Near-infrared (NIR) luminescent materials have attracted great attention in biomedical fields, non-destructive analysis, and night-vision technologies. Compared to traditional NIR light sources such as halogen lamps and tungsten-halogen lamps, NIR-emitting phosphor-converted light-emitting diodes (pc-LEDs) exhibit significant advantages of low cost, high efficiency, and portability, which can be employed in everyday smart devices. The development of broadband NIR-emitting phosphors with high luminescent efficiency and appropriate wavelengths is extremely important. Cr3+ ion-activated near-infrared phosphors have been widely reported, typically producing broadband emission in the range of 650 to 1300 nm. However, achieving ultra-broadband and tunable near-infrared emission of Cr3+ remains challenging. Recently, Prof. Guogang Li’s group and Prof. Jun Lin’s group have realized the photoluminescence (PL) tuning of LiIn2SbO6:Cr3+ by chemical unit cosubstitution of [Zn2+–Zn2+] for [Li+–In3+]. A series of (LiIn)1-yZn2yInSbO6:Cr3+(y≤0.08) solid solution phosphors have been constructed, which exhibit both ultra-broadband NIR emission and tunable PL properties of Cr3+.
Figure 1. PL tuning and applications of (LiIn)1-yZn2yInSbO6:Cr3+.
The study shows that the (LiIn)1-yZn2yInSbO6:Cr3+(y≤0.08) solid solution phases are successfully synthesized. The introduction of Zn2+ leads to lattice shrinkage, which influences the coordination environment around Cr3+, thus laying foundation of PL tuning of Cr3+. Under 460 nm excitation, LiIn2SbO6:Cr3+ shows an ultrabroad NIR emission peak at 965 nm, with a large full width at half maximum (FWHM) of 217 nm. Tunable emission over a wide range from 965 to 892 nm is achieved by cosubstitution of [Zn2+–Zn2+] for [Li+–In3+]. In this process, the PL intensity is increased by 2.24 times, and the FWHM can reach 235 nm. The time-resolved PL spectra reveals that there is only one luminescent center. Based on theanalysis of crystallographic site occupation and coordination environment, the blue-shift mechanism of emission spectra is revealed combined with the Tanabe–Sugano diagram. The lattice contraction induced by Zn2+ incorporation leads to a stronger crystal field around Cr3+, which upshifts its 4T2g energy level, and thereby induces a blue shift in the PL spectra. Finally, the as-synthesized (LiIn)1-yZn2yInSbO6:Cr3+ phosphors have demonstrated application potential in night-vision and NIR spectroscopy techniques.
This work was recently published in theAngewandte Chemie International Edition (titled “Simultaneous Broadening and Enhancement of Cr3+ Photoluminescence in LiIn2SbO6 by Chemical Unit Cosubstitution: Night-Vision and Near-Infrared Spectroscopy Detection Applications”, DOI: 10.1002/anie.202103612). The first author is Dr. Dongjie Liu and the corresponding authors are Professors Guogang Li and Jun Lin. This work was financially supported by the Science and Technology Cooperation Project between Chinese and Australian Governments, and the National Natural Science Foundation of China.
Original link for the paper: https://onlinelibrary.wiley.com/doi/10.1002/anie.202103612
