1 Thermoelectric properties of Bi 2 Te 3 : CuI and the effect 2 of its doping with Pb atoms 3

In order to understand the effect of Pb-CuI co-doping on the thermoelectric performance 8 of Bi2Te3, n-type Bi2Te3 co-doped with x at% CuI and 1/2x at% Pb (x = 0, 0.01, 0.03, 0.05, 0.07, and 9 0.10) were prepared via high temperature solid state reaction and consolidated using spark plasma 10 sintering. Electron and thermal transport properties, i.e., electrical conductivity, carrier 11 concentration, Hall mobility, Seebeck coefficient, and thermal conductivity, of CuI-Pb co-doped 12 Bi2Te3 were measured in the temperature range from 300 K to 523 K and compared to 13 corresponding x% of CuI-doped Bi2Te3 and undoped Bi2Te3. The addition of a small amount of Pb 14 significantly decreased the carrier concentration, which could be attributed to the holes from Pb 15 atoms, thus the CuI-Pb co-doped samples show a lower electrical conductivity and a higher 16 Seebeck coefficient compared to CuI-doped samples with similar x values. The incorporation of Pb 17 into CuI-doped Bi2Te3 rarely changed the power factor because of the trade-off relationship 18 between the electrical conductivity and the Seebeck coefficient. The total thermal conductivity(κtot) 19 of co-doped samples (κtot ~1.4 W/m∙K at 300 K) is slightly lower than that of 1% CuI-doped Bi2Te3 20 (κtot~1.5 W/m∙K at 300 K) and undoped Bi2Te3 (κtot ~1.6 W/m∙K at 300 K) due to the alloy scattering. 21 The 1% CuI-Pb co-doped Bi2Te3 sample shows the highest ZT value of 0.96 at 370 K. All data on 22 electrical and thermal transport properties suggest that the thermoelectric properties of Bi2Te3 and 23 its operating temperature can be controlled by co-doping. 24