Transparent and conductive films are key components for optoelectronic devices. They are applied as n-type transparent electrical contacts for inorganic and organic light emitting diodes, solar cells and flat panel displays as well as p- and n-type active semiconductive oxides to setup wide band gap p-n junctions and devices for the emerging field of transparent and radiation hard electronics. The demand for these films is strongly increasing due to the extensive market growth in these areas but the solutions available today only partially fulfill the requirements on low resistivity, high transmittance, large area deposition, low cost manufacturing, and ability for fine patterning, light scattering and precise alignment of the electronic structure to surrounding semiconductors. The cooperation of five Fraunhofer Institutes within the "Fraunhofer Project MAVO METCO" aims towards establishing fundamental knowledge and control about the defect chemistry, structure and morphology of the transparent semiconductive oxides. The goal is to achieve materials with outstanding properties such as n-type transparent conductive oxides with tailored work function and excellent durability, novel delafossite based p-type materials allowing cost effective large area deposition, oxide based p-n heterojunctions and Ag based electrodes to be used for thin film photovoltaics and organic light emitting diodes. Starting from first-principle modelling of the electronic structure, we address the development of new transparent conductive layers by PVD and Sol-Gel ending up with device implementation for OLEDs and organic as well as Si based a-Si:H/mu c-Si:H and HIT solar cells. (C) 2009 Elsevier B.V. All rights reserved.