Theoretical study of phonon and electron transport in low band gap Janus MXene monolayer MoWCO2 for thermoelectric application

A theoretical study is performed on narrow bandgap Janus monolayer MoWCO2 using the density functional theory and the Boltzmann transport equation. The scattering rate is calculated for electron–phonon, phonon–phonon, phonon-boundary, and electron-boundary scattering. It has a power factor (6.5 × 103 μW/mK2) for p-type and (1.5 × 103 μW/mK2) for n-type at T = 700 K. A strong effect of surface scattering is observed in phonon transport, and lattice thermal conductivity is reduced to 65 W/m K from 308 W/m K at T = 300K for 1 μm width (L) of ribbon. In contrast, there is no change observed in electrical conductivity. This reduction in thermal conductivity improves the thermoelectric figure of merit to 0.33 (p-type) and 0.08 (n-type) at T = 700 K for L = 10 nm from 0.04 (p-type) and 0.01 (n-type). The obtained Young's modulus and Poisson's ratio are 244 N/m and 0.55, respectively, indicating that the material can be deformed under small strain. The obtained in-plane piezoelectric coefficients are e11 = 268 pC/m and d11 = 1.6 pm/V. This indicates the material will be suitable for wearable thermoelectric devices and sensor applications.