Synergistic Optimization of Electronic Structure and Defects via Light Zn-Doping for High Performance n-Type Bi₂(Te, Se)₃ Thermoelectrics in Cooling and Power Generation

The interdependence of electrical parameters has long inhibited the progress of bismuth telluride (Bi_2Te_3), limiting its widespread application in thermoelectric cooling and power generation. This work investigates the\linebreak n-type Bi_2Te_2.79Se_0.21I_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 (\sigma) through the modulation of defect composition and multi-level band regulation. The substitution of Zn atoms at Bi sites enhances S via bandgap (E_\rm 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 \sim1.3 at room temperature. Furthermore, the Bi_2Zn_0.01Te_2.79Se_0.21I_0.004 system demonstrates impressive thermoelectric device performance, with a maximum cooling temperature difference (\Delta T_\max) of \sim70.0 K at 300 K, rising to \sim78.0 K at 323 K and \sim85.7 K at 343 K, as well as a maximum conversion efficiency (\eta_\max) of \sim6.2 % under a \Delta 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.