Organic light-emitting diodes (OLEDs) are widely commercialized in the display market due to many advantages such as wide color gamut, outstanding flexibility, and high contrast ratio. However, the performance of OLED is often hindered by the refractive index differences between the anode, substrate, and air, leading to inefficient light out-coupling from the device. In this study, we designed a polymer substrate incorporated with barium titanium oxide (BaTiO3) nanoparticles (NPs) with high refractive index to function as a bifunctional scattering substrate for efficiency enhancement of OLEDs. Fine-tuning the concentration of BaTiO(3)NPs enables direct control of the refractive index and optical scattering of the substrate. The results show that the luminance efficiency and external quantum efficiency of OLED employing BaTiO(3)embedded substrate are approximately 1.6 times higher than its pristine counterpart. Evidently, the nanocomposite polymer substrate demonstrated herein could serve as an efficient light out-coupling medium for flexible OLEDs.