Implementation of faceted dendrite growth on floating cast method to realize high-quality multicrsytalline Si ingot for solar cells

We carried out small-scale crystal growth experiment to apply faceted dendrite growth at the top of the melt to floating cast method in order to grow high-quality multicrystalline Si (mc-Si) ingot for solar cells. By appropriate cooling at the initial stage, the most part of the top surface was covered by a single faceted dendrite crystal followed by directional solidification from the top to the bottom. As a consequence, the cross-section of the ingot was dominated by a single crystal grain. The crystal grain was found to be almost free from subgrain boundaries as evidenced by spatially resolved single-peak x-ray rocking curve profiles. The minority carrier diffusion length was found to be much longer than that in a control sample grown from the bottom to the top presumably due to the minimized contact with the crucible wall. This shows that the floating cast method combined with formation of faceted dendrite crystals at the initial stage is a promising route to realize high-quality mc-Si ingot for high-efficiency solar cells.