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.