In OLED organic layers electron injection is improved by using alkali metals as cathodes, to lower work function or, as dopants of organic layer at cathode interface.
The creation of an alkali metal layer can be accomplished through conventional physical vapor deposition from a heated dispenser. However alkali metals are very reactive and must be handled in inert atmosphere all through the entire process. If a contamination takes place, it reduces the lithium deposition rate and also the lithium total yield in a not controlled way.
An innovative alkali metal dispensing technology has been developed to overcome these problems and ensure OLED alkali metal cathode reliability.
The alkali Metal dispenser, called Alkamax, will be able to release up to a few grams of alkali metals (in particular Li and Cs) throughout the adoption of a very stable form of the alkali metal.
Lithium, for example, can be evaporated “on demand”: the evaporation could be stopped and re-activated without losing alkali metal yield because the metal not yet consumed remains in its stable form.
A full characterization of dispensing material, dispenser configuration and dispensing process has been carried out in order to optimize the evaporation and deposition dynamics of alkali metals layers.
The study has been performed applying also inside developed simulations tools.