High-efficiency polymer photovoltaic devices from regioregular-poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C61-butyric acid methyl ester processed with oleic acid surfactant

Bulk heterojunction photovoltaic cells, comprised of regioregular-poly(3-hexylthiophene-2,5-diyl) (P3HT) and[6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) in the presence of the surfactant, oleic acid (OA), have been studied. The device with OA after thermal annealing has a power conversion efficiency (eta(e)) of 4.3%, while the devices without OA after thermal annealing have eta(e)=3.1%. Based on atomic force microscopy, x-ray diffraction investigation found that with OA, the P3HT-PCBM films have better molecular local ordering after thermal annealing resulting in larger donor and acceptor interfaces and higher mobility, thereby higher performance of the photovoltaic cell. (c) 2007 American Institute of Physics.