Photo-induced halide redistribution in organic–inorganic perovskite films

TLDR

Organic–inorganic perovskites such as CH₃NH₃PbI₃ achieve power‑conversion efficiencies above 21 % yet still suffer from non‑radiative recombination and poorly understood illumination‑induced dynamics. The study employs confocal photoluminescence microscopy combined with chemical imaging to correlate local photophysical changes with composition in CH₃NH₃PbI₃ films under illumination. By imaging the same regions with time‑of‑flight secondary‑ion‑mass spectrometry, the authors map photobrightening to net iodine migration, linking composition changes to photophysical behavior. The results show that illumination reduces trap‑state density by an order of magnitude, producing photobrightening, and that this is driven by iodine migration, illustrating the interplay of mobile halides, traps, and carriers that governs optoelectronic performance.

Abstract

Abstract Organic–inorganic perovskites such as CH 3 NH 3 PbI 3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH 3 NH 3 PbI 3 films under illumination. We demonstrate that the photo-induced ‘brightening’ of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.