Valence‐State Engineering of Mo Ions in Zero‐Dimensional Cs ₂ SnCl ₆ Perovskite for Tunable Luminescence

Abstract Recently, Mo‐based and Mo‐doped near‐infrared (NIR)emitting perovskites have faced significant controversy regarding the oxidation state of Mo, chemical composition, and luminescence mechanism. The uncontrollable oxidation state of Mo ions during synthesis has severely limited the tunability of emission performance. Here, a novel strategy is demonstrated to modulate the oxidation states of Mo (Mo ⁴⁺ /Mo ⁵⁺ /Mo ⁶⁺ ) in zero‐dimensional (0D) Cs ₂ SnCl ₆ perovskite by controlling the SnCl ₂ /SnCl ₄ precursor. The resulting doped materials exhibit diverse and tunable emission properties. Specifically, the Mo ⁵⁺ ‐Mo ⁶⁺ co‐doped Cs ₂ Sn(O _x Cl _6‐x ) shows bright emission in the 450–750 nm and 800–1200 nm ranges with a high internal quantum efficiency (IQE) up to 58.4%, whereas the Mo ⁴⁺ ‐doped Cs ₂ SnCl ₆ exhibits dual NIR emission bands at 700–800 nm and 1200–1600 nm. Moreover, by incorporating multiple Mo valence states into a single matrix via post‐annealing or mixed precursors, an ultra‐broadband NIR phosphor is successfully produced covering 700 to 1600 nm with a large full‐width at half‐maximum (FWHM) of ≈520 nm. These novel phosphors demonstrate excellent stability, making them promising for applications in night vision and information encryption. The findings offer new insights into valence‐state‐controlled luminescence in halide perovskites and open pathways for designing high‐performance ultra‐broadband NIR emitters for advanced optoelectronic applications.