Post-polymerization modification of phosphorus containing conjugated copolymers

A new phosphafluorene (PF) based monomer, featuring a phosphine oxide substituted with a dodecyl chain, was synthesized. PF was copolymerized with benzodithiophene (BDTT) to form the copolymer PPF-BDTT which has a donor (BDTT)-acceptor (PF) structure. For the first time, direct post-polymerization modifications were performed on the phosphorus center of phosphafluorene-containing conjugated polymers. With Lawesson's Reagent, PPF-BDTT was transformed from a phosphine oxide to a phosphine sulfide. Reduction of the phosphine oxide of PPF-BDTT with HSiCl3, followed by reaction with AuCl center dot SMe2, produced PPF-BDTT-Au, which contains AuCI coordinated to the phosphafluorene moiety. PPF-BDTT, PPF-BDTT-S, and PPF-BDTT-Au were characterized optically and electrochemically and the results compared to related BDTT containing copolymers. PPF-BDTT and its derivatives were found to have high LUMO and HOMO levels and larger bandgaps compared to common donor-acceptor copolymers. Organic solar cells were fabricated from PPF-BDTT, PPF-BDTT-S, and PPF-BDTT-Au, although the performances of these devices were poor with power conversion efficiencies ranging from 0.13% to 0.60%.