Very Thin Amorphous and Microcrystalline Silicon Films Deposited by Hot-Wire Chemical Vapour Deposition for Photovoltaic Applications

摘要

For thin-film silicon-based solar cell technology, very thin (5 - 20 nm) doped layers are prerequisite. In stacked cell structures, usually the top cell incorporates a very thin amorphous intrinsic layer (50 - 100 nm). In this paper, various aspects of fabricating these very thin films by Hot-Wire CVD are discussed: (ⅰ) the growth of very thin p-doped microcrystalline silicon (p-μc-Si:H) and amorphous silicon-carbon (a-SiC:H) films on different substrates: glass, TCO and amorphous silicon, (ⅱ) the properties and structural stability of these very thin p-doped films in device-like structures, (ⅲ) the thickness dependence of conductivity of n-doped amorphous silicon which shows bulk-like properties from a thickness of only 20 nm, if the deposition parameters are suitably chosen, (ⅳ) the incorporation of very thin p-μc-Si:H films into p-i-n and n-i-p solar cell devices entirely fabricated by Hot-Wire CVD with initial efficiencies up to η_(initial) = 7.8% and 6.2%, respectively, (ⅴ) the incorporation of very thin (43 nm) intrinsic amorphous layers into stacked cell (p-i-n-p-i-n) structures entirely fabricated by Hot-Wire CVD, where the top i-layer has to necessarily be very dense to withstand the roughening influence of the subsequent n-μc-Si:H deposition, reaching a maximum efficiency of η_(initial) = 7.0%, and (ⅵ) the fabrication of different n/p recombination or tunnel junctions for p-i-n-p-i-n tandem solar cells and their stability.