Improving Solubility And Photovoltaic Properties Of The Star-Shaped Molecules By Synergistic Effect Of Central Tris(2-Methoxyphenyl)Amine And Branched Fluorine Substituent

Three star-shaped small molecular donors of TOBTC, TOBTC-1F and TOBTC-2F were developed, which adopt tris (2-methoxyphenyl)amine (TPA-OMe) as electron-donating core, as well as nonfluoro-, monofluoro- and difluoro-substituted benzo-thiadiazole as electron-withdrawing branch, respectively. The improved solubility and hole mobility were obtained in comparison to their analogs using TPA as core. More interestingly, the TOBTC-2F: PC71BM blend exhibited highest hole mobility (mu(h)) of 8.5 x 10(-4) cm(2)V(-1)s(-1) and its solution-processed organic solar cell displayed the best photovoltaic properties with a power conversion efficiency of 4.5% at an area of 10 mm(2) without any additive and annealing treatment. Here, the mu(h) value is 10 times higher than that of its TPA based analog:PC71BM blend. It indicates that the synergistic effect of the TPA-OMe unit in core and fluorine substituents in benzo-thiadiazole is available to improve solubility, mobility and photovoltaic properties of the star-shaped small molecular donors.