Structural and Thermal Photobehaviour Characterizations of (DPA)2MnBr4: An Environmentally Friendly Organic-Inorganic Hybrid Metal Halide Perovskite with a Reversible Emission Colour Switching for Anti-Counterfeiting and Solvent Vapours 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 prime candidates for next-generation light-emitting materials and advanced sensors. Here, we report on structural and photophysical characterizations of a novel Mn-based lead-free 0D perovskite ((DPA)2MnBr4, 1 where DPA is di-n-propylammonium) from 77 to 410 K. At room temperature (RT), the Mn centres present a tetrahedral coordination, yielding a green luminescent material. Upon cooling to 77 K, we observed an increase in its emission intensity and a decrease of its bandwidth. At temperatures above 310 K, a phase transition occurs, being complete at 353 K, and in which the tetrahedral configuration of the Mn centres is converted to a red-emitting octahedral one. At RT, 1 features 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. Additionally, 1 is demonstrated to specifically detect vapours of several common solvents, and of potential for developing encryption-decryption applications.