Gettering of impurities in silicon: delivering quantitative understanding to improve photovoltaics

去除硅中的杂质：提供定量理解以改进光伏发电

• 批准号: EP/J01768X/1
• 负责人: John Murphy
• 金额: $ 11.41万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ01768X%2F1
• 关键词: Gettering; impurities; silicon; delivering; quantitative

Photovoltaics have the potential to supply all the world's energy needs. The market for photovoltaics is dominated by cells made from crystalline silicon, which account for more than 80% of today's production. Whilst other technologies are being researched, silicon's abundance, chemical stability, density, band gap and non-toxic nature mean that is certain to play a leading role in at least the medium term. More than half of bulk silicon solar cells are fabricated from multicrystalline silicon (mc-Si) wafers. Although mc-Si photovoltaics have lower efficiencies than their single-crystal counterparts, their substantially lower production costs means the technologies have equal commercial viability at present. Mc-Si is produced by casting, often using a low grade feedstock, and is consequently packed with extended defects (dislocations, grain boundaries and precipitates) and transition metal impurity point defects. Recombination of photogenerated charge carriers at such defects is a major reason for the reduced efficiency of mc-Si cells. Gettering processes are routinely used either to redistribute the defects or remove them from the material. However, such processes are not completely effective. One of the major reasons for this is that the interaction between defects prevents them being gettered. This project aims to further the fundamental understanding of defect interactions in mc-Si. The thermodynamics of interactions between transition metals (particularly iron) and extended defects (particularly dislocations and oxide precipitates) will be studied experimentally. Passivation of key extended defects will also be investigated. The fundamental knowledge obtained should allow the development of new or modified gettering processes with the ultimate aim of facilitating the use of dirtier (hence cheaper) feedstocks for silicon photovoltaics.

光伏发电有潜力满足世界所有的能源需求。光伏市场由晶硅制成的电池主导，占当今产量的80%以上。虽然其他技术正在研究中，但硅的丰度、化学稳定性、密度、带隙和无毒性质意味着，至少在中期内，这肯定会发挥主导作用。超过一半的体硅太阳能电池是由多晶硅(MC-Si)晶片制成的。尽管MC-Si光伏的效率低于单晶光伏，但其显著较低的生产成本意味着，目前这些技术具有同等的商业可行性。MC-Si是通过铸造生产的，通常使用低品位的原料，因此充满了扩展的缺陷(位错、晶界和沉淀物)和过渡金属杂质点缺陷。光生载流子在这些缺陷处的复合是MC-Si电池效率降低的主要原因。吸气工艺通常用于重新分布缺陷或将其从材料中去除。然而，这样的过程并不完全有效。其中一个主要原因是缺陷之间的相互作用防止了它们被吸走。本项目旨在加深对MC-Si中缺陷相互作用的基本了解。我们将通过实验研究过渡金属(特别是铁)和扩展缺陷(特别是位错和氧化物沉淀)之间相互作用的热力学。还将研究关键扩展缺陷的钝化。所获得的基本知识应允许开发新的或改进的吸气工艺，最终目的是促进使用更脏(因此更便宜)的硅光伏原料。

项目成果

(Invited) The Impact of Oxide Precipitates on Minority Carrier Lifetime in Czochralski Silicon

（特邀）直拉硅中氧化物沉淀对少数载流子寿命的影响

• DOI: 10.1149/05005.0137ecst
• 发表时间: 2013
• 期刊: ECS Transactions
• 作者: Murphy J