Chemical Anchoring of Excess Silver and Asymmetric Band Reshaping Enable High-Performance N -Type PbTe Thermoelectrics

While dynamic doping offers a promising route to optimize high-temperature thermoelectric performance, the structural instability and uncontrolled thermal ionization of mobile interstitials fundamentally prevent the essential decoupling of charge and heat transport. To address this, we construct robust spatial traps in n-type PbTe via Ag and Br codoping. Substituted Br atoms chemically anchor interstitial Ag with a relative energy of −56 meV, preventing electromigration and enabling controlled in situ thermal ionization for dynamic carrier regulation. As a direct physical consequence of this strong trapping, the local lattice undergoes a severe distortion, elongating the adjacent Pb–Br bond to 3.57 Å. The resulting local symmetry breaking and dynamic nanophase precipitation generate intense lattice anharmonicity, suppressing the lattice thermal conductivity to a near-amorphous limit of 0.274 W m –1 K –1 . By successfully decoupling electro-thermal transport, the optimized Pb 1.02 Ag 0.01 Te 0.998 Br 0.002 material achieves a peak ZT of 1.65 at 773 K and a high average ZT of 1.33, ranking at the forefront of n-type PbTe systems. An assembled thermoelectric module utilizing this n-type leg delivers a conversion efficiency of ∼9.63% at a temperature difference of 434 K. These results validate local defect chemistry engineering as a reliable strategy to stabilize dynamic dopants for advanced energy conversion.