Enhancing thermoelectric performance of solution-processed polycrystalline SnSe with PbSe nanocrystals
Yu Liu, Seungho Lee, Christine Fiedler, María Chiara Spadaro, Cheng Chang, Mingquan Li, Min Hong, Jordi Arbiol, María Ibáñez
Abstract
There is a growing interest in cost-effective polycrystalline SnSe-based thermoelectric (TE) materials able to replace the high performance but mechanically fragile and costly single-crystalline SnSe. In this study, we present a low-temperature solution-based approach to produce SnSe-PbSe nanocomposites with outstanding TE performance. Our method involves combining surfactant-free SnSe particles with oleate-capped PbSe nanocrystals in specific ratios, followed by thermal annealing and consolidation using spark plasma sintering. These nanocomposites are characterized by distinct compositional and structural properties that significantly impact their transport properties. In particular, the addition of oleate-capped PbSe nanocrystals results in: i) a reduction in the electrostatically adsorbed Na at the surface of the SnSe particles; ii) a reduction of Sn vacancies due to alloying with Pb; iii) an increase in grain boundary density; and iv) the formation of PbSnSe secondary phases. Notably, the SnSe-2.5 %PbSe nanocomposites demonstrate a 30 % decrease in thermal conductivity compared to that of the SnSe matrix. This reduction contributes to TE figures of merit up to zTmax = 1.75 at 788 K with a high average zT value of ca. 1.2 in the medium temperature range of 573–773 K. These values represent one of the highest reported in polycrystalline SnSe, showcasing the potential of our fabricated SnSe-PbSe nanocomposites for cost-effective TE applications.