Efficient TiO2 blocking layer for TiO2 nanorod arrays-based dye-sensitized solar cells

Thin compact titanium dioxide (TiO2) blocking layer was chemically deposited on fluorine doped tin oxide (FTO) coated glass substrate using peroxo-titanium complex (PTC) solutions. After that, TiO2 nanorod (TNR) arrays of different thickness were grown on this TiO2 film by hydrothermal method. The blocking layer's crystal structure, morphology, and thickness were characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy measurements. XPS analysis revealed that the TiO2 blocking layer derived from PTC maintains high degree of Ti-O-Ti linkage. These TiO2 materials were used as the photo-anode in the fabrication of dye-sensitized solar cells (DSSC). TNR arrays-based DSSC of thickness 6.2 μm with TiO2 blocking layer showed higher photo-electric conversion efficiency of 1.46% compared to devices with similar TNR array of thickness, 6.1 μm without TiO2 blocking layer (1.19%). The reason can be ascertained from dark photocurrent density-voltage measurements of the devices which reveal that the TiO2 blocking layer diminishes the dark current arising from reduction of I3− at the FTO/electrolyte interface apparently by blocking direct contact of the redox electrolyte with the FTO layer.