Lead-free SnTe thermoelectrics: Materials design, device engineering, and sustainable energy perspectives

Abstract

This review highlights recent advancements in SnTe-based thermoelectric materials, emphasizing their potential as environmentally friendly alternatives to conventional PbTe systems. SnTe offers several advantages, including a rock-salt crystal structure and favorable electronic band characteristics. However, intrinsic limitations such as high native hole concentration due to Sn vacancies and relatively large lattice thermal conductivity constrain its thermoelectric figure of merit (ZT). This review outlines key strategies to address these challenges, including band convergence via alloying, resonant level doping, carrier concentration optimization, and defect engineering. Methods to reduce lattice thermal conductivity such as nanostructuring and multi-scale phonon scattering are also examined. Advances in doped alloys, hybrid composites, and low-dimensional SnTe systems with ZT values exceeding unity are summarized, highlighting the role of microstructural design. Computational developments, including first-principles modeling, carrier transport analysis, defect chemistry, and emerging machine learning frameworks, are discussed in the context of accelerating material optimization. At the device scale, considerations such as thermoelectric module architecture, contact engineering, thermal/electrical stability, and system-level integration are reviewed. Environmental sustainability, cost-effectiveness, and scalable synthesis routes are evaluated to gauge commercial viability. Current limitations and potential research pathways are presented to support progress in lead-free SnTe thermoelectric technologies.