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arXiv · 2511.16770

Light-Induced Lattice Coherence and Emission Enhancement in PTM-Passivated CsSnI3 Perovskites

Thomas Y. Adams·Bruce Barrios·Michael Ziegenfus·Hui Cai·Sayantani Ghosh
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Abstract

Metal halide perovskites continue to lead in optoelectronic applications, but the toxicity of lead has driven efforts to identify environmentally benign alternatives. Cesium tin iodide is one such, with a direct bandgap and near-infrared emission, though its performance is limited by instability. We show that phthalimide (PTM) passivation during single crystal growth enhances optical output and ambient stability. Under continuous excitation, PTM-passivated microscale crystals show up to a nearly one order of magnitude increase in photoluminescence (PL) quantum yield, accompanied by reversible sharpening of a low-frequency Raman mode associated with Cs rattling. This reveals dynamic, light-induced lattice reordering that passivates trap states and enhances radiative recombination. Mechanical grinding yields nanocrystals with redshifted, narrowed PL, consistent with a relaxed polymorph and reduced inhomogeneous broadening. Despite increased surface area, PTM remains effective in preserving near-infrared emission in nanocrystals as well. Power-dependent PL reveals distinct carrier dynamics, where microcrystals show redshift due to bandgap renormalization, while nanocrystals show blueshift and elevated carrier temperatures (300 to 1900 K), consistent with hot-carrier recombination. Extended illumination reveals reversible optical changes, including PL modulation, reflecting dynamic light-matter interactions and evolving defect landscapes. These results identify PTM-passivated Cesium tin iodide as an ideal platform for probing morphology-dependent carrier relaxation and light-induced vibrational coherence in lead-free perovskites.

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Thomas Y. Adams, Bruce Barrios, Michael Ziegenfus, Hui Cai, Sayantani Ghosh. 2025-11-20. Light-Induced Lattice Coherence and Emission Enhancement in PTM-Passivated CsSnI3 Perovskites. https://arxiv.org/abs/2511.16770

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