Numerical Investigation of Argon Gas Flow Patterns and Their Effects on Mc-Si Ingot Growth Process: Solar Cell Applications

Using the finite volume method, a directional solidification (DS) furnace used to grow a multi-crystalline silicon (mc-Si) ingot is numerically simulated in 2-dimensions. The impact of argon gas flow pattern on the melt-free surface (M-FS) was studied using transient global simulations of oxygen and carbon-dependent transport in laboratory-scale DS furnaces for solar cell applications. Argon gas flow (AGF) patterns over the M-FS affects the temperature of the upper part of the silicon melt. In the conventional furnace, AGF pattern is opposite to the growth direction. In a modified furnace system, argon gas is distributed through the melt vertical to the growth direction. In the modified furnace, during the crystallisation process, the evaporated SiO flux at the top of the M-FS reduces, resulting in a decrease in oxygen concentration in the grown ingot. A modified AGF pattern that inhibits the reaction between SiO gas and hot graphite material shows an exponential reduction of carbon concentration in the as-grown ingot. The conventional ingot obtained the oxygen and carbon concentrations within 6.61E17 and 9.04E16 atoms/cm3 respectively and the modified ingot obtained the oxygen and carbon impurity concentrations within 2.2E17 and 5.32E16 atoms/cm3, respectively. The modified AGF pattern improves the quality of mc-Si ingots for PV applications.