Transformation of TiO2 nanoparticles to nanotubes by simple solvothermal route and its performance as dye-sensitized solar cell (DSSC) photoanode

Abstract

Titania nanotubes were synthesized by simple solvothermal method using quasi crystalline TiO2 nanoparticles as the starting material without using autoclave. In the presence of concentrated NaOH (sodium hydroxide), TiO2 nanoparticles were transformed into nanotubes. The complete transformation of nanoparticles to nanotubes was witnessed using Field Emission Scanning Electron Microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) images and further, the materials were found to be polycrystalline in nature. From the X-ray diffraction pattern and Raman analysis, the TiO2 nanoparticles were found to exhibit the anatase phase and the nanotubes were found to exhibit the titanate phase. The surface area and pore size distribution were analysed using BET (Brunauer–Emmett–Teller) and BJH (Barrett–Joyner–Halenda) analysis. The surface area of the nanotubes was found to be higher compared to the initial nanoparticles and bimodal type pore distributions were observed from the BJH study. The bandgap and defect emissions of the nanotubes and nanoparticles were analysed using UV–Vis absorption and photoluminescence (PL) analysis. The chemical states of the prepared nanoparticles were further characterized using X-ray photoelectron spectroscopy. The Dye-sensitized solar cells (DSSC) were fabricated using the prepared TiO2 nanostructures as photoanodes and their power conversion efficiencies were analysed.