报告人：Norbert Koch 教授
Institut für Physik, Humboldt-Universit?t zu Berlin, 12489 Berlin, Germany
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
题目: Band bending and interface dipoles at organic and inorganic semiconductor interfaces
地点：909号楼一楼B会议室(Conference Room B, 909-1F)
The electronic properties of interfaces between organic semiconductors and electrodes as well as inorganic semiconductors are crucial for improving organic and hybrid opto-electronic devices. For efficient charge injection, ohmic contacts can generally be achieved by tuning the electrode work function, e.g., by molecular donors and acceptors , in a way to induce strong Fermi-level pinning at the frontier semiconductor energy levels. However, whether band bending in an extended region away from the interface results or a localized interface dipole depends on the electronic coupling strength between the electrode and the organic semiconductor .
Surface band bending, and therefore the work function, of inorganic semiconductors depends on the surface density of states. By depositing a monolayer of strong molecular donors and acceptors, charge transfer to the highest occupied or lowest unoccupied molecular levels occurs. This allows tuning the work function of, e.g., ZnO, in a range of more than 4 eV. Noteworthy, the area charge density that is transferred to the molecular layer can be very low (< 0.1 electron/nm2) to achieve wide tuning ranges .
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