Synthesis And Properties Of A Novel Blue-emitting Material Based On Fluorinated Triphenylamine Substituted Stilbene Derivative

Triphenylamine and its derivatives are well-know organic hole transporting materials, and have been widely applied in organic photoconducting drum, organic light-emitting diodes (OLEDs), organic solar cells, and so on.Basing on the molecular and material designs, a novel p-type blue-emitting material, a fluorinated diphenylamine substituted stilbene derivate of 4, 4'-bis-[2-[4-[N, N-bis- (4-fluoro- phenylamino) ] phenyl-1- yl-vinyl -1-yl]-1,1' -biphenyl (FDPAVBi) was originally synthesized. The reaction mechanisms were discussed, and the reaction conditions and purification methods were investigated. The molecular structure of FDPAVBi was characterized by FTIR, 1HNMR and elemental analysis.Taken its unfluorinated parent compound DPAVBi as as a contrast, the properties of FDPAVBi were intensively studied. The energy levels of the two compounds were researched combining cyclic voltammetry (CV) and UV-Vis absorption spectura, it was found that the introduction of electron-withdrawing fluorine groups lower the energy levels of FDPAVBi's HOMO and LUMO, which may balance the injection/transport of electrons and holes. Also the introduction of fluoric groups enlarges the energy gap, resulting in the shift of FDPAVBi's emission to blue region compared with DPAVBi. The photoluminescence spectra of the compounds were studied, and it showed that FDPAVBi in chloroform solution have a sharp maximum PL peak centered at 460nm upon excited at 380 nm, which is blue-shifted by 7 ran compared to that of DPAVBi .While the FDPAVBi film on quartz substrate showed a maximum PL peak centered at 469nm compaired with that of DPAVBi at 505nm. The relative PL quantum efficiency of FDPAVBi was calculated taking the well-known emitting material, Alq3, as the standard sample and the result showed that FDPAVBi have the PL quantum efficiency 5.7times as high as Alq3 in solution.Through DSC analyses, it was discolosed that FDPAVBi have a glass-transition temperature at 95℃. While the melting point of FDPAVBi was detected to be 296 ℃, which was 80 ℃higher than that of unfluorinated DPAVBi.The aggregate structure of FDPAVBi film prepared by vacuum deposition was studied by XRD test, and the result showed that the flim be absolute amorphous. The 3D configuration of FDPAVBi molecular was simulated by Chem 3D and it found that FDPAVBi molecular have bad flatness which might be the reason of low crystallinity in flim. The luminescence behavior of thermal annealed FDPAVBi film showed that heat treatment an effective method of improving the PL quantum efficiency.Single electron device was fabricated by Physical vacuum deposition (PVD) method and hole mobility of FDPAVBi was measured throught space-charged-limited current (SCLC) mode.And the hole mobility was tested to be 5.5*10-7 cm2/Vs under the measurement condition. Mutilayer photoreceptors were fabricated using oxotitanium phthalocyanine (TiOPc) as charge generation material (CGM) and FDPAVBi or NPD as charge transport material (CTM) in order to study the hole transport property. And it was found that the photoreceptors using FDPAVBi as CTM have lower photosensitivity. The result was explained through the combination of the solubility, the HOMO level, the intrinsic hole mobility, and the compatibility betweenCTM and polycarbonate.