Effect of Coating Properties on the Crystal Quality Near the Sidewalls of Multicrystalline Silicon Ingot

Reducing the defects and impurity contents at the edge of multicrystalline silicon (mc-Si) is an effective way for improving the performance of solar cells. In this work, the effect of nucleation coating based on Si powder with different particle size and thickness on crystal quality of ingot edge is investigated. The results show that a large particle nucleation coating is more helpful in generating small and uniform grains at the ingot sidewall, and it also reduces the width of the red zone due to the decrease of the concentration of metal and oxygen impurities. However, too thick nucleation coating would widen the red zone due to atmosphere contamination during melting, as confirmed by iron concentration distribution. The photoluminescence (PL) images demonstrated that small grains generated continuously at the ingot sidewall could significantly improve defect distribution. The solar cell efficiency of the edge wafers grown with large particle nucleation coating is increased by 0.07% compared to that of conventional edge wafers.