Introducing PbSe quantum dots and manipulating lattice strain contributing to high thermoelectric performance in polycrystalline SnSe

Here, a p-type polycrystalline SnSe integrated with PbSe quantum dots is fabricated by an in situ magnetic field-assisted hydrothermal route. The decrease of the critical nucleation free energy and increase of homogeneous nucleation rate lead to the formation of PbSe quantum dots under high magnetic field. The enhanced density of states due to PbSe quantum dots causes significantly enhanced Seebeck coefficients and power factor. A large integral area of power factor over the full temperature range is optimized. The lattice strain induced by dislocations and stacking faults shortens the phonon relaxation time, leading to an ultralow lattice thermal conductivity (0.32 W m−1 K−1 at 873 K perpendicular to the pressing direction). Consequently, these electronic and thermal effects contribute to a high ZT of ∼1.9 at 873 K and an outstanding average ZT of 0.71 in polycrystalline SnSe. The combination of introducing PbSe quantum dots functional units and manipulating lattice strain provides a new perspective for designing high performance thermoelectric devices.