The Fundamental Of Research Organic Light-Emitting Materials

The striking optical property and charge energy transfer ability of organic light-emitting materials motivated more and more people's interest. The research of organic light-emitting materials, including material's excited state property and microscopic light mechanism, has become a vigorous field in recent years.Increasingly accurate quantum chemical methods are being applied to conjugated molecules and polymers. The expected gain in accuracy is not evident in current studies of excitation energies. Nevertheless, it is interesting to establish organic material theoretical models by calculation and analysis.In this thesis, first, intramolecular hydrogen bonding (IHB) and photoinduced intramolecular proton and electron transfer in 2-(2'-hydroxyphenyl)benzothiazole (HBT) were investigated theoretically. The IHB causes planarization of the molecule, which results in the change of the energy level of LUMO, and the change of density of state (DOS) of HOMO. The IHB and intramolecular proton transfer (IPT) was studied by IR spectra, which shows the influence of IHB to the IR spectra and the dynamics of IPT. The excited state properties of them are investigated with 2D and 3D real space representations, which revealed that the intramolecular charge transfer (ICT) also occurs when IPT happens. From the 3D transition density, the orientation of transition dipole moment for enol reverses, compared to that of normal. The orientation of ICT between enol and keto is opposite, which results from the opposite orientation of transition dipole moment between them.Secondly, the excited state properties of PT were theoretically studied with quantum chemical methods as well as 2D site and 3D cube representations. The theoretical results reveal that the 1 ( n→π*) and 1 Ag?(π→π*) excited states are intramolecular charge transfer (ICT) excited states, while the 1 Bu+(π→π*) excited state is the delocalized excited state. The orientation and strengths of the transition dipole moments of them are interpreted with 3D transition density (TD), and the excited state characters of the ICT or localized excitation are investigated with the 3D charge difference densities (CDD). The electron-hole coherence, delocalization and exciton sizes are studied with 2D site representations. The research into the phtoinduced excited state properties of the HBT and PT can guide instructive theory for more efficient organic light-emitting materials development.