Contacts between two molecular organic semiconductors [p-sexiphenyl (6P) and pentacene] and conducting polymers (CPs) were investigated with photoemission spectroscopy. The dependence of the hole injection barrier (HIB) at 6P/CP interfaces on substrate work function (ϕ) 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 ϕ was observed, despite the large range of ϕ spanned by the CPs (4.45.9eV). The results on contacts with CPs are compared to those with metals, where none of the two limiting cases for HIBs as a function of ϕ was observed.

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