Very thin amorphous and microcrystal line silicon films deposited by hot-wire chemical vapour deposition for photovoltaic applications

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 ot-Wire CVD are discussed: (i) the growth of very thin p-doped microcrystalline silicon (p-muc-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 run, if the deposition parameters are suitably chosen, (iv) the incorporation of very thin p-muc-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 eta(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-muc-Si:H deposition, reaching a maximum efficiency of eta(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.