Large Seebeck Effect by Charge-Mobility Engineering

TL;DR

This paper introduces a new mechanism for the Seebeck effect based on charge-carrier mobility changes with temperature, demonstrated in Ni-doped CoSb3, offering insights for designing better thermoelectric materials.

Contribution

It reveals a novel source of the Seebeck effect linked to charge mobility relaxation, expanding understanding beyond electronic density of states engineering.

Findings

Mobility changes can significantly enhance the Seebeck coefficient.

Demonstrated the effect explicitly in Ni-doped CoSb3.

Provides a unifying framework for thermoelectric phenomena.

Abstract

The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. Besides fundamental relevance in solid state physics, it serves as a key quantity to determine the performance of functional thermoelectric materials. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts toward superior thermoelectrics through the engineering of electronic structure. Here, we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: A charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a dramatic mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. As the physical origin for the latter can vary greatly, our proposal provides a unifying framework for the understanding of a large panoply of thermoelectric phenomena. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials for applications in solid-state cooling or power generation.