Transition metal dichalcogenides: highly stable barrier layers for telluride thermoelectrics

Tellurides exhibit excellent thermoelectric performance at low and medium temperatures, yet their practical application is constrained by the lack of reliable barrier materials. In this work, we propose transition metal dichalcogenides (TMDs) as effective barrier layers for tellurides. The two-phase equilibrium in TMDs suppresses interfacial reactions, while their intrinsically low elastic modulus mitigates stress arising from mismatched thermal expansion coefficients. Among the candidates, TiTe₂ and Ta_0.5Ti_0.5Te₂ were identified as suitable barrier layers for bismuth telluride and germanium telluride, respectively. After aging at 523 K and 773 K for 60 days, both interfaces remained stable without noticeable diffusion or reaction, and their contact resistivities were maintained at approximately 5.5 μΩ cm² and below 1 μΩ cm². Furthermore, TiTe₂ was employed as an interlayer between GeTe and Bi₂Te₃, simultaneously relieving internal stress and effectively blocking elemental interdiffusion at the interface. The resulting two-pair segmented thermoelectric module achieved a high conversion efficiency of 11% under a temperature difference of 380 K. This study offers a new paradigm for designing barrier materials for telluride and, more broadly, chalcogenide thermoelectric systems, paving the way toward fully realizing their thermoelectric conversion potential.