Fabrication of methylammonium lead bromide perovskite nanocrystals on chitosan for enhanced structural and optical stability.

Methylammonium lead bromide (MPB) perovskite nanocrystals (NCs) have emerged as promising materials for optoelectronic applications owing to their tunable bandgap, high photoluminescence quantum yield, and solution-processable fabrication. However, their long-term stability remains a major limitation for practical deployment. Although MPB exhibits greater environmental robustness than its iodide analogues, which is attributable to stronger PbBr bonds and a lower propensity for halide vacancy formation, it still undergoes phase decomposition under prolonged exposure to humidity, UV illumination, and elevated temperatures. This study investigates the encapsulation of the biopolymer chitosan (CT) by green chemical modification to form an MPB-CT composite, with the aim of mitigating the principal degradation pathways of MPB, including thermal, moisture-induced, photo-induced, ion-migration-related mechanisms, and defect minimisation. The synthesised MPB-CT complex displays an emission band at 535 nm. The MPB-CT demonstrated stable optical and structural properties even after 6 months. Overall, this approach provides insights into stability challenges and potential mitigation strategies that support the development of more durable materials for perovskite-based solar cells, light-emitting diodes, and photodetectors.