Optimal Geometric Design of Thermoelectric Metamaterials for Enhancing Power Generation: An Interpretative Approach

Abstract: Thermoelectric metamaterials featuring width modulation through constrictions (constricted geometries) have emerged as a promising approach for improving heat management and thermoelectric performance. Through a combination of theoretical calculations, analytical formalism, and validation against experimental data, it is shown that thermoelectric performance in such geometries is governed by two fundamental mechanisms of pure geometrical origin: (i) a characteristic scaling behavior of resistance with Transmissivity, and (ii) the critical formation of the Constriction Thermal Resistance. Hourglass-shaped thermoelectric legs - identified as optimal in recent experiments - are found to exhibit the same underlying transport mechanisms observed in other constricted profiles, including single and multiple sharp constrictions. The commonly used Geometric Parameter is found to be insufficient for capturing the full influence of geometry on transport, whereas Transmissivity serves as a robust descriptor of constricted geometry, independent of material choice or device operating conditions. A universal scaling formalism is derived linking electrical and thermal resistances, along with key thermoelectric performance metrics, to the Transmissivity. A unified optimization framework is also developed for composite legs, incorporating both constricted material and contact electrodes. This framework indicates that previously reported performance gains may be largely attributed to contact resistance, rather than geometry alone. Transmissivity is established as a key geometric descriptor, enabling generalized design principles and global optimization criteria for enhancing thermoelectric power generation. This analysis elucidates new avenues in the design of thermoelectric metamaterials for efficient energy conversion.