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

Efficient Near-Infrared Luminescence with Near-Unity Photoluminescence Quantum Yield in Erbium-Doped Double Perovskites Cs2NaYCl6 under Green Light Excitation

“…For example, Ln 3+ -activated NIR emitters have the sharp-peak NIR emission band, which will result in more concentrated energy and better energy resolution. Moreover, Ln 3+ -activated NIR emitters also have longer emission wavelengths, such as 1540 nm for Er 3+ and 1800 nm for Tm 3+ , , which will bring deeper tissue penetration and reduce autofluorescence interferences, allowing for higher imaging contrasts. Combined with the advantage of sharp-peak NIR emission and long decay lifetime, it can be further used in the lifetime imaging, fluorescence imaging, and NIR-II region fluorescence probe. − Based on the existing conditions in our laboratory, we have preliminarily demonstrated the application of Ln 3+ -doped Cs 2 NaYCl 6 in night vision and nondestructive testing.…”

“…As is well known, Er 3+ ions have rich energy levels, and their spectral ranges can cover from the visible region to NIR-I region and NIR-II region. Moreover, Er 3+ -activated luminescent materials also have the distinct upconversion PL characteristics, which has great potential for applications in fluorescence probe imaging, anticounterfeiting, temperature sensors, and other fields. − More importantly, the emission band of Er 3+ centered at 1540 nm is suitable for low-loss optical communications . Therefore, we here reported Er 3+ -doped rare-earth-based DPs of Cs 2 NaYCl 6 .…”