Reconfiguring Lone-Pair Electrons for High-Performance n-Type SnSe Thermoelectrics.

Direct conversion of abundant waste heat into electricity offers a promising route to more efficient energy use, motivating the development of thermoelectric materials with high figure of merit (ZT). In SnSe, Sn 5s2 LPEs are widely recognized as the origin of ultralow lattice thermal conductivity. However, their role in charge transport remains insufficiently understood. Here, by introducing trace Ce3+ that lack stereochemically active LPEs, we reconfigure the collective activity of LPEs in SnSe, thereby enabling robust n-type conduction and enhanced three-dimensional (3D) charge transport through strengthened interlayer orbital overlap and improved carrier mobility. Consequently, Sn0.99Ce0.01Se crystal achieves a peak ZT of ∼3.0 at 745 K and a maximum power-generation efficiency of ∼10.4%. This work establishes a new paradigm for optimizing the thermoelectric performance of materials containing LPEs.