Investigation on thermoelectric performance degradation of In-doped Cu0.008Bi2Te3 induced by bandgap and carrier mobility reduction
摘要
In this study, thermoelectric transport properties of In-doped Cu0.008Bi2Te3 (Cu0.008Bi2-xInxTe3, x = 0, 0.01, 0.03, 0.05, 0.07, 0.10, and 0.15) polycrystalline alloys were investigated. The carrier concentration was gradually increased by the In doping from 4.3 × 1019 to 8.5 × 1019 cm−3 at 300 K, and the carrier mobility was also significantly decreased from 224 to 74 cm2/Vs at 300 K. It was also revealed that the measured optical bandgap of Cu0.008Bi2Te3 gradually reduced from 0.43 to 0.14 eV by the in doping. As a result, Seebeck coefficient and electrical conductivity of the In-doped samples decreased simultaneously, and thus the power factor decreased significantly from 2.63 to 0.55 mW/mK2 at 300 K. Nevertheless, the lattice thermal conductivity decreased from 1.1 to 0.73 W/mK by 35% at 300 K owing to the additional point defect scattering by the In doping. As a result, the thermoelectric figure-of-merit zT of Cu0.008Bi2Te3 is decreased from 0.41 to 0.12 at 300 K due to rather significant power factor decrease originated by the bandgap and carrier mobility reduction by the in doping. In addition, the degradation of the power factor and zT is further analyzed by single parabolic band model.