Improving power conversion efficiency in polythiophene/fullerene-based bulk heterojunction solar cells

In the present work, we have studied photovoltaic devices fabricated from a blend of regioregular poly (3-hexlthiophene) (P3HT) and Buckminster fullerene. The solvent and composite ratio have been selected to obtain best morphology and minimum degradation. Buffer layers of poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS) at the anode and of LiF at the cathode were used to improve the device performance. It was further found that post-annealing of the devices for an optimum duration and temperature improves the solar cells, and the power conversion efficiency of the devices increases to 2.1% at AM1.5. Though the efficiency using [6,6]-phenyl C60 butyric acid methyl ester (PCBM) as the composite acceptor instead of C60 can be higher, it was not used because of its very high cost as compared to C60.