@phdthesis{Liess2017,
  author    = {Liess, Andreas},
  title     = {Structure-Property Relationships of Merocyanine Dyes in the Solid State: Charge Transport and Exciton Coupling},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-152900},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {The present thesis demonstrates the importance of the solid state packing of dipolar merocyanine dyes with regard to charge transport and exciton coupling. Due to the charge transport theory for disordered materials, it is expected that high ground state dipole moments in amorphous thin films lead to low mobility values due to a broadening of the density of states. However, due to their inherent dipolarity, merocyanine dyes usually align in antiparallel dimers in an ordered fashion. The examination of twenty different molecules with ground state dipole moments up to 15.0 D shows that by a high dipolarity and well-defined sterics, the molecules pack in a highly regular two-dimensional brickwork-type structure, which is beneficial for hole transport. Utilization of these molecules for organic thin-film transistors (OTFTs) leads to hole mobility values up to 0.21 cm²/Vs. By fabrication of single crystal field-effect transistors (SCFETs) for the derivative showing the highest mobility values in OTFTs, even hole mobilities up to 2.34 cm²/Vs are achieved. Hence, merocyanine based transistors show hole mobility values comparable to those of conventional p-type organic semiconductors and therefore high ground state dipole moments are not necessarily disadvantageous regarding high mobility applications. By examination of a different series of ten merocyanine dyes with the same chromophore backbone but different donor substituents, it is demonstrated that the size of the donor has a significant influence on the optical properties of thin films. For small and rigid donor substituents, a hypsochromic shift of the absorption compared to the monomer absorption in solution is observed due to the card stack like packing of the molecules in the solid state. By utilization of sterical demanding or flexible donor substituents, a zig-zag type packing is observed, leading to a bathochromical shift of the absorption. These packing motifs and spectral shifts with an offset of 0.93 eV of the H- and J-bands comply with the archetype examples of H- and J-aggregates from Kasha's exciton theory.},
  subject      = {Exziton},
  language  = {en}
}