Compositional and electronic inhomogeneities in printed non-fullerene solar cells andtheir effect on device performance and stability

印刷有机光伏提供了生产廉价、大面积和灵活产品的可能性，但在将其整合到工业应用之前，仍需解决某些挑战。其中一个挑战与大面积形成均匀、均匀的薄膜的困难有关。不均匀性的存在会影响印刷设备的功能、性能及其稳定性。在这个项目中，我们将用空间和能量分辨光电子能谱(PES)来研究印刷有机太阳能电池中组成和电子不均匀的形成。通过使用PES成像或PES映射，可以获得大范围的空间分辨信息，分别提供1um和100um的分辨率。这些长度标尺与不均匀性的研究高度相关，并使表征大样本(在厘米长度标尺上)成为可能。通过将光谱表征与气体团簇离子束的温和刻蚀相结合，实现了分辨率为1-2纳米的垂直分辨率测量，从而提供了基本上无损伤的有机材料刻蚀。这两种方法可以组合在一起，以跟踪在器件有源层不同深度的大面积上材料的组成和电子结构的演变。这些方法将使我们能够表征成分和电子不均匀作为横向尺寸和深度的函数。我们将与研究单位Popular的其他合作伙伴一起揭示这些不均匀如何影响设备性能，特别是对稳定性的影响。在本项目中将详细研究后者，以阐明在制造过程中形成的不均匀的存在如何导致退化，或者，均匀印刷层的老化如何导致不均匀的形成。

Printed organic photovoltaics offer the possibility to produce inexpensive, large area and flexible products, yet certain challenges still need to be addressed prior to its integration in industrial applications. One of these challenges is related to the difficulty of forming uniform, homogeneous films over large areas. The presence of inhomogeneities will affect the function and performance of the printed devices as well as its stability. In this project, we will investigate the formation of compositional and electronic inhomogeneities in printed organic solar cells by spatially and energetically resolved photoemission spectroscopy (PES). Spatially resolved information across large areas can be obtained by using PES imaging or PES mapping, offering a resolution of 1 and 100 um, respectively. These length scales are highly relevant to the study of inhomogeneities and make it possible to characterise large samples (on a cm length scale). Vertically resolved measurements with a resolution of 1–2 nm are made possible by coupling the spectroscopic characterisation with gentle etching by a gas cluster ion beam, which offers an essentially damage-free etching of organic materials. The two methods can be combined in order to track the evolution of the composition and electronic structure of materials across large areas at various depths of the device active layer. These methods will enable us to characterise both compositional and electronic inhomogeneities as a function of lateral dimensions and depth. Together with other partners of the Research Unit POPULAR we will reveal how these inhomogeneities impact on the device performance, and in particular on the stability. The latter will be examined in detail in this project in order to elucidate how the presence of inhomogeneities formed during fabrication can lead to degradation, and alternatively, how the ageing of homogeneous printed layers can lead to the formation of inhomogeneities.