Enhanced ionic wind generation by graphene for LED heat dissipation

Abstract

Summary High voltage is an obstacle when applying electrohydrodynamics technology. Nanomaterials are good candidates for its extraordinary electrical properties and heat‐conducting characteristics. An originally designed ionic wind cooling system was secured with graphene using the dip‐coating method to study the cooling effect for the high‐power light‐emitting diodes. The experiment results indicated that the graphene on the needles' surface acted as new emitting electrode with a smaller curvature radius. The corona discharge current density increased, and the ionic wind inception voltage decreased, because of the high aspect ratios and the field emission characteristic of graphene. The maximum ionic wind volume velocity was improved by 41.3% when the discharge gap was 10 mm, which was attributed to the local electric field enhancement and the electron field emission effect that the graphene had. The best cooling performance was obtained when the needles and the heat sink were both coated with graphene. The junction temperature decreased 21%, and the luminous flux increased 5.6% at the discharge gap of 15 mm, taking the electrostatic screening effect into consideration.

Advanced Fog Harvesting Method by Coupling Plasma and Micro/Nano Materials

“…Different from the bare needle, the W nanoparticle film covering the electrode surface will form numerous protrusions with a nanometer curvature radius, as shown in Figure d,e. Each protrusion is considered a discharge point, which undoubtedly improves the density of discharge points per unit area. ,, The extremely small curvature radius and high-density discharge points reduce the discharge threshold and make the discharge easier to occur . In other words, the W nanoparticle-covered needle can obtain more charged particles and a higher electric field at a lower applied voltage.…”

A review on recent advances and challenges of ionic wind produced by corona discharges with practical applications

“…Although this approach cannot control the orientation of the nanoparticles on the electrode surface, which causes the discharge intensity to be inferior to that of the PECVD approach, the effect of reducing the corona onset voltage to a certain extent can be achieved. Wang et al [107,205] deposited graphene on the surfaces of a previously optimized multiple needle-mesh ionic wind cooling system using the dip-coating method to study the cooling performance of high-power LEDs. The results show that the corona current density increases and the ionic wind starting voltage decreases because of the field emission of electrons from the graphene surface and the high aspect ratio of graphene, leading to a more uneven electric field near the needles.…”

“…The current effective approach is to decorate the surface of corona electrodes with nanomaterials. Using nanomaterials to decorate the corona electrodes of IWGs to reduce ozone will also produce other beneficial effects, such as an increase in the corona current [87,202,219], increase in ionic wind velocity [205], and enhancement of anti-corrosion ability. The fundamental principle of using nanomaterials to change the corona discharge characteristics and ionic wind velocity is adding a large number of micro-discharge sites on the surface of the corona electrodes to increase the discharge intensity and wind velocity, reduce the ozone emission, and improve the durability of electrodes.…”

P‐108: Stable Thermal Distribution of Flexible Transparent InGaN/GaN Multiple Quantum Wells Micro‐LED Arrays

“…Current methods of heat dissipation like heat dissipation pipes, aluminum cooling fins, and fan cooling need to handle higher density and concentrated heat sources. [5][6][7][8] If heat is not well dissipated, it causes an increase of the junction temperature. It is well known that high junction temperature in LEDs lead to reliability problems such as low quantum efficiency, wavelength shifts, short lifetime, and even catastrophic failure.…”