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 (C-70) have been developed. 6T is well known as a good hole transport material, and C-70 is expected to have a good electron transport and a higher photo-absorption property than C-60 in the visible range. We have already reported that 6T:C-60 BHJ OPV cells showed excellent photovoltaic properties by C-60 excess blend co-evaporation method [1]. We report that the J(sc) of 6T:C-70 BHJ OPV cells increases by employing C-70 instead of C-60 and the all PV characteristics of 6T:C-70 cells are dramatically improved by the thermal annealing process. (C) 2009 Elsevier B.V. All rights reserved.