Thermoelectric materials by using two-dimensional materials with negative correlation between electrical and thermal conductivity

In general, in thermoelectric materials the electrical conductivity σ and thermal conductivity κ are related and thus cannot be controlled independently. Previously, to maximize the thermoelectric figure of merit in state-of-the-art materials, differences in relative scaling between σ and κ as dimensions are reduced to approach the nanoscale were utilized. Here we present an approach to thermoelectric materials using tin disulfide, SnS 2 , nanosheets that demonstrated a negative correlation between σ and κ . In other words, as the thickness of SnS 2 decreased, σ increased whereas κ decreased. This approach leads to a thermoelectric figure of merit increase to 0.13 at 300 K, a factor ∼1,000 times greater than previously reported bulk single-crystal SnS 2 . The Seebeck coefficient obtained for our two-dimensional SnS 2 nanosheets was 34.7 mV K −1 for 16-nm-thick samples at 300 K. The improvement of the thermoelectric figure of merit ZT has been hindered by the challenges associated with the independent control of the electrical and thermal conductivity. Here the authors show that SnS 2 nanosheets can lead to an increased ZT via negative correlation between electrical and thermal conductivity.