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

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 Pb_1.01Ni_0.015Se_0.998Br_0.002, accompanied by an exceptional μ_w/κ_lat 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.