Ultrafast Microwave-Assisted Fabrication of Copper-Doped Zinc Halide Nanocrystals Unifying Efficiency and Stability

Balancing synthesis efficiency, luminescence performance, and environmental stability in lead-free metal halides remains challenging. Here we report the first synthesis of Cu⁺-doped Cs₂ZnCl₄ nanocrystals via a rapid microwave-assisted solvothermal method. Structural analyses confirm that Cu⁺ ions occupy Zn²⁺ sites within orthorhombic [ZnCl₄]^2- frameworks, forming Cu⁺-related self-trapped exciton centers. Under optimized microwave conditions, nanocrystals with an average size of ∼19 nm are obtained, exhibiting cyan emission at 480 nm with a quantum yield of 35.25% and a lifetime of 30.97 μs, attributed to self-trapped excitons. Compared to conventional hot-injection techniques, this approach yields improved morphological uniformity (18.75 ± 0.1 nm) and enhanced photostability, maintaining 70% of initial emission intensity after 50 min of UV irradiation. The multiligand passivation strategy implemented during microwave synthesis effectively inhibits Cu⁺ oxidation and structural degradation. This work establishes a rapid and scalable synthesis route for high-performance lead-free phosphors, offering a practical pathway toward achieving both superior performance and stability in such materials.