Regensburg 2007 – scientific programme
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DS: Fachverband Dünne Schichten
DS 17: Contact Properties (SYOE 10)
DS 17.4: Talk
Wednesday, March 28, 2007, 18:00–18:15, H32
Electrode - molecular semiconductor contacts: work-function-dependent hole injection barriers versus Fermi-level pinning — •Norbert Koch1 and Antje Vollmer2 — 1Humboldt-Universität zu Berlin, Institut für Physik, Berlin, Germany — 2BESSY GmbH, Berlin, Germany
Contacts between two molecular organic semiconductors [p-sexiphenyl (6P) and pentacene] and conducting polymers based on poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDT:PSS) were investigated with photoemission spectroscopy. The dependence of the hole injection barrier (HIB) at 6P/CP interfaces on substrate work function (WF) exhibited a transition from almost Schottky-Mott limit-like behavior to Fermi-level pinning. For pentacene, no significant variation of the HIB as function of WF was observed, despite the large range of work function spanned by the conducting polymers (4.4 eV to 5.9 eV). The results on contacts with conducting polymers are compared to those with metals, where none of the two limiting cases for HIBs as a function of WF were observed. In addition, we present clear-cut relations between residual water incorporation in PEDT:PSS layers and the resulting surface morphology and work function. These results are of direct relevance for organic opto-electronic device fabrication processes.