Efficient near‐infrared emission in lanthanum ion doped double perovskite Cs2NaScCl6 via Cr3+ sensitization under visible light excitation

Abstract Herein, we synthesized Cr3+/Ln3+ (Er3+, Tm3+)‐codoped rare earth‐based Cs2NaScCl6 double perovskite, and the near‐infrared emission of Ln3+ can be excited by visible light through the energy transfer (ET) from Cr3+ to Ln3+. Moreover, there are two independent emission bands, which stems from 4T2 → 4A2 transition of Cr3+ (970 nm) and f‐f transition of Ln3+ (1542 nm for Er3+ and 1220 nm for Tm3+), respectively. Particularly, both compounds have ultra‐high photoluminescence quantum yield (PLQY) of 60% for 10%Cr3+/6%Er3+‐codoped Cs2NaScCl6 (Er3+ emission: ∼26%) and 68% for 10%Cr3+/4.5%Tm3+‐codoped Cs2NaScCl6 (Tm3+ emission: ∼56%), which can be attributed to the ultra‐high ET efficiency from Cr3+ to Ln3+ and the similar ionic activity of Sc3+ and Ln3+ allowing more dopants enter the host lattice. Considering the excellent stability of the samples, we demonstrated Cr3+/Tm3+‐codoped Cs2NaScCl6 in the applications of near‐infrared imaging and night vision. Finally, we reported 10%Cr3+/4.5%Tm3+/9%Er3+‐tridoped Cs2NaScCl6 and further applied it for optical thermometry. image