@article{FreydankJanietzSchulz1998,
  author    = {Freydank, Anke-Christine and Janietz, Silvia and Schulz, Burkhard},
  title     = {Synthesis and electrochemical behaviour of Amphiphilic 1,3,4-Oxadiazole derivatives},
  year      = {1998},
  language  = {en}
}
@article{SchulzKnochenhauerBrehmeretal.1995,
  author    = {Schulz, Burkhard and Knochenhauer, Gerald and Brehmer, Ludwig and Janietz, Silvia},
  title     = {Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s},
  year      = {1995},
  language  = {en}
}
@article{SchulzKnochenhauerBrehmeretal.1994,
  author    = {Schulz, Burkhard and Knochenhauer, Gerald and Brehmer, Ludwig and Janietz, Silvia},
  title     = {Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s},
  year      = {1994},
  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}
}
@article{KurpiersFerronRolandetal.2018,
  author    = {Kurpiers, Jona and Ferron, Thomas and Roland, Steffen and Jakoby, Marius and Thiede, Tobias and Jaiser, Frank and Albrecht, Steve and Janietz, Silvia and Collins, Brian A. and Howard, Ian A. and Neher, Dieter},
  title     = {Probing the pathways of free charge generation in organic bulk heterojunction solar cells},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-018-04386-3},
  pages     = {11},
  year      = {2018},
  abstract  = {The fact that organic solar cells perform efficiently despite the low dielectric constant of most photoactive blends initiated a long-standing debate regarding the dominant pathways of free charge formation. Here, we address this issue through the accurate measurement of the activation energy for free charge photogeneration over a wide range of photon energy, using the method of time-delayed collection field. For our prototypical low bandgap polymer:fullerene blends, we find that neither the temperature nor the field dependence of free charge generation depend on the excitation energy, ruling out an appreciable contribution to free charge generation though hot carrier pathways. On the other hand, activation energies are on the order of the room temperature thermal energy for all studied blends. We conclude that charge generation in such devices proceeds through thermalized charge transfer states, and that thermal energy is sufficient to separate most of these states into free charges.},
  language  = {en}
}
@article{SchulzJanietz1995,
  author    = {Schulz, Burkhard and Janietz, Silvia},
  title     = {Preparation and characterization of thin films containing aromatic poly(1,3,4- oxadiazole)s},
  year      = {1995},
  language  = {en}
}
@article{ZellmeierBrennerJanietzetal.2018,
  author    = {Zellmeier, M. and Brenner, Thomas J. K. and Janietz, Silvia and Nickel, N. H. and Rappich, J.},
  title     = {Polythiophenes as emitter layers for crystalline silicon solar cells},
  series = {Journal of applied physics},
  volume    = {123},
  journal   = {Journal of applied physics},
  number    = {3},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-8979},
  doi       = {10.1063/1.5006625},
  pages     = {5},
  year      = {2018},
  abstract  = {We investigated the influence of the emitter (amorphous-Si, a-Si, or polythiophene derivatives: poly(3-hexylthiophene), P3HT, and poly(3-[3,6-dioxaheptyl]-thiophene), P3DOT) and the interface passivation (intrinsic a-Si or SiOX and methyl groups or SiOX) on the c-Si based 1 × 1 cm2 planar hybrid heterojunction solar cell parameters. We observed higher short circuit currents for the P3HT or P3DOT/c-Si solar cells than those obtained for a-Si/c-Si devices, independent of the interface passivation. The obtained VOC of 659 mV for the P3DOT/SiOX/c-Si heterojunction solar cell with hydrophilic 3,6-dioxaheptyl side chains is among the highest reported for c-Si/polythiophene devices. The maximum power conversion efficiency, PCE, was 11\% for the P3DOT/SiOX/c-Si heterojunction solar cell. Additionally, our wafer lifetime measurements reveal a field effect passivation in the wafer induced by the polythiophenes when deposited on c-Si.},
  language  = {en}
}
@article{PingelArvindKoellnetal.2016,
  author    = {Pingel, Patrick and Arvind, Malavika and K{\"o}lln, Lisa and Steyrleuthner, Robert and Kraffert, Felix and Behrends, Jan and Janietz, Silvia and Neher, Dieter},
  title     = {p-Type Doping of Poly(3-hexylthiophene) with the Strong Lewis Acid Tris(pentafluorophenyl)borane},
  series = {Advanced electronic materials},
  volume    = {2},
  journal   = {Advanced electronic materials},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {2199-160X},
  doi       = {10.1002/aelm.201600204},
  pages     = {7},
  year      = {2016},
  abstract  = {State-of-the-art p-type doping of organic semiconductors is usually achieved by employing strong -electron acceptors, a prominent example being tetrafluorotetracyanoquinodimethane (F(4)TCNQ). Here, doping of the semiconducting model polymer poly(3-hexylthiophene), P3HT, using the strong Lewis acid tris(pentafluorophenyl)borane (BCF) as a dopant, is investigated by admittance, conductivity, and electron paramagnetic resonance measurements. The electrical characteristics of BCF- and F(4)TCNQ-doped P3HT layers are shown to be very similar in terms of the mobile hole density and the doping efficiency. Roughly 18\% of the employed dopants create mobile holes in either F-4 TCNQ- or BCF-doped P3HT, while the majority of doping-induced holes remain strongly Coulomb-bound to the dopant anions. Despite similar hole densities, conductivity and hole mobility are higher in BCF-doped P3HT layers than in F(4)TCNQ-doped samples. This and the good solubility in many organic solvents render BCF very useful for p-type doping of organic semiconductors.},
  language  = {en}
}
@article{FritschKurpiersRolandetal.2022,
  author    = {Fritsch, Tobias and Kurpiers, Jona and Roland, Steffen and Tokmoldin, Nurlan and Shoaee, Safa and Ferron, Thomas and Collins, Brian A. and Janietz, Silvia and Vandewal, Koen and Neher, Dieter},
  title     = {On the interplay between CT and singlet exciton emission in organic solar cells with small driving force and its impact on voltage loss},
  series = {Advanced energy materials},
  volume    = {12},
  journal   = {Advanced energy materials},
  number    = {31},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1614-6832},
  doi       = {10.1002/aenm.202200641},
  pages     = {11},
  year      = {2022},
  abstract  = {The interplay between free charge carriers, charge transfer (CT) states and singlet excitons (S-1) determines the recombination pathway and the resulting open circuit voltage (V-OC) of organic solar cells. By combining a well-aggregated low bandgap polymer with different blend ratios of the fullerenes PCBM and ICBA, the energy of the CT state (E-CT) is varied by 130 meV while leaving the S-1 energy of the polymer (ES1\[{E_{{{\rm{S}}_1}}}\]) unaffected. It is found that the polymer exciton dominates the radiative properties of the blend when ECT\[{E_{{\rm{CT}}}}\] approaches ES1\[{E_{{{\rm{S}}_1}}}\], while the V-OC remains limited by the non-radiative decay of the CT state. It is concluded that an increasing strength of the exciton in the optical spectra of organic solar cells will generally decrease the non-radiative voltage loss because it lowers the radiative V-OC limit (V-OC,V-rad), but not because it is more emissive. The analysis further suggests that electronic coupling between the CT state and the S-1 will not improve the V-OC, but rather reduce the V-OC,V-rad. It is anticipated that only at very low CT state absorption combined with a fairly high CT radiative efficiency the solar cell benefit from the radiative properties of the singlet excitons.},
  language  = {en}
}
@article{SchattauerReinholdAlbrechtetal.2012,
  author    = {Schattauer, Sylvia and Reinhold, Beate and Albrecht, Steve and Fahrenson, Christoph and Schubert, Marcel and Janietz, Silvia and Neher, Dieter},
  title     = {Influence of sintering on the structural and electronic properties of TiO2 nanoporous layers prepared via a non-sol-gel approach},
  series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  volume    = {290},
  journal   = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft},
  number    = {18},
  publisher = {Springer},
  address   = {New York},
  issn      = {0303-402X},
  doi       = {10.1007/s00396-012-2708-9},
  pages     = {1843 -- 1854},
  year      = {2012},
  abstract  = {In this work, a nonaqueous method is used to fabricate thin TiO2 layers. In contrast to the common aqueous sol-gel approach, our method yields layers of anatase nanocrystallites already at low temperature. Raman spectroscopy, electron microscopy and charge extraction by linearly increasing voltage are employed to study the effect of sintering temperature on the structural and electronic properties of the nanocrystalline TiO2 layer. Raising the sintering temperature from 120 to 600 A degrees C is found to alter the chemical composition, the layer's porosity and its surface but not the crystal phase. The room temperature mobility increases from 2 x 10(-6) to 3 x 10(-5) cm(2)/Vs when the sinter temperature is increased from 400 to 600 A degrees C, which is explained by a better interparticle connectivity. Solar cells comprising such nanoporous TiO2 layers and a soluble derivative of cyclohexylamino-poly(p-phenylene vinylene) were fabricated and studied with regard to their structural and photovoltaic properties. We found only weak polymer infiltration into the oxide layer for sintering temperatures up to 550 A degrees C, while the polymer penetrated deeply into titania layers that were sintered at 600 A degrees C. Best photovoltaic performance was reached with a nanoporous TiO2 film sintered at 550 A degrees C, which yielded a power conversion efficiency of 0.5 \%. Noticeably, samples with the TiO2 layer dried at 120 A degrees C displayed short-circuit currents and open circuit voltages only about 15-20 \% lower than for the most efficient devices, meaning that our nonaqueous route yields titania layers with reasonable transport properties even at low sintering temperatures.},
  language  = {en}
}