Solvent-Free Grinding Synthesis of Hybrid Copper Halides for White Light Emission

Lead-free metal halides (LMHs) have recently attracted numerous attention in solid-state lighting due to their unique structures and outstanding optoelectronic properties. However, conventional preparation processes with the utilization of toxic organic solvents and high temperatures seem to impede commercial applications of LMHs. In this work, we successfully synthesize Cu⁺-based metal halides (TMA)₃Cu₂Br_5-Cl (TMA: tetramethylammonium) with high photoluminescence quantum yields (PLQYs) via a solvent-free mechanical grinding method. By changing the ratio of halide ions (Cl^- and Br^-) in precursors, the emission wavelength of the prepared (TMA)₃Cu₂Br_5-Cl can be tuned from 535 to 587 nm, which are employed as emitters in the fabrication of white-light-emitting diodes (WLEDs). The achieved WLEDs exhibit a high color rendering index value of 84 and standard Commission Internationale de l'Éclairage (CIE) coordinates of (0.324, 0.333). This feasible and solvent-free preparation strategy not only promotes the mass production of LMHs but also highlights the promising potential for efficient solid-state illumination.