Improvement of Optical Properties of CZTSSe-Based Solar Cells and Photocathode Devices via Cd Doping

Cu₂ZnSn(S,Se)₄ material is a material that replaces CuInGaSe₂, which is currently being researched, and is attracting attention as an eco-friendly and economical material because it does not use indium or gallium. However, various studies are being conducted to improve CZTSSe devices due to their low solar cell efficiency and low hydrogen conversion efficiency in PEC water splitting. Among them, cation doping is known to significantly contribute to improving device performance by improving the optoelectric properties of CZTSSe thin films. Cations doped into CZTSSe include various elements such as Ge, Cd, and Ag, and among these, Cd can be easily doped using the Chemical Bath Deposition method. Cd is doped into CZTSSe to control secondary phase and void formation, and when applied to a device, it improves photocurrent and improves light-hydrogen conversion efficiency. In this study, CZTSSe was doped with Cd by deposition time (9.5, 10.5, 11.5 minutes) using the CBD method to analyze its single thin film properties, and solar cells and PEC photocathodes were manufactured under the same conditions to measure device characteristics. As a result, the thin film sample doped with Cd for 11.5 minutes showed excellent photoelectric properties, solar cell efficiency was measured up to ~8%, and photocurrent was measured up to ~15 mA/cm² as a PEC photocathode.