Photoluminescence quenching of Alq3 by metal deposition:: A surface analytical investigation

The importance of the interfacial properties in organic light-emitting devices (OLED) is well recognized. We will describe our recent efforts to understand interfaces in OLEDs using surface/interface analytical techniques in a well controlled ultrahigh vacuum environment. We observed severe photoluminescence quenching of organic thin films comprising of a model OLED material, namely tris-(8-hydroxyquinoline) aluminum (Alq(3)), upon deposition of a number of metals. Such quenching may severely affect the electroluminescence device efficiency. We have investigated the interfaces using x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy, and studied the intriguing process of the interface formation at an atomic/molecular level. We will show that microscopic surface and interface properties are intimately related to the device characteristics and performance. (C) 1998 American Vacuum Society.