A review on photoluminescence phosphors for biomedical, temperature sensing, photovoltaic cell, anti-counterfeiting and white LED applications

The luminescent materials incorporated with rare earth (RE)/transition metal (TM) ions that possess up/down conversion phenomena have found widespread applications in sensing, optical thermometry, solar cells, biomedical fields and wLEDs. The augmented studies on such materials have been conducted to explore their luminescent properties for the aforementioned applications. However, how to precisely design appropriate luminescent material for certain application, how to evaluate adequacy of synthesized phosphor and finally to accomplish targeted irradiation for its desirable and practical utilization are urgently need to be clarified. In this article, a thorough overview is presented on recently explored phosphors doped with different RE/TM ions to acquire in depth knowledge about such materials and to answer the above-mentioned issues. Herein, desirable light quality for targeted application, frequently-used activators and quantitative verification methods such as cytotoxicity test and good contrast are respectively discussed for drug delivery and bio-imaging applications. The role of thermally and non-thermally coupled levels in phosphors to serve as an excellent material for thermal sensing application is reviewed. Various materials with up/down conversion are studied for improving solar cell efficiency. Different materials used for display devices and wLEDs are discussed to understand the need of developing novel materials for enhancing quantum efficiency of commercial white light emitting devices. Finally, remnant challenges in these four emerging fields are addressed, our perspectives for further investigations are presented with hope that this review can pave the way for future researchers to design and study phosphors for these application