Abstract: Realizing high performance in both n-type and p-type materials is essential for designing efficient thermoelectric devices. However, the doping bottleneck is often encountered, i.e., only one type of conduction can be realized. As one example, p-type CdSb with high thermoelectric performance has been discovered for several decades, while its n-type counterpart has rarely been reported. In this work, the calculated band structure of CdSb demonstrates that the valley degeneracy is as large as ten for the conduction band, and it is only two for the valence band. Therefore, the n-type CdSb can potentially realize an exceptional thermoelectric performance. Experimentally, the n-type conduction has been successfully realized by tuning the stoichiometry of CdSb. By further doping indium at the Cd site, an improved room-temperature electron concentration has been achieved. Band modeling predicts an optimal electron concentration of ∼2.0 × 10¹⁹ cm^-3, which is higher than the current experimental values. Therefore, future optimization of the n-type CdSb should mainly focus on identifying practical approaches to optimize the electron concentration.

Key words: Thermoelectric materials, n-type CdSb, Indium doping, Band degeneracy