Hydrophilic Antireflection and Antidust Silica Coatings

Photonic Cooler Based on Multistacked Thin Films with Near-Infrared Filter Properties

We report on the development of a multistacked configuration of a photonic cooler for implementation in sunny and arid regions. The optimized multistacking structure considers TiOx as a top layer, NiOx as the buffer layer, and Ag as a hot mirror (i.e., a reflective layer of the NIR light spectrum). The entire stacked layers were deposited in situ without breaking the vacuum. The oxide layers were grown reactively under an oxygen medium at a deposition pressure of 2 × 10-4 Torr. The level of TiOx surface wettability was demonstrated to be controlled by the oxygen flow during the film growth process, which may additionally provide a self-cleaning property to the IR filters. By combining low refractive index layers (i.e., TiOx) with the high refractive index of the metal oxides (i.e., NiOx) along with the metal layers (i.e., Ag, Al), the photonic filtration (i.e., cutoff) of the infrared spectrum was successfully achieved while keeping the light transmittance of the visible (vis) light above 50%. Different structures with different thicknesses have been systematically assessed, including TiOx/NiOx/Ag, TiOx/NiOx/Al, TiOx/MoOx/Ag, and TiOx/MoOx/Al. Furthermore, numerical simulations were carried out using SCAPS-1D and OptiLayer software to evaluate the application of these filters on silicon solar cells, considering the experimental electrical and optical parameters for each explicit layer of the device. Our results confirm that the development of such coatings with a scalable thin film growth process may have a real commercialization potential due to their multifunctionalities such as IR filtering, antireflection coating in the vis range, and antisoiling properties.

High-Efficiency Perovskite Solar Cells with Sputtered Metal Contacts

Sputter deposition produces dense, uniform, adhesive, and scalable metal contacts for perovskite solar cells (PSCs). However, sputter deposition damages the other layers of the PSC. We here report that the damage caused by sputtering metal contacts can be reversed by aerial oxidation. We support this claim by making PSCs sputtered with Au contacts that exhibit higher efficiencies (18.7%) and stabilities than those made with thermally evaporated Au contacts (18.4%). We performed a series of experiments that show that the post-sputtering oxidation step reconstructs the molecular order of the hole transport layer (HTL) and reverses Au atom diffusion into the HTL. This potential restoration was previously neglected in PSC fabrication recipes because metal contact deposition is generally performed after the HTL oxidation. This result is important for scaling PSCs because sputtering is a superior method for manufacturing optimal-quality coatings or large-area devices.

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

Areas with abundant sunlight, such as the Middle East and North Africa (MENA), are optimal for photovoltaic (PV) power generation. However, the average power loss of photovoltaic modules caused by dust accumulation is extreme and may reach 1%/day, necessitating frequent cleaning which adds to the cost of operations and maintenance. One of the solutions to the problem of PV soiling is to develop anti-soil coatings, where hydrophilic or hydrophobic coatings with spectral characteristics suitable for PV applications are added to the outer layer of PV glass. However, the effectiveness of such coatings depends extensively on climatic conditions and geographical locations. Since coatings add to the cost of solar panels, it is imperative that they are first tested for suitability at the intended location and/or in similar weather conditions prior to their large-scale deployment. This critical review focuses on various anti-dust technologies employed to mitigate the PV soiling issue. The in-depth comparison of the various developed techniques and materials aims at providing a relevant input in adapting the right technology based on particles' accumulation mechanism, weather conditions, and geographical location. Though the mechanical cleaning process is the most used solution to date, development of thin film anti-dust coating could be a better alternative-when it is relevant-due to its abrasion-free capability, large deployment, economic viability, and durability. This review aims at serving as a reference in this topic, thereby paving the way to adapting efficient anti-dust coatings, especially in the MENA region and/or desert environment at large, where it is the most relevant.

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

Most bio-inspired antireflective nanostructures are extremely vulnerable and suffer from complicated lithography-based fabrication procedures. To address the issues, we report a scalable and simple non-lithography-based approach to engineer robust antireflective structures, inspired by the longtail glasswing butterfly, in a single step. The resulting two-dimensional randomly arranged 80/130/180 nm silica colloids, partially embedded in a polymeric matrix, generate a gradual refractive index transition at the air/substrate interface to suppress light reflection. Importantly, the randomly arranged subwavelength silica colloids display even better antireflection performance for large incident angles than that of two-dimensional non-close-packed silica colloidal crystals. The biomimetic coating is of considerable technological importance in numerous practical applications.