High thermoelectric performance in p-type polycrystalline Cd-doped SnSe achieved by a combination of cation vacancies and localized lattice engineering

Herein, a high figure of merit (ZT) of approximate to 1.7 at 823 K is reported in p-type polycrystalline Cd-doped SnSe by combining cation vacancies and localized-lattice engineering. It is observed that the introduction of Cd atoms in SnSe lattice induce Sn vacancies, which act as p-type dopants. A combination of facile solvothermal synthesis and fast spark plasma sintering technique boosts the Sn vacancy to a high level of approximate to 2.9%, which results in an optimum hole concentration of approximate to 2.6 x 10(19) cm(-3) and an improved power factor of approximate to 6.9 mu W cm(-1) K-2. Simultaneously, a low thermal conductivity of approximate to 0.33 W m(-1) K-1 is achieved by effective phonon scattering at localized crystal imperfections, as observed by detailed structural characterizations. Density functional theory calculations reveal that the role of Cd atoms in the SnSe lattice is to reduce the formation energy of Sn vacancies, which in turn lower the Fermi level down into the valence bands, generating holes. This work explores the fundamental Cd-doping mechanisms at the nanoscale in a SnSe matrix and demonstrates vacancy and localized-lattice engineering as an effective approach to boosting thermoelectric performance. The work provides an avenue in achieving high-performance thermoelectric properties of materials.