| AVS 61st International Symposium & Exhibition | |
| Novel Trends in Synchrotron and FEL-Based Analysis Focus Topic | Tuesday Sessions |
| Session SA-TuP |
| Session: | Synchrotron Analysis Poster Session |
| Presenter: | Claudia Fleischmann, IMEC, Belgium |
| Authors: | C. Fleischmann, IMEC, Belgium P. Hönicke, Physikalisch-Technische Bundesanstalt (PTB), Germany M. Müller, Physikalisch-Technische Bundesanstalt (PTB), Germany B. Beckhoff, Physikalisch-Technische Bundesanstalt (PTB), Germany E. Voroshazi, IMEC, Belgium J. Tait, IMEC, Belgium T. Conard, IMEC, Belgium W. Vandervorst, IMEC, KU Leuven Belgium |
| Correspondent: | Click to Email |
While inorganic photovoltaic devices (PV) remain the main choice for large-scale energy production, organic photovoltaic devices (OPV) show great potential for future, environmentally friendly energy sources. Their semi-transparency, light-weight and unique opto-electrical properties combined with the possibility to shape OPV devices at will enable new applications where PV has never been used before. Similar to their inorganic counterparts, the underlying physical mechanisms and hence the performance and efficiency of organic devices is directly linked to their physicochemical properties. Revealing these properties is often very challenging due to the limited sensitivity and specificity of standard analytical techniques used for inorganic semiconductor characterization. In addition, it is highly desirable to probe the device structure as close as possible to a real one, which typically comprises organic-inorganic interfaces, intermixed phases being based on the same constituent atoms, or multilayer structures of a few tens to hundreds of nanometer thickness.
In this contribution we will examine the capabilities of Near-Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) for the chemical characterization of (complete) bulk-heterojunction OPV device structures based on conjugated polymers and fullerene derivatives including P3HT, PCDTBT, DPP and PCBM. We will show that the high chemical sensitivity of the carbon K-edge (~290eV) NEXAFS permits to distinguish between the common organic semiconductors in these devices, providing a tool for compositional analysis and miscibility studies. By using fluorescence yield detection the information depth is extended far beyond the surface, in contrast to electron yield detection, allowing to probe non-destructively the bulk properties of (buried) layers in the OPV structure. In this context, we will also illustrate the remaining metrology challenges and investigate the sensitivity of the sulfur and nitrogen K-edge NEXAFS to be used for degradation studies. Finally, we will discuss the stability of these organic materials under x-ray irradiation, which is particularly critical for synchrotron radiation-based methods.