@article{TaitReckwitzArvindetal.2021,
  author    = {Tait, Claudia E. and Reckwitz, Anna and Arvind, Malavika and Neher, Dieter and Bittl, Robert and Behrends, Jan},
  title     = {Spin-spin interactions and spin delocalisation in a doped organic semiconductor probed by EPR spectroscopy},
  series = {Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies},
  volume    = {23},
  journal   = {Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies},
  number    = {25},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d1cp02133h},
  pages     = {13827 -- 13841},
  year      = {2021},
  abstract  = {The enhancement and control of the electrical conductivity of organic semiconductors is fundamental for their use in optoelectronic applications and can be achieved by molecular doping, which introduces additional charge carriers through electron transfer between a dopant molecule and the organic semiconductor. Here, we use Electron Paramagnetic Resonance (EPR) spectroscopy to characterise the unpaired spins associated with the charges generated by molecular doping of the prototypical organic semiconductor poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) and tris(pentafluorophenyl)borane (BCF). The EPR results reveal the P3HT radical cation as the only paramagnetic species in BCF-doped P3HT films and show evidence for increased mobility of the detected spins at high doping concentrations as well as formation of antiferromagnetically coupled spin pairs leading to decreased spin concentrations at low temperatures. The EPR signature for F(4)TCNQ-doped P3HT is found to be determined by spin exchange between P3HT radical cations and F(4)TCNQ radical anions. Results from continuous-wave and pulse EPR measurements suggest the presence of the unpaired spin on P3HT in a multitude of environments, ranging from free P3HT radical cations with similar properties to those observed in BCF-doped P3HT, to pairs of dipolar and exchange-coupled spins on P3HT and the dopant anion. Characterisation of the proton hyperfine interactions by ENDOR allowed quantification of the extent of spin delocalisation and revealed reduced delocalisation in the F(4)TCNQ-doped P3HT films.},
  language  = {en}
}
@article{SchubertCollinsMangoldetal.2014,
  author    = {Schubert, Marcel and Collins, Brian A. and Mangold, Hannah and Howard, Ian A. and Schindler, Wolfram and Vandewal, Koen and Roland, Steffen and Behrends, Jan and Kraffert, Felix and Steyrleuthner, Robert and Chen, Zhihua and Fostiropoulos, Konstantinos and Bittl, Robert and Salleo, Alberto and Facchetti, Antonio and Laquai, Frederic and Ade, Harald W. and Neher, Dieter},
  title     = {Correlated donor/acceptor crystal orientation controls photocurrent generation in all-polymer solar cells},
  series = {Advanced functional materials},
  volume    = {24},
  journal   = {Advanced functional materials},
  number    = {26},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1616-301X},
  doi       = {10.1002/adfm.201304216},
  pages     = {4068 -- 4081},
  year      = {2014},
  abstract  = {New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all-polymer solar cells have struggled to keep up with the steadily increasing power conversion efficiency of polymer: fullerene cells. The lack of knowledge about the dominant recombination process as well as the missing concluding picture on the role of the semi-crystalline microstructure of conjugated polymers in the free charge carrier generation process impede a systematic optimization of all-polymer solar cells. These issues are examined by combining structural and photo-physical characterization on a series of poly(3-hexylthiophene) (donor) and P(NDI2OD-T2) (acceptor) blend devices. These experiments reveal that geminate recombination is the major loss channel for photo-excited charge carriers. Advanced X-ray and electron-based studies reveal the effect of chloronaphthalene co-solvent in reducing domain size, altering domain purity, and reorienting the acceptor polymer crystals to be coincident with those of the donor. This reorientation correlates well with the increased photocurrent from these devices. Thus, effi cient split-up of geminate pairs at polymer/polymer interfaces may necessitate correlated donor/acceptor crystal orientation, which represents an additional requirement compared to the isotropic fullerene acceptors.},
  language  = {en}
}
@article{KraffertSteyrleuthnerAlbrechtetal.2014,
  author    = {Kraffert, Felix and Steyrleuthner, Robert and Albrecht, Steve and Neher, Dieter and Scharber, Markus C. and Bittl, Robert and Behrends, Jan},
  title     = {Charge Separation in PCPDTBT : PCBM Blends from an EPR Perspective},
  series = {The journal of physical chemistry},
  volume    = {118},
  journal   = {The journal of physical chemistry},
  number    = {49},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/jp509650v},
  pages     = {28482 -- 28493},
  year      = {2014},
  language  = {en}
}
@article{HahnEngelhardReschkeetal.2015,
  author    = {Hahn, Aaron and Engelhard, Christopher and Reschke, Stefan and Teutloff, Christian and Bittl, Robert and Leimk{\"u}hler, Silke and Risse, Thomas},
  title     = {Structural Insights into the Incorporation of the Mo Cofactor into Sulfite Oxidase from Site-Directed Spin Labeling},
  series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  volume    = {54},
  journal   = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  number    = {40},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1433-7851},
  doi       = {10.1002/anie.201504772},
  pages     = {11865 -- 11869},
  year      = {2015},
  abstract  = {Mononuclear molybdoenzymes catalyze a broad range of redox reactions and are highly conserved in all kingdoms of life. This study addresses the question of how the Mo cofactor (Moco) is incorporated into the apo form of human sulfite oxidase (hSO) by using site-directed spin labeling to determine intramolecular distances in the nanometer range. Comparative measurements of the holo and apo forms of hSO enabled the localization of the corresponding structural changes, which are localized to a short loop (residues 263-273) of the Moco-containing domain. A flap-like movement of the loop provides access to the Moco binding-pocket in the apo form of the protein and explains the earlier studies on the in vitro reconstitution of apo-hSO with Moco. Remarkably, the loop motif can be found in a variety of structurally similar molybdoenzymes among various organisms, thus suggesting a common mechanism of Moco incorporation.},
  language  = {en}
}