Silicon ingot casting by gas assisted solidification

Abstract

Gas Assisted Solidification (GAS) is a casting method to provide low cost silicon materials for the fabrication of solar cells. In this paper, a detailed study on the mode of solidification is made according to the operational variables. The most appropriate soaking temperature is about 40 °C above the melting point of silicon, with an optimum soaking period of 4.5 hr. A slow temperature decreasing rate of about 1–2 °C/min is to ensure the formation of large grains. A triggering time of gas flow close to the end of the soaking period is most desirable. With a steep increment of gas flow rate, a large gas flow rate of about 300 1/min in the steady state period is to set for the conditions of growing elongated grains. The grown ingots were subjected to chemical and physical characterization, and some preliminary data will also be presented for their correlation.