Strategies to Broaden the Emission Spectra of Cr3+-doped Near Infrared Emitting Phosphors

Abstract

The Cr3+ activated near-infrared (NIR) phosphors displayed much application potential in food detection and biological fluids or tissues component analysis due to the large spectrum overlap between emission of Cr3+ and the absorption of water and organic groups. To realize the real-time, convenient and multi-component inspection, the wideband NIR phosphor with large bandwidth (FWHM > 200 nm) is urgently demanded to cover the absorption band of the detected component as much as possible. This review simply retrospected the researches of the existing Cr3+ doped wideband phosphors and summarized the strategies to broaden the bandwidth of Cr3+, which mainly involved the strategy of the crystal field regulation, lattice site engineering, Cr3+-Cr3+ pairs, Cr3+/Cr4+ double fluorescence centers, energy transfer process and the new emission centers resulting from lattice distortion caused by Cr3+ doping. Meanwhile, the Cr3+emission feature was also discussed through the Tanabe–Sugano energy level diagram and configuration coordinate model. In addition, the existing problems and outlook of Cr3+ activated wideband emission phosphors were also proposed and prospected in present review, which provide a reference to broaden the bandwidth of Cr3+ for the developing efficient and stable wideband near-infrared phosphor.