Both the performance and stability are the two major tasks for scientists to tackle in polymer solar cells. We introduce 3-hydroxyflavone (3-HF), a free-radical scavenging agent, as an additive in poly (3-hexythiophene):(6,6)-phenyl C-61 butyric acid methyl ester (P3HT:PCBM) blend forming new photoactive material, which is used as an active layer in inverted solar cell devices. It was found that the addition of an adequate amount of 3-HF enhances the photocurrent, which is due to the improved carrier mobility. A power conversion efficiency (PCE) of the device has improved from 2.57% to 3.05%. In addition, 3-HF can further stabilize the inverted solar cell performance with a 85% retaining of its original PCE over a month in ambient condition as compared to the additive-free device of a value of 57%. Thus, incorporating 3-HF as an additive is an effective and simple method to approach the goal of high PCE while maintaining stable ambient operation. (C) 2011 Elsevier B.V. All rights reserved.