Robust Operation of Mesoporous Antireflective Coatings under Variable Ambient Conditions

Abstract

Generating mesoporous films with adequate film thickness and refractive index is a common method to achieve amplitude and phase matching in low-cost interference-based antireflective coatings (ARCs). For high-surface-energy materials, pores on the 2−50 nm (i.e., on the subwavelength scale) are subject to capillary condensation by surrounding gas phase water molecules, which hampers their functioning. In this work, we examine the effect of relative humidity on mesoporous ARCs and present a simple method for the preparation of ARCs with robust operation under variable conditions. The materials route is based on the generation of well-defined porous aluminosilicate networks by block copolymer co-assembly with poly(isobutylene)-block-poly(ethylene oxide) and postsynthesis grafting of trichloro(octyl)silane molecules to the pore walls. The functionalized films exhibited a maximum transmittance value of 99.8%, with an average transmittance of 99.1% in the visible wavelength range from 400 to 700 nm. Crucially, the antireflection performance was maintained at high humidity values, with an average transmittance decrease of only 0.2% and maximum values maintained at 99.7%. This compared to maximum and average losses of 3.6 and 2.7%, respectively, for nonfunctionalized reference samples. The ARCs were shown to retain their optical properties within 50 humidity cycles, indicating long-term stability against fluctuating environmental conditions.

Fractionation of block copolymers for pore size control and reduced dispersity in mesoporous inorganic thin films

“…It is therefore reasonable to assume that the observed polydispersity is related to the PIB phenol precursor material rather than the subsequent grafting of polyethylene oxide. 8,48 Four BCPs served as structure-directing agents during this work. The three monodisperse BCP fractions (A17, A18, A19) were prepared alongside the polydisperse, non-fractionated BCP for comparison.…”

“…Inorganic sol material and mesoporous inorganic aluminosilicate films were prepared as described elsewhere. 8,25 BCP samples were first dissolved in a toluene/1-butanol azeotrope solution before mixing with the inorganic sol in an organic/inorganic ratio of 2 : 8. All samples were spin-coated at 2000 rpm for 20 seconds and immediately annealed on a programmable hot plate using a ramp rate of 1°C per min to a final temperature of 130°C for 30 minutes.…”

“…Structural control over a bicontinuous porous inorganic network on the 10 nm length scale is crucial for the functioning of many mesoporous thin film architectures, as demonstrated for mesoporous sensors, [1][2][3] ( photo)catalysis, 4,5 photovoltaics, including perovskite 6 and dye-sensitized solar cells, 7 optical coatings, 8 protective barriers 9 and separation and purification membranes. 10,11 Besides the mean pore size, the resulting pore dispersity is another important material property, as evidenced in examples related to electrochemistry, 2 sensing, 12,13 and controlled release.…”

Tailoring block copolymer nanoporous thin films with acetic acid as a small guest molecule

“…Porous polymer films have been revealed as promising candidates for a wide range of applications, such as gas and energy storage, separation and purification membranes, sensor applications or optical coatings . While a great number of methods have been described for their preparation, the fabrication of nanoporous films with tailored and uniform pore sizes and shapes remains as a challenge …”

“…Porous polymer films have been revealed as promising candidates for a wide range of applications, such as gas and energy storage, 1 separation and purification membranes, 2 sensor applications 3 or optical coatings. 4 While a great number of methods have been described for their preparation, 5 the fabrication of nanoporous films with tailored and uniform pore sizes and shapes remains as a challenge. [6][7][8] Block copolymer (BCP) self-assembly is a well-known approach for the creation of ordered nanoscale structures with tuneable size and morphology through control over a small number of key parameters, such as the relative volume fraction of the blocks ( ), the degree of polymerization (N), the Flory-Huggins parameter ( ab ) and the deposition conditions.…”