Nanoscale Phase Separation-Induced Suppression of Geminate Recombination in Low Bandgap Polymer-Fullerene Solar Cells

The short-circuit current of polymer solar cells based on a PCPDTBT:PC₇₁BM blend is substantially increased by using a processing additive. It is found that the significant geminate recombination in the PCPDTBT:PC₇₁BM blend film is dramatically suppressed by using a processing additive which can produce a nanoscale PCPDTBT and PC₇₁BM phase separation. The processing additive-induced aggregation of PCPDTBT polymer chains and PC₇₁BM molecules can give rise to a driving force for the separation of charge-transfer states at the donor/acceptor interfaces into the free charge carriers and thus geminate recombination is suppressed.