Fluorinated Benzoselenadiazole-based Low-Band-Gap Polymers for High Efficiency Inverted Single and Tandem Organic Photovoltaic Cells

초록

We designed and synthesized two low-band–gap conjugated copolymers with alternating difluorinated benzoselenadiazole (DFDTBSe) and ethylhexyloxy (EH)- or octyldodecyloxy (OD)-substituted benzo[1,2-b:4,5-b’]dithiophene (BDT) building blocks. The different alkyloxy side chains in the polymers affect the molecular packing and ordering in active-layer films blended with [6,6]-phenyl-C71 butyric acid methyl ester (PC71BM). Bulk heterojunction solar cells were fabricated with an inverted structure of ITO/ethoxylated polyethylenimine/polymer:PC71BM/MoO3/Ag. The device fabricated using the PEHBDT-DFDTBSe:PC71BM active layer shows a maximum power conversion efficiency (PCE) of up to 5.74%, which is the highest value reported for OPVs containing benzoselenadiazole and BDT-derivative polymers.