Red / Electron Withdrawing Substituents On The Ppv Polymer Optical And Electrical Properties Of Theoretical Research

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 bandgap(Eg) and ionization potential(IP)-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 energy band structure of series PPV derivatives were calculated by chemistry method. The geometry structures have been optimized by semiempirical method AMI, on the base of this, the electronic properties and energy band structure of typical polymers were performed by EHMACC. The influence of photo-electricity on PPV-like electroluminescent polymers substituted by alkyloxy(-OR) and cyano(-CN) were discussed. The result indicated that: HOCO level(highest occupied crystal orbital) of polymer is raised by electron-donor(-OR) substitutions and ionization potentials is decreased, while LUCO level(lowest unoccupied crystal orbital) is lowered by the electron-acceptor(-CN) substitutions and electron affinities is increased. Band gap of polymer is decreased in both cases. At the same time conducting type is changed from p type of PPV to n and p compatibility type of CN-PPV. The red shift of spectrum of MEH-PPV and CN-PPV and the higher electroluminescence efficiency of CN-PPV were explained. Our calculation is significant to design new type PPV-like polymers with highelectroluminescence efficiency.Time-Dependent Density-Functional Theory is a new method for calculating absorption and emission spectrum. The experiment indicated: the solubility of derivatives of poly(phenylene vinylene) (PPV) in organic solvents increases when OCH3 groups are introduced and when the cis/trans ratio of the olefmic links increases. The aim of this work is to investigate the influence of cis-trans isomerism on the solubility and spectroscopic characteristics of 2.5-dimethoxy-1.4-bis[2-(3,4.5-trimethoxyphenyl)ethenylJbenzene(abbrevi ated MPV) by TD-DFT method. The result of theory calculate and experiment are well agreed.