wThe temperature dependence of device parameters of polymer solar cells based on alternating copolyfluorene incorporating dioctyl-fluorene and di-thienyl-benzothiadiazole (APFO-3) mixed with [6,6]-phenyl-C61-butyric acid methylester (PCBM) was modeled theoretically by simulation and investigated experimentally under illumination of AM1.5 (100mW/cm(2)). Both simulation and experimental results show photocurrent, fill factor and power conversion efficiency all increase, and the open-circuit voltages monotonically decrease with temperature increase from room temperature (RT) to 120 degrees C. These results can be explained by taking into account the temperature dependence of the mobility, and the thermal activation of the injection current from the electrodes. The increase of PCE with temperature is a distinguishing feature of polymer solar cells. (c) 2005 Elsevier B.V. All rights reserved.