Size-Controlled Cu₃VSe₄ Nanocrystals as Cathode Material in Platinum-Free Dye-Sensitized Solar Cells

In this work, we report the first single-step, size-controlled synthesis of Cu 3 VSe 4 cuboidal nanocrystals, with the longest dimension ranging from 9 to 36 nm, and their use in replacing the platinum counter electrode in dye-sensitized solar cells. Cu 3 VSe 4, a ternary semiconductor from the class of sulvanites, is theoretically predicted to have good hole mobility, making it a promising candidate for charge transport in solar photovoltaic devices. The identity and crystalline purity of the Cu 3 VSe 4 nanocrystals were validated by X-ray powder diffraction (XRD) and Raman spectroscopy. The particle size was determined from the XRD data using the Williamson–Hall equation and was found in agreement with the transmission electron microscopy imaging. Based on the electrochemical activity of the Cu 3 VSe 4 nanocrystals, studied by cyclic voltammetry, the nanomaterials were further employed for fabricating counter electrodes (CEs) in Pt-free dye-sensitized solar cells. The counter electrodes were prepared from Cu 3 VSe 4 nanocrystals as thin films, and the charge transfer kinetics were studied by electrochemical impedance spectroscopy. The work demonstrates that Cu 3 VSe 4 counter electrodes successfully replace platinum in DSSCs. CEs fabricated with the Cu 3 VSe 4 nanocrystals having an average particle size of 31.6 nm outperformed Pt, leading to DSSCs with the highest power conversion efficiency (5.93%) when compared with those fabricated with the Pt CE (5.85%).