We have studied how the increase of pressure in the deposition of polymorphous silicon can reduce the ion energy and the damage of the p-layer in p-i-n solar cells. By increasing the pressure during the deposition of the i-layer to 3 Torr, we have been able to increase the fill factor and the solar cell efficiency up to 8.4%. In an attempt to reduce the optical gap and increase further the deposition rate we have studied the use of He dilution. Changing the dilution from hydrogen to He leads to a higher deposition rate at lower rf power while keeping similar transport properties. Moreover, the lower hydrogen content of He diluted films results in a smaller band gap and a higher short circuit current in solar cells. Thus, silane-He mixtures allow to reduce the ion energy for a constant deposition rate and to minimize the damage at the p-layer and p/i interface. The cells show a fill factor of 0.69 V-oc, of 0.91 V, an initial efficiency of 9.3% on textured SnO2. (C) 2004 Elsevier B.V. All rights reserved.
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