Research on Resistivity Control Strategy for the Preparation of Crystalline Silicon Ingots Using Recycled Silicon Materials

In this work, we studied the resistivity calculation and control strategies for recycled silicon materials co-doped with multiple impurity elements. The resistivity distribution and performance of silicon ingots produced using two approaches: batching doping calculation based on measured resistivity values versus that incorporating the resistivity contributions of individual impurity elements were analyzed and compared. The results demonstrated that: when the measured resistivity values were used in batching doping calculation, there was a large deviation between the actual resistivity of the silicon ingot and the theoretically calculated resistivity. This led to a high risk of out-of-control resistivity in the ingredient formulation, which affects the product qualification rate and electrical performance. In contrast, by controlling the resistivity values of various impurity elements for batching doping calculation of recycled silicon materials, the resistivity of the silicon ingot was generally close to the theoretically calculated value. Both the product qualification rate and electrical performance were comparable to those of conventional silicon ingots. Therefore, this method can effectively reduce the material cost of polycrystalline silicon feedstocks. In addition, the recycling of silicon materials is beneficial to environmental protection.