High-Performance Thermoelectrics Based on Solution-Grown SnSe Nanostructures

Abstract

Two-dimensional layered tin selenide (SnSe) has attracted immense interest in thermoelectrics due to its ultralow lattice thermal conductivity and high thermoelectric performance. To date, the majority of thermoelectric studies of SnSe have been based on single crystals. However, because synthesizing SnSe single crystals is an expensive, time-consuming process that requires high temperatures and because SnSe single crystals have relatively weaker mechanical stability, they are not favorable for scaling up synthesis, commercialization, or practical applications. As a result, research on nanocrystalline SnSe that can be produced in large quantities by simple and low-temperature solution-phase synthesis is needed. In this Perspective, we discuss the progress in thermoelectric properties of SnSe with a particular emphasis on nanocrystalline SnSe, which is grown in solution. We first describe the state-of-the-art high-performance single crystal and polycrystals of SnSe and their importance and drawbacks and discuss how nanocrystalline SnSe can solve some of these challenges. We illustrate different solution-phase synthesis procedures to produce various SnSe nanostructures and discuss their thermoelectric properties. We also highlight a unique solution-phase synthesis technique to prepare CdSe-coated SnSe nanocomposites and its unprecedented thermoelectric figure of merit (ZT) of 2.2 at 786 K, as reported in this issue of ACS Nano. In general, solution synthesis showed excellent control over nanoscale grain growth, and nanocrystalline SnSe shows ultralow thermal conductivity due to strong phonon scattering by the nanoscale grain boundaries. Finally, we offer insight into the opportunities and challenges associated with nanocrystalline SnSe synthesized by the solution route and its future in thermoelectric energy conversion.

Giant Thermoelectric Efficiency of Single-Filled Skutterudite Nanocomposites: Role of Interface Carrier Filtering

“…Among the various TE materials reported so far, Co 4 Sb 12 -based filled skutterudites are getting considerable attention for their potential thermoelectric applications in the midtemperature range applications (500–750 K). − A series of p- and n-type filled skutterudites with high ZT have been reported. Unfortunately, the highest ZT is achieved only in multiple rare-earth filled skutterudites (1.8 for n-type and 1.6 for p-type) so far. , Single rare-earth filled skutterudites still show lower ZT owing to its higher thermal conductivity, and moderate power factor.…”

Realization of high thermoelectric performance in solution-synthesized porous Zn and Ga codoped SnSe nanosheets

“…Solution-based methods, including the hydrothermal method, 35,36 solvothermal method 37,38 and aqueous solution method, 39,40 usually involve lower reaction temperatures and shorter reaction times. 41 In the solvothermal method, localized lattice distortions, strains, dislocations and nanoscale vacancies have been introduced into Cd-doped SnSe, resulting in a peak ZT of 1.7 at 823 K. 38 SnS 0.1 Se 0.9 nanoplates were obtained by a facile solution synthesis and achieved a peak ZT of 1.16 at 923 K. 42 Solution-processed SnSe–CdSe nanocomposites showed a peak ZT of 2.2 at 786 K by surface engineering. 43 Achieving a high average ZT in a wide temperature range is significant since thermoelectric devices are often required to operate under a large temperature gradient.…”

“…Most SnSe fabricated by solution methods possess high ZT values that are limited to an elevated temperature range but have low average ZT values over the whole temperature range, which results in low thermoelectric power conversion efficiencies. 41 Improvement of the average ZT needs the synergistic optimization of the thermal- and electrical-transport properties over a temperature range as wide as possible. Manipulating porosity has proved to be an effective approach to enhance the phonon scattering.…”

Synthesis of SnSe1–xSx Polycrystals with Enhanced Thermoelectric Properties Via Hydrothermal Methods Combined with Spark Plasma Sintering

“…Zhao et al reported a peak ZT value of 2.6 at 923 K for single crystal SnSe along the b -axis . However, it is difficult for the single crystal SnSe in thermoelectric devices to be applied, considering its poor mechanical properties, high preparation cost, and complex preparation process. , The optimization of thermoelectric properties for polycrystalline SnSe has always been a research hotspot, because of its better application prospects. − The strategies that can enhance the thermoelectric performance are band structure engineering − and microstructure manipulations. − The ZT value was obtained from 0.3 at 773 K to 3.1 at 783 K 2 for p-type polycrystalline SnSe, after nearly a decade of efforts.…”