Infrared photocurrent spectral response from plastic solar cell with low-band-gap polyfluorene and fullerene derivative

Plastic solar cells were fabricated using a low-band-gap alternating copolymer of fluorene and a donor-acceptor-donor moiety (APFO-Green1), blended with [6,6]-phenyl-C-61-butyric acid methylester or 3(')-(3,5-Bis-trifluoromethylphenyl)-1(')-(4-nitrophenyl)pyrazolino[60]fullerene as electron acceptors. The polymer shows optical absorption in two wavelength ranges from 300<lambda<500 nm and 650<lambda<1000 nm. Devices based on APFO-Green1 blended with the later fullerene exhibit an outstanding photovoltaic behavior at the infrared range, where the external quantum efficiency is as high as 8.4% at 840 nm and 7% at 900 nm, while the onset of photogeneration is found at 1 mum. A photocurrent density of 1.76 mA/cm(2), open-circuit voltage of 0.54 V, and power conversion efficiency of 0.3% are achieved under the illumination of AM1.5 (1000 W/m(2)) from a solar simulator. (C) 2004 American Institute of Physics.