VHF PECVD microcrystalline silicon: from material to solar cells

Intrinsic microcrystalline silicon has been deposited by very high frequency plasma enhanced chemical vapor deposition technique at two different frequencies, 90 and 100 MHz. Different gas mixtures of silane and hydrogen were utilized, while keeping the substrate temperature at 220 °C and the chamber pressure at 950 mTorr. In particular, the effect of plasma power has been investigated at both frequencies in the range 20–60 W. The material was characterized in terms of structural, electrical and optical properties. Optimised material was inserted in p-i-n solar cells. Since the properties of the p-layers (∼150 Å) strongly affect the solar cell performance, a particular care was directed to the structural and electrical characterization of this material. Preliminary results on the devices are presented: efficiency of approximately 3.8% was reached for 1-μm-thick solar cells.