A Brief Perspective on Piezotronic and Thermoelectric Coupling: Flexible Platforms for Synergistic Energy Scavenging and Peltier-Caloric Effects

Abstract: Advances in the development of flexible piezoelectric and thermoelectric materials have provided an important avenue for the exploration of energy scavenging through the thermodynamic-coupling of orthogonal energy-scavenging modalities. This has led to a body of work creating hybrid thermo/piezo-electric generator devices (T/PEGs) in which the two effects become thermodynamically entangled. Based on hetero- thin film architectures, such devices can exhibit a surprising power generation characteristic which is non-additive between the two energy-scavenging effects. For example, when the thermoelectric and piezoelectric effects are strongly coupled by their proximal fields, the efficacy of energy scavenging can be made to exceed that of the two effects independently. In this review of such effects, a basic coupled heat engine model is shown to provide insight into the origins of synergistic power generation. These models however, suggest the emergence of other combined thermodynamic properties such as the kinetic Peltier-Caloric Effect (PCE) traced to Onsager reciprocity. The recent observation of this effect in multicomponent systems is confirmation of the limited perspective of thermodynamic separability.