Controlled synthesis of mesoporous anatase TiO2 microspheres as a scattering layer to enhance the photoelectrical conversion efficiency

Abstract

TiO₂ microspheres with a large surface area, high crystallinity, uniform nanostructure and good light scattering properties were synthesized in an acetone–phenol mixed solvent via a simple solvothermal process. X-ray diffraction patterns and electron microscopy images indicated that the prepared TiO₂ microspheres had a highly mesoporous structure and were composed of highly crystalline anatase nanoparticles. By tuning the ratio of the mixed solvent, high-quality TiO₂ microspheres were obtained with controllable surface areas of 122–168 m² g⁻¹. Then, the mesoporous anatase TiO₂ microspheres were used as the scattering layer of the photoelectrode, which is expected to produce high efficiency dye-sensitized solar cells (DSSCs). Compared with photoelectrodes with pure TiO₂ nanoparticles or mesoporous anatase TiO₂ microspheres, DSSCs based on a photoelectrode with a TiO₂ nanoparticle underlayer and a microsphere scattering layer yield the highest photoelectrical conversion efficiency of 7.94%. This is because the obtained TiO₂ microspheres have a large surface area and exhibit excellent light scattering, allowing for fast interfacial charge transfer, low series resistance, and superior charge collection efficiency. This has been systematically observed by the electrochemical impedance spectroscopy, intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy.