Intrinsic conductivity as an indicator for better thermoelectrics

Abstract

The search for high-performance thermoelectric (TE) materials has long been a focused theme. Herein, the intrinsic conductivity σ₀ is proposed as a simple indicator to evaluate the intrinsic electrical performance of potential TE materials and instruct the exploration of better thermoelectrics. Under the framework of a single parabolic band (SPB) model, σ₀ is proved exactly to be the electrical conductivity of a TE material when its power factor (PF) reaches the maximum value. Moreover, a simplified SPB model is developed, with which simpler mathematical equations can be employed for instructing the optimization of the TE performance, enabling the rapid screening and development of new TE materials. The upper limit of the dimensionless TE figure of merit zT at different temperatures can be easily predicted. Further beyond, with the aim to enhance σ₀, carrier selective scattering engineering is theoretically proposed, with which σ₀ and PF_max could possibly be significantly improved via the selective scattering of low-energy carriers. The experimental routes to realize the carrier selective scattering are also suggested. Finally, a roadmap towards higher σ₀ and zT is summarized, which could provide an insightful understanding and instruction for the future development of thermoelectrics.