An ITO‐Free Kesterite Solar Cell

Abstract

AbstractPhotovoltaic thin film solar cells based on kesterite Cu2ZnSn(S, Se)4 (CZTSSe) have reached 13.8% sunlight‐to‐electricity conversion efficiency. However, this efficiency is still far from the Shockley‐Queisser radiative limit and is hindered by the significant deficit in open circuit voltage (VOC). The presence of high‐density interface states between the absorber layer and buffer or window layer leads to the recombination of photogenerated carriers, thereby reducing effective carrier collection. To tackle this issue, a new window structure ZnO/AgNW/ZnO/AgNW (ZAZA) comprising layers of ZnO and silver nanowires (AgNWs) is proposed. This structure offers a simple and low‐damage processing method, resulting in improved optoelectronic properties and junction quality. The ZAZA‐based devices exhibit enhanced VOC due to the higher built‐in voltage (Vbi) and reduced interface recombination compared to the usual indium tin oxide (ITO) based structures. Additionally, improved carrier collection is demonstrated as a result of the shortened collection paths and the more uniform carrier lifetime distribution. These advances enable the fabrication of the first ITO‐free CZTSSe solar cells with over 10% efficiency without an anti‐reflective coating.