An organic light-emitting device including a substrate; a first electrode on the substrate, the first electrode including a first surface and a second surface opposite to the first surface; an organic layer on the first electrode, the organic layer being adjacent to the first surface of the first electrode; a second electrode on the organic layer, the second electrode including a first surface adjacent to the organic layer and a second surface opposite to the first surface; and a luminescent efficiency improvement layer on at least one of the second surface of the first electrode and the second surface of the second electrode, the luminescent efficiency improvement layer including a condensed-cyclic compound represented by Formula 1, below: