Low-cost processing methods will be required if the small organic molecule materials currently under development for use in organic light emitting diodes (OLEDs) and other electronics are ever to realize wide spread commercial application.
Pacific Northwest National Laboratory researchers have developed a deposition method for such materials that is specifically suited to wide-area, roll-to-roll processing. The method involves injecting a mixture of a non-polymeric organic compound with a fluid carrier into a “hot box” that converts the mixture to the gas phase. The gaseous mixture is then sprayed on a substrate — such as a polymeric substrate mounted in a vacuum web coater — that is kept at a temperature such that the non-polymeric organic compound condenses on the substrate, while the fluid carrier does not condense on the substrate, and thus, can be captured for subsequent reuse.
Use of a fluid transport mechanism allows for extremely high thin-film deposition rates. Using this process, a thin-film layer of a small molecule organic compound can be efficiently and rapidly deposited on a wide area substrate. Proof-of-principle of the technique has been demonstrated by successfully coating the small molecule Alq3 on a PET substrate. The method may also be used to produce “patterned” electronic thin-film devices in which an active small molecule organic material is selectively deposited on a substrate to form a pattern appropriate for the operation of the device.