Electronic properties of grain boundaries in Cu(In,Ga)Se2 thin films with various Ga-contents

We present a study on the electronic properties of grain boundaries (GBs) in polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films by means of Kelvin probe force microscopy. As grown as well as KCN-treated films were investigated comparatively. No influence of the chemical treatment on the electronic properties of GBs was found. GBs generally exhibited large variations in their electronic properties. By means of a novel method of data analysis both potential barriers for holes and electrons were found at GBs, in a range from −118 mV to +114 mV, as well as GBs without potential barrier. No dependence of the electronic GB-properties on the Ga-content was detected. Consequently, we conclude that there is no correlation between the electronic properties of GBs and the obtained maximum efficiencies of CIGSe thin film solar cells as a function of the Ga-content.