Bright White Up-Conversion Emission from Ho3+/Yb3+/Tm3+ Tri-Doped Y2SiO5 Phosphors

Abstract

Ho3+/Yb3+/Tm3+ tri-doped Y2SiO5 phosphors were synthesized by the coprecipitation method. Bright white luminescence upon 980 nm near-infrared excitation can be observed for the sample at the optimum chemical composition of Y2SiO5: 5%Yb3+/0.4%Tm3+/0.1%Ho3+, and the measured white light consisting of blue, green, and red emissions can be fine-tuned in a wide range of pump power, which is intense and visible to the naked eye even with a pump power of 62 mw. Besides, the color coordinates and correlated color temperatures (CCTs) can also be adjusted between high and low, under different excitation pump powers, and the obtained optimal color coordinate (0.333, 0.319) is very close to the standard white light (0.333, 0.333) coordinate. Based on the dependence of the up-conversion emission intensity on the excitation power, we could confirm that energy transfer processes from Yb3+ to Tm3+ and Ho3+ ions took place simultaneously in the Ho3+/Yb3+/Tm3+ tri-doped Y2SiO5 phosphors, and produced red up-conversion emission, however, the blue and green emissions came from Tm3+ and Ho3+ ions, respectively. The white light may be a possible candidate for applications in the field of lighting, displays, and photonics.