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 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.