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For hydrogenated amorphous silicon (a-Si:H) solar cells, the critical concentration of a given impurity defines the lowest concentration which causes a decay of solar cell efficiency. Values of 2-5 x 10(19) cm(-3) are commonly found for the critical oxygen concentration (C-O(crit)) of a-Si: H. Here we report a dependence of C-O(crit) on the contamination source. For state-of-the-art a-Si: H solar cells prepared at the same plasma deposition conditions, we obtain with a (controllable) chamber wall leak C-O(crit) similar to 2 x 10(19) cm(-3) while for a leak in the gas supply line a higher C-O(crit) of similar to 2 x 10(20) cm(-3) is measured. No such dependence is observed for nitrogen. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3357424]

Microcrystalline silicon carbide (mu c-SiC) films were prepared using hot wire chemical vapor deposition at low substrate temperature. The mu c-SiC films were employed as window layers in microcrystalline silicon (mu c-Si:H) n-i-p solar cells. Quantum efficiency (QE) and short circuit current density (J(SC)) in these n-side illuminated n-i-p cells were significantly higher than in standard p-i-n cells. A high QE current density of 26.7 mA/cm(2) was achieved in an absorber layer thickness of 2 mu m. The enhanced J(SC) was attributed to the wide band gap of the mu c-SiC layer and a sufficiently high hole drift mobility in mu c-Si:H absorber layer. (C) 2007 American Institute of Physics.