Regulating Donor Aggregation Structures via Main-Chain Engineering to Enable High-Performance and Mechanically Stable All-Polymer Solar Cells

초록

Controlling the aggregation behavior of conjugated polymers is crucial for optimizing the morphology and performance of all-polymer solar cells (all-PSCs), yet achieving precise regulation remains a formidable challenge due to the complex self-assembly of polymers in solution. Herein, we report a series of bithiophene imide-based terpolymer donors (OH1 to OH4) with systematically increased thiophene pi-bridge content to modulate solution-state aggregation. Increasing the pi-bridge content progressively enhances aggregation, leading to improved molecular ordering and a favorable fibrous network morphology in blend films. The optimized OH4:PY-IT blend achieves a remarkable power conversion efficiency (PCE) of 19.25% in binary all-PSCs-among the highest reported to date. Moreover, both intrinsically stretchable and flexible devices based on OH4:PY-IT exhibit superior mechanical durability, retaining 85.3% of initial PCE after 200 deformation cycles under 10% strain and 80.1% after 7000 bending cycles, while achieving high PCEs of 14.47% and 15.63%, respectively. This work establishes pi-bridge main chain engineering as a powerful strategy to control polymer aggregation and morphology, providing key insights for developing efficient and mechanically robust all-PSCs.

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