A Zero‐Dimensional Hybrid Copper(I) Halide with Near‐Unity PLQY for Highly Sensitive X‐Ray Scintillation and Efficient Warm White Light‐Emitting Diodes

ABSTRACT The development of novel hybrid metal halides exhibiting near‐unity photoluminescence quantum yield (PLQY) and responsiveness to visible light excitation are pivotal for X‐ray imaging technologies and advancing solid‐state lighting. Herein, we report a novel zero‐dimensional hybrid copper(I) halide, (ATPP) 2 Cu 2 I 4 (ATPP = acetonyltriphenylphosphonium), and its structure features edge‐sharing [Cu 2 I 4 ] 2 − dimers. It displays bright broadband orange emission with a large Stokes shift of 304 nm and achieves a PLQY of 96.43%. The near‐unity PLQY and weak self‐absorption enable it exceptional X‐ray scintillation performance with a light yield of 20 440 photons/MeV and a low detection limit of 47.06 nGy air s − 1 . In addition, a warm white light‐emitting diode (WLED) was obtained by integrating (ATPP) 2 Cu 2 I 4 as an orange phosphor onto a 365 nm UV LED chip, exhibiting a high color rendering index of 93 and a correlated color temperature of 3397 K. This work not only presents an outstanding candidate material for X‐ray scintillator and warm WLED but also underscores the importance of low‐dimensional hybrid copper(I) halides as versatile luminescent materials for multifunctional optoelectronic applications.