Boosting\nthe Thermoelectric Properties of Ge<sub>0.94</sub>Sb<sub>0.06</sub>Te via Trojan Doping for High Output Power

GeTe\nstands as a promising lead-free medium-temperature thermoelectric\nmaterial that has garnered considerable attention in recent years.\nSuppressing carrier concentration by aliovalent doping in GeTe-based\nthermoelectrics is the most common optimization strategy due to the\nintrinsically high Ge vacancy concentration. However, it inevitably\nresults in a significant deterioration of carrier mobility, which\nlimits further improvement of the <i>zT</i> value. Thus,\nan effective Trojan doping strategy via CuScTe<sub>2</sub> alloying\nis utilized to optimize carrier concentration without intensifying\ncharge carrier scattering by increasing the solubility of Sc in the\nGeTe system. Because of the high doping efficiency of the Trojan doping\nstrategy, optimized hole concentration and high mobility are obtained.\nFurthermore, CuScTe<sub>2</sub> alloying leads to band convergence\nin GeTe, increasing the effective mass <i>m</i>* in (Ge<sub>0.84</sub>Sb<sub>0.06</sub>Te<sub>0.9</sub>)­(CuScTe<sub>2</sub>)<sub>0.05</sub> and thus significantly improving the Seebeck coefficient\nthroughout the measured temperature range. Meanwhile, the achievement\nof the ultralow lattice thermal conductivity (<i>κ</i><sub>L</sub> ∼ 0.34 W m<sup>–1</sup> K<sup>–1</sup>) at 623 K is attributed to dense point defects with mass/strain-field\nfluctuations. Ultimately, the (Ge<sub>0.84</sub>Sb<sub>0.06</sub>Te<sub>0.9</sub>)­(CuScTe<sub>2</sub>)<sub>0.05</sub> sample exhibits\na desirable thermoelectric performance of <i>zT</i><sub>max</sub> ∼ 1.81 at 623 K and <i>zT</i><sub>ave</sub> ∼ 1.01 between 300 and 723 K. This study showcases an effective\ndoping strategy for enhancing the thermoelectric properties of GeTe-based\nmaterials by decoupling phonon and carrier scattering.