Abstract
A variety of triaryldiamines were synthesized and the use of these compounds as hole transporting layers (HTL) in bilayer organic light-emitting diodes (OLED), fabricated using either tris(8-hydroxyquinolinyl) aluminum (Alq3) or 1,3,5-tris(1-phenyl-1H-2-benzimidazolyl) benzene (TPBI) as the electron transporting layers (ETL), was explored. The efficiency of the devices was assessed by measuring their current density vs. voltage, luminance vs. voltage, and external quantum efficiency vs. current density characteristics. It was discovered that the turn-on voltage is related to the energy barrier of indium tin oxide (ITO) and HTL interface. As well, the external quantum efficiency of the devices is related to not only the energy barrier of the ITO/HTL interface, but also that of the HTL/ETL interface. The details of this study comprised the first part of this thesis. A series of 5-substituted 1,3-bis(1-phenyl-1H-2-benzimidazolyl) benzene (BPBI) were synthesized and its utility as electron transporting layers of OLEDs, fabricated using 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (NPB) as the HTL, was investigated. The performance of these devices as measured in terms of current density, brightness, and quantum efficiency as a function of substitution is assessed and discussed in the second part of this thesis.