Enhancement of thermoelectric performance in Bi2S3 enabled by pressure-induced electronic topological transition

Achieving superior carrier transport is critical in thermoelectric (TE) materials. However, traditional strategies, such as doping and alloying, always generate a trade-off between carrier concentration and mobility caused by the complex scattering of carriers, limiting the carrier transport properties. Herein, we report a unique high-pressure strategy without introducing scattering centers to optimize carrier transport properties by taking Bi2S3 as an example. The layered nature of Bi2S3 offers a strong response of band structures to pressure. It was found that a unique electronic topological transition emerged under ∼4 GPa revealed by the in situ high-pressure Raman spectra, leading to simultaneous increases in carrier concentration and mobility. This enabled significant enhancement of carrier transport property to boost the electrical conductivity while maintaining a high Seebeck coefficient due to the accompanied large enhancement in the density of states, resulting in a notably improved power factor. Separately, the relatively low thermal conductivity remained due to the preserved layered structure characteristic. Consequently, a record-high figure of merit of 1.05 was achieved at 5 GPa and 744 K, which is higher than those reported state-of-the-art Bi2S3-based thermoelectrics. This study demonstrates the effectiveness of pressure in optimizing carrier transport properties, providing profound insights of high pressure in designing high-performance thermoelectrics.