Improved Charge-Collection Efficiency in PCDTBT:PC71BM-Based Solar Cells via CS2 Solvent Vapor Annealing

Photo-generated charge collection is strongly correlated with the alignment and connectivity of the individual domains of donor and acceptor in bulk heterojunction polymer solar cells. It is found that CS2 vapor annealing on PCDTBT:PC71BM (1:4) blend effectively improves the hole-transport pathways of PCDTBT domains, which reduces accumulation of photo-generated charges and improves charge collection efficiency. The PCDTBT:PC71BM-based solar cells with the active layer subjected to CS2 vapor annealing demonstrate a high fill factor of 0.71-0.73 and a power conversion efficiency of 6.68%, about a 10% increase in comparison with the control cell