Efficiency Enhancement of Silicon Photovoltaic Solar Cells by Passivation

通过钝化提高硅光伏太阳能电池的效率

• 批准号: EP/K006975/1
• 负责人: Bruce Hamilton
• 金额: $ 65.87万
• 依托单位: University of Manchester
• 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%2FK006975%2F1
• 关键词: Efficiency; Enhancement; Silicon; Photovoltaic; Solar

Increasing energy demands, exhaustion of easily accessible oil resources and fears of climate change make renewable energy sources a necessity. Although it is evident that future power generation will result from a wide mix of technologies, photovoltaic cells have made astounding technical and commercial progress in recent years. Over the last decade renewable energy generation has been stimulated by tax concessions and feed-in tariffs. Large scale manufacturing of photovoltaics has benefited from this and progress along the learning curve necessary to achieve economies of scale in manufacture has been very rapid. However like all renewable energy sources today the cost per kWh of electricity from photovoltaics is greater than that generated by fossil fuels, although the gap has reduced quite dramatically in the last two years. The cost reductions in generation from photovoltaics have been achieved through innovative cell design, the use of lower cost materials, advances in power management electronics and lower profit margins. At the moment, >85% of new installations use wafered silicon cells of multi-crystalline or single crystal material. In these cases a key issue has been developing technologies which use thinner slices (using less silicon for a given area of solar panel) and moving to "solar grade" silicon. This type of silicon is less pure than the electronic grade used for integrated circuits and is cast into multi-crystalline ingots but it is very much cheaper. This is an important issues because before these developments as much as 50% of the cost of a cell could be attributed to the silicon material. An important cost reduction per kWh delivered has been achieved in this way despite solar grade silicon producing cells of lower conversion efficiency than electronic grade material. Further substantial reductions in cost could be achieved by using silicon produced by less energy hungry metallurgical processes, for example starting the manufacturing process by the reduction of quartz with carbon and applying low energy purification processes. This type of silicon, known as upgraded metallurgical silicon, is even less pure containing compensated dopants and metals which can act as important recombination centres so reducing the efficiency further. The aim of this proposal is to develop methodologies which are able to bring the efficiency of cells made from these cheap forms of silicon close to the efficiencies achieved from the higher cost electronic grade material. This could increase the efficiency of multi-crystalline solar grade silicon by around 5% absolute and even more in the case of upgraded metallurgical silicon. Current silicon cell structures work well because hydrogen (usually from the silicon nitride antireflection layer) passivates surfaces and bulk defects. In electronic grade single crystal this reduces recombination to insignificant levels. It doesn't work as well in solar grade multi-crystalline silicon or upgraded metallurgical silicon because there are regions, sometimes entire crystal grains, which are not passivated by the hydrogen. However other regions are of very high quality often as good as electronic grade silicon. We associate the resistance to passivation with specific types of defect observed in lifetime maps of slices. In this project we plan to identify the defects which show resistance to hydrogen passivation by using electronic and chemical techniques (carrier lifetime, Laplace deep level transient spectroscopy, SIMS, Raman spectroscopy and defect modeling). The key part of the proposal is to use our knowledge of defect reactions in silicon to develop alternative passivation chemistries which can be applied, during slice or cell production, to those defect species resistant to hydrogen passivation. In this way we would expect to make a very important improvement to the efficiency of the dominant solar PV technology.

不断增长的能源需求、容易获得的石油资源的枯竭以及对气候变化的担忧使得可再生能源成为必要。虽然很明显，未来的发电将来自广泛的技术组合，但近年来光伏电池在技术和商业上取得了惊人的进展。在过去十年中，税收优惠和上网电价刺激了可再生能源发电。大规模的光致发光材料的制造已经从中受益，并且在制造中实现规模经济所必需的学习曲线的进展沿着非常迅速。然而，像今天所有的可再生能源一样，来自光化学的每千瓦时电力的成本大于由化石燃料产生的成本，尽管差距在过去两年中已经相当显著地减小。通过创新的电池设计、使用低成本材料、电力管理电子技术的进步和较低的利润率，已经实现了光电池发电成本的降低。目前，超过85%的新装置使用多晶或单晶材料的晶片硅电池。在这些情况下，一个关键问题是开发使用更薄切片的技术（在给定的太阳能电池板面积上使用更少的硅），并转向“太阳能级”硅。这种硅的纯度低于用于集成电路的电子级，并被铸造成多晶锭，但它非常便宜。这是一个重要的问题，因为在这些开发之前，电池成本的50%可能归因于硅材料。尽管太阳能级硅生产的电池的转换效率低于电子级材料，但以这种方式实现了每千瓦时交付的成本的重要降低。成本的进一步大幅降低可以通过使用由能耗较低的冶金工艺生产的硅来实现，例如通过用碳还原石英并应用低能耗纯化工艺来开始制造工艺。这种类型的硅，称为升级冶金硅，纯度甚至更低，含有补偿掺杂剂和金属，这些掺杂剂和金属可以充当重要的复合中心，从而进一步降低效率。该提议的目的是开发能够使由这些廉价形式的硅制成的电池的效率接近由较高成本的电子级材料实现的效率的方法。这可以将多晶硅太阳能级硅的效率提高约5%的绝对值，在升级的冶金硅的情况下甚至更多。目前的硅电池结构工作良好，因为氢（通常来自氮化硅氮化物层）钝化表面和体缺陷。在电子级单晶中，这将复合减少到微不足道的水平。它在太阳能级多晶硅或升级的冶金硅中不起作用，因为有些区域，有时是整个晶粒，没有被氢钝化。然而，其他区域具有非常高的质量，通常与电子级硅一样好。我们将钝化阻力与切片寿命图中观察到的特定类型缺陷联系起来。在这个项目中，我们计划通过使用电子和化学技术（载流子寿命，拉普拉斯深能级瞬态光谱，西姆斯，拉曼光谱和缺陷建模）来识别显示抗氢钝化的缺陷。该提案的关键部分是利用我们对硅中缺陷反应的了解来开发替代钝化化学品，这些钝化化学品可以在切片或电池生产期间应用于那些耐氢钝化的缺陷物种。通过这种方式，我们有望对占主导地位的太阳能光伏技术的效率做出非常重要的改进。

项目成果

Passivation of titanium by hydrogen in silicon

硅中的氢使钛钝化

• DOI: 10.1063/1.4822329
• 发表时间: 2013
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Leonard S

Donor levels of the divacancy-oxygen defect in silicon

• DOI: 10.1063/1.4837995
• 发表时间: 2014-01
• 期刊: Journal of Applied Physics
• 影响因子: 3.2
• 作者: V. Markevich;A. Peaker;B. Hamilton;S. Lastovskii;L. Murin

Evidence for an iron-hydrogen complex in p-type silicon

p型硅中存在铁氢络合物的证据

• DOI: 10.1063/1.4927323
• 发表时间: 2015
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Leonard S

Recombination centers resulting from reactions of hydrogen and oxygen in n-type Czochralski silicon

n 型直拉硅中氢和氧反应产生的复合中心

• DOI: 10.1109/pvsc.2016.7749689
• 发表时间: 2016
• 作者: Markevich V

Titanium in silicon: Lattice positions and electronic properties

• DOI: 10.1063/1.4871702
• 发表时间: 2014-04-14
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Markevich, V. P.;Leonard, S.;Coutinho, J.
• 通讯作者: Coutinho, J.