Mechanically controlled reversible photoluminescence response in all-inorganic flexible transparent ferroelectric/mica heterostructures

The ability to reversibly control the luminescent properties of functional materials with diverse external stimuli, such as an electric field, strain, and temperature, is crucial for designing high-performance optical devices. Here, we demonstrate that a purely mechanical strain in a flexible mica substrate triggered by bending can be used to dramatically modify the photoluminescence response of a Pr-doped Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ epitaxial thin film in a stable and repeatable manner with a large gauge factor of up to 6853. The strong dependence of the photoluminescence performance on the mechanical bending arises from strain-induced variations in the lattice symmetry of the host film and the local crystal field around the Pr³⁺. In particular, because of the nature of mica, the film structure exhibits excellent antifatigue characteristics after 10⁴ bending cycles as well as high optical transparency in the range of 450–780 nm. This study provides a viable route for exploring the correlation between structural symmetry and photoluminescence in ferroelectric thin-film systems and offers new possibilities for developing all-inorganic, reconfigurable, transparent and flexible light sources, photodetectors, and wearable sensors.