Design and synthesis of star-burst triphenyamine-based π-conjugated molecules

Abstract A series of star-shaped π-conjugated molecules with triphenylamine as the core and a thiophene unit as the π-bridge were designed and synthesized based on a donor-π-bridge-acceptor type of molecular framework. Various peripheral electron-deficient groups including octyl-2-cyanoacrylate, octyl-2,3-dicyanoacrylate and 1,3-diethyl-2-thiobarbituric were incorporated as electron-withdrawing moieties. By altering the terminal groups, star-shaped molecules with symmetric and asymmetric architectures were obtained. It was worth noting that the asymmetric molecules exhibited well-extended absorbance with the combination of absorption features of different donor-acceptor species. Electrochemical investigation indicated that the frontier molecular orbital energy levels can be modified by the terminal electron-withdrawing groups. Despite the fabricated organic photovoltaic devices based on the new molecules as electron-donating materials exhibited less pronounced performances, we surmise the current work illustrated an effective molecular design strategy for the realization of broad absorbance that was beneficial for the utilization of solar photon flux.