Unravelling Mixed Organic‐Halide Perovskite Degradation Under Extrinsic Factors

Over time, halide perovskite materials used in solar cell applications, can experience several degradation mechanisms, including moisture ingress, thermal stress, light-induced degradation, and ion migration, all of which lead to reduced performance and stability in devices. Among these, moisture ingress is particularly critical for the stability of perovskite solar cells. The perovskite structure is highly sensitive to water molecules, which can trigger chemical reactions and phase transitions. While significant progress has been made in mitigating perovskite degradation-through strategies such as interface engineering, encapsulation techniques, and compositional optimization-further research is necessary to develop perovskite solar cells with the long-term stability required for commercial use. Advanced characterization techniques like neutron reflectometry (NR) offer valuable insights into degradation mechanisms by using isotope substitution to track specific components within the material. For that, this work presents first, how affect the humidity and temperature in the full device, second, their characterization to unravel the degradation mechanism with NR and finally, corroborates the results with simulation techniques. NR results suggest enhanced stability of hybrid perovskite films deposited on TiO₂ layers, and indicate the formation of interfacial layers at the base of the film, likely composed of FAI, PbI₂, and MABr. The obtained experimental results are supported by molecular dynamics simulations modelling.