Supervisors: Neophytos Neophytou, Julie Staunton

Two thirds of all energy we use is lost into heat during conversion processes, a loss which puts enormous pressure on the planet and energy sustainability. Thermoelectric materials convert waste heat into electricity and can provide a solution towards this problem. This project studies the electronic and thermal properties of complex electronic structure materials subject to a large degree of nanostructuring, which is believed to be the most promising way to achieve extremely high conversion efficiencies. Density function theory methods, as well as semiclassical and quantum transport methods are merged to explore the design space of new generation thermoelectric materials.

The need for energy sustainability and the environmental consequences of the use of fossil fuels make the development of technologies for clean energy generation imperative. Thermoelectric (TE) materials convert waste heat into electricity. As 60% of all energy we use is lost into heat during conversion processes, TE materials could play a major role in energy savings. However, they have not found use in widespread applications yet, because of low efficiencies and high material prices.

Over the last several years, however, highly heterogeneous nanostructured materials have indicated very high performance improvements, based on inexpensive raw materials as well. In these novel material designs, disorder is introduced hierarchically at the atomic scale, the nanoscale (<10nm) and the macroscale. A large variety of materials, such as half-Heuslers, Si, BiTe, PbTe, SnSe and their alloys, polymer compounds, etc., are now under intense experimental investigations.

This project investigates, through theory and large scale simulation, the electronic and thermoelectric performance of hierarchically disordered nanostructured materials and alloys, and optimizes their TE conversion efficiency. A variety of electronic and thermal transport methods (semiclassical and quantum mechanical), as well as a variety of electronic structure methods (DFT, tight-biding, effective mass models) are utilized appropriately in a multi-physics, multi-scale methodology. The aim of the project is to identify the materials and the nanostructured material designs that optimize thermoelectric conversion efficiency. The targeted applications of this technology vary from large scale power generation (heat from industrial process, car exhausts, etc.) to micro-scavenging, i.e. to realize self-powered sensor devices that enable the Internet of Things.