Structural and thermal photobehaviour characterizations of (DPA)2MnBr4: an environmentally friendly organic–inorganic hybrid metal halide perovskite with reversible emission colour switching for anti-counterfeiting and solvent vapour photosensing

Abstract

Zero-dimensional (0D) lead-free hybrid manganese halides are emerging as game-changers in photonic technologies, offering a powerful combination of low cost, high emission efficiency, and exceptional optical tunability. Their outstanding luminescence makes them promising candidates for next-generation light-emitting materials and advanced sensors. Herein, we report the structural and photophysical characterization of a novel Mn-based lead-free 0D perovskite ((DPA)₂MnBr₄, 1, where DPA is di-n-propylammonium), at temperatures ranging from 77 to 410 K. At room temperature (RT), the Mn centres exhibit tetrahedral coordination, yielding a green luminescent material. Upon cooling to 77 K, we observed an increase in its emission intensity and a decrease in its bandwidth. At temperatures above 310 K, a phase transition occurs, which was completed at 353 K, and the tetrahedral configuration of the Mn centres converts to a red-emitting octahedral configuration. At RT, 1 exhibits a green photoluminescence quantum yield of 50% and a lifetime of 0.328 ms. Interestingly, the green-to-red emission conversion is reversible and can be switched several times by heating to 353 K and cooling to RT, highlighting its potential for encryption–decryption applications. In addition, 1 shows selective detection of vapours from several common solvents.