Characterisation of thin film CdSeTe/CdTe solar cells

薄膜CdsSeTe/CdTe光伏(PV)器件是2022年生产的最成功的第二代光伏技术，产量超过9GW。薄膜光伏的效率受到材料中原子级缺陷(晶界、平面缺陷、点缺陷等)的限制。高效率电池的制造通常需要某种形式的缺陷钝化处理。例如，在氯化镉中通过退火激活镉，用氯钝化晶界，用硒钝化颗粒内部，等等。最近在拉夫堡使用HRTEM进行的工作表明，沉积时的CdTe包含高密度的堆积缺陷，这些缺陷可以通过CdCl2激活过程去除。使用EBSD的研究表明，颗粒结构的随机化是重要的。阴极发光(CL)是一种强大的技术，它显示了缺陷、杂质或微结构如何影响纳米级的发光。拉夫堡正在开发CL的新能力，配备了扫描电子显微镜和新的专用STEM仪器。这个项目旨在确定原子级缺陷是如何降低电池效率的，以及支撑它们钝化的基本机制。将使用各种技术，包括电子显微镜和新的CL能力。合适的装置将在可再生能源系统技术中心(CREST)的光伏材料和设备小组中制造。我们还将与我们在国家可再生能源实验室(NREL)、斯旺西大学的长期合作伙伴以及行业合作伙伴合作。该项目将是与CTF Solar GmbH的特殊合作关系的一部分，CTF Solar GmbH将提供在其德国研发设施中制造的设备。

Thin film CdsSeTe/CdTe photovoltaic (PV) devices are the most successful second-generation technology with over 9GW produced in 2022. The efficiency of thin-film PV is limited by atomic-scale defects in the material (grain boundaries, planar defects, point defects etc). The manufacture of a high efficiency cell typically requires some form of defect passivation treatment. Examples include activation of CdTe by annealing in CdCl2, passivation of grain boundaries by chlorine, passivation of grain interiors by selenium etc.... Recent work at Loughborough using HRTEM has shown that as deposited CdTe contains high densities of stacking faults and that these are removed by the CdCl2 activation process. Work using EBSD has shown that randomisation of the grain structure is important. Cathodoluminescence (CL) is a powerful technique that shows how defects, impurities or microstructure can affect luminescence at the nanoscale. A new capability in CL is being developed at Loughborough with facilities on SEM and on a new dedicated STEM instrument. This project aims to determine how atomic-scale defects degrade cell efficiency and the fundamental mechanisms underpinning their passivation. A variety of techniques will be used including electron microscopy and the new CL capability. Suitable devices will be fabricated in the Photovoltaics Materials and Devices group in the Centre for Renewable Energy Systems Technology (CREST). We will also work with our long-term collaborators at the National Renewable Energy laboratory (NREL), Swansea University and with industrial partners. This project will be part of a special relationship with CTF Solar GmbH who will provide devices fabricated in their R&D facility in Germany.