Impact of the Interfacial Molecular Structure Organization on the Charge Transfer State Formation and Exciton Delocalization in Merocyanine:PC61BM Blends

The intermolecular charge transfer (CT) exciton in the merocyanine:[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) system induced by the molecular geometry is investigated. The CT state, localized on the merocyanine domain, was experimentally observed in the transient spectra and modeled via DFT/TDDFT calculations. A relationship between molecular geometry at the donor/acceptor interface and the delocalization of the CT exciton was identified. It was found that different alkyl side chains of merocyanine can be used to tune the formation of H-aggregates by means of better intermixing with PC61BM. Moreover, we observed that high H aggregation increases the charge delocalization and improves the efficiency and carrier transport properties of the merocyanine-based bulk heterojunction solar cell.