Processing of OLEDs – How an OLED panel is made
The use of polymers as the OLEDs active layers allows obtaining large surfaces through simple and inexpensive solution-based techniques like spin-coating or ink-jet printing. Small molecule emissive materials are typically deposited via the vacuum-evaporation technique. This method is not suitable for the fabrication of polymeric films, however, it enables the formation of well-controlled and homogeneous, very thin layers, which are highly wanted in the construction of very complex multi-layer structures.
Currently most OLED displays are made using vacuum evaporation, using a Shadow Mask (FMM, Fine Metal Mask) to pattern. This is a relatively simple method but it is inefficient and very difficult to scale up to large substrates. The cheapest and very promising technique for large area organic electronics is the ink-jet printing technology. It allows reducing the cost of manufacturing; however, it requires the design of proper inks based on organic semiconductors. The composition of the inks should not contain aggressive, chlorinated solvents in order to avoid damaging the printing machines.