Energy level alignment at metal-organic and organic-organic interfaces with Alq3 and NTCDA

The energy level alignment behavior of the widely used materials tris-(8-hydroxyquinoline)aluminum (Alq3) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is investigated. The Integer Charge Transfer (ICT) model is successfully used to predict their overall behavior at weakly-interacting hybridorganic and organic-organic interfaces, including NTCDA/Alq3 bilayers. The EICT- of NTCDA is measured to be 4.35 eV and the EICT+ of Alq3 is found to be 4.3 eV. The Alq3 films furthermore feature an interface dipole in absence of charge transfer due to the intrinsic dipole of the molecule and ordering effects.