NIR-Reflective Black Photonic Films Designed for Effective LiDAR Recognition

Conventional dark-tone paints absorb both visible light and near-infrared (NIR) wavelengths, posing a challenge for light detection and ranging (LiDAR) recognition in autonomous driving. To overcome this issue, various chemical and structural coating materials have been explored to selectively reflect NIR. In this study, we newly propose colloidal photonic crystals with a stopband in the NIR range, fabricated through the spontaneous formation of crystalline arrays of silica particles dispersed in a photocurable resin, as a potential solution. The stopband position is finely adjusted by controlling the volume fraction of particles, and the translucent films are rendered black by incorporating carbon black nanoparticles into the interstitial regions. By optimizing the concentration of carbon black, we achieve a balance of low visible light and high LiDAR intensity. These black photonic films demonstrate superior LiDAR intensity compared to commercial dark-tone paints and perform on par with the perylene black-deposited white coating, one of the most promising LiDAR-assistive materials currently available, under normal reflection conditions. Additionally, the photonic films are highly durable, thermally stable, nontoxic, and environmentally friendly, making them promising candidates for LiDAR-assistive coatings.