On the Field Dependence of Free Charge Carrier Generation and Recombination in Blends of PCPDTBT/PC70BM: Influence of Solvent Additives.
We have applied time-delayed collection field (TDCF) and charge extraction by linearly increasing voltage (CELIV) to investigate the photogeneration, transport, and recombination of charge carriers in blends composed of PCPDTBT/PC70BM processed with and without the solvent additive diiodooctane. The results suggest that the solvent additive has severe impacts on the elementary processes involved in the photon to collected electron conversion in these blends. First, a pronounced field dependence of the free carrier generation is found for both blends, where the field dependence is stronger without the additive. Second, the fate of charge carriers in both blends can be described with a rather high bimolecular recombination coefficients, which increase with decreasing internal field. Third, the mobility is three to four times higher with the additive. Both blends show a negative field dependence of mobility, which we suggest to cause bias-dependent recombination coefficients.
†Institute of Physics and Astronomy, Soft Matter Physics, Universität Potsdam, D-14476 Potsdam, Germany.
Steve
S
Albrecht
‡Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany.
Wolfram
W
Schindler
†Institute of Physics and Astronomy, Soft Matter Physics, Universität Potsdam, D-14476 Potsdam, Germany.
Jona
J
Kurpiers
†Institute of Physics and Astronomy, Soft Matter Physics, Universität Potsdam, D-14476 Potsdam, Germany.
Juliane
J
Kniepert
†Institute of Physics and Astronomy, Soft Matter Physics, Universität Potsdam, D-14476 Potsdam, Germany.
James C
JC
Blakesley
§Macromolecular Chemistry and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Strasse 20, D-42097 Wuppertal, Germany.
Ines
I
Dumsch
§Macromolecular Chemistry and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Strasse 20, D-42097 Wuppertal, Germany.
Sybille
S
Allard
‡Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany.
Konstantinos
K
Fostiropoulos
§Macromolecular Chemistry and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Strasse 20, D-42097 Wuppertal, Germany.
Ullrich
U
Scherf
†Institute of Physics and Astronomy, Soft Matter Physics, Universität Potsdam, D-14476 Potsdam, Germany.
Dieter
D
Neher
PCPDTBT; bimolecular recombination; field-dependent generation; geminate recombination; low-band-gap polymers; polymer solar cells; solvent additive