Ionic liquid-assisted route to nanocrystalline single-phase phosphors for white light-emitting diodes

Abstract

White light-emitting diodes represent the future generation of domestic and public lighting, substituting the currently favored (compact) fluorescent lamps. Research on improving the performance and costs leads to a focus on processing constraints. The optimization of the grain size is judged to be an important tool for minimizing the necessary amount of (expensive rare-earth containing) phosphors. Using only one type of phosphor that emits white light instead of a mixture of three phosphors (one for blue, green, and red, respectively) will significantly improve the characteristics of future light-emitting diodes. Small, 6-8nm-sized particles emit intense white light observable by the naked eye. The emission color has been studied by varying the dopant ion concentrations as well as the excitation wavelengths, yielding white light close to standard daylight. Lighting the path for the future: A single-phase phosphor doped with two optically active ions has been successfully downsized by using an ionic liquid mediated process. The usually occurring quenching of the emitting state when decreasing the particle size is omitted. Small, 6-8nm-sized particles emit an intense white light observable by the naked eye. The emission color has been studied by varying the dopant ion concentrations as well as the excitation wavelengths, yielding white light close to standard daylight. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.