Constructing grain boundary complexes for high-efficiency and strengthened Ag2Se thermoelectrics

Decoupling the interrelated thermoelectric parameters is challenging for developing Ag 2 Se-based room temperature thermoelectrics. In this study, we construct specific grain boundary complexes that contain nano-sized TiO 2 and Au particles in Ag 2 Se through a one-step solvothermal process combined with spark plasma sintering. The decorated Ag 2 Se exhibits enhanced power factor due to the increased carrier concentration and maintained carrier mobility, while the introduced broadband phonon scattering effectively reduced thermal conductivity. The decoupled electrical and thermal transport properties result in a high zT value of 1.19 at 390 K in the Ag 2 Se decorated by 0.4 wt.% TiO 2 and 0.5wt.% Au, along with improved mechanical properties. The device assembled by using the optimal sample shows a maximum output power of 65 mW and a maximum energy conversion efficiency of 2.3% under a temperature difference of 80 K. The aging test results highlight the good stability of our devices. Therefore, constructing grain boundary complexes could be a promising strategy for developing practical Ag 2 Se thermoelectrics.