Thin film and organic light-emitting device including the same

A thin film comprising:

• i) a combination of a donor compound and an acceptor compound, and
• ii) a blue phosphorescent dopant,
• wherein the donor compound and the acceptor compound form an exciplex,
• wherein the acceptor compound comprises at least one electron-withdrawing group selected from:
• —F, —CFH2, —CF2H, —CF3, —CN, and —NO2;
• a C1-C60 alkyl group substituted with at least one selected from —F, —CFH2, —CF2H, —CF3, —CN, and —NO2;
• a C1-C60 heteroaryl group and a divalent non-aromatic condensed polycyclic heterocyclic group, each comprising *═N—*′ as a ring-forming moiety, and
• a C1-C60 heteroaryl group and a divalent non-aromatic condensed polycyclic heterocyclic group, each comprising *═N—*′ as a ring-forming a moiety and each substituted with at least one selected from deuterium, —F, —CFH2, —CF2H, —CF3, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phoshoric acid group or a salt thereof, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C7-C60 arylalkyl group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted C1-C60 heteroaryloxy group, a substituted or unsubstituted C1-C60 heteroarylthio group, a substituted or unsubstituted C2-C60 heteroarylalkyl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group,
• wherein a maximum emission wavelength Δmax (Ex) in a photoluminescence spectrum of the exciplex is about 390 nanometers or greater and about 490 nanometers or less,
• wherein a decay time Tdecay(Ex) of delayed fluorescence in a time-resolved photoluminescence spectrum of the exciplex is about 100 nanoseconds or greater,
• wherein a ratio of a delayed fluorescence portion to the overall light-emitting portions in the time-resolved photoluminescence spectrum of the exciplex is about 10% or greater, and
• wherein the photoluminescence spectrum and the time-resolved photoluminescence spectrum of the exciplex are each a spectrum measured at room temperature with respect to a film that is formed by co-deposition of the donor compound and the acceptor compound on a substrate.