Mechanically Robust Dicing-Free Thermoelectric Module Fabrication Using Anion-Cation co-Doped Bismuth Tellurides

We present a thermoelectric performance enhancement by anion-cation co-doping in p-type bismuth tellurides with a cost-effective and mechanically robust thermoelectric module fabrication process. Polycrystalline (BST)_{1 - x}(NaCl)_x (0 ≤ x ≤ 5.0 mol%) samples were synthesized via melting and hot-press sintering, and their anisotropic transport properties were investigated. At low NaCl concentrations, Na⁺ and Cl^- act as effective substitutional dopants, optimizing carrier concentration and mobility while suppressing bipolar thermal conduction via local lattice strain. At higher NaCl contents, nanoscale precipitates form, providing additional phonon scattering without degrading electronic transport. Consequently, a maximum ZT ≈ 1.49 at 350 K and an average ZT_avg ≈ 1.4(300-425 K) were achieved. In parallel, a mechanically robust module architecture using an electrically insulating, low-thermal-conductivity PEEK support eliminates wafering and dicing processes. A 31-pair module fabricated with optimized p-type (BST)_{1 - x}(NaCl)_x and n-type (CuI)_0.3 Bi₂ Te_2.7 Se_0.3 materials exhibit competitive thermoelectric performance to that of commercial Bi₂ Te₃-based modules. These results demonstrate a pathway toward economically competitive and mechanically robust next-generation thermoelectric modules.