Effect of Pr3+concentration in luminescence properties & upconversion mechanism of triple doped NaYF4: Yb3+, Er3+, Pr3.

Lanthanide-doped fluoride nanocrystals (NCs) exhibit excellent optical features, including upconversion and downconversion luminescence (UCL and DCL), that can be utilized in a variety of applications. In this study, we have successfully demonstrated the photoluminescence behavior of triple-doped NaYF₄: Yb³⁺, Er³⁺, Pr³⁺NCs in the Vis-NIR region. Herein, highly monodisperse hexagonal phase NaYF₄: Yb_0.2, Er_0.02, Pr_xnanocrystals in various Pr³⁺(x = 0, 0.1, 0.5, and 1 mol %) concentration with ∼22 nm diameter synthesized by thermal decomposition technique. The photoluminescence studies for all samples were performed under 980 nm laser excitation. The luminescence intensity of Er³⁺including blue (407 nm), green (520 and 540 nm), red (654 nm), and near-infrared (845 nm and 1530 nm) emissions was significantly quenched and Pr³⁺emission intensity at 1290 nm (Pr³⁺:¹G₄→³H₅) changes irregularly upon doping with Pr³⁺ions. Furthermore, we performed the excitation power dependence and decay time analysis to investigate the energy transfer and upconversion mechanisms of samples. These findings indicate that the presence of praseodymium strongly reduces emission intensities due to abundant cross-relaxation channels. In addition, particle size is an efficient factor, shedding light on the influence of Pr³⁺on the energy transfer and upconversion mechanisms of the fluorides.