Enhanced thermoelectric properties of bilayer graphdiyne through twist angle and pressure regulation

Abstract

In this work, the thermoelectric properties of two-dimensional twisted graphdiyne were studied by using first-principles calculations and the Boltzmann transport equation. Unlike two-dimensional monolayer graphdiyne (GDY), which has a unique semiconductor phase, bilayer GDY (Bilayer) exhibited metallic properties. Furthermore, the band gap can be effectively adjusted by applying external stress and introducing a twist angle. Thus, the Seebeck coefficient and the ratio of the electrical conductivity to the relaxation time can be improved, thereby improving the ratio of the power factor to the relaxation time (PF/τ) of the material. The PF/τ value of the n-type structure reached a maximum of 81.36 μW/(K² cm s) at 300 K when −9 GPa of stress was applied to Bilayer in the in-plane direction with a twist angle of 21.79° (21.79°_TBGDY), which was approximately 1.74 times that without stress or a twist angle. This work combines these adjustment methods to improve the power factor to the relaxation time of the materials and further enhance their thermoelectric properties.