Atom Probe Characterisation of Individual Dislocations in Multi-Crystalline Silicon

在对环境影响最小的情况下生产低成本、可靠的电力是人类未来面临的最大挑战之一。太阳能是最清洁、最丰富的能源，因此，将光转化为电能的光伏设备很可能是克服这一挑战的主要部分。多晶硅(MC-Si)太阳能电池目前占全球太阳能生产市场的60%左右，由于原材料中的杂质，其性能有限。它们的效率在很大程度上依赖于对杂质分布(吸气)的控制和对材料中存在的缺陷的有效氢钝化。然而，吸气和钝化过程并不是完全有效的，其原因也不是很清楚。该项目由原子探测小组和半导体和硅光伏小组共同完成，将使用先进的聚焦离子束和原子探测断层扫描技术，对电学性质已得到很好表征的单个位错进行“逐个原子”分析。要使用的技术是最近才开发出来的，是牛津大学材料系独有的。该项目的结果将是更好地了解限制MC-Si太阳能电池效率的问题，并有可能导致性能设备的改进。特别是，将阐明缺陷类型、存在的杂质原子和商业电池吸除和钝化过程后的电活性之间的关系。将在细胞处理的不同阶段测量缺陷的电活动，以便识别与位错活动有关的处理中的关键参数。该项目与MC-Si制造商CrystaloxPV和牛津仪器公司合作，为该项目提供专用的电子束感应电流(EBIC)系统，以表征特定微结构特征的电活动。该项目还将用于评估牛津半导体集团正在开发的新型氢钝化和吸气技术的有效性。这项研究还将为EPSRC资助的多机构SuperSilicon PV：扩展材料性能的限制项目做出贡献。它直接促进了EPSRCs的一些战略研究领域，特别是能源专题和可再生能源分专题。

The production of low-cost and reliable electricity with minimal environmental impact is one of the biggest challenges for the future of humanity. Solar power is the cleanest and most abundant source of energy, and as such photovoltaic devices that convert light to electricity will likely be a major part of overcoming that challenge. Multicrystalline silicon (mc-Si) solar cells, which currently represent around 60% of the world market for solar energy production, have limited performance due to the impurities in the raw material. Their efficiency is heavily dependent on control of the impurity distribution (gettering) and effective hydrogen passivation of defects present in the material. However, the gettering and passivation processes are not completely effective and the reasons for this are not well understood. This project which is based both in the Atom Probe Group and Semiconductor and Silicon Photovoltaics Group will used advanced FIB (focused ion beam) and APT (atom probe tomography) techniques to perform "atom by atom" analyses on individual dislocations whose electrical properties have been well characterised. The techniques to be used have only been very recently developed and are unique to the Materials Department at Oxford. The result of this project will be a better understanding of the problems that limit the efficiency of mc-Si solar cells and potentially it will result in improved performance devices. In particular, the correlation between defect type, impurity atoms present, and electrical activity after commercial cell gettering and passivation processes will be elucidated. Measurements of the electrical activity of defects will be made at different stages in cell processing so that key parameters in the processing with regard to dislocation activity can be identified. The project is in collaboration with the mc-Si manufacturer CrystaloxPV and Oxford Instruments who are supplying a dedicated Electron Beam Induced Current (EBIC) system for use with the project to characterise electrical activity of specific microstructural features. The project will be also used to assess the efficacy of novel hydrogen passivation and gettering techniques being developed in the Oxford Semiconductor Group. The research will also contribute to the EPSRC-funded multi-institutional SuperSilicon PV: extending the limits of material performance project. It contributes directly to some of EPSRCs strategic research areas in particular the Energy theme and the Renewable Energy sub-theme.