Synthesis of nano-TiO2 assisted by diethylene glycol for use in high efficiency dye-sensitized solar cells

The performance of dye-sensitized solar cells (DSSCs) consisting of anatase TiO 2 nanoparticles that were synthesized via a hydrothermal method was studied. The synthesized TiO 2 nanoparticles were characterized by X-ray diffraction (XRD), nitrogen sorption analysis, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and UV–vis spectroscopy. Then the J - V curve, electrochemical impedance spectroscopy (EIS), and open-circuit voltage decay (OCVD) measurement were applied to evaluate the photovoltaic performance of DSSCs. Compared with the commercial TiO 2 nanoparticles (P25), the synthesized-TiO 2 nanoparticles showed better performance. By adding diethylene glycol (DEG) before the hydrothermal process, the synthesized TiO 2 nanoparticles (hereafter referred to as TiO 2 -DEG particles) shows narrower size distribution, larger specific surface area, higher crystallinity, and less surface defects than TiO 2 (DEG free) particles. The analysis of photovoltaic properties of DSSCs based on TiO 2 -DEG particles showed that the recombination of electron-hole pairs was decreased and the trapping of carries in grain boundaries restrained. It was believed that the photoelectrode fabricated with the as-prepared TiO 2 nanoparticles improved the loading amount of dye sensitizers (N719), and enhanced the photocurrent of the DSSCs. As a result, the TiO 2 -DEG particle based cells achieved a photo-to-electricity conversion efficiency ( η ) of 7.90%, which is higher than 7.53% for the cell based on TiO2 (DEG free) and 6.59% for the one fabricated with P25.