Boosting Thermoelectric Performance of PbBi2Te4 via Reduced Carrier Scattering and Intensified Phonon Scattering

Abstract Materials with low intrinsic lattice thermal conductivity are crucial in the pursuit of high‐performance thermoelectric (TE) materials. Here, the TE properties of PbBi 2 Te 4‐x Se x (0 ≤ x ≤ 0.6) samples are systematically investigated for the first time. Doping with Se in PbBi 2 Te 4 can simultaneously reduce carrier concentration and increase carrier mobility. The Seebeck coefficient is significantly increased by doping with Se, based on the density functional theory calculation, it is shown to be due to the increased bandgap and electronic density of states. In addition, the lattice strain is enhanced due to the difference in the size of Se and Te atoms, and the multidimensional defects formed by Se doping, such as vacancies, dislocations, and grain boundaries, enhance the phonon scattering and reduce the lattice thermal conductivity by about 37%. Finally, by using Se doping to reduce carrier concentration and thermal conductivity, a large ZT max = 0.56 (at 574K) is achieved for PbBi 2 Te 3.5 Se 0.5 , which is around 64% larger than those of the PbBi 2 Te 4 pristine sample. This work not only demonstrates that PbBi 2 Te 4 is a potential medium temperature thermoelectric material, but also provides a reference for enhancing thermoelectric properties through defect and energy band engineering.