Annealing effect in the sexithiophene:C70 small molecule bulk heterojunction organic photovoltaic cells

Novel small molecule bulk heterojunction (BHJ) organic photovoltaic (OPV) cells consisting of an alpha-sexithiophen (6T) and a high fullerene (C70) have been developed. 6T is well known as a good hole transport material, and C70 is expected to have a good electron transport and a higher photo-absorption property than C60 in the visible range. We have already reported that 6T:C60 BHJ OPV cells showed excellent photovoltaic properties by C60 excess blend co-evaporation method [1]. ort that the Jsc of 6T:C70 BHJ OPV cells increases by employing C70 instead of C60 and the all PV characteristics of 6T:C70 cells are dramatically improved by the thermal annealing process.