The fabrication of simple OLEDs can be performed in two general ways. The OLED components may be deposited on the glass-ITO substrate either by sublimation in vacuum (vapor deposition) or by deposition from solution in the process called spincoating.
Structure of the vapor-deposited OLEDs we use for our compounds is as follows: on the Indium-Tin Oxide (ITO) coated glass substrate is deposited hole injection layer - copper phthalocyanine (CuPc), followed by a hole-transport layer of N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'diamine (NPD) and layer of electroluminescent complex (e.g. Alq3). Finally, the cesium fluoride blocking layer and aluminum cathode are vapor-deposited on top of the electroluminescent material.
Vapor deposition requires a high-vacuum chamber (below-center) with evaporation sources (below-right) where the compounds are heated in vacuum until they evaporate. The compound vapors condense on the OLED substrate in a highly uniform film. The apparatus shown on the following photograph is from our fabrication laboratory:
Simple OLED devices utilizing small molecules used in our laboratory is shown in the picture. Briefly, indium/tin oxide (ITO) modified glass substrate is covered by a hole-injection layer (HTL) material such as Baytron-PTM (pEDOT/sulfonated polystyrene suspension) by spin-coating. Electroluminescent material is than spin-coated or vapor-deposited on top of the HTL. Finally, the calcium cathode is vapor-deposited on top of the electroluminescent material, and capped by aluminum layer (also vapor-deposited).
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