Synthesis and photovoltaic properties of star-shaped triphenylamine molecules with donor–acceptor unit as core

Two new star-shaped triphenylamine (TPA) molecules [Th3(TPABT) and TPA3(TPABT)] with TPA (donor)-benzothiadiazole (acceptor)-4-hexylthiophene unit as core, TPA or 4-hexylthiophene as arms were synthesized by Pd-catalyzed Stille coupling reaction. These TPA molecules have good solubility and film-forming ability in common organic solvents such as chloroform, tetrahydrofuran and toluene and have strong absorption in 300–600 nm. The blends of Th3(TPABT):PC71BM (1:3) comprising solution-processed organic solar cells give a power conversion efficiency (PCE) of 1.22 % with a high open circuit voltage (Voc) of 1.0 V. For TPA3(TPABT): PC71BM (1:3) device, a PCE of 1.24 % with a Voc of 0.82 V and a fill factor of 0.51 is achieved.