Stable Junctions Research Articles

Rationally designed universal passivator for high-performance single-junction and tandem perovskite solar cells

Interfacial trap-assisted nonradiative recombination hampers the development of metal halide perovskite solar cells (PSCs). Herein, we report a rationally designed universal passivator to realize highly efficient and stable single junction and tandem PSCs. Multiple defects are simultaneously passivated by the synergistic effect of anion and cation. Moreover, the defect healing effect is precisely modulated by carefully controlling the number of hydrogen atoms on cations and steric hindrance. Due to minimized interfacial energy loss, L-valine benzyl ester p-toluenesulfonate (VBETS) modified inverted PSCs deliver a power conversion efficiency (PCE) of 26.28% using vacuum flash processing technology. Moreover, by suppressing carrier recombination, the large-area modules with an aperture area of 32.144 cm2 and perovskite/Si tandem solar cells coupled with VBETS passivation deliver a PCE of 21.00% and 30.98%, respectively. This work highlights the critical role of the number of hydrogen atoms and steric hindrance in designing molecular modulators to advance the PCE and stability of PSCs.

Enhancing kesterite-based thin-film solar cells: A dual-strategy approach utilizing SnS back surface field and eco-friendly ZnSe electron transport layer

The development of kesterite-based thin-film solar cells (TFSCs) has faced significant challenges, particularly due to unstable rear contact properties and low power conversion efficiency (PCE). Despite various individual approaches aimed at addressing these issues, progress has remained limited. In this study, a dual strategy is explored to address these problems simultaneously. First, the impact of an SnS intermediate layer at the back surface field in conjunction with an FTO back contact is examined. Second, the introduction of a stable PN Mott-Schottky junction is assessed by utilizing an eco-friendly ZnSe electron transport layer (ETL) as a replacement for the conventional, yet toxic, CdS ETL. The combined application of these strategies produces a synergistic effect, leading to significant improvements in the solar cell’s microstructure and key electrical parameters, including open-circuit voltage (VOC), short-circuit current density (JSC), and overall PCE. Additionally, this approach mitigates band-tailing states and reduces deep-level defects often associated with the annealing process. As a result, the power conversion efficiency is significantly enhanced, rising from 1.31 ± 0.13 % to 7.68 ± 0.98 %. This effective dual-strategy offers new insights into overcoming the challenges of unstable rear contact properties and suboptimal device parameters, paving the way for further advancements in the performance of kesterite-based TFSCs.

Single-Molecule Conductance of Neutral Closed-Shell and Open-Shell Diradical Indenofluorenes.

Organic diradicals are highly promising candidates as future components in molecular electronic and spintronic devices because of their low spin-orbit coupling. To advance toward final circuit realizations, a thorough knowledge of the behavior of diradicals within a single-molecule junction framework is imperative. In this work, we have measured for the first time the single-molecule conductance of a neutral open-shell diradical compound, a [2,1-b] isomer of indenofluorene (IF). Our results reveal that the conductance of the [2,1-b] isomer is about 1 order of magnitude higher than that of the corresponding closed-shell regioisomer [1,2-b] IF. This is significant, as it fundamentally demonstrates the possibility of forming stable single-molecule junctions using neutral diradical compounds which are also highly conducting. This opens up a new approach to the development of externally addressable spintronic devices operable at room temperature.

The Introduction of a BaTiO3 Polarized Coating as an Interface Modification Strategy for Zinc-Ion Batteries: A Theoretical Study.

Aqueous zinc-ion batteries (AZIBs) have become a promising and cost-effective alternative to lithium-ion batteries due to their low cost, high energy, and high safety. However, dendrite growth, hydrogen evolution reactions (HERs), and corrosion significantly restrict the performance and scalability of AZIBs. We propose the introduction of a BaTiO3 (BTO) piezoelectric polarized coating as an interface modification strategy for ZIBs. The low surface energy of the BTO (110) crystal plane ensures its thermodynamic preference during crystal growth in experimental processes and exhibits very low reactivity toward oxidation and corrosion. Calculations of interlayer coupling mechanisms reveal a stable junction between BTO (110) and Zn (002), ensuring system stability. Furthermore, the BTO (110) coating also effectively inhibits HERs. Diffusion kinetics studies of Zn ions demonstrate that BTO effectively suppresses the dendrite growth of Zn due to its piezoelectric effect, ensuring uniform zinc deposition. Our work proposes the introduction of a piezoelectric material coating into AZIBs for interface modification, which provides an important theoretical perspective for the mechanism of inhibiting dendrite growth and side reactions in AZIBs.

Magnetic injection of α-CP nanoribbons and investigation of spintronic device applications of magnetic α-CP nanoribbons based on first principles calculations

Since the successful synthesis of α-phosphorus carbide (α-CP) using carbon doping technology, α-CP has exhibited excellent carrier mobility and anisotropy at room temperature, underscoring its potential for spintronic applications. The application of CP in spintronic devices is limited due to its lack of magnetism. Effective magnetic injection in non-magnetic semiconductors can typically be achieved by doping with magnetic atoms. In this study, we calculated the electromagnetic properties of transition metal (TM) atoms adsorbed at different positions on α-CP using first principles. Notably, we found that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metallicity. We discovered that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metal properties and design magnetic tunnel junctions with half-metallic Fe_H12 and Mn_H12 adsorption structures. The results show that Mn_H12 and Fe_H12 devices exhibit a highly efficient spin filtering effect, with a TMR as high as 5521%. These findings provide theoretical guidance for the application of CP-based spintronic devices.

Electrically driven cavity plasmons in Au nanowire over Au film

Light emission via inelastic tunneling electrons is appealing for integrated optoelectronic devices due to its femtosecond time scale that can in principle allow terahertz modulation bandwidth. It has gained renewed interest since 2015 due to the improved quantum efficiency, highly tunable emission wavelength, linewidth, or directionality once the electrodes are designed as a plasmonic nanocavity. However, efficient construction of stable tunnel junctions with desired plasmonic resonances is still technically challenging because of the subnanometer precision required in the electrical and optical design. Here, we demonstrate an easily accessible electrically driven cavity plasmon in metal-insulator-metal (MIM) tunnel junctions, comprised by a Au nanowire (NW) across two separate ultrasmooth Au electrodes. Two layers of self-assembled thiol molecule defines a reliable tunneling barrier. The contribution from the localized cavity plasmons to the total light emission is found to be dominant over that from the propagating surface plasmon polariton in the MIM waveguide, different from the traditional explanations. This work introduces a simplified method for constructing electrically driven cavity plasmons using crystalline metals, which holds promise for applications in in situ chemical or biosensing and the development of flexible light-emitting metasurfaces.

Enhanced CO2 photoreduction by constructing BiOCl/NiS Schottky heterojunction with a giant internal electric field

Constructing Schottky junctions is a potent strategy for enhancing charge separation and charge dynamics, essential for optimizing the kinetics of efficient CO2 photoreduction reactions (CO2 RR). Yet, developing highly efficient Schottky heterojunction photocatalyst continues to be a formidable challenge. Here, we utilize two-step hydrothermal technology to prepare a BiOCl/NiS Schottky heterojunction with a powerful internal electric field (IEF) to accelerate the photo-conversion of CO2 to CO. Experimental results show that the charge separation efficiency and IEF strength of the BiOCl/NiS composite photocatalyst are 1.26 and 5.63 times those of BiOCl, respectively. In addition, the BiOCl/NiS composite sample has excellent light absorption ability. Under Uv–vis light irradiation, the BiOCl/NiS sample exhibits superior CO2 to CO photoreduction activity without any sacrificial agents, and a CO yield reaching 7.97 μmol⋅g−1⋅h−1, which is 2.97 times higher than that of BiOCl (2.68 μmol⋅g−1⋅h−1). This work provides a viable solution for designing efficient and stable Schottky junction composite materials.

Electromigrated Gold Nanogap Tunnel Junction Arrays: Fabrication and Electrical Behavior in Liquid and Gaseous Media.

Tunnel junctions have been suggested as high-throughput electronic single molecule sensors in liquids with several seminal experiments conducted using break junctions with reconfigurable gaps. For practical single molecule sensing applications, arrays of on-chip integrated fixed-gap tunnel junctions that can be built into compact systems are preferable. Fabricating nanogaps by electromigration is one of the most promising approaches to realize on-chip integrated tunnel junction sensors. However, the electrical behavior of fixed-gap tunnel junctions immersed in liquid media has not been systematically studied to date, and the formation of electromigrated nanogap tunnel junctions in liquid media has not yet been demonstrated. In this work, we perform a comparative study of the formation and electrical behavior of arrays of gold nanogap tunnel junctions made by feedback-controlled electromigration immersed in various liquid and gaseous media (deionized water, mesitylene, ethanol, nitrogen, and air). We demonstrate that tunnel junctions can be obtained from microfabricated gold nanoconstrictions inside liquid media. Electromigration of junctions in air produces the highest yield (61-67%), electromigration in deionized water and mesitylene results in a lower yield than in air (44-48%), whereas electromigration in ethanol fails to produce viable tunnel junctions due to interfering electrochemical processes. We map out the stability of the conductance characteristics of the resulting tunnel junctions and identify medium-specific operational conditions that have an impact on the yield of forming stable junctions. Furthermore, we highlight the unique challenges associated with working with arrays of large numbers of tunnel junctions in batches. Our findings will inform future efforts to build single molecule sensors using on-chip integrated tunnel junctions.

Insights into the PMS activation towards phenol removal mechanism by a Ti3C2-MXene doped BiVO4 photocatalyst

In the field of water treatment, photocatalysis and the peroxomonosulfate (PMS) deep oxidation process have emerged as potential solutions for the degradation of refractory organic pollutants. In this study, a novel BiVO4/Ti3C2 composite photocatalytic material was successfully synthesized using a hydrothermal method. The energy band structure of this material was utilized to establish Schottky barriers, enhancing the separation of photogenerated carriers. This, in turn, facilitated the activation of PMS under visible light, generating reactive species that effectively degraded phenol. The results demonstrate that in the BT-3/PMS system, the degradation rate of phenol reached 87.2 % within 60 min, with a maximum degradation rate constant of 0.02537 min−1. This represents an 8.8-fold improvement compared to pure BiVO4 and a 5.2-fold improvement compared to pure PMS. Free radical tests indicated that SO4·- was the primary reactive species involved in the degradation process. This study offers a promising approach for the design of efficient and stable Schottky junction photocatalysts that can be activated by visible light and PMS to effectively degrade organic pollutants.

Abstract 5402: Understanding the role of exercise in lymphatic vessel regulation in melanoma

Abstract Exercise has been demonstrated to be an effective method to remodel tumor blood vessels and to improve immune cell infiltration in multiple tumor models in mice. However, it is unclear whether aerobic exercise alters lymphatic vasculature in tumors. The lymphatic system plays an important role in tumor growth and metastasis because it regulates interstitial fluid pressure via lymph flow and immune cell trafficking, in conjunction with blood vessels. Lymphatic vessels are particularly important during metastasis because tumor cells frequently escape the primary tumor through lymphatic vasculature to establish the first site of metastasis in the lymph nodes. Here, we evaluated the effect of aerobic exercise on lymphatic vessels and lymphatic endothelial cell junctions in melanoma in male C57BL/6J mice. BP melanoma cells derived from transgenic mice with BrafV600E/+ and Pten−/− mutations were injected subcutaneously. Mice were assigned to no exercise and exercise groups when tumors reached ~30 mm3. The exercise group completed treadmill running at 12 meters/minute for 45 minutes for 5 consecutive days with 2 days of rest per week for 2 weeks before tumor harvest. Tumor lymphatic endothelial cells were identified by LYVE-1, endothelial tight junctions by ZO-1, and nuclei were identified by DAPI using immunofluorescence staining on frozen tumors. The number of total lymphatic vessels, elongated vessels( >100 µm), open lumens, and co-localization of ZO-1 with LYVE-1 was quantified on 6 random images per tumor using NIH Image J software. ANOVA and t-test were used to conduct statistical analysis (p < 0.05). Tumors from exercised mice had higher lymphatic vessel density (p=0.002) and more open lumens (p=0.001). Surprisingly, tumors from exercised mice had fewer ZO-1 positive vessels (p=0.015) and lower co-localization of ZO-1 and LYVE-1 (p = 0.0185) than tumors from non-exercised mice, suggesting fewer stable endothelial cell junctions in lymphatic vessels. The higher lymphatic vessel density and higher number of open lumens present in tumors from exercised mice may contribute to an exercise-induced improved anti-tumor immune response, which has been previously reported. However, the lower ZO-1 expression on lymphatic endothelial cells in tumors from exercised mice may indicate lymphatic vasculature dysfunction and/or hyper-permeability. Further work is needed to assess the functional changes in tumor lymphatic vasculature by exercise, and how these changes impact the anti-tumor immune response and metastasis. Citation Format: Priya Tirumala, Jonghae Lee, Keri L. Schadler. Understanding the role of exercise in lymphatic vessel regulation in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5402.

Molecular Graphene Nanoribbon Junctions.

One of the challenges for the realization of molecular electronics is the design of nanoscale molecular wires displaying long-range charge transport. Graphene nanoribbons are an attractive platform for the development of molecular wires with long-range conductance owing to their unique electrical properties. Despite their potential, the charge transport properties of single nanoribbons remain underexplored. Herein, we report a synthetic approach to prepare N-doped pyrene-pyrazinoquinoxaline molecular graphene nanoribbons terminated with diamino anchoring groups at each end. These terminal groups allow for the formation of stable molecular graphene nanoribbon junctions between two metal electrodes that were investigated by scanning tunneling microscope-based break-junction measurements. The experimental and computational results provide evidence of long-range tunneling charge transport in these systems characterized by a shallow conductance length dependence and electron tunneling through >6 nm molecular backbone.

Photosystem I complexes form remarkably stable self-assembled tunneling junctions.

This paper describes large-area molecular tunneling junctions comprising self-assembled monolayers (SAMs) of light-harvesting protein complexes using eutectic Ga-In (EGaIn) as a top contact. The complexes, which are readily isolable in large quantities from spinach leaves, self-assemble on top of SAMs of [6,6]-phenyl-C61-butyric acid (PCBA) on gold (Au) supported by mica substrates (AuMica), which induces them to adopt a preferred orientation with respect to the electron transport chain that runs across the short axis of each complex, leading to temperature-independent rectification. We compared trimeric protein complexes isolated from thermophilic cyanobacteria to monomeric complexes extracted from spinach leaves by measuring charge-transport at variable temperatures and over the course of at least three months. Transport is independent of temperature in the range of 130 to 310 K for both protein complexes, affirming that the likely mechanism is non-resonant tunneling. The junctions rectified current and were stable for at least three months when stored at room temperature in ambient conditions, with the yield of working junctions falling from 100% to 97% over that time. These results demonstrate a straightforward strategy for forming remarkably robust molecular junctions, avoiding the fragility that is common in molecular electronics.

Insertion of methylene groups into functional molecules for high thermal stability and superior functionality of single-molecule transistors: a first-principles study

By inserting methylene groups at the molecule edges, stable molecule junctions are fabricated.

Supramolecular tunnelling junctions with robust high rectification based on assembly effects.

The performance of large-area molecular diodes can in rare cases approach the lower limit of commercial semiconductor devices but predictive structure-property design remains difficult as the rectification ratio (R) achieved by self-assembled monolayer (SAM) based diodes depends on several intertwined parameters. This paper describes a systematic approach to achieve high rectification in bisferrocenyl-based molecular diodes, HSCnFc-CC-Fc (n = 9-15) immobilised on metal surfaces (Ag, Au and Pt). Experiments supported by molecular dynamics simulations show that the molecular length and bottom electrode influence the SAM packing, which affects the breakdown voltage (VBD), the associated maximum R (Rmax), and the bias at which the Rmax is achieved (Vsat,R). From the electrical characterisation of the most stable Pt-SCnFc-CC-Fc//GaOx/EGaIn junctions, we found that VBD, Vsat,R, and Rmax all scale linearly with the spacer length of Cn, and that Rmax for all the SAMs consistently exceeds the "Landauer limit" of 103. Our data shows that the robust switching of M-SCnFc-CC-Fc//GaOx/EGaIn junctions is the result of the combined optimisation of parameters involving the molecular structure, the type of metal substrate, and the applied operating conditions (bias window), to create stable and high-performance junctions.

DNA-directed formation of plasmonic core-satellite nanostructures for quantification of hepatitis C viral RNA.

Hepatitis C virus (HCV) continues to be a significant public health challenge, affecting an estimated 71 million people globally and posing risks of severe liver diseases. Despite advancements in treatments, diagnostic limitations hinder the global elimination efforts targeted by 2030. This study introduces an innovative diagnostic approach, integrating catalytic hairpin assembly (CHA) with plasmonic core-satellite gold nanoparticle (AuNP) assemblies, to enable sensitive and specific detection of HCV RNA. We optimized the stoichiometry of DNA hairpins to form highly stable three-way junctions (3WJs), minimizing non-specific reactions in an enzyme-free, isothermal amplification process. The resulting dual-transduction biosensor combines colorimetric and surface-enhanced Raman spectroscopy (SERS) techniques, utilizing the Raman reporter malachite green isothiocyanate (MGITC) for signal generation. Our system targets a conserved 23-nucleotide sequence within the HCV 5'-UTR, essential for RNA replication, facilitating pan-genotypic HCV detection that complements direct-acting antiviral strategies. We evaluated the biosensor's efficacy using fluorescence spectroscopy, native PAGE, AFM, and TEM. Findings indicate that the 60 nm core AuNPs surrounded by 20 nm satellite AuNPs achieved a ten-fold increase in sensitivity over the 10 nm satellites, detecting HCV RNA concentrations as low as 1.706 fM. This sensitivity is crucial, given the extremely low viral loads present during early infection stages. Our research demonstrates the promise of enzyme-free molecular biosensors for HCV, with the potential to provide cost-efficient, rapid, point-of-care testing, although further sensitivity enhancements are needed to address the challenges of early-stage detection.

Method for Two-Dimensional Epithelial Monolayer Formation Derived from Mouse Three-Dimensional Small Intestinal Organoids.

The intestinal epithelium is composed of two distinct structures, namely, the villi and crypts. The base of the crypts contains intestinal stem cells (ISCs), which support the high regenerative capacity of the intestinal epithelium. With the establishment of the three-dimensional (3D) organoid culture method, the cellular and molecular mechanisms of differentiation, proliferation, and maintenance of ISCs have been widely analyzed. However, the sphere-like morphology of the 3D organoids prevents access to the apical side of the epithelium. To overcome this limitation, two-dimensional (2D) monolayer cultures derived from 3D organoids have been attempted; however, 2D culture methods for the mouse small intestine have not been well established. In this study, we developed a simple method that uses only commercially available materials, for the formation of 2D epithelial monolayers from mouse 3D small intestinal organoids. Using this method, confluent 2D epithelial monolayers were established within 4days. This monolayer showed stable tight junction and included ISCs and differentiated intestinal cells. It also showed physiologically relevant transepithelial electrical resistance values. On the basis of these findings, this method opens a novel platform for analyzing the physiology of the intestinal epithelium, its interaction with microbes, and mechanisms of villus formation.

Berberine promotes lacteal junction zippering and ameliorates diet-induced obesity through the RhoA/ROCK signaling pathway

BackgroundObesity has emerged as a global epidemic. Recent research has indicated that diet-induced obesity can be prevented by promoting lacteal junction zippering. Berberine, which is derived from natural plants, is found to be promising in weight reduction, but the underlying mechanism remains unspecified. PurposeTo determine whether berberine protects against obesity by regulating the lacteal junction and to explore potential molecular mechanisms. MethodsFollowing the induction of the diet-induced obese (DIO) model, mice were administered low and high doses of berberine for 4 weeks. Indicators associated with insulin resistance and lipid metabolism were examined. Various methods, such as Oil Red O staining, transmission electron microscopy imaging, confocal imaging and others were used to observe the effects of berberine on lipid absorption and the lacteal junction. In vitro, human dermal lymphatic endothelial cells (HDLECs) were used to investigate the effect of berberine on LEC junctions. Western Blot and immunostaining were applied to determine the expression levels of relevant molecules. ResultsBoth low and high doses of berberine reduced body weight in DIO mice without appetite suppression and ameliorated glucolipid metabolism disorders. We also found that the weight loss effect of berberine might contribute to the inhibition of small intestinal lipid absorption. The possible mechanism was related to the promotion of lacteal junction zippering via suppressing the ras homolog gene family member A (RhoA)/Rho-associated kinase (ROCK) signaling pathway. In vitro, berberine also promoted the formation of stable mature junctions in HDLECs, involving the same signaling pathway. ConclusionBerberine could promote lacteal junction zippering and ameliorate diet-induced obesity through the RhoA/ROCK signaling pathway.

A sensitive “off-on” electrochemiluminescence DNA sensor based on signal cascade amplification circuit and distance-dependent energy transfer

A sensitive “off-on” electrochemiluminescence (ECL) DNA sensor was constructed based on Exo III-assisted cascade amplification system. In the cascade amplification circuit, target DNA and Exo III cutting substrate were designed into an inverted T-shaped binding mode to form a stable DNA junction, thus effectively triggering Exo III digestion cycle. During the biosensor assembly process, ferrocene (Fc) and distance-dependent ECL resonance energy transfer (ECL-RET) and surface plasmon resonance (SPR) effects were introduced to regulate the ECL of semiconductor quantum dots (QDs). Carboxylated ZnCdSe/ZnS QDs were used as ECL signal probes and K2S2O8 was coreactant, and the initial cathodic ECL signal of QDs was efficiently quenched through electron and energy transfer with Fc and ECL-RET with Au NPs, leaving the system in “off” state. After the products of cascade amplification were introduced into the electrode surface, the single-stranded DNA modified with Fc was displaced, and the distance between Au NPs and QDs became farther, resulting in a transition from ECL-RET to SPR, and then a significant ECL signal boost was achieved, turning the system into “on” state. The combination of efficient cascade amplification system and sensitive “off-on” ECL signal change mode enabled the biosensing platform to detect target DNA with high selectivity (able to distinguish single-base mutated DNA) and ultra-high sensitivity (limit of detection was 31.67 aM, S/N = 3), providing a new perspective for designing highly sensitive and programmable ECL biosensors.

Extreme long-lifetime self-assembled monolayer for air-stable molecular junctions.

The molecular electronic devices based on self-assembled monolayer (SAM) on metal surfaces demonstrate novel electronic functions for device minimization yet are unable to realize in practical applications, due to their instability against oxidation of the sulfur-metal bond. This paper describes an alternative to the thiolate anchoring group to form stable SAMs on gold by selenides anchoring group. Because of the formation of strong selenium-gold bonds, these stable SAMs allow us to incorporate them in molecular tunnel junctions to yield extremely stable junctions for over 200 days. A detailed structural characterization supported by spectroscopy and first-principles modeling shows that the oxidation process is much slower with the selenium-gold bond than the sulfur-gold bond, and the selenium-gold bond is strong enough to avoid bond breaking even when it is eventually oxidized. This proof of concept demonstrates that the extraordinarily stable SAMs derived from selenides are useful for long-lived molecular electronic devices and can possibly become important in many air-stable applications involving SAMs.

Controlling piezoresistance in single molecules through the isomerisation of bullvalenes

Nanoscale electro-mechanical systems (NEMS) displaying piezoresistance offer unique measurement opportunities at the sub-cellular level, in detectors and sensors, and in emerging generations of integrated electronic devices. Here, we show a single-molecule NEMS piezoresistor that operates utilising constitutional and conformational isomerisation of individual diaryl-bullvalene molecules and can be switched at 850 Hz. Observations are made using scanning tunnelling microscopy break junction (STMBJ) techniques to characterise piezoresistance, combined with blinking (current-time) experiments that follow single-molecule reactions in real time. A kinetic Monte Carlo methodology (KMC) is developed to simulate isomerisation on the experimental timescale, parameterised using density-functional theory (DFT) combined with non-equilibrium Green’s function (NEGF) calculations. Results indicate that piezoresistance is controlled by both constitutional and conformational isomerisation, occurring at rates that are either fast (equilibrium) or slow (non-equilibrium) compared to the experimental timescale. Two different types of STMBJ traces are observed, one typical of traditional experiments that are interpreted in terms of intramolecular isomerisation occurring on stable tipped-shaped metal-contact junctions, and another attributed to arise from junction‒interface restructuring induced by bullvalene isomerisation.