We present a simulation tool that predicts solar cell efficiency based on iron content in as-grown wafer and solar cell processing conditions. This “impurity-to-efficiency” (I2E) simulation tool consists of three serial components, which are independently and jointly validated using published experimental results: (1) a kinetic model that calculates changes in the distribution of iron and phosphorus atoms during annealing; (2) an electronic model that predicts depth-dependent minority carrier lifetime based on iron distribution; and (3) a device simulator that predicts solar cell performance based on the minority carrier lifetime distribution throughout the wafer and the device architecture. The I2E model is demonstrated to be an effective predictor of cell performance for both single-crystalline and multi-crystalline silicon solar cells. We demonstrate the process optimization potential for the I2E simulator by analyzing efficiency improvements obtained using low-temperature annealing, a processing concept that has been successfully applied to achieve higher solar cell efficiencies on Fe-contaminated materials. Copyright © 2010 John Wiley & Sons, Ltd.