A new solution-processable biarmed organic molecule with triphenylamine (TPA) core and benzothiadiazole-hexylthiophene (BT-HT) arms, B(TPA-BT-HT), has been synthesized by a Heck reaction, and characterized by UV−vis absorption, cyclic voltammetry, and theoretical calculation. Photovoltaic properties of B(TPA-BT-HT) as light-harvesting and electron-donating material in organic solar cells (OSCs), with [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as acceptors, were systematically investigated. The performance of the OSCs varied significantly with B(TPA-BT-HT)/fullerene weight ratio, active layer thickness, and solvents used for spin-coating the active layer. The optimized device with the B(TPA-BT-HT)/PC70BM weight ratio of 1:2 and a thickness of 55 nm with the active layer spin-coated from DCB solution shows a power conversion efficiency of 1.96% with a short-circuit current density of 5.50 mA/cm2 and an open-circuit voltage of 0.96 V under the illumination of AM1.5, 100 mW/cm2.