Description of Ribbon Growth Techniques

To understand the potential of the different photovoltaic silicon ribbon technologies, a closer look at the wafer growth technology, wafer characteristics and behaviour in the cell process are all necessary. 

In the past, the different ribbon Si technologies were classified in several ways  

In an ideal silicon ribbon growth technology, the wafer characteristics are completely determined by the way the crystallisation heat (latent heat of fusion) is extracted. 

Obviously, the circumstances during crystal growth have a major impact on the crystal structure and on the chemical, electrical and mechanical properties of the silicon ribbon. Silicon-melt preparation and especially the dissolution of impurities from the crucible material and the wafer cooling procedure are also crucial. 

This will be demonstrated for three typical examples representing the most important silicon ribbon growth processes the edge-defined film-fed growth and the string ribbon process where the crystallisation interface moves in line with the ribbon transport direction as typical representatives of type I, and the ribbon growth on substrate technique where the liquid-solid interface moves almost perpendicular to the ribbon transport direction as type II process. 

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