Infrared Absorption Properties of Carbon Nanotube/Nanodiamond Based Thin Film Coatings

We report on the characterization of thin-film near and short wavelength infrared absorbers comprised of carbon nanotubes dispersed in a polymer. Charged nanodiamond particles are used to effectively and uniformly disperse the carbon nanotubes in the polymer matrix, leading to a very homogenous film. Using this new technique, we demonstrate an infrared absorption of up to 95% in films with thicknesses <2000 nm. This remarkably high absorption is the result of low reflection off the surface and high absorption across the film thickness. The complex refractive index of the films is extracted using an effective media approximation. Calculations show the film has a wide angle for high absorption and is polarization independent. These films are easy to fabricate, robust and damage-resistant, and are compatible with post-processing techniques. These films can be used as the coating layer to boost the efficiency of uncooled infrared sensors and solar-thermal energy harvesters.