Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 31: Organic semiconductors

HL 31.7: Vortrag

Mittwoch, 29. März 2006, 16:00–16:15, POT 51

The Transport Gap of Organic Semiconductors Studied Using the Combination of Direct and Inverse Photoemission — •Gianina N. Gavrila, Mihaela Gorgoi, and Dietrich R.T. Zahn — Chemnitz University of Technology, Semiconductor Physics, D-09107, Chemnitz, Germany

Direct valence band photoemission spectroscopy in combination with inverse photoemission spectroscopy is applied to study the densities of occupied and unoccupied electronic states of organic semiconductor materials e.g. perylene derivatives and phthalocyanines. The energy separation derived from the difference between Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) in an organic solid is called HOMO-LUMO gap or transport gap. The charge injection processes require promotion of an electron or a hole from the electrodes into one of the charge transport (HOMO or LUMO) states of the organic film therefore their determination is vitally important. It is proposed that the transport gap of organic materials can be obtained from the edge-to-edge distance between the HOMO and LUMO features. The resulting values of the transport gaps are in good agreement with results of electrical measurements and another method of deriving the transport gap employing measurements of the interface dipole at inorganic/organic interfaces.