Understanding the electrical transports of p-type polycrystalline SnSe with effective medium theory

Abstract

SnSe crystal is one of the most potential thermoelectric materials due to its excellent transport properties. The electrical conductivity of p-type SnSe crystal gradually decreases with increasing temperature, while that of the polycrystalline sample shows a completely different trend. We revealed that below 400 K, the existence of plentiful grain boundaries dominates the carrier scattering and determines the electrical transport of p-type polycrystalline SnSe, while at high temperatures, from 400 to 800 K, the electrical transport and conductivity curve still requires a clear understanding. In this study, by conducting the high-temperature synchrotron radiation x-ray diffraction (SR-XRD) measurements and refining the patterns, we obtained the phase fractions of Pnma and Cmcm phases in this temperature range. Using the derived single-phase theoretical electrical conductivity, combined with the self-consistent effective medium theory, the electrical conductivity of p-type polycrystalline SnSe between 400 and 800 K was simulated. This study provides a perspective and simulation method to understand the electrical transport of p-type polycrystalline SnSe.

Remarkable electron and phonon transports in low-cost SnS: A new promising thermoelectric material

“…The subdued carrier mobility at low temperatures is ascribed to the strong grain boundary potential barrier in polycrystalline SnS [65]. The grain boundary scattering has also been observed in other polycrystalline thermoelectric systems, such as SnSe [66][67][68], GeSe [69], Mg 3 (Sb,Bi) 2 [70]. Besides, compared with the crystals, the overall carrier mobility is still lower in polycrystalline SnS (apart from the suppressed mobility below ~450 K) in the entire working temperature range, indicating a constant difference in carrier mobility caused by grain boundary.…”

Thermoelectric Property of SnSe Films on Glass Substrate: Influence of Columnar Grain Boundary on Carrier Scattering

“…Carrier scattering is very important for thermoelectric properties. , Scattering by acoustic phonons and optical phonons (nonpolar/polar) and by ionized impurities has been theoretically discussed for SnSe. , Carrier scattering by acoustic phonons, , defects, , and nanopore boundaries has been discussed experimentally. Grain boundaries significantly affect the carrier scattering in polycrystalline SnSe, − as is observed in other thermoelectric materials . Here, the carrier scatterings by the domain and grain boundaries are comparatively analyzed.…”

“…While the grain boundary is formed due to randomly oriented crystal growth, the domain boundary originates from the phase transition. While the importance of the domain boundary on electrical conductivity has been demonstrated, the influence of grain boundaries on carrier transport has been discussed in bulk SnSe. − The scattering effects of grain boundary and domain boundary have been separately discussed, and a comparative study of these effects has not yet been performed. Practical thermoelectric SnSe devices should contain grain boundaries because they consist of SnSe films on amorphous layers.…”

Modulating structures to decouple thermoelectric transport leads to high performance in polycrystalline SnSe

“…Although polycrystalline SnSe possesses comparably low k lat compared to SnSe crystals, it has unavoidable grain-boundary scattering, which greatly hinders carrier transport and reduces carrier mobility. [48][49][50][51] In our previous work, we utilized alloying ternary compounds (AgSbTe 2 , NaSbTe 2 , and NaSbSe 2 ) 52,53 to stabilize the cubic phase of SnSe at ambient temperature and pressure, which exhibit excellent electrical transport properties. The electrical conductivity of the samples aer turning into the cubic phase can reach ∼10 2 S cm −1 , which mainly comes from the signicant increase in carrier concentration (∼10 21 cm −3 ), while the carrier mobility is still as low as ∼1-2 cm 2 V −1 s −1 .…”