A comprehensive characterization of the interfaces in Mo/CIS/CdS/ZnO solar cell structures

The alignment of energy bands in a Mo/CIS/CdS/ZnO solar cell structure is presented as derived from individual measurements on the different interfaces. Special attention is paid to the surface chemistry of the molybdenum coated substrate. In this study we have performed in situ analyses on polycrystalline thin films starting with the molybdenum coated soda lime glass. The different films have been deposited sequentially under ultra high vacuum conditions and have been analyzed with photoelectron spectroscopy techniques. We have found that the Mo surface is significantly oxidized. Air annealing at 200 degrees C leads to a diffusion of sodium through the Mo layer. Mo-O compounds are present and Mo-Se compounds are formed during the evolution of the Mo-CIS interface. Band lineups have been determined for the CIS/CdS/ZnO interfaces of the solar cell structure. We have found no indication for band discontinuities deteriorating the solar cell device performance.