High Transparency Research Articles

Thickness Optimization of Front and Recombination ITO in Monolithic Perovskite/Silicon Tandem Solar Cells

Optical losses of perovskite/silicon tandem solar cells can be effectively reduced by optimizing the thin‐film layer thicknesses. Herein, the thicknesses of DC sputtered indium tin oxide (ITO) films, which serve as the front electrode and the recombination layer connecting the subcells, are optimized to reach high transparency and good lateral charge transport simultaneously. Optical simulations of the full perovskite/silicon tandem solar cell stacks are performed to find the optimum recombination and front electrode ITO thicknesses for solar cells as well as modules. Implementation of the optimized 25 nm front electrode ITO thickness in semitransparent single‐junction perovskite solar cells increases the short‐circuit density by 1.5 mA cm−2 compared to the former reference thickness of 75 nm. Combined with an optimized 20 nm recombination ITO layer, high short‐circuit density of 20.3 mA cm−2 is reached in perovskite/silicon tandem solar cell devices, which is the highest reported value for planar front perovskite/silicon tandem solar cells to the best of knowledge. Further interface passivation enables 28.8% power conversion efficiency.

Tailoring Mechanical and Optical Properties of Sputtered SiNx/BN Coatings.

The swift evolution of contemporary electronics products, such as flexible screens and wearable electronic devices, highlights the significance of flexible protective coatings, which combine superior mechanical and optical properties. Even though the recently developed polymer protective coatings can satisfy requirements for flexibility and transparency, their intrinsic nature often results in a hardness below 1 GPa, rendering them susceptible to scratches. On the other hand, traditional inorganic coatings, known for their high hardness and transparency, fall short of meeting flexibility requirements. In the present study, a SiNx/BN periodical nanolayered coatings (PNCs) structure has been tailored to achieve high mechanical durability, transparency, and flexibility. In SiNx/BN PNCs, the optical and mechanical properties of the single-layer SiNx film are crucial to the overall performance of the PNCs. Therefore, pulse direct current (DC) magnetron sputtering was optimized first to enhance the ionization efficiency of Si and N, thereby promoting their reaction and diminishing the presence of elemental silicon in SiNx. The effects of the pulse frequency and duty cycle on SiNx were evaluated. Additionally, the influence of the thickness ratio and modulation periods on the overall performance of the SiNx/BN PNCs was investigated. As a result, a SiNx/BN coating with sapphire-grade hardness, almost no optical absorption in the visible-near-infrared (vis-NIR) range, high wear resistance, and exceptional flexibility was demonstrated.

Effects of Moisture Content on the Radiative Properties and Energy-Saving Performance of Silica Aerogel Windows.

The thermal insulation performance of windows is crucial for energy-efficient buildings. Windows are typically the weakest part of the building envelope, regarding thermal insulation. Due to its excellent thermal insulation and high transparency, silica aerogel shows great promise as a window material. However, moisture can impact the effectiveness of the aerogel, leading to poor visibility and reduced thermal insulation. This study simulated a silica aerogel with varying moisture levels using the combination of diffusion-limited cluster aggregation, discrete dipole approximation, and Monte Carlo methods. The effects of the moisture content, thickness, porosity, and particle size on thermal conductivity, solar transmittance, and haze were analyzed. Visual properties of the aerogels were also considered. The energy consumption of a 30 m2 room under different climates was simulated using TRNSYS to assess the energy-saving potential of silica aerogel glass. The findings indicate that a higher moisture content leads to decreased solar transmittance and increased thermal conductivity of aerogels. Silica aerogel glass is more energy efficient than single-layer float glass, with the dry aerogel performing better in cold climates but worse in hot climates. This study provides insights for designing aerogel glass that optimizes solar transmittance and thermal insulation to enhance building comfort and energy efficiency.

Transforming Element Sulfur to High Performance Closed-Loop Recyclable Polymer via Proton Transfer Enabled Anionic Hybrid Copolymerization.

The utilization of sulfur has been a global issue. Copolymerization of element sulfur (S8) with other monomers is a promising route to convert it to useful materials but is limited by the comonomers. Here, we report anionic hybrid copolymerization of S8 with acrylate and epoxide at room temperature, where S8 does not copolymerize with epoxide in the absence of acrylate. Yet, the proton transfer from the methyne in acrylate to the oxygen anion enables the ring-opening of the cyclic comonomer and hence the copolymerization. The cyclic comonomers can be expanded to lactone and cyclic carbonate. Specifically, the copolymer of S8 with bisphenl A diglycidyl ether and diacrylate displays mechanical properties comparable to those of most common plastics, namely, it has ultimate tensile strength as high as 60.8 MPa and Young's modulus up to 680 MPa. It also exhibits high UV resistance and good transparency. Particularly, it has excellent UV-induced self-healing, reprocessability and closed-loop recyclability due to the abundant dynamic S-S bonds and ester groups. This study provides an efficient strategy to turn element sulfur into closed-loop recyclable polymer with high mechanical and optical performances.

UV-A Flexible LEDs Based on Core-Shell GaN/AlGaN Quantum Well Microwires.

Nanostructured ultraviolet (UV) light sources represent a growing research field in view of their potential applications in wearable optoelectronics or medical treatment devices. In this work, we report the demonstration of the first flexible UV-A light emitting diode (LED) based on AlGaN/GaN core-shell microwires. The device is based on a composite microwire/poly(dimethylsiloxane) (PDMS) membrane with flexible transparent electrodes. The electrode transparency in the UV range is optimized: namely, we demonstrate that single-walled carbon nanotube electrodes provide a stable electrical contact to the membrane with high transparency (70% at 350 nm). The flexible UV-A membrane demonstrating electroluminescence around 345 nm is further applied to excite Zn-Ir-BipyPDMS luminophores: the UV-A LED is combined with the elastic luminophore-containing membrane to produce a visible amber emission from 520 to 650 nm. The obtained results pave the way for flexible inorganic light-emitting diodes to be employed in sensing, detection of fluorescent labels, or light therapy.

High transparency Ce3+-doped oxyfluoride glass scintillator for X-ray imaging and γ-ray detection

High transparency Ce3+-doped dense gadolinium aluminum borosilicate (GSx) glass scintillator was synthesized in reducing atmosphere by melt-quenching process. The transmittance of the glasses exceeds 80%, and the light attenuation length is between 5-20 cm within the range of 400–600 nm. GSx glass shows an photoluminescence (PL) in range of 350–550 nm, with the strongest emission peak around 420 nm. The PL decay time of GSx glasses is around 37 ns, with a maximum PL quantum yield of 44.05%. The integrated X-ray excited luminescence (XEL) intensity of GSS glass is 52.5% compared with BGO crystal. For X-ray imaging, GSL glass based imaging system shows a high spatial resolution of 9 lp/mm, which is comparable to CsI:Tl X-ray detectors. Under γ-ray, the highest light yield of GSS glass is 1235 ph/MeV with an energy resolution of 24.0% at 662 keV, close to that of BSO crystal. The scintillation decay time of GSx glasses is consisted of fast (∼100 ns) and slow (∼560 ns) components. In thermally stimulated luminescence (TSL), GSS glass exhibits a strong TSL peak at approximately 440 K, with low intensity shoulders at about 520 K, implying different types of defects and traps. Therefore, GSx glass has promising prospects for X-ray imaging and high-energy physics applications.

Flexible transparent ITO thin film with high conductivity and high-temperature resistance

ITO thin films exhibit superior optical characteristics. However, their electrical properties are somewhat less optimal, and they demonstrate limited tolerance under high-temperature conditions. These limitations significantly constrain their potential applications in the domain of optical and electronic devices. In this study, ITO thin films with a thickness of 20 nm were prepared on a flexible Mica substrate. The film has an atomic-level flat surface, high optical transparency (around 85 %), and low resistivity. The stability of the film's surface chemical structure in high-temperature applications was confirmed through XPS characterization. Furthermore, the ITO/Mica flexible thin film demonstrates exceptional durability and recyclability, retaining its optical and electronic properties under a high bending radius of 5 mm and 1000 bending cycles. It is particularly noteworthy that the film's maintenance of good structural and electrical stability (sheet resistance stabilized at 35∼37.5 Ω/sq) under bending cycles at high-temperature (up to 800 °C) conditions, which is crucial for high-temperature resistance in commercial and industrial applications. This study will provide an important experimental basis for the further development and application of ITO thin films in flexible transparent electronic devices with high temperatures and low energy consumption.

Energy-efficient and directional preparation of cellulose nanosheets by one-pot surface modification assisted swelling method

The energy-intensive and time-consuming process required for disassembling natural materials into nanoblocks are the major obstacles for the practical applications of biopolymer nanomaterials. Herein, a one-pot, energy-efficient and directional preparation method for gently exfoliating cellulose into nanosheets was achieved by surface modification assisted swelling process. The resulting cellulose nanosheets (CNSs) exhibited diameters ranging from 100 to 480 nm and thicknesses of approximately 5 nm, with a maximum yield of 97.9 %. This method could be widely applicable to common cellulose raw materials. Contrary to other nanocellulose reported previously, CNSs could be dried and stored in solid state, and re-dispersed in aqueous phase, thereby convenient for storage and transportation. Cellulose nanosheets films (CNSFs) obtained from CNSs showed high transparencies (>90 %) and excellent gas barrier properties, especially for the water vapor permeability of only 0.0072×10−10 cm3 cm cm−2 s−1 Pa−1, which were superior to other cellulose based films. In the simulation experiment of dry food packaging, CNSF10 possessed remarkable water vapor and oxygen blocking capabilities comparable to commercial cling films and met the practical requirements. The preparing process of CNSs reported here had the advantages including easy implementation, energy efficiency, and environmentally friendliness, and expanded possibilities for large-scale and widespread utilization of nanocellulose.

Preparation and Stability Study of an Injectable Hydrogel for Artificial Intraocular Lenses.

Currently available intraocular lenses (IOLs) on the market often differ significantly in elastic modulus compared to the natural human lens, which impairs their ability to respond effectively to the tension of the ciliary muscles for focal adjustment after implantation. In this study, we synthesized a polyacrylamide-sodium acrylate hydrogel (PAH) through the cross-linking polymerization of acrylamide and sodium acrylate. This hydrogel possesses excellent biocompatibility and exhibits several favorable properties. Notably, the hydrogel demonstrates high transparency (94%) and a refractive index (1.41 ± 0.07) that closely matches that of the human lens (1.42). Additionally, it shows strong compressive strength (14.00 kPa), good extensibility (1400%), and an appropriate swelling ratio (50 ± 2.5%). Crucially, the tensile modulus of the hydrogel is 2.07 kPa, which closely aligns with the elastic modulus of the human lens (1.70-2.10 kPa), enabling continuous focal adjustment under the tension exerted by the ciliary muscles.

Reverse Mode Polymer Stabilized Cholesteric Liquid Crystal Flexible Films with Excellent Bending Resistance.

The reverse-mode smart windows, which usually fabricated by polymer stabilized liquid crystal (PSLC), are more practical for scenarios where high transparency is a priority for most of the time. However, the polymer stabilized cholesteric liquid crystal (PSCLC) film exhibits poor spacing stability due to the mobility of CLC molecules during the bending deformation. In this work, a reverse-mode PSCLC flexible film with excellent bending resistance was fabricated by the construction of polymer spacer columns. The effect of the concentration of the polymerizable monomer C6M and chiral dopant R811 on the electro-optical properties and polymer microstructure of the film were studied. The sample B2 containing 3 wt% of C6M and 3 wt% R811 presented the best electro-optical performance. The electrical switch between transparent and opaque state of the flexible PSCLC film after bending not only indicated the excellent electro-optical switching performance, but also demonstrated the outstanding bending resistance of the sample with polymer spacer columns, which makes the PSCLC film containing polymer spacer columns have a great potential to be applied in the field of flexible devices.

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

Tolerance of Corundum‐Structured Tin‐Doped Indium Oxide Thin Films to Gamma‐ray Irradiation

Corundum‐structured Sn‐doped indium oxide (rh‐ITO) is investigated as a novel transparent conductive oxide. Herein, its gamma‐ray tolerance up to a total dose of 77 kGy is examined for potential applications in harsh environments, such as space. The investigations are conducted on rh‐ITO with Sn concentrations of 0 and 5 at%. X‐ray diffraction 2θ‐ω scan analysis reveals that no phase separation occurs due to gamma‐ray irradiation. The carrier concentration in undoped rh‐In2O3 increases after irradiation, indicating that the gamma rays displace the oxygen atoms and form oxygen defects that generate donors. The high visible light transparency of rh‐In2O3 and rh‐ITO is maintained after irradiation. This study demonstrates the high stability of rh‐ITO to gamma‐ray irradiation until 77 kGy dose. This work contributes to the application of rh‐ITO as an electrode in high‐radiation environments.

Design of a 10.8 to 34.6 GHz Ultra‐Wideband Transparent Metamaterial Absorber Using an Equivalent Circuit Model

AbstractIn this paper, an ultra‐wideband metamaterial absorber (UWMA) is proposed and demonstrated by using a transparent and flexible sandwich structure, which consists of a top patterned double‐square loop (DSL) of conductive film, the polymer interlayer, the bottom conductive film. The work presents the UWMA's equivalent circuit model for a macroscopic analysis of its physical mechanism. Further, optimizing UWMA's structural parameters using this equivalent circuit model can greatly enhance its efficiency. The absorption coefficient of the designed structure achieves over 90% within the wide frequency range from 10.82 to 34.59 GHz due to the overlapping of three absorption bands. The experimental results indicate that the absorption coefficient of the fabricated structure exceeds 60% in the frequency range of 10.45–35.28 GHz, and reaches 90% in the majority of frequency range of 10.71–28.51 GHz, while its averaged optical transparency in the visible spectrum exceeds 75%. The UWMA achieves high transparency due to a small ratio of the surface area occupied by the ITO pattern to the total area and realizes multiple‐resonance ultra‐wideband absorption with conformality while maintaining a thickness of only 2.2 mm, which has diverse applications in the field of electromagnetics, including aircraft stealth, transparent chambers, and flexible electronic screens.

Highly transparent inorganic superhydrophilic coatings with sustainable anti-fogging and mechanically robust underwater anti-oil-fouling capabilities

Inorganic coatings with high transparency and superhydrophilicity have attracted tremendous attention because of their potential applications in marine environment monitoring, and oily wastewater treatment. However, the transparency and superhydrophilicity are usually mutually exclusive. Herein, we present a new facile strategy for fabricating highly transparent and mechanically robust superhydrophilic inorganic coatings with outstanding anti-fogging ability and anti-oil-fouling performance for high-viscosity oils. In this strategy, amorphous calcium phosphate (ACP) coatings are mineralized on the surface of polydopamine and polyethylenimine (PDA/PEI) membranes under the synergistic effect of magnesium ions, citric acid, and poly(acrylic acid) at room temperature, forming an organic-inorganic composite structure with a uniform texture on various substrates. Owing to the strong hydration capacity of ACP, these coatings are highly efficient at preventing surface fogging and avoiding underwater crude oil fouling. Meanwhile, the ACP coating without grain boundaries or pores can reduce light scattering, thus maintaining the high transparency of the substrate. Moreover, the organic-inorganic composite structure endows the coatings with robust mechanical properties. This PDA/PEI-ACP mineralized coating can be deposited on various substrates, showing potential applications in underwater optical lenses, oily wastewater treatment, microfluidic devices, and other areas.

FLUID: a fluorescence-friendly lipid-compatible ultrafast clearing method.

Many clearing methods achieve high transparency by removing lipid components from tissues, which damages microstructure and limits their application in lipid research. As for methods which preserve lipid, it is difficult to balance transparency, fluorescence preservation and clearing speed. In this study, we propose a rapid water-based clearing method that is fluorescence-friendly and preserves lipid components. FLUID allows for preservation of endogenous fluorescence over 60 days. It shows negligible tissue distortion and is compatible with various types of fluorescent labeling and tissue staining methods. High quality imaging of human brain tissue and compatibility with pathological staining demonstrated the potential of our method for three-dimensional (3D) biopsy and clinical pathological diagnosis.

Bioinspired transparent ultratough birefringent photonic films with engineerable interference colors derived from in-situ synthesis of CaCO3

Chameleons can rapidly modify their coloration by manipulating the arrangement of iridophores encompassing guanine crystals in their dermis, which enables incident light to undergo birefringence. Various biomaterials have been designed to mimic the arrangement of guanine crystals, yet instances of synthesizing bottom-up structures with anisotropy for optical functionality remain rare. In this study, we report a novel two-step gas diffusion method for in-situ synthesis of CaCO3 (Vaterite) within a hydrogel to fabricate a bio-photonic film displaying birefringence interference colors. This strategy enables the successful fabrication of an inorganic–organic photonic film with superior mechanical properties and flexibility, resulting in high transparency, superior toughness, and adjustable optical anisotropy. Through a combination of experiment and simulation results, we elucidated the critical role played by shape factor (distribution) and structural factor (particle size) in producing transmitted interference colors. Finally, the birefringent photonic films prepared using the dot-plate method can function as optical patterns accurately representing the “on”/“off” state within a binary system. This system offers high spatial resolution, excellent repeatability, and precise controllability of optical properties, making it applicable in fields such as information encryption and decrytion. Our study has successfully synthesized photonic material with anisotropic structure though in-situ method while elucidating the underlying mechanism governing their ability to generate transmission interference colors, thus opening up new avenues for transparent flexible polarized optics, imperceptible wearable devices, and advanced information encryption.

Functionalized cellulose nanofiber films as potential substitutes for Japanese paper

Japanese papers (JPs) are among the most common materials used for the restoration of historical papers. However, they have low transparency and may structure the paper surface. To overcome the limitations of JPs, in the present work, films of cellulose nanofibers with and without lignin (LCNFs and CNFs, respectively) were explored. For this, chemically different LCNFs (carboxylated by TEMPO-mediated oxidation using variable oxidant amount and sulfated with deep eutectic solvent) and two reference CNFs were produced from Eucalyptus kraft pulps. Lignin hindered slightly the introduction of carboxyl groups into the cellulose structure, but did not affect the incorporation of sulfate groups. (L)CNFs gave films with better mechanical properties than those determined for three types of JP (tensile strength of 79–142 MPa (±11) vs 3.5–13.0 MPa (±0.4) and Young's modulus of 4900–5900 MPa (±300) vs 200–1800 MPa (±70)). Additionally, the (L)CNF films exhibited lower water vapor transmission rates (132–312 g.m−2.day−1) compared to the JPs (685–719 g.m−2.day−1), and a higher transparency (up to 89% and ≤82% for JPs). Besides thermal stability, all properties studied favored (L)CNF films over JPs, indicating their strong potential for restoration/conservation applications. This systematic comparison between the properties of (L)CNF films and JPs has never been conducted before.

A versatile ionic liquid enables epoxy resin with excellent fire safety and mechanical properties but ultra-low loading

The emergence of ionic liquids provides an effective way to construct new advanced multifunctional epoxy resin (EP) composites with excellent fire retardancy and mechanical properties. In this study, 1-butyl-3-methylimidazolium dibutyl phosphate (BDBP) was synthesized via a facile strategy and then incorporated into the EP matrix. The results showed that ultra-low loading of BDBP (1 wt%) enabled EP composite to achieve a V-0 rating (3.2 mm) in the UL-94 test. When increasing the loading to 4 wt%, the limiting oxygen index (LOI) of EP/BDBP4 composites was improved to 31.9 %. Meanwhile, the peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) significantly decreased by 48.1 %, 21.9 %, and 13.5 %, respectively, compared to neat EP. Moreover, the presence of BDBP increased the tensile strength of EP/BDBP2 by more than 7 %, while all EP/BDBP composites maintained high transparency. In summary, this work provides a feasible and low-cost idea for constructing multifunctional EP composites, paving the way for their applications in aerospace, wind turbines, and electronic and electrical fields.

Mn doping and core-shell engineering of silane-modified Mn-TiO2@SiO2 nanoparticles with drastically reduced photocatalytic activity for transparent UV-shielding hybrid materials

The photocatalytic ability and incompatibility with the organic matrix of TiO2 limit its application in UV-shielding hybrid materials. Tuning the electronic structure and engineering the morphology of TiO2 are effective in reducing photocatalytic activity but remain challenging in drastic reduction. Herein, a Mn-TiO2@SiO2 structure with an average size of 24.4 nm is constructed via a combination strategy of Mn doping and core–shell engineering to accelerate the recombination of carriers and build surface barriers. Impressively, compared with pure TiO2, the 2 %Mn-TiO2@SiO2 shows 336, 447, and 237 times lower photocatalytic reaction rate constants (k) for the degradation of three dyes (reactive red 120, methyl orange, and methyl blue), respectively, demonstrating the drastically reduced photocatalytic activity of Mn-TiO2@SiO2 structure. The characterizations and density functional theory calculations reveal that Mn doping introduces an occupied deep level and an unoccupied shallow level, which facilitates the co-trapping of electrons and holes, accelerating the recombination of carriers, and the SiO2 shell serves as a barrier to mitigate the interfacial charge transfer. Additionally, surface modification using silanes enables monodisperse core–shell structure and improves its compatibility with substrates, providing the UV-shielding Mn-TiO2@SiO2-C12 silane/fluorocarbon hybrid coatings with high transparency and anti-UV aging ability.

Investigating the optical and electrical performance of rod coated silver nanowire-based transparent conducting films

Silver nanowires (Ag NWs) are highly promising building blocks for developing transparent conducting films (TCFs) due to their high electrical conductivity and good optical transparency. The large-scale production of Ag NW-based high-quality TCFs using low-cost processing methods can replace the traditional oxide based TCFs. Therefore, developing a reliable technique for large-scale fabrication of Ag NW-based TCFs is vital. This work involves the synthesis of Ag NWs, the fabrication of large-area Ag NW-based TCFs using a simple rod coating process, its optimization, and the performance analysis of the fabricated TCFs, including their demonstration as transparent heaters. The polyol synthesis method produces Ag NWs of lengths ranging from 25-110µm and diameters from 80-180 nm. The effect of Ag NW length, the number of coating passes, and the volume of the NW dispersion used per coating pass on the electrical and optical properties of the TCFs are studied by quantifying sheet resistance(Rs)and transmittance (T) of the film. The performance of the fabricated film is evaluated by estimating the figure of merit (FoM) in both percolative and bulk regimes. The TCF made with NWs of length 25.7µm and diameter 85.1 nm had the largest value of bulk FoM (101.3), percolative FoM (43.9), and, conductivity exponent (0.6). This elucidated the superior performance of the fabricated TCFs over those fabricated by other techniques. The critical thickness of the film (tmin), at the crossover between the percolation and bulk, scales with the shortest dimension of the NW, namely its diameter. The percolative FoM showed an increase, with a decrease in both sheet resistance and diameter of the NWs, with lowern. The fabricated TCF is tested as a transparent heater and the demonstration proves that rod coated Ag NW-based TCFs can be used for transparent electrode applications.