Photoinduced metastable cation disorder in metal halide double perovskites
Abstract
Lead-free perovskites have emerged as environmentally benign alternatives to lead-halide counterparts for optoelectronics. Among them, the double perovskite Cs2AgInCl6 family exhibits remarkable white-light emission with proper composition engineering, enabled by strong electron-phonon coupling and the formation of self-trapped excitons (STEs). Despite these advantages, the fundamental photo- and structural dynamics governing their excited-state behavior remain poorly understood. Here, we report a long-lived metastable phase in the Cs2AgInCl6 double perovskite family and unravel this process and the concomitant electronic and structural evolution using a suite of tools including transient optical spectroscopy, time-resolved X-ray diffraction (TR-XRD) and X-ray absorption (TR-XAS). We show that the photoinduced, transient metastable phase is associated with B-site (Ag-In) disorder, which induces a dramatically reduced optical bandgap. Supported by TR-XRD and first-principles calculations, the Ag-In disorder drives the formation of Ag-rich and In-rich domains with millisecond lifetimes, with lifetimes increasing at lower temperatures. TR-XAS further reveals that photogenerated STEs oxidize Ag+ to Ag2+, facilitating this highly temporally asymmetric order-disorder transition. Our findings demonstrate a new mechanism, mediated by hole-localized STE formation, that enables prolongation of transient light-induced states to the multi-millisecond regime in double perovskites, opening possibilities to harvesting the functional properties of metastable phases of these materials.
Keywords
Cite
@article{arxiv.2601.16404,
title = {Photoinduced metastable cation disorder in metal halide double perovskites},
author = {Shunran Li and Burak Guzelturk and Conrad A. Kocoj and Donald A. Walko and Du Chen and Haidan Wen and Xian Xu and Xiaoming Wang and Bongjun Choi and Borui Li and Zhibo Kang and Cunming Liu and Suchismita Sarker and Benjamin T. Diroll and Xiaoyi Zhang and Yong Q. Cai and Yu He and Deep Jariwala and Yanfa Yan and Diana Y. Qiu and Peijun Guo},
journal= {arXiv preprint arXiv:2601.16404},
year = {2026}
}