Abstract

Optimizing the carrier concentration across the entire operating temperature range is crucial for maximizing the power factor in n-type PbTe. However, conventional shallow donors produce a nearly temperature-invariant electron concentration, leading to an increasingly large deviation from the optimal carrier concentration at elevated temperatures. Herein, we implement a dynamic deep-shallow co-doping strategy by combining iodine (a shallow donor) with gallium (a deep-level donor) in PbTe. The Ga-related deep impurity states thermally ionize at elevated temperatures, providing additional electrons and driving the Hall carrier concentration above ~563 K toward its temperature-dependent optimum. Concurrently, our optimized synthesis preserves a high carrier mobility, which synergistically sustains a remarkable peak power factor of 30 μW·cm−1·K−2 for the optimal composition, Ga0.02Pb0.98Te0.996I0.004. Combined with a strongly suppressed lattice thermal conductivity, this results in a maximum figure of merit (ZT) of 1.41 at 803 K and an average ZT of 1.00 within 400–773 K for Ga0.02Pb0.97Te0.996I0.004—a 25% improvement over the I-only doped baseline. These findings establish deep-shallow co-doping as a robust and broadly applicable carrier-engineering paradigm for thermoelectric optimization.

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