Studies on tio2 and modified tio2 based photoanodes for dye sensitized solar cells

Abstract

In the present work TiO2 nanoparticles were prepared by solvothermal and microwave methods using titanium tetraisopropoxide as precursor and anhydrous ethanol as solvent respectively. The X-ray diffraction patterns and the Raman spectra of the TiO2 nanoparticles prepared by both methods exhibits peaks corresponding to the anatase phase of TiO2. The optical absorption of the prepared TiO2 nanoparticles is found to be in shorter wavelength region (lt 400nm) and this is the property which is associated with wide bandgap semiconductors. HRTEM (high resolution transmission electron microscope) images of the TiO2 nanoparticles synthesized by solvothermal method shows the presence of nearly uniform spherical shaped particles. TiO2 prepared by microwave method exhibited aggregate like morphology. From the HRTEM lattice fringe pattern the dspacing values were calculated, and it was found to be 0.36 nm and 0.35 nm, and this matches well with the obtained XRD results. The chemical states of the prepared materials were studied using X-ray photo electron spectroscopy (XPS) and from the survey spectrum the peaks corresponding to Ti, O, and C were observed. Ti 2p core level spectrum exhibits two binding energy peaks corresponding to Ti 2p3/2 and Ti 2p1/2 which can be assigned to the spin orbitals of Ti4+. The O1s peak of the nanoparticles is attributed to the Ti O surface species. The surface area and the pore size distribution of the prepared nanoparticles were studied using Brunauer Emmett Teller (BET) analysis and Barrett Joyner Halenda (BJH) analysis and from the results it is observed that the synthesized material is of mesoporous nature and has a uniform pore size distribution. TiO2 nanostructures were prepared by solvothermal method by treating TiO2 nanoparticles with 10M NaOH at 130°C for 10 hours. The X-ray diffraction patterns and the Raman spectra of the prepared TiO2nanostructures exhibits peaks corresponding to the trititanate phase of TiO2. The optical absorption of the prepared TiO2 nanostructures is found to be i