Perex
The active interface in charge injection devices is often defined by a monolayer-thick blend of donor and acceptor molecules in contact with a metal surface. We have explored electronic states of such hetero-interfaces using high-resolution core-level photoemission (XPS), near-edge X-ray absorption (NEXAFS), and valence band photoemission (UPS) spectroscopies. A thorough analysis is carried out using Au(111), Ag(111) and Cu(111) surfaces, onto which pentacene (PEN) and copper phthalocyanine (CuPc) are mixed with their fluorinated counterparts F16CuPc and PFP, respectively.
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We analyze in detail the variations in all spectral features as a function of the donor/acceptor ratio, revealing subtle binding energy shifts in core-levels and changes in HOMO/LUMO filling. The systematic exploration allows us to correlate all observations, thereby offering important clues to predict energy barriers for electron/hole injection/extraction in such hybrid interfaces.