An organic light-emitting device includes an anode, a cathode, and an organic layer between the anode and the cathode, wherein the organic layer includes a mixed organic layer, and the mixed organic layer includes at least two different compounds, and a triplet energy of at least one compound of the at least two different compounds is 2.2 eV or higher. The organic light-emitting device according to embodiments of the present invention may have a low driving voltage, a high efficiency, and a long lifespan.