Fundamentals of Charge Injection Mechanism

In all of these approaches, the injection process is dominated by the charge injection barrier at the interfaces between the active layer and the metal electrodes, which is defined as the energy separation between Fermi-level Ep of the electrode and HOMO (or LUMO) of the organic layer. Thus, it is necessary to consider electronic properties and band alignment of the MO interfaces. 

Energy diagram of an intrinsic molecular solid. Ip is the ionization potential and is the electron affinity. 

Schematic energy diagrams of an MO interface (a) assuming a common vacuum level and no interface dipole, and (b) with interface dipole. is the metal work function. Ip is the ionization 

Organic Electronics Materials, Processing, Devices and Applications 

The injection barrier on the MO interface is ideally eliminated by using an appropriate electrode. In this case, carriers can freely inject into the organic solid without overcoming any barriers. The interface is viewed as an ohmic contact, that is, contact with a reservoir of free carriers sufficiently large 

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