UV photoemission study of interfaces related to organic EL devices[Ultraviolet, Electroluminescent]
Interfacial electronic structures related to organic electroluminescent (EL) devices were studied by UV photoemission spectroscopy (UPS). The two classes of interfaces studied were: (1) interfaces in a typical multilayer device Al/Alq{sub 3}/TPD/ITO, where Alq{sub 3} is tris(8-hydroxyquinolino)- aluminum, TPD is N,N{prime}-diphenyl-N,N{prime}-(3-methylphenyl)-1,1{prime}-biphenyl-4,4{prime}-diamine, and ITO is indium tin oxide, and (2) TTN/metals and TCNQ/metals interfaces, where TTN is tetrathianaphthacene and TCNQ is tetracyanoquinodimethane. The UPS studies of the specimen formed by the successive deposition of TPD, Alq{sub 3}, and Al on ITO revealed interfacial energy diagrams, with the vacuum level shift of {minus}0.25 eV (downward) and {minus}0.1 eV (downward) at the TPD/ITO and the Alq{sub 3}/TPD interfaces, respectively. The deposition of TTN and TCNQ on metals showed opposite direction of the shift of the vacuum level, with the positive and negative charge at the vacuum side. This can be explained by considering the charge-transfer between the metal and the organic molecule, with these directions being consistent with the electron donating and accepting ability of these molecules.
- Research Organization:
- Nagoya Univ., Furocho (JP)
- OSTI ID:
- 20034146
- Country of Publication:
- United States
- Language:
- English
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