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HL: Fachverband Halbleiterphysik

HL 30: ZnO and Relatives I

HL 30.6: Vortrag

Dienstag, 27. März 2012, 10:45–11:00, EW 202

Oxygen-controlled photoconductivity in hybrid ZnO-nanowire/CdSe-quantum-dot devices — •dongchao hou, apurba dev, and tobias voss — Semiconductor Optics, Institute of Solid State Physics, University of Bremen

Modern nanotechnology has interest in the assembly and study of hybrid structures composed of different materials that offer enhanced properties or achieve new functions through the interactions between different constituents. We built a hybrid assembly using ZnO nanowire (NW) arrays decorated with colloidal CdSe quantum dots (QDs) which has a potential application in photovoltaics. QDs were synthesized with an aqueous precipitation method and stabilized with mercaptopropionic acid (MPA), through which the QDs are chemically linked to the nanowire surface. A dense and clustered coating of the QDs on the ZnO nanowire surface was achieved via partial removal of the MPA stabilizers. The photoconductivity of this NW/QD assembly was investigated in multiple gas environments using an argon laser to selectively excite electron-hole pairs in the QDs. The photoconductivity was significantly enhanced under laser irradiation. The enhancement achieved in vacuum was more than 6-fold higher than in air. The operation mechanism involving electron transfer between the QDs and the nanowires as well as the surface oxygen desorption was analyzed, which reveals that the passivation of the QD surface defects by oxygen adsorption has significant influence on the relaxation and transfer dynamics of the photo-excited electrons in QDs.