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

Abstract

The performance of dye-sensitized solar cells (DSSCs) consisting of anatase TiO2 nanoparticles that were synthesized via a hydrothermal method was studied. The synthesized TiO2 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 TiO2 nanoparticles (P25), the synthesized-TiO2 nanoparticles showed better performance. By adding diethylene glycol (DEG) before the hydrothermal process, the synthesized TiO2 nanoparticles (hereafter referred to as TiO2-DEG particles) shows narrower size distribution, larger specific surface area, higher crystallinity, and less surface defects than TiO2 (DEG free) particles. The analysis of photovoltaic properties of DSSCs based on TiO2-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 TiO2 nanoparticles improved the loading amount of dye sensitizers (N719), and enhanced the photocurrent of the DSSCs. As a result, the TiO2-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.