Flexible graphene composites with high thermal conductivity as efficient heat sinks in high-power LEDs

Abstract

Flexible graphene composites (FGCs) have been fabricated for heat dissipation purposes by using a mold-casting method. The flexible graphene composites have an elastic modulus of 18–68 MPa, which is suitable for flexible heat sinks in lighting applications. Scanning electron microscopy (SEM) images show that the graphene nanoplatelets in the FGCs coalesce in the through-plane direction, which enhances the thermal conductivity by increasing the inter-layer contact among the graphene nanoplatelets, and reduces the structural defects and grain boundaries. The heat dissipation properties of the FGCs were compared with devices for aluminum heat sinks (AHSs). For this, the operating temperature in the emitting area of a high-power UV-LED was measured as a function of the mass for each type of heat sink. Experiments on LEDs demonstrated that the FGCs with masses of 4.9 g and 5.5 g cooled down the hottest points on the LEDs at similar temperatures observed when the LED is operating on an AHS with 565 g of mass. The heat dissipation results demonstrated that the FGCs could be used as compact and lightweight heat sinks for high-power LEDs employed as lighting sources.