A Fluorinated Imide‐Functionalized Arene Enabling a Wide Bandgap Polymer Donor for Record‐Efficiency All‐Polymer Solar Cells

Abstract All‐polymer solar cells (all‐PSCs) present compelling advantages for commercial applications, including mechanical durability and optical and thermal stability. However, progress in developing high‐performance polymer donors has trailed behind the emergence of excellent polymer acceptors. In this study, we report a new electron‐deficient arene, fluorinated bithiophene imide (F‐BTI) and its polymer donor SA1, in which two fluorine atoms are introduced at the outer β ‐positions in the thiophene rings of BTI to fine‐tune the energy levels and aggregation of the resulting polymers. SA1 exhibits a deep HOMO level of −5.51 eV, a wide bandgap of 1.81 eV and suitable miscibility with the polymer acceptor. Polymer chains incorporating F‐BTI result in a highly ordered π–π stacking and favorable phase‐separated morphology within the all‐polymer active layer. Thus, SA1 : PY‐IT‐based all‐PSCs exhibit an efficiency of 16.31 % with excellent stability, which is further enhanced to a record value of 19.33 % (certified: 19.17 %) by constructing ternary device. This work demonstrates that F‐BTI offers an effective route for developing new polymer materials with improved optoelectronic properties, and the emergence of F‐BTI will change the scenario in terms of developing polymer donor for high‐performance and stable all‐PSCs.