In the medium to long-term future, PV should play an important role as a renewable energy source for the production of clean electricity in Western Balkan Countries (WBC). Such large-scale implementation of PV requires at least drastic reduction of prices of PV systems to more competitive levels. Production of PV modules and systems in WBCs facilitates low cost PV production with the additional benefit of local development of innovative and clean technologies. This project aims at lower cost price per Wat tpeak (Wp) for film-Si PV produced in a local production plant in WBC by a significant upgrade of the cell and module efficiency, while keeping the production costs per m² almost constant.The increase of cell efficiency will be achieved in several sequenti al steps. 1)improvement of TCO layers (better stability in hydrogen plasma, better transparency) 2)introduction of doped micro-crystalline Si layers as window layers (less optical losses) 3)introduction of intrinsic micro-crystalline Si layers as active la yers (no light induced degradation,improved light absorption) 4)integration of previous steps leading to the introduction of a-Si/mc-Si tandem cell concept (enlarge effective absorption spectrum). Steps 1) and 2) will be performed using existing industrial production tools of Participant 4. Scientific support and analysis of the deposited layers will be provided by Participants 2, 3, and 5. Step 3) will be performed by applying MW-PECVD on lab scale at Participant 1 with assistance of Participant 7. Analysi s of the layers will take place by Participant 6. In parallel, Participant 7 will make a design for an industrial scale MW-PECVD system, suitable for this application. Step 4 will be a joint action of all participants involved. This procedure should lead to a concept for an opgraded production such that the existing module efficiency (5 %) can be increased to 8 %. This will result in decrese of production costs towards less than 2 Euro/Wp.