Defect control based on constitutional supercooling effect in cast multicrystalline silicon: Boron-indium co-doping

The impact of constitutional supercooling (CS) on the grain structure of cast multicrystalline silicon (mc-Si) materials was investigated. Indium impurity was chosen as the CS dopant because of its low equilibrium segregation coefficient so that CS effect could be obtained at relatively low doping concentration. Industrial indium (In) doped G2 and boron-indium (B–In) co-doped G5 seed-assisted multicrystalline silicon (mc-Si) ingots were fabricated and characterized. Self-nucleated grains and epitaxial grains could be obtained, respectively, as the result of tuning the doping amount of indium. Constitutional-supercooling-related defects (CSD) were found in the co-doped ingot and could suppress the growth and propagation of dislocation-type defects. As a result, the overall deleterious defect density of B–In co-doped mc-Si wafers was well reduced compared to that of referential B-doped wafers, and the average solar cell performance of B–In co-doped ingots was obviously enhanced.