Mechanochemistry as a Green Route: Synthesis, Thermal Stability, and Postsynthetic Reversible Phase Transformation of Highly-Luminescent Cesium Copper Halides
G. Krishnamurthy Grandhi, Noolu Srinivasa Manikanta Viswanath, Han Bin Cho, Joo Hyeong Han, Seong Min Kim, Sungho Choi, Won Bin Im
Abstract
Cesium copper halides (CCHs) show promise for optoelectronic applications, and their syntheses usually involve high-temperatures and hazard solvents. Herein, the synthesis of highly luminescent and phase-pure Cs3Cu2X5 (X = Cl, Br, and I) and CsCu2I3 via a solvent-free mechanochemical approach through manual grinding is demonstrated. This cost-effective approach can produce CCHs on a scale of tens to hundreds of grams. Rietveld refinement analysis of the X-ray diffraction patterns of the as-synthesized CCHs reveals their structural details. Notably, the emission characteristics of green-emitting, chloride-based CCHs remain stable even at elevated temperatures—maintaining 80% of initial PL efficiency at 150 °C. Lastly, a postsynthetic reversible transformation between zero- and one-dimensional CCH materials is demonstrated, indicating the labile nature of their crystal structure. The proposed study suggests that mechanochemistry can be an alternative and promising synthetic tool for fabricating high-quality lead-free metal halides.