Conduction Bands Manipulation Leads to Promising Thermoelectric Efficiency in n‐Type Mo‐Doped Bi ₂ (Te,Se) ₃

Abstract A high power factor ( PF ) that ensures thermoelectric coolers have excellent cooling temperature difference (Δ T ) and low power consumption, is often hindered by the inherent trade‐offs between electrical parameters. In this study, Molybdenum (Mo) is found to effectively manipulate the conduction bands structure of n‐type Bi ₂ (Te,Se) ₃ (BTS) by directly introducing impurity levels, distorting the density of states near the Fermi level to achieve a large effective mass and Seebeck coefficient. Meanwhile, Mo doping promotes band sharpening and band convergence to further realize the synergistic optimization of carrier mobility and effective mass. In addition, the low carrier concentration caused by the expanded bandgap and regulated defects maintain the low thermal conductivity. Consequently, the Bi ₂ Mo _0.008 Te _2.79 Se _0.21 I _0.004 (BTS+0.8%Mo) sample achieves a PF of ≈52.3 µW cm ⁻¹ K ⁻² and a dimensionless figure‐of merit ( ZT ) value of ≈1.2 at 300 K. Resultantly, the as‐fabricated device achieves a maximum cooling temperature difference (Δ T _max ) of ≈71.4 K at 300 K and a maximum conversion efficiency ( η _max ) of ≈6.0% when Δ T is 200 K. Those observations provide valuable insights for circumventing the limiting inter‐dependencies among thermoelectric parameters, offering a fresh perspective for enhancing the efficiency of various thermoelectric systems.