Unveiling the layer-resolved mechanical landscape of multilayer hybrid perovskite solar cells by statistical nanoindentation

Perovskite solar cells rely on complex multilayer architectures whose mechanical integrity is increasingly recognized as a critical factor for long-term operational stability. Despite extensive characterization of methylammonium lead iodide (MAPbI 3 ), the mechanical properties of emerging multi-cation perovskites within complete device stacks remain poorly understood. In this manuscript, we present a system-level mechanical characterization of two perovskite solar cell architectures using depth-resolved nanoindentation. By combining continuous stiffness measurements with statistical deconvolution, we isolate the elastic modulus and hardness of individual layers across the full device stack. The approach accurately reproduces reported values for common transport layers and MAPbI 3 , demonstrating robustness. We further report, for the first time, the intrinsic mechanical properties of the four-cation perovskite CsRbFAMAPb(IBr) 3 , which exhibits a similar elastic modulus but substantially higher hardness than MAPbI 3 . These results reveal a higher resistance to localized indentation-induced plastic deformation in multi-cation absorbers and underscore the importance of mechanical characterization when designing next-generation perovskite solar cells.