Fabrication and characterization of ZnWO4/CoWO4 heterojunction for multispectral photodetection on flexible substrate

Abstract

Flexible photodetectors hold significant interest across diverse applications, such as imaging, communication, healthcare, and environmental monitoring. This work reports a broad-band photodetector comprising Zinc tungstate (ZW) and Cobalt tungstate (CW) on a flexible paper substrate. CW thin film was fabricated by a facile successive ionic layer adsorption and reaction(SILAR) technique and the ZW nanoparticles, synthesised via simple co-precipitation method, were drop casted on it to form a heterojunction. Structural characterization of the materials was conducted using X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR), while scanning electron microscopy was employed for detailed morphology analysis. CW is a p type semiconductor with its bandgap of 2.6 eV, exhibits impressive sensitivity across both visible and infrared segments of the electromagnetic spectrum. In contrast, ZW which is n type contributes UV-responsive, attributes effectively broadening the overall spectral sensitivity from Ultraviolet (UV) to Infrared (IR) spectra within a single compact device. The photodetector demonstrates remarkable responsivity of 1.66 mA/W (UV), 24.58 mA/W (Visible), and 0.024 mA/W (IR) under respective light intensities of 0.6 mW/cm², 0.4 mW/cm², and 4.41 mW/cm. The detectivity metrics are equally impressive, measuring at 9.9×1010 Jones (UV), 5.01×1011 Jones (Visible), and 4.48×1010 Jones (IR). The successful combination of Zinc tungstate and Cobalt tungstate on a paper substrate represents an advancement in photodetector technology, offering enhanced sensitivity, extended spectral range, and the potential for seamless integration into wearable electronics and portable devices.