Enhancing optoelectronic performance of rubidium halide-based perovskites RbSrCl3 via pressure-induced approaches

The vast majority of light-emitting diode and liquid-crystal displays, solar panels, and windows in residential and industrial buildings use glass panels owing to their high mechanical stability, chemical resistance, and optical properties. Glass surfaces reflect about 4-5% of incident light if no antireflective coating is applied. In addition to energy losses in displays, surface reflections diminish picture quality. Engineering of antireflective coatings can be beneficial for all types of glass screens, specifically for large screens and touch-screen devices when scratch-resistance and self-cleaning properties of the glass surface are also desired. A scalable and robust approach to produce antireflective coatings for glass surfaces with desired optical and mechanical properties is introduced in this work. The developed coating mimics the structure of a moth-eye cornea. The coating is a subwavelength-microstructured thin layer on the glass surface made of a monolayer of hemispherical silica nanoparticles obtained by hydrothermal fusion of spherical particles to the glass substrate. The sequence of the particle deposition in the layer-by-layer process is adjusted to balance attractive-repulsive interactions among nanoparticles and between the nanoparticles and the glass surface to generate coatings with a high surface coverage of up to 70%, which exceeds the 54.7% limit of the random sequential addition model. This level of surface coverage allows for a combination of properties beneficial for the described applications: (i) an average reflectance of 0.5 ± 0.2% for a visible and near-infrared optical spectrum, (ii) an improved mechanical stability and scratch resistance, and (iii) non-wetting behavior.

Devices employing double perovskite semiconductors have gained attention due to their favorable properties, including a compositionally and chemically stable crystal structure. This study utilizes density functional theory (DFT) and employs the full‐potential linearized augmented plane‐wave (FP‐LAPW) approach to examine the electrical, structural, thermoelectric, optical, and mechanical characteristics of Li 2 ScCuX 6 (X = Cl, Br, and I) double perovskite halides. The research focuses on evaluating optoelectronic and thermoelectric device characteristics. The stability of the anticipated compounds in cubic phase was validated using the octahedral factor and Goldsmith tolerance factor. Furthermore, to validate their thermodynamic and dynamic stabilities, we evaluated the formation energy and AIMD simulation technique. TB‐mBJ potential was utilized to calculate the electronic, optoelectronic, and thermoelectric characteristics. The analysis of the electronic band structure indicates an indirect band structure semiconducting characteristic, with band gap values of 1.71 eV for Li 2 ScCuCl 6 , 1.70 eV for Li 2 ScCuCl 6 , and 1.62 eV for Li 2 ScCuCl 6 . The optical characteristics present low reflectivity and elevated light absorption coefficients (10 4 /cm 2 ) within the visible spectrum. Their spectral response spans the ultraviolet to visible range, rendering them suitable for usage in solar cells and optoelectronic devices. The mechanical stability is validated by the Born–Huang stability criteria. The ductility of all analyzed perovskites is confirmed by Pugh's ratio, Cauchy pressure, and Poisson's ratio. BoltzTraP code was utilized to calculate the Seebeck coefficient, thermal conductivity, and electrical conductivity. The results demonstrate that Li 2 ScCuCl 6 , Li 2 ScCuBr 6 , and Li 2 ScCuI 6 exhibit a significant figure of merit ranging from 0.39 to 0.49. The results suggest that the investigated double perovskite Li 2 ScCuCl 6 is a promising candidate for photovoltaic, optoelectronic, and thermoelectric applications.

ABSTRACTThe impact of nanostructured broadband antireflection (AR) coatings on solar panel performance has been projected for a broad range of panel tilt angles at various locations. AR coated films have been integrated on test panels and the short-circuit current has been measured for the entire range of panel tilts. The integration of the AR coatings resulted in an increase in short-circuit current of the panels by eliminating front sheet reflection loss for a broad spectrum of light and wide angle of light incidence. The short-circuit current enhancement is 5% for normal light incidence and approximately 20% for off-angle light incidence. The National Renewable Energy Laboratory (NREL) System Advisor Model (SAM) predicts that this AR coating can yield at least 6.5% improvement in solar panel annual power output. The greatest enhancement, approximately 14%, is predicted for vertical panels. The AR coating’s contributions to vertical mount panels and building-integrated solar panels are significant. This nanostructured broadband AR coating thus has the potential to lower the cost per watt of photovoltaic solar energy.

Reduction of optical losses in colored solar cells with multilayer antireflection coatings

North America

Gallium arsenide finds use in a great number of electronics applications, and one of these is antireflection components in optoelectronic devices. Professor Douglas Hall of the University Of Notre Dame in the US tells us a bit more about his group's latest work in this field. Yuan Tian, Jinyang Li, and Doug Hall outside the Notre Dame Nanofabrication Facility, where the processing and some of the characterisation work was performed Gallium arsenide (GaAs) is widely used for optoelectronic devices such as photodetectors, solar cells, and red through amber LEDs. Uncoated GaAs has a reflectance of ∼33-47% across the visible spectrum. All of these devices can benefit from an antireflection layer on the surface to improve light collection or extraction efficiency. Many researchers (dating back to Henry Minden at General Electric in 1962) have tried a wide variety of methods to form a useful, insulating dielectric layer on the III-V compound semiconductor GaAs, akin to silicon dioxide grown on silicon. However, similar thermal oxidation processes do not readily work for GaAs because the material decomposes (i.e., Ga and As atoms “dissociate”) at the temperatures over 800°C typically used with silicon. We have recently discovered a means to directly oxidise GaAs at the relatively low temperature of 420°C. In this Letter, we show that the GaAs oxide films formed have a suitable refractive index and sufficiently smooth interfaces to form a useful antireflection (AR) layer on GaAs. The thermal oxidation methods previously reported for GaAs have typically used temperatures in the 510-700°C range and often resulted in low quality films with poor adhesion and rough surfaces and interfaces due to extensive pitting caused by dissociation. Most prior work doesn't report surface or interface roughness for these reasons. To form a high-performance AR layer based on thin-film interference effects, very smooth top and bottom oxide interfaces are absolutely essential so that two highly specular reflections are able to interfere destructively (when a relative phase shift of 180° is obtained for a given thickness and refractive index). In addition to our reported atomic force microscopy measurements of roughness, the close match between modelled and measured reflectance for the GaAs oxide AR layers realised in this work demonstrates the excellent interface quality of the oxides obtained through our process. When conventional wet-thermal oxidation of aluminum gallium arsenide (AlGaAs) was discovered by John Dallesasse et al. at the University of Illinois in 1990, it was found to be widely applicable only to alloys containing higher Al/Ga ratios, given the much greater chemical reactivity of Al. Around 2001, we found that oxidation rates of lower Al content alloys could be significantly enhanced (an order of magnitude or more) by mixing dilute amounts of oxygen into the water vapor process gas. In subsequent studies, we have learned that even Al-free alloys like GaAs and InGaAs can be oxidised, but the gas mixture must be carefully optimised and precisely controlled within a quite narrow “sweet spot”, a range of ∼0.1-0.2% oxygen flow rates relative to our nitrogen carrier gas. If too high or too low, or if small amounts of air leak into the system, surface quality and uniformity degrade, or no oxide grows at all. Even in 1962, Minden mixed water vapor with oxygen in the first reported study on GaAs oxidation, but concluded that it had no effect for temperatures under 800°C! This indicates that finding the proper O2/H2O ratio is critically important, and not just any mixture of these gases will do. We have elucidated the “why and how” details of the chemistry involved in some of our group's earlier papers on this subject. Optical microscope image of three oxidised GaAs samples on top of an unoxidised GaAs wafer We have recently been working to further enhance several aspects of the process control in our III-V compound semiconductor oxidation furnace, especially to more precisely regulate and monitor the optimal mixed gas ratios. Our wider research interests include applications of these native oxides to improve optical waveguides for semiconductor lasers and photonic integration, and we are currently actively exploring the extension of our process to telecommunications-wavelength InP-based materials and devices. As much as oxides of high-Al content alloys have found very widespread use for current apertures in commercial vertical cavity surface emitting lasers over the past 10-20 years, we would like to see the enhanced performance of other optoelectronic and photonic devices through the incorporation of oxidised low-Al content, Al-free, and InP-based alloys enabled by the mixed-gas oxidation process demonstrated in this work.

Study of optoelectronic, transport, and mechanical aspects of lead-free double perovskites Rb2AgTlX6 (X = Cl, Br) for green energy applications

Antireflective coatings with superhydrophobicity have many outdoor applications, such as solar photovoltaic panels and windshields. In this study, we fabricated an omnidirectional antireflective and superhydrophobic coating with good mechanical robustness and environmental durability via the spin coating technique. The coating consisted of a layer of phytic acid (PA)/polyacrylamide (PAM)/calcium ions (Ca2+) (referred to as Binder), an antireflective layer composed of chitin nanofibers (ChNFs), and a hydrophobic layer composed of methylsilanized silica (referred to as Mosil). The transmittance of a glass slide with the Binder/ChNFs/Mosil coating had a 5.2% gain at a wavelength of 550 nm, and the antireflective coating showed a water contact angle as high as 160° and a water sliding angle of 8°. The mechanical robustness and environmental durability of the coating, including resistance to peeling, dynamic impact, chemical erosion, ultraviolet (UV) irradiation, and high temperature, were evaluated. The coating retained excellent antireflective capacity and self-cleaning performance in the harsh conditions. The increase in voltage per unit area of a solar panel with a Binder/ChNFs/Mosil coating reached 0.4 mV/cm2 compared to the solar panel exposed to sunlight with an intensity of 54.3 × 103 lx. This work not only demonstrates that ChNFs can be used as raw materials to fabricate antireflective superhydrophobic coatings for outdoor applications but also provides a feasible and efficient approach to do so.

A first-principles study on the potential of MAB2 (M=Nb, ta; A=Co, Ni) ternary borides as friction-resistance cermet

Encapsulation of solar modules needs high-transparent solar glass. Antireflection (AR) coatings are usually deposited on solar glass to further improve transmission through suppression of Fresnel reflection at the interface of air and glass. Because the solar modules face the severe external environments during outdoor application, the AR coatings must be of not only high transparency, but also stability and scratch resistance. We dedicate to develop various AR coatings by studying the optical, mechanical properties, and durability. The work we have done is reviewed and the perspective on technology and application of novel AR coatings is presented.

Chapter 12 - Nanostructured superhydrophobic coatings for solar panel applications

The integration of solar modules into buildings offers a highly attractive area for enlarging the market of commercial solar cells. Therefore, cost-effective industrial approaches to fabricate solar cells and relevant modules with different colors are required. In this work a simple method for applying individual color to Si based solar cells was adapted to the industrially fabricated commercial cells with standard SiNx:H antireflection coating (ARC) and also explicitly described by a fundamental model. This method of coloring is based on the optical interference effect in the layered structure. The structure includes a thin indium tin oxide (ITO) layer deposited on the top of the ARC. An intentional change of the ITO thickness from 0 to 240 nm resulted in a change of the color through the visible spectrum. The color was added to multi- as well as mono-Si based industrially fabricated textured solar cells with conventional blue color ARC. Reasonable agreement between the theoretical and experimental results has been obtained from the model calculations. For the proof of concept, a mini-solar-module with six green cells was fabricated that were coated by an ITO (185 nm)/SiNx:H double layer ARC stack. It is shown that the efficiency of such module is only about 1.5% lower than that of the mini-module manufactured using reference industrial cells with SiNx:H ARC only. It is concluded that the proposed approach can be considered as a cost-effective method to fabricate coloured Si based cells and relevant modules using only one simple technological step.

Tuning the essential physical properties of KTaO3 through sulfur, selenium doping, and oxygen vacancy: A first principle investigation

Front side anti-reflective coatings (ARC) provide a significant contribution to performance and energy yield in PV modules, solar thermal housings and green house applications. However, ARC degradation and abrasion may lead to long term losses in optical performance. In order to quantify these losses and bench mark various ARC in abrasion testing, a nondestructive optical assessment of the ARC performance in large samples is required.Here, we present a methodology for the quantitative measurement of front side ARC performance and its impact on optical transmittance from a simple reflection spectroscopy measurement using a commercial spectrometer and a broad band absorber for reflection suppression at the glass back side. Results on reflection spectroscopy are presented on standard ARC coated solar glasses with and without internal reflection suppression, which represent the application scenarios in PV modules and green houses, respectively. The optical transmittance of the front side ARC is calculated via a simplified approach based on the law of energy conservation. A validation is performed by comparing spectra determined with the adapted experimental characterization method with optical calculations. Finally, the simplified method for a quantitative optical front side ARC assessment of full size glass panes is applied in successive and gradual ARC abrasion experiments.

www.advopticalmat.de Inevitable Fresnel refl ection from the interface between two optical media with different refractive indices ( η ) can decrease light absorption in photovoltaic devices and can cause undesirable glare in fldisplays. Thus, an effective antirefl ection coating (ARC) for a higher optical transmittance can contribute to the accomplishment of improved contrast and brightness in display devices and higher levels of energy conversion effi ciency in solar panels. Traditional ARCs improve optical transmittance by introducing destructive interference between refl ected light beams from the air-fi lm and fi lm-substrate interfaces. An ideal ARC should satisfy the requirements of a quarter-wavelength fi lm thickness and a fi lm η of ( η s ) 0.5 , where η s denotes the η of the substrate. [ 1 ] However, an ARC with a homogeneous η can achieve high transmittance only in narrow wavelength and incidence angle ranges, which are fi xed by its thickness and refractive index. In contrast, an ARC with a gradually changing η , also known as a graded index, can avoid the formation of an interface with a sharp contrast in η . As a result, the Fresnel refl ection can be effectively minimized in a wide wavelength range and high optical transparency can be achieved. In an ideal gradedindex anti-refl ection coating (GIARC), the η should gradually vary from that of the substrate material, onto which the GIARC is coated, to the η of air ( ∼ 1), necessitating the use of a material with a widely tunable η . Theoretical studies showed that a quintic profi le of η varying from that of the substrate (typically 1.5‐2) to 1 is best for achieving the lowest refl ectance (<0.1% in the visible range). [ 2 ] While dense materials generally have an η larger than ∼ 1.35, the extensive variability of indices has been demonstrated by nanoporous materials for the applications for GIARC. [ 2‐6 ] Various methods, such as lithography, obliqueangle deposition, catalytic etching, chemical vapor deposition, and a sol-gel process, have been reported. [ 2‐5 ] However, these methods may lack cost-effectiveness and high-throughput capabilities due to the requirements of vacuum processing, multiple etching steps, or because of the limited controllability of η . Recently, highly porous block copolymer (BCP) thin fi lms were applied to the fabrication of ARC due to the excellent low-cost solution processability and facile tunability of η when controlling the fraction of the pores generated by the selective removal of one block. [ 7‐11 ] Kim and co-workers reported a wide tuning range of η between 1.17 and 1.42 in nanoporous polystyrene (PS) thin fi lms obtained by removing poly(methyl methacrylate) (PMMA) in PS-PMMA BCPs. The stacking of three PS layers with gradually changing porosity achieved a minimum refl ectance of less than 0.1%. Han and coworkers demonstrated that a mixture of PS-PMMA BCPs and PMMA homopolymers led to a graded distribution of PMMA along the vertical direction of the thin fi lms and that a gradient η can be obtained for the remaining PS nanostructures after the removal of PMMA, which can reduce the number of processing steps including spin-coating and acid etching. However, these approaches may be associated with challenges related to the low chemical and mechanical stability of the porous organic thin fi lms and the