Synergistic impact of dual metal-oxide doping on the morphological and optoelectronic properties of flexible electrospun PVA nanofiber detectors

Abstract

This study presents the design, fabrication, and comprehensive characterization of UV–visible photodetectors based on electrospun ZnO–CoO/PVA composite nanofibers deposited on flexible polyethylene terephthalate (PET) substrates. Three compositions were prepared by systematically varying the metal-oxide loading: a pristine PVA baseline (M1), a low-loading composite (M2, 8:2), and a high-loading composite (M3, 6:4), enabling a direct correlation between stoichiometry and optoelectronic performance. The optimized M3 (6:4) sample exhibited extremely fine one-dimensional nanostructures with a fiber diameter as small as 22 nm. X-ray diffraction analysis revealed a predominantly amorphous phase within the polymeric matrix, while Energy Dispersive X-ray spectroscopy confirmed a highly homogeneous distribution of Zn, Co, and O throughout the nanofibrous network. Optical measurements demonstrated effective tuning of the bandgap structure with increasing metal-oxide content. Under periodic illumination at a fixed bias, the M3 configuration displayed a strong broadband photoresponse, achieving a maximum sensitivity of 1833.3% at 395 nm, corresponding to a three-order-of-magnitude increase in current relative to the M2 (8:2) configuration. Furthermore, the M3 device delivered fast temporal response, with a rise time of τ_r = 0.076 s and a fall time of τ_f = 0.074 s, together with a high specific detectivity of D* = 9.51 × 10⁸ Jones. Combining these figures of merit with its mechanical flexibility, non-toxic composition, and low-cost fabrication, the developed ZnO–CoO/PVA photodetector represents a promising candidate for flexible, broadband optoelectronic devices operating across the UV–visible spectral range.