Characterisation of high-performance photovoltaic materials for space applications using a correlative cathodoluminescence/photoluminescence spectrosc

在空间光伏应用的背景下，高性能一词包括几种材料特性。光电器件的一个关键要求，也是将许多期望的材料特性联系在一起的一个关键要求是高效率。卫星的电源供应是可能的任务目标的限制因素，通常也决定了它们的寿命。因此，需要能够制造高效率设备的材料，不仅在生命之初，而且在恶劣的空间条件下也能保持，这推动了这个项目的研究。该项目将探索这一高效率问题的两个方面，即提高寿命开始时的效率以及执行任务时性能的可持续性。它的目标是通过使用阴极发光和光致发光光谱方法来表征材料，这将提高我们对材料的光学和电学性质的理解，并为我们提供对材料或器件结构进行重要改进的信息。目前空间电源系统的行业标准是晶圆上III-V多结技术。在这个项目中，我们将为另一种高效率概念开发材料：热载流子太阳能电池。这种新兴的设备概念可以在薄、相对简单和热力学优雅的设计中实现高效率。我们将利用发光技术研究半导体和量子约束结构中的热载流子，包括它们的热化和提取。在热化机理的阻滞方面的进展，加上热载流子萃取效率的提高，可能会导致一种新的、根本不同的光伏电池，其效率超过Shockley-Queisser极限。我们还将解决这些材料中的辐射损伤的挑战，这是空间光伏电池性能下降的主要原因。碰撞辐射在吸收剂中引入缺陷，这些缺陷作为光生成载流子的非辐射重组位点，因此导致设备效率和性能下降。上述确定的实验技术可用于有效地研究缺陷部位。计划的相关方法，以及在阴极发光和光致发光光谱中进行时间分辨测量的能力，可能为研究新型器件结构中的缺陷及其影响提供新的见解。

In the context of photovoltaics for space applications, the term high-performance encompasses several material properties. A key requirement for the photovoltaic devices and one that ties together many of the desired material properties is that of high efficiency. The power supply to satellites is the limiting factor in the possible mission objectives and usually also determines their lifetime. It is therefore the need for materials that enable the fabrication of high efficiency devices, not only at the beginning of life, but also maintained despite the harsh conditions of space, that drives the research of this project.The project will explore two sides of this high efficiency problem, improvement of both efficiency at beginning of life as well as sustainability of on-mission performance. It will aim to do so through characterization of materials using cathodoluminescence and photoluminescence spectroscopy methods, which will improve our understanding of the optical and electrical properties of materials and give us the information to make vital improvements to materials or device structures.The current industry standard for space power systems is an on-wafer III-V multi-junction technology. In this project we will develop materials for an alternative high efficiency concept: the hot-carrier solar cell. This emerging device concept could enable high efficiency in a thin, comparatively simple and thermodynamically elegant design. We will use luminescence techniques to study hot carriers in semiconductors and quantum confined structures, including their thermalization and extraction. Advances in retardation of thermalization mechanisms coupled with improved efficiency of extraction of hot carriers could lead to a new, fundamentally different class of photovoltaics, with efficiencies beyond the Shockley-Queisser limit.We will also address the challenge of radiation damage in these materials which is the main cause of performance deterioration for space photovoltaics. Impinging radiation introduces defects in the absorber, which act as non-radiative recombination sites for photogenerated carriers and therefore lead to a decrease in device-efficiency and therefore performance. The experimental techniques identified above can be used to effectively study defect sites. The planned correlative approach, together with capacity for time-resolved measurements in both cathodoluminescence and photoluminescence spectroscopy may provide new insight on defects and their effects in novel device structures.