Spatiotemporal Monitoring of MAPbI3 Films under Outdoor Conditions by Using Hyperspectral Imaging

Abstract

The heterogeneous and environmentally induced degradation of lead halide perovskite films represents one of the major challenges for their practical implementation in photovoltaic devices, yet conventional spatially integrated characterization techniques remain inadequate for resolving this complexity. Here, we present hyperspectral imaging (HSI) as a nondestructive, spatially resolved diagnostic platform for monitoring the spatiotemporal degradation of methylammonium lead iodide (MAPI) films under uncontrolled atmospheric conditions. Pixel-wise Tauc analysis across a 0.754 cm2 analyzed area (∼1,400 pixels) enables simultaneous tracking of bandgap distributions associated with the photoactive MAPI phase, the hydrated intermediate MAPI-H2O, and the PbI2 degradation product over 21 days. Ternary phase trajectory maps reveal that degradation proceeds through inherently heterogeneous, multipathway mechanisms. The incorporation of diaminoethane as a bifunctional additive into the perovskite precursor solution (DAE-PVK) markedly enhances the material stability, extending the stability of the MAPbI3 phase up to days 10–14 and delaying PbI2 formation by around 1 week relative to the reference film (ref-PVK). These HSI-derived findings are corroborated by X-ray diffraction, scanning electron microscopy, contact angle measurements, and steady-state photoluminescence. DAE incorporation promotes an around 2.76-fold increase in grain size, enhanced surface hydrophobicity (contact angle: 63.8° vs 50.3°), and improved photovoltaic stability over 50 days, wherein DAE-based devices retain their initial power conversion efficiency while reference devices lose approximately 20%. This work establishes HSI-based bandgap and phase mapping as an early stage diagnostic strategy for assessing perovskite film stability prior to full device integration, providing a practical screening methodology for the rational design of more durable perovskite photovoltaic technologies.