Organic light-emitting device

An organic light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an emission layer disposed between the first electrode and the second electrode,
• wherein the emission layer comprises a host and a thermally activated delayed fluorescence emitter, and
• the host comprises a compound represented by Formula 1, a compound represented by Formula 2, or a combination thereof:
• wherein, in Formulae 1 and 2,
• Z1 to Z6 are each independently:
• hydrogen, deuterium, —F, —Cl, —Br, —I, or a cyano group;
• or
• a C1-C20 alkyl group, a phenyl group, a biphenyl group, a terphenyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a cyano group, a C1-C20 alkyl group, a phenyl group, a biphenyl group, or any combination thereof,
• b1 to b6 are each independently 1, 2, 3, or 4, and
• in Formulae 1 and 2, at least one of, i) Z1 in the number of b1, ii) Z2 in the number of b2, iii) Z3 in the number of b3, iv) Z4 in the number of b4, v) Z5 in the number of b5, and vi) R6 in the number of b6 is a cyano group.