SIMS analysis of the degradation pathways of methylammonium lead-halide perovskites

This study employed time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate degradation pathways at the nanoscale, utilizing its capacity for in-depth chemical and structural analysis through various methods, including depth profiling and 3D analysis. A key focus is the matrix effect in ToF-SIMS, which alters secondary ion yields based on the sample matrix composition, influencing species identification and quantification. We show that this effect can be used to enhance the resolution of ToF-SIMS beyond its traditional limits, allowing for detailed imaging of the degradation process. Our findings indicate that the initial formation of PbI₂ phases, a crucial step in the degradation pathway triggered by environmental factors, can be traced and visualized. By investigating the sputtering yields and secondary ion formation, we reveal the nonlinear sputtering regimes present in MAPI, contributing to our understanding of the mechanisms driving perovskite degradation. The application of this enhanced analytical technique paves the way for improved degradation studies.