Synthesis and Applications of Cyano-Vinylene-Based Polymers Containing Cyclopentadithiophene and Dithienosilole Units for Photovoltaic Cells

Two b-cyano-thiophenevinylene-based polymers containing cyclopentadithiophene (CPDT-CN) and dithienosilole (DTS-CN) units were synthesized via Stille coupling reaction with Pd(PPh3)4 as a catalyst. The effects of the bridged atoms (C and Si) and cyano-vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic proper- ties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about � 5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about � 3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of