Fluorenylidene‐Cyclopentadithiophene Based Asymmetric Bistricyclic Aromatic Ene Compounds: Synthesis and Substituents Effects.

Low band gap materials have always been a focus of attention due to their potential applications in various fields. In this work, a series of asymmetric bistricyclic aromatic ene (BAE) compounds with fluorenylidene‐cyclopentadithiophene (FYT) skeleton were facially synthesized, which were modified with different substituents (−OMe, −SMe). The FYT core exhibit twisted C=C bond with dihedral angles around 30°, and the introduction of −SMe group can provide additional S⋅⋅⋅S interaction between molecules, which is conducive to the charge transporting. The UV‐Vis spectra, electrochemistry and photoelectron spectroscopy revealed that these compounds have relatively narrow band gaps, particularly, the −SMe modified compounds have slightly lower HOMO and Fermi energy levels than that of the −OMe modified compounds. Furthermore, PSCs devices were fabricated with the three compounds as HTMs, and FYT‐DSDPA exhibit the best performance among them, revealing the fine‐tuning band structure could influence properties of HTMs. [ABSTRACT FROM AUTHOR]