An innovative method for accelerated photo-stability testing of novel thin film semiconductors for solar cell applications

诸如太阳能电池之类的光电子学中的退化机制要么是由于外部环境，例如随着时间的推移水扩散到器件中，要么是由于诸如吸收层或电极之类的材料的本征光降解。由于在没有氧气和水的情况下照明，这种固有的光降解无法通过智能设备架构或先进的封装策略来抑制。因此，测量和连续了解本征退化过程是进一步提高太阳能系统寿命和可靠性的关键。在这个项目中，我们希望建立一种新的方法，能够加速评估光电材料，特别是用于太阳能应用的薄膜半导体的光稳定性。我们的方法的目标是通过使用聚光将光降解时间加快数百倍，因为目前的标准测试持续几个月。这一概念的新颖之处在于评估了在集中光照和良好控制的温度下的降解动力学。通过这样做，可以深入了解光电材料或器件的各种退化机制(在低照度下)。主要的技术挑战是在大范围的照明强度下保持对温度的精确控制。因此，我们将能够区分温度诱导的降解和光诱导的降解。就我们所知，我们还没有意识到试图将光电材料的温度诱导降解过程和光诱导降解过程分开的研究，并利用对这些过程的洞察来建立一种方法，允许在尽可能短的时间内预测光电材料的最大固有寿命。所提出的方法当然会与光电子学以外的领域相关，如光学涂层，但由于研究人员的背景和经验，我们将把第一批研究集中在半导体上。不同的材料，如涂料、发色团薄膜、光谱选择涂层或包装膜，可能会在稍后阶段进行测试。我们将进一步将工作重点放在与太阳能应用相关的半导体上，特别是与薄膜太阳能电池相关的材料上。目前正在开发大量新型的、有前途的、高性能的薄膜半导体材料。近年来，人们报道了几十万种有机半导体，然而，由于有机半导体的数量巨大，寿命测试需要很长的时间，因此其固有的稳定性在很大程度上是未知的。为了建立半导体结构与其本征稳定性之间的关联，需要一种方法，能够在尽可能短的测量时间内研究新型半导体材料的本征光稳定性，而不是几天而不是几个月或几年。

Degradation mechanisms in optoelectronics such as solar cells occur either due to outer circumstances, e. g. water diffusion into the device over time, or due to intrinsic photo-degradation of the materials such as the absorber layer or electrodes. This intrinsic photo-degradation, due to illumination in the absence of oxygen and water, cannot be suppressed by smart device architectures or advanced packaging strategies. Measuring and successive understanding of the intrinsic degradation processes is, accordingly, a key for further increasing lifetime and reliability of solar systems.Within this project, we want to establish a novel method allowing the accelerated assessment of the photo-stability of optoelectronic materials and in particular of thin film semiconductors for solar applications. Our approach targets to speed up the photo-degradation time by a factor of several hundreds by using concentrated light, since current standard tests last several months. The novelty of the concept is to assess the degradation kinetics under concentrated illumination and well controlled temperature. In doing so, deep insight is gained into the various degradation mechanisms (under low illumination) of the optoelectronic materials or devices. The main technical challenge is to maintain precise control on the temperature for a wide range of illumination intensities. Accordingly, we will be able to separate temperature induced degradation from photo-induced degradation.To the best of our knowledge we are not aware of investigations trying to separate temperature induced degradation processes from photo-induced degradation of optoelectronic materials and use this insight into the processes to establish a method allowing to predict the maximal inherent lifetime of optoelectronic material in the shortest possible time. The proposed method certainly will have relevance to fields other than optoelectronics, such as optical coatings, however, due the background and experience of the investigator we will concentrate our first studies to semiconductors. Different materials, for example paints, chromophore films, spectral selective coatings or packaging foils, may be tested at a later stage.We will further focus our work on semiconductors with relevance for solar applications and, in particular, on materials related to thin film solar cells. A vast amount of novel promising, high performance thin film semiconductor materials is currently developed. Several hundreds of thousands of organic semiconductors were reported in the recent years, however, due to this huge number and long time periods required for lifetime testing, their inherent stability is largely unknown. A method allowing to investigate the intrinsic photo-stability of novel semiconducting materials in the shortest possible measurement time, days instead of months or years, is required in order to build correlations between the structure of the semiconductor and its intrinsic stability.