A centimeter-sized water-resistant blue-light-emitting zero-dimensional hybrid halide for solid-state lighting

Zero-dimensional (0D) organic-inorganic hybrid halides exhibit attractive excitonic emission properties, but their environmental stability remains a major challenge. Here we report centimeter-sized single crystals of (MAPPA)CdBr₄·H₂O (MAPPA = protonated 1-methyl-4-(6-aminopyridin-3-yl)piperazine), which exhibit blue emission with a photoluminescence quantum yield of 46.7%. The emission is excitation-wavelength-independent, maintains an unchanged spectral profile under varying excitation powers and is governed by a temperature-driven balance between thermally activated blue emission and self-trapped exciton-mediated yellow emission. Time-resolved spectroscopy reveals moderate thermal quenching, while density functional theory calculations indicate that the emission originates from Br-4p → Cd-5s/Br-4p transitions. (MAPPA)CdBr₄·H₂O retains both luminescence and crystallographic integrity after extended exposure to water (50 days) and air (150 days), demonstrating notable environmental resilience. When integrated into a white light-emitting diode (WLED) with commercial phosphors, the material yields warm-white emission with a high color rendering index (91) and stable chromaticity across operating currents. These findings highlight (MAPPA)CdBr₄·H₂O as a robust 0D halide hybrid, offering valuable design insights for developing environmentally stable blue emitters for next-generation solid-state lighting.