Investigations of a New High-Performance Low-Band-Gap Photovoltaic Polymer Semiconductor

Abstract

Application of our newly synthesized low-band-gap polymer, i.e., PDTBT-TT, in organic solar cells (OSCs) has been studied. We have investigated the effects of molecular weight of the PDTBT-TT on the PDTBT-TT:PC₇₁ BM-based bulk heterojunction OSCs' performance. It was found that the OSCs fabricated with higher molecular weight (M_n) PDTBT-TT polymer have the higher short-circuit current and power conversion efficiency. The better performance of the PDTBT-TT-based OSC with the higher M_n PDTBT-TT polymer is attributed to the improved charge transfer resistance and the suppressed bimolecular recombination inside the PDTBT-TT:PC₇₁ BM blend active layer of the OSC. Moreover, the increased doping density observed in the higher M_n PDTBT-TT:PC₇₁ BM-based OSCs increases the photocurrent and leads to the cell's higher power conversion efficiency.