Suppression of penetration of aluminum into 8-hydroxyquinoline aluminum via a thin oxide barrier

We report a direct observation of Al penetration into an organic film of 8-hydroxyquinoline aluminum (Alq) in a Alq/Al bilayer, a common interface occurring in many organic light-emitting diode structures. The Al penetration has a strong correlation with Alq photoluminescence quenching. We also demonstrate that the penetration and luminescence quenching can be effectively suppressed by ∼20 Å of an intervening layer of Al2O3 at the Alq/Al interface.