Baryshnikov G. Structural and spectral properties of heterocirculenes and sensitizing dyes for photovoltaic cells

The thesis is devoted to investigation of the electronic structure and spectral properties of the heterocirculenes, organic and organometallic photosensitizing dyes as being a material for the light-emitting devises and the Gratzel-type solar cells. It is shown in the thesis, that the high symmetry of the heterocirculene molecules imposes the restriction on the electroluminescence properties. On this basis a new azaoxo[8]circulene species were synthesized and their structural and spectral properties were studied for the first time. The particular attention is paid to the aromatic properties of heterocirculene species as the first representatives of the planar antiaromatic cyclooctatetraenes. On the ground of the quantum-chemical study for the heterocirculenes crystal structure it is shown that the strong intermolecular interactions cause the formation of the stable stacking dimers. This provides an appreciable perturbation of the electronic shells for the neighboring molecules. The special attention in the thesis is paid to the initial mechanism of the electric current generation in the Gratzel-type solar cells. Particularly, it is shown that the first exited state of the photosensitizing dye must be able for electron injection into the TiO2 conduction band. In this context, two different mechanisms of the first exited state occupation can be realized: 1) direct mechanism due to intense S0-S1 absorption; 2) indirect mechanism S0-Sn-S1 through the higher exited state levels. It is stressed in the thesis that the conformation of the photosensitizing dye molecule is an important factor which is determined charge transfer and charge separation efficiency. In this connection the numerous non-covalent interactions are important to be taken into account, which is shown in the thesis for the first time.