Two-dimensional WSe2/SnSe p-n junctions secure ultrahigh thermoelectric performance in n-type Pb/I Co-doped polycrystalline SnSe

In this study, we, for the first time, introduce p-type two-dimensional (2D) WSe2 nanoinclusions in n-type Pb/I co-doped SnSe matrix to form WSe2/SnSe p-n junctions. These p-n junctions act as energy barriers and effective phonon scattering sources, leading to a high figure-of-merit (ZT) of similar to 1.35 at similar to 790 K in n-type polycrystalline SnSe. First-principles density functional theory calculation results indicates that I-doping shifts Fermi level up into conduction bands of SnSe, making the system n-type behavior, while both Pb and I dopants act as point-defect-based short-wavelength phonon scattering centers. The introduced p-type 2D WSe2 nanoinclusions induce high-density WSe2/SnSe interfaces that act as p-n junctions, which block the electron carriers and rationally tune the carrier density, contributing to a high absolute Seebeck coefficient of similar to 470.7 mV K-1 and a high power factor of similar to 5.9 mW cm(-1) K-2. Meanwhile, the dense phase boundaries and considerable lattice strains by the introduced 2D WSe2 nanoinclusions significantly strengthen the mid- and long-wavelength phonon scattering, giving rise to a much low thermal conductivity of 0.35Wm(-1) K-1 and in turn a high ZT of similar to 1.35. This study provides a new strategy to achieve high thermoelectric performance in n-type polycrystalline SnSe. Crown Copyright (C) 2020 Published by Elsevier Ltd. All rights reserved.

Automated summary

This study introduces p-type two-dimensional WSe2 nanoinclusions into n-type polycrystalline SnSe for the formation of p-n junctions, resulting in enhanced thermoelectric performance through phonon scattering and Fermi level control.