Wide multicolor tunability of blue-to-green up-conversion emission and white light generation in Pr3+/Yb3+ co-doped yttrium tantalates

Abstract

We achieved wide multicolor tunable up-conversion emission and white light generation in Pr3+/Yb3+ co-doped yttrium tantalates prepared by a soft sol–gel method designed to afford the cubic Y3TaO7 and monoclinic M′-YTaO4 crystalline phases. The annealing temperature influenced the crystallization kinetics and stabilized a preferential phase. To investigate how the crystalline phase affected the Pr3+ photoluminescence properties, we recorded up-conversion emission spectra for the samples annealed at 900 or 1100 °C. Excitation at 980 nm elicited emissions assigned to the Pr3+ transitions in the blue (3P0→3H4), green (3P1,0→3H5), and red (3P0→3H6,3F2; 3P1→3F3) regions. The Yb3+ content, crystalline phase, and laser power influenced such emissions. The most dominant mechanisms are proposed to elucidate the differences in the number of photons during the power dependence studies. Spectroscopic studies showed that the crystalline structure composition and Yb3+ concentration affected the population of the Pr3+:3P1,0 states and modified the relative intensity of bands particularly in the green and red regions. These changes provided extensive color gamut, so we evaluated emission color tunability from blue to green as a function of the Yb3+ concentration. The above-mentioned structural and photoluminescent properties make these Pr3+/Yb3+ co-doped yttrium tantalates potential candidates for applications in Photonics, mainly in the integration of white, blue, or green LED systems, multicolor displays, and other devices for security applications.