Electrode-molecular semiconductor contacts: Work-function-dependent hole injection barriers versus Fermi-level pinning

摘要

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 (4.4-5.9 eV). 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.