Thermoelectric Properties of PbSe Nanocomposites from Solution-Processed Building Blocks

High thermoelectric performance and low material cost are essential to the commercialization of thermoelectric modules. Microstructural design, size effects, and rational band engineering are among the keys to high thermoelectric performance, especially for nanocomposites. Here, we demonstrate a facile and versatile bottom-up approach to produce nanocomposites by heat consolidating solution-processed PbSe nanoparticles with a proper amount of Ag. In this PbSe-Ag system, a certain amount of Ag diffuses into the PbSe matrix and partially substituted Pb while other forms Ag2Se at the interphases. This increased the electrical conductivity and inversed the n-type behavior of PbSe to p-type, which is observed from the positive Seebeck coefficient for PbSe-Ag nanocomposites over the temperature range. Nonetheless, the decrease of total lattice thermal conductivity at high temperature is ascribed to the effective phonon at grain boundaries, Ag2Se nanodomain, and point defect. Overall, we obtained an optimized figure of merit, ZT = 0.97 at 723 K for 5 wt % Ag, a significant improvement of 8.8 times than the pure PbSe. Thus, this partially substituting host atom and the presence of a secondary phase provide another potential strategy to enhance the thermoelectric performance of PbSe, promoting its commercialization.