Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 42: Functional Materials I

MM 42.3: Talk

Thursday, March 17, 2011, 18:15–18:30, IFW B

Study of the degradation of conjugated polymers using scanning probe microscopy — •Esha Sengupta, Anna L. Domanski, Stefan A.L. Weber, Maria B. Retschke, Hans Jürgen Butt, and Rüdiger Berger — Max Planck Institute for Polymer Research, Mainz, Germany

A major problem for applications of conjugated polymers in organic photovoltaics is their limited life-time [1]. Degradation occurs when these are exposed to sunlight, oxygen and water. Recent studies have reported changes in the open circuit voltage (Voc) and short circuit current (Jsc) in fabricated organic solar cells as estimates of degradation [2]. However, in these studies, device fabrication and optimization of the processing steps are time consuming. Since the morphology of organic solar cells needs to be controlled on a nanometer scale due to small exciton pathways, Scanning Probe Microscopy (SPM) provides a valuable tool to study topographic and electronic effects. Here, we present an SPM based method to study degradation of conjugated polymers without the need to fabricate devices. Changes in the surface potential and conductivity due to degradation of the active layer of solar cells were investigated using Kelvin Potential Microscopy (KPM) and conductive Scanning Force Microscopy (c-SFM). These changes have been related to the Voc and Jsc changes upon degradation. We expose the active layer directly to simulated sunlight and varying amounts of oxygen and humidity while partially covering it with a grid. [1] Krebs, F.C. et al., Chemistry of Materials, 2005, 17, 5235 [2] Seemann, A., et al., Organic Electronics, 2009, 10, 1424.