Theoretical study of thermoelectric properties of few-layer MoS₂and WSe₂

Molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) are prototypical layered two-dimensional transition metal dichalcogenide materials, with each layer consisting of three atomic planes. We refer to each layer as a trilayer (TL). We study the thermoelectric properties of 1-4TL MoS2and WSe2using a ballistic transport approach based on the electronic band structures and phonon dispersions obtained from first-principles calculations. Our results show that the thickness dependence of the thermoelectric properties is different under n-type and p-type doping conditions. Defining ZT1st peakas the first peak in the thermoelectric figure of merit ZT as doping levels increase from zero at 300 K, we found that ZT1st peakdecreases as the number of layers increases for MoS2, with the exception of 2TL in n-type doping, which has a slightly higher value than 1TL. However, for WSe2, 2TL has the largest ZT1st peakin both n-type and p-type doping, with a ZT1st peakvalue larger than 1 for n-type WSe2. At high temperatures (T > 300 K), ZT1st peakdramatically increases when the temperature increases, especially for n-type doping. The ZT1st peakof n-type 1TL-MoS2and 2TL-WSe2can reach 1.6 and 2.1, respectively. This journal is