Quantum confined semiconductor nanocrystals have been widely investigated as light harvesting and charge separation components in photovoltaic and photocatalytic devices. Interest in these materials has intensified due to recent reports multiexciton generation in semiconductor nanocrystals and devices. The efficiency of these semiconductor nanocrystal-based devices depends on many processes, including light harvesting, carrier relaxation, charge separation and charge recombination. The competition between these processes determines the overall solar energy conversion (solar to electricity or fuel) efficiency. Compared with single component quantum dots (QDs), semiconductor nanoheterostructures, combining two or more materials, offer additional opportunities to control their charge separation properties by tailoring their compositions and dimensions through wavefunction engineering. In a series of recent studies, we show that the efficiency of single and multiple exciton dissociation from semiconductor nanocrystals can be effectively controlled. With (quasi)-type II band alignment, forward reactions (charge separation and hole filling) can be facilitated, while the backward recombination (charge recombination and exciton-exciton annihilation) can be simultaneously retarded. We show near-unity quantum yield of redox mediator (methylviologen radical) generation with asymmetric CdSe/CdS dot/rod nano-heterostructures. When coupled with catalysts (Pt), these nanorods lead to a much higher hydrogen generation efficiency compared to molecular dyes and other nanocrystals. In ongoing work, we show that these materials can be used to form high surface area photocathodes, facilitating their integration in photoelectrochemical water splitting devices.

Charge separation dynamics in quantum-confined colloidal nanoheterostructures: From exciton dissociation to light-driven H<sub>2</sub> generation

245th National Meeting (2013)

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Charge separation dynamics in quantum-confined colloidal nanoheterostructures: From exciton dissociation to light-driven H2 generation

Charge separation dynamics in quantum-confined colloidal nanoheterostructures: From exciton dissociation to light-driven H₂ generation