Characterization of Cu(InGa)Se2 grain boundary properties by electron- and tip-probe methods

Grain boundary (GB) properties of Cu(InGa)Se2 thin film were measured using electron beam induced current (EBIC), electron back scatter diffraction patterns (EBSD) and scanning spreading resistance microscopy (SSRM) methods. The weak EBIC signal was observed in back-side grains which were separated by the random grain boundaries (GBs) running parallel to the substrate. Furthermore, it was shown by the SSRM that the tilt GBs had low resistivity. The two phenomena were explained by our previous proposed GB model [1]. Finally, the grain with a weak EBIC signal was assessed by the transmission electron microscope (TEM), 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.