Realizing high-performance thermoelectric modules through enhancing the power factor via optimizing the carrier mobility in n-type PbSe crystals

The limited availability of Te poses challenges for the widespread application of Bi₂Te₃-based thermoelectric modules. In this work, we explored the thermoelectric module potential of Te-free PbSe by elevating its power factor through crystal growth and slight-tuning vacancy and interstitial defects. The outcomes revealed a gradual increase in the carrier concentration and a high room-temperature carrier mobility of ∼1750 cm² V⁻¹ s⁻¹, leading to an enhanced power factor of ∼37.4 μW cm⁻¹ K⁻² in Pb_1.006Se+0.0016 Al crystals. We grew PbSe crystals to minimize the impact of grain boundaries on the charge carrier transport. Subsequently, n-type PbSe crystals were produced by introducing extra Pb to occupy the intrinsic Pb vacancies, effectively minimizing vacancy scattering. Following this, a minute quantity of small-sized Al (≤2‰) was introduced, revealing that these surplus Al atoms served as cationic dopants, substituting for Pb, while also occupying interstitial positions. The interstitial doping increases the carrier concentration while maintaining carrier mobility due to the distinct dimensions between the interstitial atoms and mean free path of electrons. The consistently improved power factor with the suppression of thermal conductivity brings about a significantly high ZT value over the whole temperature. Specifically, the ZT values of the Pb_1.006Se+0.0016Al crystal reached ∼0.5 at 300 K, ∼1.5 at 673 K, and the average ZT (ZT_ave) reached ∼1.1 at 300-773 K. Ultimately, a single-leg power generation efficiency ∼7.1% was achieved in Pb_1.006Se+0.0016Al crystal and a 7-pair module reached a maximum temperature cooling difference ∼51.2 K at the high temperature side T_h of 363 K. These results indicate the potential for developing a cost-effective and high-performance thermoelectric module utilizing PbSe.