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

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.