A wide-bandgap polymer based on alkylthio-naphthyl- substituted benzo[1,2-b:4,5-b′]dithiophene units for efficient fullerene-based and fullerene-free polymer solar cells

A wide-bandgap polymer PBDTNS-TPD based on alkylthio-naphthyl-substituted benzo[1,2-b:4,5-b′]dithiophene units was synthesized. The PBDTNS-TPD exhibited better light-harvesting properties and charge transport properties than that of alkylthio-phenyl-substituted counterpart PBDTBS-TPD. The PBDTNS-TPD:PC71BM solar cell devices yield a PCE of 9.09%, which exhibits an increase of 29% in comparison with that of PBDTBS-TPD-based PSCs (PCE 7.02%). Moreover, the PBDTNS-TPD:ITIC based PSCs also shows a higher PCE of 8.19% as compared to the PBDTBS-TPD:ITIC based PSCs (PCE 5.93%).154