Two-Dimensional Electronic Excitations in Self-Assembled Conjugated Polymer Nanocrystals
R. Österbacka,
*
C. P. An,
X. M. Jiang,
Z. V. Vardeny
Several spectroscopic methods were applied to study the
characteristic properties of the electronic excitations in thin films of regioregular and regiorandom polythiophene polymers. In the regioregular polymers, which form two-dimensional lamellar structures, increased interchain coupling strongly influences the traditional one-dimensional electronic properties of the polymer chains. The photogenerated charge excitations (polarons) show two-dimensional delocalization that results in a relatively small polaronic energy, multiple absorption bands in the gap where the lowest energy band becomes dominant, and associated infrared active vibrations with reverse absorption bands caused by electron-vibration interferences. The relatively weak absorption bands of the delocalized polaron in the
visible and near-infrared spectral ranges may help to achieve laser
action in nanocrystalline polymer devices using current injection.
Physics Department, University of Utah, Salt Lake City, UT 84112, USA.
*
On leave from the Department of Physics and the Graduate
School of Materials Research, Åbo Akademi University, Porthansgatan 3, FIN-20500 Turku, Finland.
To whom correspondence should be addressed. E-mail:
val{at}physics.utah.edu
