Spectral variations of nano-sized Y3Al5O12:Ce phosphors via codoping/substitution and their white LED characteristics

The urgent demand for alternative light source in an illumination and display area has led to the rapid advancement of white light emitting diodes (LEDs). A blue LED can serve as a primary light component, pumping photoluminescence of a broad band emission phosphor such as yellow Y3Al5O12:Ce3+ (YAG:Ce). Various YAG:Ce nanocrystalline phosphors, where a red-emitting Pr3+ ion is codoped with Ce3+ ion in the YAG host and some Y3+ or Al3+ sites are substituted with Gd3+ or Ga3+ ions, respectively, have been synthesized via a novel soft chemistry using citric acid and poly (vinyl pyrrolidone) (PVP). Codoped Pr3+ ion exhibited its characteristic red line peaks, and the Ce3+ emission was blue- and red-shifted by respective Ga3+ and Gd3+ substitution due to a modified crystal field splitting. These spectral variations caused by a codopant and substituents can lead to the manipulation of CIE color coordinates of the emission. This tunability would contribute to an improved color gamut of white LEDs, particularly for backlighting liquid crystal display. White LEDs were fabricated by coating these nanophosphors on blue LEDs and characterized. (C) 2008 Elsevier B.V. All rights reserved.