Reactively evaporated multilayer antireflection coatings for Ge optical window

Abstract

Two multilayer antireflection (AR) coating configurations are designed, prepared and characterized. These AR coatings are designed for a 1 mm thick Ge optical window in the 3.25–5.25 µm band. Ta2O5 and TiO2 are used as high index materials along with SiO2 as low index material. Configuration 1 comprises nine alternating layers of SiO2 and Ta2O5, whereas configuration 2 comprises seven alternating layers of SiO2 and TiO2. Post-deposition annealing is also carried out in the temperature range 150–450 °C for 10 h. The prepared multilayered structures are characterized optically and structurally using a spectrophotometer, an atomic force microscope, x-ray diffraction and a scanning electron microscope. Optical characterization shows that multilayered structures have high absorption for as-deposited samples. A considerable improvement in the transmission profiles for the two multilayered configurations is observed at 350 °C with peak and average transmission for both the configurations exceeding 90%. The as-prepared samples show predominantly amorphous-like structure with pronounced peaks for configuration 2 only. Delamination (for configuration 1) and cracking (for configuration 2) of the multilayered structures are witnessed at an annealing temperature of 450 °C.

Highly Stable and Efficient Mesoporous and Hollow Silica Antireflection Coatings for Perovskite Solar Cells

“…Fresnel reflection at the air–substrate interface of a solar cell inevitably occurs because of the contrast of refractive index between air and transparent substrates, which is one of the most important optical losses for photovoltaic conversion efficiency. , More precisely, the generally used low iron glasses or plastic substrates with refractive indices ( n ) around 1.5 show typically visible light transmittance of ∼92% at normal incidence, − resulting in 8–10% reflection loss of the normal incident light, and this value can go up to 30% if all incident angles are taken into considerations . One of the most feasible methods to virtually eliminate Fresnel loss is to deposit an antireflection coating (ARC) on the transparent substrate. ,, For example, introducing multiple layers of higher and lower reflective indices alternatively with destructive interference, depositing a stack of homogeneous ultrathin transparent layers with graded index profiles to remove the step difference in refractive indices, or fabricating wavelength scale structured ARC to guide the incident light propagation toward the device. ,− …”

TiO2/SiO2 multilayer as an antireflective and protective coating deposited by microwave assisted magnetron sputtering

“…To become potential candidates for multilayered structures, thin films should exhibit certain desired properties such as high transparency, homogeneity, good adhesion, high hard− ness and ability to survive in different environmental condi− tions. The most often used for optical coating manufactur− ing are TiO 2 , SiO 2 , Nb 2 O 5 , Al 2 O 3 , Ta 2 O 5 , MgF 2 [7]. They are well transparent in a broad wavelength range and have low (MgF 2 , SiO 2 ), moderate (Al 2 O 3 , Ta 2 O 5 ) or high (TiO 2, Nb 2 O 5 ) refraction index.…”

Improved visible transparency of SIO2/ZNO:AL /CEO2-TIO2/SIO2 multilayer films with high UV absorption and infrared reflection rate

“…The most often used for optical coating manufacturing are TiO 2 , SiO 2 , Al 2 O 3 , Ta 2 O 5 , and MgF 2 [3] . It is reported that CeO 2 -TiO 2 coatings deposited on glass showed UV absorption and exhibited high reflectance and interference coloring [4][5][6] .…”