Polymorphous Structural Landscapes Drive Broadband Optical Response in Water-Stable Mixed-Halide Antiperovskites
Year: 2026
Type: preprint
Abstract: Silver chalcohalide antiperovskites have emerged as low-toxicity semiconductors with strong near-infrared absorption, although their unusual composition-dependent optical properties, including inverse bandgap bowing, remain poorly understood. Here, Ag3SI1-xBrx solid solutions were synthesized by a solvent-free mechanochemical route and investigated by structural and optical characterization, ultrafast spectroscopy, and first-principles calculations. While all compositions retain an average cubic Pm-3m structure and exhibit a Vegard-like lattice contraction with increasing Br content, strongly nonlinear optical behavior and multiple absorption onsets are observed. First principles calculations reveal that these alloys are more appropriately described by an ensemble of electronically distinct low-energy configurations arising from an underlying polymorphous energy landscape. This configurational diversity redistributes band-edge spectral weight, enables quasi-direct transitions at Γ, and provides a microscopic explanation for the broadband absorption and anomalous bandgap evolution. Transient absorption spectroscopy further supports the presence of different compositiondependent electronic environments and reveals prolonged carrier lifetimes for mixed-halides, consistent with alloy-disorder-induced localization. From an applicative perspective, these materials show remarkable water stability and efficient photothermal energy conversion enabling their use in a proof-of-concept solar water evaporation setup. These findings establish Ag3SI1-xBrx antiperovskites as water-stable, low-toxicity, broadband-absorbing materials and demonstrate the importance of polymorphous local structure in governing their optical response.
Source: ChemRxiv
Institutions: Universidad Politécnica de Cartagena, Cyprus Institute, Czech Technical University in Prague, Indian Institute of Technology Roorkee, University of Southern California, Sogang University, CSIR National Physical Laboratory of India, Academy of Scientific and Innovative Research, National Institute for Materials Science
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213283726