High conversion efficiency of a thermoelectric generator attributed to consistency of material parameters

Thermoelectric (TE) material parameters are well known to have strong temperature dependency. However, there is a paucity of descriptors to assess their temperature-related trends during power generation. Here, we emphasize the importance of relative standard deviation (RSD) of electric current density in evaluating TE materials. For materials with identical average TE figure of merit, the one with lower RSD has higher conversion efficiency due to its consistency in power generation. This metric offers a direct approach to screen various TE materials for efficient thermoelectric generators (TEGs). To verify theoretical results, we fabricated two TEGs using distinct TE materials with varying RSDs and obtained higher conversion efficiency in the TEG constructed using materials with lower RSDs. This discovery forms a solid foundation for evaluating and screening high-performance TE materials.