Overcoming the grain size limit to Voc in sustainable photovoltaics

基于硅片的太阳能发电是一种广泛使用的成熟技术。虽然由于中国的大规模生产而变得越来越便宜，但国际市场仍然受到政府补贴的推动。替代的“薄膜”材料是最好的竞争机会，但它们有三个问题：a）它们的电压低于预期，这是由于它们中的晶粒尺寸小（通常为百万分之几米），B）目前用于薄膜太阳能电池的材料含有稀有元素，随着PV工业在未来40年内扩大数百倍，这些稀有元素将造成供应问题，为了在全球市场上竞争，生产方法必须变得更便宜、更有效。我们将测试一种制造太阳能电池的新方法，这种方法有望克服所有这些限制。我们将研究典型的地球丰度半导体Cu_2ZnSn（S，Se）_4（CZTSS）。由它制成的太阳能电池面临着典型的问题：它的电压性能不佳，晶粒非常小。它也很难制造，因为它很容易失去硫和硒（最成功的研究实验室诉诸复杂的方法，涉及纳米颗粒和危险的还原溶剂）。几年来，CZTSS的效率一直限制在12%，这阻碍了CZTSS成为一种生产技术。在这个项目中，我们将测试一种替代方法来生长CZTSS。我们将探索在具有小颗粒的廉价金属片上生长大颗粒CZTSS的可能性-我们预计这可能成为可行的生产路线。我们将制作数百块太阳能电池来验证假设。总的来说，这个想法有可能将CZTSS的效率从12%提高到16%，甚至更高，从而为新的光伏产品开辟一条可行的道路。在这一领域的技术领先地位可能使英国有机会在不断扩大的全球光伏业务中夺回一部分份额。

Solar electricity based on wafer silicon is a mature technology that is in widespread use. Although it is getting cheaper due to mass production in China, the international market is still driven by government subsidies. Alternative 'thin film' materials are the best chance of competition, but they have three problems: a) their voltages are lower than expected due to the small size of the crystal grains in them (several millionths of a meter typically), b) the materials presently used for thin film solar cells contain rare elements that will pose supply issues as the PV industry expands by several hundred fold over the next 40 years, and c) production methods must become cheaper and more effective in order to compete in the global marketWe will test a new method to make solar cells that promises to overcome all of these limitations. We will work on the archetypal earth abundant semiconductor Cu2ZnSn(S,Se)4 (CZTSS). Solar cells made from it suffer from the typical problems: It underperforms on voltage and has very small crystal grains. It is also difficult to make since it is prone to lose sulphur and selenium (the most successful research labs resort to complex methods involving nanoparticles and dangerous reducing solvents). The efficiency has been limited to 12% for some years now, and this is preventing CZTSS from becoming a production technology.In this project we will test an alternative method to grow CZTSS. We will explore the possibility of growing large grains of CZTSS on cheap metal sheet with small grains -we expect this could become a workable production route. We will make some hundreds of solar cells to test the hypotheses.Overall the idea has the potential to increase the efficiency of CZTSS from 12% to 16%, or even higher, making it feasible to open up a pathway for new PV products. A technological lead in this area could give the UK the opportunity to grab back a share of the expanding global PV business.