Cooperative Nanostructuring and Resonant Density-of-States Engineering Enable High-Performance n-Type PbSe Thermoelectrics

PbSe is a promising mid-temperature thermoelectric material for low-grade heat harvesting but is fundamentally limited by strong coupling between charge and phonon transport. Here, we report a coordinated nano- and atomic-scale engineering strategy to decouple electronic and phononic transport in n-type PbSe by integrating a nanoscale metallic Pb layer with Ni interstitial doping and Br substitution. Advanced electron microscopy reveals that the embedded Pb layer forms semicoherent interfaces with low-angle grain boundary characteristics, enabling strong phonon scattering while largely preserving carrier mobility. First-principles calculations demonstrate that Ni interstitials introduce a resonant density-of-states feature near the Fermi level, increasing the carrier effective mass and enhancing the Seebeck coefficient without sacrificing the electrical conductivity. As a result, a remarkable peak zT of ∼1.7 at 873 K is achieved in Pb1.01Ni0.015Se0.998Br0.002, accompanied by an exceptional μw/κlat ratio of ∼250 × 10² cm³ W⁻¹ K V⁻¹ s⁻¹ and a high average power factor of ∼2.5 mW m⁻¹ K⁻². A seven-pair thermoelectric device delivers a maximum conversion efficiency of ∼7% and a peak output power density of ∼710 W m⁻² under a temperature difference of 400 K. This work establishes an effective paradigm for cooperatively optimizing electronic and phononic transport in PbSe and other thermoelectrics.