An Overview for Zero-Dimensional Broadband Emissive Metal-Halide Single Crystals

The high-profile candidacy of low-dimensional metal-halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low-dimensional metal-halide single crystals, zero-dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron-phonon coupling have been further translated into near-unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal-halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications.