Influence of the total gas flow on the deposition of microcrystalline silicon solar cells

In this paper we study the influence of total gas flow on solar cell performance and deposition rate of microcrystalline silicon solar cells prepared by plasma enhanced chemical vapor deposition at 13.56-MHz excitation frequency. By changing the total gas flow the transition between amorphous and microcrystalline growth can be systematically varied. Over a wide range of total gas flows, solar cell efficiencies between 7 and 9% could be realized. The cells at low total gas flows were prepared at increased silane concentrations and reduced hydrogen flows. The results are interpreted in terms of gas utilization and gas residence time in the plasma space. Furthermore, a new technique for the deposition of pc-Si:H is described which produces muc-Si:H suitable for high efficiency solar cells with only very low hydrogen supply. The best solar cell prepared by this method had an efficiency of 7.3%. (C) 2003 Elsevier B.V. All rights reserved.