Beyond Substitution on the Role of Ce-Doping in Boosting Thermoelectric Performance of GeTe

Rare-earth (RE) doping shows extensive potential in boosting thermoelectric performance of GeTe-based materials, which are promising candidates for midtemperature thermoelectric applications. However, the low solubility of RE elements in GeTe limits their effectiveness in improving the thermoelectric dimensionless figure of merit ( ZT ). Here, we reveal that the influence of Ce doping in GeTe extends beyond atomic substitution. At low Ce concentrations, a minor amount of Ce can successfully substitute Ge in the GeTe matrix, forming Ce Ge point defects, tuning the carrier concentration. At higher Ce doping levels, the formation of CeTe 2 precipitates introduces interfacial barrier scattering, further reducing the carrier concentration. Through Bi codoping, we achieve a high ZT of 2.0 in Ge 0.95 Ce 0.01 Bi 0.04 Te. This study provides insight into the multifaceted effects of RE doping on the thermoelectric performance of GeTe-based materials.