Long term scenarios for a sustainable global development suggest that it should be feasible by the middle of this century to provide over 80% of the electric power by a mix of energy from renewable sources. Photovoltaics (PV) is one important option which can provide a significant share of over 30% to such a mix. According to the learning curve for cost reduction of photovoltaics, thin film solar cells will play a major role. The APAS study, assigned by the European Commission, has shown that for large-capa city facilities (> 60 MW/year per plant) the manufacturing costs for thin film modules will become substantially lower, compared to crystalline silicon wafer modules. This project focuses on the most promising material and device options for thin film t echnologies, namely cadmium-free cells and modules, based on amorphous, micro- and polycrystalline silicon as well as on I-III-VI2-chalcopyrite compound semiconductors. The overall goal is to provide the scientific and technological basis for an industrial mass production of cost effective and highly efficient, environmentally sound, large-area thin film solar cells and modules. By drawing on a broad basis of expertise, the entire range of module fabrication and supporting R&D will be covered: Substrate s, semiconductor and contact deposition, monolithic series interconnection, encapsulation, performance evaluation and applications. The main objectives are: - significantly reducing the cost/efficiency ratio: towards 0.5 Euro/Wp on the long run - providing the know-how and the scientific basis for large-area PV modules by identifying and testing new materials and technologies with maximum cost reduction - developing the process know-how and the production technology as well as the design and fabrication of specialised equipment resulting in low costs and high yield in the production of large area thin film modules.