Reinforced Perovskite‐Substrate Interfaces via Multi‐Sited and Dual‐Sided Anchoring

Abstract Interfacial reliability is critical for the long‐term stability of perovskite solar cells (PSCs), yet the perovskite‐substrate interface represents the most vulnerable part in high‐efficiency devices. Here, this interface, by incorporating a dual‐sided anchoring polymeric hole‐transporting interlayer is reinforced with abundant coordinating pyridyl units as side chains, which induces strong adhesion between the perovskite and substrate by forming multidimensional interactions with adjacent layers. This simultaneously enhances the mechanical strength through effective distribution and dissipation of mechanical stress and the electronic quality of the perovskite‐substrate interface through defect passivation. The resulting PSCs exhibit a high power conversion efficiency (PCE) of 26.8% (certified at 26.6%). With a more robust perovskite composition, devices maintain 98% of their initial PCE of ≈26% after maximum‐power‐point tracking at 85 °C for 1500 h. These devices exhibit excellent fatigue resistance under thermal cycling (‐40 to 85 °C), retaining 93% efficiency after undergoing 900 cycles.