Growth and Solar Cell Aspects in Relation to Polycrystalline Silicon Ribbons Grown by the RAD Process

Summary

It is reported on the present status of a three-year programme initiated in June 1980 about polycrystalline silicon ribbons achieved by the RAD growth process. This presentation covers all the aspects of the study including those which do not explicitly pertain to the CEC contract n° ESC-R-022 F.

The results are presented according to the main research areas which relate to the carbon ribbon, growth and solar cell aspects. A carbon ribbon structure was chosen in January 82. It is shown that, although the specifications pertinent to this structure were individually met, the delayed optimization of this structure slowed down the growth programme. With respect to the carbon ribbon drawbacks, the solar cell back-contact problem was obviated by a burn-off step after growth which yields self-sustained silicon layers.

Continuous growth was demonstrated on the single-ribbon puller over lengths up to 30 m at a pulling rate of 10 cm.mn⁻¹. The thickness of each opposite silicon layer thus obtained can be made larger than the minimal value necessary to prevent the formation of cracks of thermoelastic origin.

The AM1 conversion efficiencies η of solar cells are in the 9–11% range. Comprehensive studies indicate that η values in the 11 to 13% may be envisaged.

Finally, the major goals of this three-year programme should be reached on schedule by July 1983.