Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 69: Focussed Session: Towards a Quantitative Understanding of Complex Adsorption Structures: Surface Science goes Organic II
O 69.1: Topical Talk
Donnerstag, 3. April 2014, 10:30–11:00, HSZ 01
Injection/extraction barriers in donor-acceptor blends on metals through core-level spectroscopy — •Enrique Ortega1,2, Afaf El-Sayed1, Patrizia Borghetti2, Eli Goiri2, Celia Rogero2, Luca Floreano3, Yutaka Wakayama4, Jose Luis Cabellos-Quiroz2, Duncan Mowbray2, Angel Rubio2, and Dimas Oteyza1,2 — 1Departamento de Física Aplicada I, UPV/EHU, San Sebastian — 2Centro de Física de Materiales and DIPC, San Sebastian — 3Cons. Naz. Ric.-IOM, L. N. TASC, Trieste — 4National Institute Material Science, Tsukuba
The active interface in charge injection devices can be generally defined by a monolayer-thick blend of donor/acceptor molecules in contact with a metal surface, where electron and hole injection/extraction barriers are determined by the offset of HOMO/LUMO molecular levels with respect to EF. HOMO/LUMO alignment is not easy to elucidate in complex multi-component systems from valence band photoemission. Alternatively, we explored core-level photoemission, as a way to transparently assess molecular level alignment in donor-acceptor/metal interfaces. We performed systematic experiments combining acceptor-like fluorinated phthalocyanine (F16CuPc) and perfluoropentacene (PFP) with pentacene (PEN) and copper phthalocyanine (CuPc), respectively, on Au(111), Ag(111) and Cu(111). We observe, as a function of the donor/acceptor ratio, a characteristic binding energy shift in all core-levels, irrespectively of the donor/acceptor/metal combination. The meaning and the exceptions to such general behavior will be discussed. [See A. El-Sayed et al. ACS Nano 7, 6914 (2013)]