Triisopropylsilyl-Substituted Benzo[1,2-b:4,5-c ']dithiophene-4,8-dione-Containing Copolymers with More Than 17% Efficiency in Organic Solar Cells

Abstract

Considering the special functions of fused-ring aromatic building blocks and Si-atom in high-performance donor-acceptor-conjugated materials at the same time, herein the synthesis of a novel fused-ring tricyclic heterocycle, triisopropylsilyl-substituted benzo[1,2-b:4,5-c ']dithiophene-4,8-dione (iBDD-Si), an isomer of well-known benzo[1,2-c:4,5-c ']dithiophene-4,8-dione is presented. The iBDD-Si-based copolymer series (PM6, PM6-5Si, PM6-10Si, and PM6-15Si) is synthesized via Stille polymerization, revealing fine-tuned optical and electrochemical properties, and molecular packing with varying iBDD-Si contents in the backbone. Organic solar cells are fabricated by pairing the copolymer donors with nonfullerene acceptor N3 and characterized. High power conversion efficiency of more than 17% is achieved using the PM6-5Si-based solar cell, which is attributed to the balanced charge transport, enhanced charge generation/dissociation kinetics, and minimized total energy and recombination losses. It is demonstrated that iBDD-Si is a promising backbone toolbox for various high-performance conjugated materials.