The role of the ionization potential in vacuum-level alignment at organic semiconductor interfaces

The charge-injection barriers at interfaces of a pentacene monolayer are investigated. It is found that the charge-injection barrier depends on the substrate work function. Substrate work functions smaller than the ionization potential of pentacene film have vacuum-level alignment, whereas for substrate work functions exceeding the ionization potential of pentacene film, the HOMO of the pentacene film is pinned to near the Fermi level of the substrate (see figure).