Priority Program 1386: Nanostructured Thermoelectric Materials: Theory, Model Systems and Controlled Synthesis

Nanostructuring is nowadays considered as a promising strategy towards the development of thermoelectric materials of high efficiency ZT. Although the three transport parameters contributing to Z=S2σ/λ (the Seebeck coefficient S as well as the electric and thermal conductivities σ and λ) are directly interrelated with one another in bulk materials, accurate structuring on the nanometer scale enables one to tune each of them to some extent independently of each other. With the strategic goal to transform the manifest potential of nanoscale thermoelectrics into practical applicability, the Priority Programme will address the following questions:

(1) Can the thermoelectric efficiency of nanostructured model systems be computed theoretically with sufficient accuracy to steer the experimental material development?

(2) Which real systems can be chosen as model systems in order to achieve a feedback between theory and experimental controlled engineering (via chemical and physical methods)? How can thermoelectric model systems nanostructured "vertically" and "horizontally" be built and characterised structurally?

(3) How does the measurement technique be designed for the model systems in order to provide widely accepted reference data? Which experimental methods can provide insight into the thermoelectric transport phenomena in nanostructures?

This Priority Programme will substantially contribute to fill this gap on the international level. Therefore, activities will be supported in the following three competence areas (KB):

KB 1: The development of well-defined experimental model systems in which each of the basic thermoelectric properties can be manipulated by chemical, electrochemical or physical methods, whereby either the principles of phonon barriers or the tuning of the band structure are exploited. The model systems must consist of well-characterisable nanostructures, such as epitaxial multilayers, nanowires, quantum wells or monodisperse nanoparticles.

KB 2: The structural and thermoelectric characterisation methods able to provide a better understanding of the transport phenomena on the nanometer scale. Projects may focus on the measurement technique itself, the carrying out of measurements, or the preparative aspects directly related to the measurement.

KB 3: The development of solid-state theoretical models that significantly improve the understanding of transport phenomena in model systems. Among possible project topics are finite elements methods and ab initio computations based on density functional theory or other analytical solutions, in any case with the goal of facilitating material design. A particularly challenging aspect in the modelling of thermoelectric nanostructures is the simultaneous handling of a wide range of length scales.