Phase-selective synthesis of lead-free CsMnBr₃ and Cs₃MnBr₅ nanocrystals dependent on solvent concentration

We demonstrate the crystal phase-selective synthesis for lead-free cesium manganese bromine perovskite nanocrystals synthesized by the modified hot-injection method due to changing the concentration of solvent (trioctylphosphine; TOP). The compositions synthesized were determined by the amount of TOP solvent, and the structure phase of the nanocrystals was selected from hexagonal CsMnBr₃ to tetragonal Cs₃MnBr₅ as the amount of TOP solvent increased. The emission peaks of CsMnBr₃ and Cs₃MnBr₅ nanocrystals were observed at 650 nm (red) and 520 nm (green), respectively. After a durability test at 85°C and 85% humidity for 24 h, the lead-free perovskite CsMnBr₃ nanocrystal powder maintained its initial emission intensity, and the metal halide Cs₃MnBr₅ nanocrystal powder exhibited an increase in red emission due to the post-synthesis of CsMnBr₃ nanocrystals.