Normally Cesium Fluoride used as a metal-semiconductor interlayer for OLED fabrication to enhance the electron injection, but CsF drastically decrease the hole injection in organic semiconductor devices.How to understand the difference of hole and electron injection with CsF interlayer.
Injection of certain carrier from one material to the other depends on the electrostatic potential barrier facing the transport of this specific charge. This potential barrier i a consequence of different work functions of two materials. The other factor controlling the injection of certain type of charge carriers i their concentration in the injecting material. In thermal equilibrium there is no net flow of charges across the barrier. Because the injection and back injection balance. By polarizing the junction in the forward direction the potential barrier decreases to the flow of holes from the anode and electrons from the cathode. This type of flow is called injection and it is very demonstrative in the pn junction and the pin diode.
Applying these concepts on the introduction of cesium florid to enhance electron injection, it is expected that this material has smaller barrier for the flow electrons from the metal in its direction. To decrease the hole injection at the same time, it must increase the potential barrier to the hole flow from the cathode. And this is required for its function. It is required to favor the injection pf electrons only from the cathode to the active radiative layer of the diode.
Foe more information please see the link:http://scholarworks.rit.edu/cgi/viewcontent.cgi?article=3763&context=theses
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