Figure 9.

Energy level diagram of a metal–organic semiconductor interface (a) without an interface dipole Δ and (b) with the interface dipole. ϕ_M is the work function of the metal, E_F is the Fermi level, EA and IE are the electron affinity and ionization potential of the organic semiconductor, respectively; ϕ_Be and ϕ_Bh are the electron and hole barriers, respectively; HOMO and LUMO are the highest occupied molecular orbital and lowest unoccupied molecular orbital of the organic semiconductor, respectively; and E_vac(O) is the vacuum level in the organic semiconductor, while E_vac(M) is the metal vacuum level. Reproduced with permission from Ref. [49]. Copyright 1998 AIP Publishing LLC.