Self-assembled thin layer formation on ITO and Its application to organic LED

Abstract

In recent years, surface modification of solid suface is in the limelight as a new tool to connect macroscopic bulk properties and microscopic properties of materials. Of the known surface modification methods, self-assembly is being studied extensively because of ease of formation and its wide applicability. In this thesis, four kinds of surface active alkoxy silanes, {[4-(Diphenylamino)-phenyl]methoxy}-N-(4,4,4-triethoxy-4-silabutyl)formamide (TPA-CONH-Silane), [(9-Ethylcarbazol-3-yl)methoxy]-N-(4,4,4-triethoxy-4-silabutyl)formamide (Car-CONH-Silane), Diphenyl{4-[(11,11,11-triethoxy-11-silaundecyloxy)methyl]-phenyl}amine (TPA-Silane) and 11,11,11-Triethoxy-1-[(9-ethylcarbazol-3-yl)-methoxy]-11-silaundecane (Car-Silane) were synthesized using (3-isocyanato-propyl)triethoxysilane or platinum catalyzed hydrosilation method. Through the self-assembly onto both Si wafer and ITO, thin layers covalently linked to the substrates were formed successfully and they were characterized by contact angle measurement, AFM and XPS. To study the effect of self-assembled layers on electroluminescent (EL) characteristics of light-emitting devices, we fabricated light-emitting diodes using $Alq_3$ and MEH-PPV as emissive materials. The device configurations were ITO/TPD/$Alq_3$/LiF/Al in the case of $Alq_3$ based devices, and ITO/MEH-PPV/Al in the case of MEH-PPV based devices. Those devices using self-assembled layers showed enhanced EL characteristics than the devices using bare ITO.