aPhysikalische Chemie, TU-Dresden, D-01062 Dresden
With regard to possible applications in the field of optical switches and circuits DFT based methods have been used to study the influence of an electric field on the optical properties of several organic molecules.
We have investigated a set of α-oligothiophenes with up to six thiophene rings as well as the molecules pyrrole, 2,5-(2',5''-dithienyl-)pyrrole und 3-phenylpyrrole. These molecules can act as terminal functional groups of self-assembly capable molecules.
The dependence of the excitation energies on the electric field strength has been calculated using the time-dependent, density functional based tight binding method TD-DFRTB. In addition the influence of the electric field on the Kohn-Sham-energies has been studied.
The most promising molecules are the α-oligothiophenes. Under the influence of an electric field, which is directed in the molecular plane towards the longest molecular axis, the energy of each lowest, most intensive excitation decreases about 1eV in the range of 1010 V/m. This corresponds to a shift of the absorption bands within the whole visual spectra up to the IR region.