Modeling and optimization of the feedstock melting for industrial photovoltaic multi-crystalline silicon ingot

A transient global model of industrial furnace of seed-assisted directional solidification is built and it can reproduce basically the feedstock melting process. Thermal field, velocity field and silicon phase transition are investigated in the numerical furnace with and without a back plate. Simulation result shows that insulation of the plate will lower the possibility of second contamination resulted by circulation flow outside gas hole and flatten surface of seed crystals. Experiment measurements show that deflection of seed crystals in modified furnace with the plate is 2 mm, which is lower about 3 mm than that in original furnace without the plate. The casting experiment also confirms that the ingot quality by adding the plate is improved with 0.13 μs and 2.14% gain on average minority carrier lifetime and effective minority carrier lifetime yield, respectively.