This project aims at developing highly efficient barrier coatings on flexible polymer substrates,for photovoltaic applications. Thanks to great flexibility and expected very low cost, thedevelopment of organic solar cells opens the way to new markets, dedicated to unusual curvedand/or large area supports. There, the need for transparent efficient barriers againstenvironmental species like water or oxygen is even more demanding than for food andpharmaceutical packaging. Indeed, solar conversion efficiency of organic photovoltaic devicesis nowadays reaching very interesting values (up to 6%), but lifetime has to be improved. Inaddition to internal intrinsic stabilisation of active materials, the durability of such solar cells hasalso to be ensured by protection barrier coating on their outer surfaces.The literature already establishes very interesting coatings made of plasma polymerizedmaterials, but these works are essentially performed for small areas and/or under industriallychallenging vacuum conditions. The Atmospheric Plasma Dielectric Barrier Discharge (APDBD)processing method that will be deployed in this project is very promising to make large scalecoatings on polymer substrates of interest, i.e. PET (Polyethylene Terephthalate) and PEN(Polyethylene Naphthalate). In this cold and very reactive medium, monomer precursors givebirth to thin polymer coatings. Such coatings will be designed to be high barrier against oxygenand water by the use of organosilicons and fluorocarbons sub-layers respectively. Inter-layersmade of acrylic monomers will be investigated in order to accommodate the expected surfaceenergy mismatch and inter(intra)-layers stresses. Moreover, as nano-clays can lead to greatbarrier efficiency while keeping transparency, in-situ incorporation of nano-clays within plasmapolymer will be investigated. A multi-layered and multi-functional architecture will thus bedeveloped to fulfil all the requirements of the application. The control of in-situ incorporation andof alternation of various nature layers are key features for the goals of this project.A comprehensive approach of the relationship between structure and properties will be the keyfor success. We expect that this project will allow deep understanding of physico-chemicalphenomena, relations between structure / architecture and properties. This would guaranteepeer reviewed publications and thus increase the visibility of Luxembourg on a hot topicresearch field.