Defect mitigation in silicon
Crystalline silicon (c-Si) is the material of which a growing >85% of industrial solar cells are manufactured. The performance of c-Si devices has historically been limited by metallic impurities, especially iron, which can degrade solar-cell performance by several percent absolute. Complex cost and performance trade-offs govern solar-cell manufacturing, making impurity management a persistent challenge in PV manufacturing.
Innovations: The PVLab contributed to a body of literature that today assists iron mitigation during solar-cell manufacturing. Among our specific contributions, we developed and/or applied: (i) nanofocused X-ray mapping techniques to measure the distribution of precipitated iron in modern industrial c-Si materials; (ii) simulation tools to predict the evolution of fast-diffusing iron impurities during solar-cell processing; and (iii) novel annealing treatments to mitigate iron during solar-cell processing, resulting in yield, throughput, and performance enhancements at industrial partners. Key challenges we faced include improving the detection limit of synchrotron techniques to measure iron in modern c-Si materials, which are orders of magnitude more pure than those made a decade ago. This work did not occur in a vacuum; we benefit from a worldwide network of collaborators who contribute complementary techniques, simulations, industry interactions, and perspectives.
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