Advanced Thermoelectric Power Modules Employing n-Type Ag2Se Synthesized via a Sustainable Route

Thermoelectric (TE) Ag2Se was synthesized via an energy-efficient, solution-based chemical synthesis route with microwave-assisted heating and compacted by sustainable cold pressing. Structural and TE transport property analyses confirmed a highly crystalline microstructure that promotes high electrical conductivity, a large Seebeck coefficient, and low thermal conductivity, yielding a peak TE figure of merit (ZT) of ∼0.85 at room temperature. To evaluate device-level performance, Ag2Se was employed as the n-type TE leg in modules paired with Sb1.5Bi0.5Te3 (ZT ∼1.1 at 325 K) as the complementary p-type TE leg. Both rigid and flexible modules, each containing 58 thermocouple pairs, were fabricated and benchmarked against a commercial TEC1-12706 module. The rigid module exhibited more than four times the maximum power output of the commercial reference, highlighting the promise of Ag2Se for low-temperature TE power applications. Cooling performance tests demonstrated the critical influence of electrical configuration. Series-connected rigid modules achieved the lowest cold-side temperatures at lower input power, reaching ∼2 °C at 18 W, comparable to or exceeding the cooling performance of the commercial device. In contrast, parallel-connected modules exhibited stronger initial cooling but were hindered by excessive current draw, Joule heating, and thermal instability, preventing stable saturation. Increasing input power would enhance cooling performance until saturation limits were reached. These results emphasize the importance of module architecture and thermal management for optimizing TE device performance. Overall, this work establishes Ag2Se as a promising alternative to conventional Bi-Sb-Te-based n-type materials, demonstrating versatility in both rigid and flexible TE modules for energy harvesting and cooling technologies.