Study of lithium fluoride/tris(8-hydroxyquinolino)-aluminum interfacial chemistry using XPS and ToF-SIMS

Abstract 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.