Photovoltaic and charge recombination characteristics of regioregular poly(3-hexylthiophene)/poly(9,9´-dioctyl fluorene-co-benzothiadiazole) based solar cells

Blends of poly(3-hexylthiophene) (P3HT) and poly(9,9´-dioctylfluorene-co-benzothiadiazole) (BT) electron donor and acceptor polymers were studied as organic solar cell materials. P3HT and BT exhibit relatively high hole and electron mobilities compared with other known conjugated polymers, an attractive feature for photocarrier collection. The two polymers were well mixed in solution and the resulting thin films were optically clear, indicating good compatibility on a sub-micron length. Almost perfect exciton transfer was observed from BT to P3HT. The external quantum and power conversion efficiencies of solar cells with blend films of 60 wt.% P3HT reached 2% and 0.07%, respectively. At low incident light intensity, all of the blend films as well as the pristine polymers showed monomolecular charge recombination.