Tunable-wavelength photoluminescence of a flexible transition metal doped oxide phosphor thin film

Near-infrared luminescence phosphors are key material basis to potential applications for light sources and optoelectronic devices. In particular, it is vital to tune the luminescent properties of these phosphors in a flexible and controllable manner. Here, we demonstrate that a flexural strain originated from bending can be used to modulate the photoluminescence of freestanding Ni²⁺ doped SrTiO₃ membranes. The bent membranes show remarkable red-shift emissions, arising from the variations of the symmetry of host materials and the local crystal fields around the Ni²⁺ ions. In addition, the phosphor films show a reversible and stable wavelength modulation with remarkable anti-fatigue characteristics after 10⁴ bending cycles. These results provide a potential routine to develop flexible strain-tunable devices for applications in optical amplifiers and other optoelectronics.