Electron mean-free-path filtering in n-type SnSe for improved thermoelectric performance at room temperature

Based on the fact that the mean free path of phonon is larger than that of the electron, the improvement of ZT could be obtained by adjusting the size of grain boundary. Pushing the size of grain boundary down to the length ranges stated by the electron MFP, both electron transport and phonon transport are affected strongly, but the reduced scale of phonon transport is larger than that of electron transport, leading to the enhancement of ZT. By combining all electron and phonon transport property from full electron-phonon interactions, the room-temperature thermoelectric property of n-type SnSe under different electron/ phonon transport mechanism is evaluated. The h-LO dominates the scattering process of electron transport, while the optic branch controls the scattering process of phonon transport. Compared to the bulk ZT (0.26), the room temperature ZT of 0.62 with the size of 7 nm is obtained, which is nearly three times higher than that of bulk value. Our work not only reveals the enhancement of ZT by the electron filtering effect, but also exhibits the computational framework for accurately calculating the thermoelectric performance under different electron/phonon transport mechanisms.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

By adjusting the size of the grain boundary, the improvement of ZT can be achieved. The thermoelectric performance of SnSe under different electron/phonon transport mechanisms is evaluated by considering the full electron-phonon interactions. Our work reveals the enhancement of ZT through the electron filtering effect and demonstrates a computational framework for accurately calculating thermoelectric performance.