Coaxial SnS₂/SnS Nanostructures on the Ag Fiber Substrate for Flexible Self-Powered Photodetectors

Sustainable and stable photodetectors with self-powering nature and superior performance are necessary to address the growing demand for flexible and wearable optoelectronic devices. This work demonstrates a flexible, self-powered, coaxial p–n heterojunction photodetector using SnS 2 /SnS on an Ag fiber substrate by coupling the photoexcitation property, semiconductor nature, and piezoelectric effect. Detailed characterization studies confirm the formation of hexagonal and orthorhombic crystal planes of SnS 2 and SnS nanoflakes, respectively, with a piezoelectric coefficient ( d 33 ) of 175 pm/V for SnS 2 . The photoabsorption is maximum in the visible region with a direct band gap of 2.1 eV. The electrical studies display a tunable photoresponse under zero-bias conditions. Upon compressive strain of 0.43%, the photoresponse increases by 36%. The I on / I off ratio of the fabricated photodetector was 10 2 at a zero bias, and the rise and decay times shorter than 1 s were obtained. The maximum external quantum efficiency of the fabricated photodetector was found to be 54.2%, owing to the superior piezo-phototronic properties. The band diagram and the charge transfer mechanism are studied to investigate the piezo-phototronic effect. The uniform strain on the Ag fiber substrate and the piezo-potential distribution upon compressive and tensile strain promotes carrier separation in the coaxial interfaces of the p–n junction. The demonstrated strategy provides a direction for developing fiber-based photodetectors with self-powering behavior and enhanced photoresponsivity for next-generation smart wearable textile-based applications.