The insertion of a thin LiF layer between Al and tris(8-hydroxyquinolino)-aluminum (Alq(3)) is a significant advance in the practical development of organic light-emitting devices (OLEDs). We studied the chemistry at the buried interface of LiF/Alq(3) using X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Dramatic changes in Al 2p, N 1s, and O 1s line shapes were observed after LiF deposition. These changes were attributed to the partial substitution of hydroxyquinoline ligands of Alq(3) by F-, and the formation of hydroxyquinoline anions at the LiF/Alq(3) interface. The AlqF(-) structure of products was confirmed by ToF-SIMS. (C) 2004 Elsevier B.V. All rights reserved.