Simple-structure small molecular acceptors based on a benzodithiophenedione core: synthesis, optoelectronic and photovoltaic properties

Abstract

It is crucial to develop high-efficiency simple-structure small molecular acceptors (SMAs) having a shortened synthetic route and lower cost. Herein, two simple SMAs, BDDTTIC and BDDTTIC-4F, with the A–D–A′–D–A architecture were primarily synthesized via a simple three-step route in high yields, based on the central acceptor (A′) unit of benzodithiophenedione (BDD), the spacing donor (D) unit of thienothiophene (TT) and the terminal acceptor (A) unit of dicyanomethylene indanone (IC) or its fluorinated analog (IC-4F). The influence of the molecular structure on the photophysical, electrochemical and photovoltaic properties was primarily studied. The results show that the fluorine-free BDDTTIC exhibits better solubility and higher LUMO energy levels (−3.81 eV) than the fluorinated BDDTTIC-4F. Moreover, the PM6:BDDTTIC based OSCs show better photovoltaic properties than the PM6:BDDTTIC-4F based OSCs by optimizing the polymer donor material, donor/acceptor ratio and 1-chloronaphthalene additive ratio. An increasing power conversion efficiency of 5.62% with a high open-circuit voltage of 0.95 V was obtained in the optimal PM6:BDDTTIC-based device, which is almost two times higher than that of the optimal PM6:BDDTTIC-4F-based device. This work provides a potential direction to further construct high-efficiency BDD-based SMAs.