In order to realize large area integrated a-Si modules using a commercial, single chamber, PECVD reactor, an accurate optimization of deposition process for p-i-n solar cell has been performed leading to a 1 cm2 device efficiency value of 10.3%. Besides the efficiency improvements achieved by the insertion of a graded layer at p/i interface and by the introduction of SnO2 Asahi type U substrate, an 'interface cleaning procedure', based on NF3 flushing step, was the key for the cells Voc and fill factor increase. Microcrystalline n+ layer, ZnO/Ag back contact and device thermal annealing gave further contributions to the cell efficiency. Utilizing this technology, a large area p-i-n modules (900 cm2) with an initial efficiency of 8.5% has been manufactured.