A thin-film transistor (TFT) array substrate and organic light-emitting diode (OLED) display are disclosed. In one aspect, the TFT array substrate includes a driving TFT including a driving gate electrode, a switching TFT including a switching gate electrode and spaced apart from the driving TFT, and a storage capacitor including a first electrode electrically connected to the driving gate electrode and a second electrode formed over and insulated from the first electrode. The TFT array substrate also includes a capacitor insulating film formed between the first and second electrodes and an interlayer insulating film covering at least part of the driving TFT, at least part of the switching TFTs, and the capacitor insulating film, wherein the switching gate electrode and the second electrode are formed of the same material.