Synthesis of Mesoporous TiO2 Spheres via the Solvothermal Process and Its Application in the Development of DSSC

This study examined the synthesis of the n -type nanostructured titanium dioxide semiconductor using a combined sol-gel/solvothermal method at 200°C, varying the concentrations of H 2 O and HCl used as a catalyst for the hydrolysis of the titanium isopropoxide precursor. A white powder of TiO 2 nanoparticles was obtained via the solvothermal process. Scanning electron microscopy revealed a spherical morphology of the TiO 2 nanoparticles, with their diameter ranging from 2 to 7 microns as the HCl concentration increases. High-resolution electron microscopy and X-ray diffraction showed that the spheres are mesoporous titanium oxide (TiO 2 m ) composed of nanocrystals with an anatase crystalline phase whose crystallite diameter grows from 8 to 13 nm as the HCl concentration increases. On the contrary, optimizing the H 2 O concentration enabled a decrease in the crystallite size of TiO 2 m and increases in the surface area and the energy band gap of TiO 2 m . The enlarged surface area enabled an increase in the number of contact points between TiO 2 m and the dye of dye-sensitized solar cells (DSSCs), resulting in a better solar cell performance. The white powder was used to prepare a TiO 2 m film via the screen-printing technique, which was used in the development of DSSC. The performance parameters of the DSSC ( I SC , V OC , FF, and η %) were correlated with the synthesis parameters of TiO 2 m . This correlation showed that H 2 O and HCl greatly influence the semiconductor properties of TiO 2 m , along with the short-circuit current J SC and the conversion efficiency η% of the DSSC.