德国洪堡大学Norbert Koch教授2月19日下午学术报告

发布时间:2014-02-17访问量:15设置

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

 

时间:2014219(星期三)下午2:00

地点:909号楼一楼B会议室(Conference Room B, 909-1F)

 

摘要:

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 [1], 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 [2].

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 [3].

[1] G. Heimel, et al., Nat. Chem. 5 (2013) 187.

[2] H. Wang, et al., Adv. Mater., DOI: 10.1002/adma.201303467.

[3] R. Schlesinger, et al., Phys. Rev. B 87 (2013) 155311; Y. Xu, et al., Phys. Rev. Lett. 111 (2013) 226802.

 

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