Mechanochemical Synthesis of Phase-Pure CsCu2I3 and Cs3Cu2I5 Phosphors Regulated by Polar Solvents and Their Application in Tunable Chromaticity LEDs

Lead halide perovskites have garnered interest in light-emitting diode (LED) applications due to their strong emission and tunable properties. However, conventional synthesis methods involve energy-intensive thermal processes and hazardous organic solvents, raising environmental concerns. In this study, we report a simple and eco-friendly mechanochemical approach that produces phase-pure blue-emitting Cs3Cu2I5 (emission at 440 nm) and yellow-emitting CsCu2I3 (emission at 570 nm) phosphors through polarity modulation and control of grinding duration. Our comprehensive analysis of the phase transitions during mechanochemical synthesis reveals that pure Cs3Cu2I5 was synthesized from a 3:2 precursor molar ratio in ethanol for 30 min, while pure CsCu2I3 was obtained from a 1:2 precursor molar ratio in an aqueous solution for 7.5 min. Moreover, Raman spectroscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy analyses confirmed that phase-pure phosphors were achieved through these methods. Finally, we fabricated a series of color-adjustable LEDs by mixing Cs3Cu2I5 and CsCu2I3 phosphors in different proportions. This demonstrates the potential of our mechanochemical synthesis for the efficient, large-scale production of next-generation lighting materials with tunable emission.