Chlorinated Bithiophene Imide-Based n-Type Polymers: Synthesis, Structure–Property Correlations, and Applications in Organic Electronic Devices

Developing electron-deficient (hetero)arenes with optimized geometries and electronic properties is imperative for advancing n-type polymers and organic electronic devices. We report here the design and synthesis of two chlorinated imide-functionalized electron-deficient heteroarenes, namely chlorine-substituted bithiophene imide (ClBTI) and its fused dimer (ClBTI2). The corresponding polymers show a near-planar framework, appropriate frontier molecular orbital levels, and good solubility. When integrated into organic thin-film transistors, ClBTI2-based n-type polymer afforded unipolar electron mobility of up to 0.48 cm² V⁻¹ s⁻¹. The binary all-PSCs based on PM6 and new polymers show a power conversion efficiency (PCE) exceeding 1%. Interestingly, by introducing these polymers with ordered structure, high crystallinity, and sizable electron mobility as the third component into the host system PM6:PY-IT, continuous interpenetrating networks with large fibrillar structures can be formed. Investigations of charge transfer kinetics and energy loss analyses unveiled that ClBTI2-based n-type polymer P(ClBTI2-BTI) enables optimized charge transport, reduced charge recombination, and minimized non-radiative loss within the all-polymer ternary blends, yielding a remarkable PCE of 19.35% (certified: 19.20%) through optimizing the state-of-the-art PM6:PY-IT blend. The structure–property–performance relationships provide valuable insights into the design of electron-deficient (hetero)arenes and n-type polymers, marking a great progress in the development of high-performance n-type polymers for organic electronic devices.