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Ordering of PCDTBT revealed by time-resolved electron paramagnetic resonance spectroscopy of its triplet excitons

: Biskup, T.; Sommer, M.; Rein, S.; Meyer, D.L.; Kohlstädt, M.; Würfel, U.; Weber, S.


Angewandte Chemie. International edition 54 (2015), No.26, pp.7707-7710
ISSN: 1433-7851
ISSN: 0044-8249
ISSN: 0570-0833
ISSN: 1521-3773
Journal Article
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Farbstoff; Organische und Neuartige Solarzellen; Organische Solarzellen; paramagnetic resonance; semiconductors; PCDTBT; photovoltaics

Time-resolved electron paramagnetic resonance (TREPR) spectroscopy is shown to be a powerful tool to characterize triplet excitons of conjugated polymers. The resulting spectra are highly sensitive to the orientation of the molecule. In thin films cast on PET film, the molecules’ orientation with respect to the surface plane can be determined, providing access to sample morphology on a microscopic scale. Surprisingly, the conjugated polymer investigated here, a promising material for organic photovoltaics, exhibits ordering even in bulk samples. Orientation effects may significantly influence the efficiency of solar cells, thus rendering proper control of sample morphology highly important.