This article provides an efficient way for improving the light absorption properties and photovoltaic performance of a bulk heterojunction (BHJ) organic solar cells (OSCs) by using a light-trapping (LT) Al-doped ZnO(AZO) via controlling the heating process. Through the comparison of device performance parameters based on three different surface structures of AZO, results show that the 5 degrees C/min AZO layer with peak as high as 140 nm and average distance between major peaks of about 1.6 gm exhibited the highest LT ability. The AZO layer serves multiple functions to affect the photo-induced charge transfer, increase the light absorption through light scattering as well as a template to influence the BHJ distribution leading to a superior interface properties. Devices based on the AZO displayed a significant improvement in PCE by 43% (for the P3HT devices) and 25% (for the PTB7 devices), compared to the planar ZnO-based device. Our findings are also applicable to other BHJ mixtures for OSCs and other types of thin film solar cells. (C) 2017 Elsevier Ltd. All rights reserved.