Regensburg 2019 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 16: Organic Thin Films, Organic-Inorganic Interfaces
DS 16.1: Vortrag
Mittwoch, 3. April 2019, 09:30–09:45, H39
Visualising the Vertical Energetic Landscape in Organic Photovoltaics — •Vincent Lami1, Andreas Weu1, Jiangbin Zhang2, Yongsheng Chen3, Zhuping Fei4, Martin Heeney4, Richard Friend2, and Yana Vaynzof1 — 1KIP/CAM, Heidelberg University, GER — 2Cavendish Laboratory, University of Cambridge, UK — 3Nankai University, Tianjin, China — 4Chemistry & CPE, Imperial College London, UK
Energy level diagrams in organic photovoltaic (OPV) devices play a crucial role in interpretation of device physics, since they determine elementary processes such as charge generation, transport or extraction. Despite the importance of these diagrams, they are currently often constructed by combining energetic values of the individual device components, without taking into account interfacial effects, such as band bending or dipole formation. Herein, we demonstrate that combining ultra-violet photoemission spectroscopy (UPS) with gas cluster ion beam sputtering allows for a damage-free depth profiling and hence, an accurate determination of the vertical energetic landscape of active layers. First, we utilize a model photovoltaic system, then we demonstrate our method on other high efficiency fullerene and non-fullerene systems. We are not only able to accurately measure the highest occupied molecular orbital (HOMO) offset of the contributing materials and to quantify energy losses, but also to obtain compositional information with a very high vertical depth resolution. Finally, as UPS depth profiling can be performed at any point in device lifetime, it offers valuable information after device operation or degradation.