Large Modulation Research Articles

Boosting the electrochromic performance of P-doped WO3 films via electrodeposition for smart window applications.

Electrochromic smart windows have attracted more attention from researchers due to their potential applications for energy conservation in buildings. As the most key component, the electrochromic layer is still limited by the complexity of the preparation process and poor performance, such as lower stability, slow response time, and low coloration efficiency. In this study, as a simple and expedient method, electrodeposition is successfully used to prepare amorphous WO3 films doped with P. By optimizing the amount of P in the PW-2 film, a large optical modulation of 80.8% at 550 nm is achieved, and the P-doped amorphous WO3 film also shows a fast response time, a high CE, and good cycling stability. The mechanism of the P-doped amorphous WO3 films to improve the electrochromic properties is as follows. Firstly, by appropriate phosphorus doping, the stress of the film is released, and the binding force is improved. Secondly, the films possess proper cracks, which accelerate the diffusion of ions. Thirdly, the films make the nanoparticles more uniform, and provide more active sites. Furthermore, the electrochromic smart windows based on the P-doped amorphous WO3 film display a large temperature difference of 11 °C, which indicates good solar thermal regulation ability, and promises practical applications for building energy conservation.

Amorphous bismuth and GO co-doped WO3 electrochromic film with fast-switching time and long-term stability.

The sol-gel process for fabricating electrochromic thin films is straightforward, offering advantages such as low cost and ease of compositional control. Herein we prepared GO-Bi-WO3 films with improved electrochromic performance using a simple sol-gel spin-coating method. The sample shows a fast-switching time (1.8 s for coloring and 1.8 s for bleaching), large optical modulation (85% at 630 nm), excellent stability (86.4% retention after 10 200 cycles), and high coloration efficiency (65.9 cm2 C-1). This work indicates the electrochromic performance of WO3-based films can be enhanced by incorporating GO, which provides an effective strategy for the rapid, safe, and efficient fabrication of electrochromic thin films.

Thermal Runaway in Thin Film PV: temperature profile modeling

Thermal runaway is a well known phenomena in degradation analysis of the CdS/CdTe thin film solar cells. The thin thickness of such devices can be deteriorated by the temperature fluctuations after a long enough time. We modeled the temperature profile of thin film devices considering the uniform and nonuniform distribution for temperature of the glass substrate and current flowing through TCO layer. In addition, the temperature profile of a hot spot at the edge of the device has been formulated and compared with the real data and fitting functions represented in a few literature. All the above modeling was based on the heat transfer equation considering the importance of thermal resistances. The convection and conduction resistances were introduced in the considered Biot number optimized for PV applications. The modeling presented in this paper can be extended to other solar cell structures or large scale modules. The current study suggests that the thickness and temperature dependencies of the thermal conductivity, convection and conduction resistance might be taken into account and be optimized in thermal runaway issues of thin film devices. The hot spot modeling suggests that the current flowing across the TCO layer can assist the thermal runaway and deformation of neighboring area.

Tunable multiband circular dichroism and asymmetric transmission enabled by chiral quasi-BICs in dielectric metasurfaces covered with graphene

High-Q chiral resonances have attracted great interest recently due to their practical photonic applications. For generating such resonances, chiral quasi-bound states in the continuum (quasi-BICs) have recently been proposed and experimentally demonstrated by many researchers, while their dynamic tunability has still not been discussed. In this work, we show multiband circular dichroism and asymmetric transmission based on high-Q chiral quasi-BICs in dielectric metasurfaces, which are dynamically tunable in the mid-infrared range by using graphene monolayers covering the metasurfaces. By changing the Fermi energy, the surface conductivity of graphene is tunable in a wide range, resulting in tunable chiroptical responses of the metasurfaces. Since the metasurfaces exhibit high-Q resonances with narrow linewidths, tuning the metasurfaces results in large modulation depths of circular dichroism and asymmetric transmission, which is of great importance for photonic applications, including tunable polarization manipulation and polarization-dependent detection.

Some dimensional-geometric modulations of the Stonehenge megalithic complex

The article is devoted to the modulated dimensional-geometric peculiarities of the Stonehenge megalith and continues the theme of our previous publications devoted to such megalithic objects as the “stone ship” Ales Stenar, small circle in Nabta Playa, and the outer “circle of stones” in Clava. By “modulation” we mean the use of a large module in the size of historical structures, quantitatively equal to the simple number of known historical linear measures (the simple number 37 is most often identified). A more detailed justification of the method is given in “Hypothesis of the dimensional-geometric scheme of the Nabta-Playa megalith landscape monument” including connections with the dimensional-geometric features of ancient Egyptian architecture are also shown there.

Transforming patterned defects into dynamic poly-regional topographies in liquid crystal oligomers.

We create high-aspect-ratio dynamic poly-regional surface topographies in a coating of a main-chain liquid crystal oligomer network (LCON). The topographies form at the topological defects in the director pattern organized in an array which are controlled by photopatterning of the alignment layer. The defect regions are activated by heat and/or light irradiation to form reversible topographic structures. Intrinsically, the LCON is rubbery and sensitive to temperature changes, resulting in shape transformations. We further advanced such system to make it light-responsive by incorporating azobenzene moieties. Actuation reduces the molecular order of the LCON coating that remains firmly adhered to the substrate which gives directional shear stresses around the topological defects. The stresses relax by deforming the surfaces by forming elevations or indents, depending on the type of defects. The formed topographies exhibit various features, including two types of protrusions, ridges and valleys. These poly-regional structures exhibit a large modulation amplitude of close to 60%, which is 6 times larger than the ones formed in liquid crystal networks (LCNs). After cooling or by blue light irradiation, the topographies are erased to the initial flat surface. A finite element method (FEM) model is adopted to simulate structures of surface topographies. These dynamic surface topographies with multilevel textures and large amplitude expand the application range, from haptics, controlled cell growth, to intelligent surfaces with adjustable adhesion and tribology.

MSLKNet: A Multi-Scale Large Kernel Convolutional Network for Radar Extrapolation

Radar echo extrapolation provides important information for precipitation nowcasting. Existing mainstream radar echo extrapolation methods are based on the Single-Input-Single-Output (SISO) architecture. These approaches of recursively predicting the predictive echo image with the current echo image as input often results in error accumulation, leading to severe performance degradation. In addition, the echo motion variations are extremely complex. Different regions of strong or weak echoes should receive different degrees of attention. Previous methods have not been specifically designed for this aspect. This paper proposes a new radar echo extrapolation network based entirely on a convolutional neural network (CNN). The network uses a Multi-Input-Multi-Output (MIMO) architecture to mitigate cumulative errors. It incorporates a multi-scale, large kernel convolutional attention module that enhances the extraction of both local and global information. This design results in improved performance while significantly reducing training costs. Experiments on dual-polarization radar echo datasets from Shijiazhuang and Nanjing show that the proposed fully CNN-based model can achieve better performance while reducing computational cost.

Achieving neutral-tinted and energy-efficient electrochromic device enabled by sputtered tungsten-niobium-oxygen film for smart windows

WO3 based electrochromic device (ECD) is becoming the mostly-used one for smart windows, however, in WO3 tinted state, the intrinsically deep blue and strong infrared (IR) light absorption, resulting in a habitant discomfortableness and also an enhanced thermal gain from the heated device surface, severely restrict its diversified applications. Herein, we firstly conduct a kind of columnarly-grown and amorphous WO3 film with high concentration of niobium doping (Nb/(Nb+W) = 54.1 at.%). This film is fabricated via sputtering a home-made ceramic target, and subsequently improved by a rapid thermal annealing (RTA) process. Comparing with the conventional WO3, the newly-established system owns not only basic EC properties comprising large light modulation range, fast response, and long-term electrochemically cyclic stability, but also a neutral-tinted color (a* = −1.5, b* = 1.0) as well as a relatively lower IR absorption (63.7 %) in tinted state. These outstanding performances enable the assembled ECD with neutral color (a* = 0.6, b* = −2.7) and a higher energy efficiency in cutting down the interior space air temperature about 4.3 °C in its fully-tinted state, underscoring the potential of the tungsten-niobium-oxygen for commercially viable ECDs.

SPLConv: Channel-Separated Convolution Using Large Convolution Kernels

In modern society, chips play a crucial role in various aspects of everyday life. Nevertheless, the diverse chip manufacturing processes can introduce defects, making the detection of faulty chips imperative. Convolutional neural networks (CNNs) are extensively employed in computer vision due to their ability to deliver high-performance results. However, this comes at the expense of significant computational resources. Current research focuses on employing pruning or quantization techniques to minimize the size of model parameters and investigate the development of lightweight models. This paper proposes a large depth-wise convolutional module called split-based large convolutional (SPLConv), which is devised and optimized from the perspective of split-based convolutional operations (SPConv). SPLConv not only disregards redundant features in the convolutional layer but also enhances spatial information capture, thereby mitigating excessive computational overhead. Experiment demonstrate that SPLConv effectively reduces complexity and computational cost while delivering commendable performance.

Transparent-to-Brown-Black Patterned Electrochromic Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) exhibit promising electrochromic (EC) performance owing to their porous structure, regular channel, and tunable component characteristics. However, few reports focus on MOF materials with the EC performance of a transparent to brown-black (neutral colored state) change that is more suitable for smart windows. In this work, we proposed a strategy for synthesizing MOF (named Ni-BPY) EC materials and corresponding films fabricated via a low-cost electrostatic spray deposition technique. The obtained film exhibits excellent EC performance with a neutral color change from transparent to brown-black, a large optical modulation of 70% at 430 nm, and a fast response within 10 s. Benefiting from good electrical and chemical stability, the Ni-BPY film can be cycled over 500 times. Notably, the Ni-BPY MOF film also delivers a stepwise-controlled process during the bleached state due to its porous characteristics. In addition, the unique color variation of the Ni-BPY film derives from the redox reaction of the Ni metal node between Ni2+ and Ni3+, which is verified by the in situ potential-dependent Raman and X-ray photoelectron spectroscopy (XPS) measurement. As a proof of application, the patterned Ni-BPY EC films and devices are additionally constructed to demonstrate their potential application in electronic tags and logo displays.

Fabrication Knowledge and Techniques for Multiporous-Layered-Electrodes Perovsekite Solar Cells (MPLE-PSCs)

Multiporous-Layered-Electrodes Perovsekite Solar Cells (MPLE-PSCs) shows high stability (for 7000 h at 100 degree C; for 10,000 h under 1-Sun irradiation, for 3,000 h at 85%RH-85 degree C), adequate efficiency (11.5% by large modules), and low cost by fully-printed fabrication systems. In oder to fabricate good modules of MPLE-PSCs, good techniques and knowledges should be gathered up for the commercialization. In this conference, our group will show the efforts for the cost-effective commercially-available fully-printed MPLE-PSCs.

High-Performance Electrochromic Devices Based on Size-Controlled 2D WO3 Nanosheets Prepared Using the Intercalation Method.

It is difficult to obtain ultrathin two-dimensional (2D) tungsten trioxide (WO3) nanosheets through direct exfoliation from bulk WO3 in solution due to the strong bonding between interlayers. Herein, WO3 nanosheets with controllable sizes were synthesized via K+ intercalation and the exfoliation of WO3 powder using sonication and temperature. Because of the intercalation and expansion in the interlayer distance, the intercalated WO3 could be successfully exfoliated to produce a large quantity of individual 2D WO3 nanosheets in N-methyl-2-pyrrolidone under sonication. The exfoliated ultrathin WO3 nanosheets exhibited better electrochromic performance in an electrochromic device than WO3 powder and exfoliated WO3 without intercalation. In particular, the prepared small WO3 nanosheets exhibited excellent electrochromic properties with a large optical modulation of 41.78% at 700 nm and fast switching behavior times of 9.2 s for bleaching and 10.5 s for coloring. Furthermore, after 1000 cycles, the small WO3 nanosheets still maintained 86% of their initial performance.

A flexible electrochromic device with variable infrared emissivity based on W18O49 nanowire cathode and MXene infrared transparent conducting electrode

Electrochromism with tunable infrared (IR) responses has emerged as an intriguing technology for adaptive IR camouflage and radiative thermal management. Its current development is however hindered by low IR emissivity modulation and unsatisfactory cycle life. Herein, a flexible IR electrochromic device with large IR emissivity modulation and high stability is fabricated by combining an oxygen-deficient W18O49 nanowire cathode and a MXene-based IR transparent conducting electrode. The nanowire structure and abundant oxygen vacancies of W18O49 works in synergy with the high IR transparence of the MXene conducing electrode, to provide the IR emissivity to vary from 0.8 to 0.4 within 3–5 μm (△ε = 0.4), and from 0.77 to 0.3 within 8–14 μm (△ε = 0.47). A long cycle life of more than 2000 cycles was also verified, which could be attributed to the high stability of W18O49 and no material phase transition during cycling. This work demonstrates a viable pathway to design and build high performance flexible IR electrochromic devices for adaptive thermal management.

Enhancement of mid-infrared saturable absorption of graphene by compositing with PbSe for ultra-short pulse lasers in the ∼ 2.8 to ∼ 4 μm band

The suitably large modulation depth of the saturable absorber (SA) is crucial to obtaining short pulse lasers via passive Q-switching or mode-locking techniques. Graphene could theoretically be used as a mid-infrared (mid-IR) SA due to its zero band-gap. However, the low modulation depth of graphene in the mid-IR region limits its applications. In this work, to improve the mid-IR modulation depth of graphene, a strategy of functionalizing graphene with narrow-band gap semiconductors was adopted. Graphene/PbSe (G/PbSe) composite was synthesized by a facile hydrothermal process and the reflective G/PbSe SA was prepared by spin-coating method. The saturation absorption properties were investigated by the open aperture Z-scan technique. The results indicated that the saturation absorption properties of G/PbSe SA were largely enhanced, and the modulation depth was increased from 3.02 % to 5.4 % at ∼ 2.8 μm and from 2.5 % to 6.4 % at ∼ 4 μm compared with pure graphene. Moreover, with the as-prepared reflective G/PbSe SA, passively Q-switched Er:YAP laser operation at ∼ 2.8 µm was realized. At the pump power of 6.78 W, the pulse train with pulse width of 326 ns and repetition rate of 107 kHz was obtained, and the average output power was 498 mW. This study presents a way for preparing graphene-based mid-IR SAs for short pulse mid-IR lasers.

Enhanced Interband Transition in FeCoNiAlTi High‐Entropy Alloy for Ultrafast Nonlinear Optical Applications

AbstractHigh‐entropy alloys (HEAs) possess superior mechanical, thermal, and electronic properties, which attract great interest in the fields of photothermal, electrocatalysis, and magnetic applications. Herein, the nonlinear optical properties of FeCoNiAlTi HEA with a large specific surface area for the first time is investigated. Owing to the strong d–d interaction, the interband transition near the Fermi level could be enhanced in HEAs, leading to broadband optical absorption. Excitation with the picosecond laser source, the FeCoNiAlTi HEA possesses saturable absorption with a large modulation depth of 7.61% and 30.47% at 1 and 1.5 µm, respectively. Furthermore, at the higher excitation level at 1.5 µm, the saturable absorber exhibits a typical reverse saturable absorption property. Subsequently, the FeCoNiAlTi HEA on the tapered fiber first serves as the saturable absorber in the Yb‐doped fiber laser and the Er‐doped fiber laser, leading to the noise‐like pulses at 1 µm, and the stable Q‐switching, conventional soliton, and dissipative soliton resonance mode‐locking operations at 1.5 µm. This work confirms that the enhanced saturable absorption in HEAs can endow the high‐performance ultrashort pulse generation.

Dynamics of pH at Santa Catalina Island

The local expression of ocean acidification may depend on local oceanographic features in addition to global forcings. Our objective is to provide a baseline of pH behavior at Santa Catalina Island, situated within the unique oceanographic characteristics of the Southern California Bight, and to gain insight into ocean acidification at the island. Measurements of the upper water column (to 30-m depth) of pH, temperature, conductivity, chlorophyll and dissolved oxygen at Santa Catalina were made from a fixed mooring and by profiling the water column from a boat and on Self-Contained Underwater Breathing Apparatus (SCUBA). The average pH (8.095 at 18-m depth) was found to be higher than that reported off the nearby mainland and the Northern Channel Islands. The higher value is thought to result from both downwelling produced by internal waves as well as less upwelling at the island compared to other locations. Large modulations in pH at depth corresponded to advection of gradients by internal waves. Within the accuracy of the sensors there was no seasonal dependence detected at near-surface, nor a pH signal associated with the sub-surface chlorophyll and oxygen maxima. We conclude that marine life living at depths affected by internal waves experience significant variation in pH.

Pedestrian detection algorithm integrating large kernel attention and YOLOV5 lightweight model.

In the context of intelligent driving, pedestrian detection faces challenges related to low accuracy in target recognition and positioning. To address this issue, a pedestrian detection algorithm is proposed that integrates a large kernel attention mechanism with the YOLOV5 lightweight model. The algorithm aims to enhance long-term attention and dependence during image processing by fusing the large kernel attention module with the C3 module. Furthermore, it addresses the lack of long-distance relationship information in channel and spatial feature extraction and representation by introducing the Coordinate Attention mechanism. This mechanism effectively extracts local information and focused location details, thereby improving detection accuracy. To improve the positioning accuracy of obscured targets, the alpha CIOU bounding box regression loss function is employed. It helps mitigate the impact of occlusions and enhances the algorithm's ability to precisely localize pedestrians. To evaluate the effectiveness of trained model, experiments are conducted on the BDD100K pedestrian dataset as well as the Pascal VOC dataset. Experimental results demonstrate that the improved attention fusion YOLOV5 lightweight model achieves an average accuracy of 60.3%. Specifically, the detection accuracy improves by 1.1% compared to the original YOLOV5 algorithm, and the accuracy performance index reaches 73.0%. These findings strongly indicate the proposed algorithm in significantly enhancing the accuracy of pedestrian detection in road scenes.

Thermo-compression Bonding Assembly Technology

With the slowing of Moore’s law heterogeneous integration and assembly became important drivers of the performance of semiconductor packaging. This “More than Moore” approach enables higher functional density and higher bandwidth packages. At the same time, heterogeneous integration drives an aggressive interconnect pitch roadmap, pushing the limits of Advanced Packaging technologies. Flip chip with mass reflow has been the main assembly technology for fine pitch interconnect. However, the need for even finer pitch and higher packaging density was not compatible with the limitations imposed by the mass reflow process, therefore requiring new interconnect technologies. Local reflow flip chip via thermocompression bonding (TCB) overcomes limitations due to CTE-mismatch and warpage. Meanwhile, TCB based on solder micro-bumps became a well-established and cost effective fine-pitch interconnect process and Cu to Cu Hybrid Bonding is emerging as a technology for the future. Normal TCB typically requires the application of flux and post-bond flux cleaning as any flux residue can result in post mold package reliability issues, even for ‘no-clean’ flux materials. Post-bond flux cleaning, however, becomes more and more difficult for increasing die size and with bump pitch and stand-off height shrinking even further. K&S has developed and demonstrated a flux-less TCB process for large and high-density interconnect die that utilizes in-situ Formic Acid (FA) vapor application for copper and solder oxide reduction. This process eliminates the need for flux and, therefore, there is no need for the tedious and time-consuming cleaning of the post bond flux residue. The FA process delivers nearly the same productivity as a conventional flux based TCB process. The FA delivery system can be integrated on our high-accuracy C2S and C2W TCB tools, leveraging the existing HVM TCB infrastructure and extending its application space from ~35µm towards ultra-fine pitch applications around 10µm. Hybrid bonding created a lot of attention over the last years as this bump-less technology allows for long-term pitch scalability, possibly even down to 1µm. Hybrid bonding, however, requires a more complex process flow which relies on pristine die and target wafer surfaces as well as front-end level cleanliness conditions. Accordingly, the advantages and cost of Flux-less TCB as compared to Hybrid bonding should be explored in more detail. TCB can be viewed as an extension of flip chip. Using the existing assembly and metrology infrastructure as well as the existing die and substrate design layouts will be attractive to subcons. As a result, the overall cost and time to market should be much lower. An activity-based cost model has been developed along with SavanSys comparing flux-less TCB and Hybrid bonding. We present results on the process cost as well as the overall package cost as a function of die size and yield. In summary, flux-less thermo-compression bonding should be considered for ultra-fine pitch applications. We have demonstrated pitch capability below 30µm and believe that a pitch of 10µm may be possible. Other applications that formic acid vapor TCB enables are large module bonding (50 X 50 mm, 70 X 70 mm) and Cu to Cu interconnects.

Interdecadal Variations of Radiative Feedbacks Associated With the El Niño and Southern Oscillation (ENSO) in CMIP6 Models

AbstractInternally generated radiative feedback at interannual timescales can influence climate sensitivity estimates. This study has clarified the mechanisms of variability in radiative feedback associated with the El Niño and Southern Oscillation based on preindustrial control simulations for Coupled Model Intercomparison Project Phase 6. Radiative feedback showed large modulation with a comparable magnitude to the intermodel uncertainty associated with internal changes in the zonal gradient of the ocean thermocline and sea surface temperature (SST) in the equatorial Pacific on interdecadal timescales. When the interdecadal SST anomalies in the eastern and western equatorial Pacific were simulated as positive and negative, respectively, the statistical properties of the interannual variations were also modified with diminished Walker circulation changes per unit of global mean surface temperature rise. Meanwhile, the enhanced local Hadley circulation led to a middle‐to upper‐level cloud decrease and a low‐level cloud increase in the subtropics, causing enhanced negative radiative feedback as a global average.

Boosting the Self-Recharging of Polypyrrole/Prussian Blue Electrochromic Device by Potential Difference-Driven Alternative Redox.

Energy-storage electrochromic (EC) devices are a kind of recently developed device integrating energy-saving and energy-storage functions. To minimize energy consumption, a self-rechargeable energy-storage EC device with fast recovery speed is highly desired. Herein, a polypyrrole (PPy)/Prussian blue (PB) double-layer film with a potential difference is initially constructed and fabricated into a fast-recovery self-rechargeable EC device. Due to the existence of potential difference, the reduced PPy can be oxidized by PB, and subsequently Prussian white (the reduced state of PB) can be oxidized by O2 dissolved in electrolyte. Thus, the self-coloration/self-recharging process can be boosted by an alternative redox occurring in the solid/solid/liquid interfaces of PPy/PB/dissolved O2 instead of common solid/liquid interfaces or solutions. After self-recharging for 1 h, 65.0% of the open-circuit voltage and 45.2% of the total capacity can be recovered. Simultaneously, the synergy effect in this PPy and PB system enables a large optical modulation of 63.3% at 800 nm, a high open-circuit voltage of 1.20 V, and a large initial specific capacity of 87.8 mA·h·g-1 at 1.0 A·g-1. The design of double-layer film with a potential difference for boosting the self-coloration/self-recharging process of EC devices provides a new strategy for next-generation self-powered energy-storage EC devices.