Synthesis of morphology controlled Titanium dioxide particles and fabrication of remodeled titanium dioxide multi-layers for dye-sensitized solar cells

Abstract

DSSC (Dye-Sensitized Solar cell) based on nano-crystalline TiO2, have attracted considerable scientific and technological interest. General DSSC is fabricated with TiO2 bilayer which is consisted of TiO2 (20nm) nanoparticle and TiO2 (400nm) submicroparticle. In this study, we used remodeled TiO2 layers consisted of atomic layer deposited TiO2 layer, nanocrystalline TiO2 layer and rod-like anatase particles. We controlled the combination of these various structures, and we made sure how much they influenced energy conversion efficiency, respectively. Recently, One-dimensional (1D) nanostructures, such as nanorods, nanowires, nanobelts, and nanotubes, and atomic layer deposition(ALD) as nano-scale and good step-coverage deposition have become the focus of intensive research owing to their unique applications in fabrication of nano-scale devices. In chapter 1, the overview about dye-sensitized solar cells and titanium dioxide are shortly introduced. DSSCs based on nanocrystalline TiO2 films present an attractive alternative to conventional solid-state devices. In chapter 2, the effect of surfactants on the synthesis of TiO2 nanostructures were investigated at the low temperature sol-gel method and solvothermal conditions in aqueous and non-aqueous solutions. We used surface active agents which have the hydrogen bond such as aniline (– NH) or PVA (– OH) as additives. As a result, sphere-like TiO2 nanoparticles and TIO2 nanorods with various morphologies, sizes and aspect ratios were synthesized depending on the different surfactants. In chapter 3, We fabricated nano-scale TiO2 thin films for DSSC electrode application using ALD (atomic layer deposition) method at the low temperatures of 200℃. We confirmed that the ALD-processed TiO2 thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices. The nanostructures and morphologies of as-prepared TiO2 materials were investigated by field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). &#8195