Novel D–A−π–A-Type Organic Dyes Containing a Ladderlike Dithienocyclopentacarbazole Donor for Effective Dye-Sensitized Solar Cells

A novel ladderlike fused-ring donor, dithienocyclopentacarbazole (DTCC) derivative, is used to design and synthesize three novel donor–acceptor−π–acceptor-type organic dyes (C1–C3) via facile direct arylation reactions, in which the DTCC derivative substituted by four p-octyloxyphenyl groups is served as the electron donor and the carboxylic acid group is used as the electron acceptor or anchoring group. To fine-tune the optical, electrochemical, and photovoltaic properties of the three dyes, various auxiliary acceptors, including benzo[2,1,3]thiadiazole (BT), 5,6-difluorobenzo[2,1,3]thiadiazole (DFBT), and pyridal[2,1,3]thiadiazole (PT), are incorporated into the dye backbones. The results indicate that all of the three dyes exhibit strong light-capturing ability in the visible region and obtain relatively high molar extinction coefficients (>31 000 M–1 cm–1) due to their strong charge transfer (CT) from donor to acceptor. Moreover, theoretical model calculations demonstrate fully separated highest occup...