Regensburg 2013 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 24: Thermoelectric Materials

DS 24.9: Vortrag

Mittwoch, 13. März 2013, 16:45–17:00, H32

The ineffectiveness of energy filtering at grain boundaries for thermoelectric materials — •Michael Bachmann, Michael Czerner, and Christian Heilger — I. Physikalisches Institut, Justus Liebig University Giessen, D-35392, Germany

We present results that show the ineffectiveness of energy filtering at grain boundaries [1]. Our results are based on a model that we developed to describe electron transport in nanograined materials. For the band structure we use a one band effective mass model. The transport is calculated using the Landauer formalism. The grain boundaries are described using the model by Seto [2]. In this model additional trapping states in the grain boundary are assumed that causes a space charge accumulation in the grain boundary. This space charge distribution leads to a formation of a double Schottky barrier. It is believed that such barriers can increase the efficiency of thermoelectric materials by energy filtering effects. Since in our model the space charge distribution depends on the doping concentration and therefore also the barrier, we are able to calculate the electron transport in dependence of the doping concentration. For low doping concentration we obtain a energy filtering effect, but for high doping concentration that are necessary for effective thermoelectric material the barrier height and width is too small to have an impact on the transport. Therefore, we conclude that electrostatic barriers play no role for thermoelectric devices.

[1] M.Bachmann, M. Czener and C.Heiliger, Phys. Rev. B 86, 115320 [2] J. Seto, J.Appl. Phys. 46 5247 (1975)