An organic light-emitting device including a transparent conducting oxide layer as a cathode and a method of manufacturing the organic light-emitting device. The organic light-emitting device includes an anode disposed on a substrate. An organic functional layer including at least an organic light-emitting layer is disposed on the anode. The transparent conducting oxide layer used as the cathode is disposed on the organic functional layer. The transparent conducting oxide layer cathode is formed by plasma-assisted thermal evaporation. A microcavity structure is not formed in the organic light-emitting device, thereby avoiding a luminance change and a color shift as a function of viewing angle.