Shunt mitigation in ZnO: Al/i-ZnO/CdS/Cu(In, Ga)Se2 solar modules by the i-ZnO/CdS buffer combination

The influence of the i-ZnO/CdS buffer layer on intentionally produced defects in Cu(In, Ga)Se-2 (CIGS) mini-modules is investigated by electroluminescence (EL) imaging. Macroscopic shunts of the dimension of 100 mu m in length and several mm in width were produced by mechanically removing locally one or several of the layers during the module production process. After creating the defects the modules were finished in the usual way. It is found that heavy shunts were produced whenever the doped ZnO: Al came into contact with the Mo back contact. The decline of photovoltaic performance is seen by a decrease of the EL intensity of the damaged cell. In contrast, considerable shunt mitigation was observed whenever the i-ZnO/CdS buffer combination was present. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim