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Three fused-ring electron acceptors ( SIDIC , DIDIC and TIDIC ) were designed and synthesized using single bond, vinylene and acetylene units linked indaceno[3,2- b ]dithiophene dimers as electron-rich cores and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone as electron-deficient termini. These molecules exhibit strong absorption from 550 to 900 nm with large attenuation coefficients of 1.8–2.0 × 10 5 M −1 cm −1 and high electron mobilities of 2.2–4.9 × 10 −3 cm 2 V −1 s −1 . In combination with wide-bandgap polymer FTAZ as a donor, organic solar cells exhibit efficiencies of 9.3–13.1%. Effects of the linking units on optical, electronic, morphologic, and photovoltaic properties were revealed. Relative to SIDIC , vinylene-bridged DIDIC shows red-shifted absorption, while acetylene-bridged TIDIC shows blue-shifted absorption. Compared with SIDIC and DIDIC , TIDIC has a lower HOMO, higher electron mobility, and higher device efficiency. 

Two polymer donors, FTAZ and J71 , and two fused-ring electron acceptors, ITIC1 and ITIC2 , are used to investigate the effects of conjugation dimension on the performance of organic solar cells (OSCs). FTAZ and J71 , and ITIC1 and ITIC2 share the same molecular backbone, respectively, while J71 and ITIC2 possess conjugated thienyl side chains. The addition of conjugated side chains slightly red-shifts the absorption spectra and lowers the bandgap due to the extended 2D conjugation. Conjugated side chains on the acceptor induce the self-aggregation of the acceptors, while conjugated side chains on the donor increase the miscibility of the donors and acceptors, thus optimizing the morphology of the active layers. The blends based on mixed combinations, namely 1D donor/2D acceptor and 2D donor/1D acceptor, show better performance relative to 1D donor/1D acceptor and 2D donor/2D acceptor.