Reversible Ionic Liquid Intercalation for Electrically Controlled Thermal Radiation from Graphene Devices

Using graphene as a tunable optical material enables a series of optical devices such as switchable radar absorbers, variable infrared emissivity surfaces, or visible electrochromic devices. These devices rely on controlling the charge density on graphene with electrostatic gating or intercalation. In this paper, we studied the effect of ionic liquid intercalation on the long-term performance of optoelectronic devices operating within a broad infrared wavelength range. Our spectroscopic and thermal characterization results reveal the key limiting factors for the intercalation process and the performance of the infrared devices, such as the electrolyte ion-size asymmetry and charge distribution scheme and the effects of oxygen. Our results provide insight for the limiting mechanism for graphene applications in infrared thermal management and tunable heat signature control.