Rapid synthesis and mechanochemical reactions of cesium copper halides for convenient chromaticity tuning and efficient white light emission

Lead halide perovskites are emerging as important candidates for many photoelectric applications; however, the toxicity of the heavy metal Pb poses a barrier to such applications. Thus, intense research efforts have been directed to developing lead-free photoelectric materials. Here, we report on the synthesis and transformation of the cesium copper halides Cs 3 Cu 2 I 5 and CsCu 2 I 3 . These Cu based halide compounds are synthesized through a rapid antisolvent crystallization process with the use of isopropanol. The Cs 3 Cu 2 I 5 has blue emission at 445 nm with a full width at half maximum (FWHM) of ∼81.7 nm; CsCu 2 I 3 has a yellow emission at 575 nm with a FWHM of ∼119.9 nm. Notably, these two compounds can be interconverted through mechanochemical reactions. Therefore, standard white light emission can be obtained from a mixture of these two halides at an appropriate ratio and a white light emitting diode device is fabricated. We report a convenient route for rapid synthesis and easy tuning of Commission Internationale de l'Eclairage chromaticity coordinates to achieve white light emission. These findings might promote the large-scale synthesis of lead-free all-inorganic compounds for future applications in optoelectronic devices. Emitting wavelength of cesium copper halides can be effectively tuned by regulating the process of mechanochemical reaction firstly.