Synergistic Optimization of Electronic Structure and Defects via Light Zn-Doping for High Performance n-Type Bi ₂ (Te, Se) ₃ Thermoelectrics in Cooling and Power Generation

Abstract The interdependence of electrical parameters has long inhibited the progress of bismuth telluride (Bi 2 Te 3 ), limiting its widespread application in thermoelectric cooling and power generation. This work investigates the n-type Bi 2 Te 2.79 Se 0.21 I 0.004 (Bi 2 (Te, Se) 3 , BTS) system with light Zn doping, revealing that Zn addition simultaneously enhances the Seebeck coefficient ( S ) and electrical conductivity ( σ ) through the modulation of defect composition and multi-level band regulation. The substitution of Zn atoms at Bi sites enhances S via bandgap ( E g ) widening, band flattening, and band splitting effects, contributing to a competitive power factor ( PF ) of ∼60 μW⋅cm −1 ⋅K −2 . Additionally, thermal conductivity is maintained at a low level, leading to an extraordinary figure-of-merit ( ZT ) value of ∼1.3 at room temperature. Furthermore, the Bi 2 Zn 0.01 Te 2.79 Se 0.21 I 0.004 system demonstrates impressive thermoelectric device performance, with a maximum cooling temperature difference (Δ T max ) of ∼70.0 K at 300 K, rising to ∼78.0 K at 323 K and ∼85.7 K at 343 K, as well as a maximum conversion efficiency ( η max ) of ∼6.2% under a Δ T of 200 K. This study clarifies the mechanism of Zn doping and presents a cost-effective strategy for enhancing the performance of n-type BTS thermoelectrics and their devices.