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

Tin selenide (SnSe) has emerged as a promising thermoelectric cooling candidate, exhibiting room-temperature performance comparable to that of commercial bismuth telluride (Bi₂Te₃). 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^-1K^-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 (ΔT_max) of ≈81.1 K at 343 K. A SnSe-based single-leg device achieve a conversion efficiency of ≈7.0% under a ΔT 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.