Empowering Solar Cells With Non‐Toxic Cu 2 O and Zn(O,S): A Sustainable Approach for CIGS Solar Cells

ABSTRACT This study investigates the incorporation of a non‐toxic p‐type Cu 2 O layer as a back‐contact hole collector on the Cu(In,Ga)Se 2 (CIGS) absorber layer in thin‐film solar cells, alongside a wide‐bandgap and non‐toxic Zn(O,S) buffer layer as the n‐type material. Simulations analyze the effects of absorber layer thickness, Ga concentration, defect density, and recombination on the photovoltaic performance, as well as the influence of various metal work functions, back‐contact and alternative buffer layers. The proposed design achieves a significant improvement in current density, reaching 36.8 mA/cm 2 compared to 33.2 mA/cm 2 in a reference cell using a Zn(O,S) buffer layer and no Cu 2 O. The Cu 2 O layer enhances hole conduction at the rear contact due to its p‐type nature, thereby improving device efficiency. Additionally, the Zn(O,S) buffer layer, with its larger bandgap of 2.7 eV compared to the 2.4 eV of CdS, reduces parasitic absorption losses and significantly enhances photocurrent in the UV spectrum. As a result, the solar cell's conversion efficiency improves from 22.11% to 25.35% with the inclusion of Cu 2 O and the substitution of CdS with Zn(O,S). These findings demonstrate that Cu 2 O is a promising back‐contact hole collector, and the proposed CIGS solar cell design offers a pathway to developing high‐efficiency thin‐film solar cells.