Theoretical study of two-photon absorption properties of organic Π-conjugated materials for photovoltaic devices

Frequency up-conversion describes the conversion of low energy incident photons towards higher energy photons via active material. Two-photon absorption is one of the approaches for this strategy which can improve the efficiency in the solar cell. In this report, the molecular structures were designed from the symmetrical grafting of two elongated conjugated linker on a conjugated core and then adding donor group at both the terminals. Fluorine derivatives as a core acceptor, phenylethynl as the conjugated linker and diphenylamino or methyl-9H-carbozole as the donor end groups were selected for the design. Such conjugated molecules bearing two electron-releasing (donor) end-groups display large two-photon absorption cross section. All the calculations were performed using time dependent density functional theory (TD-DFT) with B3LYP/6-31G.