Achieving High Photoluminescence Quantum Yield in Sb‐Doped Indium‐Based Hybrid Halides for Single‐Component Warm White LEDs

ABSTRACT Indium(III)‐based hybrid halides are emerging low‐dimensional luminescent materials; however, their rigid lattices and d ¹⁰ electronic configuration of In ³⁺ suppress intrinsic self‐trapped‐exciton (STE) emission, leading to limited photoluminescence quantum yield (PLQY). To address this issue, Sb ³⁺ is doped into the 0D (Me ₂ NH ₂ ) ₄ InCl ₇ host, transforming it from a nearly non‐emissive material into a highly efficient warm‐white STE emitter. The optimized (Me ₂ NH ₂ ) ₄ InCl ₇ :0.2Sb ³⁺ delivers a near‐unity PLQY (∼100%) under 350 nm excitation. Single‐crystal structural analysis and theoretical calculations reveal substitutional Sb ³⁺ at In ³⁺ sites, inducing locally distorted [SbCl ₆ ] octahedra. This Sb ³⁺ ‐triggered local lattice distortion strengthens electron–phonon coupling, and it deepens the STE potential well and suppresses non‐radiative relaxation pathways, thereby enabling robust broadband STE emission with a microsecond‐scale lifetime (4.28 µs), a large Stokes shift (280 nm), and a wide bandwidth (177 nm). This work provides a facile route to realize warm‐white emission from a single host lattice based on stable, low‐toxicity indium‐based hybrid halides.