Thin-film thermoelectric devices for energy harvesting and material parameter extraction

A major barrier for a wider use of thermoelectric devices for energy harvesting is their low efficiency, which tends lead to a high cost per converted power. The ability to use non-toxic and abundant materials has also become increasingly important in the recent years and enhanced the interest towards improving the thermoelectric properties of metal oxides. Tin-doped indium oxide (ITO) is one of the most commonly used transparent conductive oxides due to its high electrical conductivity and high transparency. However, aluminum-doped zinc oxide (AZO) provides an environmentally friendly alternative that is more abundant, has better thermoelectric properties and lower cost. In this work, we present selected results of our thermoelectric device development based on AZO aiming at flexible thin-film TEG applications. Thermodynamic modelling and performance simulations are conducted for selected designs in order to estimate the available thermal gradients, the performance of the thermoelectric elements and the power available from the thermoelectric modules consisting of various geometries and configurations [1]. In addition to the electrical properties, the heat transfer mechanisms over the modules are studied. In addition to the conventional material characterizations, the potential of the materials is also evaluated by constructing experimental test devices of the thin-films and building corresponding simulation models of the test devices. By combining the experimental and theoretical approaches through device evaluations, the optimization of the thin-film materials and device designs can be performed in parallel for constructing a large-area thermoelectric module for thermal energy harvesting applicable in various environments without elaborated heat sinks. The ultimate goal of the project is to build a distributed sensor network integrating large-area thin-film thermoelectric devices and sensors for multifunctional smart windows and flexible high impact volume applications.