Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 58: Focus Session: Structure and Transport in Organic Photovoltaics III (jointly with CPP)

HL 58.5: Vortrag

Mittwoch, 28. März 2012, 16:00–16:15, ER 270

Charge Carrier Dynamics in Blends of PCPDTBT/PC₇₀BM: Influence of Solvent Additives — •Steve Albrecht¹, Wolfram Schindler², Jona Kurpiers¹, Sybille Allard³, Ullrich Scherf³, and Dieter Neher¹ — ¹Universität Potsdam, Institute of Physics and Astronomy, Soft Matter Physics, D-14476 Potsdam, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany — ³Bergische Universität Wuppertal, Macromolecular Chemistry and Institute for Polymer Technology, Gauss-Strasse 20, D-42097 Wuppertal, Germany

We have applied time delayed collection field (TDCF) and photo-CELIV to investigate the photogeneration, recombination dynamics and transport of charge carriers in blends composed of PCPDTBT:PC₇₀BM processed with and without the solvent additive diiodooctane. We show that the solvent additive affects several elementary processes involved in the photon to electron conversion in these blends. First, there is a pronounced field dependence of the generation of free carriers for both blends, with the field dependence being more pronounced without the additive. Second and most important, addition of diiodooctane leads to a three-fold increase of the carrier mobility, enabling rapid extraction of the charge in competition with bimolecular recombination. On the other hand, both blends show rather high but similar bimolecular recombination coefficients. All together, the improvement in generation and extraction of the free carriers explains well the twofold increase in device efficiency upon addition of the processing agent.