Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 41: Crystallization, Nucleation, Self Assembly II (joint session CPP/DY, organized by CPP)
CPP 41.5: Vortrag
Mittwoch, 9. März 2016, 17:30–17:45, H42
Revealing Structure Formation in conjugated polymers such as PCPDTBT by Optical Spectroscopy — •Anna Köhler1, Christina Scharsich1, Florian Fischer2, Kevin Wilma3, Fabian Panzer1, Richard Hildner3, and Sabine Ludwigs2 — 1Experimental Physics II, University of Bayreuth, Bayreuth, Germany — 2IPOC-Functional Polymers, University of Stuttgart, Stuttgart , Germany — 3Experimental Physics IV, University of Bayreuth, Bayreuth, Germany
There is increasing evidence that the performance of conjugated polymers in organic solar cells is strongly affected by the presence of small crystallites or aggregates. However, short-range order is difficult to detect using structural techniques. Here, we show that optical spectroscopy can be employed to reveal the presence of short-range ordered structured as well as their formation mechanism. We present a comprehensive study of the optical properties as a function of temperature for PCPDTBT in solution and in thin films with two distinct morphologies.[1] Using absorption and photoluminescence spectroscopy as well as Franck-Condon analyses, we show that PCPDTBT in solution undergoes a phase transition (critical temperature: 300 K) from a disordered to a truly aggregated state upon cooling. Comparison is made to the formation of aggregtes in P3HT.[2] The saturation value of aggregates in solution is reached in PCPDTBT thin films at any temperature. In addition, we demonstrate that a low percentage of thermally activated excimer states is present in the films at temperatures above 200 K.