Hole indium compounds

Table 4.1-86 Effective masses of electrons (nin) and holes (nip) for indium compounds (in units of the electron mass mo)...

Table4.1-89 Electron and hole mobilities /in and /tp of indium compounds...

A typical multilayer thin film OLED is made up of several active layers sandwiched between a cathode (often Mg/Ag) and an indium-doped tin oxide (ITO) glass anode. The cathode is covered by the electron transport layer which may be A1Q3. An emitting layer, doped with a fluorescent dye (which can be A1Q3 itself or some other coordination compound), is added, followed by the hole transport layer which is typically a-napthylphenylbiphenyl amine. An additional layer, copper phthalocyanine is often inserted between the hole transport layer and the ITO electrode to facilitate hole injection. 

There are two main classes of materials from which OLED devices can be made, low-molar-mass compounds, often referred to as small molecules, which are deposited by vacuum evaporation [1] and mainchain, highly conjugated polymers, which are processed from solution by ink-jet printing, for example [10]. A hole injection layer is often used as the first layer on top of the conductive indium tin oxide (ITO) coated substrate. This layer can be either an evaporated small molecule, such as copper phthalocyanine, or a conductive polymer like poly(3,4-ethylenedioxythiophene) (PEDT) shown in Fig. 7.3 [11]. The role of the hole injection layer is to match the HOMO levels of the ITO and the hole transport materials, such as aromatic amines, and, especially in the case of PEDT, to planarise the rough ITO surface. 

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