Effect of van der Waals models on the phonon behavior and thermal conductivity of 2D graphene stacked structure

Abstract

Graphene-related two-dimensional (2D) van der Waals (vdW) materials with strong carrier-carrier scattering and weak carrier-phonon coupling, offer the potential to exceed the limit of the solar to electric power conversion efficiency (PCE). Understanding and regulating the interactions between phonons, electrons, and photons in graphene-related 2D materials play an important role for further breakthroughs of applications. Here, we systematically study the phonon property and thermal conductivity (k) of graphene stacked structures in different vdW models including non-local correlation functions (vdW-DF-R and vdW-DF) and a semiempirical generalized gradient approximation (GGA) function (DFT-D2). We found that there are significant differences in their predictions of k and phonon behavior. The interlayer spacings of bilayer graphene (BLG) and graphite are 3.363 and 3.34 Å by vdW-DF-R and vdW-DF, respectively, which are closest to experimental value (3.35 Å). The predicted room-temperature k of BLG and graphite are ∼152.8 and 1162 W/m-K by vdW-DF-R agreeing well with previous experiments. Comprehensive understanding of phonon properties show that compared with DFT-D2, the non-local vdW model confirms stronger anharmonic scattering of ZA modes in BLG than that in graphite. We expect that this work could facilitate the device designs with high thermal conductivity or high photoelectrical conversion efficiency based on vdW-stacked structures.