Low-dimensional non-toxic A3Bi2X9 compounds synthesized by a dry mechanochemical route with tunable visible photoluminescence at room temperature

Abstract

We have synthesized fifteen inorganic and hybrid organic–inorganic non-toxic A₃Bi₂X₉ compounds (A = K⁺, Rb⁺, Cs⁺, CH₃NH₃⁺ and HC(NH₂)₂⁺; X = I⁻, Br⁻, Cl⁻) through dry mechanochemistry. We demonstrate that this synthetic method is very well suited to prepare compounds from poorly soluble precursors, allowing thus the preparation of so far unreported compounds. X-ray diffraction analysis demonstrates the high crystallinity of the so-formed ternary bismuth halides. Furthermore, we show that, through substitution of the A-cation and X-anion, the bandgap of these compounds can be tuned to absorb throughout the whole visible spectrum. As-prepared powders of Cs₃Bi₂Br₉ and Cs₃Bi₂I₉ without any passivating agents show room-temperature photoluminescence covering the visible spectrum from 450 nm to 800 nm, making them especially promising for white-light emission.