Tuning the Intermolecular Electrostatic Interaction toward High‐Efficiency and Low‐Cost Organic Solar Cells

Abstract Organic solar cells (OSCs) have achieved much progress with rapidly increasing power conversion efficiencies (PCEs). It should be noted that the top‐performance OSCs are generally consisted of active materials with complex chemical structures, resulting in high costs. Here, combining the material design and morphology control, high‐efficiency OSCs are fabricated by a low‐cost donor: acceptor blend. A completely non‐fused electron acceptor named Tz is designed and synthesized via introducing thiazole units on both sides of a bithiophene core, which shows an outstanding PCE of 13.3% with a typical polythiophene donor. More importantly, optimization guidelines are presented to get excellent morphology for low‐cost donor:acceptor systems. Three polythiophenes are selected, poly(3‐hexylthiophene) and its two derivatives with electron‐withdrawing substitutions (PDCBT and PDCBT‐2F), as donors to fabricate the cell devices. The computational and experimental data reveal that decreasing the electrostatic interaction between polythiophene and Tz is the key to getting a suppressed miscibility and thus a high phase purity. This study provides insight into the molecular design and donor:acceptor matching requirements for high‐efficiency and low‐cost OSCs.