Theoretical Study of Torsional Disorder in Poly(3-alkylthiophene) Single Chains: Intramolecular Charge-Transfer Character and Implications for Photovoltaic Properties

BJORGAARD J. A., Kose M. E.

JOURNAL OF PHYSICAL CHEMISTRY A, cilt.117, sa.18, ss.3869-3876, 2013 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 117 Sayı: 18
  • Basım Tarihi: 2013
  • Doi Numarası: 10.1021/jp401521j
  • Dergi Adı: JOURNAL OF PHYSICAL CHEMISTRY A
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.3869-3876
  • Kocaeli Üniversitesi Adresli: Hayır

Özet

The role of polymer chain morphology on the optoelectronic properties of polythiophenes is an ongoing investigation with the promise of improving organic photovoltaic performance. Chain morphology is predominantly affected by torsional disorder, which causes localization of holes and electrons in the conjugated backbone. Using the model compound oligo(3-methylthiophene), torsionally disordered oligomers were created to compare with a trans-planar oligomer such as found in crystalline poly(3-hexylthiophene). Low lying electronic excitations are calculated using TD-HF and TD-DFT with various long-range corrected functionals. Probability densities of electron and hole were constructed from natural transition orbitals, giving insight into localization and electron-hole overlap. Overlap is found to be substantially higher in disordered oligomers, indicating a stronger Coulombic interaction between electron and hole. Results suggest that improved photovoltaic performance with increased crystallinity is partially explained by stronger light absorption in crystalline polymers and a higher barrier to charge separation in disordered polymers.