Valence band alignment at CdSe quantum dot and ZnO (101bar0) interfaces

COLL 490

Brooke A. Carlson, bcarlson@chem.umn.edu1, Kurtis Leschkies, leschkie@cems.umn.edu2, Eray Aydil, aydil@umn.edu2, and Xiaoyang Zhu, zhu@umn.edu1. (1) Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Smith Hall, Minneapolis, MN 55455, (2) Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Ave SE, Minneapolis, MN 55455
Nanostructured semiconductors, such as CdSe and ZnO, are important materials under study for use in next-generation photovoltaic technology. A key issue governing efficient electron transfer between two semiconductors is interfacial energetic alignment. We explore this issue in a model system, CdSe quantum dots adsorbed on single crystal ZnO(101bar0) surface via molecular linkers, using ultraviolet photoelectron spectroscopy. The valence band maximum (VBM) of the CdSe quantum dots is found to be located at 1.1±0.1 eV above the VBM of ZnO, independent of the size of the quantum dots (2.2-4.2 nm). This finding suggests that there is direct electronic interaction between the quantum dot and the surface that is mediated by occupied states, such that the valence bands are pinned to the Fermi level.
 

Interfacial Electron Transfer and Solar Energy Conversion: From Molecules to Nanomaterials
2:00 PM-5:00 PM, Thursday, April 10, 2008 Morial Convention Center -- Rm. 226, Oral

Division of Colloid & Surface Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008