Triisopropylsilylethynyl substituted benzodithiophene copolymers: synthesis, properties and photovoltaic characterization†
We demonstrated herein the facile synthesis of triisopropylsilylethynyl (TIPS) functionalized benzo[1,2-b:4,5-b′]dithiophene (BDT). Three new TIPSBDT-based donor–acceptor alternating copolymers were further developed by Pd-catalyzed Stille coupling. The effect of accepting unit structure on the optical, electrochemical and energy levels of the polymer was studied. The positive impact of PFN layer, high-boiling solvents processing, polar solvent treatment and solvent annealing on the performance of polymer : PC71BM bulk heterojunction solar cells was revealed. The best devices delivered a power conversion efficiency of 5.46% when blend films processed using o-dichlorobenzene with 3 vol% DIO and treated with the optimization of THF annealing and insertion of PFN layer. The device performance was correlated with the morphology evolution of blend films processed with solvent choice, methanol treatment and THF annealing.