Effective passive phase-change light-emitting diode cooling system using graphene nanoplatelets coatings

An effective passive two-phase light-emitting diode (LED) cooling system using thermally cured graphene nanoplatelets (GNPs) coatings is introduced. The GNPs-coated surfaces demonstrate significant reduction in the static contact angle as compared to the uncoated aluminium surface. The ultrafast water permeation property of the micro/nano-capillaries-structured GNPs coatings engenders significant cooling performance enhancement of the LED. The water is absorbed by the GNPs coatings and permeating upwards against the gravitation force. The water molecules are propelled through the nanocapillaries formed by the carbon walls and the capillary force dominates over the gravitational force. This induces the filmwise evaporation on the GNPs-coated surfaces and significantly enhances the LED cooling. As compared to the uncoated case, a maximum heat transfer coefficient enhancement of 73% is achieved. The GNPs coatings also significantly lower the operating light emitting surface temperature up to 10 °C reduction, effectively removes potential hotspots which in turn optimise the LED functionality and durability. This study paves the way for the promising employment of thermally cured GNPs coatings in developing a passive phase-change heat transfer device for LED cooling.