In this study, we optimize the process of treating the surface of Ag anodes through exposure to UV-ozone, for the efficient planar heterojuction top-illuminated organic solar cells (OSCs). Several characteristics of Ag anodes such as work function (Phi(Anode)), surface roughness (R-a) and sheet resistance are increased proportionally to exposure time following the formation of AgOx on the surface. Two factors, Phi(Anode) and R-a, dominated the performance of the device due to their opposite contributions of power conversion efficiency (PCE). An increase in Phi(Anode) flattened the energy barrier level between the anode and copper phthalocyanine, thereby benefiting hole injection and increasing open circuit voltage (V-OC). An increase in R-a led to an increase in the density of localized traps, which obstructed hole injection and degraded the V-OC. It also reduced reflectivity, thereby diminishing the short circuit current density (J(SC)). The top-illuminated OSCs in this study were optimized following surface treatment of the anode for 45 s to achieve a maximum PCE of 1.04%, V-OC of 0.48 V. and J(SC) of 3.56 mA/cm(2) with a fill factor of 60.7%. (C) 2011 Elsevier B.V. All rights reserved.