Electron Tunneling from Colloidal CdSe Quantum Dots to ZnO Nanowires Studied by Time-Resolved Luminescence and Photoconductivity Experiments

Abstract

CdSe quantum dots (QDs) with different organic linker molecules are attached to ZnO nanowires (NWs) to study the luminescence dynamics and the electron tunneling from the QDs to the NWs in time-resolved photoluminescence (PL) and photoconductivity experiments. The PL transients of the QD luminescence indicate two different recombination channels: the direct recombination inside of the QD core and the recombination via QD surface defect states. After linking the QDs to the ZnO NW surface, photoinduced electron tunneling from an excited state of the QD into the conduction band of the NW becomes visible by a clear decrease of the PL decay time. Efficient electron tunneling is confirmed by a strong enhancement of the photocurrent through the functionalized NWs in which the tunneling rate can be controlled by using different organic linker molecules.