@phdthesis{Reitzenstein2010,
  author    = {Reitzenstein, D{\"o}rte},
  title     = {Donor-Acceptor Conjugated Polymers for Application in Organic Electronic Devices},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-53939},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {In the first part of the work three polycarbazoles poly[N-((4-dimesitylboryl)-3,5-dimethylphenyl)-carbazole]-2,7-diyl P1, poly[N-((4-dimesitylboryl)-3,5-dimethylphenyl)-carbazole]-3,6-diyl P2 and poly[N-(4-(diphenylmethylene)-phenyl)- carbazole]-2,7-diyl P3 were synthesized by Yamamoto coupling reaction and their spectroscopic and electrochemical properties were investigated. Absorption and fluorescence characteristics of P1 and P3 were found to be similar to other 2,7-linked polycarbazoles, whereas P2 shows a CT absorption band arising from a shift of electron density from the nitrogen of the carbazole donor to the triarylborane acceptor. This causes a negative solvatochromic absorption and a positive solvatochromic fluorescence behaviour and is responsible for the significantly enlarged fluorescence quantum efficiency in solution and solid state compared to other 3,6-linked polycarbazoles. Thus the spectroscopic properties are governed by the connection pattern: the 2,7-linked polycarbazoles are not affected by the acceptor substituent due to the rigid poly-para-phenylene-like backbone structure, whereas the 3,6-linked polycarbazole P2 is dominated by the properties of the monomer unit due to its more flexible (less conjugated) structure. The oxidative processes of P1-P3 have been investigated in detail by cyclic voltammetry, which are similar to known 2,7- and 3,6-polycarbazoles. The reversible reduction found for P1 and P2, respectively, is attributed to the reduction of the triarylborane moiety. No reduction process referring to the carbazole moiety was observed. Due to its better solubility compared to P1 and P3 only P2 was used as active layer in an OLED device (ITO/P2/Al). The electroluminescence spectrum revealed CIE coordinates of (0.17, 0.21). In the second part of the work the low band gap polyradical poly{[((2,3,4,5,6-pentachlorophenyl)-bis(2,3,5,6-tetrachlorophenyl)methyl radical)-4,4'-diyl]-alt-4,4'-bis(vinylphenyl)-4-(2-ethylhexyloxy)phenylamin} P4 was synthesized by Horner-Emmons reaction. It shows an IV-CT band in the NIR, which arises from an ET from the triarylamine donor to the PCTM radical acceptor. This transition is confined to one monomer unit as deduced from comparison with the monomer spectra. HOMO and LUMO of P4 determined by cyclic voltammetry are at -5.5 and -4.5 eV, respectively. The smaller electrochemical band gap (1.0 eV) compared to the optical band gap (1.2 eV) is probably caused by ion pairing effects in the electrochemical experiments and indicates a low exciton binding energy. Femtosecond-pump-probe transient absorption spectroscopy revealed the spectral features of the oxidized triarylamine donor and the reduced PCTM acceptor similar to the spectra obtained separately for positive and negative potentials by spectroelectrochemistry. Thus the ET event causing the IV-CT absorption band could unambiguously be identified. The decay of the IV-CT state was found to be biexponential. The fast solvent dependent decay component is ascribed to the direct decay from the IV-CT state to the ground state, whereas the slow solvent independent decay component is tentatively attributed to an equilibrium formation of the IV-CT state and a completely charge separated state formed by charge migration along the polymer backbone. Well balanced ambipolar charge transport with hole and electron mobilities of ca. 3 × 10-5 cm2 V-1 s-1 was found in OFET devices (BG/TC structure) comprising an additional insulating organic PPcB layer. Polymer/polymer BHJ solar cell devices with the structure glass/ITO/PEDOT:PSS/(P3HT/P4)/Ca/Al yielded a power conversion efficiency of 3.1 × 10-3 \%, VOC = 0.38 V, JSC = 2.8 × 10-2 mA cm-2 and FF = 0.29 for the 1:4 (P3HT/P4) blend ratio. The improper solid state morphology of P4 that causes the unsatisfying performance of OFET and solar cell devices renders P4 less suitable for these applications, whereas the hypothesis of charge migration in the excited state is worth to be investigated in more detail.},
  subject      = {Carbazolderivate},
  language  = {en}
}