Advances in Near-Infrared Luminescent Materials without Cr³⁺: Crystal Structure Design, Luminescence Properties, and Applications

Abstract

Near-infrared (NIR) luminescent materials are attracting much attention as the promising applications in food composition analysis, night vision, biosensors, and so on. Besides Cr3+ ions, other ions such as Eu2+, Ce3+, and Bi3+, etc. recently also exhibit remarkable broadband NIR light emission in inorganic hosts. The key issues are to optimize their photoluminescence quantum yield and reveal an unclear “structure-luminescence” relationship. Herein, photoluminescence properties of NIR luminescent materials without Cr3+ are systematically summarized. Importantly, we propose a significant influence of local crystal structure on NIR luminescence properties. These strategies contain (i) ligand covalency, (ii) strong crystal field and distorted lattice, (iii) selective sites occupation, and (iv) mixed valences and doping level control. The proposed “structure-luminescence” relationship can provide a new insight into exploit NIR luminescent materials and optimize current luminescent materials. Furthermore, the concept of “high-throughput DFT prediction-crystal structure design-photoluminescence performances optimization” is summarized to swiftly develop targeted NIR luminescent materials. Subsequently, energy transfer strategies and application prospects are summarized in detail. This review discusses the relationship between crystal structure and NIR light emission based on a high-throughput method. The proposed concept can offer a guidance to exploit a series of novel NIR luminescent materials and clarify underlying luminescence mechanisms.

Highly efficient Fe3+-doped A2BB′O6 (A = Sr2+, Ca2+; B, B′ = In3+, Sb5+, Sn4+) broadband near-infrared-emitting phosphors for spectroscopic analysis

“…Moreover, substantial progress has been achieved in the tunable NIR luminescence of Cr 3+ -doped phosphor materials 12 – 14 . However, there is a potential risk of oxidation of Cr 3+ to Cr 6+ 15 , 16 . On the one hand, mixed Cr 6+ seriously affects the NIR luminescence efficiency 17 .…”

“…Therefore, there is an urgent requirement to find alternatives to the Cr 3+ activator to achieve NIR emission. Recently, several studies have focused on Bi 3+ -, Eu 2+ -, and Mn 2+ -activated NIR-emitting phosphors 15 , 16 , 19 . Their emission wavelengths are near the deep-red light region, which has inferior penetration ability in biological tissues.…”

Achievement of high efficiency and thermally stable near-infrared phosphors by designing a chromium crystallographic environment for nondestructive testing and night vision

“…NIR luminescent materials have generated significant interest in the biomedical field, nondestructive food testing, night vision, and bioimaging technologies. [1][2][3][4][5][6][7][8][9][10][11][12] Compared to traditional NIR light sources such as halogen lamps and tungsten-halogen lamps, NIR pc-LEDs exhibit prominent advantages because of their low cost, high efficiency, and portability, which can be employed in a smart device. 5,[13][14][15][16] The Cr 3+ ions with a 3d 3 structure are the main protagonists of current NIR phosphor materials.…”

“…In particular, modulating the crystal field environment by substitution of single cations or chemical units is an effective way to improve the luminescence performance, such as Sr(Al 12Àx Ga x )O 19 :Cr 3+ , Gd 3 (Sc 2Àx Al x )Ga 3 O 12 :Cr 3+ , Ca 3 Hf 2 (Lu x Al 2Àx )SiO 12 :Cr 3+ , and (Li 1Àx In 2Àx Zn 2x )SbO 6 :Cr 3+ . 3,[22][23][24] An enhancement of the luminescence properties can be achieved fundamentally by tuning the environment of the crystallographic site occupied by Cr 3+ ions. However, currently, the research on the influence of the crystallographic sites occupied by Cr 3+ ions on the luminescence properties (FWHM, thermal stability, and IQE) is still not comprehensive and remains a valuable and promising study.…”

Tailoring red-NIR luminescence in rare earth doped lead-free layered double perovskites by bivalent manganese energy bridge

“…[5][6][7] As an emerging eld, researchers have made considerable efforts to explore new NIR emitters, such as Eu 2+ /Cr 3+ /Bi 3+ -doped NIR bulk luminescent materials, CH 3 NH 3 PbI 3 halide perovskite, Sb 3+ -doped Cs 2 ZnCl 4 metal halide materials and Ag 2 S quantum dots based LEDs. [8][9][10][11][12] In these both regard, the development of red and NIR luminescent materials provides new opportunities for both white and NIR pc-LED applications.…”