Near-Infrared Luminescence in Mo 4+ -Activated Metal Halide for Advanced Optoelectronics

The development of efficient, thermally stable, and broadband near-infrared (NIR) phosphors is critical for next-generation smart devices yet remains challenged by limited quantum efficiency and spectral coverage in existing systems. Here, we introduce a breakthrough strategy via crystal field distortion engineering in zero-dimensional Cs₂ZnCl₄, achieving unprecedented Mo⁴⁺-activated broadband NIR emission centered at 960 nm with a fwhm ∼ 206 nm. Unlike conventional octahedral hosts, the tetrahedral Zn²⁺ site in Cs₂ZnCl₄ undergoes a distortion-driven transformation to an octahedral Mo⁴⁺ coordination upon doping, facilitated by Cs vacancies and Jahn-Teller effects. This unique structural reorganization enables a remarkable internal quantum efficiency of 78.7%. The material exhibits thermal stability and environmental robustness. Leveraging these properties, we fabricate NIR phosphor-converted LEDs (pc-LEDs) with a peak output power of 132 mW at 350 mA, demonstrating high-contrast imaging for fruit bruise detection and night vision. This work not only establishes a new paradigm for activator-centered lattice distortion to unlock efficient NIR luminescence but also expands the frontiers of 4d transition-metal-ion applications in optoelectronics.