Low Loss Coefficient Research Articles

Dual-crosslinked reduced graphene oxide/polyimide aerogels possessing regulable superelasticity, fatigue resistance, and rigidity for thermal insulation and flame retardant protection in harsh conditions

Polyimide (PI) aerogels have various applications in aerospace, national defense, military industry, and rail transit equipment. This paper reports a series of ultra-lightweight, high elasticity, high strength, low thermal conductivity, and high flame retardant rGO/PI nanocomposite aerogels prepared by the ice templating method. The effects of freezing processes (unidirectional freezing and random freezing), chemical composition, and environmental temperature (−196–200 °C) on the morphology, mechanical, and thermal properties of the aerogels were systematically studied. The results indicated that unidirectional aerogels exhibit anisotropic mechanical properties and thermal performance. Compression in the horizontal direction showed high elasticity, high fatigue resistance, and superior thermal insulation. Meanwhile, in the vertical direction, it demonstrated high strength (PI-G-9 reaching 14 MPa). After 10,000 cycles of compression in the horizontal direction (at 50 % strain), the unidirectional PI-G-5 aerogel still retains 90.32 % height retention, and 78.5 % stress retention, and exhibited a low stable energy loss coefficient (22.11 %). It also possessed a low thermal conductivity (32.8 mW m−1 K−1) and demonstrated good thermal insulation performance by sustaining at 200 °C for 30 min. Interestingly, the elasticity of the aerogels was enhanced with decreasing temperatures, achieving a height recovery rate of up to 100 % when compressed in liquid nitrogen. More importantly, the rGO/PI aerogels could be utilized over a wide temperature range (−196–200 °C) and had a high limiting oxygen index (LOI) ranging from 43.3 to 48.1 %. Therefore, this work may provide a viable approach for designing thermal insulation and flame-retardant protective materials with excellent mechanical properties that are suitable for harsh environments.

Thermal assessment of cylindrical parabolic integrated collector storage using input-output and dynamic system testing procedures: Experimental and numerical study

The main limitation of Integrated Collector Storage systems lies in their low efficiencies and high loss coefficients. In this paper, experimental and numerical setups are conducted to assess the thermal performances of low cost Cylindrical Parabolic Integrated Collector storage (CP-ICS). The conceived system has two aluminum plates in parabolic form serving as reflectors, each with a surface area of 2 m2. The storage tank has a volume of 160 L covered with a layer of black paint with single and double transparent insulations. Results of the experimental tests using Input-Output method showed that the daily thermal efficiency ηd of the developed systems is equal to 48.21% and 49.46% for single and double insulation cover configurations, respectively. The total store heat capacity Cs, the useful collector surface Ac* and the storage tank heat losses coefficient Us of the system found using Dynamic System Testing procedure are equal to 0.56 MJ/K, 0.74 m2 and 1.59 W/K, respectively. Even if the energy efficiency of the system is slightly lower than that recorded in conventional systems, numerical results of long-term study using TRNSYS software showed that the system provides a reasonable solar fraction for the needs of a family in Tunisian climate. A comparative assessment of the developed solar collector performances in different representative climates showed that the use of the CP-ICS system presents a promising solution for countries with annual ambient temperatures fluctuating from 13°C to 33°C, such as Araxos with a solar coverage of 30.65% for a daily supply volume of 160 L. More importantly, in Faya-Largeau location, presenting Chadian climate data, the solar fraction is found to be the highest and reached an average of 67.25%.

Numerical Investigation of Butterfly Valve Performance in Variable Valve Sizes, Positions and Flow Regimes

Reliability and efficiency of valves are necessary for precise control and sufficient heat-flow to heat application plants for the integrated energy systems of nuclear power plants (NPPs). Strategic Management Analysis Requirement and Technology (SMART) valves’ ability to control flow and assess environmental parameters stands out for these requirements. Their ability to sustain the downstream flow rate, prevent reverse flow, and maintain pressure in the heat transport loop is much more efficient with the integration of sensors and intelligent algorithms. For assessing valve performance and monitoring, mechanical design and operating conditions are two important parameters. In this study, the butterfly valves of three different sizes are simulated with water and steam using STAR-CCM+ in various flow regimes and positions to analyze performance parameters to strategize an automated control system for efficiently balancing the heat–transport network. Also, flow behavior is studied using velocity and pressure fields for valve–body geometry optimization. It can be observed, through performance parameters, that the valves are suitable for operation between 30° and 90° positions with significantly low loss coefficients and high flow coefficients, and the performance parameters follow a certain pattern in both water and steam flow in each scenario.

Supercritical foaming of novel poly(ether‐b‐amide) elastomer and compression property characterization

AbstractLightweight foam made of poly(ether‐b‐amide) (PEBA) elastomer has been widely used in sport shoes due to its superior rebounding and supporting properties. Novel PEBA with polyamide 1012 as hard segments and poly(tetramethylene oxide) (PTMO) as soft segments was foamed by supercritical CO2. The influence of foaming process parameters, that is saturation temperature, pressure on the morphology of cellular structure was systematically studied by scanning electron microscopy (SEM) and wide‐angle x‐ray diffraction (WAXD). By controlling the viscoelastic behavior of PEBA at certain temperatures and pressures, foams with low density and energy loss coefficient can be fabricated. The cell density of 4.5 × 109 cells/cm3 and expansion ratio of 16.0 of the foams can be obtained respectively. Cyclic compression performance of foams was systematically studied. For the foams with the highest expansion ratio, the energy loss coefficient of 11.9% in the first cycle and 3.5% after equilibrium were observed, which were less than those of former reported PEBA foams. The relationship between the Young's modulus and expansion ratio is in line with the Gibson–Ashby relationship.

Controllable and Low-Loss Electrochemiluminescence Waveguide Supported by a Micropipette Electrode.

One-dimensional molecular crystal waveguide (MCW) can transmit self-generated electrochemiluminescence (ECL), but heavy optical loss occurs because of the small difference in the refractive index between the crystal and its surroundings. Herein, we report a micropipette electrode-supported MCW (MPE/MCW) for precisely controlling the far-field transmission of ECL in air with a low optical loss. ECL is generated from one terminal of the MCW positioned inside the MPE, which is transmitted along the MCW to the other terminal in air. In comparison with conventional waveguides on solid substrates or in solutions, the MPE/MCW is propitious to the total internal reflection of light at the MCW/air interface, thus confining the ECL efficiently in MCW and improving the waveguide performance with an extremely low-loss coefficient of 4.49 × 10-3 dB μm-1. Moreover, by regulation of the gas atmosphere, active and passive waveguides can be resolved simultaneously inside MPE and in air. This MPE/MCW offers a unique advantage of spatially controlling and separating ECL signal readout from its generation, thus holding great promise in biosensing without or with less electrical/chemical disturbance.

Low‐k dielectric materials derived from ZSM‐5 zeolite

AbstractLow‐k dielectric materials were prepared by sintering ZSM‐5 zeolite powder compacts at temperatures ranged 1200–1300°C, and the microwave dielectric characteristics were investigated together with the structure evolution during sintering. It was failed to obtain ZSM‐5 ceramics by high temperature sintering because the densification could never occur below the tolerable temperature and the ordered porous structure completely collapsed above the tolerable temperature. The structure changed from ZSM‐5 zeolite to SiO2‐Al2O3 glass at 1240°C, and finally to SiO2‐based cristobalite ceramics above 1275°C. A low dielectric constant (2.63‐2.78) combined with low dielectric loss (< 0.0005 at 18 GHz) and small temperature coefficient of resonant frequency (varied from ‐18.6 to ‐8.1 ppm/°C) was achieved in the present materials, and the value of dielectric loss was the lowest one achieved so far in the dielectric materials with a dielectric constant lower than 3. With the structure evolution from ZSM‐5 zeolite to SiO2‐Al2O3 glass and finally to SiO2‐based cristobalite ceramics, the dielectric constant increased from 2.27 to 2.78, while the Qf value indicated a complicated variation tendency, and the higher Qf values were achieved in the amorphous and crystalline states, while significant drop was determined in the partial amorphous state. It should be a great challenge to prepare dense zeolite ceramics without collapse of ordered porous structure, and then the ultra‐low dielectric constant materials with high Q could be expected.

Superelastic, soft, stress-healable, recyclable conductive materials

We report the design of materials with a unique combination of self-healing ability, electrical conductivity (8–150 Ohm·m), softness (G = 1 MPa), extremely low loss coefficient (tan δ ≈ 0.04) even at large deformations and linearity of resistivity dependence on strain in a broad range. The conductive material can bounce with very low energy dissipation at fast deformation, and it flows and self-heals at a large time scale and when sufficient stress is applied. The key to such properties is a combination of very stable interpenetrated networks formed by multiwalled carbon-nanotubes (MWCNT) filler and by viscoelastic polyborosiloxane (PBS) polymer matrix rendering relaxation processes and self-healing ability. We demonstrated the promise of the developed materials for the design of strain sensors with a very large linear regime and rubber-substitute as a protective coating or a sealing agent material.

Light‐up the white light emission in microscale with a superior deep‐blue AIE fiber as wave‐guiding source

AbstractThe development of high‐performance organic blue light‐emitting emitters is in urgent to act as an excitation source to contribute the white light generation. On the other hand, the investigation on optical waveguides have been received increasing attentions because they can manipulate the light propagation accurately in the microscale to boost the optoelectronic and energy conversion applications. In this work, we facilely prepared a deep‐blue aggregation‐induced emission (AIE) dye, namely TPP‐4OMe, which shows high luminescent efficiency, narrow emission band and good stability in the aggregate state. TPP‐4OMe can be fabricated as deep‐blue AIE microfibers readily with definite morphology and composition. Based on the AIE microfibers, the active waveguide to transmit deep‐blue emission signals can be achieved with a very low optical loss coefficient (α) of 6.7 × 10−3 dB μm−1. Meanwhile, the full‐visible broadband low‐loss passive waveguide can be well performed with these AIE microfibers, which has never been observed in the pure organic crystals. More interestingly, the excellent properties of AIE microfibers enable them to act as a wave‐guiding excitation source, resulting in a distinct and pure white light emission. The present work not only provides excellent blue light‐emitting materials but also bridges the waveguide to realize the efficient white light emission to accelerate the practical applications.

Terahertz magneto-optical metadevice for active spin-selective beam steering and energy distribution with nonreciprocal isolation

Active beam steering and energy distribution have important applications for terahertz (THz) communication, radar, and imaging. However, the spin-conjugated mirror symmetry of a passive Pancharatnam–Berry (PB) metasurface limits the active energy distribution. Here, we prepared a low dispersion, low loss, and high magneto-optical coefficient La:YIG single crystal, ±45∘ Faraday rotation angle that can be actively tuned by a weak magnetic field in broadband THz range at room temperature. Based on this functional material, a THz magneto-optical (MO) spin-modulated metadevice has been demonstrated, which is integrated with a La:YIG, an anisotropic metasurface, and a PB metasurface layer. The spin-conjugated mirror symmetry is broken by the MO chirality effect and photonic spin Hall effect in this metadevice so that spin-selective beam steering within the range of ±27∘−±41∘ is dynamically manipulated by external magnetic fields and power distribution can be tuned with the max modulation depth of 91.6%. More importantly, the MO crystal introduces nonreciprocal phase shift between two spin states so that the device not only achieves active THz beam steering but also provides isolation for reflected waves with the max isolation of 23 dB. This mechanism of THz nonreciprocal spin beam steering provides multiple functions for THz point-to-point networking communication, anti-shielding, anti-interference, and power distribution.

Study on N application and N reduction potential of farmland in China.

The frequent occurrence of extreme weather in recent years poses a significant threat to food production. Ensuring food production and rationalizing the use of agricultural resources require addressing the problem of the improper application of chemical fertilizers. Several effective measures have been implemented in China to reduce agricultural non-point source pollution. Among them, the reduction of excessive nitrogen fertilizer application proves to be the most effective approach in controlling surface pollution from cultivation. Currently, it is crucial to clarify and quantify crop nutrient fertilizer requirements while evaluating the potential for reducing nitrogen fertilizer usage in China. Nitrogen requirements for major crops grown in China were assessed based on the theory of crop nutrient balance, assuming constant grain production as a guarantee. In this paper, we analyze the potential for nitrogen reduction through short-term, medium-term, and long-term scenario predictions. The results show that in the next 3 years, China has a reduction potential of 34.98%, but this potential is not sustainable. Over the next 10 years, there is a reduction potential of 15.04%, with most provinces experiencing a balanced state of soil nitrogen cycling. Hainan, Beijing, Shaanxi, and Fujian have higher reduction potential, with possible reductions of 69.95%, 64.14%, 60.72%, and 54.10%, respectively. However, there are still provinces in China where nitrogen fertilizer is insufficient, leading to soil nitrogen consumption. Specifically, Heilongjiang, Jiangxi, and Shandong Provinces need to increase their nitrogen fertilizer applications by 87.00%, 35.97%, and 8.31%, respectively. The long-term scenario analysis over the next 30 years shows a reduction potential of 40.96%. Among the regions analyzed, Hainan, Beijing, Shaanxi, Fujian, and Ningxia have higher nitrogen fertilizer reduction potentials, with values of 78.97%, 78.48%, 74.25%, 67.87%, and 67.72%, respectively. However, Heilongjiang Province still needs to increase nitrogen fertilizer application by 44.20% to address soil nitrogen depletion. Conversely, Tibet and Qinghai, with high organic fertilizer yields, lower chemical fertilizer usage, and low nitrogen loss coefficients, are well-suited for organic agriculture development. For areas with high organic fertilizers usage and a risk of fertilizer loss, we recommend implementing the organic-inorganic mixed fertilization planting mode.

Impermeable Graphene Skin Increases the Heating Efficiency and Stability of an MXene Heating Element.

A Joule heater made of emerging 2D nanosheets, i.e., MXene, has the advantage of low-voltage operation with stable heat generation owing to its highly conductive and uniformly layered structure. However, the self-heated MXene sheets easily get oxidized in warm and moist environments, which limits their intrinsic heating efficiencies. Herein, an ultrathin graphene skin is introduced as a surface-regulative coating on MXene to enhance its oxidative stability and Joule heating efficiency. The skin layer is deposited on MXene using a scalable solution-phased layer-by-layer assembly process without deteriorating the excellent electrical conductivity of the MXene. The graphene skin comprises narrow and hydrophobic channels, which results in ≈70 times higher water impermeability of the hybrid film of graphene and MXene (GMX) than that of the pristine MXene. A complementary electrochemical analysis confirms that the graphene skin facilitates longer-lasting protection than conventional polymer coatings owing to its tortuous pathways. In addition, the sp2 planar carbon surface with a low heat loss coefficient improves the heating efficiency of the GMX, indicating that this strategy is promising for developing adaptive heating materials with a tractable voltage range and high Joule heating efficiency.

High-temperature resistant, super elastic aerogel sheet prepared based on in-situ supercritical separation method for thermal runaway prohibition of lithium-ion batteries

Thermal runaway (TR) propagation is considered the utmost safety issue of lithium-ion batteries (LIBs), which raised extensive concern. Using high-efficiency fireproof sheets to separate battery packs is one of the effective technologies to reduce the risk of TR propagation. Hence, we report a novel method, namely in-situ supercritical separation (ISS), to fabricate co-precursor aerogel sheets (CAS) based on an in-house device. ISS method can effectively reduce the preparation time of aerogel sheets to 3 h and greatly reduce the amount of solvent used without replacing or pressurizing additional solvent. More importantly, the proposed ISS method can effectively suppress the separation of the co-precursor heterogeneous substances, achieving homogeneous polymerization and improving the mechanical properties, high-temperature resistance and thermal insulation properties of the aerogel sheet. Specifically, CAS exhibits a compression strength of 638.5 kPa (50% strain), a low energy loss coefficient (0.238), and superior fatigue resistance (10,000 compressions). CAS has an ultralow thermal conductivity (i.e., 0.0197 W/(m·K)). The blocking functions of CAS are verified by a series of experiments where TR is triggered by abusive heating. Consequently, the TR propagation among fully charged LIBs with the highest temperature of up to 836.2 °C is successfully suppressed by 2-mm-thick CAS, yielding the maximum cell-to-cell temperature gap of 767 °C. Furthermore, it is proved that CAS with 35.7% wt aerogel is economical and capable of suppressing the TR propagation in the LIB module. The above results indicate that the CAS prepared by the ISS method is promising in applying to a safer LIB module.

Highly resilient and fatigue-resistant poly(4-methyl-ε-caprolactone) porous scaffold fabricated via thiol-yne photo-crosslinking/salt-templating for soft tissue regeneration

Elastomeric scaffolds, individually customized to mimic the structural and mechanical properties of natural tissues have been used for tissue regeneration. In this regard, polyester elastic scaffolds with tunable mechanical properties and exceptional biological properties have been reported to provide mechanical support and structural integrity for tissue repair. Herein, poly(4-methyl-ε-caprolactone) (PMCL) was first double-terminated by alkynylation (PMCL-DY) as a liquid precursor at room temperature. Subsequently, three-dimensional porous scaffolds with custom shapes were fabricated from PMCL-DY via thiol-yne photocrosslinking using a practical salt template method. By manipulating the Mn of the precursor, the modulus of compression of the scaffold was easily adjusted. As evidenced by the complete recovery from 90% compression, the rapid recovery rate of >500 mm min−1, the extremely low energy loss coefficient of <0.1, and the superior fatigue resistance, the PMCL20-DY porous scaffold was confirmed to harbor excellent elastic properties. In addition, the high resilience of the scaffold was confirmed to endow it with a minimally invasive application potential. In vitro testing revealed that the 3D porous scaffold was biocompatible with rat bone marrow stromal cells (BMSCs), inducing BMSCs to differentiate into chondrogenic cells. In addition, the elastic porous scaffold demonstrated good regenerative efficiency in a 12-week rabbit cartilage defect model. Thus, the novel polyester scaffold with adaptable mechanical properties may have extensive applications in soft tissue regeneration.

A Broadband Optical Fiber Coupler Based on Dual-Hollow Core Fiber

Hollow fiber has become a research hotspot in the field of special fibers for its excellent characteristics, such as low loss, low delay, low dispersion, and low nonlinear coefficient. Due to the lack of fiber coupler matching hollow core fiber, the application development of hollow core fiber in the all-fiber integrated system is greatly hindered. Dual-core fiber is widely used in the development of fiber couplers because it can choose optical power, wavelength, and polarization state by the coupling between the two cores. For the urgent need for hollow core fiber coupler, the design and research of wideband fiber coupler based on dual-hollow core fiber are carried out in this paper. Based on the coupled mode theory, the theoretical correlation between the structural parameters and the coupling length in the dual-hollow core anti-resonant fiber was analyzed by using the COMSOL simulation software system. On this basis, a 50:50 wideband fiber coupler was designed by adjusting the structural parameters to reduce the coupling length and introducing the sleeve into the cladding pipe to reduce the loss. The bandwidth of the coupler is up to 150 nm and the transmission loss is on the order of 10−2 dB/m.

Effect of co-doping Nb2O5 with equal amount of Eu2O3 or In2O3 on the electrical properties of TiO2-based varistors

In this work, TiO2 varistors with enhanced nonlinear coefficient, low breakdown voltage, high relative dielectric constant and low dielectric loss were fabricated by co-doping of Nb2O5 with equal amount of Eu2O3 or In2O3. The results indicated an appropriate proportion of dopant could improve the comprehensive performance of the varistors. For the TiO2–Nb2O5–Eu2O3 system, the breakdown voltage and relative dielectric constant of the samples decreased first and then increased, while the nonlinear coefficient increased first and then decreased with the increase of doping content, the best value appears at the doping content of 1.00 mol% (E1mA = 2.14 V/mm, α = 4.6, εr = 2.72 × 105, tanδ = 0.25). It is noted that the secondary phase formed on the grain boundary as Eu2Ti2O7, thus the growth of grain was hindered and the dielectric performances deteriorated. By contrast, for the TiO2–Nb2O5–In2O3 system, the secondary phase was not found. As a result, a low breakdown voltage, low dielectric loss and high nonlinear coefficient were obtained, reaching the best at the doping content of 5.0 mol% (E1mA = 4.6 V/mm, α = 8.4, εr = 1.85 × 105, tanδ = 0.16). The influence of this doping system on the electrical performance can be explained by Internal Barrier Layer Capacitance theory (IBLC), which is related to the potential barrier at the grain boundary.

Optimizing Thermomechanical Processing of Bimetallic Laminates.

Thermomechanical processing combining plastic deformation and heat treatment is a favorable way to enhance the performance and lifetime of bimetallic laminates, especially those consisting of metals, which tend to form intermetallic layers on the interfaces when produced using methods involving increased temperatures. The presented work focuses on optimizing the conditions of thermomechanical treatment for an Al + Cu bimetallic laminate of innovative design involving a shear-strain-based deformation procedure (rotary swaging) and post-process heat treatment in order to acquire microstructures providing advantageous characteristics during the transfer of direct and alternate electric currents. The specific electric resistivity, as well as microhardness, was particularly affected by the structural features, e.g., grain size, the types of grain boundaries, and grain orientations, which were closely related to the applied thermomechanical procedure. The microhardness increased considerably after swaging (up to 116 HV02 for the Cu components), but it decreased after the subsequent heat treatment at 350 °C. Nevertheless, the heat-treated laminates still featured increased mechanical properties. The measured electric characteristics for DC transfer were the most favorable for the heat-treated 15 mm bimetallic laminate featuring the lowest measured specific electric resistivity of 22.70 × 10-9 Ωm, while the 10 mm bimetallic laminates exhibited advantageous behavior during AC transfer due to a very low power loss coefficient of 1.001.

Molecular and Aggregate Synergistic Engineering of Aggregation-Induced Emission Luminogens to Manipulate Optical/Electronic Properties for Efficient and Diversified Functions.

The optical/electronic properties of organic luminescent materials can be regulated by molecular structure modification, which not only requires sophisticated and time-consuming synthesis but also is unable to accurately afford the optical properties of materials in the aggregate state. Herein, a facile strategy of molecular and aggregate synergistic engineering is proposed to manipulate the optical/electronic properties of a luminogen, ACIK, in the solid state for efficient and diversified functions. ACIK is facilely synthesized and exhibits three polymorphic states (ACIK-Y, ACIK-R, and ACIK-N) with a large emission difference of 102 nm from yellow to near-infrared (NIR). Their structure-property relationships were investigated by crystallographic analyses and computational studies. ACIK-Y, with the most twisted structure, exhibits an intriguing color-tuned fluorescence between yellow and NIR in the solid state in response to multiple stimuli. Shuttle-like ACIK-R microcrystals exhibit an optical waveguide property with a low optical loss coefficient of 19 dB mm-1. ACIK dots display bright NIR-I emission, large Stokes shift, and strong NIR-II two-photon absorption. ACIK dots show specific lipid droplets-targeting capability and can be successfully applied for two-photon fluorescence imaging of mouse brain vasculature with deep penetration and high spatial resolution. This study will inspire more insights in developing advanced optical/electronic materials based on a single chromophore for practical applications.

Fabrication of low-loss III-V Bragg-reflection waveguides for parametric down-conversion

Entangled photon pairs are an important resource for many types of quantum protocols. Semiconductor Bragg-reflection waveguides are a promising photon-pair source due to mature fabrication, integrability, large transparency window in the telecom wavelength range, integration capabilities for electro-optical devices as well as a high second-order nonlinear coefficient. To increase performance, we improved the fabrication of Bragg-reflection waveguides by employing fixed-beam-moving-stage optical lithography, low-pressure, and low chlorine concentration etching, and resist reflow. The reduction in sidewall roughness yields a low optical loss coefficient for telecom wavelength light of αreflow = 0.08 (6) mm−1. Owing to the decreased losses, we achieved a photon-pair production rate of 8800 (300) (mW · s · mm)−1, which is 15-fold higher than in previous samples.

Stoichiometric and Chiral Stacking Tailoring of Dibenzocarbazole Analog–TCNB Charge‐Transfer Cocrystals via Supramolecular Assembly for Variable Optical Behaviors

AbstractIn this paper, three new donor–acceptor complex forms (zBC) containing a helical‐shape dibenzocarbazole analog (DBCz) as the electron donor and 1,2,4,5‐tetracyanobenzene (TCNB) as the electron acceptor via a simple solution‐processing strategy are reported. The beginning components self‐assembled into supramolecular frameworks with glamorous alignment modes and different molar ratios: ≈1:1 P or M‐enantiomer for α‐cocrystal, alternated P/M‐column stacking in mesmeric 2:3 β‐cocrystal, and segregated stacking of γ‐cocrystal. As a result, α‐cocrystal exhibits bright solid‐state red fluorescent, β‐cocrystal shows significant optical waveguide behavior with a low optical loss coefficient of ≈0.018 dB µm−1, and no visual light emission is observed for γ‐cocrystal under ultraviolet radiation. Interestingly, the α‐zBC crystal is not only emissive but also chiroptically active with dissymmetry factor (glum) of 0.004. This study on chiral stacking tailoring paves a way for functional design of organic charge‐transfer complex toward application in high‐performance organic optoelectronics.

Large Cation Engineering in Organic Antimony Halides for Low‐Loss Active Waveguide

AbstractActive waveguides have attracted growing attention as a basic component of miniaturized and integrated photonic devices. However, most optical waveguide materials suffer from severe self‐absorption, which greatly increases the optical loss. Therefore, developing highly efficient red‐emitting materials with large Stokes shift and negligible self‐absorption is of great interest. Herein, this work proposes a strategy to achieve both large Stokes shifts and high photoluminescence quantum yield (PLQY) in organic metal halide via large cation engineering. Two zero‐dimensional antimony(III) chlorides, (TMA)2SbCl5 and (TMAA)2SbCl5, are designed and synthesized by screening the ligands with different cationic volumes. Experimental and theoretical results reveal that the large cation can promote the self‐trapped excitons emission and improve stability. Benefiting from the large Stokes shift (291 nm) and high PLQY (98.3%), the as‐prepared (TMAA)2SbCl5 microplate exhibits efficient active waveguide with low loss coefficient of 6.07 × 10−3 dB µm−1. This work not only develops a novel active waveguide material, but also provides insights into the role of organic cation, which will provide new inspiration for the exploitation of excellent luminescent metal halides and photonic devices.