Controlling dislocation gliding and propagation in quasi-single crystalline silicon by using -oriented seeds

Abstract

Dislocations originating from the seed junctions are the most harmful defects in quasi-single crystalline silicon (QSC-Si). In traditional <100>-oriented QSC-Si ingots, dislocations easily develop into cascade shape, or even further form sub-grain boundaries as the ingot grows. In this paper, we have developed a novel <110>-oriented QSC-Si ingot to control the gliding and propagation of dislocations. It is found that the cascade shape is absent and dislocations only aggregate in the {100}/{100} boundary planes of <110>-oriented seeds, revealed by the minority carrier lifetime mapping and photoluminescence image. Accordingly, the internal quantum efficiency of <110>-oriented QSC-Si solar cells is obviously higher than that of the traditional <100>-oriented ones. Nevertheless, it should be noticed that the average photoelectric conversion efficiency of <110>-oriented QSC-Si solar cells could be 0.6% lower than that of traditional ones if the {100}/{100} boundary is included in the solar cell, due to a higher reverse leakage current. This problem can be involved by enlarging the size of seed crystals or adopting better seed arrangement. These results provide a new promising method for the development of high quality QSC-Si in photovoltaic industry.