Grain-boundary types in chalcopyrite-type thin films and their correlations with film texture and electrical properties

Grain boundaries in chalcopyrite-type thin films can be divided into (near) Σ3 (twin) and random boundaries. It is shown that Σ3 grain boundaries in a 110/201-textured Cu(In,Ga)Se2 film may exhibit a preferential orientation perpendicular to the substrate, however, that this preferential orientation is not a common feature in 110/201-textured films. In general, it is not possible to draw conclusions about the Cu(In,Ga)Se2 thin-film microstructure based on its texture and vice versa. From cathodoluminescence and electron backscatter diffraction measurements acquired on the same area of a CuInS2 cross-section sample, it is concluded that the density of non-radiating recombination centers at random boundaries is substantially larger than that at Σ3 (twin) boundaries. Evaluation of reconstructed phase images from transmission electron microscopy focus series revealed considerably larger mean-inner potential wells at a random boundary as compared with Σ3 (twin) boundaries.