Mo ⁴⁺ ‐Doped Cs ₄ ZnBi ₂ Cl ₁₂ Lead‐Free Double Perovskite for Near‐Infrared Luminescence

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This study presents the synthesis of Mo 4+ ‐doped Cs 4 ZnBi 2 Cl 12 double perovskite through a hydrothermal method, demonstrating efficient near‐infrared (NIR) emission at 1110 nm with a full width at half maximum (FWHM) of 45 nm. The emission originates from the d‐d transition of Mo 4+ ions within an octahedral crystal field. Structural analysis using powder X‐ray diffraction (PXRD) confirms the phase purity and lattice contraction as a result of Mo 4+ substitution at Bi 3+ sites, supported by X‐ray photoelectron spectroscopy (XPS) and elemental mapping. The material exhibits broad excitation compatibility (348–590 nm) and achieves a photoluminescence quantum yield (PLQY) of 45.3% with a microsecond‐scale lifetime of 6.78 μs. Thermal stability tests demonstrate sustained emission intensity (58% at 420 K) and resilience to prolonged heating or UV exposure. This work highlights Mo 4+ ‐doped Cs 4 ZnBi 2 Cl 12 as a stable and efficient NIR emitter, advancing lead‐free perovskites for optoelectronic applications in bioimaging, agriculture, and sensing.