Phosphor-up-converted white LED materials assisted by 1-D photonic crystals

Abstract

A series of lanthanide-doped aluminosilicate glasses have been prepared by sol-gel (SG) processing. The present work started by optimizing bulk aluminosilicate glasses doped with Er3+, Tm3+ and Yb3+ for white light generation (WLG) and possible application as white LED materials, using SG as a low-cost high purity processing alternative to conventional phosphor fabrication. Undoped alternating aluminosilicate glass and titania multilayers were also synthesized in the form of Bragg mirrors (BMs) and Fabry-Perot Microcavity (MC) 1-D photonic crystals to assist light emission, e.g. by enhancing it at selected wavelengths within the WLG spectrum. This work utilizes (anti-Stokes) up-conversion (UC) excited at 980 nm to generate white light, instead of conventional (Stokes) down-conversion. The materials prepared were characterized by X-ray diffraction (XRD), Spectroscopic Ellipsometry, FTIR, variable angle specular reflection and UC photoluminescence (UCPL) spectroscopies. The UC light emission was analyzed with the help of CIE chromaticity diagrams. Laser power dependence studies were also performed in order to assess the average number of infrared photons (980 nm) involved in the UC mechanism.