Transition metal ion activated near-infrared luminescent materials

Near infrared (NIR) luminescent materials are an exciting playground for telecommunications, biosciences and solar energy conversion. In particular, transition metal (TM) ions activated materials, which exhibit unique spectroscopic features such as broadband luminescence and long lasting phosphorescence in the NIR region, have attracted increasing attention. The local chemistry environment enables TM ions activated to have compelling properties such as tunable, broadband NIR emission as well as the adjustable decay dynamics. In this review, we firstly introduce the fundamental principles, the crystal field theory, for the NIR optical response of the TM ions, discuss the key physical factors to adjust the NIR luminescence properties of the TM ions. Secondly, we present a comprehensive review of the strategies based on local chemistry engineering for design the TM ions activated materials with the desired performance. Furthermore, we also emphasize recent advances in the application of the TM ions activated materials. Finally, we comment on the future requirements for the TM ions activated materials.