Copolymers based on trialkylsilylethynyl-phenyl substituted benzodithiophene building blocks for efficient organic solar cells

Abstract

Non-fullerene acceptors have received a great deal of attention over the past several years, and numerous modifications on the molecular structures significantly boosted the power conversion efficiencies (PCEs) of organic solar cells (OSCs). To be a match, a promising polymer donor is urgently needed. Herein, we report a wide bandgap donor with alternating fluorinated benzotriazole (FTAZ) and triisopropylsilylethynyl-phenyl substituted benzodithiophene. Strategically, the lateral benzene and acetylene motifs induce a down-shift of the HOMO energy level, and the alkylsilyl facilitates inter-chain interactions and modulates the solubility. The new polymer exhibits a strong solution pre-aggregation ability that influences the intermixed morphology and optimizing methods of OSCs. When blended with the easily accessible acceptor IDIC, a respective PCE of 7.81% with a V_oc of 0.928 V has been demonstrated. We investigated the impact of molecular weights on the optical and electrochemical properties, charge transport, blend morphology, and photovoltaic parameters, and the result indicates that a high M_n is desired for improving the quality of the solution-processed films. The acquired results reveal that trialkylsilylethynyl-phenyl is a promising multi-functional side chain scaffold for developing promising conjugated molecules.