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

光电子器件（如太阳能电池）中的降解机制要么是由于外部环境（如水随时间扩散到器件中），要么是由于材料（如吸收层或电极）的内在光降解。由于缺乏氧气和水的照明，这种内在的光降解不能通过智能设备架构或先进的封装策略来抑制。因此，测量和连续了解固有的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，允许加速评估光电子材料的光稳定性，特别是用于太阳能应用的薄膜半导体。由于目前的标准测试持续数月，我们的方法旨在通过使用聚光将光降解时间加快数百倍。该概念的新颖之处在于评估在集中照明和良好控制的温度下的降解动力学。在此过程中，深入了解了光电材料或器件的各种降解机制（在低照度下）。主要的技术挑战是在广泛的照明强度范围内保持对温度的精确控制。因此，我们将能够区分温度诱导降解和光诱导降解。据我们所知，我们还没有意识到试图将温度诱导降解过程与光电材料的光诱导降解分离开来的研究，并利用这一见解建立了一种方法，可以在最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，例如光学涂层，然而，由于研究者的背景和经验，我们将首先集中研究半导体。不同的材料，例如油漆、发色团膜、光谱选择性涂层或包装箔，可能会在后期进行测试。我们将进一步关注与太阳能应用相关的半导体，特别是与薄膜太阳能电池相关的材料。目前正在开发大量新颖、有前途的高性能薄膜半导体材料。近年来报道了数十万种有机半导体，然而，由于数量庞大且需要长时间进行寿命测试，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内在稳定性之间的相关性，需要一种允许在最短的测量时间（几天而不是几个月或几年）内研究新型半导体材料的内在光稳定性的方法。

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.