Enhanced omni-directional performance of copper zinc tin sulfide thin film solar cell by gradient index coating

Many types of thin-film solar cells have a top, transparent conducting oxide (TCO) coating (such as aluminum-doped zinc oxide (AZO)) through which light is transmitted and current collected. In this paper, we demonstrate an effective antireflective coating for TCO surfaces using a gradient index coating formed from co-sputtered AZO and silicon dioxide (SiO2) targets that reduces reflection loss from the TCO. When applied to an active solar device, the power conversion efficiency of the solar cell increased by >10% when measured at normal incidence and >20% at angles 10° or greater.