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Impact of pre-fabrication treatments on n-type UMG wafers for 21% efficient silicon heterojunction solar cells
摘要： Silicon heterojunction solar cells achieve high conversion efficiency due to the excellent surface passivation provided by the hydrogenated intrinsic amorphous silicon films. However, they require a high-quality wafer as a starting material because their low-temperature processing does not allow for gettering. Czochralski-grown upgraded metallurgical-grade (UMG-Cz) silicon is a low-cost alternative to electronic-grade silicon for silicon solar cells, but is often limited in lifetime by grown-in defects. We have previously shown that pre-fabrication treatments, namely tabula rasa, phosphorus diffusion gettering, and hydrogenation, can significantly improve the bulk quality of UMG-Cz wafers. These help to mitigate the impact of grown-in oxygen precipitate nuclei and metallic impurities. In this work, we fabricate rear-junction silicon heterojunction solar cells on both as-grown and pre-treated UMG-Cz and electronic-grade wafers. We show that pre-fabrication treatments have a marked impact on solar cell efficiencies. With pre-fabrication treatment, the efficiency improves from 18.0% to 21.2% for the UMG-Cz cells and 21.2%–22.7% for the electronic-grade cells. Comparison of the open-circuit voltages of the as-grown and pre-treated UMG-Cz and electronic-grade cells using Quokka simulations reveals that the bulk lifetime remains the primary limiting factor for the UMG-Cz wafers.
关键词： Hydrogenation,Phosphorus diffusion gettering,Czochralski silicon,Solar-grade silicon,Tabula rasa,Silicon heterojunction solar cells
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Statistical analysis of structure loss in Czochralski silicon growth
摘要： In Czochralski monocrystalline silicon growth, structure loss (SL) is the loss of the mono-crystalline structure. It represents a significant loss of productivity. In this work, this phenomenon is investigated by statistical analysis of production data of roughly 14000 ingots produced over a year of time at NorSun factory in ?rdal, Norway. It is found that ingots with structure loss typically have lower heater power and temperature fluctuations than ingots without structure loss after four hours of body (ca. 240 mm). Particularly, ingots without manual adjustment by furnace operator have significantly higher frequency of structure loss than ingots for which the operator has increased the temperature one or more times. Most ingots with structure loss are also found to have a higher pull speed on average than ingots without structure loss, and that there is a threshold below which no ingots had structure loss. A binary logistic regression was used for classification of ingots with and without structure loss and 30% of the data was used to comparison of predictions of the model. Using only the standard deviation of the temperature fluctuations around a moving average provided a prediction accuracy of 99.6%, for ingots that have passed six hours of body (ca. 360 mm).
关键词： statistical analysis,structure loss,binary logistic regression,Czochralski silicon growth
更新于2025-09-11 14:15:04