Building the Principle of Thermoelectric ZT Enhancement
  Thermoelectrics involves both the generation of electrical power from heat flow, and the efficient refrigeration using electricity, which has been intensively focused on for two decades. The performance of thermoelectric power generation and refrigeration has been improved by many proposals since 1993, which is, however, the currently not yet in an industrially competitive level. The development of the entire filed has come to a puzzling point, where the physical reason of why this energy conversion efficiency enhancing problem is barely soluble, and the physical answer of how it should be re-formed to be soluble are the most urgent questions in this field. We here answer these questions and provide the guidance on how to design the of thermoelectric figure of merit enhancement in various systems using different approaches for future researches. We start from criticizing the current way of expression the thermoelectric figure of merit ZT and then introduce the new concept of pseudo-ZT, which can finally make it clear what variables really decides ZT, and clarify the historical misunderstanding of many thermoelectric performance enhancing proposals. Then we explore the most important question on what variables really enhance ZT, and give the contemporary researchers a new guidance on what is the correct direction of thermoelectric performance improving for various systems. 
Shuang Tang, Mildred Dresselhaus
cond-mat.mtrl-sci