Cu(In,Ga)Se2-based thin-film solar cells are one of the most promising photovoltaic technologies nowadays. Despite significant improvements to the performance of Cu(In,Ga)Se2 (CIGS) in recent decades, the electrical characteristics of CIGS solar cells still have not been completely understood, especially the origins and the properties of metastabilities. This project focuses on the electrical characterization of CIGS based thin film devices with different Cu contents. Different characterization techniques have been used in this project. With varying Cu content, the structural properties, basic parameters, space charge distribution, temperature dependent properties, reverse bias- and white light illumination- induced metastable effects and breakdown behaviors have been investigated.