Improving quality of cast monocrystalline Si ingot with seed crystal strips and graphite soft felt

Abstract

A combination of the two techniques, one that employs seed crystal strips and the other that makes use of graphite soft felts have been proposed and studied to improve the casting process of monocrystalline Si (mono-Si) ingots. The evolution of the melting process of Si seed crystals and the growth of edge Si muliticrystals during the cast of mono-Si ingot has been investigated in detail. The results of the study indicated that these two changes increased the proportion of full mono-Si wafers substantially and led to a considerable reduction in the average dislocation ratio of edge Si bricks based on cast mono-Si ingot. Solar cell devices fabricated based on cast mono-Si ingot with the above two improvement measures exhibited enhancement in their overall photoelectric conversion efficiency (η) by 0.29% and 0.64% (absolute value), in comparison to the solar cells based on mono-Si ingot that was cast using only the seed crystal strips and the conventional ingot, respectively. Therefore, the study provides sufficient evidence that utilization of seed crystal strips and graphite soft felts in combination with each other as supplementary measures to the casting process of mono-Si ingot can be scaled up to be used in the photovoltaic production line for the development of solar cells with higher performance.