Hydrophilic Antireflection and Antidust Silica Coatings

Abstract

We report on the optical and morphological properties of silica thin layers deposited by reactive RF magnetron sputtering of a SiO 2 target under different oxygen to total flow ratios [r(O 2 ) = O 2 /Ar, ranging from 0 to 25%]. The refractive index (n), extinction coefficient, total transmission, and total reflectance were systematically investigated, while field-emission scanning electron microscopy, atomic force microscopy, and threedimensional (3D) average roughness data construction measurements were carried out to probe the surface morphology. Contact angle measurements were performed to assess the hydrophilicity of our coatings as a function of the oxygen content. We performed a thorough numerical analysis using 1D-solar cell capacitance simulator (SCAPS-1D) based on the measured experimental optical properties to simulate the photovoltaic (PV) device performance, where a clear improvement in the photoconversion efficiency from 25 to 26.5% was clearly observed with respect to r(O 2 ). Finally, a computational analysis using OptiLayer confirmed a minimum total reflectance of less than 0.4% by coupling a silica layer with n = 1.415 with another high-refractive-index (i.e., >2) oxide layer. These promising results pave the way for optimization of silica thin films as efficient antireflection and self-cleaning coatings to display better PV performance in a variety of locations including a desert environment.

Single-Step Fabrication of Longtail Glasswing Butterfly-Inspired Omnidirectional Antireflective Structures

“…In contrast, its intrinsic antireflection characteristics are impaired after scratching with a 5 H pencil, resulting from obvious traces of scratches on the surface (insert of Figure 6 ). The coating hardness is even competitive with commercial antireflection coatings [ 38 ]. Moreover, in comparison with the hardness of the randomly arranged 80/130/180 nm silica colloid-coated PET substrate, it is evident that the surface and the corresponding optical properties of a bare PET substrate are damaged after scratching with a 2H pencil ( Figure 7 ).…”

Anti-Soiling Coatings for Enhancement of PV Panel Performance in Desert Environment: A Critical Review and Market Overview

“…The dust accumulation on PV glass modules significantly reduces modules’ output power ( Figure 3 ). Hence, the PV industry has been active in developing anti-soiling and anti-reflection coatings [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. However, very few experimental works have reported such layers for a longer period of testing time considering natural sandstorms along with other cleaning procedures [ 43 ].…”

“…In this technique, a porous silica layer forms on the glass panel by evaporation of the solvent. This silica layer consists of many hydroxyl groups, which helps in adsorbing water molecules on the surface [ 39 ]. Figure 8 shows a simple coating process based on sponge phase resin and the surface of the PV panels after coating [ 57 ].…”

“…Compared to the super-hydrophobic surface, the performance of dust reduction was 2.5 times higher and was found to be due to reducing organic cementation. In general, a super-hydrophilic surface can be proved to be hydrophilic through texturing of the surface and such morphology strongly depends on background gas pressure [ 39 ].…”

“…With texturing, 𝜇 3 × Cos θ = φ (𝜇 1 − 𝜇 2 ) − (1 − φ) 𝜇 3 , where φ stands for the insignificant area covered by the texturing on the surface, θ is the angle of the droplet, 𝜇 3 is the tension between liquid and vapor, 𝜇 1 is the tension between surface and vapor, 𝜇 2 is the tension between surface and liquid. This mechanism is well established and known as the theory of Wenzel and Cassie-Baxter [ 39 ]. For a super-hydrophobic surface, a water droplet rolls down the dust particles using gravitational force.…”