An organic light-emitting diode (OLED) device with high efficiency and brightness is fabricated by inserting CuOx/Cu dual inorganic buffer layers between indium-tin-oxide (ITO) and hole-transport layer (HTL). The CuO_x/Cu buffer layer limits the operating current density obviously, while the brightness and efficiency are both enhanced greatly. The highest brightness of the optimized device is achieved to be 14 000 cd/m²at current efficiency of 3 cd/A and bias voltage of 15 V, which is about 50% higher than that of the compared device without CuO_x/Cu buffer layer. The highest efficiency is achieved to be 5.9 cd/A at 11.6 V with 3 400 cd/m², which is almost twice as high as that of the compared device.