Efficient Near-Infrared Luminescence in Lanthanide-Doped Vacancy-Ordered Double Perovskite Cs 2 ZrCl 6 Phosphors via Te 4+ Sensitization.

All-inorganic lead-free perovskite-derivative metal halides have shown great promise in optoelectronics, however, it remains challenging to realize efficient near-infrared (NIR) luminescence in these materials. Herein, we report a novel strategy based on Te 4+ /Ln 3+ (Ln=Er, Nd, and Yb) co-doping to achieve efficient NIR luminescence in vacancy-ordered double perovskite Cs 2 ZrCl 6 phosphors, which are excitable by a low-cost near-ultraviolet light-emitting diode (LED) chip. Through sensitization by the spin-orbital allowed 1 S 0 → 3 P 1 transition of Te 4+ , intense and multi-wavelength NIR luminescence originating from the 4f→4f transitions of Er 3+ , Nd 3+ , and Yb 3+ was acquired, with a quantum yield of 6.1 % for the Er 3+ emission. These findings provide a general approach to achieve efficient NIR emission in lead-free metal halides through ns 2 -metal and lanthanide ion co-doping, thereby opening up a new avenue for exploring NIR-emitting perovskite derivatives towards versatile applications such as NIR-LEDs and bioimaging.