Simultaneously optimizing power factor and thermal conductivity of <i>n</i>-type PbTe

p-type PbTe is long recognized as an outstanding thermoelectric material in the moderate temperature range, while its n-type counterpart shows relatively poor performance. To address this issue and enhance the thermoelectric properties of n-type PbTe, indium (In) was selected as the dopant to synthesize a series of Pb1−xInxTe (0.03 ≤ x ≤ 0.038) compounds, aiming to regulate the electron concentration and transport characteristics due to the simultaneous increase in electron concentration and mobility, which could be ascribed to the lattice regularization and the reduction of Pb vacancies induced by In doping. As a result, the In-doped compound Pb0.966In0.034Te demonstrated superior thermoelectric performance. Subsequently, Pb0.966In0.034Te/f-CdSe composites were fabricated, and their thermoelectric properties were systematically investigated. The results revealed that In doping significantly increased the electrical conductivity of the materials importantly, and in situ reactions between CdSe and the Pb0.966In0.034Te matrix led to the formation of coherent CdIn2Te4 nanoparticles. The presence of these nanoparticles further enhanced the power factor of the composites across the entire investigated temperature range. Moreover, the lattice thermal conductivity of the composites decreased significantly due to the effective scattering of heat-carrying phonons by point defects and nano-interfaces. Consequently, the sample Pb0.966In0.034Te + 0.7 wt. % CdSe exhibited the optimal thermoelectric performance. At 703 K, its figure of merit (ZT) reached 1.3, representing a 34% increase compared to Pb0.966In0.034Te, and the average ZT reached 0.75. These findings indicate that incorporating CdSe into Pb0.966In0.034Te is an effective strategy to improve the thermoelectric performance of n-type PbTe.