Grain boundary properties of Cu(InGa)Se2 thin film were measured using electron beam induced current, electron back scatter diffraction patterns and scanning spreading resistance microscopy methods. The weak electron beam induced current signal was observed in back-side grains which were separated by the random grain boundaries running parallel to the substrate. Furthermore, it was shown by scanning spreading resistance microscopy that the tilt grain boundaries had low resistivity. The two phenomena were explained by a previously proposed grain boundary model. Finally, the grain with a weak electron beam induced current signal was assessed by the transmission electron microscope, and it was found that the grain had a twin cluster. The edge of the cluster reached at the CdS/CIGS interface, and the interface was disordered, which caused the minority carrier to sink, limiting the solar cell performance. Characterization of Cu(InGa)Se2 Grain Boundary Properties by Electron- and Tip-Probe Methods. S.Oonishi, M.Kawamura, N.Takano, D.Hashimoto, A.Yamada, M.Konagai: Thin Solid Films, 2011, 519[21], 7347-50