An OLED device including a first electrode; a second electrode; and an organic layer, the organic layer including an emission layer, a hole transport region between the first electrode and the emission layer, the hole transport region including at least one of a hole transport layer, a hole injection layer, and a buffer layer, and an electron transport region between the emission layer and the second electrode, the electron transport region including at least one of a hole blocking layer, an electron transport layer, and an electron injection layer, wherein the emission layer includes at least one host (H) and at least one phosphorescent dopant (D), an electron affinity (EA) and an ionization potential (IP) simultaneously satisfying the relationships represented by Equation (1) and Equation (2) below: EA(D)−EA(H)≧0.2 eV  (1) IP(H)−IP(D)≧0.2 eV  (2).