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.