Lattice Plainification and Intercalation Advances Power Generation and Thermoelectric Cooling in n‐type Bi2(Te, Se)3

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Bismuth telluride (Bi2Te3) has been the only commercialized material in thermoelectric cooling and waste heat recovery. However, the inferior performance for n‐type Bi2(Te, Se)3 largely restricts the practical applications. In this study, additional Ag atoms are introduced utilizing lattice plainification strategy to enhance electrical performance. Observations indicate that Ag atoms situate in the van der Waals layers, acting as n‐type dopants to increase carrier concentration, bonding with adjacent Te as intercalating atoms to form electron transport channels, while also suppressing the formation of Te vacancies to boost carrier mobility, substantially favoring carrier transport. Consequently, Bi2Te2.79Se0.21I0.004+0.3%Ag achieves an excellent room‐temperature ZT of ≈1.1, while Bi2Te2.79Se0.21I0.004 + 0.4%Ag demonstrates a higher average ZT of ≈1.1 at 300–523 K. Furthermore, a full‐scale thermoelectric cooler using optimized Bi2Te2.79Se0.21I0.004+0.3%Ag combined with commercial p‐type Bi0.5Sb1.5Te3 has achieved a maximum cooling temperature difference (ΔTmax) of ≈68.3 K at 300 K and a larger ΔTmax of ≈84.8 K at 343 K. Additionally, the Bi2Te2.79Se0.21I0.004 + 0.4%Ag/Bi0.5Sb1.5Te3‐based power generator realizes a conversion efficiency of ≈6.0% under a ΔT of ≈240 K. These results outperform commercial Bi2Te3‐based devices, illustrating the effectiveness of lattice plainification for Bi2Te3‐based thermoelectrics.