Fully solution-processed photonic structures from inorganic/organic molecular hybrid materials and commodity polymers

Abstract

Managing the interference effects from thin (multi-)layers allows for the control of the optical transmittance/reflectance of widely used, technologically significant structures such as antireflection coatings (ARCs) and distributed Bragg reflectors (DBRs). These rely on the destructive/constructive interference between incident, reflected and transmitted radiation. While known for over a century and having been extremely well investigated, the emergence of printable, large-area electronics brings a new emphasis: the development of materials capable of transferring well-established ideas to a solution-based production. Here, we demonstrate the solution-fabrication of ARCs and DBRs utilizing alternating layers of commodity plastics and recently developed organic/inorganic hybrid materials comprised of poly(vinyl alcohol) (PVAl), cross-linked with titanium oxide hydrates. Dip-coated ARCs exhibit an 88% reduction in reflectance across the visible compared to uncoated glass, and fully solution-coated DBRs provide a reflection of >99% across a 100 nm-spectral band in the visible region. Detailed comparisons with transfer-matrix methods (TMM) highlight their excellent optical quality including extremely low optical losses. Beneficially, when exposed to elevated temperatures, the hybrid material can display a notable, reproducible and irreversible change in refractive index and film thickness while maintaining excellent optical performance allowing post-deposition tuning, e.g., for thermoresponsive applications, including security features and product-storage environment monitoring.