Charge transport and recombination in bulk heterojunction solar cells studied by the photoinduced charge extraction in linearly increasing voltage technique

Abstract

Charge carrier mobility and recombination in a bulk heterojunction solar cell based on the mixture of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C-61 (PCBM) has been studied using the novel technique of photoinduced charge carrier extraction in a linearly increasing voltage (Photo-CELIV). In this technique, charge carriers are photogenerated by a short laser flash, and extracted under a reverse bias voltage ramp after an adjustable delay time (t(del)). The Photo-CELIV mobility at room temperature is found to be mu=2x10(-4) cm(2) V-1 s(-1), which is almost independent on charge carrier density, but slightly dependent on t(del). Furthermore, determination of charge carrier lifetime and demonstration of an electric field dependent mobility is presented. (C) 2005 American Institute of Physics.