Crystal growth, microstructure characterization and cell performance analysis of casting-monocrystalline ingots with <111> orientation

Casting mono-crystalline technology, or also called quasi-monocrystalline technology, is regarded as a promising approach to fabricate low cost but high quality wafers. Although very high efficiency can be obtained with cells fabricated from wafers located at the bottom to middle position of the ingot, the defect density increases quickly as the ingot grows due to defect multiplication. In this paper, the defect multiplication is controlled by changing the seed orientation from <;100> to <;111>. The defect density is decreased on a large scale from the bottom to the top along the crystal growth direction. Especially at the top of the ingot, the defect density is much lower than that of <;100> orientation. The performance of the cells fabricated using <;111> oriented casting mono wafers does not show, however, significant improvement compared to the <;100> oriented wafers. The possible reasons are discussed.