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[en] This thesis constitutes a comprehensive study of the surface physics of epitaxial CuInSe2 films. It comprises analyses of the surface morphology and reconstruction, electronic band structure as well as hetero-junctions relevant to photovoltaic applications. Therefore, especially the aspect of stoichiometry variation from the CuInSe2 to the copper-deficient defect phases was considered. Preparation and analysis was completely performed under ultra-high vacuum conditions in order to ensure the investigation of well-defined samples free of contaminants. For some of the analysis techniques, single-crystalline samples are indispensable: They allow for the determination of surface periodicity by low-energy electron diffraction (LEED). In combination with concentration depth profiling by angle-resolved x-ray photoemission, to types of surface reconstructions could be distinguished for the near-stoichiometric CuInSe2(112) surface. In the copper-rich case, it is stabilized by CuIn anti-site defects and on the indium-rich side by 2 VCu defects, as predicted by surface total energy calculations by Jaffe and Zunger. Both configurations correspond to a c(4 x 2) reconstruction of the zinc blende type (111) surface. For the defect compound CuIn3Se5, a sphalerite order of the surface was found, which points at a weakening or absence of the chalcopyrite order in the bulk of the material. The unusual stability of the (112) surface could also be proven by comparison with the reconstruction and surface order of (001) and (220) surfaces. The results from surface analysis were used to measure the valence band structure of the epitaxial samples by synchrotron-based angle-resolved photoelectron spectroscopy. The CuInSe2(001) surface gives access to the high symmetry directions Γ-T and Γ-N of momentum space. By contrasting the data obtained for the stoichiometric surface with the copper-poor defect compound, a reduction of the valence band dispersion and a broadening of electron states was observed, which can be understood as a higher localization of electronic states and lower crystal quality. In addition, a strong rearrangement of the copper partial density of states was shown. The intimate knowledge of the electric structure was then exploited to demonstrate the valence band discontinuity between CuInSe2 and CuIn3Se5. The analysis by photoemission yielded a valence band offset of 0.28 eV, again in reasonable agreement with theoretical results. The p-n-junction in chalcopyrite solar cells is situated near the absorber-buffer interface, which is therefore crucial for the device performance. In this thesis, ZnO deposited from metal-organic precursors on epitaxial CuInSe2 was investigated as cadmium-free buffer material. In the course of contact formation, the interfacial region of the absorber becomes depleted of copper. Additionally, a thin intrinsic ZnSe layer is formed, prior to the growth of ZnO. The derived band alignments show no dependence on the surface orientation of the chalcopyrite substrate and are consistent with theoretical results. The conduction band lineup is favorable for the application in solar cells.