Improving photovoltaic properties of the linear A-Ar-A type small molecules with rhodanine by extending arylene core

In order to efficiently tune photovoltaic performance, a series of linear A-Ar-A type small molecules (SMs) of (DRCN3T)2Ar were designed and synthesized, which contain the same terminal of 2-(1,1-dicyanomethylene) rhodanine (DRCN) and π-bridged space of 5-vinyl-trithiophene (3T), but different central arylene (Ar) unit, respectively. Significantly extending film absorption and increasing hole mobility were obtained in these SMs with enlarging Ar units from phenylene (Ph), naphthylene (Nap) to anthrylene (Ant). As a result, photovoltaic properties were remarkably improved in these SM/PC71BM based solution-processing organic solar cells (OSCs) by enlarging Ar units in (DRCN3T)2Ar. The highest power conversion efficiency of 5.15% with a short-circuit current density of 11.34 mA cm−2 was obtained in the (DRCN3T)2Ant based device, which is three times of that in the (DRCN3T)2Ph-based device. Our work further indicates that properly extending Ar core could be beneficial to improve photovoltaic properties for the A-Ar-A type SMs.