An organic light-emitting device including a first electrode, a second electrode, and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer includes an emission layer, the emission layer includes a host, a dopant, and a sensitizer, the host does not include a metal atom, the dopant emits light, and the light has a decay time of about 100 nanoseconds or less, and the sensitizer includes an organometallic compound represented by one selected from Formulae 1 and 2 described in the specification.