 50 cycloalkenyl group, a substituted or unsubstituted C 5 -C 60 aryl group, a substituted or unsubstituted C 5 -C 60 aryloxy group, a substituted or unsubstituted C 5 -C 60 arylthio group, and a substituted or unsubstituted C 2 -C 60 heteroaryl group, wherein optionally at least two of R 1, R 2, R 3, R 4, R 5, R 6, and R 7 which are adjacent to each other bind to each other to form a saturated or unsaturated ring.