Using multisize arrays of colloidal CdSe quantum dots to explore charge separation and collection in QD junctions

COLL 19

Emily A. Weiss, eweiss@gmwgroup.harvard.edu1, Ryan C. Chiechi, rchiechi@chemistry.harvard.edu1, Scott M. Geyer, sgeyer@mit.edu2, Venda J. Porter, vporter@alum.mit.edu2, Moungi G Bawendi, mgb@mit.edu2, and George M. Whitesides1. (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, (2) Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139
This paper describes the electrical characteristics of junctions containing 3D arrays of colloidal CdSe quantum dots (QDs) of either a single size or multiple sizes. The electrodes were indium tin oxide (ITO) covered with a thin layer of poly(3,4-ethylenedioxyl- thiophene):poly(styrene sulfonate) (PEDOT:PSS), and eutectic Ga/In. The turn-on voltage of the junctions depended on the size of the QDs next to the PEDOT:PSS. We describe this dependence using a Marcus model to estimate the barrier for charge transfer induced by the energy gap at the QD/PEDOT:PSS interface. Size-selective photoexcitation of the arrays of multiple sizes of QDs helped to determine the location of the interface at which photoinduced charge separation occurred, whether the energy absorbed by the QDs was redistributed before charge separation, and the dependence of the photovoltage on the locations of various sizes of QDs within the junction.
 

Interfacial Electron Transfer and Solar Energy Conversion: From Molecules to Nanomaterials
8:20 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 226, Oral

Division of Colloid & Surface Chemistry

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