Charge Transport Properties of Tetrabenz[a,c,h,j]-anthracene Derivatives

Charge transport properties of F, OH, OCH3, SH and SCH3-substituted tetra- benz[a,c,h,j]- anthracene derivative molecules have been investigated theoretically at the B3LYP/6-31G＊＊ level using Marcus theory. The results showed that at 300 K, the hole or electron transport capability of F or SH-substituted molecules was better obviously than that of OH or OCH3-substituted molecules, The electron transport capability of SCH3-substituted and F or SH-substituted molecules was superior to their hole transport capability, respectively. F, SH or SCH3-substituted tetrabenz[a,c,h,j]-anthracene derivative molecules can be used as electron transport materials.

Tuning crystal orientation and charge transport of quasi-2D perovskites via halogen-substituted benzylammonium for efficient solar cells

Quasi-two-dimensional(quasi-2D)perovskites with high stability usually suffers from poor device efficiency.Chemical tuning of the spacer cations has been an effective strategy to achieve efficient and stable quasi-2D perovskite solar cells.Here,we demonstrate that 3-halogon-substituted benzylammonium iodide(3X-BAI,X=F,Cl,Br,I)can significantly affect the orientation of low-dimensional perovskites and charge transport from perovskite to hole extraction layer,as well as device performance.With 3Br-BAI,we achieve the highest device efficiency of 13.21%for quasi-2D perovskites with a nominal n=3 average composition.Our work provides a facile approach to regulate vertical crystal orientation and charge transport via tuning the molecular structure of organic spacer toward high performance quasi-2D perovskite solar cells.

Theoretical Investigation on the Charge Transport Properties of 2,5-Di(cyanovinyl)-thiophene/furan with the Kinetic Monte Carlo Method

Exploring, designing, and synthesizing novel organic field-effect transistor （OFET） materials have kept an important and hot issue in organic electronics. In the current work, the charge transport properties for 2,5-di（cyanovinyl）thiophene/furan crystal associating two pentafluorophenyl units linked via the azomethine bond, CTE and CFE have been theoretically investigated by means of density functional theory （DFT） calculations coupled with the incoherent charge-hopping mechanism and the kinetic Monte Carlo simulation. Results show that these two compounds possess remarkably low-lying HOMO （-7.0 eV） and LUMO （-4.0 eV） levels, as well as large electron affinities （〉 3.0 eV）, which indicate their high stability exposed to air as promising OFET materials. However, the ph value at room temperature （T = 300 K） is predicted to be 2.058x10^7 cm26Vl·s-1, and the is as low as 9.834^10-8 cm2-V-l.s-1 for CFT crystal. Meanwhile, these two values are 7.561 x 10-8 and 8.437 x 10-8 cm2.V-I.s-1 for the CFE crystal, respectively. Furthermore, the simulation of angle-dependent mobility in the a-b, a-c, and b-c crystal planes shows that the charge transport in CTE and CFE crystals is remarkably anisotropic, which maybe is helpful for the fabrication of high-performance OFET devices.

Charge Transport in Bifidobacterium animalis subsp.lactis BB-12 under Various Atmospheres

The influence of relative humidity (RH) on quasistatic current-voltage (I-V) characteristics of Bifidobacterium animalis subsp. lactis BB-12 thin layers was studied for the first time. The value of electrical conductivity in 75% RH was found to be in the order of 10-7 (ohm·cm)-1, which was 106 orders of magnitude higher than that observed in dry atmosphere. It was concluded that RH played a key role in hysteresis behavior of the measured (I-V) characteristics. FTIR measurements showed that under water moisture environment, the associated bonds between amine and carboxyl group were greatly strengthened that was the source of free charge carries after ionization. The surface charge of Bifidobacterium animalis subsp. lactis BB-12 was found to be negative by zeta potential measurements, claiming that electrons were the charge carriers.

Influence of shape effect on dynamic surface charge transport mechanism of cellular electret after corona discharge

Surface charge accumulation and transport on cellular polypropylene play an important role in nanogenerators,which could have a potential impact on energy harvesting and wearable devices for zero carbon energy systems and the internet of things.Different shapes have different charge accumulation and decay characteristics of the polymer.Therefore,we studied the influence of the sample’s shape on the surface charge decay by experiment and modeling.The surface potential of square and circular cellular polypropylene was measured by a two-dimensional surface potential measurement system with electrostatic capacitive probe.The experimental result shows that the surface potential distribution of the square sample dissipates non-uniformly from the bell shape to a one-sided collapsed shape,while that of the circular sample dissipates uniformly from the bell shape to the crater-like shape.Moreover,the simulated results of the initial surface potential distributions of the square and circular cellular polypropylene are consistent with the experimental results.The investigation demonstrates that the charge transport process is correlated with the shape of the sample,which provides significant reference for designing electret material used for highly efficient nanogenerators.

Influence of charge transport layer on the crystallinity and charge extraction of pure tin-based halide perovskite film

As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].

Crucial role of charge transporting layers on ion migration in perovskite solar cells

The device preconditioning dependent hysteresis and the consequential performance degradation hinder the actual performance and stability of the perovskite solar cells. Ion migration and charge trapping in the perovskite with large contribution from grain boundaries are the most common interpretations for the hysteresis. Yet, the high performing devices often include intermediate hole and electron transporting layers, which can further complicate the dynamical process in the device. Here, by using Kelvin Probe Force Microscopy and Confocal Photoluminescence Microscopy, we elucidate the impact of chargetransporting layers and excess MAI on the spatial and temporal variations of the photovoltage on the MAPbI3-based solar cells. By studying the devices layer by layer, we found that the light-induced ion migration occurs predominantly in the presence of an imbalanced charge extraction in the solar cells, and the charge transporting layers play crucial role in suppressing it. Careful selection and processing of the electron and hole-transporting materials are thus essential for making perovskite solar cells free from the ion migration effect.

Charge Transport Processes of Immobilized Heteropolyanions at Self-assembled Monolayer Modified Gold Electrode by Electrochemical Quartz Crystal Microbalance Measurement

The in situ electrochemical quartz crystal microbalance（EQCM） technique was used to investigate the ion transport of immobilized heteropolyanions at a self-assembled monolayer（SAM） modified gold electrode during electrochemical redox process.A mixed transfer method was presented to analyse the abnormal change of resonant frequency based on the simultaneous insertion/extraction of different ions.The results indicate that the migration of HSO4-anions was indispensable in the redox process of the heteropolyanions in a 1 mol/L H2SO4 solution and played a key role in the abnormal change of the resonant frequency.Such a change was attributed to different packing densities derived by means of differently immobilized methods.

Coherent charge transport in ferromagnet/semiconductor nanowire/ferromagnet double barrier junctions with the interplay of Rashba spin-orbit coupling, induced superconducting pair potential,and external magnetic field

By solving the Bogoliubov-de Gennes equation, the influence of the interplay of Rashba spin-orbit coupling, induced superconducting pair potential, and external magnetic field on the spin-polarized coherent charge transport in ferromagnet/semiconductor nanowire/ferromagnet double barrier junctions is investigated based on the Blonder-Tinkham-Klapwijk theory. The coherence effect is characterized by the strong oscillations of the charge conductance as a function of the bias voltage or the thickness of the semiconductor nanowire, resulting from the quantum interference of incoming and outgoing quasiparticles in the nanowire. Such oscillations can be effectively modulated by varying the strength of the Rashba spin-orbit coupling, the thickness of the nanowire, or the strength of the external magnetic field. It is also shown that two different types of zero-bias conductance peaks may occur under some particular conditions, which have some different characteristics and may be due to different mechanisms.

Phase transition and charge transport through a triple dot device beyond the Kondo regime

Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single,double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown.

Theoretical Study on the Charge Transport Properties of Coronene and Its Derivatives

Molecular structures, reorganization energies and charge transport matrix elements of coronene and its fluoro-, hydroxyl- and sulfhydryl-substituted derivatives have been studied at the B3LYP/6-31G＊＊ level. Based on the semi-classical model of electron transfer, charge transport rate constants of the title molecules have been calculated. The results indicate that the coronene molecule is helpful to the transport of negative charge, and the transport rate of positive charge is between those of hexaazatriphenylene and triphenylene.

A Quantum Chemical Screening of Two Imidazole-Chalcone Hybrid Ligands and Their Pd, Pt and Zn Complexes for Charge Transport and Nonlinear Optical (NLO) Properties: A DFT Study

A quantum chemical screening of two imidazole-based chalcone ligands: 2- [1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol and 2-[1-(3-(1H- imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol (hereinafter referred to as HL1 and HL2 respectively) and their Pd, Pt and Zn chelates for charge transport and nonlinear optical (NLO) properties, is reported via dispersion- corrected density functional theory (DFT-D3) and time-dependent DFT (TD- DFT) methods. From our results, Pd and Pt complexes have been observed to show excellent hole-transport properties, owing to their very small reorganization energies. The light extraction efficiency of the HL1-Pt complex was deduced to be particularly impressive, thus suitable for the manufacture of hole transport layer in violet light emitting diodes (LEDs). Moreover, redox potentials and chemical stability studies have enabled us to validate the greater stability in moisture (towards oxidation), of HL2 complexes compared to their HL1 counterparts. The first and second hyperpolarizabilities of both ligands and their complexes have been found to be outstandingly higher than those of the push-pull prototypical, para-nitroaniline by factors of up to 12 in the case of HL2. These compounds, with the exception of the HL2-Pt complex, are thus interesting candidates having wide transparency tradeoffs for NLO efficiency in the manufacture of optoelectronic and photonic devices capable of second and third-order NLO response. Finally, metal chelation has been established to enhance the NLO response of all the chalcone-based imidazole ligands investigated as a result of metal-ligand charge transfer and ligand- metal charge transfer electronic transitions identified in the resulting complexes with the exception of the zinc complexes.

Realizing compact three-dimensional charge transport networks of asymmetric electron acceptors for efficient organic solar cells

Asymmetry has been demonstrated an effective approach in recent years to tune the structural and energetic orders of nonfullerene electron acceptors(NFAs)to prepare efficient organic solar cells(OSCs).In this article,five asymmetric NFAs,namely C9BTP-BO-Th Cl-2F,C9BTP-BO-Cl-2F,C9BTP-BO-2Cl-2F,C7BTP-BO-2Cl-2F and C5BTP-BO-2Cl-2F possessing varied asymmetric end-groups and alkyl chains are synthesized to tune the charge transport networks formed within these NFAs.We found that the enhanced planarity in the asymmetric NFA can facilitate closerπ-πstacking distance in either the A-to-A or A-toD type NFA dimers,whilst the larger dipole moment can promote the formation of three-dimensional(3D)charge transport networks among NFAs.Taking those advantages,C7BTP-BO-2Cl-2F exhibit a compact 3D honeycomb network with a high packing coefficient of 72.1%and molecular packing density of 0.48 g/cm^(3),contributing to a superior power conversion efficiency of 18.0%when employing PM6 as the donor,with an open-circuit voltage of 0.85 V,short-circuit current of26.7 m A cm^(-2)and fill factor of 79.3%.Our work provides guidelines in engineering the end group and side chains of asymmetric NFAs to achieve compact charge transport networks for high efficiency OSCs.

Modulating single-molecule charge transport through external stimulus

Understanding and tuning charge transport over a single molecule is a fundamental topic in molecular electronics.Single-molecule junctions composed of individual molecules attached to two electrodes are the most common components built for single-molecule charge transport studies.During the past two decades,rapid technical and theoretical advances in single-molecule junctions have increased our understanding of the conductance properties and functions of molecular devices.In this perspective article,we introduce the basic principles of charge transport in single-molecule junctions,then give an overview of recent progress in modulating single-molecule transport through external stimuli such as electric field and potential,light,mechanical force,heat,and chemical environment.Lastly,we discuss challenges and offer views on future developments in molecular electronics.

Oxygen doping modulating thermal-activated charge transport of reduced graphene oxide for high performance temperature sensors

Graphene and its derivatives have sparked intense research interest in wearable temperature sensing due to their excellent electric properties,mechanical flexibility,and good biocompatibility.Despite these ad-vantages,the weak temperature dependence of charge transport makes them difficult to achieve a highly sensitive temperature response,which is one of the remaining bottlenecks in the progress towards practi-cal applications.Unfortunately,detailed knowledge about the key factors of the charge transport temper-ature dependence in this material that determines the critical performance of electrical sensors is very limited up to now.Here,we reveal that oxygen absorption on the ultrathin reduced graphene oxide(RGO)films(~3 nm)can significantly increase their conductance activation energy over 200%and thus greatly improve the temperature dependence of thermal-activated charge transport.Further investigations sug-gest that oxygen introduces the deep acceptor states,distributed at an energy level~0.175ev from the valence-band maximum,which allows a highly temperature-dependent impurity ionization process and the resulting vast holes release in a wide temperature range.Remarkably,our temperature sensors based on oxygen-doped ultrathin RGO films show a high sensitivity with temperature conductive coefficient of 14.58%K^(-1),which is one order of magnitude higher than the reported CNT or graphene-based devices.Moreover,the ultrathin thickness and high thermal conductivity of RGo film allow an ultrafast response time of~86ms,which represents the best level of temperature sensors based on soft materials.Profit-ing from these advantages,our sensors show good capacity to identify the slight temperature difference of human body,monitor respiratory rate,and detect the environmental temperature.This work not only represents substantial performance advances in temperature sensing,but also provides a new approach to modulate the charge transport temperature dependence,which could be benefited to both device design and fundamental research.

The role of externally-modulated electrostatic interactions in amplifying charge transport across lysine-doped peptide junctions

Many evolved biomolecular functions such as ion pumping or redox catalysis rely on controlled charge transport through the polypeptide matrix, which can be regulated by shifts in molecular protonation states and dependent supramolecular packing modes in response to environmental cues. However, the exact roles of such dynamic, non-covalent interactions in peptide charge transport have remained elusive. To tackle this challenge, here we report the modulation of charge transport in a series of lysine(Lys)-substituted hepta-glycine(Gly) peptide self-assembled monolayers(SAMs) on template-striped gold(Au^(TS)) bottom electrodes with eutectic gallium-indium(EGaIn) liquid metal top electrodes. We demonstrate systematic modulation of hydrogen bonding and more general electrostatic interactions by shifting the position of the charged Lys-residue and creating different protonation patterns by changing the environmental pH in the Au^(TS)/peptide//Ga Ox/EGa In junctions. The effective modulation is evidenced by current density-voltage(J-V) measurements combined with SAM characterization using ultraviolet photoelectron spectroscopy(UPS) and angle-resolved X-ray photoelectron spectroscopy(ARXPS), polarization modulation-infrared reflection-absorption spectroscopy(PM-IRRAS), and molecular dynamics(MD) simulations. Decreasing the hydrogen bonding inside the peptide SAMs and increasing the electrostatic interactions by environmental counterions amplifies the charge transport differently with Lys-position, which means that the sensitive electrical response of peptide SAMs can be tuned by the peptide sequence. Our results provide insights into the relationship between molecular design and in situ modulation of charge transport properties for the development of bionanoelectronics.

Tuning Charge Transport of Oligopeptide Junctions via Interfacial Amino Acids

Comprehensive Summary,The charge transport through peptides can imitate the corresponding processes in more complicated proteins,enabling us to develop high-performance bioelectronic devices and to understand the mechanisms of biomolecular recognition and information transfer.While charge transport modulation through individual peptides has been achieved via various covalent strategies,the intermolecular modulation is still very challenging,which may capture the charge transport between proteins.To tackle this challenge,we used well-defined self-assembled monolayers(SAMs)of oligopeptides as a model to imitate the interface of proteins and explored an interfacial amino acid strategy for charge transport modulation.We showed that non-covalently interfaced charged amino acids(e.g.,arginine)effectively attenuated the charge transport of glutamic acid terminated polyglycine peptide SAMs.By analyzing the relationship of the charge transport with the molecular frontier orbital relative to the Fermi energy level of the electrode,the molecule-electrodes coupling(Γ),and the trends in skewness and kurtosis with voltage and the dielectric constant(εr),we showed that the attenuation was from the decreasedΓand the reduced polarizability.We present an efficient strategy to modulate the charge transport of oligopeptide-SAM junctions by intermolecular interactions,which will advance our understanding of charge transport in biological systems and facilitate developing future electronics.

Theoretical analyses on the one-dimensional charged particle transport in a decaying plasma under an electrostatic field

The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell(PIC)simulations with the ion extraction process in a laser-induced plasma as the major research background.Based on the theoretical analyses,the transport process of the charged particles including electrons and ions can be divided into three stages:electron oscillation and ion matrix sheath extraction stage,sheath expansion and ion rarefaction wave propagation stage and the plasma collapse stage,and the corresponding criterion for each stage is also presented.Consequently,a complete analytical model is established for describing the ion extraction flux at each stage during the decaying of the laser-induced plasmas under an electrostatic field,which is also validated by the PIC modeling results.Based on this analytical model,influences of the key physical parameters,including the initial electron temperature and number density,plasma width and the externally applied electric voltage,on the ratio of the extracted ions are predicted.The calculated results show that a higher applied electric potential,smaller initial plasma number density and plasma width lead to a higher ratio of the extracted ions during the first stage;while in this stage,the initial electron temperature shows little effect on it.Meanwhile,more ions will be extracted before the plasma collapse once a higher electric potential is applied.The theoretical model presented in this paper is helpful not only for a deep understanding to the charged particle transport mechanisms for a bounded decaying plasma under an applied electrostatic field,but also for an optimization of the ion extraction process in practical applications.

Charge Transport in Disordered Graphene-Based Low Dimensional Materials

Two-dimensional graphene,carbon nanotubes,and graphene nanoribbons represent a novel class of low dimensional materials that could serve as building blocks for future carbon-based nanoelectronics.Although these systems share a similar underlying electronic structure,whose exact details depend on confi nement effects,crucial differences emerge when disorder comes into play.In this review,we consider the transport properties of these materials,with particular emphasis on the case of graphene nanoribbons.After summarizing the electronic and transport properties of defect-free systems,we focus on the effects of a model disorder potential(Anderson-type),and illustrate how transport properties are sensitive to the underlying symmetry.We provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons,and discuss the onset of weak and strong localization regimes,which are genuinely dependent on the transport dimensionality.We also consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation.

Modulation of Microstructure and Charge Transport in Polymer Monolayer Transistors by Solution Aging

A few monolayers of organic semiconductors adjacent to the dielectric layer are of vital importance in organic field-effect transistors due to their dominant role in charge transport.In this report,the 2-nm-thick polymer monolayers based on poly(3-hexylthiophene)with different molecular weights(M_(n))were fabricated using dip-coating technique.During the monolayer(solid state)formation from the solution,a disorder-to-order transition of polymer conformation is observed through UV-vis absorption measurement.Meanwhile,high Mn polymer monolayer generates higher crystalline fibrillar microstructure than the low Mn one due to the strongerπ–πintermolecular packing between polymers.More importantly,the solution aging procedure is utilized to further improve the morphology of polymer monolayers.It is obvious that after aging for 6 d,both fiber dimension and density as well as conjugation length are significantly increased under the same processing conditions in comparison to the fresh solution,and consequently the field-effect mobilities are remarkably enhanced by 2—4 times.Note that the maximum mobility of 0.027 cm2·V^(–1)·s^(–1)is among the highest reported values for poly(3-hexylthiophene)monolayer transistors.These results demonstrate a simple but powerful strategy for boosting the device performance of polymer monolayer transistors.