Efficient Near‐Infrared Luminescence with Broad‐Band Sensitization in Mo 4+ −Er 3+ Co‐Doped Cs 2 ZrCl 6 Vacancy‐Ordered Double Perovskites

Abstract Lanthanide (Ln 3+ )‐doped lead‐free inorganic metal halide perovskites with near‐infrared (NIR) luminescence have shown great promise in optoelectronics. However, these materials exhibit low NIR efficiency due to insufficient absorption from forbidden f − f transitions. Herein, a strategy based on Mo 4+ –Er 3+ co‐doping is reported to achieve efficient NIR emission in Cs 2 ZrCl 6 phosphors, which are excitable by low‐cost multicolor light‐emitting diode (LED) chips. Besides a broadband NIR emission of transition of Mo 4+ ions centered at 960 nm, the co‐doped sample also exhibits an NIR‐II emission peak at 1543 nm. These Mo 4+ − Er 3+ codoped samples achieved an overall photoluminescence quantum yield of 66.7%, with Er 3+ emission contributing 8.3%. Mo 4+ ions not only sensitize Er 3+ ions but also possess broad‐band excitation extending from ultraviolet to NIR region (250–850 nm). Further, temperature‐dependent (10–400 K) steady state and time‐resolved photoluminescence provide mechanistic information on excitation, emission, and sensitization mechanisms. These findings provide a general approach to achieve efficient NIR emission by codoping of optically active metal cations. The admirable stability and dual NIR bands of Mo 4+ –Er 3+ co‐doped Cs 2 ZrCl 6 microcrystals will open new avenues for NIR light sources excitable by low‐cost multicolor LED chips in potential optical communication, night‐vision, and bio‐imaging applications.