Asymmetric Core Research Articles

Asymmetric Modification of Carbazole Based Self-Assembled Monolayers by Hybrid Strategy for Inverted Perovskite Solar Cells.

Carbazole-based self-assembled molecules (SAMs) are widely applied in inverted perovskite solar cells (iPSCs) due to their unique molecular properties. However, the symmetrical structure of the carbazole-based SAMs makes it difficult to finely regulate their performance, which impedes the further enhancement of the efficiency and stability of iPSCs. This work demonstrates that by constructing an asymmetric carbazole core, 9H-thieno[2',3' : 4,5]thieno[3,2-b]indole) (TTID), the key properties of SAM molecules can be effectively regulated. It has been confirmed that the hybrid thieno[2,3-b]thiophene unit of this asymmetric core governs the energy level, the surface wettability, and the defect passivation capability of the SAMs, while the substituent of core has a greater impact on the molecular dipole and device stability. The synergistic effects from thieno[2,3-b]thiophene and fluorine lead to the KF-derived iPSC demonstrating a certified power conversion efficiency (PCE) of 25.17 % and excellent operational stability. This hybrid design concept offers a promising approach for the further structural modification of SAMs in iPSCs.

Asymmetric main-chain twisted small molecules for efficient polymer solar cells

Polymer solar cells (PSCs) based on small molecules with twisted backbones as electron acceptors, have many advantages over their planar counterparts, such as upshifted molecular energy levels, better charge extraction performance, enhanced extinction coefficient, extended carrier lifetime and reduced recombination rate, which are very helpful in improving the power conversion efficiencies (PCE). The present study was designed to synthesize two new small molecules with main-chain twisted structures that include an asymmetric electron donor core thiophene-phenylene-thieno[3,2-b]thiophene, namely i-T-TT and i-T-TT-4F, to investigate the “structure-property” correlation of main-chain twisted acceptors. Both asymmetric molecules exhibit bent geometric structures, and the fluorinated acceptor i-T-TT-4F possesses a more red-shifted spectrum, improved molar extinction coefficient, and deepened molecular energy levels. As a result, when combined with the middle bandgap polymer donor J52, there was a remarkable efficiency of 12.22 % for the device of i-T-TT-4F, higher than that of i-T-TT (9.51 %). Our research illustrates the importance of the main-chain twisted asymmetric electron-donating core and fluorinated end-capping group in the construction of efficient PSCs.

Multiphoton‐And SHG‐Active Pyrimidine‐Based Liquid Crystalline Thin Films Toward 3D Optical Data Storage

AbstractAn original asymmetric achiral pyrimidine core molecule, with long carbon chains on one side and a coumarin fragment on the other, is designed. This advanced molecular structure enabled the spontaneous emergence of crystalline and liquid crystalline thin films with strong 2nd harmonic generation (SHG) without any corona polishing process or tedious deposition techniques. Moreover, pin‐pointed multiphoton absorption in the liquid crystalline phase effectively switches off the SHG signal locally and permanently, underlining its interest in 3D data storage. This prototypical material, which can be fully addressed by NLO processes, multiphoton writing, and SHG reading, paves the way for the development of efficient flexible materials for 3D optical data storage.

New Data for Asymmetric Core Reduction in Western Tian Shan Piedmonts: The Ertash Sai 2 Open-Air Site

ABSTRACT This study describes a multi-proxy approach toward a newly discovered open-air loess site, Ertash Sai 2, located in the western piedmonts of the Tian Shan in Uzbekistan. Technological analyzes enabled the identification of an asymmetric core reduction scheme accompanied by a Levallois-like predetermined knapping scheme, along with the production of truncated-faceted pieces and burin-cores. Moreover, the results show a direct relationship between the presence of truncated-faceted pieces or burin-cores and both core reduction schemes, as long as truncated-faceted pieces were mostly produced from débordant blades and flakes. Chronostratigraphic studies enabled the precise chronology of the assemblage to be determined as 68–57 ka BP. This raises questions about the origins of traits usually associated with the Initial Upper Palaeolithic in Central Asia and their roots in local Levallois-based assemblages.

Role of structural asymmetry on the delivery of all-optical logical binary half adder in an asymmetric triple core photonic crystal fiber

This article explores the influence of structural asymmetry on the delivery of all-optical logical binary half adder function through triple-core photonic crystal fiber. For the proposed aim, the study considers different configurations of symmetric as well as asymmetric triple-core photonic crystal fiber involving optical guiding cores arranged in a planar and triangular fashion. The role of geometrical asymmetry is investigated by considering an asymmetric triple core photonic crystal fiber with a minor variation in one of the guiding core radii. Through the extinction ratio calculations, with suitable input signal combinations and control signal power, the half adder operation is demonstrated via logic outputs. The obtained results show the significant role of geometrical asymmetry indicated by the variation in the extinction ratios for the individual configurations. However, the half adder operation is found to be robust even in the presence of considerable geometrical asymmetry, with a significant figure of merit. Apart from this, a minor shift in the control signal phase is also observed between symmetric and asymmetric configurations for delivering logic gates based on the half adder function.

Low bandgap fused-ring electron acceptors based on π-expended asymmetric benzotrithiophene core: Regulating aggregation and photovoltaic performance by side chain isomerization

Asymmetric molecular design strategy has received increasing attention in the development of fused-ring electron acceptors (FREAs). Benzo [2,1-b: 3,4-b’: 5,6-b”] trithiophene (asym-BTT) with intrinsically asymmetric and electron-rich π-plane is an ideal unit to construct asymmetric FREAs, whereas asym-BTT-based FREAs are still very limited. Herein, two asymmetric FREAs based on the π-expended asym-BTT fused-core with para-hexylphenyl and meta-hexylphenyl side chains (p-FABTT and m-FABTT) have been developed. Owing to strong electron-donating ability and planar configuration of π-expended asym-BTT fused-core, two acceptors exhibit effective intramolecular charge transfer and intermolecular interaction, leading to near infrared absorption above 900 nm with narrow bandgaps of around 1.34 eV. Although the same π-conjugated backbones of two acceptors afford the nearly identical energy levels and solution absorptions, side chain isomerization leads to significant differences in film absorption, molecular stacking orientation and crystallinity. In neat film, the m-FABTT with meta-hexylphenyl side chains exhibits slightly redshifted absorption with stronger 0-0 absorption peak from J-aggregation compared to p-FABTT with para-hexylphenyl side chains. More orderly molecular stacking and stronger π-π interactions with shorter π-π stacking distance in both the neat film and active layer can be observed for m-FABTT. When blended with donor polymer D18, m-FABTT exhibits broadened spectral region and proper phase separation morphology for effective exciton dissociation and charge transport. Therefore, the OSCs device based on m-FABTT achieves an optimal PCE of 7.14 % with a higher JSC of 15.39 mA cm−2 and an improved FF of 57.96 % as comparing with p-FABTT-based device (a PCE of 4.81 % with a JSC of 11.67 mA cm−2 and a FF of 48.51 %).

Optimized Crystal Framework by Asymmetric Core Isomerization in Selenium-Substituted Acceptor for Efficient Binary Organic Solar Cells.

Both the regional isomerization and selenium-substitution of the small molecular acceptors (SMAs) play significant roles in developing efficient organic solar cells (OSCs), while their synergistic effects remain elusive. Herein, we developed three isomeric SMAs (S-CSeF, A-ISeF, and A-OSeF) via subtly manipulating the mono-selenium substituted position (central, inner, or outer) and type of heteroaromatic ring on the central core by synergistic strategies for efficient OSCs, respectively. Crystallography of asymmetric A-OSeF presents a closer intermolecular π-π stacking and more ordered 3-dimensional network packing and efficient charge-hopping pathways. With the successive out-shift of the mono-selenium substituted position, the neat films give a slightly wider band gap and gradually higher crystallinity and electron mobility. The PM1 : A-OSeF afford favourable fibrous phase separation morphology with more ordered molecular packing and efficient charge transportation compared to the other two counterparts. Consequently, the A-OSeF-based devices achieve a champion efficiency of 18.5 %, which represents the record value for the reported selenium-containing SMAs in binary OSCs. Our developed precise molecular engineering of the position and type of selenium-based heteroaromatic ring of SMAs provides a promising synergistic approach to optimizing crystal stacking and boosting top-ranked selenium-containing SMAs-based OSCs.

Optimized Crystal Framework by Asymmetric Core Isomerization in Selenium‐Substituted Acceptor for Efficient Binary Organic Solar Cells

AbstractBoth the regional isomerization and selenium‐substitution of the small molecular acceptors (SMAs) play significant roles in developing efficient organic solar cells (OSCs), while their synergistic effects remain elusive. Herein, we developed three isomeric SMAs (S‐CSeF, A‐ISeF, and A‐OSeF) via subtly manipulating the mono‐selenium substituted position (central, inner, or outer) and type of heteroaromatic ring on the central core by synergistic strategies for efficient OSCs, respectively. Crystallography of asymmetric A‐OSeF presents a closer intermolecular π–π stacking and more ordered 3‐dimensional network packing and efficient charge‐hopping pathways. With the successive out‐shift of the mono‐selenium substituted position, the neat films give a slightly wider band gap and gradually higher crystallinity and electron mobility. The PM1 : A‐OSeF afford favourable fibrous phase separation morphology with more ordered molecular packing and efficient charge transportation compared to the other two counterparts. Consequently, the A‐OSeF‐based devices achieve a champion efficiency of 18.5 %, which represents the record value for the reported selenium‐containing SMAs in binary OSCs. Our developed precise molecular engineering of the position and type of selenium‐based heteroaromatic ring of SMAs provides a promising synergistic approach to optimizing crystal stacking and boosting top‐ranked selenium‐containing SMAs‐based OSCs.

Response of aluminium honeycomb sandwich panels under combined shock and impact loading: Experimental and numerical investigations

The performance of sandwich structures against individual shock loading and fragment impact loading has been extensively examined, but little is known about their performance in the presence of simultaneous shock and impact loading. Based on a recently developed composite projectile to simulate combined shock and single fragment impact loading, the performance of aluminum honeycomb core sandwich panels (HCSPs) against combined loading is methodically examined. The achieved results reveal that the combined loading exhibits a synergistic effect compared to the single loading, i.e., increased damage of the sandwich panel and enhanced perforation resistance of the sandwich panel. After that, a three-dimensional finite element simulation is performed to explore the underlying mechanism of the synergistic effect. Numerical analysis indicates that the increased damage is a result of perforation-induced reduction of load-carrying capacity of sandwich panel, while the enhanced perforation resistance is the result of deflecting-induced perforation time delay of the perforation process. Finally, the parametric investigation of sandwich geometries such as asymmetric face sheets, core density, and core height is comprehensively conducted. The gained results reveal that both performance and synergistic effect due to combined loading are sensitive to these parameters.

A Scalable Matrix Integrated Transformer With Controllable Leakage Inductance for a Bi-Directional Resonant Converter

Integrated transformer with built-in leakage inductors is a good approach for simplifying the whole system, as it integrates discrete leakage inductors into the transformer with printed circuit board (PCB) windings for a single-phase CLLC (1PCLLC) resonant converter. The EI-core-based integrated transformer can integrate adjustable leakage inductance into the transformer. Series or parallel connections of EI-core-based integrated transformers offer a possible solution for high-voltage and high-power applications: however, the penalty of more considerable core loss by the induced leakage flux is problematic. This paper proposes a matrix integrated transformer with controllable leakage inductance for a 1PCLLC resonant converter. Three EI-core-based elemental integrated transformers can be integrated into one three-UI-core-based integrated transformer with built-in leakage inductance, and the benefits of evenly distributed flux inside the core and much-reduced core loss can be achieved. An asymmetrical winding structure and asymmetrical core structure were proposed to adjust the built-in leakage inductance for the proposed matrix integrated transformer. An 11-kW 1PCLLC resonant converter for 800-V onboard-charger application was built to verify the proposed novel matrix integrated transformer. The designed converter can achieve a power density of 250W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density and 98.4% peak efficiency.

Experimentally verified numerical model for asymmetric ferrite core wireless power transfer with on-chip interfacing circuits

This paper presents a novel numerical model for asymmetric ferrite core wireless power transfer, which has been experimentally verified. The research focuses on addressing the challenge of reducing the resonance frequency in wireless power transfer technology, particularly for cost reduction in power transfer systems. To achieve this, a toroidal ferrite core is utilized to decrease the self-resonant frequency, and the transmission parameter is measured using a vector network analyzer. Inductive wireless power transfer designs operating at MHz frequencies often suffer from low current efficiency due to the quality factor of the resonant coils. To overcome this limitation, finite element analysis is employed to optimize the cross-sectional area of the inductors, specifically for high-frequency wireless power transfer. The results demonstrate the effectiveness of the optimized coils, achieving an impressive transfer efficiency of nearly 98% at 5 cm, with an operating frequency of 21.6 MHz. Furthermore, the system is enhanced with a CMOS-based interfacing circuit, designed to enable system-on-chip power transfer for Internet of Things (IoT) applications. This integrated system design contributes to the advancement of wireless power transfer technology by not only addressing resonance frequency reduction but also proposing a cost-effective and efficient solution for power transfer in IoT applications.

Reconstruction of three-dimensional strain field in an asymmetrical curved core–shell hetero-nanowire

Crystal orientation and strain mapping of an individual curved and asymmetrical core–shell hetero-nanowire (NW) is performed based on transmission electron microscopy. It relies on a comprehensive analysis of scanning nanobeam electron diffraction data obtained for 1.3 nm electron probe size. The proposed approach also handles the problem of appearing twinning defects on diffraction patterns and allows for the investigation of materials with high defect densities. Based on the experimental maps and their comparison with finite element simulations, the entire core–shell geometry including full three-dimensional strain distribution within the curved core–shell NW are obtained. Our approach represents, therefore, a low-dose quasi-tomography of the strain field within a nanoobject using only a single zone axis diffraction experiment. Our approach is applicable also for electron beam-sensitive materials for which performing conventional tomography is a difficult task.

An asymmetric slotted structured twin core photonic crystal fiber based highly sensitive surface plasmon resonance refractive index biosensor

A butterfly-shaped core photonic crystal fibers with less asymmetric rectangular and circular air holes are proposed, and their properties are numerically analyzed. The sensor construction is reduced to only seven air holes and uses surface plasmons stimulated inside gold (Au) strips for simplicity in manufacture and high sensitivity. Gold is employed as an effective plasmonic metal throughout this design to create resonant effects and is located away from the proposed structure to make production easier. Maximum amplitude sensitivity for the proposed sensor is 228.89 RIU−1, maximum wavelength sensitivity is 88,000 nm/RIU, and maximum wavelength resolution is 1.14 × 10−6RIU−1 for y-polarized mode where the figure of merit is 65.78 RIU−1 with a linearity of 0.9905. The proposed sensor can detect the RI of unspecified analytes between 1.27 and 1.40, allowing for the analysis of many different types of analytes, such as viruses, cancer cells, sugars, proteins, DNA/RNA and many more.

A Deep Learning Regression Model for Photonic Crystal Fiber Sensor with XAI Feature Selection and Analysis.

A Deep Learning Multi-output regression model is employed to correctly model the relationships between optical design parameters of an asymmetric Twin Elliptical Core Photonic Crystal Fiber (TEC-PCF) and its sensing performances. TEC-PCF acts as a biosensor to detect the blood glucose level taking hemoglobin components into account. Since asymmetric TEC-PCF uses a dual elliptical core, four super modes have to be evaluated to analyze the sensing performance in terms of effective index difference, transmission spectrum, coupling length, and sensor sensitivity. The dataset used in this work is of the optical design parameters of the sensor and Finite Element Method (FEM) results with effective indices of four super modes obtained from the COMSOL Multiphysics by varying hemoglobin concentration to 120 g/L, 140 g/L, and 160 g/L. Gretel.ai's free open-source synthetic data library is used to augment the dataset to make the training more efficient. Explainable AI (XAI) feature analysis using Shapley Additive Explanations (SHAP) framework is used for two purposes: feature selection and to know the feature's effect on prediction. The former led to the development of an optimal model with much fewer computational demands and the latter made the model interpretable. The proposed model can predict the accurate super modes when given input specifications with wavelength ranging from 1.27-1.5 μm and for various glucose concentrations under the influence of hemoglobin much faster compared to the other numerical simulations which are computationally expensive. Computation time taken by the proposed Artificial Neural Network (ANN) model, the proposed model with XAI and FEM is also being compared.

Synthesis of Asymmetrical CsPbBr3/TiO2 Nanocrystals with Enhanced Stability and Photocatalytic Properties

Practical applications of CsPbX3 nanocrystals (NCs) are limited by their poor stability. The formation of a heterojunction between CsPbX3 NCs and oxides is an effective means to protect perovskite from polar solvents and other external factors. Significantly improving the stability and photocatalytic properties of the core/shell perovskite is very important for its application in photoelectric and photocatalytic technology. Here, we report the synthesis of asymmetrical CsPbBr3/TiO2 core–shell heterostructure NCs at the single-particle level by hot-injection liquid-phase synthesis and sol–gel method, where each CsPbBr3 NCs is partially covered by titanium dioxide. We tested not only the optical properties of the material but also the electrochemical impedance and photocurrent density of the material in sodium sulfate solution. It is shown that the type II arrangement is generated at the heterogeneous interface, which greatly facilitates the separation of electron–hole pairs and increases the carrier transport efficiency. Compared with CsPbBr3 NCs, CsPbBr3/TiO2 has higher photocatalytic efficiency. More crucially, due to the protection of the titanium dioxide shell, the product has higher long-term stability in humid air compared with bare CsPbBr3 NCs. The asymmetrical core–shell heterostructure prepared in this study not only improves the stability of CsPbX3 NCs but also provides some ideas for optoelectronic device applications and TiO2-based photocatalysts.

A new non-fullerene acceptor based on an asymmetric electron-deficient core for indoor organic photovoltaic cells

Extending the number of fused aromatic rings in π-conjugated materials has proven to be an effective strategy to tailor the electronic, optical, and structural properties. In this work, the structure of the well-known Y6 was modified and a new asymmetric non-fullerene acceptor BIID was developed for organic photovoltaics. BIID was found to show a slightly blue-shifted absorption spectrum compared with Y6 in solid thin films. A high efficiency of 19.5% was achieved by using an BIID:PM6 bulk heterojunction blend film in a 1 cm2 device under indoor LED light, while an efficiency of 17.6% was achieved from the Y6:PM6 blend under the same conditions. Several characterization techniques were applied to study the structure–property relationships, and it was found that the BIID:PM6 blend has less trap-induced recombination, which led to a much higher open circuit voltage and higher device efficiency. With numerous possibilities for further structural optimization, such as attaching various substituents to the central electron-deficient core, BIID is considered to be a class of promising non-fullerene acceptors for indoor organic photovoltaics.

Soliton Dynamics in a Birefringent Optical Fiber

Long-distance solitons maintain their form and speed. Single mode optical fiber exhibits birefringence as a result of its asymmetric core's effect on the refractive index. The soliton pulse is broadened and chirped as it travels through a birefringent optical fiber due to many features of the fiber. Therefore, it is necessary to strike a balance between the elements influencing the transmission to guarantee minimal data loss. This work uses OptiSysten software to strike a balance between the length, effective area, soliton period, and attenuation effects that affect the performance of the soliton while employing optical fiber as a birefringent optical fiber. Based on this research, a set of values for these parameters that minimizes widening and chirping was determined. The simulation findings are compared to the mathematical and analytical combination of soliton, which is based on the coupled non-linear Schrodinger equation. Although previous works on soliton had demonstrated the impact of GVD and SPM on the transmission, this paper aids comprehension by including additional performance-affecting characteristics.

The Impact of Increasing the Length of the Conical Segment on Cyclone Performance Using Large-Eddy Simulation

In cyclone separators, the asymmetrical coherent structure significantly influences the velocity fluctuations and hence the cyclone performance. This asymmetric rotating vortex in the core region precesses around the cyclone axis with a frequency that depends on the cyclone geometry and operating conditions. In the present work, we studied the impact of increasing the length of the conical segment on the performance of cyclone separators as well as the precessing frequency of the asymmetrical structure. For this, five different cone lengths were considered such that the total cyclone length equalled 3.0D, 3.5D, 4.0D, 4.5D, and 5.0D (here, D is the main body diameter of the cyclone). The study was performed at three different inlet velocities, viz. 10, 15, and 20 m/s. Throughout the work, the angle of the conical segment was held fixed and resembled the reference model (which had a total cyclone length equal to 4.0D). The cyclone performance was evaluated using advanced closure large-eddy simulation with the standard Smagorinsky subgrid-scale model. Conclusive results indicate that with an increase in the cone length, the pressure losses reduce appreciably with small variations in the collection efficiency, followed by a reduction in the precessing frequency of the asymmetric vortex core. The results further indicate that the apex cone angle (or the bottom opening diameter) must be carefully adjusted when increasing the cone length.

Metabolic engineering for the biosynthesis of bis-indolylquinone terrequinone A in Escherichia coli from L-tryptophan and prenol

BackgroundTerrequinone A is a bis-indolylquinone natural product with antitumor activity. Due to its unique asymmetric quinone core structure and multiple functional groups, biosynthesis is more efficient and environmentally friendly than traditional chemical synthesis. Currently, most bis-indolylquinones are obtained by direct extraction from fungi or by chemical synthesis. By focusing on the biosynthesis of terrequinone A, we hope to explore the way to synthesize bis-indolylquinones de novo using Escherichia coli as a cell factory.ResultsIn this study, a terrequinone A synthesis pathway containing the tdiA–tdiE genes was constructed into Escherichia coli and activated by a phosphopantetheinyl transferase gene sfp, enabling the strain to synthesize 1.54 mg/L of terrequinone A. Subsequently, a two-step isopentenol utilization pathway was introduced to enhance the supply of endogenous dimethylallyl diphosphate (DMAPP) in E. coli, increasing the level of terrequinone A to 20.1 mg/L. By adjusting the L-tryptophan (L-Trp)/prenol ratio, the major product could be changed from ochrindole D to terrequinone A, and the content of terrequinone A reached the highest 106.3 mg/L under the optimized culture conditions. Metabolic analysis of L-Trp indicated that the conversion of large amounts of L-Trp to indole was an important factor preventing the further improvement of terrequinone A yield.ConclusionsA comprehensive approach was adopted and terrequinone A was successfully synthesized from low-cost L-Trp and prenol in E. coli. This study provides a metabolic engineering strategy for the efficient synthesis of terrequinone A and other similar bis-indolylquinones with asymmetric quinone cores. In addition, this is the first report on the de novo biosyhthesis of terrequinone A in an engineered strain.

Complex Phase Behavior in Binary Blends of AB Diblock Copolymer and ABC Triblock Terpolymer

Blending block polymers with different block compositions provides an opportunity to create nanostructures that are not accessible from neat block copolymer melts. In this study, we investigate the equilibrium phase behavior in binary blends composed of an AB diblock copolymer and an ABC triblock terpolymer, using self-consistent field theory (SCFT). Blending these simple linear block polymers results in complex phase behaviors, including unusual core–shell network phases with asymmetric core and shell volume fractions and a new cylinder-in-O70 hybrid network phase. The phase diagrams with respect to segregation strength and blend composition reveal an unexpected morphological richness, including 15 ordered phases, illustrating the potential inherent in blending these relatively simple components.