Ultrasonically-prepared copper-doped cesium halide nanocrystals with bright and stable emission

All-inorganic cesium lead halide perovskite nanocrystals (NCs) are quite promising materials for emission-based applications. However, the intrinsic toxicity of lead, as well as the weak stability, remains to be resolved. Exploring more and more types of lead-free NCs with high photoluminescence quantum yields (PLQYs) and high stability is a fundamental task. This work gave the first example of copper doped cesium halide (Cu:CsX, X = Br, Cl/Br, Br/I) NCs with good stability and high PLQYs (∼31.2%), which could act as a new member of the lead-free NC family. A simple single-step ultrasonic method was applied for the synthesis of environmentally friendly Cu:CsX NCs. By varying the halide composition, the emission wavelength of Cu:CsX can be shifted within 450-505 nm. The as-prepared NCs show highly uniform size and excellent stability. Finally, UV pumped light-emitting diodes are demonstrated by using Cu:CsX NCs as a color conversion layer.