Tuning the Photoresponse of Flexible and Wearable SnO2-Based UV Sensors Using the Piezo-Phototronic Effect

Piezo-phototronic devices based on wide bandgap oxide materials are extremely useful for wearable optoelectronic devices, as their optical and electrical characteristics can be easily tuned by external strain. Herein, we fabricated a flexible ultraviolet (UV) photodetector (PD) by depositing a thin film of SnO₂ nanoparticles onto a poly(ethylene terephthalate) (PET) substrate using a simple chemical coating method. The SnO₂ film demonstrated strong UV absorption at around 335 nm and good transparency (∼80%) in the visible region (400–800 nm). The PD device exhibited excellent strain-induced photoresponse modulation in the UV region (275 nm) with photo-to-dark current ratio of up to ∼1.01 × 10⁴ and a responsivity of 0.745 A/W at 1 V under a tensile strain of 9%. The device exhibited an excellent reversible and reproducible photoresponse following the number of bending operations (∼10³ times). The device’s response time remained unaffected by the applied external strain, ensuring its reliability for multiple operations. The observed modulation in the photoresponse is attributed to strain-induced modifications in the Schottky barrier height (−15 to 60 meV) at the Au/SnO₂ interface, which affected the width of the depletion region and enhanced charge carrier collection efficiency at the electrodes. The realization of strain-induced enhancement in the performance of UV photodetectors based on metal oxide optoelectronic devices through the piezo-phototronic effect is the primary objective of this work, paving the way for next-generation wearable oxide-based optoelectronics.