Device model for the operation of polymer/fullerene bulk heterojunction solar cells

We have developed a numerical device model that consistently describes the current-voltage characteristics of polymer: fullerene bulk heterojunction solar cells. Bimolecular recombination and a temperature- and field-dependent generation mechanism of free charges are incorporated. It is demonstrated that in poly2-methoxy-5- (3^', 7^'-dimethyloctyloxy) -p-phenylene vinylene- (OC₁C₁₀-PPV-) and 6, 6-phenyl C₆₁-butyric acid methyl ester- (PCBM-) (1: 40. 3em{0ex}wt. 0. 2em{0ex}%) based solar cells space-charge effects only play a minor role, leading to a relatively constant electric field in the device. Furthermore, at short-circuit conditions only 7% of all free carriers are lost due to bimolecular recombination. The model predicts that an increased hole mobility together with a reduction of the acceptor strength of 0. 50. 3em{0ex}eV will lead to a maximum attainable efficiency of 5. 5% in the PPV/PCBM-based solar cells.