Energy level alignment at interfaces in organic photovoltaic devices

• Published in: Journal of electron spectroscopy and related phenomena Vol. 190; pp. 12 - 24
• Main Authors: Opitz, Andreas, Frisch, Johannes, Schlesinger, Raphael, Wilke, Andreas, Koch, Norbert
• Format: Journal Article
• Language: English; French; German
• Published: 01-10-2013
• Subjects: Alignment; Devices; Electrodes; Electronic structure; Energy levels; Multilayers; Photovoltaic cells; Solar cells
• ISSN: 0368-2048
• DOI: 10.1016/j.elspec.2012.11.008

The alignment of energy levels at interfaces in organic photovoltaic devices is crucial for their energy conversion efficiency. Photoelectron spectroscopy (PES) is a well-established and widely used technique for determining the electronic structure of materials; at the same time PES measurements of conjugated organic materials often pose significant challenges, such as obtaining sufficiently defined sample structures and radiation-induced damage of the organic layers. Here we report how these challenges can be tackled to unravel the energy levels at interfaces in organic photovoltaic devices, i.e., electrode/organic and organic/organic interfaces. The electronic structure across entire photovoltaic multilayer devices can thus be reconciled. Finally, general considerations for correlating the electronic structure and the photovoltaic performance of devices will be discussed.