Improved Photovoltaic Performance Of Star-Shaped Molecules With A Triphenylamine Core By Tuning The Substituted Position Of The Carbazolyl Unit At The Terminal

Two star-shaped molecules of TPA(BT-2Cz)(3) and TPA(BT-3Cz)(3) with a triphenyl-amine (TPA) core were designed and synthesized, in which 2- and 3-carbazolyl units (2Cz and 3Cz) are attached to the benzothiadiazole (BT) arms as planar terminal groups, respectively. Although both molecules show a similar broad UV-Vis absorption covering from 300 nm to 560 nm, different photovoltaic performances were observed owing to the varied linked positions of terminal carbazolyl units. In contrast to TPA(BT-2Cz) 3-based solar cells, solution-processable organic solar cells (OSCs) based on TPA(BT-3Cz)(3) exhibited better photovoltaic performance with the maximum power conversion efficiency up to 3.94% and an enhanced short-circuit current of 8.80 mA cm(-2). This work further demonstrates that tuning the substituted position of the terminal carbazolyl group can significantly improve the photovoltaic performance of its resulting small molecules.