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.