Heterocyclic compound and organic light-emitting diode including the same

A heterocyclic compound, comprising a compound represented by Formula 1:

• wherein:
• X1 comprises CR11 or nitrogen (N),
• X2 comprises C(R12)(R13), NR14, S, or O,
• each of X3 and X4 independently comprises CR15 or N,
• each of R1 to R5 and R11 to R15 independently comprises a hydrogen atom, a heavy hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a carboxyl group, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C3-C30 cycloalkenyl group, a substituted or unsubstituted C5-C30 aryl group, or a substituted or unsubstituted C2-C30 heteroaryl group,
• Ar1 comprises a hydrogen atom, a heavy hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a carboxyl group, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C3-C30 cycloalkenyl group, a substituted or unsubstituted C5-C30 aryl group, a substituted or unsubstituted C5-C30 aryloxy group, a substituted or unsubstituted C5-C30 arylthio group, a substituted or unsubstituted C2-C30 heteroaryl group, —N(Q1)(Q2), or —Si(Q3)(Q4)(Q5)(Q6), wherein:
• each of Q1 to Q6 independently comprises a hydrogen atom, a heavy hydrogen atom, a halogen atom, a hydroxyl group, a cyano group, an amino group, a nitro group, a carboxyl group, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C3-C30 cycloalkyl group, a substituted or unsubstituted C3-C30 cycloalkenyl group, a substituted or unsubstituted C5-C30 aryl group, a substituted or unsubstituted C5-C30 aryloxy group, a substituted or unsubstituted C5-C30 arylthio group, or a substituted or unsubstituted C2-C30 heteroaryl group,
• L1 comprises a substituted or unsubstituted C5-C30 arylene group or a substituted or unsubstituted C2-C30 heteroarylene group, and
• a is an integer from 0 to 3.