Effects and mechanisms of argon flow rate on the quality of cast multicrystalline silicon

Abstract

Cast multicrystalline silicon is a well-established crystal growth technique, widely utilized not only as a direct material for photovoltaic cells but also as an effective method for purifying low-purity silicon feedstock. This study, based on a mature industrial process for small-grain cast multicrystalline silicon, examines the impact of varying argon flow rates on material quality. Increasing the argon flow rate enhances heat transfer, reducing crystal growth time, and strengthens melt convection, which mitigates residual stress. Consequently, this reduces the concentration of detrimental defects, extends carrier recombination lifetime, and improves purification efficiency. Furthermore, a higher argon flow rate effectively lowers interstitial oxygen content in the cast silicon. However, excessively high flow rates may compromise the crucible coating, introducing additional contaminants and inclusions into the crystal.