@article{AlbrechtSchindlerKurpiersetal.2012,
  author    = {Albrecht, Steve and Schindler, Wolfram and Kurpiers, Jona and Kniepert, Juliane and Blakesley, James C. and Dumsch, Ines and Allard, Sybille and Fostiropoulos, Konstantinos and Scherf, Ullrich and Neher, Dieter},
  title     = {On the field dependence of free charge carrier generation and recombination in blends of PCPDTBT/PC70BM influence of solvent additives},
  series = {The journal of physical chemistry letters},
  volume    = {3},
  journal   = {The journal of physical chemistry letters},
  number    = {5},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/jz3000849},
  pages     = {640 -- 645},
  year      = {2012},
  abstract  = {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.},
  language  = {en}
}
@article{AlbrechtTumblestonJanietzetal.2014,
  author    = {Albrecht, Steve and Tumbleston, John R. and Janietz, Silvia and Dumsch, Ines and Allard, Sybille and Scherf, Ullrich and Ade, Harald W. and Neher, Dieter},
  title     = {Quantifying charge extraction in organic solar cells: The case of fluorinated PCPDTBT},
  series = {The journal of physical chemistry letters},
  volume    = {5},
  journal   = {The journal of physical chemistry letters},
  number    = {7},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/jz500457b},
  pages     = {1131 -- 1138},
  year      = {2014},
  abstract  = {We introduce a new and simple method to quantify the effective extraction mobility in organic solar cells at low electric fields and charge carrier densities comparable to operation conditions under one sun illumination. By comparing steady-state carrier densities at constant illumination intensity and under open-circuit conditions, the gradient of the quasi-Fermi potential driving the current is estimated as a function of external bias and charge density. These properties are then related to the respective steady-state current to determine the effective extraction mobility. The new technique is applied to different derivatives of the well-known low-band-gap polymer PCPDTBT blended with PC70BM. We show that the slower average extraction due to lower mobility accounts for the moderate fill factor when solar cells are fabricated with mono- or difluorinated PCPDTBT. This lower extraction competes with improved generation and reduced nongeminate recombination, rendering the monofluorinated derivative the most efficient donor polymer.},
  language  = {en}
}