An organic light-emitting device including a substrate; a first electrode; a second electrode; an emission layer; a first electron transport layer; a second electron transport layer; a third electron transport layer; and a hole transport layer, wherein the first electron transporting material has an electron mobility smaller than an electron mobility of the second electron transporting material at an electric field of 800 to 1000 V/cm, the second electron transporting material and the third electron transporting material each independently have an electron mobility of about 10−8 to about 10 cm2/V·s at an electric field of 800 to 1000 V/cm, and the third electron transport layer has an electron injection barrier of about 0.2 eV or less at an interface between the third electron transport layer and the second electrode.