Blue luminescence of Cs2CuCl4 glass ceramics with long-term water-resistance stability

Metal halide Cs 2 CuCl 4 has shown great potential in photovoltaic and photoelectric applications, but it is sensitive to oxygen, moisture, light and temperature. To improve its stability, we make Cs 2 CuCl 4 nanocrystals precipitated from borosilicate glass synthesized by traditional melting and quenching method. The prepared glass ceramics have an absorption band at 374 nm and an intense blue emission band at 465 nm, showing long-term water-resistance stability after immersing this sample in water for 80 days. Density functional theory (DFT) calculations show that the strong band observed in the excitation spectra can be attributed to a ligand-to-metal charge transfer (LMCT) transition. Theoretical calculation and spectral studies showed Cs 2 CuCl 4 nanocrystals absorbed the excitation ultraviolet by LMCT and then transfer the energy to Cu + , so the blue emission originated from transition 3d 9 4p 1 → 3d 10 of Cu + defects in Cs 2 CuCl 4 nanocrystals. Our work not only demonstrates Cs 2 CuCl 4 glass-ceramics as a promising sky-blue phosphor, but also presents a new general method to improve the stability of lead-free metal halides, paving the way to their applications.