Preparation of composite-layered structure of TiO 2 nanoparticles/TiO 2 nanotubes and its role in dye sensitized solar cell

Composite layered structure of TiO 2 nanoparticles (TiNPs) and TiO 2 nanotubes (TiNTs) was prepared by two-step anodizing of titanium at 50 V to form well-aligned TiNTs with uniform diameter, followed by spin coating the TiNPs of 10–30 nm prepared by hydrothermal synthesis. For smaller number of cycles, the spin coated nanoparticles were observed to penetrate into the nanotubular structure up to some extent. Morphology of the samples was studied by scanning electron microscopy (SEM). X-ray diffraction and Raman spectroscopy showed that TiNPs were composed of a mixture of brookite, anatase and rutile phases. Diffuse reflectance spectroscopy (DRS) was performed to assess the light scattering properties and measuring band gap. Photoluminescence spectroscopy was performed to assess the presence of defect. The DSSC made by five times spin coated photoanode shows percentage increase in efficiency of about 55% under back side xenon lamp irradiation. The good light scattering ability of the mixed layer formed by the penetration of nanoparticles without deteriorating the electron transport properties of the high aspect ratio nanotubes offered synergistic effects on the performance of DSSC in backside illumination mode.