Thermal conductivity and interfacial thermal conductivity of complex graphene nanoribbons without and with polyethylene molecules

We investigate the thermal conductivity (TC) and interfacial TC (ITC) of complex graphene nanoribbons (GNRs) with homojunctions formed by two monolayer GNR regions (MRs) and one central multi-layer GNR region (CR), as well as the influences of the CR layer number and length, the MR length, the GNR width, and the temperature. We show that the ITC is always smaller than the TC, indicating the entire heat transport performance is fundamentally determined by the interfaces. The GNRs with the two-layer CR show the largest ITC, which is much greater than the GNRs with other CR layer numbers. With increasing the temperature and the CR length, the ITC will increase while the TC will decrease for the GNRs with arbitrary CR layer numbers. However, the TC and ITC show the oscillations around certain values with the increase of the GNR width, and the TC will increase with the increase of the length of the MR. In addition, the TC (ITC) in the left part of the complex GNR changes in the same pace as the TC (ITC) in the right counterpart, while the TC always changes in the pace opposite to the ITC in the left or right part of the complex GNR. Finally, we show that the ITC can be increased by placing polyethylene molecules at the interfaces. This research should be an important reference for understanding the heat transport mechanism and designing the thermal functional materials.