Few-Layer Nanosheets of n-Type SnSe₂

Layered p-block metal chalcogenides are renowned for thermoelectric energy conversion due to their low thermal conductivity caused by bonding asymmetry and anharmonicity. Recently, single crystalline layered SnSe has created sensation in thermoelectrics due to its ultralow thermal conductivity and high thermoelectric figure of merit. Tin diselenide (SnSe₂ ), an additional layered compound belonging to the Sn-Se phase diagram, possesses a CdI₂ -type structure. However, synthesis of pure-phase bulk SnSe₂ by a conventional solid-state route is still remains challenging. A simple solution-based low-temperature synthesis is presented of ultrathin (3-5 nm) few layers (4-6 layers) nanosheets of Cl-doped SnSe₂ , which possess n-type carrier concentration of 2×10¹⁸  cm^-3 with carrier mobility of about 30 cm²  V^-1  s^-1 at room temperature. SnSe₂ has a band gap of about 1.6 eV and semiconducting electronic transport in the 300-630 K range. An ultralow thermal conductivity of about 0.67 Wm^-1  K^-1 was achieved at room temperature in a hot-pressed dense pellet of Cl-doped SnSe₂ nanosheets due to the anisotropic layered structure, which gives rise to effective phonon scattering.