Synthesis of Hexa-arylamine Substituted Triphenylene Containing Tetra(ethylene glycol) Chains as Bridge in between and the Application as Hole-Injection and Transport Layer on PLED

Discotic liquid crystal molecules play very important role in academical research field recently. In terms of the structures of discotic liquid crystal molecules, they have a discotic core and flexible side chains. In addition, they also have π-π interaction such that they have stacking properties and can become columnar structures because of their central polymeric core. Therefore, the discotic liquid crystal moleculs can become hole-transport materials due to central polymeric and electon-rich core.
We adopt a similar discotic liquid crystalline synthesis way to synthesize target molecules 7, 11, 15, 19, 21 in this article. The target molecules have a central triphenylene core and different side chains including triphenylamine derivatives and carbazole molecules. We observe these molecules optical and electrochemical properties and the effect of hole-transport layers in organic light emitting diode (OLED).
In the results of the optical properties, these molecular monomers have different HOMO and LUMO energy gap such that there are dual-emission and energy transfer mechanism in solution fluorescence spectrum. In the study of the electrochemical properties, various of triphenylamine derivaties have different oxygen binding site and they make elecropolymerization happen or not. In the applications of the hole-transport materials, the performance of compound 21 is better than other compounds. The electropolymerized-film may have residual cation molecules so they can increase the concentration of hole-transport. Due to this reason , compound 21 is suitable to become hole-transport materials.