Advances in Polycrystalline P-type SnSe for Thermoelectric Applications

Approximately two-thirds of the energy utilized globally is lost as heat in the atmosphere.¹ The role of thermoelectric materials is gaining more attention to recycle this lost energy, especially in light of the increased worldwide projection for energy demand. Unfortunately, the conversion efficiency of thermoelectric applications averages around 5-10%, which raises concern regarding the ability to expand these applications on a wider scale.² Conversion efficiency in thermoelectric applications is dependent on the temperature gradient used and the dimensionless figure of merit (ZT) of the p-type and n-type materials in the system.³ To enhance efficiency, current research is focused on enhancing the ZT of potential materials, specifically by suppressing lattice thermal conductivity, while enhancing the Seebeck coefficient and electrical conductivity.¹ In the past two decades, a number of materials have been studied as candidates for thermoelectric applications due to their large ZT values, including single crystal tin selenide, which was recently discovered to hold a world record ZT of 2.62 at 973K.^1,4 Although significant, there are practical disadvantages to single crystal systems, including the costliness to grow large crystals and the lack of scalability.^5-7 Given these setbacks, a resurgence of interest has ignited in optimizing bulk polycrystalline tin selenide, which has a reported peak ZT of 0.5 at 823 K.⁸ This talk will focus on the increase of ZT in polycrystalline p-type tin selenide with an emphasis on suppressing lattice thermal conductivity through different approaches such as doping/mechanical alloying⁵, secondary phase nanostructuring⁶, and vacancy formation⁷.

1. Tan, G.; Zhao, L.-D.; Kanatzidis, M. G. Chem. Rev. 2016, 116 (19), 12123–12149.
2. Andrei, V.; Bethke, K.; Rademann, K. Energy Environ. Sci. 2016, 9 (5), 1528–1532.
3. Kim, H. S.; Liu, W.; Chen, G.; Chu, C.-W.; Ren, Z. Proc. Natl. Acad. Sci. 2015, 112 (27), 8205–8210.
4. Zhao, L.-D.; Lo, S.-H.; Zhang, Y.; Sun, H.; Tan, G.; Uher, C.; Wolverton, C.; Dravid, V. P.; Kanatzidis, M. G. Nature 2014, 508 (7496), 373–377.
5. Chen, Y.-X.; Ge, Z.-H.; Yin, M.; Feng, D.; Huang, X.-Q.; Zhao, W.; He, J. Adv. Funct. Mat. 2016, 26 (37), 6836–6845.
6. Tang, G.; Wei, W.; Zhang, J.; Li, Y.; Wang, X.; Xu, G.; Chang, C.; Wang, Z.; Du, Y.; Zhao, L.-D. J. Am. Chem. Soc. 2016, 138 (41), 13647–13654.
7. Wei, W.; Chang, C.; Yang, T.; Liu, J.; Tang, H.; Zhang, J.; Li, Y.; Xu, F.; Zhang, Z.; Li, J.-F.; Tang, G. J. Am. Chem. Soc. 2018, 140 (1), 499–505.
8. Sassi, S.; Candolfi, C.; Vaney, J.-B.; Ohorodniichuk, V.; Masschelein, P.; Dauscher, A.; Lenoir, B. Appl. Phys. Lett. 2014, 104 (21), 212104-212105.