Dipole Vector Research Articles

Enhancing the Performance of MoS2 Field-Effect Transistors Using Self-Assembled Monolayers: A Promising Strategy to Alleviate Dielectric Layer Scattering and Improve Device Performance.

Field-effect transistors (FETs) based on two-dimensional molybdenum disulfide (2D-MoS2) have great potential in electronic and optoelectronic applications, but the performances of these devices still face challenges such as scattering at the contact interface, which results in reduced mobility. In this work, we fabricated high-performance MoS2-FETs by inserting self-assembling monolayers (SAMs) between MoS2 and a SiO2 dielectric layer. The interface properties of MoS2/SiO2 were studied after the inductions of three different SAM structures including (perfluorophenyl)methyl phosphonic acid (PFPA), (4-aminobutyl) phosphonic acid (ABPA), and octadecylphosphonic acid (ODPA). The SiO2/ABPA/MoS2-FET exhibited significantly improved performances with the highest mobility of 528.7 cm2 V-1 s-1, which is 7.5 times that of SiO2/MoS2-FET, and an on/off ratio of ~106. Additionally, we investigated the effects of SAM molecular dipole vectors on device performances using density functional theory (DFT). Moreover, the first-principle calculations showed that ABPA SAMs reduced the frequencies of acoustic and optical phonons in the SiO2 dielectric layer, thereby suppressing the phonon scattering to the MoS2 channel and further improving the device's performance. This work provided a strategy for high-performance MoS2-FET fabrication by improving interface properties.

Scalable Analysis of Dipole Moment Fluctuations for Characterizing Intermolecular Interactions and Structural Stability.

Accurately predicting protein-ligand interactions is essential in computational molecular biochemistry and in silico drug development. Monitoring changes in molecular dipole moments through molecular dynamics simulations provides valuable insights into dipole-dipole interactions, which are critical for understanding protein structure stability and predicting protein-ligand binding affinity. In this study, we propose a novel method to monitor changes in the interangle between dipole vectors of residue molecules within proteins and ligand molecules, aiming to evaluate the strength and consistency of interactions within the complex. Additionally, we extend the concept of positional root-mean-square fluctuation (RMSF), commonly used for protein structure stability analysis, to dipole moments, thus defining dipole moment RMSF. This enables us to analyze the stability of dipole moments for each residue within the protein and compare them across residues and between binding and non-binding complexes. Using the CRBP1-retinoic acid complex as our model system, we observed a significant difference in the interangle change of dipole moments for the key residue at the residue-level between the non-binding and binding complexes. Furthermore, we found that the dipole moment RMSF value of the non-binding complex was substantially larger than that of the binding complex, indicating greater dipole moment instability in the non-binding complex. Leveraging the concept of scalability inherent in the calculation of dipole moment vectors, we systematically expanded the residues within the protein's primary secondary structure. Our dipole moment analysis approach can provide valuable predictive insights into complex candidates, especially in situations where experimental comparisons are challenging.

Evaluating aliphatic CF, CF2, and CF3 groups as vibrational Stark effect reporters.

Given the extensive use of fluorination in molecular design, it is imperative to understand the solvation properties of fluorinated compounds and the impact of the C-F bond on electrostatic interactions. Vibrational spectroscopy can provide direct insights into these interactions by using the C-F bond stretching [v(C-F)] as an electric field probe through the vibrational Stark effect (VSE). In this work, we explore the VSE of the three basic patterns of aliphatic fluorination, i.e., mono-, di-, and trifluorination in CF, CF2, and CF3 groups, respectively, and compare their response to the well-studied aromatic v(C-F). Magnitudes (i.e., Stark tuning rates) and orientations of the difference dipole vectors of the v(C-F)-containing normal modes were determined using density functional theory and a molecular dynamics (MD)-assisted solvatochromic analysis of model compounds in solvents of varying polarity. We obtain Stark tuning rates of 0.2-0.8cm-1/(MV/cm), with smallest and largest electric field sensitivities for CFaliphatic and CF3,aliphatic, respectively. While average electric fields of solvation were oriented along the main symmetry axis of the CFn, and thus along its static dipole, the Stark tuning rate vectors were tilted by up to 87° potentially enabling to map electrostatics in multiple dimensions. We discuss the influence of conformational heterogeneity on spectral shifts and point out the importance of multipolar and/or polarizable MD force fields to describe the electrostatics of fluorinated molecules. The implications of this work are of direct relevance for studies of fluorinated molecules as found in pharmaceuticals, fluorinated peptides, and proteins.

Separating Charge Centers of Chain Segments in Dielectric Elastomer through Steric Hindrance Engineering.

Theoretically, separating the positive and negative charge centers of the chain segments of dielectric elastomers (DEs) is a viable alternative to the conventional decoration of chain backbone with polar handles, since it can dramatically increase the dipole vector and hence the dielectric constant (ε') of the DEs while circumvent the undesired impact of the decorated polar handles on the dielectric loss (tan δ). Herein, a novel and universal method is demonstrated to achieve effective separation of the charge centers of chain segments in homogeneous DEs by steric hindrance engineering, i.e., by incorporating a series of different included angle-containing building blocks into the networks. Both experimental and simulation results have shown that the introduction of these building blocks can create a spatially fixed included angle between two adjacent chain segments, thus separating the charge center of the associated region. Accordingly, incorporating a minimal amount of these building blocks (≈5mol%) can lead to a considerably sharp increase (≈50%) in the ε' of the DEs while maintaining an extremely low tan δ (≈0.006@1kHz), indicating that this methodology can substantially optimize the dielectric performance of DEs based on a completely different mechanism from the established methods.

Multiscale insights into electric field orientation effects on piezoelectric strain and crystallography in P(VDF–TrFE) and P(VDF–TrFE–CTFE) fibers

This research primarily focuses on the effect of changing electric field directions on the crystal structure of piezoelectric fibers, notably, P(VDF–TrFE) and P(VDF–TrFE–CTFE). The study also explores the deformation mechanisms of fibers at micro- and nanoscales. A significant aspect of the research involves the application of parallel and perpendicular electric fields and observation of their impact on fiber properties. In situ wide-angle X-ray diffraction (WAXD) studies are crucial for determining the nanoscale properties when the electric field orientations change. The results show that the direction of the electric field significantly affects the sign (positive or negative) of the dipole vector within the β-crystal lattice structure of the fibers. This can be attributed to the rotation of dipole vectors in response to the electric field–fiber alignment angle. Furthermore, the research identifies the crystal plane (201,111)β as exhibiting the highest magnitude of piezoelectric response strain in the β phase. The study also employs scanning electron microscopy and digital image correlation (DIC) to reveal the material's morphology and to assess fiber strain distribution at the micrometer scale under different voltages. DIC results particularly highlight that stress concentration leads to the deformation of fibers into voids, which are spaces between fibers created by electrospinning. This work comprehensively elucidates how deformation works in piezoelectric polymers by connecting large-scale changes observed in fibers through DIC and small-scale changes observed in WAXD studies presenting the piezoelectric strain responses at the crystal plane.

Generation of a super-oscillation magnetization hotspot by reversing the electric dipole array radiation

We propose an all-optical approach to realize a super-oscillatory longitudinal magnetization hotspot with about 0.1λ in a 4π focusing system using time-reversed dipole radiation and vector diffraction theory calculations. Such a magnetization behavior is induced by focal fields of opposite polarities in the central and peripheral regions based on the inverse Faraday effect. By regulating the destructive interference in the central and peripheral regions of the focal field, a super-oscillating magnetization field is generated. Moreover, two important parameters affect the size of the magnetization field are also explored. Superoscillating magnetization hotspots in the focal region can be achieved by either increasing δ (the intensity of electric field) or reducing dn (the distance of electric field). The achieved ultrasmall magnetization spot shows great prospects in high-density magnetic recording, magnetic resonance imaging, and magnetic sensors.

Probing the in-plane dipole moment vector between ground and excited state of single molecules by the Stark effect.

Single molecules, embedded inside a well-defined insertion site of a single-crystalline host matrix, are sensitive probes of electric field via the induced Stark shift on their lifetime-limited electronic transition. Though the response of molecules to electric field has been shown to be relatively homogeneous, crystal symmetry allows for several, spectroscopically-indistinguishable, orientations of the net permanent dipole moment between the ground and excited state - the dipole vector - and this is problematic for measuring field orientation and magnitude. In this work, we measure for each terrylene molecule, embedded inside a new host matrix, the dipole vector independently by an electric field that we can rotate in the plane of the crystal. This single crystal host matrix, called [1]BenzoThieno[3,2-b]BenzoThiophene, induces a moderate symmetry breaking of the embedded centrosymmetric terrylene molecule, and gives rise to a net dipole moment of 0.28±0.09 Debye. Based on quantum chemistry calculations we propose an insertion site that best matches the experimental findings.

Spontaneous (two-pulse) photon echo in the nanoscale structure of self-organized quantum dots

We consider the coherent response of a medium with quasi-zero-dimensional structural units in the form of a photon echo upon resonant selective pulsed excitation of interband optical transitions, the inhomogeneous broadening of which is largely determined by the polydisperse composition of the nanocomposite. The process of formation of a photon echo is analyzed, when optical excitation leads to the formation of exciton complexes by resident electrons, which are localized in nanosized microcrystals in the limiting cases of strong and weak size quantization. By studying the coherent dynamics of the components of the pseudospin electric dipole vector, an expression is derived for the macroscopic specific polarization at the moment of emission of the photon echo signal. The consideration is carried out for a model nanocomposite medium on the example of a dielectric matrix with a system of semiconducting spherical inclusions (spherical quantum dots), the distribution over the radii of which is described by the Lifshitz-Slyozov formula.

Vectorial On‐Surface Synthesis of Polar 2D Polymer Crystals

AbstractThe asymmetric introduction of functional groups into polymers is promising due to its potential to provide novel electronic and magnetic properties. Though traditional on‐surface bottom‐up synthesis has succeeded in creating various types of polymers, it struggles at realizing asymmetry due to the difficulty of stereoregular polymerization and the tendency for overall polarity cancellation during agglomeration. Here, enabled by the low halogen‐contaminated metal surfaces provided by two‐zone chemical vapor deposition, “compass” precursors possessing three independent bonding, edge, and dipole vectors undergo isotactic polymerization via the vectorial self‐assembly of chiral precursor diradicals without the need for chiral catalysts required in conventional in‐solution polymerization. The isotactic polymers exhibit polar 2D crystalline structures due to the hetero‐edge CH–π interaction between the standing phenyl and butoxy group surpassing the homo‐edge interactions of π–π and CHCH. The developed vectorial on‐surface synthetic technique not only paves the way to the realization of stereoregular control but also unlocks unprecedented crystal engineering.

Ultrafast Photophysics of Regioisomeric Triphenylamine Dyes having Dipolar D-π-A-A and Octupolar D-(π-A-A)3 Character with a Benzothiazole Unit in Matched or Mismatched Orientation.

Benzothiazole is among prominent electron-withdrawing heteroarene moieties used in a variety of π-conjugated molecules. Its relative orientation with respect to the principal dipole vector(s) of chromophores derived thereof is crucial, affecting photophysical and nonlinear optical properties. Here we compare the photophysics and ultrafast dynamics of dipolar and octupolar molecules comprising a triphenylamine electron-donating core, ethynylene π-conjugated linker(s) and benzothiazole acceptor(s) having the matched or mismatched orientation (with respect to the direction of intramolecular charge transfer), while a carbaldehyde group is attached as an auxiliary acceptor. Among chromophores without the auxiliary acceptor, stronger fluorescence solvatochromism and faster excited state dynamics are exhibited for the derivatives with the mismatched geometry. On the contrary, introduction of the auxiliary acceptor to the benzothiazole unit enhances the intramolecular charge transfer ICT (featuring ultrafast dynamics of the excited state) for the matched geometry. The data confirm the crucial role of the relative orientation of asymmetric heteroaromatic unit (regioisomeric effect) in dipolar as well as in multipolar molecules in tuning linear and nonlinear optical properties as well as excited state dynamics.

Dipole alignment of water molecules flowing through a carbon nanotube

The flow of water through nanochannels has promising applications in desalination, energy conversion, and nanomedicine. We have used molecular dynamics simulations to show that the water molecules passing through a wide single-walled carbon nanotube (CNT) get aligned by the flow to have a net dipole moment along the flow direction. With increasing flow velocity, the net dipole moment first increases and eventually saturates to a constant value. This behavior is similar to that of an Ising chain with the flow velocity acting as an effective aligning field. We show that the microscopic origin of this behavior is the preferential entry of water molecules with their dipole vectors pointing inward along the CNT axis.

Height Measurement for Meter Wave Polarimetric MIMO Radar with Electrically Long Dipole under Complex Terrain

Height measurement of meter wave radar is a difficult and important problem. This paper studies the height measurement of meter wave polarimetric (MWP)-MIMO array radar under complex terrain. The traditional electrically short dipole has low radiation efficiency, and the collocated dipole vector antenna has strong mutual coupling. This paper proposes to use electrically long dipoles and separated vector antennae to solve the problems of low radiation efficiency and strong mutual coupling. In addition, different from the traditional flat terrain, the research of this paper is based on the conditions of complex undulating terrain. First, the height measurement signal model of the MWP-MIMO radar with separated electrically long dipole under the complex terrain is derived. Then, a preprocessing method of block orthogonal matching pursuit is proposed to obtain the coarse estimation of the target’s elevation. Then, under the guidance of the coarse estimation, the generalized MUSIC algorithm is used to obtain the high-precision elevation estimation of the target, and then the height measurement of the target is obtained according to the geometric relationship. Finally, the effectiveness of the proposed algorithm is proved by computer simulations.

Progress on the magnetic rotation in the nuclei of <italic>A</italic>~60 and <italic>A</italic>~80 mass regions

<p indent="0mm">Nuclear collective rotation, which involves coherent contributions from many nucleons, has been well known for a long time. It is ascribed as a consequence of deformation and gives rise to regular rotational bands, which are characterized by strong electric quadrupole (<italic>E</italic>2) transitions. Studies of the rotational bands in nuclei have been in the forefront of nuclear structure physics and have led to many interesting phenomena including the backbending, superdeformed bands, and chiral doublet bands. In 1990s, a new type of rotational-like sequences, which have strong <italic>M</italic>1 transitions and weak or vanishing <italic>E</italic>2 transitions, have been discovered in weakly deformed or near-spherical nuclei and attracted a lot of interests. This new type of rotational structure cannot be understood in terms of conventional rotation of deformed nuclei but has been successfully interpreted in terms of the shears mechanism. In this interpretation, nuclear orientation is specified by the current distribution rather than the deformation. The magnetic dipole vector arises from proton particles (holes) and neutron holes (particles) in high-<italic>j</italic> orbitals, and rotates around the total angular momentum vector. In the subsequent experimental studies, the magnetic rotation phenomenon were found in the <italic>A</italic>~60, <italic>A</italic>~80, <italic>A</italic>~110, <italic>A</italic>~140, and <italic>A</italic>~190 mass regions. Here, we report the studies of magnetic rotation in the <italic>A</italic>~80 and <italic>A</italic>~60 mass regions. The high-spin structures of⁷⁵As, ⁷⁹Se and ⁶²Cu were respectively populated via ⁷⁰Zn(⁹Be, 1p3n)⁷⁵As, ⁸²Se(α, α3n)⁷⁹Se and ⁵⁴Cr(¹²C, 1p3n)⁶²Cu heavy ion fusion–evaporation reactions. The dipole bands were established for the first time in these three nuclei. The properties of these dipole bands are investigated in terms of the self-consistent tilted axis cranking covariant density functional theory. In the calculation for ⁷⁵As, ⁷⁹Se and ⁶²Cu, the valence nucleon configurations of π[(1g_9/2)¹(1f_5/2)⁻²]<x content-type="symbol">Ä</x>υ[(1g_9/2)⁵(fp)⁻³], <sc>π[(1g_9/2)¹(fp)⁵]</sc><x content-type="symbol">Ä</x>υ[(1g_9/2)⁵] and π[(f_7/2)⁻¹(p_3/2f_5/2)²]<x content-type="symbol">Ä</x>υ[(g_9/2)¹(p_3/2f_5/2)⁴] are used, respectively. The calculated energy spectra reasonably reproduce the experimental excitation energies of ⁷⁵As, ⁷⁹Se, and ⁶²Cu. The evolutions of deformation parameters <italic>β</italic> and <italic>γ</italic> of these dipole bands driven by increasing rotational frequency are discussed. In contrast to the relatively large triaxial deformation of the dipole bands in ⁷⁵As and ⁶²Cu, the dipole band of ⁷⁹Se has a relatively axially symmetric and small prolate deformation. With the increase of rotational frequency, the <italic>β </italic>deformations for ⁷⁵As, ⁷⁹Se and⁶²Cu behave in a similar way, i.e., a smooth decrease in <italic>β</italic>. Meanwhile, both <italic>γ</italic> values of ⁷⁵As and ⁶²Cu show a smoothly increasing tendency. Based on the examination of the composition of the proton and neutron angular momentum vectors <italic>J</italic>_π and <italic>J</italic>_υ as well as the total angular momentum <italic>J</italic>_tot=<italic>J</italic>_π+<italic>J</italic>_υ at both the bandhead and the maximum rotational frequency, the dipole bands in ⁷⁵As and ⁷⁹Se can be interpreted as novel stapler bands, where the valence nucleons in (1g_9/2) orbital rather than the collective core are responsible for the closing of the stapler of angular momentum. Although not firmly confirmed in experiments, the dipole structure in ⁶²Cu may be a candidate of magnetic rotational bands. To unambiguously confirm this, further experimental investigations are strongly desirable.

Surface Properties of N,N-Dimethylformamide-Water Mixtures, As Seen from Computer Simulations.

The liquid-vapor interface of N,N-dimethylformamide (DMF)-water mixtures, spanning the entire composition range, is investigated in detail at 298 K by molecular dynamics simulation and intrinsic surface analysis. DMF molecules are found to adsorb strongly at the liquid surface, but this adsorption extends only to the first molecular layer. Water and DMF molecules mix with each other on the molecular scale even in the surface layer; thus, no marked self-association of any of the components is seen at the liquid surface. The major surface component prefers such orientation in which the molecular dipole vector lays parallel with the macroscopic plane of the surface. On the other hand, the preferred orientation of the minor component is determined, at both ends of the composition range, by the possibility of H-bond formation with the major component. The lack of H-donating ability of DMF leads to a rapid breakup of the percolating H-bond network at the surface; due to the strong adsorption of DMF, this breakup occurs below the bulk phase DMF mole fraction of 0.03. The disruption of the surface H-bond network also accelerates the exchange of both species between the liquid surface and bulk liquid phase, although, for water, this effect becomes apparent only above a bulk phase DMF mole fraction of 0.4. H-bonds formed by a DMF and a water molecule live, on average, 25-60% longer than those formed by two water molecules at the liquid surface. A similar, but smaller (i.e., about 10-20%) difference is seen in the bulk liquid phase. The enhanced surface mobility of the molecules results in 2-6 times larger diffusion coefficient and 2-5 times shorter H-bond lifetime values at the liquid surface than in the bulk liquid phase. The diffusion of both molecules is slowed down in the presence of the other species; in the case of DMF, this effect is caused by the formation of water-DMF H-bonds, whereas for water, steric hindrances imposed by the bulky DMF neighbors are responsible for this slowing down.

Capturing the Polarization Response of Solvated Proteins under Constant Electric Fields in Molecular Dynamics Simulations.

We capture and compare the polarization response of a solvated globular protein ubiquitin to static electric (E-fields) using atomistic molecular dynamics simulations. We collectively follow E-field induced changes, electrical and structural, occurring across multiple trajectories using the magnitude of the protein dipole vector (Pp ). E-fields antiparallel to Pp induce faster structural changes and more facile protein unfolding relative to parallel fields of the same strength. While weak E-fields (0.1-0.5 V/nm) do not unfold ubiquitin and produce a reversible polarization, strong E-fields (1-2 V/nm) unfold the protein through a pathway wherein the helix:β-strand interactions rupture before those for the β1-β5 clamp. Independent of E-field direction, high E-field induced structural changes are also reversible if the field is switched off before Pp exceeds 2 times its equilibrium value. We critically examine the dependence of water properties, protein rotational diffusion and E-field induced protein unfolding pathways on the thermostat/barostat parameters used in our simulations.

A unique cardiac electrocardiographic 3D model. Toward interpretable AI diagnosis.

Mathematical models of cardiac electrical activity are one of the most important tools for elucidating information about heart diagnostics. In this paper, we present an efficient mathematical formulation for this modeling simple enough to be easily parameterized and rich enough to provide realistic signals. It relies on a five dipole representation of the cardiac electric source, each one associated with the well-known waves of the electrocardiogram signal. Beyond the physical basis of the model, the parameters are physiologically interpretable as they characterize the wave shape, similar to what a physician would look for in signals, thus making them very useful in diagnosis. The model accurately reproduces the electrocardiogram signals of any diseased or healthy heart. This new discovery represents a significant advance in electrocardiography research. It is especially useful for diagnosis, patient follow-up or decision-making on new therapies; is also a promising tool for well-performing, transparent and interpretable AI approaches.

Ferroelectric Ordering in Nanosized PbTiO3.

The insight into the three-dimensional configuration of ferroelectric ordering in ferroelectric nanomaterials is motivated by the application of the development of functional nanodevices and the structural designing. However, the atomic deciphering of the spatial distribution of ordered structure remains challenging for the limitation of dimension and probing techniques. In this paper, a neutron pair distribution function (nPDF) was utilized to analyze the spontaneous polarization distribution of zero-dimensional PbTiO3 nanoparticles in three dimensions, via the application of reverse Monte Carlo (RMC) modeling. The comprehensive identification with transmission electron microscopy verified the linear characteristics of polarization along the c-axis in the main body, while electric polarization distribution on the surface was enhanced abnormally. In addition, the correlation of dipole vectors extending to three unit cells below the surface is retained. This work shows an application of the micro/macroscale information to effectively decode the polarization structure of nanoferroelectrics, providing new views of designing nanoferroelectric devices.

Adiabatic inversion in an array of spherical microcrystals under conditions of the Stark effect

A model of the process of adiabatic tracking on a system of size-quantized levels of isolated spherical quantum dots (QDs) in an electric field is proposed, which, due to the Stark effect, creates intervals between levels varied by the field. The method of perturbation theory for degenerate states is used to analyze the splitting and partial lifting of the degeneracy of levels in the lower part of the spectrum of a spherical QD. Using the pseudospin electric dipole vector model, we study the process of adiabatic inversion on a system of selected pairs of QD levels, the energy intervals between which are subject to a monotonous change by an external electric field. The course of the process of adiabatic tracking is analyzed in the case of a linear dependence of the electric field on time, at different values of the amplitude of the radiation pulse field. An asymmetry in the course of change in the amplitude profile of the inversion oscillations is revealed, which can affect the process of detecting non-stationary stimulated amplification. It is pointed out that it is possible to trace the inversion process, when the variation of the resonance detuning can be determined by the selection of the radii of the spherical QDs.

Molecular understanding of aqueous electrolyte properties and dielectric effect in a CDI system

Capacitive deionization (CDI) provides performance of ion removal via electrodes with high porosity and confined nanopores. Hitherto, the main emphasis has been on the enhancement of removal efficiency based on a lab-scale setup, neglecting anomalous dynamic and dielectric properties in confinement. This work was completed to reveal structural and dynamic properties of hydrated ions in a 3-nm nanopore of a CDI electrode using molecular dynamics simulation based on the nonpolarizable (SPC/E) and polarizable (SWM4-DP/-NDP) force fields. It was shown that all the force fields caused marginal differences in hydration structure but greater differences in ionic dynamics. Furthermore, dielectric constants obtained from all the force fields were lower in confinement than in bulk, although they were slightly higher in the polarizable models. Angular distributions of water bonds and dipole vectors revealed this decrease was caused by the restriction of water rotational dynamics and hence a depression of dipolar fluctuations. Hydrogen bond lifetimes indicated that higher availability of hydrogen bonding sites also facilitated increasing the dielectric constant as it allowed a more frequent “switch” of the fast hydrogen bond. Both the angular distribution and the hydrogen bonding contributed to the slightly higher dielectric constant in the polarizable model than in the nonpolarizable model. Our local sensitivity analysis of a ion transport model revealed that the dielectric constant greatly determined ion transport in the electrode, although the diffusion coefficients of typical ions had limited influences. This work provides fundamental theories and great implications for the theoretical analysis of ion electrosorption in a CDI electrode and enhances its application in water treatment.

Understanding Interface Dipoles at an Electron Transport Material/Electrode Modifier for Organic Electronics.

Interface dipoles formed at an electrolyte/electrode interface have been widely studied and interpreted using the “double dipole step” model, where the dipole vector is determined by the size and/or range of motion of the charged ions. Some electron transport materials (ETMs) with lone pairs of electrons on heteroatoms exhibit a similar interfacial behavior. However, the origin of the dipoles in such materials has not yet been explored in great depth. Herein, we systematically investigate the influence of the lone pair of electrons on the interface dipole through three pyridine derivatives B2–B4PyMPM. Experiments show that different positions of nitrogen atoms in the three materials give rise to different hydrogen bonds and molecular orientations, thereby affecting the areal density and direction of the lone pair of electrons. The interface dipoles of the three materials predicted by the “double dipole step” model are in good agreement with the ultraviolet photoelectron spectroscopy results both in spin-coated and vacuum-deposited films. These findings help to better understand the ETMs/electrode interfacial behaviors and provide new guidelines for the molecular design of the interlayer.