Facile synthesis of rutile TiO2 nanorod microspheres for enhancing light-harvesting of dye-sensitized solar cells

Sub-micrometer sized rutile TiO2 nanorod microspheres with diameters of 500-700 nm and with a specific surface area of 63.7 m(2) g(-1) were synthesized via a salt-assisted hydrothermal method. Morphological evolution as a function of reaction time was carried out to gain insight into the formation mechanism of the nanorod microspheres. Unlike traditional bulk rutile TiO2 particles, the nanorod microspheres could provide dual-functions of adsorbing dye molecules and strong light-harvesting efficiency when they were fabricated as a scattering overlayer in dye-sensitized solar cells (DSSCs). Furthermore, the inherent nanorods would provide excellent electron percolation pathways for charge transfer as confirmed by electrochemical impedance spectroscopy. Consequentially, DSSC with the scattering overlayer exhibited a 39% increment of cell efficiency (7.32%) compared with the DSSC without one (5.28%), and the efficiency was also a little higher than the DSSC with the same thickness composed of only nanocrystallites (7.14%).