Upcycling Silicon Sludge into LiDAR-Detectable Organic–Inorganic Hybrid Black Coatings

Conventional carbon-black coatings strongly absorb near-infrared (NIR) light, limiting their detectability by Light Detection and Ranging (LiDAR) sensors. Herein, semiconductor silicon sludge was upcycled into a black pigment for LiDAR-detectable organic–inorganic hybrid coatings. The silicon sludge was coated with TiO2 through a sol-gel process and subsequently reduced using NaBH4 to produce sludge-derived black TiO2 (SS/bTiO2). SS/bTiO2 was combined with NIR-transmissive organic pigments, including perylene diimide, diketopyrrolopyrrole, copper phthalocyanine, and perylene, to achieve visible blackness while maintaining NIR reflectance. A bilayer coating was further fabricated by depositing the hybrid black layer onto a white TiO2 bottom layer. In this structure, visible light was absorbed by the black pigment layer, whereas transmitted NIR light was reflected by SS/bTiO2 and the underlying TiO2 layer. The resulting coating exhibited enhanced NIR reflectance and was successfully recognized using commercial LiDAR sensors and a smartphone LiDAR system. This work demonstrates a sustainable strategy for converting semiconductor manufacturing waste into functional LiDAR-detectable black coatings for autonomous driving applications.
- This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2025-16070620).