@article{DeviAlSutiDoscheetal.2008,
  author    = {Devi, Lekshmi Sudha and Al-Suti, Mohammed K. and Dosche, Carsten and Khan, Muhammad S. and Friend, Richard H. and K{\"o}hler, Anna},
  title     = {Triplet energy transfer in conjugated polymers : I. Experimental investigation of a weakly disordered compound},
  year      = {2008},
  abstract  = {Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. Here, we have investigated triplet diffusion using a model compound that has weak energetic disorder. The Dexter-type triplet energy transfer is found to be thermally activated down to a transition temperature T- T, below which the transfer rate is only weakly temperature dependent. We show that above the transition temperature, Dexter energy transfer can be described within the framework of Marcus theory. We suggest that below T-T, the nature of the transfer changes from phonon-assisted hopping to quantum-mechanical tunneling. The lower electron-phonon coupling and higher electronic coupling in the polymer compared to the monomer results in an enhanced triplet diffusion rate.},
  language  = {en}
}
@article{EvansDeviMaketal.2006,
  author    = {Evans, Nicholas R. and Devi, Lekshmi Sudha and Mak, Chris S. K. and Watkins, Scott E. and Pascu, Sofia I. and K{\"o}hler, Anna and Friend, Richard H. and Williams, Charlotte K. and Holmes, Andrew B.},
  title     = {Triplet energy back transfer in conjugated polymers with pendant phosphorescent iridium complexes},
  issn      = {0002-7863},
  doi       = {10.1021/Ja0584267},
  year      = {2006},
  abstract  = {The nature of Dexter triplet energy transfer between bonded systems of a red phosphorescent iridium complex 13 and a conjugated polymer, polyfluorene, has been investigated in electrophosphorescent organic light-emitting diodes. Red- emitting phosphorescent iridium complexes based on the [Ir(btp)2(acac)]fragment (where btp is 2-(2 '- benzo[b]thienyl)pyridinato and acac is acetylacetonate) have been attached either directly (spacerless) or through a - (CH2)(8)-chain (octamethylene-tethered) at the 9-position of a 9-octylfluorene host. The resulting dibromo- functionalized spacerless (8) or octamethylene-tethered (12) fluorene monomers were chain extended by Suzuki polycondensations using the bis(boronate)-terminated fluorene macromonomers 16 in the presence of end-capping chlorobenzene solvent to produce the statistical spacerless (17) and octamethylene-tethered ( 18) copolymers containing an even dispersion of the pendant phosphorescent fragments. The spacerless monomer 12 adopts a face-to-face conformation with a separation of only 3.6 angstrom between the iridium complex and fluorenyl group, as shown by X-ray analysis of a single crystal, and this facilitates intramolecular triplet energy transfer in the spacerless copolymers 17. The photo- and electroluminescence efficiencies of the octamethylene-tethered copolymers 18 are double those of the spacerless copolymers 17, and this is consistent with suppression of the back transfer of triplets from the red phosphorescent iridium complex to the polyfluorene backbone in 18. The incorporation of a -(CH2)(8)- chain between the polymer host and phosphorescent guest is thus an important design principle for achieving higher efficiencies in those electrophosphorescent organic light-emitting diodes for which the triplet energy levels of the host and guest are similar},
  language  = {en}
}
@article{KoehlerBeljonne2004,
  author    = {K{\"o}hler, Anna and Beljonne, David},
  title     = {The singlet-triplet exchange energy in conjugated polymers},
  issn      = {1616-3028},
  year      = {2004},
  language  = {en}
}
@article{ZhangHayerAlSutietal.2006,
  author    = {Zhang, Ning and Hayer, Anna and Al-Suti, Mohammed K. and Al-Belushi, Rayya A. and Khan, Muhammad S. and K{\"o}hler, Anna},
  title     = {The effect of delocalization on the exchange energy in meta- and para-linked Pt-containing carbazole polymers and monomers},
  doi       = {10.1063/1.2200351},
  year      = {2006},
  abstract  = {A series of novel platinum-containing carbazole monomers and polymers was synthesized and fully characterized by UV-VIS absorption, luminescence, and photoinduced absorption studies. In these compounds, a carbazole unit is incorporated into the main chain via either a para- or a meta-linkage. We discuss the effects of linkage and polymerization on the energy levels of S-1, T-1, and T-n. The S-1-T-1 splitting observed for the meta-linked monomer (0.4 eV) is only half of that in the para-linked monomer (0.8 eV). Upon polymerization, the exchange energy in the para- linked compound reduces, yet still remains larger than in the meta-linked polymer. We attribute the difference in exchange energy to the difference in wave function overlap between electron and hole in these compounds. (c) 2006 American Institute of Physics},
  language  = {en}
}
@article{KhanAlMandharyAlSutietal.2004,
  author    = {Khan, Muhammad S. and Al-Mandhary, Muna R. A. and Al-Suti, Mohammed K. and Al-Battashi, Fathiya R. and Al-Saadi, Sultan and Bjernemose, Jens K. and Mahon, Mary F. and Chawdhury, Nazia and Yonus, Muhammad and K{\"o}hler, Anna and Teat, Simon J. and Marseglia, Elizabeth A. and Tedesco, Emilio and Feeder, Neil and Ahrens, Birte and Raithby, Paul R.},
  title     = {Synthesis, characterisation and optical spectroscopy of platinum(II) di-ynes and poly-ynes incorporating condensed aromatic spacers in the backbone},
  issn      = {1477-9226},
  doi       = {10.1039/B405070C},
  year      = {2004},
  language  = {en}
}
@article{YangVardenyKoehleretal.2004,
  author    = {Yang, C. and Vardeny, Z. V. and K{\"o}hler, Anna and Wohlgenannt, M. and Al-Suti, Mohammed K. and Khan, Muhammad S.},
  title     = {Spectroscopic study of spin-dependent exciton formation rates in pi-conjugated semiconductors : Comparison with electroluminescence techniques},
  year      = {2004},
  abstract  = {It has been found in recent measurements that the singlet-to-triplet exciton ratio in organic light-emitting diodes (OLEDs) is larger than expected from spin degeneracy, and that singlet excitons form at a larger rate than triplets. We employed the technique of optically detected magnetic resonance to measure the spin-dependent exciton formation rates in films of a polymer and corresponding monomer, and explore the relation between the formation rates and the actual singlet-to-triplet ratio measured previously in OLEDs. We found that the spin-dependent exciton formation rates can indeed quantitatively explain the observed exciton yields, and that singlet formation rates and yields are significantly enhanced only in polymer OLEDs, but not in OLEDs made from the corresponding monomer},
  language  = {en}
}
@article{SandeeWilliamsEvansetal.2004,
  author    = {Sandee, A. J. and Williams, Charlotte K. and Evans, N. R. and Davies, J. E. and Boothby, C. E. and K{\"o}hler, Anna and Friend, Richard H. and Holmes, Andrew B.},
  title     = {Solution-processible conjugated electrophosphorescent polymers},
  year      = {2004},
  language  = {en}
}
@article{HahnTscheuschnerSalleretal.2016,
  author    = {Hahn, Tobias and Tscheuschner, Steffen and Saller, Christina and Strohriegl, Peter and Boregowda, Puttaraju and Mukhopadhyay, Tushita and Patil, Satish and Neher, Dieter and B{\"a}ssler, Heinz and K{\"o}hler, Anna},
  title     = {Role of Intrinsic Photogeneration in Single Layer and Bilayer Solar Cells with C-60 and PCBM},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {120},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.6b08471},
  pages     = {25083 -- 25091},
  year      = {2016},
  language  = {en}
}
@article{HayerKoehlerArisietal.2004,
  author    = {Hayer, Anna and K{\"o}hler, Anna and Arisi, E. and Bergenti, I. and Dediu, A. and Taliani, C. and Al-Suti, Mohammed K. and Khan, Muhammad S.},
  title     = {Polymer light-emitting diodes with spin-polarised charge injection.},
  issn      = {0379-6779},
  year      = {2004},
  language  = {en}
}
@article{KhanSreearunothaiHerzetal.2004,
  author    = {Khan, Amena L. T. and Sreearunothai, Paiboon and Herz, Laura M. and Banach, Michael J. and K{\"o}hler, Anna},
  title     = {Morphology-dependent energy transfer within polyfluorene thin films},
  year      = {2004},
  language  = {en}
}
@article{HayerKhanFriendetal.2005,
  author    = {Hayer, Anna and Khan, A. L. T. and Friend, Richard H. and K{\"o}hler, Anna},
  title     = {Morphology dependence of the triplet excited state formation and absorption in polyfluorene},
  year      = {2005},
  language  = {en}
}
@article{MermerVeeraraghavanFrancisetal.2005,
  author    = {Mermer, {\"O}. and Veeraraghavan, G. and Francis, T. L. and Sheng, Y. and Nguyen, D. T. and Wohlgenannt, M. and K{\"o}hler, Anna and Al-Suti, Mohammed K.},
  title     = {Large magnetoresistance in nonmagnetic pi-conjugated semiconductor thin film devices},
  year      = {2005},
  abstract  = {Following the recent observation of large magnetoresistance at room temperature in polyfluorene sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different pi-conjugated polymers and small molecules. The study includes a range of materials that show greatly different chemical structure, mobility, and spin-orbit coupling strength. We study both hole and electron transporters at temperatures ranging from 10 K to 300 K. We observe large negative or positive magnetoresistance (up to 10\% at 300 K and 10 mT) depending on material and device operating conditions. We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results.},
  language  = {en}
}
@article{KrohEllerSchoetzetal.2022,
  author    = {Kroh, Daniel and Eller, Fabian and Sch{\"o}tz, Konstantin and Wedler, Stefan and Perdig{\´o}n-Toro, Lorena and Freychet, Guillaume and Wei, Qingya and D{\"o}rr, Maximilian and Jones, David and Zou, Yingping and Herzig, Eva M. and Neher, Dieter and K{\"o}hler, Anna},
  title     = {Identifying the signatures of intermolecular interactions in blends of PM6 with Y6 and N4 using absorption spectroscopy},
  series = {Advanced functional materials},
  volume    = {32},
  journal   = {Advanced functional materials},
  number    = {44},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1616-301X},
  doi       = {10.1002/adfm.202205711},
  pages     = {14},
  year      = {2022},
  abstract  = {In organic solar cells, the resulting device efficiency depends strongly on the local morphology and intermolecular interactions of the blend film. Optical spectroscopy was used to identify the spectral signatures of interacting chromophores in blend films of the donor polymer PM6 with two state-of-the-art nonfullerene acceptors, Y6 and N4, which differ merely in the branching point of the side chain. From temperature-dependent absorption and luminescence spectroscopy in solution, it is inferred that both acceptor materials form two types of aggregates that differ in their interaction energy. Y6 forms an aggregate with a predominant J-type character in solution, while for N4 molecules the interaction is predominantly in a H-like manner in solution and freshly spin-cast film, yet the molecules reorient with respect to each other with time or thermal annealing to adopt a more J-type interaction. The different aggregation behavior of the acceptor materials is also reflected in the blend films and accounts for the different solar cell efficiencies reported with the two blends.},
  language  = {en}
}
@article{HayerdeHalleuxKoehleretal.2006,
  author    = {Hayer, Anna and de Halleux, Veronique and K{\"o}hler, Anna and El-Garoughy, Abdel and Meijer, E. W. and Barbera, Joaquin and Tant, Julien and Levin, Jeremy and Lehmann, Matthias and Gierschner, Johannes and Cornil, Jerome and Geerts, Yves Henri},
  title     = {Highly fluorescent crystalline and liquid crystalline columnar phases of pyrene-based structures},
  issn      = {1520-6106},
  doi       = {10.1021/Jp0573689},
  year      = {2006},
  abstract  = {A concept for highly ordered solid-state structures with bright fluorescence is proposed: liquid crystals based on tetraethynylpyrene chromophores, where the rigid core is functionalized with flexible, promesogenic alkoxy chains. The synthesis of this novel material is presented. The therniotropic properties are studied by means of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), and X-ray diffraction. The mesogen possesses an enantiotropic Col(h) phase over a large temperature range before clearing. The material is highly fluorescent in solution and, most remarkably, in the condensed state, with a broad, strongly red shifted emission. Fluorescence quantum yields (Phi(F)) have been determined to be 70\% in dichloromethane solution and 62\% in the solid state. Concentration- and temperature-dependent absorption and emission studies as well as quantum-chemical calculations on isolated molecules and dimers are used to clarify the type of intermolecular interactions present as well as their influence on the fluorescence quantum yield and spectral properties of the material. The high luminescence efficiency in the solid state is ascribed to rotated chromophores, leading to an optically allowed lowest optical transition},
  language  = {en}
}
@article{ParkinsonAharonChangetal.2007,
  author    = {Parkinson, P. and Aharon, E. and Chang, M. H. and Dosche, Carsten and Frey, G. L. and K{\"o}hler, Anna and Herz, L. M.},
  title     = {Dimensionality-dependent energy transfer in polymer-intercalated SnS2 nanocomposites},
  doi       = {10.1103/Physrevb.75.165206},
  year      = {2007},
  abstract  = {We have investigated the influence of dimensionality on the excitation-transfer dynamics in a conjugated polymer blend. Using time-resolved photoluminescence spectroscopy, we have measured the transfer transients for both a three-dimensional blend film and for quasi-two-dimensional monolayers formed through intercalation of the polymer blend between the crystal planes of an inorganic SnS2 matrix. We compare the experimental data with a simple, dimensionality- dependent model based on electronic coupling between electronic transition moments taken to be point dipoles. Within this approximation, the energy-transfer dynamics is found to adopt a three-dimensional character in the solid film and a two-dimensional nature in the monolayers present in the SnS2-polymer nanocomposite.},
  language  = {en}
}
@article{MakHayerPascuetal.2005,
  author    = {Mak, Chris S. K. and Hayer, Anna and Pascu, S. I. and Watkins, Scott E. and Holmes, Andrew B. and K{\"o}hler, Anna and Friend, Richard H.},
  title     = {Blue-to-green electrophosphorescence of iridium-based cyclometallated materials.},
  issn      = {0022-4936},
  doi       = {10.1039/b508695gb70},
  year      = {2005},
  language  = {en}
}