Enhancing Photovoltaic Performance of Copolymers Containing Thiophene Unit with D–A Conjugated Side Chain by Rational Molecular Design

Rational molecular design of conjugated polymers and cautious optimization of morphologies of the active layer are critical for developing high performance polymer solar cells (PSCs). In this work, we designed and synthesized a new thiophene monomer TBTF attaching donor–acceptor (D–A) conjugated side chain with fluorinated 4,7-dithien-5-yl-2,1,3-benzodiathiazole (BTF) as acceptor unit, and synthesized two new two-dimension-conjugated (2D-conjugated) copolymers, P(BDT-TBTF) and P(BDT-TBTF/DPP), for the application as donor materials in PSCs. P(BDT-TBTF) is a new side chain D–A copolymer of benzodithiophene (BDT) and TBTF units, and P(BDT-TBTF/DPP) is a ternary D–A copolymer of BDT, TBTF and pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) units. The introduction of TBTF unit with D–A conjugated side chain and DPP unit forming the ternary copolymer provides the opportunity to tune the optoelectronic properties of the resulting polymers. As expected, the binary copolymer P(BDT-TBTF) shows an enhanced absorption coeffic...