Charge Carrier Transport and Interfacial Transfer in QD Solid ElectrodesYe Yang, Tianquan LianDepartment of Chemistry, Emory University, 1515 Dickey Drive NE, Atlanta, Georgia 30322, United States  ABSTRACT: Due to their unique properties arising from strong quantum confinement, semiconductor quantum dot (QDs) has been investigated intensely as a light harvesting material for solar-driven hydrogen production. However, so far, sacrificial electron donors are required for most of the reported solar-to-H2 generation studies. One approach to eliminate sacrificial electron donor is to couple the water reduction components with water oxidation photoanode in a full water splitting photoelectrochemical cell, with the latter providing the protons and electrons needed for the reduction part of the cell. QD solid electrode can be a promising photocathode candidate for light-driven hydrogen generation because the QD solid can exhibit high photoconductivity due to strong coupling between the closely packed QDs, while maintaining quantum confinement in individual dots. Using CdSe QD solids as an example, we showed that electrons in QDs at the surface of the electrode could be transferred to methyl viologen (MV2+) molecules in the solution with an average time of <107 fs, while the electrons in the QD inside the solid could be transported to the surface to reduce MV2+ with an effective time constant of 12 ps. The rate for the latter process was to be controlled by diffusion of electrons in the solid. We observed a 100% quantum efficiency of MV2+ photoreduction in this system, which can be attributed to a high carrier mobility in the solid and fast electron transfer at the interface. Encouraged by this initial finding, in ongoing studies are exploring the application of  QD solids as photocathodes for light-driven H2 evolution.

Charge carrier transport and interfacial transfer in QD solid electrodes

246th National Meeting (2013)

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