Organic Light-emitting Material Absorption And Emission Spectra Of The Simulation Study

The 21th century is an information scientific era. The construction of the digital information and Infobahn need more high-level Flat Panel Display (FPDs). Organic light emitting diode (OLED) has attract world wide attention in the fields of science and industry due to their many merits of light weight, low cost, broad visual angle, high response speed, spontaneous light-emitting, high brightness and efficiency, etc. Since the discovery of the first organic electroluminescent material, poly ( p-phenylene vinylene ) (PPV) in 1990, the interest in this new functional polymer has greatly increased over the years because it is the simplest and cheapest electroluminescent material. To investigate the relationship between the conformation and optical properties of PPV oligomers (3PV) and to design new organic electroluminescent material using quantum chemical theory has very important practical and theoretical significance nowadays.We have studied the geometries and optical properties of some benzene derivatives such as aniline, nitrobenzene, p-nitroaniline, p-nitrophenol, o-nitrophenol and m-nitrophenol in detail in order to find a suitable chemical model for 3PV. The result is that the adding of diffusion or/and polarization functions into the standard 6-31G* basis set can only affect the structural parameters of substituents clearly. B3LYP/6-31G* and CIS/6-31G* level calculation fits for the optimization of S0 and S1 state for larger molecules respectively. And TD-B3LYP/6-31G* level calculation is suitable for the prediction of optical properties.The relationship between the conformation and optical properties of 3PV is investigated in higher-level chemical model for the first time in this work. The maximum emission wavelength (λem) and oscillator strength are most important properties relative to the capability of luminescent material. The larger dihedral angles are the higher total energy of S0 of 3PV is. The lowest total energy of S0 is appeared when the molecule is planer, which agrees with experimental result. While the most stable conformation is appeared at the geometry with 20( or 30( dihedral angles in the excited state. The maximum absorption wavelength (λabs) and λem based on the stable conformation of S0 and S1 are in good agreement with the experimental values. As the dihedral angles increase, the complete conjunction is destroyed corresponding to blue shift for λabs (53-179nm) and λem (71-218nm).We designed and investigated a series of new organic electroluminescent materials that substituted pyridine, naphthyl, pyrrole, furan, thiophene into the 3PV backbone. We found that the change of phenyl rings by pyridine for the optical properties is very small, while the substituation of naphthyl, pyrrole, furan and thiophene in the center benzene ring get red shift clearly. It should be noticed that the nitrogen atoms in pyridine has lone pair electrons which can ligate with other metal cations and will change the electronic structure and optical property.