A highly thermostable and transparent lateral heat spreader based on silver nanowire/polyimide composite

Abstract

Heat accumulation is a severe problem for high-power light-emitting diodes (LEDs). Here, we introduce a thermostable and transparent lateral heat spreader as an additional heat-escaping channel of an LED chip to improve the thermal management of LED devices. The lateral heat spreader was prepared based on a silver nanowire (AgNW)/polyimide composite comprising a thin polyacrylate layer soldering a conductive AgNW network to confine the nanowires to the surface of a polyimide film and to obtain low contact resistance between the nanowires. The AgNW/polyimide composite film has a figure-of-merit sheet resistance of 7 ohm sq⁻¹ with 76% transmittance at 550 nm. After heating at 200 °C for 168 h, the sheet resistance increases to 16 ohm sq⁻¹. The thermal conductivity and thermal diffusivity are 130.2 W m⁻¹ K⁻¹ and 60.5 mm² s⁻¹, respectively, which are comparable to those of a commercial copper foil. A demonstration shows the core temperature in a thermal diffusion apparatus can be lowered by 9 °C. The experimental data combined with computational simulation indicate the Joule heating could be drawn away efficiently along the lateral heat spreader.