Bilateral Chemical Bridging Enables Efficient Ultra‐Flexible Perovskite Solar Cells With Improved Extreme Mechanical Durability

Abstract Ultra‐flexible perovskite solar cells (UF‐PSCs) with superior power‐to‐weight ratio have enormous application potential in the aerospace field. However, structural integrity and functional stability of UF‐PSCs remains a significant challenge under such extreme conditions, which are mainly caused by insufficient bonding and thus damage of the physically‐contact‐only perovskite buried interfaces. Herein, to solve this problem, imidazole bromide (IMBr) interface linker with bilateral linking ability is employed to harmonize the bonding between perovskite and substrate. It is demonstrated that the imidazole cations can anchor to poly(3,4‐ethlenedioxythiophene) polystyrene sulfonate through hydrogen bonds and connect to Pb‐I by coordination bonds, resulting in low‐defect and robust perovskite‐substrate interface at the same time. The interfacial tensile test reveals that the tensile resistance of the buried interface is increased by 2.76 times, which will directly improve the ultimate bending resistance of UF‐PSCs. Finally, the strategy increased the power conversion efficiency (PCE) of UF‐PSCs from 16.87% to 20.45%, the highest efficiencies reported so far. The UF‐PSCs demonstrates unprecedented bending stability after extreme deformation, retaining 82.4% and 89.4% of their initial PCEs after 10,000 and 200 cycles at radii of 0.5 and 0.25 mm, respectively. This work advances the potential application of UF‐PSCs in the aerospace sector.