Ionic conductivity of vanadium-doped tin disulfide for photovoltaic applications.

Tin disulfide (SnS) is an environmentally friendly and widely available material with a band gap ranging from approximately 2.20 to 2.45 eV, making it a strong candidate for use as a buffer layer in photovoltaic technologies. In this study, SnS was synthesized using the hydrothermal method. To enhance its interaction with visible light, vanadium (V) atoms-also earth-abundant and characterized by a low band gap-were incorporated into the SnS matrix. The atomic percentage of vanadium was varied from 0% to 10% in increments of 2%. A previous study conducted on similar mixed SnVS samples, though with different vanadium concentrations, suggested that V-doped SnS thin films could be suitable as buffer layers for solar cell fabrication. However, the electrical conductivity of these samples had not been quantified, and therefore, such a conclusion cannot be definitively confirmed. In this work, electrochemical impedance spectroscopy was used to determine the conductivity and diffusivity of vanadium-doped samples as a function of temperature. Our results revealed a percolation threshold at approximately 6% vanadium content, with notable changes in conductivity observed around 120 °C. The sample doped with 6% vanadium exhibited a significantly enhanced photocurrent response (3.0 × 10 A cm) compared to the undoped SnS thin films (4.0 × 10 A cm). These findings indicate that vanadium incorporation significantly alters the crystallinity of SnS, leading to changes in the melting temperature of the mixed SnVS samples. Such changes may induce structural relaxation, lattice dilation, or enhanced atomic interactions. Together with previous studies, these results highlight that V-doped SnS is a promising candidate for optoelectronic applications, including photoelectrochemical catalysis, photodetectors, and photovoltaic devices.