  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 nanowires in time-resolved photoluminescence (PL)
and photoconductivity measurements. The PL transients of the QD luminescence
indicate two different recombination channels: the direct recombination inside
the QD core and the recombination via QD surface defect states. After linking
the QDs to the ZnO NW surface, photo-induced electron tunneling from an excited
state of the QD into the conduction band of the nanowire 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
nanowires in which the tunneling rate can be controlled by using different
organic linker molecules.
