Alkylated indacenodithieno[3,2-b]thiophene based non-fullerene acceptor with high crystallinity, low voltage loss and single junction solar cell efficiency greater than 13% with Low Voltage Losses

We report a new synthetic route to prepare an alkylated indacenodithieno[3,2-b]thiophene (IDTT) based non-fullerene acceptor (C8-ITIC). Compared to the reported ITIC with phenylalkyl side chains, the new acceptor C8-ITIC exhibited a red-shifted absorption with increased absorptivity. Accordingly, blends with the donor polymer PBDB-T exhibited an efficiency up 12.4%. Further improvements in efficiency were found upon backbone fluorination of the donor polymer. The resulting blend showed an impressive PCE up to 13.2%, which is related to broad absorption, higher crystallinity of C8-ITIC and low voltage loss in blend.