265147 Synthesis and Properties of Novel Luminescent Compounds Containing Triphenylamine and Thiophene Units

Thursday, November 1, 2012: 2:00 PM
Fayette (Westin )
Yakun Song, Xianggao Li, Shirong Wang and Yin Xiao, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China

Organic light emitting devices(OLEDs) based on low molecular weight organic materials have attracted much attention because of their potential application in full-color and flat-panel displays. In these devices, N,N,N',N'-tetraphenylbenzidine (TPD) derivatives are often used as hole-transporting materials (HTMs) due to their strong electron donating ability, high charge mobility and good thermal stability. But because of the poor solubility, these HTMs can not be used to fabricate OLEDs by solution forming film methods with commercial significance (such as spin-coating and ink-jet printing) to form large-area solid films. Hence, it is necessary to prepare high solubility materials. The TPD-based HTMs can be easily synthesized in moderate yields using cheap raw materials by well-known organic reactions including the Vilsmeier and Wittig reactions. In this paper, we designed and synthesized two compounds H1 and H2 (Fig.1) containing TPD donors, thiophene acceptors and olefinic linkers. The structures were characterized via MS, 1H NMR, FT-IR. H1 and H2 exhibit excellent solubility in common solvents and good film forming properties. The UV-Vis absorption and fluorescence emission spectra of the two compounds in dilute chloroform and on the solid films were measured. It reveals that compounds H1 and H2 exhibit similar spectral behavior. The two compounds exhibit two absorption peaks in the regions of 311-313nm and 353-380nm. For the emission spectra in chloroform solution, the maximum emission peaks are 520nm and 501nm for H1, H2 respectively, corresponding to green light emission. The thermal properties of the two compounds were investigated by differential scanning calorimetry (DSC). The two compounds show similar glass transition temperature (Tg) of 104.04 and 103.60. Cyclic voltammetry measurements show that these compounds have proper HOMO levels for hole injection. In order to investigate the electron distribution of the HOMO and LUMO energy levels of these two compounds, quantum chemical calculations were carried out through the Gaussian 03 program at the B3LYP/6-31G* level. The results show that compounds H1 and H2 have linear structures and proper highest occupied molecular orbital(HOMO) levels. The properties of compounds H1 and H2 indicate that these two compounds are candidates for the application in OLEDs as HTMs.

Fig. 1 Molecular structures of compounds H1 and H2

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