Low-dimensional materials for thermoelectric applications

In recent years, increasing awareness and concern for energy resources and the environment have stimulated significant advances in materials and technologies for energy conversion. By using a principle called ‘the Seebeck effect’ thermoelectric modules can convert heat energy to electricity. The efficiency of a thermoelectric material is given by the figure of merit ZT = (S2σ/κ) T, where S is the Seebeck coefficient, T is the temperature, and σ and κ are the electrical and thermal conductivities, respectively. An improvement in ZT can be achieved by increasing S−1>σ or reducing κ. However, in three–dimensional (3D) materials, S, >σ and κ are interrelated. By contrast, when dimensionality of materials is lowered down to the nanometre scale, these parameters can be tuned to some extent independently from one another to some extent. This paper reports on some examples of low–dimensional thermoelectric materials with enhanced properties. Various calculation methods used to predict these properties are also presented, and the added value of the calculations as a complement to experiments in the improvement of thermoelectric materials is particularly stressed.