Hybrid Indium Halides With Near‐Unity Quantum Yield for Multimodal Stimuli‐Responsive Luminescence and High‐Performance White LEDs

ABSTRACT Low‐dimensional indium‐based metal halide materials have emerged as promising optoelectronic materials owing to their outstanding photophysical properties. However, the low photoluminescence quantum yield (PLQY) caused by forbidden transitions has limited their further application in optoelectronic devices. Here, a novel orange‐yellow emitting (C 25 H 21 ClP) 2 InCl 5 :Sb 3+ 0D hybrid metal halide single crystal was successfully designed and synthesized, with a PLQY approaching 100%. This near‐unity efficiency stems from Sb 3+ ‐induced band structure engineering, which effectively suppresses non‐radiative recombination pathways while enhancing radiative decay. The efficient broadband orange‐yellow emission originates from self‐trapped excitons (STEs) induced by strong electron‐phonon coupling, accompanied by unique low‐temperature anti‐thermal quenching behavior. This sample exhibits highly efficient luminescence responses under various external stimuli, with its mechanoluminescence (ML) performance being particularly outstanding. It is the first reported indium‐based metal halide with significant mechanical luminescence properties. The above‐mentioned multi‐modal stimulus response characteristics endow (C 25 H 21 ClP) 2 InCl 5 :Sb 3+ with significant potential in advanced application fields such as pressure‐sensitive sensing, security anti‐counterfeiting, and white light‐emitting diodes (WLEDs) applications.