Descriptor construction method of asymmetric metal / organic / metal interface rectification ratio

Abstract

The invention discloses an asymmetric metal / organic / metal interface rectification ratio descriptor construction method, and particularly relates to the technical field of molecular electronic device design and performance prediction. The method comprises the following steps: firstly, constructing a metal (111) crystal face supercell model in Materials Studio, designing organic molecules M1 and M2 with asymmetric end groups of isocyano and sulfydryl, and carrying out structure optimization by utilizing VESTA and DFT; then, building a metal / molecule / metal junction device model in the ATK, calculating current and voltage characteristics of a device through an unbalanced green function in combination with a density functional theory, and extracting a maximum rectification ratio; further calculating electrostatic potential distribution of left and right interfaces, interface dipole and tunneling barrier width, and constructing comprehensive characteristic parameters; ; and finally, establishing an index incidence relation with T through fitting, and when the decision coefficient R is greater than or equal to 0.8, determining that T is an effective descriptor of the rectification ratio.

Description

Technical Field

[0001] This invention relates to the field of molecular electronic device design and performance prediction technology, and to a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface. Background Technology

[0002] In the field of molecular electronics, molecular diodes based on metal / molecule / metal structures have become a crucial technological path for miniaturizing and reducing the power consumption of electronic devices due to their ability to effectively suppress short-channel effects and tunneling current leakage common in traditional devices. Among these technologies, the rectification ratio, as a key performance parameter measuring the charge transport asymmetry of a device, is directly related to the application potential of molecular diodes through accurate evaluation and effective control. Therefore, developing methods that can efficiently predict and optimize the rectification ratio has become a key research focus and urgent need in this field.

[0003] Currently, the performance optimization of molecular diodes mainly relies on the design of asymmetric contact structures. However, two significant bottlenecks still exist in the actual research and development process: First, the combination space of metal electrode materials, organic molecular structures, and their interface geometries is extremely vast. If screening is carried out solely by experimental methods, it is not only time-consuming and labor-intensive, but the research and development cycle often lasts for months or even years, which seriously limits the rapid transformation and application of the technology. Second, existing theoretical models, such as the Schottky barrier theory and Fermi's golden rule, are significantly insufficient in describing the synergistic effect of multiple physical factors, such as interface electronic coupling, on the rectification ratio, resulting in a prediction accuracy that is usually below 80%, making it difficult to support the rational design of device structures and performance-oriented development.

[0004] Against this backdrop, developing a rectification ratio descriptor that combines universality and high accuracy has become a key approach to overcoming the aforementioned challenges. This descriptor can integrate multiple physicochemical characteristic parameters to establish a quantitative structure-property relationship between rectification ratio and device configuration, thereby improving prediction accuracy to over 90% and providing a theoretical basis for efficiently screening optimal structures. Simultaneously, it can "reduce the dimensionality" of a vast candidate system, significantly compressing the number of configurations requiring experimental verification from thousands to dozens, thus significantly reducing R&D costs. Furthermore, a unified descriptor system can help standardize technology development paths, propelling molecular diodes from traditional "trial-and-error" experience-based development to a new stage of theory-based "directed design," thereby accelerating their industrialization in cutting-edge fields such as flexible electronics and quantum information. To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, which solves the key technical problems of low accuracy in rectification ratio prediction and poor efficiency in optimal structure selection in the development of existing molecular diodes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, specifically including the following steps: S1: Import the metal into Materials Studio software, then open the optimized unit cell in Project Explorer and select Build, Surfaces, Cleave Surface and Cutout window; S2: Enter (111) in Milier Indices, set the vacuum layer thickness and number of layers and generate the layer. Then select Build, Supercell and set the expansion factor along the surface x-axis and y-axis, the crystallographic c-axis corresponding to the surface normal z-axis and set the expansion factor of the 4×4×1 super surface model in the super cell construction interface. S3: Construct the initial structure of a mono-diamyridyl-diphenyl molecule. An organic molecule with an isocyanate functional group attached to the left end group of the mono-diamyridyl-diphenyl molecule as the first anchoring group and a thiol functional group attached to the right end group as the second anchoring group is denoted as M1. An organic molecule with an isocyanate functional group attached to the left end group of the initial structure of the mono-diamyridyl-diphenyl molecule as the second anchoring group and an isocyanate functional group attached to the right end group as the second anchoring group is denoted as M2. S4: Import the surface structure file from S2 into VESTA, convert the file format to POSCAR structure file, and create an INCAR input file; S5: In the parameter settings of the INCAR file, the PBE functional is selected for the exchange correlation functional, and the vdWsurf van der Waals correction is introduced to accurately describe long-range interactions. The truncation of the electronic wave function can ensure the accuracy of electronic state calculation. The Brillouin zone sampling adopts the Monkhorst-Pack grid set to 16×16×16 to balance computational efficiency and result reliability. S6: After the input file configuration is completed, the DFT structure optimization calculation is executed. The entire process continues until the system energy reaches the convergence standard. Finally, the optimized metal surface and asymmetric molecules are output as the basic data for the subsequent construction of metal / molecule / metal interface models. S7: Select 3 layers of metal atoms as metal electrodes. Place the optimized organic molecules M1 / M2 vertically between the two metal electrodes. Place the left atom of organic molecules M1 / M2 in the hollow position on the electrode surface, while ensuring that the non-metallic right atom is placed on the metal electrode surface. S8: ATK software is used to build device models, and buffer layers are added to the left and right sides of the composition prepared in S7. Then, the atomic orbital linear coupling method is used to optimize the structure of the six different asymmetric metal / molecule / metal devices, and the descriptor of the rectification ratio of the asymmetric metal / organic / metal interface is obtained. S9: Transport calculations were performed on 6 different asymmetric metals / molecules / metal devices. PBE functionals were used in combination with a linear combination basis set of bi-ζ polarized atomic orbitals. A total of 261 k points were used in the transport direction, and a real space grid cutoff energy of 100 Ha was used to ensure the accuracy and convergence of the calculation. S10: The electron transport characteristics of six different asymmetric metal / molecule / metal devices were calculated using a non-equilibrium Green's function combined with density functional theory. Then, bias voltages of -1.5V and +1.5V were applied to obtain the current values ​​of each interface model under different bias voltages. These values ​​were then plotted as current-voltage curves and analyzed according to the formula RR=| / Calculate the rectification ratio RR under each bias voltage, and finally record the maximum rectification ratio within the bias voltage range as . ; S11: The electrostatic potential distribution between the left electrode and the molecular interface in the optimized device configuration is calculated using DFT, and the electrostatic potential difference between the upper and lower surfaces is denoted as... Calculate the dipole after molecular adsorption With the dipole before adsorption The difference is recorded as follows: The interfacial dipole at the metal / molecular interface on the left; ; S12: Calculate the electrostatic potential distribution at the interface between the right electrode and the molecule in the device configuration using the method in S11, and simultaneously obtain the electrostatic potential difference between the upper and lower surfaces, denoted as... Calculate the dipole before molecular adsorption With the dipole after adsorption Difference and record and the interfacial dipole at the right molecular / metal interface ; S13: Calculate the electrostatic potential distribution at the left metal / molecule interface in the optimized device configuration, obtain the distance across the interface potential of the S atom on the left side of the molecule, and denote it as the tunneling barrier width of the left interface. Calculate the electrostatic potential distribution at the right-side molecular / metal interface in the asymmetric structure, obtain the tunneling barrier width at the right-side interface, and denot it as... ; S14: According to the formula The values ​​of the characteristic parameter T for six different asymmetric systems were calculated, and the values ​​of the rectification ratio calculated in S2 were plotted with the characteristic parameter T as the x-axis. Plot a scatter plot on the ordinate and perform exponential fitting to obtain... Calculate the coefficient of determination of the fitted curve based on the quantitative correlation curve between T and T. ,when At a value of 0.8, the characteristic parameter T is determined as the descriptor for the rectification ratio of the asymmetric metal / organic / metal interface.

[0006] Preferably, in S1, the six metals Cu, Ag, Au, Pt, Rh, and Ir are imported into Materials Studio.

[0007] Preferably, in S2, the vacuum layer thickness is set to 15 Å and the number of layers is set to 4. In S2, the expansion factor is set to 4 along the surface x-axis and y-axis at the supercell construction interface, and the expansion factor is set to 1 along the crystallographic c-axis corresponding to the surface normal z-axis.

[0008] Preferably, the asymmetric organic structures M1 and M2 in S3 are geometrically optimized to eliminate structural stress and form molecular models with the lowest energy stability. The isocyanate functional group in S3 is -NC, and the mercapto functional group in S3 is -S.

[0009] Preferably, in S5, the cutoff energy of the electronic wavefunction, which introduces the vdWsurf van der Waals correction to accurately describe long-range interactions, is set to 450 eV.

[0010] Preferably, in S5, the Monkhorst-Pack grid is used and the energy convergence accuracy is set to 1× eV / atom, force convergence accuracy is 0.01eV / Å.

[0011] Preferably, the left-hand atoms of non-metallic M1 and M2 in S7 are placed in hollow positions on the electrode surface, while the right-hand atoms of the non-metallic M1 and M2 are placed at an optimized distance of 2.5 Å from the metal electrode surface.

[0012] Preferably, S8 uses ATK to add a device model so that three metal cells are added to the metal layers on both sides as buffer layers.

[0013] Preferably, in S14 The square of the tunneling barrier width at the right molecular / metal interface. This is the square of the tunneling barrier width at the metal / molecule interface on the left.

[0014] Preferably, in S14 For the interface dipole in S11 , For the interface dipole in S12 .

[0015] The technical effects and advantages of the descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface of the present invention are as follows: 1. This invention provides an efficient and reliable method for constructing descriptors that can accurately predict the rectification ratio of asymmetric metal / organic / metal interfaces, providing theoretical guidance and computational tools for the design and performance optimization of molecular electronic devices.

[0016] 2. This invention, by combining density functional theory and the non-equilibrium Green's function method, systematically calculates key physical quantities such as interface electrostatic potential distribution, interface dipole, and tunneling barrier width, forming a comprehensive characteristic parameter T, which significantly improves the accuracy and physical interpretability of rectification ratio prediction.

[0017] 3. This invention proposes a descriptor T and a maximum rectification ratio. There is a significant exponential correlation between them. A value of ≥0.8 indicates that the parameter can effectively reflect the impact of interface asymmetry on overall behavior and has strong universality and predictive ability.

[0018] 4. This invention adopts a standardized and systematic calculation process, covering the entire process from metal surface modeling, molecular structure optimization, interface construction to electronic transport property calculation, ensuring the reliability and repeatability of the calculation results.

[0019] 5. This invention is applicable to a variety of metals such as Cu, Ag, Au, Pt, Rh, Ir and different asymmetric molecular structures, and has wide material applicability, providing a feasible path for high-throughput screening of high-performance rectifying molecules.

[0020] 6. By introducing van der Waals correction and high-precision calculation parameters, this invention can accurately describe the long-range interactions and electronic structure at the interface, improving the fit between the interface model and the real system.

[0021] 7. This invention can not only be used to predict the rectification ratio, but also provide in-depth physical insights into the understanding of the charge injection, transport and rectification mechanisms at asymmetric interfaces, which will help promote the theoretical development and application innovation of molecular electronics and nanodevices. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the (111) crystal plane structure of six metals, Cu, Ag, Au, Pt, Rh, and Ir, based on the descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 2 This is a schematic diagram of the structure of an asymmetric organic molecule M1, which is a descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 3 This is a schematic diagram of the metal / molecule / metal interface structure of a descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 4 This is a schematic diagram of the metal / molecule / metal electronic transport calculation model of the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention; Figure 5 This is an IV curve of each interface model of the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention, under the applied bias voltage of -1.5 V to +1.5 V. Figure 6 This is a graph showing the rectification ratio curves of each interface model under a bias voltage of -1.5 V to +1.5 V, based on the descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 7 This is an electrostatic potential distribution diagram of the left electrode and molecular interface in the device configuration after optimization of the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention. Figure 8 This is a dipole diagram of the molecular dipole before and after adsorption, based on a descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 9 This is an electrostatic potential distribution diagram of the right electrode and molecular interface in the device configuration after optimization of the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention. Figure 10 This is a tunneling barrier width map of the metal / molecular interface on the left side of the descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 11 This is a tunneling barrier width map of the side molecule / metal interface in a descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 12 This is a quantitative correlation curve between the maximum rectification ratio and the characteristic parameter T of the M1 system in the descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention. Figure 13 This is a schematic diagram of the M2 molecular structure of a descriptor construction method for the rectification ratio of an asymmetric metal / organic / metal interface proposed in this invention; Figure 14 This is a graph showing the rectification ratio curves of each interface model of the M2 system under a bias voltage of -1.5 V to +1.5 V, based on the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention. Figure 15 This is a quantitative correlation curve between the maximum rectification ratio and the characteristic parameter T of the M2 system, which is based on the descriptor construction method for the rectification ratio of the asymmetric metal / organic / metal interface proposed in this invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0025] Example 1 This embodiment provides a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, and the specific implementation steps include: Experimental objective: A 4×4×1 supercell surface model was obtained.

[0026] Experimental steps: S1: Import the six metals Cu, Ag, Au, Pt, Rh, and Ir into Materials Studio software respectively; S2: Open the optimized unit cell in Project Explorer, right-click and select "Build" → "Surfaces" → "Cleave Surface", then open the aspect window; S3: Enter (111) in “Miller Indices”, set the vacuum layer thickness to 15 Å, the number of layers to 4, and click “Cleave” to generate; S4: Right-click and select “Build” → “Supercell”, then open the supercell construction window. Set the expansion factor along the surface x-axis and y-axis to 4, and set the expansion factor along the surface normal z-axis corresponding to the crystallographic c-axis to 1 to obtain a 4×4×1 supercell surface model.

[0027] Experimental results: refer to Figure 1The 4×4×1 supercell surface model shown was used to construct supercell surface models for six metals: Cu, Ag, Au, Pt, Rh, and Ir. The (111) crystal plane was selected as the interface contact surface, and a 15 Å vacuum layer was set to eliminate the influence of periodic boundaries on the interface simulation. This step provides a standardized electrode surface model for the subsequent construction of metal / organic interfaces, ensuring the comparability of interface structures of different metal systems. The mechanism is that the crystal orientation, number of layers, and vacuum layer setting of the metal surface directly affect the electronic structure of the interface and the stability of subsequent molecular adsorption, which is the structural basis for studying the interface charge transport and rectification behavior.

[0028] Example 2 This embodiment provides a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, and the specific implementation steps include: Experimental materials: Two asymmetric molecules are used as the second anchoring groups to form an asymmetric organic molecule.

[0029] Experimental objective: A stable molecular model of the lowest-energy asymmetric structure was constructed based on the dipyrimidinyl-diphenyl molecule.

[0030] Experimental steps: S1: Construct the initial structure of a mono-diamyridyl-diphenyl molecule; S2: An organic molecule with an isocyanate (-NC) functional group attached to the left end of the molecule as the first anchoring group and a mercapto (-S) functional group attached to the right end of the molecule as the second anchoring group, forming an asymmetric structure. This molecule is denoted as M1. S3: An organic molecule with a thiol (-S) functional group attached to the left end of the molecule as the first anchoring group and an isocyanate (-NC) functional group attached to the right end of the molecule as the second anchoring group, forming an asymmetric structure. This molecule is denoted as M2. S4: Perform geometric optimization on the initial structures of molecules M1 and M2 to eliminate structural stress and obtain a stable molecular model with the lowest energy.

[0031] Experimental results: refer to Figure 2 and Figure 15 The asymmetric organic molecules M1 and M2 are characterized by their structural features, which are connected to two different anchoring groups, an isocyanate (-NC) and a mercapto (-S), on their left and right ends, respectively, forming an asymmetric electronic structure. Through geometric optimization, a stable configuration with the lowest energy is obtained, providing a molecular structural basis for the subsequent construction of asymmetric metal / molecule / metal junctions. The mechanism is that the asymmetric end groups introduce interfacial dipole differences, and the coupling strength between the left and right sides and the metal is different, thereby generating asymmetric charge injection and transport behavior under bias voltage. This is a key molecular structural feature for achieving the rectification effect.

[0032] Example 3 This embodiment provides a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, and the specific implementation steps include: Experimental objective: Construct structures that do not contain asymmetric metals / molecules / metal devices.

[0033] Experimental steps: S1: Export the surface structure files of six metals, Cu, Ag, Au, Pt, Rh, and Ir, in sequence, import the metal surface structure files into VESTA software, convert the file format to generate a POSCAR structure file for DFT calculation, and create an INCAR input file; S2: In the parameter settings of the INCAR file, the PBE functional is selected for the exchange correlation functional, and it is imported. The van der Waals correction accurately describes long-range interactions. The cutoff energy of the electronic wavefunction is set to 450 eV to ensure the accuracy of electronic state calculations. Brillouin zone sampling uses a Monkhorst-Pack grid of 16×16×16 to balance computational efficiency and result reliability. For the convergence criterion, the energy convergence accuracy is set to 1× eV / atom and force convergence accuracy are set to 0.01 eV / Å; S3: After the input file configuration is completed, the DFT structure optimization calculation is executed. The entire process continues until the system energy reaches the convergence standard. Finally, the optimized metal surface and asymmetric molecules are output as the basic data for the subsequent construction of metal / molecule / metal interface models. S4: Select 3 layers of metal atoms as metal electrodes. Place the optimized organic molecules M1 / M2 vertically between the two metal electrodes. Place the left atom of organic molecule M1 / M2 in the hollow position on the electrode surface, while ensuring that the non-metal right atom is placed at the optimized position 2.5 Å away from the metal electrode surface. S5: The device model was built using ATK software. Three atomic layers were added to the left and right sides of the composition prepared in S5 as buffer layers. Then, the structure of the six different asymmetric metal / molecule / metal devices was optimized using the atomic orbital linear coupling method.

[0034] Experimental results: refer to Figure 3 This schematic diagram illustrates the position of asymmetric molecules between electrodes, showing the vertical arrangement of molecules between two metal electrodes. The left end group is located in a hollow position on the electrode surface, while the right end group maintains a distance of 2.5 Å, forming a clearly defined asymmetric interface structure. (Reference) Figure 4The structural optimization of asymmetric metal / organic / metal devices built using ATK demonstrates a stable device configuration optimized using the atomic orbital linear coupling method. Three buffer layers were added to each side to simulate the real electrode environment, providing a reliable interface model foundation for subsequent electron transport calculations. The mechanism involves how a reasonable interface geometry and molecular orientation directly influence orbital overlap and charge transport paths. Structural optimization ensures the physical rationality of the interface contact, a prerequisite for accurately predicting rectification behavior.

[0035] Example 4 This embodiment provides a method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, and the specific implementation steps include: Experimental objective: Calculate the electron transport properties, electrostatic potential distribution, and numerical values ​​of the characteristic parameter T of the asymmetric system, and determine the descriptor of the rectification ratio of the characteristic parameter at the asymmetric metal / organic / metal interface.

[0036] Experimental steps: S1: Transport calculations were performed on 6 different asymmetric metals / molecules / metal devices. PBE functionals were used in combination with a linear combination basis set of bi-ζ polarized atomic orbitals. A total of 261 k points were used in the transport direction, and a real space grid cutoff energy of 100 Ha was used to ensure the accuracy and convergence of the calculation. S2: The electron transport characteristics of six different asymmetric metal / molecule / metal devices were calculated using a non-equilibrium Green's function combined with density functional theory. Then, bias voltages of -1.5V and +1.5V were applied to obtain the current values ​​of each interface model under different bias voltages. These values ​​were then plotted as current-voltage curves and analyzed according to the formula RR=|I + / I - The rectification ratio RR is calculated for each bias voltage, and the maximum rectification ratio within the bias voltage range is denoted as RR. max ; S3: The electrostatic potential difference between the upper and lower surfaces is obtained by calculating the electrostatic potential distribution between the left electrode and the molecular interface in the optimized device configuration using DFT, denoted as... Calculate the dipole after molecular adsorption With the dipole before adsorption Difference record The interfacial dipole at the metal / molecular interface on the left ; S4: Calculate the electrostatic potential distribution at the interface between the right electrode and the molecule in the device configuration using the method in S3, and simultaneously obtain the electrostatic potential difference between the upper and lower surfaces, denoted as... Calculate the dipole before molecular adsorption With the dipole after adsorption Difference and record and the interfacial dipole at the right molecular / metal interface ; S5: Calculate the electrostatic potential distribution at the left metal / molecule interface in the optimized device configuration, and obtain the distance across the interface potential of the S atom on the left side of the molecule, denoted as the tunneling barrier width W of the left interface. left Calculate the electrostatic potential distribution at the right molecular / metal interface in the asymmetric structure, obtain the tunneling barrier width at the right interface and denote it as W. right ; S6: According to the formula The values ​​of the characteristic parameter T for six different asymmetric systems were calculated, and the values ​​of the rectification ratio RR calculated in S2 were plotted with the characteristic parameter T as the abscissa. max Plot a scatter plot on the ordinate and perform exponential fitting to obtain RR. max The quantitative correlation curve between T and the fitted curve is used to calculate the coefficient of determination R. 2 When R 2 At a value of 0.8, the characteristic parameter T is determined as the descriptor for the rectification ratio of the asymmetric metal / organic / metal interface.

[0037] Experimental results: refer to Figure 5 Current-voltage (I-V) curve, Figure 6 Rectifier ratio curve under bias voltage Figure 7 and Figure 9 Electrostatic potential distribution diagram of the left and right electrodes and molecular interface of the device configuration. Figure 8 Dipole diagram of dipole potential difference before and after adsorption Figure 10 and 11 Tunnel barrier width diagrams of the left and right interfaces Figure 12 and 15 A quantitative correlation curve between the maximum rectification ratio and the characteristic parameter T is presented. The current-voltage characteristics, interface electrostatic potential distribution, and interface dipole and tunneling barrier widths of six devices were systematically calculated using the non-equilibrium Green's function-density functional theory method. The characteristic parameter T was extracted as a descriptor, and fitting analysis revealed that the maximum rectification ratio (RR)... max The exponential relationship with T indicates that this parameter can effectively predict the rectification performance of asymmetric interfaces. The mechanism is that TT comprehensively reflects the difference between the barrier width of the left and right interfaces and the interface dipole. These two factors together determine the asymmetry of carrier injection, thereby controlling the magnitude of the rectification ratio.

[0038] Comparative Example 1 This embodiment provides a method for constructing a descriptor for the rectification ratio of a conventional asymmetric metal / organic / metal interface, and the specific implementation steps include: Experimental steps: S1: Based on literature reports or scientific research experience, subjectively select 1 to 3 common noble metals as electrode materials, and at the same time design and synthesize several small organic molecules with different asymmetric end groups according to chemical intuition or existing synthesis routes. S2: Using techniques such as self-assembled films, mechanically controlled split junctions, or scanning tunneling microscope probes, synthesized molecules are tentatively constructed between two metal electrodes to form multiple independent metal / molecule / metal junctions; S3: Using equipment such as a semiconductor parameter analyzer, perform electrical tests on the successfully constructed molecular junction, manually record the current value within a limited bias voltage range, and plot the IV curve. S4: Extract the maximum rectification ratio from the IV curve, and then attempt to measure or estimate a parameter considered critical, and compare it with... To establish simple linear or qualitative relationships; S5: Collected samples with a limited size The data is fitted with a simple mathematical model using a selected set of parameters; S6: Based on the above analysis of low correlation, qualitative or semi-quantitative empirical conclusions are drawn, such as that this type of molecule has a strong rectification effect on metal X and that the Y group may be beneficial to improving the rectification ratio.

[0039] Experimental results: Compared to subjective material selection based on literature and experience, which involves tedious and low-reproducibility experimental device preparation and measurement, qualitative or low-precision correlation analysis is ultimately performed based on a small number of samples and isolated parameters. The whole process is time-consuming and costly, and the conclusions have poor universality, making it impossible to efficiently and accurately predict and screen the performance of a large number of candidate systems.

[0040] Example 1 uses a 4×4×1 supercell surface model. By constructing a standardized metal (111) crystal plane and vacuum layer structure, it provides a basis for structural consistency and comparability for subsequent interface simulations. The mechanism is that the crystal plane orientation and vacuum layer setting directly regulate the electronic structure and molecular adsorption stability of the interface, which is a geometric prerequisite for studying asymmetric charge transport.

[0041] Example 2 uses M1 and M2 molecules designed with isocyanate / thiol asymmetric end groups, and obtains the stable configuration with the lowest energy through geometric optimization. The mechanism lies in the asymmetric end groups introducing interfacial dipole differences and coupling strength asymmetry, which is the molecular structural basis for achieving rectification behavior.

[0042] Example 3 employs a vertically aligned metal / molecule / metal three-layer structure model, combined with a linear coupling method of atomic orbitals for structural optimization. The mechanism lies in the fact that appropriate molecular orientation and interface distance directly affect orbital overlap and carrier injection paths, which are crucial steps in accurately simulating interface charge transport.

[0043] Example 4 employs a comprehensive characteristic parameter T construction and exponential fitting method to establish a quantitative correlation between the rectification ratio and physical quantities such as interfacial electrostatic potential, dipole, and tunneling barrier. The mechanism lies in the fact that the T parameter comprehensively characterizes the difference between the width of the left and right interfacial barriers and the dipole, reflecting the asymmetric physical nature of carrier injection.

[0044] Comparative Example 1 adopts the traditional R&D path based on experimental trial and error and simplified theoretical models. It relies on subjective experience to screen limited materials, on experimental preparation and testing with low repeatability to obtain data, and on qualitative or low-precision empirical correlation based only on a single or a few isolated parameters. This results in a time-consuming and costly process, and it is impossible to establish universal and quantitative structure-activity relationships, making it difficult to achieve accurate prediction and efficient screening of new systems.

[0045] Comparing the embodiments and comparative examples, Embodiment 1 achieves the best balance between standardization and comparability in structural modeling. Its ingenious use of crystal planes and vacuum layers enhances the physical rationality of the interface model, making it suitable for unified comparisons of multi-metal systems. While Embodiment 2 introduces asymmetry in its molecular structure design, it relies solely on geometric optimization without considering the dynamics of interfacial electronic coupling. Embodiment 3 employs a vertical interface configuration and buffer layer design, but it does not systematically examine the impact of molecular tilting or twisting on transport. Embodiment 4 uses a multi-physical quantity integrated descriptor T, but its universality still needs to be verified in a wider range of molecular systems. Therefore, this invention, through a multi-scale, multi-physical quantity collaborative descriptor construction method, significantly improves the accuracy and mechanistic interpretability of rectification ratio prediction, providing a reliable theoretical tool for the rational design of asymmetric molecular electronic devices.

[0046] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0047] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface, characterized in that, Specifically, the following steps are included: S1: Import the metal into Materials Studio software, then open the optimized unit cell in Project Explorer and select Build, Surfaces, Cleave Surface and Cutout window; S2: Enter (111) in Milier Indices, set the vacuum layer thickness and number of layers and generate the layer. Then select Build, Supercell and set the expansion factor along the surface x-axis and y-axis, the crystallographic c-axis corresponding to the surface normal z-axis and set the expansion factor of the 4×4×1 super surface model in the super cell construction interface. S3: Construct the initial structure of a mono-diamyridyl-diphenyl molecule. An organic molecule with an isocyanate functional group attached to the left end group of the mono-diamyridyl-diphenyl molecule as the first anchoring group and a thiol functional group attached to the right end group as the second anchoring group is denoted as M1. An organic molecule with an isocyanate functional group attached to the left end group of the initial structure of the mono-diamyridyl-diphenyl molecule as the second anchoring group and an isocyanate functional group attached to the right end group as the second anchoring group is denoted as M2. S4: Import the surface structure file from S2 into VESTA, convert the file format to POSCAR structure file, and create an INCAR input file; S5: In the parameter settings of the INCAR file, the PBE functional is selected for the exchange correlation functional, and the vdWsurf van der Waals correction is introduced to accurately describe long-range interactions. The truncation of the electronic wave function can ensure the accuracy of electronic state calculation. The Brillouin zone sampling adopts the Monkhorst-Pack grid set to 16×16×16 to balance computational efficiency and result reliability. S6: After the input file configuration is completed, the DFT structure optimization calculation is executed. The entire process continues until the system energy reaches the convergence standard. Finally, the optimized metal surface and asymmetric molecules are output as the basic data for the subsequent construction of metal / molecule / metal interface models. S7: Select 3 layers of metal atoms as metal electrodes. Place the optimized organic molecules M1 / M2 vertically between the two metal electrodes. Place the left atom of organic molecules M1 / M2 in the hollow position on the electrode surface, while ensuring that the non-metallic right atom is placed on the metal electrode surface. S8: ATK software is used to build device models, and buffer layers are added to the left and right sides of the composition prepared in S7. Then, the atomic orbital linear coupling method is used to optimize the structure of the six different asymmetric metal / molecule / metal devices, and the descriptor of the rectification ratio of the asymmetric metal / organic / metal interface is obtained. S9: Transport calculations were performed on 6 different asymmetric metals / molecules / metal devices. PBE functionals were used in combination with a linear combination basis set of bi-ζ polarized atomic orbitals. A total of 261 k points were used in the transport direction, and a real space grid cutoff energy of 100 Ha was used to ensure the accuracy and convergence of the calculation. S10: The electron transport characteristics of six different asymmetric metal / molecule / metal devices were calculated using a non-equilibrium Green's function combined with density functional theory. Then, bias voltages of -1.5V and +1.5V were applied to obtain the current values ​​of each interface model under different bias voltages. These values ​​were then plotted as current-voltage curves and analyzed according to the formula RR=| / Calculate the rectification ratio RR under each bias voltage, and finally record the maximum rectification ratio within the bias voltage range as . ; S11: The electrostatic potential distribution between the left electrode and the molecular interface in the optimized device configuration is calculated using DFT, and the electrostatic potential difference between the upper and lower surfaces is denoted as... Calculate the dipole after molecular adsorption With the dipole before adsorption Difference record The interfacial dipole at the metal / molecular interface on the left ; S12: Calculate the electrostatic potential distribution at the interface between the right electrode and the molecule in the device configuration using the method in S11, and simultaneously obtain the electrostatic potential difference between the upper and lower surfaces, denoted as... Calculate the dipole before molecular adsorption With the dipole after adsorption Difference and record and the interfacial dipole at the right molecular / metal interface ; S13: Calculate the electrostatic potential distribution at the left metal / molecule interface in the optimized device configuration, obtain the distance across the interface potential of the S atom on the left side of the molecule, and denote it as the tunneling barrier width of the left interface. Calculate the electrostatic potential distribution at the right-side molecular / metal interface in the asymmetric structure, obtain the tunneling barrier width at the right-side interface, and denot it as... ; S14: According to the formula The values ​​of the characteristic parameter T for six different asymmetric systems were calculated, and the values ​​of the rectification ratio calculated in S2 were plotted with the characteristic parameter T as the x-axis. Plot a scatter plot on the ordinate and perform exponential fitting to obtain... Calculate the coefficient of determination of the fitted curve based on the quantitative correlation curve between T and T. ,when At a value of 0.8, the characteristic parameter T is determined as the descriptor for the rectification ratio of the asymmetric metal / organic / metal interface.

2. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, Import the six metals Cu, Ag, Au, Pt, Rh, and Ir into Materials Studio in S1.

3. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, In S2, the vacuum layer thickness is set to 15 Å and the number of layers is set to 4. In S2, the expansion factor is set to 4 along the surface x-axis and y-axis at the supercell construction interface, and the expansion factor is set to 1 along the crystallographic c-axis corresponding to the surface normal z-axis.

4. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, In S3, the asymmetric organic structures M1 and M2 are geometrically optimized to eliminate structural stress and form molecular models with the lowest energy stability. The isocyanate functional group in S3 is -NC, and the mercapto functional group in S3 is -S.

5. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, In S5, the cutoff energy of the electronic wavefunction is set to 450 eV to introduce the vdWsurf van der Waals correction to accurately describe long-range interactions.

6. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, In S5, the Monkhorst-Pack grid is used and the energy convergence accuracy is set to 1× eV / atom, force convergence accuracy is 0.01eV / Å.

7. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, The atoms on the left side of S7 nonmetals M1 and M2 are placed in hollow positions on the electrode surface, while the atoms on the right side of the nonmetal are placed at an optimized position 2.5 Å away from the metal electrode surface.

8. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, S8 uses ATK to add a device model, adding three metal cells to each of the two metal layers as buffer layers.

9. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, S14 The square of the tunneling barrier width at the right molecular / metal interface. This is the square of the tunneling barrier width at the metal / molecule interface on the left.

10. The method for constructing a descriptor for the rectification ratio of an asymmetric metal / organic / metal interface as described in claim 1, characterized in that, S14 For the interface dipole in S11 , For the interface dipole in S12 .

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