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.