X-ray photoemission and photoabsorption of organic electroluminescent materials

Thin films of tris-(8, hydroxyquinoline) aluminum (Alq(3)) and N,N'-dipheny l-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) were measured u sing synchrotron radiation-based core and valence level photoemission and c ore level photoabsorption to elucidate the element-specific electronic stru cture of organic electroluminescent materials. The energy level alignment o f an Alq(3)/TPD interface is given for both occupied and unoccupied states. A comparison of freshly evaporated films of Alq(3) and TPD with films that have been exposed to intense radiation or oxidative conditions sheds light on possible damage mechanisms of the molecular solid. (C) 1999 American In stitute of Physics. [S0021-8979(99)03613-0].