Transient thermal effects into a 155 kg POLIX ingot [for solar cells]

The POLIX process has been adapted to produce high quality and high capacity multicrystalline silicon ingots with large vertically oriented columnar grains for solar cell production. This paper describes the recently developed 155 kg ingot unidirectional solidification process conditions and also the main features of material characterization. Furthermore, after thermal studies based on heat flow motions, the relevant parameters have been optimized so that the solid-liquid interface is planar and its growth rate is quite constant. Determination of dislocation density is analysed in term of thermal analysis giving the temperature distribution in the ingot during the growth and in the last phase of crystallization and cooling.