Multiple chlorinations to improve the performance of unfused electron-acceptor based organic photovoltaic cells

Abstract

Organic solar cells (OSCs) with non-fused ring acceptors have improved steadily in recent years, benefiting from the subtly molecular regulation and well-organized blend film morphology. Herein, a simple and effective strategy was proposed for finely chemical structural regulation from a well-established molecule BDTC-4Cl. With this, two unfused acceptors namely Cl-4F and Cl-4Cl were designed and synthesized. After adding a chlorine atom into the core unit and a fluorine atom into the end group, the molecule Cl-4F achieved high efficiency of 10.38% and short-circuit current density (JSC) of 19.59 mA cm−2, which is superior to that of the control molecule BDTC-4Cl (9.42%) without chlorine atom in the central backbone. When using multi-chlorination in the end group and backbone, the Cl-4Cl based device obtained an exciting efficiency of 10.88%, a fill factor (FF) of 65.2%, and a JSC of 20.07 mA cm−2. The Cl-4Cl-based device's power conversion efficiency (PCE) ranks among the highest values for non-fused ring acceptors with a benzodithiophene (BDT) core, demonstrating the feasibility of using multiple chlorination strategies to design and construct novel non-fused ring acceptors for high-performance OSCs.