High Bandgap (1.9 eV) Polymer with Over 8% Efficiency in Bulk Heterojunction Solar Cells

Two high bandgap donor-acceptor polymers based on benzodithiophene with different alkyl side chains and fluorinated benzotriazole are designed and synthesised. Due to the deep HOMO energy level and high hole mobility of the octylthio substituted polymer PBDTTS-FTAZ, it exhibits higher efficiency of 8.3% in bulk-heterojunction solar cells. This indicates the advantages of alkylthio over alkyl for the design of conjugated polymers.