Enhanced grain orientation in Sb2Se3 thin films deposited on Mo/BSG substrates via RF-sputtering and selenization

Abstract

The alignment of the Sb2Se3 absorber grains along the c-axis, resulting from their quasi-1D ribbon-like growth, has been found to enhance current density, thereby enabling high power conversion efficiencies in Sb2Se3-based thin film solar cells. This study presents a controllable method for depositing Sb2Se3 thin films with highly oriented grains and a compact morphology, making them suitable for large-scale solar cell applications. A combination of magnetron sputtering and post-deposition isothermal selenization techniques was used. This process involved sputtering antimony onto Mo-coated Borosilicate glass (BSG) substrates, followed by selenizing the films at different temperatures in argon-gas filled quartz ampoules. The influence of several partial Ar-gas pressures and selenization temperatures on the grain growth was studied to achieve enhanced preferred grain orientations and compact morphology of the Sb2Se3 thin films. Selenization at 380 °C resulted in dominant vertical grain orientations with respect to the substrate surface of the Sb2Se3, as confirmed by scanning electron microscopy and X-ray diffraction analysis, without compromising surface compactness. Although occasional micro-voids remain in the films, further optimization could eliminate these imperfections. The developed sequential method, where Sb layer was deposited by RF-sputtering process, followed by an annealing at elevated temperature in the presence of Se and argon gas pressure, holds potential for large-scale production and the fabrication of other quasi-1D chalcogenide thin films.