Investigation of UV-Vis Photoresponse of WO3/RGO Heterostructure-Based Optical Sensor

Abstract

Combining tungsten oxide (WO3) with feasible reduced graphene oxide (RGO) yields a novel heterostructure so as to improve optical sensing performances. Here, we develop a high-performance WO3/RGO heterostructure-based optical sensor to work in the ultraviolet-to- visible region of electromagnetic spectrum. The WO3/RGO heterostructures with their varying ratios were synthesized via chemical route and were treated for characterization. The nature, structure, and morphology of the heterostructures were confirmed via XRD pattern and scanning electron microscopy (SEM) images. The absorption spectra investigated in the range of 200–800 nm reveal that their absorption peaks and bandgap mainly lie in the UV–Vis region, which gives the idea that these fabricated heterostructures would be well suited for optical sensors to work in the UV–Vis region. The optical sensor having pure RGO, pure WO3, and WO3/RGO heterostructures as detecting materials was fabricated onto Si/SiO2 substrate and was characterized on illuminating it with UV–Vis light of 390-, 532-, and 635-nm wavelengths, and the current–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}{)}$ </tex-math></inline-formula> and current–time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}{)}$ </tex-math></inline-formula> characteristics were measured. The addition of RGO to WO3 altered the device’s ability to detect UV and visible light while also increasing the output photocurrent to a much higher value. The obtained responsivity, detectivity, and quantum efficiency were found to be 16.24 mA/W, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${16}.{3} \times {10} ^{{7}}$ </tex-math></inline-formula> Jones, and 5.16%, respectively. At the same time, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}$ </tex-math></inline-formula> curves show continuous stable peaks under periodic on/off, indicating that the optical sensor is highly stable and the obtained rise and recovery times were much better demonstrating that the device also has good switching capability.