-cf <sub> 3 </ Sub> Substituted Ppv Class Of Electroluminescent Materials, Optical And Electrical Properties Of The Td-dft Theoretical Studies

The design and synthesis of electroluminescent polymers, luminescence mechanism and the study of EL devices have been becoming the most active research field in recent years. Poly-phenylene vinylene(PPV) is not only a kind of conducting material but a fine kind of electroluminescent material. The application of PPV is limited for its hard solubility in organic solvent. So the various donor, acceptor substitutions were introduced to change the band gap (Eg), ionization potential (IP) and electron affinity (EA), thus it is a research focus for scientist to improve the solubility, alter the color of luminescence, increase efficiency of luminescence.In this paper, the electronic properties and geometry configuration of a serie of CF3-PPV derivatives were calculated by chemistry method. The geometry structures have been optimized by ab initio HF method, and then the electronic excitation energies of the typical polymers were performed by TD-DFT methods. Influence of conjugated -CN and non-conjugated -CFs electron withdrawing substituents on the molecular structure and photo-electricity properties of PPV-like derivatives were discussed. The result indicated that: (1) The conjugated group 5-CN leads to red shift of the absorption spectrum of the corresponding compounds, and the non-conjugated group -CF3 leads to blue shift. (2) The chain length of the alkoxy side groups has no impact on the excitation energies of PPV substituted by the alkoxy groups. So the modeling structures were simplified and the different alkoxy groups were all substituted for methoxy group. (3) The SCLE-TD method is a feasible way to estimate the excitation transitions for infinite chains of the polymer of the PPV derivatives only through the calculations of the corresponding oligomers,so that the restriction of the existing hardware and the program were broken. (4) Through the comparison of the excitation energies using nonhybrid methods such as BP86, BLYP and hybrid B3LYP, the latter is concluded to be the most suitable functional for computation qualitatively and quantitatively. (5) Computationally, the introduction of electron-withdrawing group trifluoromethyl (-CFs) lower LUMO energies, and increasing the electron affinities of the CFs-substituted PPV-like derivatives, thereby they are expected to be a good kind of suitable materials for electron transport application consequently...