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

ABSTRACT 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 3+ ‐doped 0D perovskite single crystals, (BYA) 4 InCl 7 : xSb 3+ . Structural analysis confirms the successful substitution of Sb 3+ into the isolated [InCl 6 ] 3− octahedra, which are spatially separated by bulky BYA + organic cations, thereby preserving the intrinsic 0D framework. Sb 3+ 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) 4 InCl 7 : Sb 3+ phosphor exhibits excellent color rendition (CRI = 89.3) and robust operational stability. This study elucidates the structure property interplay governing Sb 3+ ‐doped 0D indium halides and highlights their promise as high‐performance emitters for advanced optoelectronic devices.