The efficiency of the photovoltaic (PV) device based on P3HT and PCBM bulk heterojunction is improved by introducing small-diameter electrospun ZnO diffused nanofibers network. Diameter, diffusion and melting of nanofibers are controlled by calcination temperature. The thickness of the active layer is optimized for efficient PV devices by varying electrospinning (ES) time. Increased nanofiber's mat thickness by an increase in electrospinning time beyond a certain optimum value reduces the device performance due to increased series resistance, increased traps and reduced blend infiltration through the nanofiber pores. ES time suggests optimized active area for energy absorption and exciton dissociation. In this study, we report the improvement in power conversion efficiency (PCE) from 0.9% to 2.23%, for optimum ES time (similar to 300s). (C) 2012 Elsevier B.V. All rights reserved.