Near-Unity PLQY and Strong Broadband Emission From 0D (BYA)(4)InCl(7) Enabling High-CRI Solid-State Lighting.

0D metal halides are promising light emitters owing to strong quantum confinement and efficient self-trapped exciton (STE) emission, yet achieving both broadband tunability and near-unity PLQY in lead-free systems remains challenging. This study reports the synthesis and comprehensive characterization of Sb-doped 0D perovskite single crystals, (BYA)InCl: xSb. Structural analysis confirms the successful substitution of Sb into the isolated [InCl] octahedra, which are spatially separated by bulky BYA organic cations, thereby preserving the intrinsic 0D framework. Sb incorporation induces a substantial bandgap narrowing from 4.08 to 2.85 eV, accompanied by a pronounced enhancement of broadband STE emission. At an optimal doping level x = 4.87%, the material achieves an ultrahigh PLQY of 97.53%. Temperature-dependent photoluminescence measurements, together with density functional theory calculations, reveal that the exceptional emission efficiency arises from strong electron phonon coupling and a low activation energy for thermal quenching. Furthermore, a prototype white light-emitting diode fabricated using the (BYA)InCl: Sb phosphor exhibits excellent color rendition CRI = 89.3 and robust operational stability. This study elucidates the structure property interplay governing Sb-doped 0D indium halides and highlights their promise as high-performance emitters for advanced optoelectronic devices.