An organic light-emitting diode includes a first electrode and a second electrode facing the first electrode; an emission layer between the first electrode and the second electrode; a hole transport layer between the first electrode and the emission layer and includes a first hole transport layer, a second hole transport layer, and a buffer layer between the first hole transport layer and the second hole transport layer; and an electron transport layer between the emission layer and the second electrode, wherein the buffer layer and the electron transport layer each include a mixture of an electron-transporting organometallic compound and an electron-transporting organic compound.