Mixed-phase TiO2 nanorods assembled microsphere: crystal phase control and photovoltaic application

Here, mixed-phase TiO2 nanorods assembled microspheres were fabricated via a facile one-step hydrothermal process. The synthesized samples were investigated employing X-ray powder diffraction (XRD), Raman spectrometry, field emission-scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The study shows the interesting symbiotic phenomenon occurred in the mixed anatase and rutile phase TiO2. The mixed crystalline phase of anatase-rutile ratios were accurately tuned by adjusting the concentration of disodium edetate (EDTA). The crystalline phase has a great influence on their photovoltaic performance. The photoelectric conversion efficiency increases by 162% when the anatase weight ratio increases from 6% to 51%. While a 263% increase in the photoelectric conversion efficiency of the optimized mixed-phase TiO2 nanorods is achieved when compared to the pure rutile phase TiO2. Accordingly, the DSSCs based on the optimized mixed-phase TiO2 nanorods assembled microspheres show a high open circuit voltage of 0.85 V and a conversion efficiency of 8.85% with a relative low dye adsorption of 0.99 x 10(-7) mol cm(-2).