The Growth and Morphology Control of Nanostructured Metal Oxide for Dye-Sensitized Solar Cell and Gas Sensor

Abstract

In this study, growth of various metal oxides is controlled by using RF magnetron sputtering and solvothermal methods and as-grown metal oxides were applied for Dye Sensitized Solar Cell and gas sensor. The sputtering is one of the most popular Physical Vapor Deposition methods. It can make a homogenous thin film and mass production. Firstly, change of electrical and gas sensing properties with orientation and thickness of Indium Tin Oxide which is representative Transparent Conducting Oxide materials is investigated. In order to confirm influence on orientation and thickness, ITO is deposited on various YSZ single crystals, controlling deposition time (thickness). The different reasons electrical and gas sensing properties with orientation and thickness are confirmed because different In/Sn ratio and surface roughness exhibit. Secondly, it confirmed ZnO nanorods are directly grown on Fluorine doped Tin Oxide substrate without catalyst using RF magnetron sputtering. Although homogenous thin film is generally formed on substrate by sputtering, in this case, as-deposited ZnO exhibits growth behavior of rod shape. Reaction sites which are formed by react with Sn and ZnO suggest because SnO is decomposed by Sn and SnO2 over 400oC. Therefore, ZnO is not grown like thin film on FTO substrate, but nanorod shape. The growth of TiO2 nanorod array on TCO substrate using solvothermal method for DSSC application was researched. TiO2 nanorods, which are generally grown on FTO substrate using hydrothermal method, have disadvantages such as large diameter and bad adhesion on the substrate. Therefore, dense and well aligned TiO2 nanorods are grown using NMP and chloroform solvents in order to solve these problems. Dense TiO2 nanorods are grown by tuning NMP and HCl concentrations, which are disintegrated into thinner nanorods through etching process. This structure suggests more dye adsorption site. Additionally, it confirmed the surface morphology change with concentration. At last, previous thickness problems are solved by using chloroform (CHCl3) solvent. As previous mentioned, TiO2 nanorods, which is grown using hydrothermal method, are peeled off on the substrate in case of over specific thickness about 4~5μm. However, TiO2 nanorods using chloroform show over 8μm thickness and are well adhered on FTO substrate. Additionally, optimum TiO2 nanorod structure is fabricated through etching process and TiCl4 treatment which suggest more dye adsorption sites and current path.