Influence of damp heat on the electrical properties of Cu(In,Ga)Se-2 solarcells

This article investigates the influence of damp heat treatments on the elec tronic properties of ZnO/CdS/Cu(In,Ga)Se-2 heterojunction solar cells. We o bserve losses of around 20% (50%) in the fill factor and between 5% (10%) i n the open circuit voltage after 100 h (1000 h) of damp heat exposure. Temp erature dependent current voltage measurements point to recombination in th e space charge region as the dominant loss mechanism before and after damp heat treatment. Admittance spectroscopy on the heterostructures indicates a reduction of type inversion at the CdS/Cu(In,Ga)Se-2 interface as well as an increase of deep defect levels in the Cu(In,Ga)Se-2 film upon damp heat tests. We ascribe the losses in the fill factor to the detected changes at the interface and the losses in the open circuit voltage to the increased d efect density in the absorber. (C) 2000 Elsevier Science S.A. All rights re served.