The presented thesis is devoted to the field of organic light emitting
diodes (OLEDs). Time-dependent Kohn-Sham density functional theory
(TDDFT) is applied in order to eludicate optical properties such as fluorescence and
phosphorescence for some of the most important materials. The accuracy of TDDFT
is evaluated with respect to the calculated absorption and emission spectra for
commonly used light emitting polymers. A continuation of this work is devoted to
Polyfluorene as this polymer has proven to be very promising. In this study the
chain length dependence of its singlet and triplet excited states is analyzed as well
as the excited state structures.
Understanding the phosphorescence mechanism of tris(2-phenylpyridine)Iridium is
of importance in order to interpret the high efficiency of OLEDs
containing these specimens. The mechanism is analyzed by calculating
the electric transition dipole moments by means of TDDFT using
quadratic response functions. As not only the optical properties are essential for
effective devices, electron transfer properties are addressed. The electron
transfer capability of the sulfur and nitrogen analogues of Oxadiazole
is evaluated through their internal reorganization energy.
Stockholm: KTH , 2007. , viii, 43 p.