Optimized VO2-TiO2 photoanodes for high-efficiency solid-state dye-sensitized solar cells

Abstract

Vanadium dioxide demonstrates excellent thermal, chemical stability and shows enhanced properties when doped with other metals and metal oxides. These variables are essential for dye-sensitized solar cell (DSSC) photoanode tuning and performance enhancement. In this study, VO₂-doped TiO₂ nanoparticles were synthesized via the sol-gel method. The resulting VO₂-doped TiO₂ nanoparticles were then coated using the doctor blade method on Indium-doped tin oxide (ITO) glass substrates and used as a photoanode in a solid-state dye-sensitized solar cell (DSSC) for the very first time. Structural analysis confirmed that VO₂ doping reduced TiO₂ crystallite size, leading to an increased surface area and enhanced dye loading, thereby improving the cell’s photocurrent conversion efficiency. Ultraviolet-Visible spectroscopy revealed that VO₂ incorporation introduced an inherent energy barrier, further enhancing light absorption and overall performance. A nanocomposite polymer electrolyte was prepared using the solution cast method, composed of polyethylene oxide with varying montmorillonite nanoparticle and multi-walled carbon nanotube (MWCNT) loadings as primary and secondary nanofillers, was utilized to enhance cell stability. X-ray diffraction (XRD) analysis indicated a significant reduction in polymer crystallinity upon nanofiller integration. Electrical impedance spectroscopy at room temperature demonstrated that nanofiller incorporation improved electrolyte conductivity, with the addition of MWCNTs further increasing A.C. conductivity from 5.6 × 10⁻⁴ to 7.63 × 10⁻³ S cm⁻¹, attributed to the formation of conductive pathways. The combination of the VO₂-TiO₂ photoanode and the optimized solid polymer electrolyte achieved a peak solar efficiency of 3.8%, highlighting its potential for next-generation solid-state DSSCs.