@article{PingelNeher2013,
  author    = {Pingel, P. and Neher, Dieter},
  title     = {Comprehensive picture of p-type doping of P3HT with the molecular acceptor F(4)TCNQ},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {87},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {11},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1098-0121},
  doi       = {10.1103/PhysRevB.87.115209},
  pages     = {9},
  year      = {2013},
  abstract  = {By means of optical spectroscopy, Kelvin probe, and conductivity measurements, we study the p-type doping of the donor polymer poly(3-hexylthiophene), P3HT, with the molecular acceptor tetrafluorotetracyanoquin-odimethane, F(4)TCNQ, covering a broad range of molar doping ratios from the ppm to the percent regime. Thorough quantitative analysis of the specific near-infrared absorption bands of ionized F(4)TCNQ reveals that almost every F(4)TCNQ dopant undergoes integer charge transfer with a P3HT site. However, only about 5\% of these charge carrier pairs are found to dissociate and contribute a free hole for electrical conduction. The nonlinear behavior of the conductivity on doping ratio is rationalized by a numerical mobility model that accounts for the broadening of the energetic distribution of transport sites by the Coulomb potentials of ionized F(4)TCNQ dopants. DOI: 10.1103/PhysRevB.87.115209},
  language  = {en}
}
@article{PingelSchwarzlNeher2012,
  author    = {Pingel, P. and Schwarzl, R. and Neher, Dieter},
  title     = {Effect of molecular p-doping on hole density and mobility in poly(3-hexylthiophene)},
  series = {Applied physics letters},
  volume    = {100},
  journal   = {Applied physics letters},
  number    = {14},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.3701729},
  pages     = {3},
  year      = {2012},
  abstract  = {Employing impedance spectroscopy, we have studied the hole density, conductivity, and mobility of poly(3-hexylthiophene), P3HT, doped with the strong molecular acceptor tetrafluorotetracyanoquinodimethane, F(4)TCNQ. We find that the hole density increases linearly with the F(4)TCNQ concentration. Furthermore, the hole mobility is decreased upon doping at low-to-medium doping level, which is rationalized by an analytic model of carrier mobility in doped organic semiconductors [V. I. Arkhipov, E. V. Emelianova, P. Heremans, and H. Bassler, Phys. Rev. B 72, 235202 (2005)]. We infer that the presence of ionized F(4)TCNQ molecules in the P3HT layer increases energetic disorder, which diminishes the carrier mobility.},
  language  = {en}
}