Synthesis and characterization of a wide‐bandgap polymer based on perfluorinated and alkylthiolated benzodithiophene with a deep highest occupied molecular orbital level for organic photovoltaics

A perfluorinated and alkylthiolated benzodithiophene (BDT)‐ttTPD‐based donor polymer (P2FS‐ttTPD) was synthesized via a Stille polymerization, and found to have a number average molecular weight ( M n ) of 13,000 g/mol ( Đ = 2.3). P2FS‐ttTPD has a wide bandgap (1.96 eV) and a deep highest occupied molecular orbital (HOMO) level (−5.70 eV). The perfluorination and alkylthiolation of the polymer backbone lower the polymer's HOMO level significantly. The hole and electron mobilities of P2FS‐ttTPD were determined to be 1.12 × 10 −4 and 9.38 × 10 −7 cm 2 /V s, respectively. Polymer solar cell devices prepared with a P2FS‐ttTPD:IT‐4F (1:1) blend as the active layer were found to exhibit power conversion efficiencies of 4.15%, a short‐circuit current density ( J SC ) of 10.29 mA/cm 2 , an open‐circuit voltage ( V OC ) of 0.97 V, and a fill factor of 41.6%. The (1:1) blend devices were found to exhibit high V OC and low E loss values.