Scalable Synthesis of Large-Area WS2 Thin Films from Tungsten Precursors by Thermal CVD and Their Application in Schottky-Barrier Solar Cells

Abstract

Two-dimensional tungsten disulfide (WS2) is a promising semiconductor for next-generation optoelectronic and photovoltaic devices, but scalable routes to uniform, large-area films remain challenging. In this study, a systematic thermal chemical vapor deposition (T-CVD) strategy is presented to synthesize centimeter-scale WS2 thin films by sulfurizing tungsten (W) precursors in a controlled sulfur vapor environment. High-purity sputtered W thin films on SiO2/Si and W foils were sulfurized at temperatures between 400 and 1000 C, with Raman spectroscopy identifying 800 C as the optimal growth temperature. Under these conditions, the films exhibit the characteristic E12g (349.7 cm-1) and A1g (416.8 cm-1) modes with narrow full-width at half-maximum values, indicative of high crystallinity and controlled thickness. Optical microscopy, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy collectively validate the creation of stoichiometric, layered WS2 with significantly enhanced uniformity and diminished roughness when utilizing sputtered W thin films in contrast to W foils. Leveraging this optimized process, WS2 films grown on W foils were transferred onto target substrates, including indium tin oxide (ITO)-coated glass, using a PMMA-assisted wet-transfer method that preserves structural integrity over large areas. Schottky-barrier solar cells with an Au/WS2/ITO architecture fabricated from these films deliver a short-circuit current density of 7.91 mA cm-2, an open-circuit voltage of 0.495 V, and a power conversion efficiency of 1.45 percent. These results demonstrate that sulfurization of W thin films and foils via T-CVD provides a scalable, substrate-compatible platform for integrating WS2 into practical optoelectronic and low-cost photovoltaic technologies.