Analysis of the excited-state absorption spectral bandshape of oligofluorenes
Ημερομηνία
2010Source
Journal of Chemical PhysicsVolume
132Issue
21Google Scholar check
Keyword(s):
Metadata
Εμφάνιση πλήρους εγγραφήςΕπιτομή
We present ultrafast transient absorption spectra of two oligofluorene derivatives in dilute solution. These spectra display a photoinduced absorption band with clear vibronic structure, which we analyze rigorously using a time-dependent formalism of absorption to extract the principal excited-state vibrational normal-mode frequencies that couple to the electronic transition, the configurational displacement of the higher-lying excited state, and the reorganization energies. We can model the excited-state absorption spectrum using two totally symmetric vibrational modes with frequencies 450 (dimer) or 400 cm-1 (trimer), and 1666 cm-1. The reorganization energy of the ground-state absorption is rather insensitive to the oligomer length at 230 meV. However, that of the excited-state absorption evolves from 58 to 166 meV between the oligofluorene dimer and trimer. Based on previous theoretical work [A. Shukla, Phys. Rev. B 67, 245203 (2003)], we assign the absorption spectra to a transition from the 1 Bu excited state to a higher-lying m A g state, and find that the energy of the excited-state transition with respect to the ground-state transition energy is in excellent agreement with the theoretical predictions for both oligomers studied here. These results and analysis permit profound understanding of the nature of excited-state absorption in π -conjugated polymers, which are the subject of general interest as organic semiconductors in the solid state. © 2010 American Institute of Physics.
Collections
Cite as
Related items
Showing items related by title, author, creator and subject.
-
Article
Tin oxide nanowires: The influence of trap states on ultrafast carrier relaxation
Othonos, A.; Zervos, Matthew; Tsokkou, D. (2009)We have studied the optical properties and carrier dynamics in SnO 2 nanowires (NWs) with an average radius of 50 nm that were grown via the vapor-liquid solid method. Transient differential absorption measurements have ...
-
Article
Tin oxide nanowires: The influence of trap states on ultrafast carrier relaxation
Othonos, Andreas S.; Zervos, Matthew; Tsokkou, Demetra (2009)We have studied the optical properties and carrier dynamics in SnO 2 nanowires (NWs) with an average radius of 50 nm that were grown via the vapor-liquid solid method. Transient differential absorption measurements have ...
-
Article
Defect states of chemical vapor deposition grown GaN nanowires: Effects and mechanisms in the relaxation of carriers
Tsokkou, Demetra; Othonos, Andreas S.; Zervos, Matthew (2009)Carrier relaxation in GaN nanowires, grown by atmospheric pressure chemical vapor deposition, via direct nitridation of Ga with NH3 at 950 °C has been investigated in detail. Differential absorption measurements reveal a ...