Interlocked Interface Enhances Mechanical Integrity for Thermal‐Cycling‐Stable Perovskite Solar Cells With 26.82% Certified Efficiency

Perovskite solar cells (PSCs) experience mechanical damage and failure (i.e. degradation and fracture) induced by temperature changes under thermal cycling. However, few studies have been able to simultaneously suppress interface delamination and delay chemical degradation to ensure the mechanical integrity of perovskite film under thermal shock, making it challenging to improve the thermal cycling stability of PSCs. We report a universal interlocking strategy via the modification of polymethyl(hydro)/polymethylvinylsilazane (PHVS), which achieves interfacial interlocking through the condensation reactions with substrates, hydrogen bonding with the perovskite film, and a self-crosslinking reaction. The interlocked interface significantly enhances the interfacial adhesion toughness and releases the residual stress of the perovskite film, thereby suppressing the interface delamination and delaying the chemical degradation under thermal cycling. The PHVS-modified PSCs exhibit a certified efficiency of 26.82%. The encapsulated PSCs retain 96% of their original efficiency after 200 cycles of thermal cycling testing, and the perovskite modules maintain 95% of their original efficiency after 1000 h, day and night, outdoor testing. This work highlights the significance of enhancing the mechanical integrity of perovskite films under thermal cycling and provides a promising approach for achieving thermal cycling-stable PSCs with high efficiency.