Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Publication date: 7th November 2016
In optical photovoltaics, properties of donor-acceptor interface play an important role in its functionality. Regarding this point, cychlopentadithiophene-benzothiadiazole copolymer (PCPDTBT) has interesting experimental characteristics: when it has 2-ethylhexyl (EH) side chain, “face-on” configuration is dominant, while “edge-on” configurations are prevailing for n-dodecyl (C12) and n-hexadecanyl (C16) side chains. Saeki and co-workers in Osaka Univ. measured charge separation and recombination efficiencies on PCBM/PCPDTBT(EH, C12, C16) interfaces using time-resolved microwave conductivity method, and found that charge separation and recombination are faster in PCPDTBT-EH, compared to those in C12 and C16 cases. In order to understand this experimental result, we performed molecular dynamics simulation on PCBM/PCPDTBT interface as well as quantum chemistry calculation to obtain charge separation and recombination rates between PCBM and PCPDTBT monomers in various relative configurations. Our calculations suggest that donor-acceptor distances at “face-on” configuration are generally smaller than those at “edge-on” configuration, and this difference results in difference of charge separation and recombination rates.