CFN Colloquium Series
"Solar Energy Conversion Using Artificial Atoms, Molecules and Solids"
Presented by Tianquan (Tim) Lian, Emory University, Atlanta, GA
Tuesday, April 16, 2013, 11 am
Bldg. 735 - Seminar Room, 2nd Floor
Hosted by: Mircea Cotlet
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 in recent years due to reports of multiexciton generation in semiconductor nanocrystals and devices. Compared with single component quantum dots (or "artificial atoms"), semiconductor nanoheterostructures (or "artificial molecules"), which consist of two or more component 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 showed that the efficiency of single and multiple exciton dissociation from semiconductor nanocrystals could be effectively controlled. With (quasi)-type II band alignment, forward reactions (charge separation and hole filling) could be facilitated, while the backward recombination (charge recombination and exciton-exciton annihilation) could be simultaneously retarded, enhancing the charge separation efficiency. We achieved 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 led to a much higher solar-driven hydrogen generation efficiency compared to molecular dyes and other nanocrystals. In ongoing work, we show that these materials can form "artificial solids", facilitating their integration in photoelectrochemical water splitting devices. (Relevant recent publications: JACS(2012),134, 4250&10337&11701&11289)