Synthesis And Properties Of Novel Hole Transport Materials Containing Triphenylamine Groups

Recently, the organic charge transport materials (OCTMs) have been focused to be developed, and have been widely applied in thin layer optoelectronic devices such as xerography, organic light-emitting diodes (OLED), organic solar cells, organic field-effect transistors (OFETs), and so on. OCTMs include organic hole transport materials (OHTMs), organic electron transport materials (OETMs), and organic hole /electron transport materials (OHETMs). As OHTMs, triarylamine derivatives have attracted significant attention due to their excellent optoelectronic properties with high potentialities in both basic and applied researches.Basing on molecular and material designs, 10 kinds of OHTMs including the triphenylamine derivatives, the triphenylamine substituted stilbene derivatives, and the triphenylamine substituted stilbene polymers have been designed and synthesized. The reaction mechanisms were discussed, and the purification methods were investigated. Their molecular structures were characterized by FTIR spectrum, !H NMR spectroscopy and elemental analysis. Their solubility and stability were also investigated. Results showed that the compounds substituted methoxy groups or bromine atoms had better solubility than their parent compounds, and they also have good thermal stability, so they were favorite for the optoelectronic devices with high thermal stability prepared by solution.The effect of molecular structure on the energy bands of the triphenylamine derivatives, the triphenylamine substituted stilbene derivatives, and the triphenylamine substituted stilbene polymers has been studied by combining cyclic voltammetry (CV) and UV-Vis absorption. It is indicated that electron-donor methoxy groups and electron-acceptor bromine atoms exhibit different effect on the three kinds of materials. The introduction of methoxy groups as the substituent in the triphenylamine derivatives can raise the highest occupied molecular orbital (HOMO) level from -5.50 eV to -5.28 eV, lower the lowest unoccupied molecular orbital(LUMO) level from to -2.05 eV to -2.07 eV, whereas the introduction of bromine atoms as the substituent can both lower HOMO and LUMO levels from -5.50 eV to -5.58 eV and from -2.05 to -2.19 eV respectively. The introduction of methoxy groups as the substituent in the triphenylamine substituted stilbene derivatives can both raise HOMO and LUMO levels, whereas the introduction of bromine atoms as the substituent can both lower HOMO and LUMO levels. This could be attributed to the conjugation between the substituent and the parent conjugate system. The larger parent conjugate system, the smaller of the effect of P- n conjugation between the substituent and the parent conjugate system on the energy bands of the conjugate system. The HOMO level, LUMO level and Eg of the triphenylamine derivatives were calculated by semi-empirical PM3 method. The results showed that there exists significant linear correlation between the calculated values and the experimental values.The effect of molecular structure on the photoluminescence spectra of the triphenylamine substituted stilbene derivatives and the triphenylamine substituted stilbene polymers has also been studied. The results showed that with the substituent of the triphenylamine substituted stilbene derivatives changing from the electron-donor of methoxy groups to the electron-acceptor of bromine atoms, themaximum emission wavelength () of their chloroform solutions was blue-shifted,PLmaxand the Stock's shift decreased. When the polarity of solution was increased, the of the triphenylamine substituted stilbene derivatives was red-shifted and the Stock's shift increased. The X of the triphenylamine substituted stilbene derivatives filmcoated by vacuum vapour method had a red shift in contrast to those in the solution of chloroform. The introducing methoxy groups into the triphenylamine substitutedstilbene polymer also resulted in the red shift of the X.The effect of molecular structure on the aggregate structure of hole transport materials containing...