Broadband Antireflection Coating Covering from Visible to Near Infrared Wavelengths by Using Multilayered Nanoporous Block Copolymer Films

Broadband antireflection (AR) covering from visible light to near infrared (NIR) wavelengths (400−2000 nm) was obtained by using three sequential spin-coatings of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers with different volume fractions of PMMA block (fPMMA) on a glass. PS-b-PMMA having the lowest PMMA volume fraction (fPMMA ∼ 0.3) among three PS-b-PMMAs was first spin-coated on a glass substrate. After spin-coating, the film was irradiated by ozone to prevent dissolution during the next spin-coating process. Then PS-b-PMMA with the next larger volume fraction of PMMA block (fPMMA ∼ 0.46) was spin-coated and irradiated again by ozone. Finally, PS-b-PMMA with the largest volume fraction of PMMA block (fPMMA ∼ 0.69) was spin-coated. After three sequential spin-coatings, the entire film was irradiated under UV followed by rinsing with acetic acid, which removed PMMA blocks. This process allowed us to have the triple layers with spongelike nanoporous structures where the refractive in...