Silicon quantum dots in thermoelectric material applications

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Major advances in efficient, clean and secure energy conversion and use are needed if we are to reduce global greenhouse gas emissions, for example to meet the EU's commitment of a reduction of 80% by 2050. Thermoelectric materials are able to take advantage of wasted or unutilized heat sources, such as in furnaces, car exhausts, and solar cells. As a result, thermoelectric materials have become an area of great interest. These materials are able to convert a temperature gradient into electrical power, and vice versa, without mechanical intervention. The power output from current commercial modules produced are however, modest, but power generated from these devices are then used elsewhere for low power applications, e.g. powering sensors or safety feedback loops. We have successfully synthesized Phenyl-acetylene functionalized Silicon quantum dots (SiQDs) which are showing potential to provide highly efficient thermoelectric materials. These conjugated ligands would allow transport of electrons through the conjugated orbitals. A preliminary characterization of this system, in the bulk, shows an electric conductivity in the region of 24 S.m-1, thermal conductivity 0.10 Wm-1K-1 and a Seebeck coefficient of 4148 muVK-1 at 300 K, with an estimated figure of merit ZT in the region of 0.6. Knowledge of the microscopic conduction rates and mechanisms of these materials would be invaluable in our attempts to improve these materials by design. The present application is to use the uniquely elegant method of Muon spectroscopy to measuring these microscopic properties.