High Transparency Research Articles

Highly transparent and semi-transparent perovskites and their applications

Perovskite has recently garnered significant attention as a promising semiconductor for optoelectronic applications and particularly for solar cells. In various applications, solar cells must be semi-transparent or even nearly fully transparent. Perovskite solar cells emerge as strong contenders to meet this requirement, owing to their remarkable versatility that allows for high transparency. Consequently, numerous studies on semi-transparent perovskite have been presented in recent years, demonstrating significant advancements in their properties. This review aims to explore color-neutral highly transparent and semi-transparent perovskite solar cells, encompassing their synthetic routes, challenges associated with their fabrication process, and potential solutions. The incorporation of potential additives or two-dimensional perovskites to enhance the properties of semi-transparent perovskite solar cells is also discussed. Finally, we will delve into some promising applications of semi-transparent perovskite solar cells and other applications that have been successfully studied.

Evaluasi Kinerja Algoritma Klasifikasi dalam Studi Kasus Prediksi Kelulusan di Universitas XYZ

This study aims to evaluate the performance of three classification algorithms—Decision Tree, K-Nearest Neighbors (KNN), and Naive Bayes—in a case study of predicting student graduation outcomes at XYZ University. Utilizing a dataset that includes a diverse range of academic attributes of students, this research conducts an in-depth analysis of each algorithm's capability to predict students' graduation status. The findings reveal that the Decision Tree provides the best performance with an accuracy rate of 97%, while KNN also shows very good results with similar accuracy, and Naive Bayes records an accuracy of 91%. The advantage of the Decision Tree lies in its ease of interpretation and high decision transparency, making it highly suitable for educational system implementations. Meanwhile, KNN excels in handling complex datasets due to its adaptability to data variability, and Naive Bayes offers rapid analysis speeds ideal for processing large data volumes. These insights provide valuable guidance for educational institutions in developing more effective graduation prediction systems and supporting strategic decisions in academic management. The study also opens avenues for further research in exploring these algorithms' applications in broader educational contexts, as well as fine-tuning modeling techniques to enhance prediction accuracy and efficiency.

UV-Curable Optical-Silicone-Modified Coatings Prepared from CO2-Based Non-Isocyanate Polyurethane Diol

Though polyurethanes (PUs) are widely used in people’s daily lives, traditional PUs are generally fabricated from toxic (poly)isocyanates. Furthermore, (poly)isocyanates are commonly industrially prepared from a seriously toxic and injurious chemical compound named phosgene, which is a dangerous gas that can cause lung irritation and eventually death. As is known to all, the consumption of carbon dioxide (CO2)-based raw materials in chemical reactions and productions will be conducive to reducing the greenhouse effect. In this paper, non-isocyanate polyurethane (NIPU) diol was fabricated through a polyaddition reaction from ethylenediamine and CO2-based ethylene carbonate, and then NIPU-based silicone-containing thiol hyperbranched polymers (NIPU-SiHPs) were synthesized from the NIPU diol. Finally, UV-curable optical-silicone-modified CO2-based coatings (UV-NIPUs) were fabricated from NIPU-SiHPs and pentaerythritol triacrylate by a UV-initiated thiol-ene click reaction without a UV initiator. The UV-NIPUs demonstrated high transparency over 90% (400–800 nm), good mechanical performance with tensile strength reaching 3.49 MPa, superior thermal stability with an initial decomposition temperature (Td5) in the range of 239.7–265.6 °C, moderate hydrophilicity with a water contact angle in the range of 42.6–62.1°, a high pencil hardness in the range of 5–9H, and good adhesive performance of grade 0. The results indicate that it is a promising green chemical strategy to fabricate CO2-based high-performance materials.

Sustainable passive radiation cooling transparent film for mobile phone protective screens

Passive daytime radiative cooling (PDRC) is a promising approach to address energy, environmental, and safety issues caused by global warming, with high emissivity in a transparent atmospheric window and high reflectivity in the solar spectrum. However, most demonstrations of PDRC rely mainly on complex and expensive spectral selective nanophotonic structures, requiring specialized photonic structures that are both expensive and difficult to obtain. The superiorities of low-cost, abundant resources, renewability, and high value-added biomass resources prompt Gleditsia sinensis polysaccharides (GSP) to be used in thermal emission materials to explore further the characteristics of regulating object temperature within a specific range without any external energy consumption. The three-layer thermal emission film (PDMS3PG3/t4) obtained by the scalable scraping method has high transparency, hydrophobicity (114.2°), and super flexibility. The spectral variations of non-selective PDMS3PG3/t4 (1.0wt% GSP, 800 μm thickness) in the 3-5μm and 8-13μm waveband ranges were discussed in detail, and high emissivities of 69.1% and 92.2% were obtained, respectively. PDMS3PG3/t4 was appointed a mobile phone screen film and experimented with a 4.9°C average temperature difference below ambient temperature, materializing prime PDRC and desiring to broaden the passive cooling technology and reduce the global energy burden.

Synthesis of copper nanowires and facile fabrication of nanostructured conductors with high transparency in 400–2500 nm spectral range

Synthesis of copper nanowires and facile fabrication of nanostructured conductors with high transparency in 400–2500 nm spectral range

New high UV transparency PV encapsulants: properties and degradation after accelerated UV aging tests

New high UV transparency PV encapsulants: properties and degradation after accelerated UV aging tests

Recent Advances and Challenges in Metal Halide Perovskite Quantum Dot-Embedded Hydrogels for Biomedical Application

Metal halide perovskite quantum dots (MHP QDs), as a kind of fluorescent material, have attracted much attention due to their excellent photoluminescence (PL) quantum yield (QY), narrow full width at half maximum (FWHM), broad absorption, and tunable emission wavelength. However, the instability and biological incompatibility of MHP QDs greatly hinder their application in the field of biomedicine. Hydrogels are three-dimensional polymer networks that are widely used in biomedicine because of their high transparency and excellent biocompatibility. This review not only introduces the latest research progress in improving the mechanical and optical properties of hydrogels/MHP QDs but also combines it with the existing methods for enhancing the stability of MHP QDs in hydrogels, aiming to provide new ideas for researchers in material selection and methods for constructing MHP QD-embedded hydrogels. Finally, their application prospects and future challenges are introduced.

Selective Undercut of Undoped Optical Membranes for Spin-Active Color Centers in 4H- Silicon Carbide.

Silicon carbide (SiC) is a semiconductor used in quantum information processing, microelectromechanical systems, photonics, power electronics, and harsh environment sensors. However, its high-temperature stability, high breakdown voltage, wide bandgap, and high mechanical strength are accompanied by a chemical inertness, which makes complex micromachining difficult. Photoelectrochemical (PEC) etching is a simple, rapid means of wet processing SiC, including the use of dopant-selective etch stops that take advantage of the mature SiC homoepitaxy. However, dopant-selective PEC etching typically relies on highly doped material, which poses challenges for device applications such as quantum defects and photonics that benefit from low doping to produce robust emitter properties and high optical transparency. In this work, we develop a selective PEC process that relies not on high doping but on the electrical depletion of a fabricated diode structure, allowing the selective etching of an n-doped substrate wafer versus an undoped epitaxial (carrier density of 1(10)14 cm-3) device layer. We characterize the photoresponse and PEC behavior of the diode under bias and use those insights to suspend large (100 × 100 μm) undoped membranes of SiC. We further characterize the compatibility of membranes with quantum emitters, performing comparative spin spectroscopy between undoped and highly doped membrane structures, finding the use of undoped material improves ensemble spin lifetime by >5×. This work enables the fabrication of high-purity suspended thin films suitable for scalable photonics, mechanics, and quantum technologies in SiC.

Photoresponsivity enhancement of W-doped ZnO film/Silicon based devices via silver nanoparticles

Silver nanoparticles (Ag NPs) were deposited onto a 2 at.% Tungsten (W)-doped ZnO (WZO)/p-Silicon (p-Si) UV photodetector using a cost-effective sol–gel method. Top-view scanning electron microscopy (SEM) images confirmed the uniform coating of Ag NPs. Cross-sectional SEM analysis revealed a WZO film thickness of 167 nm, including the Ag NP layer. UV–Vis spectroscopy demonstrated high transparency with an average value of 79.5% for the Ag NPs-coated WZO film. The bandgap energy of this film was calculated to be 3.17 eV. The fabricated photodetector, comprising the Ag NP-modified WZO film and p-Si substrate, exhibited superior performance due to enhanced optical and electrical properties. Notably, the device achieved a responsivity (R*) of 4.83 A/W, a sensitivity (S*) of 60.82, and a detectivity (D*) of 5.06 × 1012 Jones. Compared to the unmodified WZO/p-Si device, the Ag NP-coated photodetector displayed significant improvements: a 26% increase in R*, a 79% increase in S*, and a 53% increase in D*. These findings highlight the potential of incorporating metal nanoparticles into photosensitive devices to optimize light-matter interactions.

Ultrawideband microwave metamaterial absorber with excellent absorption performance and high optical transparency based on double-layer mesh structures

Achieving microwave absorbers that combine wideband and excellent absorption performance with high optical transparency remains a significant challenge in the field of radar stealth. In this paper, an ultrawideband metamaterial absorber consisting of double-layer mesh structures and two transparent dielectric layers is proposed. In the absorption layer, an indium tin oxide (ITO) mesh pattern, equivalent to an RL circuit (series connection of resistance R and inductance L) to reduce design complexity, enhances the optical transparency of the absorber when combined with a mesh structure in the shielding layer. The polycarbonate (PC) cover plate is innovatively introduced to adjust the impedance matching, improving the absorbing bandwidth and angular stability. Based on the equivalent circuit model (ECM), optimization of the circuit parameters for the designed unit cell is conducted with the genetic algorithm (GA) and exhibits excellent absorption performance. Simulation and experiment results show that the reflection coefficient of the sample fabricated by the laser etching process is below -20 dB from 7.78 GHz to 12.58 GHz, covering the whole X band and reaching a relative bandwidth of 47.2%. Moreover, the average optical transmittance of the designed absorber is fixed at 81% in the visible region of 400–700 nm. The proposed metamaterial absorber with excellent absorption performance and high optical transparency provides a new avenue for the research and development of stealth and electromagnetic compatibility (EMC).

Bioinspired Conductivity-Enhanced, Self-Healing, and Renewable Silk Fibroin Hydrogel for Wearable Sensors with High Sensitivity.

The development of silk fibroin-based hydrogels with excellent biocompatibility, aqueous processability, and facile controllability in structure is indeed an exciting advancement for biological research and strain sensor applications. However, silk fibroin-based hydrogel strain sensors that combine high conductivity, high stretchability, reusability, and high selectivity are still desired. Herein, we report a simple method for preparing double-network hydrogels including silk fibroin and poly(acrylic acid) sodium-polyacrylate (PAA-PAAS) networks. The conformation and aggregate of silk fibroin could be facilely tuned by both ions and pH resulting from the PAA-PAAS network. The optimized hydrogel exhibits intriguing properties, such as high conductivity (3.67 S/m) and transparency, high stretchability (1186%) with a tensile strength of 110 kPa, good adhesion properties, reversible compression, self-healing, and high sensitivity (GF = 10.71). This hydrogel strain sensor can detect large-scale and small human movements in real time, such as limb movements, heartbeats, and pulse. Additionally, its ability to adsorb water and recover effectiveness after losing water from air with 90% humidity along with the capability for low-temperature motion detection facilitated by ethylene glycol further enhance its practical utility. This work offers a novel and simple approach to design flexible bionic strain sensors.

Design of a Multifunctional Resin-Based Outdoor Spherical Robot Shell for Ultrahigh Visible to Near-Infrared Transmittance and Mid-Infrared Radiative Cooling.

As robots undertake increasingly complex tasks, such as real-time visible image sensing, environmental analysis, and weather monitoring under harsh conditions, design of an appropriate robot shell has become crucial to ensure the reliability of internal electronic components. Several key factors, such as the cooling efficiency, visible transparency, mechanical performance, and weathering resistance of the shell material, are proposed in this research to ensure future robot functionality. In this study, a polymeric double-layered shell for fabrication by stereolithography 3D printing was designed, featuring a porous outer layer and a spherical inner shell. The inner spherical shell provides approximately 90% transmission in the visible to near-infrared wavelength range (450-1050 nm) and ensures the proper functioning of the optical devices, such as cameras, lidar, and solar cells, inside the robot. In addition, the inner shell material displays high emittance in the mid-infrared range (5-20 μm) to facilitate effective radiative cooling and protect the robot control system from thermal damage. The 3D-printed inner shell is exposed to a real environment for three months, and its stable optical and mechanical performance confirms its weather resistance ability. Moreover, the 3D-printed outer robot shell promotes mechanical strength while the robot is moving. The optimal 50% porous outer shell is designed to protect the inner shell from continuous moving impact. Finite element simulations are also used to show that the 50% porosity of the outer shell significantly reduces the strain energy upon impact. Compared with a conventional single-layer design with a strain energy of 130 mJ, the double-layered shell with 50% porosity exhibits a reduced strain energy of 22.09 mJ. This double-layered design, which offers excellent weather resistance, high visible transparency, and effective radiative cooling, is promising for future applications in both land and water robot shells.

Broadband, Single‐Layered, and Optically Transparent Reflective Phase‐Shifting‐Surface Array for Beam Manipulation and Enhanced Wireless Communications

AbstractOptically transparent electromagnetic devices play a crucial role in modern society, yet conventional optically transparent millimeter‐wave devices suffer from high return loss, limited phase shift, narrow bandwidth, high profile, and low optical transparency. Current materials, fabrication processes, and design methodologies restrict the development of high‐performance optically transparent reflective phase‐shifting‐surface arrays or reflectarrays. To address this, a design concept for broadband, single‐layered, and optically transparent reflectarray antennas is reported, which can be integrated with glass windows for beam manipulation and enhanced indoor signal coverage and wireless communications. The proposed reflectarray element employs a single‐layered cyclic olefin copolymer (COC) medium as the dielectric substrate, with fine metal line (FML) patterns under 50 µm width to create multi‐resonant structures for phase range broadening. This architecture combines multi‐resonant phase‐shifting elements with minimal FML structures and low‐loss COC substrate, achieving exceptional antenna performance while ensuring high optical transparency. Wireless communication transmission experiments validate the functionality and performance advantages of the fabricated optically transparent reflectarray. These results substantiate the immense potential and broad application prospects of the novel optically transparent COC dielectric material, the FML structure, and the proposed design concepts and methods in advancing high‐performance optically transparent reflectarrays and related communication systems.

Enhanced in-glass nonlinear optical modulation by coupling thin ENZ film with a femtosecond laser-written skimming waveguide

Glass-based photonic and electronic chips are attractive due to the high transparency, strong mechanical strength and biocompatibility of such substrates, or where low-loss connections to fiber-optic networks are required. However, efficient nonlinear optical modulation is difficult to achieve in ordinary silicate glass substrates, due to their inherent small optical nonlinearity in the broadband transparency window. In this paper, by integrating low-loss skimming waveguides using femtosecond laser pulses, we report a general strategy to significantly enhance the nonlinear response of glass photonic circuits based on the evanescent-coupling of an epsilon-near-zero (ENZ) thin film with the skimming waveguides. The fabricated device exhibits flexible tuning of absorptive optical nonlinearity between saturable absorption and reverse saturable absorption. This work provides what we believe to be a new method for optical switches and modulators that could offer potential solutions for 3D high-density photonic integration with dynamic programmability.

High Glass Transition PEcBT and PEPecBT Copolyesters Synthesized by Direct Esterification Route

ABSTRACT2,2,4,4‐Tetramethyl‐1,3‐cyclobutanediol (CBDO) based copolyesters like poly(cyclohexane dimethylene‐co‐2,2,4,4‐tetramethyl cyclobutylene terephthalate) (PCcBT) has high transparency, heat‐resistance and safety and has been commercialized to replace bisphenol A polycarbonate in food contact applications. However, its synthesis and processing suffer from CBDO sublimation, composition deviation and relatively poor thermal stability. In order to obtain transparent heat‐resistant CBDO‐based copolyesters with improved synthesis robustness and thermal stability, poly(ethylene co‐tetramethyl cyclobutene terephthalate (PEcBT)) copolyesters were synthesized from ethylene glycol (EG), CBDO, and terephthalic acid (TPA) via direct esterification route, and the structure–property was studied. It is found that the presence of EG effectively inhibited the sublimation of CBDO, and the resulting PEcBT copolyesters had reasonably good thermal stability so that the melt polycondensation proceeded smoothly without serious foaming. PEcBT copolyesters with intrinsic viscosity ([η]) over 0.60 dL/g were successfully synthesized at copolymer composition (ϕcBT) up to 67 mol%. A quantitative relationship between Tg and its influence factors is established. The copolyesters with ϕcBT of 48–62 mol% displayed Tg of 126°C–144°C, flexible tensile behavior, satisfactory tensile properties and reasonably good impact performance. Ternary PEPecBT copolyesters were also synthesized using 1,5‐pentanediol as another diol comonomer to improve toughness of the materials.

Liquid-based encapsulation for implantable bioelectronics across broad pH environments

Wearable and implantable bioelectronics that can interface for extended periods with highly mobile organs and tissues across a broad pH range would be useful for various applications in basic biomedical research and clinical medicine. The encapsulation of these systems, however, presents a major challenge, as such devices require superior barrier performance against water and ion penetration in challenging pH environments while also maintaining flexibility and stretchability to match the physical properties of the surrounding tissue. Current encapsulation materials are often limited to near-neutral pH conditions, restricting their application range. In this work, we report a liquid-based encapsulation approach for bioelectronics under extreme pH environments. This approach achieves high optical transparency, stretchability, and mechanical durability. When applied to implantable wireless optoelectronic devices, our encapsulation method demonstrates outstanding water resistance in vitro, ranging from extremely acidic environments (pH = 1.5 and 4.5) to alkaline conditions (pH = 9). We also demonstrate the in vivo biocompatibility of our encapsulation approach and show that encapsulated wireless optoelectronics maintain robust operation throughout 3 months of implantation in freely moving mice. These results indicate that our encapsulation strategy has the potential to protect implantable bioelectronic devices in a wide range of research and clinical applications.

Highly Transparent Superhydrophobic Coatings for Prevention of Raindrop Adhesion on Rearview Mirrors.

The adhesion of raindrops on car rearview mirrors poses a significant threat to traffic safety due to the resulting blurred vision. Transparent superhydrophobic coatings have emerged as a potential solution to this problem. However, the development of transparent superhydrophobic coatings is often hampered by complex preparation procedures, high costs, and limited substrate compatibility, rendering them unsuitable for practical applications. Herein, we present a facile spraying method for fabricating a transparent superhydrophobic perfluorodecyl polysiloxane-modified silica (SiO2@FD-POS) coating with a high transparency of approximately 91%, which is comparable to that of bare glass (∼93%). This coating can be applied onto various substrates, including paper, polycarbonate goggles, and PET fabric, without altering their inherent color. Furthermore, the SiO2@FD-POS coating demonstrates robust mechanical, thermal, and UV durabilities, which are crucial for its application in outdoor conditions. When applied to a rearview mirror, this coating effectively prevents raindrops from adhering on the surface for over 60 min during moderate rainfall, maintaining a clear reflection throughout. Therefore, the SiO2@FD-POS coating holds significant potential in enhancing drivers' visibility during rainy conditions, thus contributing to high driving safety.

Transparent Poly(amide-imide)s with Low Coefficient of Thermal Expansion from Trifluoromethylated Trimellitic Anhydride

Making transparent aromatic polymers with high Tg and low thermal expansion behavior, like glass, is challenging. We report transparent and soluble poly(amide-imide)s (PAIs) with high dimensional stability synthesized from the new monomer, trifluoromethylated trimellitic anhydride. Insertion of trifluoromethyl (CF3) groups into polymer chains enhanced solubility and the optical properties of polymers without sacrificing high thermal stability. Model reactions were utilized to study how the CF3 group in trimellitic anhydride affects the polymerization reaction with aromatic diamine monomers, and a series of new PAIs were synthesized. All the polymers were soluble in polar organic solvents and can be solution-cast into nearly colorless and flexible freestanding films. The obtained PAI films possessed high thermal stability (Td5: 437–452 °C in N2) and high transparency (84~87% transmittance at 550 nm). Interestingly, PAIs prepared in this study exhibited high thermodimensional stability with low CTE values from 9 to 26 ppm/°C. The transparent poly(amide-imide) film with low CTE value finds its application in display and optical devices that require flexible and transparent form factors.

Laminated Two-Terminal All-Perovskite Tandem Solar Cells with Transparent Conductive Adhesives.

Established sequential deposition of multilayer two-terminal (2T) all-perovskite tandem solar cells possesses challenges for fabrication and limits the choice of materials and device architecture. In response, this work represents a lamination process based on a transparent and conductive adhesive that interconnects the wide-bandgap (WBG) perovskite top solar cell and the narrow-bandgap (NBG) perovskite bottom solar cell in a monolithic 2T all-perovskite tandem solar cell. The transparent conductive adhesive (TCA) layer combines Ag-coated poly(methyl methacrylate) microspheres with an optical adhesive. The TCA is employed as a recombination junction, achieving self-encapsulation with high transparency and good conductivity. A high vertical electrical conductivity is realized by optimizing the distribution of microspheres using a novel solidification strategy that employs UV curing and drying at 85 °C at low pressure. In addition, uniform and dense bilayer hole transport layers are realized by vapor-phase evaporation, which facilitates the application of the TCA and achieves pinhole-free buried interfaces in both the WBG perovskite top solar cell and the NBG perovskite bottom solar cell. Using these two strategies, losses in fill factor (FF) and open-circuit voltage (VOC) of the 2T all-perovskite tandem solar cell are reduced, achieving a respectable power conversion efficiency up to 18.2% for the lamination of the all-perovskite tandem solar cell. The laminated tandem solar cell retains ∼93% of initial efficiency after exposure in ambient air (30-70 RH% and 20-35 °C) for ∼30 days.

Rubber-like Deep Eutectic Solvent-Assisted Poly(N-acryloylglycinamide) Hydrogel for Highly Sensitive Pressure Detecting.

Deep eutectic solvent (DES)-based conductive hydrogels have attracted great interest in the building of flexible electronic devices that can be used to replace conventional temperature-intolerant hydrogels and expensive ionic liquid gels. However, current DES-based conductive hydrogels obtained have limited mechanical strength, high hysteresis, and poor microdeformation sensitivity of the assembled sensors. In this work, a rubber-like conductive hydrogel based on N-acryloylglycinamide (NAGA) and DES (acetylcholine chloride/acrylamide) has been synthesized by a one-step method. The prepared conductive PNAGA-DES hydrogel has exhibited excellent mechanical strength, stability, and resilience during the long-term loading-unloading cycles, endowed with service durability. Besides, the as-prepared PNAGA-DES also possesses high transparency, high conductivity, and favorable antienvironmental disturbance, which can enhance the designability and robustness of the PNAGA-DES-based devices. Based on the remarkable properties, the PNAGA-DES hydrogel can be used for wearable pressure-strain sensors with high sensitivity of tiny strain for transferring information (gauge factor (GF) = 8.18, 0.2-2% strain) and long-term stability. Furthermore, it can also sensitively detect the large strain of human motion, showing potential application in information interaction and wearable electronics.