Intrinsic Electronic Quality and Compatibility-Factor-Driven Design of Thermoelectric Materials Across Temperature Regimes

Abstract

Thermoelectric energy conversion requires materials that combine high intrinsic performance with effective integration into devices. In this study, 'intrinsic performance' is defined as the inherent ability of a material to efficiently convert heat into electricity, characterized by parameters like the Seebeck coefficient and electrical conductivity. In contrast, 'device-level efficiency' refers to the performance of a thermoelectric material when integrated into a device, considering factors such as current matching and compatibility. To identify optimal candidates across low-, mid-, and high-temperature regimes, the present study integrates experimental transport property data with electronic descriptors, such as the electronic quality factor (BE) and Slack’s material quality factor (B). These analyses are complemented by three-dimensional finite-element simulations of thermoelectric devices. This comprehensive methodology enables temperature- and device-specific performance rankings, which inform targeted optimization strategies. The results demonstrate that high power output does not necessarily equate to high efficiency. For instance, half-Heusler ScCoSb and SiGe alloys achieve the highest power at elevated temperatures but are constrained by poor compatibility factors and current-matching limitations. In contrast, traditional chalcogenides such as Bi₂Te₃ and Bi₂SbTe₃ exhibit superior intrinsic electronic properties at lower temperatures, resulting in higher conversion efficiencies within this range. A newly synthesized Ho-Sb-Te alloy demonstrates potential for mid-temperature applications by leveraging low lattice thermal conductivity, achieving competitive performance despite moderate electronic quality. These findings underscore the importance of compatibility factor matching in segmented thermoelectric generators, as mismatches can significantly reduce efficiency even when individual zT values are high. By integrating BE, B, and compatibility factors with device-level modeling, this study advances beyond conventional zT-centric screening and establishes principles for material selection and segmented device design. This approach provides a strategic framework for optimizing thermoelectric generators across diverse operating temperatures, thereby supporting the development of waste-heat recovery and solid-state cooling systems with enhanced efficiency.