Towards optimized nucleation control in multicrystalline silicon ingot for solar cells

Abstract

Single layer silicon beads (SLSB) and chunks (SLSC) coated with silicon nitride were used as seed layer to grow high-quality multicrystalline silicon (mc-Si) ingots. The mc-Si ingots were grown using various sizes of the Si beads and chunks in the range of <1mm up to 4mm as seed layer. Grain size, grain orientation and grain boundary density were analyzed over ingot heights. It was found that SLSB and SLSC seeded mc- Si wafers have uniform small grains, more randomly orientated grains and high density of random grain boundary in comparison to the conventional mc-Si wafers. The density of dislocation cluster was significantly lower in SLSB and SLSC seeded mc-Si wafers than conventional mc-Si wafers. The reason responsible for dislocation clusters reduction in SLSB and SLSC seeded mc-Si wafers was discussed on the basis of the difference in the grain size and density of random grain boundary. However, density of dislocation cluster was slightly high in SLSC seeded mc-Si wafers than SLSB seeded mc-Si wafers. The indentation effects and irregular shape of Si chunks to cause inhomogeneous stress that may account for dislocation generation and/or multiplication in SLSC mc-Si wafers.