Influence of nitrogen doping on TiO2 nanoparticles synthesized by pneumatic spray pyrolysis method

Abstract

Improving the photon harvesting efficiency of dye sensitized solar cells (DSSCs) employing TiO2 photo-anode has been the major issue since 1991. So it is very important to discover new techniques that will enhance the properties of TiO2 nanoparticles (NPs) which will then prevent recombination of the photo-generated electron hole pairs and as well as improving the visible absorption properties of the TiO2. This will in turn improve the performance of the DSSC photo-electrode. The optical, electronic and structural properties of TiO2 NPs rely on factors like morphology, surface area, particle size and the presence of beneficial defects caused by dopants. This study focuses on the fabrication and characterization of nitrogen doped TiO2 (NPs) prepared by pneumatic spray pyrolysis (PSP) technique. The un-doped and nitrogen doped TiO2 NPs were prepared using titanium butoxide as a precursor and urea as the dopant. The morphological and structural properties of PSP synthesized NPs were evaluated using SEM, EDX, Raman Spectroscopy (RS), XRD and FTIR. SEM analysis revealed that the presence of nitrogen dopant results in a significant change in the surface morphology of the PSP synthesized NPs. RS revealed the presence of Raman vibrational modes and symmetry at 158 (Eg(1)), 208 (Eg(2)), 258 (B1g), 255 (B1g) 396 (B1g), 514 (A1g + B1g(2)) and 640 (Eg(3)) belonging to a mixed Anatase-Rutile phase. XRD analysis revealed that the PSP synthesized NPs have particles sizes of 10.90 nm, 11.31 nm, 11.93 nm and 14.14 nm for un-doped TiO2, 0.005 M TiO2, 0.015 M TiO2 and 0.025 M TiO2 NPs respectively. FTIR spectra of the PSP fabricated samples exhibited a peak at 616.22 cm−1 that is assigned to Ti–O vibrational stretching of the anatase phase of TiO2. UV–vis spectroscopy revealed a decrease in energy band gap with increase in dopant level for the TiO2 samples prepared.