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.