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

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.