Mechanically induced enhancement and modulation of upconversion photoluminescence by bending lanthanide-doped perovskite oxides

We report experimental studies of the bending strain impact on the upconversion processes in Yb³⁺, Er³⁺, and Mn²⁺ co-doped BaTiO₃ (BTO) thin films with mica as the flexible substrate. Bending strain induces strong enhancement and modulation of the upconversion emission in doped BTO thin films. Because the unshielded 3d⁵ configuration of Mn²⁺ is more susceptible to crystal field changes, the introduction of an Mn²⁺ ion further promotes the strain-induced modulation effect. The upconversion intensity is amplified by six times at bending strain ε = 1.83% in BTO:Yb³⁺/Er³⁺/Mn²⁺ thin films. These results demonstrate the opportunity of rendering an upconversion emission through integrating lanthanide-doped ferroelectric films with flexible mica, especially by incorporating an Mn²⁺ ion.