Electronic characterization of molecules with application to organic light emitting diodes

Abstract: The presented thesis is devoted to the field of organic light emittingdiodes (OLEDs). Time-dependent Kohn-Sham density functional theory(TDDFT) is applied in order to eludicate optical properties such as fluorescence andphosphorescence for some of the most important materials. The accuracy of TDDFTis evaluated with respect to the calculated absorption and emission spectra forcommonly used light emitting polymers. A continuation of this work is devoted toPolyfluorene as this polymer has proven to be very promising. In this study thechain length dependence of its singlet and triplet excited states is analyzed as wellas the excited state structures.Understanding the phosphorescence mechanism of tris(2-phenylpyridine)Iridium isof importance in order to interpret the high efficiency of OLEDscontaining these specimens. The mechanism is analyzed by calculatingthe electric transition dipole moments by means of TDDFT usingquadratic response functions. As not only the optical properties are essential foreffective devices, electron transfer properties are addressed. The electrontransfer capability of the sulfur and nitrogen analogues of Oxadiazoleis evaluated through their internal reorganization energy.