Conductive coating deposition vacuum evaporators

Most of the transparent conductive coatings are produced by vacuum evaporation and sputtering. Other techniques are hot spraying and chemical vapour deposition, as manufactured by Corning, Pittsburgh Plate Glass (PPG) and others [162]. 

Vacuum evaporators have been in use for several decades for the thermal evaporation of materials, such as metals, onto a specimen to provide a conductive layer and dissipate charge during electron iiucroscopy. Holland [312] is an early authority on the topic of vacuum deposition. Typically, a 12 inch diameter bell jar is fitted onto a vacuum system which includes a rotary pump and diffusion pump. Electrodes are fitted onto the baseplate of the evaporator and connected to a transformer. These electrodes are used for attachment of the metals and the carbon rods for evaporation. An important accessory is a liquid nitrogen trap which is fitted above the diffusion pump to trap oil vapors and keep the vacuum clean, which is essential for carbon coating. 

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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