Site-selective alkali ion alloying in double perovskites via liquid-assisted mechanosynthesis revealed by solid-state NMR
Year: 2026
Type: preprint
Abstract: Lead-free halide double perovskites are promising materials for light-emitting and photovoltaic applications. However, compositional tuning of their structural and optoelectronic properties has largely focused on B-site and halide alloying. In this work, we show that Cs + on the perovskite A-site of Cs 2 AgInCl 6 can be partly substituted with Rb + using simple apolar liquid-assisted mechanochemistry. By comparing Rb + with Na + substitution we show that ion size drives the site-selectivity of alkali ion substitution into double perovskites, with Na + preferentially occupying the perovskite B-site. By combining multinuclear solid-state nuclear magnetic resonance spectroscopy with X-ray diffraction, we show that Rb+ not only enters the double-perovskite site-selectively but also induces local symmetry breaking of the cubic structure, comparable to the effect of B-site Na + /Ag + alloying, with important implications for symmetry-forbidden photoluminescence emissivity. This work extends the tuneable compositional range of lead-free double perovskites to include A-site mixing while also establishing the site-selectivity of alkali ion speciation into the double perovskite structure.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Awards: Atomistic Design of Photoabsorbing Materials, G2656698611, Analysis and Modelling Service for Engineering Materials Studied with Neutrons, G3391484441, G4197476736, G4632909464, G5404377299, G6253828198, The UK High-Field Solid-State NMR National Research Facility, G6831956292, Atomic-Level Insight into Photoinduced Transformations in Perovskite Optoelectronics, Solid-State NMR at 1.0 GHz: A World-Leading UK Facility to Deliver Advances in Chemistry, Biology and Materials Science, NAISS, G978999556
OpenAlex ID: W7204798298