Thermal gradient influence of HEM multi-crystalline Si ingot

Performance of Multicrystalline ingots is affected by many properties, especially during the crystallizing process. Reducing the defects of ingots and improving the cell property are main stream pursuits for this field. For this study, three types of thermal gradient during crystallizing were tested to verify the properties of Multi-crystalline ingot. Reducing the thermal gradient can slow the growth rate with the ingot oxygen concentration and cell efficiency being the main impact on ingot performance. Current acceptable oxygen concentrations are below 10×10¹⁷ cm^-3, however the oxygen concentration at bottom of the ingot can be reduced to 2×10¹⁷ cm^-3 with a slow down in the growth rate. In addition, wafer efficiency can also increase 0.2% by setting up a small thermal gradient. Regarding cell properties, a small thermal gradient during solidification increased the performance of J_sc and V_oc.