Fabrication of Al-doped ZnO thin-films by ion beam assisted molecular beam epitaxy and their application to dye-sensitized solar cells

摘要

Al-doped ZnO thin films were deposited on glass substrates at room temperature by ion-beam-assisted molecular beam epitaxy (MBE) deposition. The crystallinity, microstructure, surface roughness, and electrical, optical and mechanical prosperities of thin films were investigated as a function of the deposition parameter and the ion energy. The microstructure of the Al-doped ZnO crystalline films on amorphous glass substrates was closely related to oxygen ion bombardment on the growing surface. The effects on the film may be divided into two categories: 1) the enhancement of atom mobility at low energetic ion bombardment and 2) the surface damage by radiation damage at high energetic ion bombardment. A large sized grain structure was obtained in the films deposited at 300 eV. At a high energy ion bombardment of 600eV, however, only a smaller grain structure with high hardness was observed. The electrical properties of the deposited films were significantly related to the change of microstructure and crystallinity. The Al-doped ZnO films with a large size grain structure have better electrical properties than those with a smaller grain structure because the grain boundary scattering decreased in the large size structure compared with the small size grains. The optical photoluminescence of Al-doped ZnO thin films was dependent on the grain size. And then the dye-sensitized solar cell (DSSC) fabricated on the AZO film grown at ion beam energy 300eV condition, it exhibits superior conversion efficiency than the other condition sample. Therefore, transparent conductive glass applying in DSSCs must have a low sheet resistance, a high transmittance in the ultraviolet visible infrared region and an excellent surface microstructure.