Efficiency improvement of a-Si solar cells deposited in a single chamber, large area, PECVD reactor

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 cm(2) 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 cm(2)) with an initial efficiency of 8.5% has been manufactured.