Hot Electron Extraction From Colloidal Quantum Dots

Hot electrons are created in core/shell CdSe/ZnSe colloidal quantum dots by mid-infrared intraband (4 mu m) excitation and are probed by time-resolved visible spectroscopy. The hot electron, in the first excited conduction state 1P(e) of the CdSe core, is efficiently extracted by tunneling through the ZnSe shell. Electron extraction times are temperature-independent. They range from similar to 100 ps. for thick, similar to 3 nm, uniform ZnSe shells to < 4 ps for high-surface-area irregular ZnSe shells, and they compete favorably with intraband relaxation. The hot electron extraction leads to a quench of the visible photoluminescence. This is a first step toward infrared detection using the intraband transitions of colloidal quantum dots.