Enhancing the NIR Emission in Cs2ScCl5·H2O:Cr3+ Phosphor via Te4+ Sensitization

Presently, a multitude of all-inorganic and lead-free metal halide perovskites are chosen as matrices for Cr3+ doping due to their favorable coordination environments, aiming to achieve a near-infrared (NIR) emission. Nonetheless, the acquisition of a more efficient NIR emission remains challenging. Herein, we successfully enhanced NIR luminescence within the Cs2ScCl5·H2O:Cr3+ by codoping Te4+ ions. The weak symmetry of Cs2ScCl5·H2O provides an appropriate crystal environment for the broadband near-infrared emission of Cr3+. The NIR emission from the 4T2 → 4A2 transition of Cr3+ is significantly enhanced due to the energy transfer by the emission of STEs, with a photoluminescence quantum yield (PLQY) of 11.02%. Compared to single doping with Cr3+, the emission intensity of Cs2ScCl5·H2O:Cr3+, Te4+ in the NIR region obtains a 3-fold enhancement, while a new yellow emission is simultaneously obtained. This discovery offers a viable method for achieving efficient NIR emission in lead-free metal halides via codoping with ns2 ions and Cr3+. Additionally, Cs2ScCl5·H2O:Cr3+, Te4+ sample was combined with a 380 nm violet light chip for encapsulation, demonstrating its potential applications in the fields of nondestructive material testing and night vision.