We focused on the light out coupling efficiency to be improved. To improve out coupling efficiency, we considered air/substrate interface is the key place to be modified. We simulated various shaped array at that interface for high out coupling efficiency. As a result of simulation, we found that the pyramid array was best. We successfully fabricated a pyramid array film and attached to a white emission OLED panel for evaluation. The white emission OLED was optimized to be suitable for the pyramid array. The luminance and flux of OLED with pyramid array were increased by a factor of 2.0, 1.7 relatively. For further improvement in luminance, we found that additional use of Brightness Enhancement Film (BEF) with optimized OLED device is able to achieve much higher luminous efficiency of 3.0 times comparing to the normal OLED.