High Thermoelectric Performance in Cu-Doped Bi₂Te_2.7Se_0.33 Due to Cl Doping and Multiscale AgBiSe₂

The thermoelectric performance of n-type Bi₂Te₃ needs further enhancement to match that of its p-type Bi₂Te₃ counterpart and should be considered for competitive applications. Combining Cu/Cl and multiscale additives (AgBiSe₂) presents a suitable route for such enhancement. This is evidence of the enhanced thermoelectric performance of Bi_1.995Cu_0.005Te_2.69Se_0.33Cl_0.03. Moreover, by incorporating 0.65 wt % AgBiSe₂ (ABS) into Bi_1.995Cu_0.005Te_2.69Se_0.33Cl_0.03, we further reduce its lattice thermal conductivity to ∼0.28 W m^-1 K^-1 at 353 K owing to the extra phonon scattering of multiscale ABS. Additionally, the Seebeck coefficient enhances (-183.89 μV K^-1 at 353 K) owing to the matrix's reduced carrier concentration caused by ABS. As a result, we achieve a high ZT of ∼1.25 (at 353 K) and a high ZT_ave of ∼1.12 at 300-433 K for Bi_1.995Cu_0.005Te_2.69Se_0.33Cl_0.03 + 0.65 wt % ABS. This work provides a promising strategy for enhancing the thermoelectric performance of n-type Bi₂Te₃ through Cu/Cl doping and ABS incorporation.