Research On High Performance Organic Second Order Nonlinear Optical Materials

Since the 21st century,with the rapid development of information technology,people have higher and higher requirements for information transmission speed,storage and processing.The traditional microelectronic integrated circuit has some problems such as poor heat dissipation and low transmission efficiency.With the development of photonics,optical communication based on light wave becomes more and more prominent.In recent years,the application of organic optical materials in optical switches,optical sensors,information processing and communication fields has attracted wide attention.Organic second-order nonlinear electro-optic materials are an important part of organic optical materials.In order to meet the strict requirements of various devices,organic second-order nonlinear electro-optic materials need to have high first-order hyperpolarizability,good thermal stability and good chemical stability.Based on the above problems,we designed the organic second-order nonlinear optics(NLO)chromophores to improve the electro-optical performance and stability of the chromophores.The work of this paper mainly includes the following two aspects:1.A strong modifiable double donor based on Bis(N-Ethyl-N-hydroxyethyl)aniline-derivatived structure was developed and applied to nonlinear optical materials for the first time.Three isolation groups were introduced into the donor and bridge sides of the chromophores to reduce the electrostatic interaction between molecules,so as to improve the poling efficiency.Based on this,we have developed a series of nonlinear optical chromophores BLD1-4 with the same Bis(N-Ethyl-N-hydroxyethyl)aniline-based donor and TCF or CF₃-TCF acceptor with isophorone-derived bridges.Density functional theory calculations suggested the four chromophores have much larger hyperpolarizability than traditional nonlinear optical chromophores due to strong electron donor ability.Poled films of neat chromophore BLD1-BLD4 showed very high poling efficiencies due to large steric hindrance and first-order hyperpolarizability of chromophore.An ultrahigh r₃₃(351 pm/V)and poling efficiency(3.50±0.10 nm²/V²)have been achieved for Neat films containing chromophore BLD3.2.A series of theoretically driven chromophore based on tetrahydroquinoline donor with isophorone derived bridge and CF₃-TCF receptor have been synthesized and systematically studied.Tetrahydroquinoline groups modified with anthracene,acrylate and dendritic macromolecules were designed to enhance the electron-giving ability and thermal stability of chromophore.Redshift?_maxand a small energy range confirm a stronger electron-giving capacity than most chromophores,resulting in a greater first-order hyperpolarizability.DFT calculation shows that the chromophores with tetrahydroquinoline donor have higher first-order hyperpolarizability.In pure chromophores,QLD4 obtained a r₃₃value of 276pm/V after polarization,and had a high polarization efficiency of 3.43±0.13nm²/V².Moreover,the polarization efficiency and electro-optical coefficient of chromophores after cross-linking were still high.