The search for efficient phosphors for color conversion for white light emitting LEDs (w-LEDs) has recently raised new interest in the photoluminescence behavior of phosphors materials doped mainly with rare earth ions. Another very recent research topic is than undoubtedly the development of new solid-state phosphors, which are suitable for the construction of tunable white light sources (so-called circadian sources) based on LEDs. It is a complete optical characterization, verification of thermal stability and usability in real conditions. Materials studied are, for example, ternary sulfides of the general formula ALnS2 (where A = Li, Na, K, Rb, Cs or their combinations, Ln = La, Gd, Lu, Y or their combinations) doped with Eu2+ ions, non-stoichiometric ceramics based on YAG:Ce further co-doped by other rare-earth ions to increase energy transfer, or high-entropy oxides like (Lu;Gd)3(Al;Sc)5O12 doped by Ce3+ ions.
