Fabrication of surface-textured ZnO:Al/ITO bilayers with enhanced electrical and light-scattering properties

Highly textured ZnO:Al/ITO bilayers with excellent electrical and light-scattering properties were prepared on glass substrates using RF magnetron sputtering followed by a wet-etching process. In the bilayer structure, the sputtered ZnO:Al films were deposited on highly conductive ITO-coated glass substrates, and the ZnO:Al surfaces were subsequently chemically etched with a 1% HCl solution to modify the surface morphology. After wet-etching for the as-deposited ZnO:Al films without ITO films, the diffuse transmittance of the ZnO:Al films without ITO films deposited up to 100 °C was enhanced by the rough surfaces, accompanied by an abrupt increase in the sheet resistance to approximately 300 Ω/square due to the reduction in film thickness. The [001] orientation of the ZnO:Al films deposited on the ITO films with various crystalline orientations decreased significantly compared with the strong [001] preferred orientation of the ZnO:Al films deposited without the ITO films. For the textured ZnO:Al/ITO bilayers, a low sheet resistance below 10 Ω/square was obtained, and the light-scattering properties of these bilayers of 400-1100 nm were superior to those of the Asahi U glass that has been widely used as a transparent conducting electrode in thin-film solar cells. The material properties of the as-deposited and textured ZnO:Al/ITO bilayers with and without ITO films were systematically investigated.