In this work, a soluble perylene-derivative dye, N, N'-didodecyl-3,4,9,10-perylene tetracarboxylic diimide (PDI), was used to improve the photovoltaic performance of poly(3-hexylthiophene) (P3HT)/ZnO bulk heterojunction cells through blending with the composite. Results show that by incorporation of PDI in the P3HT/ZnO composite, the light absorption and exciton separation can be significantly improved. The photocurrent under white-light irradiation can be increased from 6.35 to 9.55 mA/cm(2). Solar decay experiment shows that V-OC of the ITO/PEDOT:PSS/P3HT:ZnO:PDI/Al device decreases rapidly to almost zero in I h under persistent white-light illumination. After placing a 420 nm cutoff filter between the cell and the xenon lamp, the stability of the cell can be significantly improved. The device performance can maintain about 80% of the original value within 30 h and I-SC degraded to zero after 142 h. The addition of PDI into the P3HT/ZnO device up to 5 wt% does not show observable effect on the solar cell decay behavior. (c) 2008 Elsevier B.V. All rights reserved.