@article{CastellaniSalzmannBugnonetal.2009,
  author    = {Castellani, Mauro and Salzmann, Ingo and Bugnon, Philippe and Yu, Shuwen and Oehzelt, Martin and Koch, Norbert},
  title     = {Structural and electronic implications for carrier injection into organic semiconductors},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-009-5336-6},
  year      = {2009},
  abstract  = {We report on the structural and electronic interface formation between ITO (indium-tin-oxide) and prototypical organic small molecular semiconductors, i.e., CuPc (copper phthalocyanine) and alpha-NPD (N,N'-di(naphtalen-1-yl)- N,N'-diphenyl-benzidine). In particular, the effects of in situ oxygen plasma pretreatment of the ITO surface on interface properties are examined in detail: Organic layer-thickness dependent Kelvin probe measurements revealed a good alignment of the ITO work function and the highest occupied electronic level of the organic material in all samples. In contrast, the electrical properties of hole-only and bipolar organic diodes depend strongly on the treatment of ITO prior to organic deposition. This dependence is more pronounced for diodes made of polycrystalline CuPc than for those of amorphous alpha-NPD layers. X-ray diffraction and atomic force microscopic (AFM) investigations of CuPc nucleation and growth evidenced a more pronounced texture of the polycrystalline film structure on the ITO substrate that was oxygen plasma treated prior to organic layer deposition. These findings suggest that the anisotropic electrical properties of CuPc crystallites, and their orientation with respect to the substrate, strongly affect the charge carrier injection and transport properties at the anode interface.},
  language  = {en}
}
@article{LuBlakesleyHimmelbergeretal.2013,
  author    = {Lu, Guanghao and Blakesley, James C. and Himmelberger, Scott and Pingel, Patrick and Frisch, Johannes and Lieberwirth, Ingo and Salzmann, Ingo and Oehzelt, Martin and Di Pietro, Riccardo and Salleo, Alberto and Koch, Norbert and Neher, Dieter},
  title     = {Moderate doping leads to high performance of semiconductor/insulator polymer blend transistors},
  series = {Nature Communications},
  volume    = {4},
  journal   = {Nature Communications},
  number    = {1-2},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/ncomms2587},
  pages     = {8},
  year      = {2013},
  abstract  = {Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt\% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60.},
  language  = {en}
}
@article{SalzmannHeimelDuhmetal.2012,
  author    = {Salzmann, Ingo and Heimel, Georg and Duhm, Steffen and Oehzelt, Martin and Pingel, Patrick and George, Benjamin M. and Schnegg, Alexander and Lips, Klaus and Blum, Ralf-Peter and Vollmer, Antje and Koch, Norbert},
  title     = {Intermolecular hybridization governs molecular electrical doping},
  series = {Physical review letters},
  volume    = {108},
  journal   = {Physical review letters},
  number    = {3},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.108.035502},
  pages     = {5},
  year      = {2012},
  abstract  = {Current models for molecular electrical doping of organic semiconductors are found to be at odds with other well-established concepts in that field, like polaron formation. Addressing these inconsistencies for prototypical systems, we present experimental and theoretical evidence for intermolecular hybridization of organic semiconductor and dopant frontier molecular orbitals. Common doping-related observations are attributed to this phenomenon, and controlling the degree of hybridization emerges as a strategy for overcoming the present limitations in the yield of doping-induced charge carriers.},
  language  = {en}
}