Decoupled electron–phonon transport in Ag2Se thermoelectric materials through constructing TiO2/MoS2 co-decorated cell-membrane-mimic grain boundaries

Ag₂Se has emerged as a promising n-type thermoelectric material; however, its application is limited mainly due to the strongly coupled charge carrier and phonon transport. Enhancing phonon scattering by constructing interfacial complexes often results in low carrier mobility due to its strong carrier scattering resulting from the high energy barrier at the multiphase interface. Inspired by the cell membrane with selective permeability, we construct bio-mimic grain boundaries with TiO₂ and MoS₂ co-decoration in Ag₂Se to decouple electron scattering from strong phonon scattering. The nanostructured TiO₂ with a high dielectric constant screens the interfacial Coulomb potential, ensuring efficient carrier transport and reducing the grain boundary barriers, while the few-layer MoS₂ provides significant phonon scattering to further reduce the thermal conductivity. This method effectively enhances the zT value of Ag₂Se by as much as 60% and also can significantly enhance the theoretical output performance of the thermoelectric device, which highlights the effectiveness of the bio-mimic grain boundary engineering strategy.