Growth of Multicrystalline Silicon for Solar Cells: Dendritic Cast Method

Abstract

This chapter introduces the dendritic cast method which allows us to obtain multicrystalline silicon ingot containing large-size crystal grains with specific orientations. The growth of dendrite crystals along the bottom wall of crucible in the initial stage of casting is crucial in this method. First, the features of Si dendrite crystals including the conditions for initiating dendrite growth will be explained following the concept of the dendritic cast method. The parallel twin formation and undercooling, those are prerequisites for the growth of the dendrite crystal, will be considered fundamentally. Next, experimental results of the growth of multicrystalline silicon ingots by the dendritic cast method will be summarized. The idea to control the dendrite growth will be described. Finally, problems and the future development of this method will be considered. A nonwetting dendritic cast method, which is a growth concept for the reduction of generation of dislocation and impurity during casting, will be introduced.