Showing papers on "Transmittance published in 2022"

Highly transmitted silver nanowires-SWCNTs conductive flexible film by nested density structure and aluminum-doped zinc oxide capping layer for flexible amorphous silicon solar cells

Abstract: Indium tin oxide (ITO) is widely used in transparent conductive films (TCFs); however, several disadvantages, such as high cost and toxicity of indium, limit its applications. Therefore, it is necessary to develop other materials that can replace ITO. Silver nanowires or single walled carbon nanotubes (SWCNTs) have attracted considerable interest owing to their unique electrical, optical, and thermal stabilities, and thus, they are ideal for transparent electrodes for flexible or stretchable devices. In this study, we develop a novel architecture of composite TCFs on a polyethylene naphthalate (PEN) flexible substrate. Herein, the silver nanowires-SWCNTs films with nested density structure were fabricated through ultrasonic spraying technology by varying the spraying width. For achieving enhanced transmittance, we combined the larger irregular grids and holes with fewer nanowires stacked in the longitudinal direction, more optical channels, and good carrier transport. Thereafter, aluminum-doped zinc oxide (AZO) was used as capping to the structure for enhancing the optical properties of the TCFs. The silver nanowires-SWCNTs/AZO (ASA) bilayer was obtained in the optimized architecture, which showed superior optoelectronic performance to that shown by commercial ITO with a high optical transmittance of 92% at the wavelength of 550 nm and low sheet resistance of 17 Ω/sq. In the specially structured conductive film, the significant improvement in the transmittance and uniformity of the sheet resistance was attributed to the effective nanowire junction contact compared to that in ordinary structure of silver nanowires, which reduced the mean density of small clusters of nanowires. Compared with the silver nanowires-SWCNTs films, the ASA bilayer film exhibited excellent resistance to boiling, mechanical bending (10,000 cycles), and CO2 plasma. Moreover, the sheet resistance of ASA changed slightly after the tape tests, thereby illustrating a strong adhesion to the PEN substrate after the enclosure of AZO. Meanwhile, the AZO capping layer can enhance the optical transmittance between 600 and 1500 nm. In addition, the amorphous silicon photovoltaic devices with flexible ASA TCFs exhibited a power conversion efficiency (PCE) of 8.67%. After bending for 3000 times, the PCE was decreased to 8.20%, thereby demonstrating the potential of developed films to replace traditional ITO.

Recent Advances on Dual‐Band Electrochromic Materials and Devices

Abstract: Dual‐band electrochromism is a phenomenon where materials can independently regulate the transmittance of visible (VIS) and near‐infrared (NIR) light. Owing to their bistability, low energy consumption, and independent control over VIS and NIR regions, dual‐band electrochromic (EC) devices have been of great significance to fully harnessing VIS and NIR light and building an energy‐saving society. The past several years have witnessed the efforts put in developing novel EC materials to improve their dual‐band optical performance through altering their composition, structural, and physicochemical features, which determine the optical behavior of dual‐band EC devices. In this review, the concept, significance, working principle, and key influence factors of dual‐band electrochromism are briefly introduced. Next, the up‐to‐date progress of dual‐band EC materials including inorganic, organic, and composites materials are summarized, with a focus on material design, device fabrication, and performance optimization. Finally, the challenges and perspectives of dual‐band EC materials and devices are also presented.

Efficient Semitransparent Layer‐by‐Layer Organic Photovoltaics via Optimizing Wide Bandgap and Narrow Absorption Polymer Layer Thickness

Abstract: Layer‐by‐layer organic photovoltaics (LbL‐OPVs) are fabricated using wide bandgap polymer D18 with narrow photon harvesting range in visible light region and narrow bandgap small molecular N3 with strong near‐infrared photon harvesting; the only difference is D18 layer thickness adjusted by spin coating speed. A 15.75% power conversion efficiency (PCE) is obtained from the LbL‐OPVs with D18 layer prepared under 7000 round per minute of spin coating condition; the corresponding D18/N3 layers have a 52.06% of average visible transmittance (AVT) in the spectral range from 370 to 740 nm. Based on the optimized D18/N3 layers, semitransparent LbL‐OPVs are built with 1 nm Au/(10, 15, 20 nm) Ag as the top electrode. The PCE and AVT of semitransparent LbL‐OPVs can be simultaneously adjusted by altering Ag layer thickness due to its variable reflectance and conductivity of top electrode dependence on Ag layer thickness. The PCE/AVT of 12.58%/22.81%, 13.80%/15.09%, and 14.85%/9.48% can be individually achieved from the semitransparent LbL‐OPVs with 10, 15, or 20 nm‐thick Ag layer, which should be among the highest values of semitransparent OPVs based on bulk heterojunction or LbL structures. Adjusting donor layer thickness may be an effective method to construct efficient semitransparent LbL‐OPVs.

Femtosecond laser textured porous nanowire structured glass for enhanced thermal imaging

Abstract: Tingni Wu (吴婷妮), Zhipeng Wu (吴志鹏), Yuchun He (何玉春), Zhuo Zhu (朱 卓), Lingxiao Wang (王凌霄), and Kai Yin (银 恺) 1 Hunan Key Laboratory of Nanophotonics and Devices, School of Physics and Electronics, Central South University, Changsha 410083, China 2 State Key Laboratory of High Performance and Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China

Ultrafast Shaped Laser Induced Synthesis of MXene Quantum Dots/Graphene for Transparent Supercapacitors.

Abstract: xxxx This article is protected by copyright. All rights reserved.

Semitransparent Organic Solar Cells with Efficiency Surpassing 15%

Abstract: Semitransparent organic solar cells (ST‐OSCs) have promising prospects for building or vehicle integrated solar energy harvesting with energy generation and see‐through function. How to achieve both an adequate average visible transmittance (AVT) and high‐power conversion efficiency (PCE) is always the key issue. Herein, a simple but effective strategy for constructing high performance ST‐OSCs by introducing a small molecule [2‐(9‐H‐Carbazol‐9‐yl) ethyl] phosphonic acid (2PACz) into a low‐donor content active layer is reported. The fill factor is improved from 70.5% to 75.5% and correlated to the mitigated charge recombination and strengthened charge extraction, further ascribed to the enhanced build‐in potential, reduced charge transport resistance, and favorable film morphology. By combining the unique nature of 2PACz, that can spontaneously form in situ self‐organized hole transport interlayers under bulk‐heterojunction films, PEDOT‐free ST‐OSCs with a PCE of 15.2%, amongst the highest values in this field, is achieved with an AVT of 19.2%. Moreover, an outstanding light utilization efficiency of 3.39% is also obtained with an AVT of 30.0% and a PCE of 11.3% in a translucent device by tuning the electrode. The work demonstrates a new and simple strategy for achieving excellent AVT and PCE in ST‐OSCs with simplified device structure.

3D Printed High Performance Silver Mesh for Transparent Glass Heaters through Liquid Sacrificial Substrate Electric-Field-Driven Jet.

Abstract: Transparent glass with metal mesh is considered a promising strategy for high performance transparent glass heaters (TGHs). However, the realization of simple, low-cost manufacture of high performance TGHs still faces great challenges. Here, a technique for the fabrication of high performance TGHs is proposed using liquid sacrificial substrate electric-field-driven (LS-EFD) microscale 3D printing of thick film silver paste. The liquid sacrificial substrate not only significantly improves the aspect ratio (AR) of silver mesh, but also plays a positive role in printing stability. The fabricated TGHs with a line width of 35 µm, thickness of 12.3 µm, and pitch of 1000 µm exhibit a desirable optoelectronic performance with sheet resistance (Rs ) of 0.195 Ω sq-1 and transmittance (T) of 88.97%. A successful deicing test showcases the feasibility and practicality of the manufactured TGHs. Moreover, an interface evaporator is developed for the coordination of photothermal and electrothermal systems based on the high performance TGHs. The vapor generation rate of the device reaches 10.69 kg m-2 h-1 with a voltage of 2 V. The proposed technique is a promising strategy for the cost-effective and simple fabrication of high performance TGHs.

Tailoring Silver Nanowire Nanocomposite Interfaces to Achieve Superior Stretchability, Durability, and Stability in Transparent Conductors.

Abstract: Silver nanowires (AgNWs) have been considered as a promising candidate for transparent stretchable conductors (TSCs). However, the strong interface mismatch of stiff AgNWs and elastic substrates leads to the stress concentration at their interface and ultimately the low stretchability and poor durability of TSCs. Here, to address the interfacial mismatch of AgNWs-based TSCs we put forward a universal interface tailoring strategy that introduces the mercapto compound as the intermediate cross-linked layer. The mercapto compound strongly interacts with the AgNWs, forming a dense protective layer on their surface to improve their corrosion resistance, and reacts with the polymer substrate, forming a buffer layer to release the concentrated stress. As a result, the optimized TSCs showed superior stretchability (160%), exceptional durability (230 000 cycles), competent optoelectrical performance (18.0 ohm·sq-1 with a transmittance of 86.5%), and prominent stability. This work provides clear guidance and a strong impetus for the development of transparent stretchable electronics.

Flexible transparent electromagnetic interference shielding films with silver mesh fabricated using electric-field-driven microscale 3D printing

Abstract: In order to address the challenging issue regarding the high-efficiency and low-cost fabrication of high-performance flexible transparent electromagnetic interference (EMI) shielding films, a novel approach is proposed to produce flexible transparent EMI shielding film with silver mesh based on electric-field-driven (EFD) microscale 3D printing. The manufacturing principle and the reasonable process parameters are revealed with a series of experiments. Following this fabricating scheme and self-developed EFD micro-scale 3D printer, three flexible transparent EMI shielding films having a size of 60 mm × 60 mm and a line width of 26 μm are achieved utilizing the low-temperature nano silver paste (75% silver content and 350 dPa·s (25 °C) dynamic viscosity). The experimental result shows that the adhesive force between the sintered silver mesh and the polyethylene terephthalate (PET) substrate is measured to be 5B with 3 M scotch tape. The bending experiment proves the excellent mechanical flexibility of the flexible transparent EMI shielding film. In different chemical environments and ultrasonic vibration environments, the silver mesh flexible transparent EMI shielding film can still maintain good electrical properties. When the pitch of the silver mesh is 500 μm, the optical transmittance is 90.5% and the EMI shielding efficiency for the common medium-high frequency electromagnetic wave is greater than 26 dB. When the pitch is 300 μm, the optical transmittance is 84% and the shielding efficiency is higher than 32 dB. When the pitch is 150 μm, the optical transmittance is 69% and the shielding efficiency is higher than 34 dB. As a result, the proposed method provides a promising solution for mass producing high-performance silver mesh flexible transparent EMI shielding films at low cost and high throughput.

Ferroelectric crystals with giant electro-optic property enabling ultracompact Q-switches

Abstract: Relaxor-lead titanate (PbTiO3) crystals, which exhibit extremely high piezoelectricity, are believed to possess high electro-optic (EO) coefficients. However, the optical transparency of relaxor-PbTiO3 crystals is severely reduced as a result of light scattering and reflection by domain walls, limiting electro-optic applications. Through synergistic design of a ferroelectric phase, crystal orientation, and poling technique, we successfully removed all light-scattering domain walls and achieved an extremely high transmittance of 99.6% in antireflection film–coated crystals, with an ultrahigh EO coefficient r33 of 900 picometers per volt (pm V−1), >30 times as high as that of conventionally used EO crystals. Using these crystals, we fabricated ultracompact EO Q-switches that require very low driving voltages, with superior performance to that of commercial Q-switches. Development of these materials is important for the portability and low driving voltage of EO devices. Description Breaking down the domain walls Ferroelectric materials should make for decent optical components because of the change in refractive index with electric field. However, many of the best ferroelectrics have domain walls that scatter light and are not useful for optics applications. Liu et al. used a high-temperature poling method to remove the light-scattering domain walls in a lead ceramic ferroelectric. The material has a very high electro-optic coefficient and requires a very low driving voltage. This strategy may be useful for other materials and may help in the development of better optical devices. —BG High-temperature poling eliminates light-scattering domain walls in a relaxor ferroelectric.

Encoding and Tuning of THz Metasurface-Based Refractive Index Sensor With Behavior Prediction Using XGBoost Regressor

Abstract: We have investigated graphene-based three various refractive index sensors (split ring resonator (SRR), split ring resonator with thin wire (SRRTW), and thin wire (TW) refractive index sensors) for the encoding and sensing-based applications. The sensors are designed to detect the presence of hemoglobin biomolecules with high sensitivity. The results are analyzed in the form of transmittance, and electric field and detailed sensitivity analysis is also carried out for the proposed graphene-based refractive index sensors for four various concentrations of hemoglobin biomolecules. We have also investigated the sensor’s performance in terms of quality factor, Q, and figure of merit (FOM). The encoding of ‘0’ and ‘1’ is attained by varying the graphene chemical potential fulfilling the one-digit coding. An array of these sensors can then be used for encoding-based applications. The detailed analysis of reported sensors is also carried out by checking the effect of varying physical parameters such as substrate thickness, split ring gap, and thin wire width on tunability. These sensors can be applied in biomedical or encoding-based applications. Experiments are performed using XGBoost regressor to determine, whether simulation time and resources can be reduced by using regression analysis to predict the transmittance values of intermediate frequency or not. Experimental results prove that regression analysis using XGBoost Regressor can reduce the simulation time and resources by at least 70 percent.

In situ plasma cleaning of large-aperture optical components in ICF

Abstract: The organic contamination damage of large-aperture optical components limits laser energy improvement of inertial confinement fusion (ICF). In situ cleaning of large-aperture optical components via low-pressure plasma is expected to remove organic contaminants from the optical surface. Herein, low-pressure air plasma equipment was proposed and used on surfaces of SiO2 sol–gel antireflection (AR) films in situ by conducting experiments. Its electrical discharge parameters were investigated and optimized during plasma cleaning. Plasma diffusion characteristics and homogeneity in large-aperture windows were analyzed by optical emission spectroscopy. Dramatic degradation in the optical properties of components was observed after organic contamination for 5 h. Transmittance, laser-induced damage threshold and surface morphology observation results demonstrated that low-pressure air plasma removed the organic contaminants from the surface of sol–gel AR films without causing damage and metal contamination. After plasma cleaning, the hydrophilicity of the films increased significantly due to the increase in the polar components of surface free energy. The mechanism of plasma cleaning organic contaminants was confirmed by x-ray photoelectron spectroscopy measurements. These salient results provide a new alternative method for removing organic contaminants in situ from large-aperture optical components and a foundation for improving the energy output of the ICF system.

The impact of magnetized cold plasma and its various properties in sensing applications

Abstract: These analyses present a novel magnetized cold plasma-based 1D photonic crystal structure for detecting the refractive index of various bio-analytes. The proposed structure is designed with two photonic crystals composed of an alternating layer of right-hand polarization and left-hand polarization of the magnetized cold plasma material with a central defect layer. Transmittance characteristics of the structure are studied by employing the well-known transfer matrix method. Various geometrical parameters such as electron density, external magnetic field, thickness of odd and even layers of the multilayers, thickness of the sample layer, and incident angle are judiciously optimized to attain the best sensitivity, figure of merit, quality factor, signal-to-noise ratio, detection range and limit of detection. Finally, a maximum sensitivity of 25 GHz/RIU is accomplished with the optimized value of structure parameters, which can be considered as a noteworthy sensing performance.

Switchable Surface Coating for Bifunctional Passive Radiative Cooling and Solar Heating

Abstract: The ability to achieve dual‐mode thermal regulation for switchable heating and cooling on a single platform has thus far been challenged by the availability of suitable materials. The materials need to possess both high solar reflectance and high transmittance, necessitating large and small thicknesses in the same coating layer, respectively (i.e., the thickness constraint). Herein, for the first time, a single‐layer coating made in a facile one‐step process is reported, which exhibits rapid switch between high solar reflection (≈96.6%) and high solar transmission (≈86.6%). In the dry state, high solar reflectance and infrared (IR) emittance (>96% from 8 to 13 µm) enable passive radiative cooling, resulting in all‐day near/sub‐ambient temperatures in the demanding weather conditions of the tropical climate. Upon wetting, high transparency in the broadband range (0.3–2.5 µm) allows solar heating, leading to switchable thermal regulation. Such unprecedented performances are achieved through a unique hierarchical porous structure comprising of vertically aligned microscale pores in nanoscale pore matrix. This structure breaks the thickness constraint and broadens its applicability, in particular for seasonal areas with large temperature variation throughout the day.

Transparent and Flexible Electromagnetic Interference Shielding Materials by Constructing Sandwich AgNW@MXene/Wood Composites.

Abstract: Electromagnetic interference (EMI) shielding materials have attracted intensive attention with the increased electromagnetic pollution, which are required to possess high transparency and flexibility for applications in visualization windows, aerospace equipment, and wearable devices. However, it remains a challenge to achieve high-performance EMI shielding while maintaining excellent light transmittance. Herein, a sandwich composite is constructed by coating the core material of transparent wood (TW) with silver nanowire (AgNW)@MXene, exhibiting a maximum transmittance of 28.8% in the visible range and a longitudinal tensile strength of 47.8 MPa. The average EMI shielding effectiveness can reach up to 44.0 dB under X-band (8-12.4 GHz), ascribed to the increased absorption shielding induced by the multireflection of electromagnetic waves within microchannels of the TW layer and the interfacial polarization between AgNW and MXene. Simultaneously, large-scale EMI shielding films can be conveniently produced by our proposed method, which provides inspiration for the development of advanced EMI shielding materials for wide applications.

MATLAB Simulation-Based Theoretical Study for Detection of a Wide Range of Pathogens Using 1D Defective Photonic Structure

Abstract: The present 1D photonic biosensor is composed of two sub-PhCs of alternate layers made of GaP and SiO2. The period number of each PhC has been fixed to 3. Both these PhCs are joined together through a cavity region of air in which different analytes are to be filled one by one under the scope of this study. The theoretical findings of this work have been formulated with the help of the well-known transfer matrix method. Moreover, all the computations pertaining to this work have been carried out with the help of MATLAB software. The effect of change in cavity thickness and angle of incidence corresponding to a TE wave on the transmittance of the structure (AB)ND(AB)N has been studied theoretically which in turn determines the performance of the proposed biosensor. Various parameters, such as sensitivity (S), signal to noise ratio (SNR), figure of merit (FOM), resolution (RS), detection limit (LOD), quality factor (Q) and dynamic range (DR) have been theoretically calculated to evaluate the performance of the proposed design in true sense. The sensitivity of this structure varies between the highest and lowest values of 337.3626 nm/RIU and 333.0882 nm/RIU corresponding to water samples containing Pseudomonas aeruginosa cells and Bacillus anthracia cells, respectively, under normal incidence condition with a cavity thickness of 2.0 µm. The resolution (in nm) and LOD (in RIU) values of the proposed design are small enough and are significant for our structure. This study may also be helpful for distinguishing various microbiological samples under investigation and find suitable applications for discriminating bacterial cells from spores.

Pseudo‐Planar Heterojunction Organic Photovoltaics with Optimized Light Utilization for Printable Solar Windows

Abstract: The existing conformation of the active layer is defective for employment of semitransparent organic solar cells (ST‐OSCs) in solar windows. Herein, scalable solar windows are successfully printed by introducing a pseudo‐planar heterojunction (PPHJ) structure. The PPHJ structure can effectively improve the average visible transmittance (AVT) value while boosting the power conversion efficiency (PCE) of semitransparent devices due to the reduced optical loss. The universality of the PPHJ structure in the preparation of ST‐OSCs is proved. Furthermore, an inset of a superhydrophobic patterned soft insertion layer (PSIL) in the encapsulated window improves the waterproof performance without losing transparency. Accordingly, the semitransparent devices based on the 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6) system afford a maximal efficiency of 14.62%, with a considerable AVT of 20.42%, and the resultant solar windows achieve a stabilized efficiency of 13.34% with excellent waterproof performance. Moreover, the PCE of the unilateral broken solar windows retains 70.6% of the initial efficiency after being placed under simulated rainfall conditions for 1200 h at room temperature.

Analogue of electromagnetically induced transparency in square slotted silicon metasurfaces supporting bound states in the continuum

Abstract: In this work, a silicon metasurface designed to support electromagnetically induced transparency (EIT) based on quasi-bound states in the continuum (qBIC) is proposed and theoretically demonstrated in the near-infrared spectrum. The metasurface consists of a periodic array of square slot rings etched in a silicon layer. The interruption of the slot rings by a silicon bridge breaks the symmetry of the structure producing qBIC stemming from symmetry-protected states, as rigorously demonstrated by a group theory analysis. One of the qBIC is found to behave as a resonance-trapped mode in the perturbed metasurface, which obtains very high quality factor values at certain dimensions of the silicon bridge. Thanks to the interaction of the sharp qBIC resonances with a broadband bright background mode, sharp high-transmittance peaks are observed within a low-transmittance spectral window, thus producing a photonic analogue of EIT. Moreover, the resonator possesses a simple bulk geometry with channels that facilitate the use in biosensing. The sensitivity of the resonant qBIC on the refractive index of the surrounding material is calculated in the context of refractometric sensing. The sharp EIT-effect of the proposed metasurface, along with the associated strong energy confinement may find direct use in emerging applications based on strong light-matter interactions, such as non-linear devices, lasing, biological sensors, optical trapping, and optical communications.