In-situ tailoring upconversion processes from lanthanide ions doped ferroelectric films through piezoelectric strain

The ability to manipulate the upconversion processes in lanthanide doped phosphors is of great significance for both scientific research and practical applications. In this regards, we have demonstrated in-situ tailoring the upconversion processes in Yb3+, Er3+ and Tm3+ tri-doped BaTiO3 thin films through piezoelectric strain. In contrast to conventional chemical routes, the physical approach can eliminate the persisted sample-to-sample inherent inhomogeneities, and identify the lattice deformation impact on the intra-configurational 4f transitions of dopant ions, as well as inter-lanthanide ions energy transfers. Herein, the reduced photoluminescence intensities and the elongated lifetimes for the multi-color emissions mainly arise from strain-induced improved lattice symmetry, which contributes to the reduction of radiative probabilities of dopant Er3+ and Tm3+ ions. While the reduced distances between the dopant ions enhance the energy transfer. These two mechanisms are entangled and act simultaneously. The observed phenomena indicate that the influence of the variation of crystal-field effect on the upconversion emissions suppresses that of the interionic distance-dependent energy transfer under 0.2% biaxial strain imposed by PMN-PT substrates. Our work has unambiguously provided new opportunities to render the upconversion processes. More intriguingly, integrating lanthanide-doped ferroelectric films with giant piezoelectric actuators provide an in-situ and dynamic modulation of the upconversion emissions.