Photoemission study of the ITO/triphenylene/perylene/Al interfaces

The interface formation in a ITO-coated glass/triphenylene hexaether/peryle ne tetraester/aluminum heterostructure was studied by ultra-violet photoemi ssion spectroscopy (UPS). The interfaces were built step by step by success ive evaporation of thin (few nm) material layers. Each step was followed by UPS characterization which allowed determination of the evolutions of the valence bands (VBs) and that of the vacuum level. An electronic energy diag ram has been deduced giving the metal/organic barriers and the band offset between the two organic semiconductors. Major differences were observed bet ween the two metal/organic interfaces which can have consequences for light emitting diodes based on these materials. (C) 2001 Elsevier Science B.V. A ll rights reserved.