Significantly improved thermoelectric performance of SnSe originating from collaborative adjustment between valence and conduction bands, mass fluctuations, and local strain

In this study, environmentally friendly, low cost, and easy to synthesize InSn and VSn co-doped SnSe materials was designed and prepared via vacuum melting and spark plasma sintering technology, which avoids the shortcomings of high-performance Pb, Ge, and Na-doped SnSe samples. InSn and VSn, doping achieved appropriate bandgap (Eg) and energy band degeneracy (NV) from the valence and conduction band, obtaining the highest electrical conductivity of 4726 S m-1 at 773 K. The impurity state controls the carrier transport process below 573 K, while Eg and NV control the process above 573 K. InSn and VSn doping induces quality fluctuation and local strain, which decreases the lattice thermal conductivity. Owing to the higher power factor and low lattice thermal conductivity, the ZT value of the Sn0.985In0.01Se sample was 1.3 at 773 K. Dual regulation of the valence and conduction band provides a new idea for adjusting the transport behavior of semiconductors.

Preparation of Heavily Doped P-Type PbSe with High Thermoelectric Performance by the NaCl Salt-Assisted Approach

Thermoelectric (TE) technology, which can convert scrap heat into electricity, has attracted considerable attention. However, broader applications of TE are hindered by lacking high-performance thermoelectric materials, which can be effectively progressed by regulating the carrier concentration. In this work, a series of PbSe(NaCl)x (x = 3, 3.5, 4, 4.5) samples were synthesized through the NaCl salt-assisted approach with Na+ and Cl− doped into their lattice. Both theoretical and experimental results demonstrate that manipulating the carrier concentration by adjusting the content of NaCl is conducive to upgrading the electrical transport properties of the materials. The carrier concentration elevated from 2.71 × 1019 cm−3 to 4.16 × 1019 cm−3, and the materials demonstrated a maximum power factor of 2.9 × 10−3 W m−1 K−2. Combined with an ultralow lattice thermal conductivity of 0.7 W m−1 K−1, a high thermoelectric figure of merit (ZT) with 1.26 at 690 K was attained in PbSe(NaCl)4.5. This study provides a guideline for chemical doping to improve the thermoelectric properties of PbSe further and promote its applications.