Substrate dependent charge injection at the V2O5/organic interface

Charge injection at the interface between V2O5 and N,N-'-diphenyl-N,N-'-bis-(1-naphthyl)-1-1(')-biphenyl-4,4(')-diamine (alpha-NPD) was studied. It is found that the energy-level alignment at the V2O5/alpha-NPD is dependent on the underlying substrate, in contrast to previous reports. This phenomenon is consistent with interface dipole theory for weakly pinning interfaces. V2O5 is found to weakly pin the Fermi level, such that the underlying substrate still influences the dipole between V2O5 and alpha-NPD. The charge neutrality level of V2O5 is also found to be 5.35 eV.