Characteristics of an oxide/metal/oxide transparent conducting electrode fabricated with an intermediate Cu–Mo metal composite layer for application in efficient CIGS solar cell

Abstract

In order to improve the performance of Al-doped ZnO (AZO) based transparent conducting oxide (TCO) films, a metal Cu–Mo composite layer has been introduced between two AZO films to form an oxide/metal/oxide structure. The AZO/Cu–Mo/AZO (ACMA) multilayer film was prepared at room temperature by direct current magnetron sputtering equipped with multi-targets. To evaluate the performance of ACMA film as transparent conductors, the optical and electrical properties have been studied. These studies have shown the introduction of Cu–Mo composite layer significantly improves the performance of transparent conducting ACMA film compared to the AZO film as well as AZO/Cu/AZO (ACA) and AZO/Mo/AZO (AMA) multilayer films. The opto-electrical properties of the ACMA film critically depend on the thickness of the Cu–Mo composite layer. The highest figure of merit ∼7.96 × 10⁻⁴ Ω⁻¹ is obtained for the ACMA film with a 10 nm thick Cu–Mo composite layer, indicating optimum conditions for the fabrication of transparent conducting electrodes. The CIGS solar cell fabricated with the ACMA electrode exhibits substantially higher efficiency (11.59%), compared to ACA or AMA electrodes. The gain in the cell efficiency is attributed to the improved opto-electrical characteristics of the ACMA electrode, resulting from the optimum optical transmittance and charge carrier collections.