Properties of multilayered ZnO/Al/ZnO transparent film electrodes: models and experiments

Abstract

ZnO/Metal/ZnO multilayers have been recognized as good candidates for transparent conductive thin films for application in solar cells and optoelectronic devices. One of the important challenges in the experimental design of such structures is the lack of optimum metal thickness range such as Al in ZnO/Al/ZnO multilayers. The present work overcomes this limitation by investigating how Al thickness affects the optical properties of such multilayered films. In this paper, optical simulations are used to explore the possibility of ultrathin, high transparent ZnO/Al/ZnO multilayer films. MultilayeredZnO/Al/ZnO film with mid-Al layer thicknesses between 1 and 10 nm are shown to have optical transmittances between 70 and 90%. Variations in the ZnO thickness between 10 and 100 nm are shown to have little effect on the optical characteristics of the ZnO/Al/ZnO multilayers, for a given Al thickness. The optimum thicknesses for the ZnO and Al layers are predicted and discussed for the design of transparent conducting ZnO/Al/ZnO electrodes. The reliability of the simulation method is verified by comparing the computational and experimental results for a related system, namely, single-layered ZnO thin film deposited on glass substrates.

 Keywords: Absorbance, multilayers, reflectance, TCOs, transmittance