Resonant Levels Induced Seebeck Coefficient Matching Contributes to High Thermoelectric Cooling Efficiency in p‐type SnSe Crystals

Abstract Tin selenide (SnSe) has emerged as a promising thermoelectric cooling candidate, exhibiting room‐temperature performance comparable to that of commercial bismuth telluride (Bi 2 Te 3 ). However, the Seebeck coefficient of p‐type SnSe crystals remains significantly lower than that of n‐type Bi₂(Te, Se)₃ (BTS), and the resulting mismatches hinder effective utilization of its excellent cooling potential. To address this limitation, resonant levels are introduced in the valence bands of hole‐doped SnSe through indium‐doping, which increased the density of states and thereby boosted the Seebeck coefficient. This strategy enable the power factor to reach ≈55 µWcm −1 K −2 and ZT value of ≈1.0 at 300 K, with a more matching Seebeck coefficient of ≈211 µVK −1 . Furthermore, a full‐scale thermoelectric cooler incorporating the p‐type SnSe paired with n‐type BTS demonstrated a maximum cooling temperature difference (Δ T max ) of ≈81.1 K at 343 K. A SnSe‐based single‐leg device achieve a conversion efficiency of ≈7.0% under a Δ T of 250 K. These findings highlight that matching thermoelectric parameter of p‐type and n‐type materials is crucial for enhancing the cooling efficiency of devices, and engineering resonant energy levels constitutes a robust strategy for solving the inherent performance limitations of p‐type SnSe in practical thermoelectric applications.