One‐Structure‐Based Barrier Film for Simultaneous Exclusion of Water and Ultraviolet Light

Abstract

CommuniCation(1 of 5) 1600888 UV barrier films on the flexible substrate.Furthermore, multilayer barrier films exhibit high Fresnel reflection loss at visible wavelengths (≈400 ≤ λ ≤ ≈700 nm) as a result of differences in the refractive indices of barrier layers. [27] By using an optical design to create a film that is impermeable to both water and UV, these problems will be overcome.In this letter, we propose a new type of multifunctional barrier film that prevents penetration by both water and UV light (Figure 1). To enable a low-cost and simple process, we developed a fabrication approach that uses UV-distributed Bragg reflector (UV-DBR) structures to combines thin-film passivation and a UV reflector. Layers of passivation materials (Si x N y , SiO 2 ) were alternated ("SN/SO pairs") in the UV-DBR structure, so water transmission was reduced. Simulation was conducted to optimize the thickness of SiO 2 and Si x N y to block UV light (λ < 400 nm) while maintaining visible transparency. According to finite difference time domain (FDTD) simulations, UV light can be remarkably reflected by the UV-DBR because of the welldesigned Bragg reflector structure. The UV-DBR structure with 10 SN/SO pairs reduced UV transmittance UT (wavelengths 200 ≤ λ ≤ 400 nm) to ≈1.6% while maintaining visible transmittance VT ≈ 78.9%.To design the UV-DBR structure, optical simulation was performed using Macleod (Thin Film Center, Inc.), which is based on the characteristics matrix method for optical analysis involving a multilayer structure. The optical constants of Si x N y and SiO 2 were measured using spectroscopic ellipsometry. Si x N y has an energy bandgap >4 eV, so it can protect against high-energy UV radiation (λ < 300 nm). [28] Therefore, optical simulation was conducted to optimize the thicknesses of SiO 2 and Si x N y to block UV (300 < λ < 400 nm). To determine the optimum thickness, five kinds of UV-DBR structure were considered (Figure 2a). In the design of the UV-DBR samples, a DBR structure with 10 SN/SO pairs (10-pair UV-DBR) was used, and center wavelengths were 310 ≤ λ c ≤ 390 nm. At 350 ≤ λ c ≤ 390 nm, UT was minimized to ≈3.0%. However, at λ c = 310 and 330 nm, 5.3 ≤ UT ≤ 7.9%. The average visible transmittance VT avg gradually decreased from 83.7% to 75.4% as λ c increased (Figure 2b). λ c = 350 nm was chosen as the best compromise between blocking of UV and maintenance of VT (81.8%). To obtain these values, the thicknesses of Si x N y and SiO 2 layers were calculated as t = λ/4n, where n is the refractive index of Si x N y (n = 2.3) and SiO 2 (n = 1.6) layers. For Si x N y , t = 41 nm; for SiO 2 , t = 54 nm. To study the angular dependency of UV-DBR, its UT and VT (Figure 2c) were calculated for incident angles 0°-80° to the normal. Three structures Si x N y (41 nm, Figure S2, Supporting Information), SiO 2 (54 nm, Figure S2, Supporting Information), and 10-pair UV-DBR (Figure 2c) on glass were simulated. Both Si x N y and SiO 2 samples had high angular UT (Si x N y = 49.6%, SiO 2 = 84.7% at 0°),

Ordered Hybrid Micro/Nanostructures and Their Optical Applications

“…The thicknesses of SiO 2 and Si x N y were optimized to block the UV light (<400 nm) while maintaining the visible transparency. This coating thus prevented the polymer or organic materials from degradation to some extent . Commonly, the organic constituents are not adaptable to nonflat substrates.…”

Solution-Processed One-Dimensional Photonic Crystals Based on Hollow Silica Exhibiting High Refractive Index Contrast

“…Theoretical models and practical applications suggest that these photonic structures can be engineered to reflect specific target wavelengths, rendering them invaluable in various domains. For instance, they are instrumental in creating vibrant structural colors with applications in anticounterfeiting − and aesthetics, − offering protective solutions against harmful radiation like ultraviolet rays, , enhancing the efficiency of solar cells in photovoltaics, − and showing considerable potential in sensing, , thermal insulation, − and radiative cooling …”

“…A higher Δ n typically signifies a broader band gap and more intense reflectivity. In addition to the need for lower Δ n to improve resolution in sensor applications, in many other optical fields, a higher Δ n often implies superior optical performance. − Traditional methods like physical vapor deposition (PVD) have been employed to fabricate these structures using inorganic materials such as SiO 2 /Si x N y , SiO 2 /TiO 2 , and SiO 2 /CdSe . However, these methods often suffer from drawbacks, including high-energy requirements and unsuitability for polymer substrates due to the high-temperature conditions involved.…”

Optical Design of Porous ZnO/TiO2 Films for Highly Transparent Glasses with Broadband Ultraviolet Protection

“…Unfortunately, as increases in UV absorptive materials, the extinction coefficients in UV region also decrease, causing reduced UV absorption. To compensate this degradation, different UV absorbers with high extinction coefficients in each UV region (i.e., UVA and UVB) are used in the form of nanocomposites or multilayer structures [19,20]. However, despite several studies of nanostructures for transparent UV protection, optical analysis and design have hardly been conducted to optimize UV absorbers for high visible-light transparency, and only studies adopting the reflection effect such as 1D photonic crystal or Bragg mirror have been conducted [21][22][23].…”