Unlocking Full-Spectrum\nBrilliance: Dimensional Regulation\nin Lead-Free Metal Halides for Superior Photoluminescence

Lead-free\nmetal halides with tunable structures have emerged as\na new class of optoelectronic materials. The arrangement of metal\nhalide polyhedra defines their structural dimensionality and serves\nas a key factor influencing their optical properties. To investigate\nthis, we synthesized four different antimony (Sb)-doped indium (In)-based\nmetal halides, all of which possess zero-dimensional (0D) electronic\nstructures but exhibit 3D, 2D, 1D, and 0D structural dimensionality\nat the molecular level. With a decreasing of structural dimensionality,\ntheir self-trapped exciton (STE) emission shows a red shift with peak\nposition from 496 to 663 nm. We revealed that the red shift is caused\nby increased distortion of [SbCl<sub>6</sub>]<sup>3–</sup> octahedra\nas the structural dimensionality decreases, leading to lowered energy\nlevels of STE and a corresponding red shift. The tunable STE emission\nmakes these metal halides promising for anticounterfeiting and white\nLED applications. These findings provide a new strategy for tuning\nSTE emission in lead-free metal halides.