The dislocation distribution characteristics of a multi-crystalline silicon ingot and its impact on the cell efficiency

The characteristics of dislocation distribution of a commercially produced multi-crystalline silicon ingot and its influence on cell performance were investigated. The dislocation of a multi-crystalline silicon ingot with a weight of 450kg was measured with the etch pits method. The measurement was made on bricks cut from the corner, the edge, as well as from the center of the ingot. It was found that the dislocation density increases from the bottom to the top and the dislocation density at the top section is at least three times higher than that of at the bottom, while the dislocation density of the corner brick is generally lower than that of the center brick at the same height. The potential influence of such characteristics of dislocation was further investigated through phosphorus gettering process. It was found that the improvement on minority lifetime through gettering is directly related to the dislocation density. The results indicated that the dislocation density is one of the key limiting factors for the performance of mc-Si wafer.