Shunt mitigation in ZnO:Al/i-ZnO/CdS/Cu(In,Ga)Se2 solar modules by the i-ZnO/CdS buffer combination (Phys. Status Solidi A 3∕2015)

The influence of the i‐ZnO/CdS buffer layer combination on intentionally produced defects in Cu(In,Ga)Se2 (CIGS) minimodules is investigated by electroluminescence (EL) imaging in the work by Misic et al. (pp. 541–546). Shunts with diameters of about 100 μm were produced by mechanically removing locally one or several layers during the module production process. The cover image schematically illustrates a defect‐free CIGS solar cell next to three intentionally implemented defective layer sequences together with their corresponding EL images. The authors find that the i‐ZnO/CdS buffer combination mitigates shunts effectively, despite a hole in the CIGS absorber and Mo electrode. However, the high‐ohmic i‐ZnO layer alone without the CdS buffer layer is less effective. Misic et al. demonstrate that the covering coating by the chemical bath deposited CdS fills cavities and covers rough edges at the damaged Mo and CIGS, and thus provides a smoothened surface where the sputtered i‐ZnO can form an intact high‐ohmic layer between the front and back electrode. In this work it is argued that the i‐ZnO/CdS buffer layer has a strong shunt mitigating effect. This may be an important aspect to consider in the development of Cd‐free buffer combinations or buffer layers for kesterite‐based solar cells.