# Unravelling Mixed Organic‐Halide Perovskite Degradation Under Extrinsic Factors

## TL;DR

This paper investigates how environmental factors like humidity and temperature affect perovskite solar cells and uses advanced techniques to understand and improve their stability.

## Contribution

The study introduces neutron reflectometry combined with simulations to reveal interfacial layer formation in perovskite films under environmental stress.

## Key findings

- Hybrid perovskite films on TiO2 show enhanced stability under environmental stress.
- Interfacial layers containing FAI, PbI2, and MABr form at the base of the film.
- Molecular dynamics simulations support experimental findings on material degradation.

## Abstract

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.

Advanced characterization methods like neutron reflectometry (NR) provide insights into degradation by using isotope substitution to track components. NR indicates improved stability of hybrid perovskite films on TiO2 and reveals interfacial layers at the film base, likely containing FAI, PbI2, and MABr. Molecular dynamics simulations support these experimental findings under various environmental conditions to better understand material performance and stability.