Organic light-emitting diode display device

An display device including a substrate, an organic light-emitting diode, and a thin film encapsulation layer. The organic light-emitting diode is disposed on the substrate. The thin film encapsulation layer is disposed on the organic light-emitting diode. The thin film encapsulation layer includes at least one inorganic layer, at least one organic layer, and a first refractive-index control layer. The at least one organic layer is alternately disposed with the at least one inorganic layer. The first refractive-index layer is disposed between one of the at least one inorganic layer and one of the at least one organic layer disposed adjacent to each other. The first refractive-index control layer has a refractive-index variation ratio per unit length (Δn/nm) from about 0.001/nm to about 0.002/nm along a direction from the organic light-emitting diode toward the thin film encapsulation layer.