Frequency upconversion in Er3+ doped Y2O3 nanophosphor: Yb3+ sensitization and tailoring effect of Li+ ion

Er3+ doped Y2O3 nanophosphor has been synthesized using solution combustion technique and further characterized for structure and optical properties. Optical properties of Er3+ ion have been studied both through frequency upconversion (UC) as well as through fluorescence (excitation, emission, and CIE coordinate analysis) processes. Further to enhance the UC emission of Er3+ ions, a two step process has been used. In the first step, Yb3+ ion has been co-doped, which acts as the sensitizer for Er3+ through energy transfer process. In the second step, different concentrations of Li+ ions have been co-doped in the Er3+/Yb3+:Y2O3 system. Fourier transform infrared analysis, and X-ray diffraction (XRD) followed by Le-Bail refinement of the XRD data reveal that the co-doping of Li+ ion decreases unit cell parameter, increases the particle size, and removes the quenching centers (like OH, NOx, etc.), which all together causes a significant enhancement in UC emission. Optimum UC luminescence is attained for 5 mol% Li+ doping concentration beyond which a quenching in UC emission is observed. This combined approach, i.e. Yb3+ sensitization and Li+ ion tailoring simultaneously enhances the UC emission intensity of Er3+ several times in yttria matrix effectively. The strategy can be generalized in other hosts also which could help in the development of efficient photonic materials for lighting and display devices. (C) 2013 Elsevier Ltd. All rights reserved.