Research On Excited State Properties Of The Carotenoid Derivative

The molecule design, synthesis and charge energy transfer mechanism in organic solar-cell material research have become a most vigour's field in recent years.Carotenoids are ubiquitous in plants, animals and bacteria. Light harvesting by carotenoids is a fundamental part of the earliest reaction in photosynthesis. Light energy that is absorbed by carotenoids is rapidly and efficiently transferred to the chlorophylls, thereby allowing photosynthesis to harvest energy over a wider range of wavelengths than would be possible with chlorophyll alone. It is of great importance to insight into excited state properties of acceptor-substitute carotenoids, because The excited state properties of this oligomer are largely determined by their polyene backbone and the functional groups attached to the polyene chain.In this thesis , the influence of neutral, weak and strong polar function groups to the ground and excited properties of the carotenoids are studied by the method of quantum chemistry(AM1/ZINDO)as well as 2D and 3D real-space analysis methods. the results indicate that the different function groups affect the bond lengths of the polyene chain, charge distribution and electron density . They also influence the direction of charge and energy transfer, the orientations and strength of the transition dipole moment, electron–hole correlation, delocalized size, and the properties in the excited state. the strong polar function group make the first excited state of compound C become the charge transfer excited state.Secondly, the excited state properties of the neurosporene & PPB a der are investigated theoretically with quantum chemistry method. The calculated transition energies and oscillator strengths are consistent with the experimental data. The calculated results show the excited state properties (electron-hole coherence and excitation delocalization) of the doner-accepter system. 2D transition density matrix analysis method indicate that the first, the second, the fifth and the sixth excited states are locally excited states at the PPB a der, however the fourth excited state is locally excited state at the neurosporene. 2D and 3D real-space analysis as well as HOMO/LOMO analysis methods reveal that the third excited state is the intermolecular charge transfer state (charges transfer from the neurosporene to the PPB a der.). The research into the phtoinduced excited state properties of the neurosporene & PPB a der can guide instructive theory for designing the photosynthesis molecule D-A system ,developing efficient solar-cell material and storage medium.