Structure And Charge Transfer Property Of Star-shaped Molecule: The Density Functional Theory Study

In the recent years, it is one of the important ways to improve and explore new materiel by introducing functional groups to star shaped molecule in order to adjust the structure and charge transfer efficiency and improve the material transport capability. However, it is not clear for the relation between luminescent mechanism, structure and spectrum properties, and theoretical studies on this field are still scarce. In this paper we study and explore the relation between structure and luminescence behavior, structure and carrier transport property of a series of star shaped molecule by using density functional theory(DFT) and time dependent density functional theory(TDDFT). It provides the theoretical basis for designing and synthesizing new star-shaped material. The main work is as follows:(1)The structural, electronic absorption spectrum, fluorescence radiation lifetime and charge transfer properties of a series of star-shaped truxene derivatives which are end-capped by different donors have been studied by means of DFT. The results show that the alternation of ended donor with different electron-releasing ability is not only to change remarkblely the energy gap, absorption and fluorescence spectra but also efficiently modulate charge transport ability. The new designed tetrathiafulvalene (TTF) end-capped truxene derivative presents the multi-directional charge transfer property upon excitation, which are fully investigated by charge density difference and transition density matrix. It is predicted theoretically that this TTF end-capped truxene derivative expected to have the potential application prospect to apply to organic optoelectronic devices.(2)The study of star shaped truxene 2DA type derivatives on geometry and excitation energy properties using various DFT methods indicate, the hybrid density functional that contain a larger Hartree-Fock orbital exchange fraction shows the smaller excitation energy error. The photophysical properties of a series of designed 2DA structure with different conjugated bridge have be studied with optimal DFT method. The result indicates that adjusting structure of conjugate bridge can change the band range and nature of spectral transition. It provides effective guidance to achieve white light emission.(3)A series of star-shaped TTF derivatives were designed by adjusting substituent of phenyl core. Electronic structure, absorption and emission properties have been investigated by using density functional theory on the basis of a comparative research of the similar structure experimental reported. The results indicate that the energy gap can be changed effectively through adjusting the electron-releasing ability of benzene core's meta-substituent and the way of charge transfer also be changed. It has the smaller energy gap for PCNT compound, and exist the absorption band in red areas. It provides the theory guide for synthesizing effectively the new star shaped narrow band gap materials.