Investigation on optical and electrical properties of multilayer ITO/AZO/ITO transparent conductive oxides

Abstract

This paper examines how varying the thickness of the indium tin oxide (ITO) seed layer, ranging from 8 to 20 nm, impacts the optical, electrical, and structural properties of triple-layer transparent conductive oxide ITO/aluminum doped zinc oxide (AZO)/ITO. ITO and AZO films were deposited by DC and RF magnetron sputtering, respectively. The thickness and density of each layer were measured by X-ray reflectometry (XRR). X-ray diffraction showed that as the thickness of the ITO seed layer increased, both the average size of the crystallites and the volume of the crystalline phase in the AZO film also increased. Measurements of the electrical characteristics indicated a decrease in resistivity as the thickness of the ITO seed layer increased. This reduction is attributed to enhanced charge mobility, resulting from improved crystallinity. It has been shown that a 20-nm-thick ITO seed layer is sufficient to achieve a charge mobility comparable to that of pure ITO films. The photoluminescence spectra have shown a decrease in the concentration of the oxygen vacancies with the introduction of both the cover and seed layers of ITO. The figure of merits (FOM) of the triple-layer coatings and the optical constants of the AZO and ITO films were calculated. The results of this paper indicate that the ITO20/AZO48/ITO12 triple-layer coating possesses optimal characteristics for use in high-efficiency silicon solar cells.