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Proceedings Paper

The influence of doping on the performance of organic bulk heterojunction solar cells
Author(s): Markus Glatthaar; Nicola Mingirulli; Birger Zimmermann; Florian Clement; Moritz Riede; Bas van der Wiel; Michael Niggemann; Andreas Gombert
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Paper Abstract

We investigated organic bulk-heterojunction solar cells based on an absorber blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) by electrical impedance spectroscopy (EIS). A strong neck in the modulus plot of the EIS-spectra indicates that the absorber is divided into two regions of different conductivities. A similar behaviour was observed for pure P3HT-diodes. Hence, it can be concluded that the PCBM:P3HT absorber is pdoped by impurities of P3HT, so that a Schottky-like contact with aluminium is formed. It is known from literature, that annealing of PCBM:P3HT solar cells leads to drastic improvement of the photovoltaic performance. We compared the current-voltage characteristics and impedance spectra before and after consecutive annealing steps. After the annealing an expansion of the depletion region was observed, indicating that volatile dopants were evaporated out of the absorber. This contributes to an improved photovoltaic performance as the separation of the generated charges in the depletion region is more efficient than in the non-depleted region. Also an improved rectification behaviour might be caused by a lower doping level.

Paper Details

Date Published: 20 April 2006
PDF: 6 pages
Proc. SPIE 6192, Organic Optoelectronics and Photonics II, 61921V (20 April 2006); doi: 10.1117/12.662695
Show Author Affiliations
Markus Glatthaar, Freiburger Materialforschungszentrum (Germany)
Nicola Mingirulli, Fraunhofer Institut Solare Energiesysteme (Germany)
Birger Zimmermann, Freiburger Materialforschungszentrum (Germany)
Florian Clement, Fraunhofer Institut Solare Energiesysteme (Germany)
Moritz Riede, Freiburger Materialforschungszentrum (Germany)
Bas van der Wiel, Fraunhofer Institut Solare Energiesysteme (Germany)
Michael Niggemann, Freiburger Materialforschungszentrum (Germany)
Fraunhofer Institut Solare Energiesysteme (Germany)
Andreas Gombert, Fraunhofer Institut Solare Energiesysteme (Germany)

Published in SPIE Proceedings Vol. 6192:
Organic Optoelectronics and Photonics II
Paul L. Heremans; Michele Muccini; Eric A. Meulenkamp, Editor(s)

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