Solution-processable star-shaped photovoltaic organic molecules based on triphenylamine and benzothiadiazole with longer pi-bridge

Two solution-processable star-shaped D–π–A organic molecules with triphenylamine (TPA) as donor unit, benzothiadiazole (BT) as acceptor unit and 4-hexyl-thienylenevinylene as pi conjugated bridge, S(TPA-TBTT) and S(TPA-TBTT-TPA), have been designed and synthesized for the application as donor materials in bulk-heterojunction organic solar cells (OSCs). The two molecules possess broader absorption from 350 to 700 nm benefitted from the longer pi-bridge in the molecules but weaker absorbance and poorer solubility in comparison with their corresponding organic molecules with shorter vinylene pi-bridge. The OSC based on S(TPA-TBTT): PC70BM (1:3, w/w) exhibited Jsc of 6.41 mA/cm2, Voc of 0.75 V, FF of 39.0% and power conversion efficiency of 1.90%, under the illumination of AM 1.5, 100 mW/cm2.

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► We synthesized two new solution-processable star-shaped D–π–A organic molecules.
► The two molecules S(TPA-TBTT) and S(TPA-TBTT-TPA) possess broader absorption.
► We studied the photovoltaic properties of the molecules.
► The OSC based on S(TPA-TBTT): PC70BM exhibited power conversion efficiency of 1.90%.