Efficient Organic Semiconductors Containing Fluorine-Substituted Benzothiadiazole for Solution-Processed Small Molecule Organic Solar Cells

The synthesis and photovoltaic characteristics of new organic semiconductors, [bisDMFA-Th]-BT-HxTh3 (1), [bisDMFA-Th]-MonoF-BT-HxTh3 (2), and [bisDMFA-Th]-DiF-BT-HxTh3 (3), are reported. These semiconductors have an unsymmetrical donor A–acceptor–donor B (DA-A-DB) framework composed of a benzothiadiazole (BT; fluorinated or unfluorinated) acceptor between two different donors, bisDMFA and terthiophene. We have demonstrated that these compounds are suitable for use in p-type organic semiconductors for high efficiency solution-processed small molecule organic solar cells (SMOSCs), for which we achieved a remarkable power conversion efficiency of 4.24% with a maximum Voc of 0.89 V. The fluorine substitution on BT decreased its HOMO level and increased hole mobilities of [bisDMFA-Th]-BT-HxTh3 derivatives, leading to an increased Voc in the SMOSCs and improved hole carrier transport properties of the material. In addition, we determined that the insertion of a TiOx functional layer into a bulk heterojunction (...