Fig. 1 a SnSe crystal structure Pnma, b electronic band structures of low-temperature (Pnma), c electronic band structures of high-temperature (Cmcm) phases of SnSe. (Adapted with permission from Ref. [13], copyright Springer Nature 2014)

Fig. 2 Atomic-scale point defects (vacancies): a the atomically resolved STEM HAADF image of the matrix, the inset shows the atomic coordinates of a, in red and green are Sn and Se atoms, respectively, b, c the intensity mapping of Se atom and Sn atom columns overlaid on the STEM HAADF image, d, e the intensity mapping of Se and Sn, showing Se vacancies and Sn vacancies. f Total thermal conductivity (κT), g lattice thermal conductivity (κL), h comparison of κL, i calculated κL based on the Callaway’s model. (Adapted with permission from Ref. [80], copyright Creative Commons 2024)

Fig. 3 Microstructural characterizations of PbSe QD/Sn0.965Cd0.025Pb0.01Se: a low-magnification TEM image of high density of PbSe quantum dots, b atomic resolution HAADF-STEM image of PbSe quantum dots. c Schematic diagram of microstructure. d Schematic illustration of microstructural manipulation under high magnetic field. (Adapted with permission from Ref. [87], copyright Elsevier 2021)

Fig. 4 SEM images of a, b Sn0.96Ge0.04Se0.96S0.04 nanorods, c, dsingle nanorod and its elemental mapping. e, f STEM image showing nanorod-like grains. The temperature dependence of g lattice thermal conductivity (κL), h comparison of κL, i ZT, j ZTmax and ZTavg. Mechanical performance of SnSe and Sn0.96Ge0.04Se0.96S0.04 nanorods: k the Vickers microhardness and hardness (H), l compressive stress. (Reproduced from Ref [106]. with permission from the Royal Society of Chemistry.)

Fig. 5 a-h Micro-/nanostructural characterizations of polycrystalline Sn1-xSe. i Calculated spectral lattice thermal conductivity (κs) at 300 K using the Debye-Callaway model. Mechanical performance of polycrystalline Sn1-xSe. j Load-displacement curves. The inset SEM image shows typical nanoindentation. k Elastic modules Er. l Hardness H. m Compressive strength with reported value. The inset photograph shows typical specimens used for the compression tests. (Adapted with permission from Ref. [124], copyright John Wiley and Sons 2022)

Fig. 6 XRD patterns for the SnSe polycrystalline samples before and after texturing process along the directions that are perpendicular a and parallel b to the SPS pressure; the standard pattern of SnSe (PDF# 48-1224) is also plotted for comparison. c, d (111) and (400) pole figures of textured SnSe0.94Br0.06 along the direction that is perpendicular to the SPS pressure. e, f SEM images of the fractured surfaces for textured Sn1.005Se0.94Br0.06 along the two directions. g, h Typical samples for as-SPSed and SPS texturing 3 times, respectively. (Adapted with permission from Ref. [114], copyright Creative Commons 2019)

Fig. 7 Structural characterizations of Sn0.98Pb0.01Zn0.01Se: a HAADF-STEM image of layered grains; b, c HAADF-STEM images of nanoscale precipitates in the interior of grains viewed along [011] and [99] zone axes, respectively; e atomic resolution HAADF-STEM image of nanoscale precipitates in b; f atomic resolution HAADF-STEM image of nanoscale precipitates of yellow square area in c; d EDS maps of Pb with corresponding HAADF-STEM image c. g Phase map of Sn0.99−xPb0.01ZnxSe sample from T-EBSD measurements, which indicates that the SnSe Pnma phase (in blue) and PbSe cubic phase (in red). h Total thermal conductivity (κT), i lattice thermal conductivity (κL) and j ZT as a function of temperature. (Adapted with permission from Ref. [27], copyright Elsevier 2018)

Fig. 8 Nanocomposite construction of phonon scattering centers to enhance the thermoelectric and mechanical properties of SnSe. (Adapted with permission from Ref. [111], copyright American Chemical Society 2024)

Fig. 9 Electronic band structures of SnSe of a Sn0.984Ga0.016Se, Sn0.968Ga0.032Se, and Sn0.952Ga0.048Se. b Carrier concentration (p) and mobility (μ), c Seebeck coefficient (S), d PF and e ZT as a function of temperature. (Adapted with permission from Ref. [25], copyright American Chemical Society 2021)

Fig. 10 Evolution of the band structure of SnSe doped with Ge and S: a Sn24Se24; b Sn23GeSe23S. The color bar scale under the band structure is the number of primitive cell bands spanning the interval (0.05 eV) at a given primitive wave vector. c Electronic density of states of Sn24Se24, Sn24Se23S, Sn23GeSe24, and Sn23GeSe23S. d Comparison of Seebeck coefficient of Sn1-xGexSe1-xSx nanorods with other reported SnSe-based materials. (Reproduced from Ref [106] with permission from the Royal Society of Chemistry.)