The role of interface states in controlling the electronic structure of Alq₃/reactive metal contacts

Gap states induced by the formation of metal/organic interfaces have been observed in a number of instances. Yet, the role that these states play in determining the electronic structure of the interface and the carrier injection barriers has not been clearly established. In this paper, we provide a model for the role of chemistry-induced gap states at Mg/ Alq₃ and Al/Alq₃ interfaces, in particular with regard to the formation of dipole barrier and level bending. We show that these states play a defining role in producing identical Fermi level positions at metal-on-organic and organic-on-metal interfaces. The model is supported by photoemission and current - voltage measurements.