Method and system for obtaining charge injection barrier at metal / polymer interface

Abstract

The present invention discloses a method and system for obtaining the charge injection barrier at a metal / polymer interface. The method comprises the following steps: obtaining a metal / polymer interface model based on first principles, according to the metal / polymer interface for which the charge injection barrier is to be obtained; obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity, and ionization energy based on first principles, the polymer molecular chain structure model, and the metal / polymer interface model; and calculating the charge injection barrier at the metal / polymer interface based on the obtained physical quantities and the definition of the metal / insulating material charge injection barrier in energy band theory. This method solves technical problems in the prior art, such as the significant influence of external interference on the results; the difficulty in standardizing the experimental process for different polymer materials and metal electrode materials; and the lack of a complete theoretical basis for the method.

Description

Technical Field

[0001] The present invention belongs to the technical field of power insulation prediction, relates to the prediction of physical and chemical properties of composite interfaces, and particularly to a method and system for obtaining a charge injection barrier at a metal / polymer interface. Background Art

[0002] In recent years, polymer insulation materials have been widely used in various high-voltage power equipment, such as power cables and power capacitors, due to their excellent insulation properties. During the operation of such power equipment, the phenomenon of electrode injection, which occurs at the metal conductor / polymer interface, has attracted widespread attention. Specifically, the physical process of electrons and holes being injected from the metal conductor into the polymer when polymer insulation materials are subjected to long-term high-field DC operation is called electrode injection.

[0003] The above-mentioned electrode injection phenomenon will lead to the accumulation of space charge inside the polymer, causing internal electric field distortion, which may cause the occurrence of adverse phenomena such as electrical treeing and partial discharge, and even eventually cause the insulating material to lose its insulating properties, thereby posing a major threat to the safety of power equipment.

[0004] The charge (electron and hole) injection barrier at the metal / polymer interface is the most critical physical parameter affecting the electrode injection phenomenon. It is jointly affected by the metal type, polymer type and interface structure. Accurately determining the size of the charge injection barrier at the polymer / metal interface can effectively help people understand, predict and avoid the charge injection phenomenon in power equipment.

[0005] Currently, the primary method for determining the charge injection barrier at metal / polymer interfaces relies on indirect experimental measurement. Specifically, a DC bias electric field is applied to the polymer / metal interface, and the conductance current is measured. Based on the electric field strength-current relationship, the charge injection barrier is inferred using the Schottky injection equation. However, due to the relatively small magnitude of the conductance current, this experimental measurement method is significantly susceptible to external interference. Furthermore, the experimental process is difficult to standardize for different polymer materials and metal electrode materials. Furthermore, it remains uncertain whether the Schottky injection equation can be used to describe the charge injection process at interfaces across different metal / polymer materials, and this method lacks a comprehensive theoretical foundation. Summary of the Invention

[0006] The present invention aims to provide a method and system for determining the charge injection barrier at a metal / polymer interface to address one or more of the aforementioned technical issues. The present invention provides a first-principles approach to determining the charge injection barrier at a metal / polymer interface, resolving existing technical issues such as the significant influence of external interference on the results obtained; the difficulty in standardizing the experimental process for different polymer materials and metal electrode materials; and the lack of a comprehensive theoretical foundation for the method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for obtaining a charge injection barrier at a metal / polymer interface, comprising the following steps:

[0009] Obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface at which the charge injection barrier is to be obtained; wherein the metal / polymer interface model includes a polymer molecular chain structure model and a metal surface structure model, and the polymer molecular chain structure model is embedded in the metal surface structure model;

[0010] Based on first principles, the polymer molecular chain structure model and the metal / polymer interface model, the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy are obtained;

[0011] Based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, the charge injection barrier at the metal / polymer interface is calculated according to the definition of the metal / insulating material charge injection barrier in band theory.

[0012] A further improvement of the present invention is that the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained specifically includes:

[0013] According to the metal / polymer interface where the charge injection barrier is to be obtained, an initial polymer molecular chain structure model with a degree of polymerization between 2 and n is established according to the polymer molecular chemical formula; the initial polymer molecular chain structure model is optimized by first principles to obtain a polymer molecular chain structure model; the metal unit cell is cut to establish a 2-m layer metal structure, and a vacuum layer with a length greater than the optimized polymer molecule length is added to form a metal surface structure model;

[0014] The polymer molecular chain structure model is placed in the vacuum layer of the metal surface structure model to obtain a metal / polymer interface model; wherein the placement is carried out in such a way that the skeleton of the polymer molecular chain forms an angle of 0° to 90° with the metal surface.

[0015] A further improvement of the present invention is that in the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained, the software tool used is Materials Studio software.

[0016] A further improvement of the present invention is that the step of obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on the first principles, the polymer molecular chain structure model and the metal / polymer interface model specifically includes:

[0017] The pw.x module of Quantum Espresso, a first-principles calculation software based on density functional theory, was used to perform structural optimization and single-point energy calculations on the metal / polymer interface model, obtaining the wave function data and Fermi level of the thermodynamically stable metal / polymer interface model. The obtained wave function data of the metal / polymer interface model were post-processed using the pp.x module of Quantum Espresso, a first-principles calculation software, to obtain electrostatic potential data in a three-dimensional grid format. The electrostatic potential data were averaged along the direction perpendicular to the interface to obtain the plane-averaged electrostatic potential distribution of the metal / polymer interface model. Based on the plane-averaged electrostatic potential distribution of the metal / polymer interface model, the metal surface work function and vacuum energy level difference were calculated. The vacuum energy level difference is the difference between the vacuum energy levels on the metal side and the polymer side. The metal surface work function is the difference between the vacuum energy level on the metal side and the Fermi level.

[0018] The calculation expression of polymer electron affinity and ionization energy is:

[0019] EA=E 中 -E 负 ;

[0020] IP=E 正 -E 中 ;

[0021] Where EA is the polymer electron affinity; IP is the polymer ionization energy; E 中 、E 负 and E 正 They are the energies when the polymer molecular chain structure model is in a neutral state, with a negative charge, and with a positive charge, respectively.

[0022] A further improvement of the present invention is that, in the step of calculating the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in energy band theory,

[0023] The charge injection barrier includes electron and hole injection barriers; the calculation expressions of the electron and hole injection barriers are respectively,

[0024]

[0025]

[0026] Where, φ e is the electron injection barrier; h is the hole injection barrier; m is the metal work function; is the vacuum energy level difference; EA is the polymer electron affinity; IP is the polymer ionization energy.

[0027] The present invention provides a system for acquiring a charge injection barrier at a metal / polymer interface, comprising:

[0028] a model acquisition module for acquiring a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be acquired; wherein the metal / polymer interface model includes a polymer molecular chain structure model and a metal surface structure model, and the polymer molecular chain structure model is embedded in the metal surface structure model;

[0029] A physical quantity acquisition module, for obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on first principles, the polymer molecular chain structure model and the metal / polymer interface model;

[0030] The charge injection barrier acquisition module is used to calculate the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in the band theory.

[0031] A further improvement of the present invention is that the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained specifically includes:

[0032] According to the metal / polymer interface where the charge injection barrier is to be obtained, an initial polymer molecular chain structure model with a degree of polymerization between 2 and n is established according to the polymer molecular chemical formula; the initial polymer molecular chain structure model is optimized by first principles to obtain a polymer molecular chain structure model; the metal unit cell is cut to establish a 2-m layer metal structure, and a vacuum layer with a length greater than the optimized polymer molecule length is added to form a metal surface structure model;

[0033] The polymer molecular chain structure model is placed in the vacuum layer of the metal surface structure model to obtain a metal / polymer interface model; wherein the placement is carried out in such a way that the skeleton of the polymer molecular chain forms an angle of 0° to 90° with the metal surface.

[0034] A further improvement of the present invention is that in the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained, the software tool used is Materials Studio software.

[0035] A further improvement of the present invention is that the step of obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on the first principles, the polymer molecular chain structure model and the metal / polymer interface model specifically includes:

[0036] The pw.x module of Quantum Espresso, a first-principles calculation software based on density functional theory, was used to perform structural optimization and single-point energy calculations on the metal / polymer interface model, obtaining the wave function data and Fermi level of the thermodynamically stable metal / polymer interface model. The obtained wave function data of the metal / polymer interface model were post-processed using the pp.x module of Quantum Espresso, a first-principles calculation software, to obtain electrostatic potential data in a three-dimensional grid format. The electrostatic potential data were averaged along the direction perpendicular to the interface to obtain the plane-averaged electrostatic potential distribution of the metal / polymer interface model. Based on the plane-averaged electrostatic potential distribution of the metal / polymer interface model, the metal surface work function and vacuum energy level difference were calculated. The vacuum energy level difference is the difference between the vacuum energy levels on the metal side and the polymer side. The metal surface work function is the difference between the vacuum energy level on the metal side and the Fermi level.

[0037] The calculation expression of polymer electron affinity and ionization energy is:

[0038] EA=E 中 -E 负 ;

[0039] IP=E 正 -E 中 ;

[0040] Where EA is the polymer electron affinity; IP is the polymer ionization energy; E 中 、E 负 and E 正 They are the energies when the polymer molecular chain structure model is in a neutral state, with a negative charge, and with a positive charge, respectively.

[0041] A further improvement of the present invention is that, in the step of calculating the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in energy band theory,

[0042] The charge injection barrier includes electron and hole injection barriers; the calculation expressions of the electron and hole injection barriers are respectively,

[0043]

[0044]

[0045] Where, φ e is the electron injection barrier; h is the hole injection barrier; m is the metal work function; is the vacuum energy level difference; EA is the polymer electron affinity; IP is the polymer ionization energy.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] In this invention, in order to address the defects and shortcomings of the existing methods for actually measuring the charge injection barrier at the metal / polymer interface, a method for obtaining the charge injection barrier at the metal / polymer interface is specifically disclosed. The technical solution of the present invention realizes the acquisition of the charge injection barrier at the metal / polymer interface based on first principles, and has the following significant improvements compared to the above-mentioned existing measurement methods:

[0048] 1) All calculations are based on first-principles theory, do not rely on experimental results, and are not affected by any external conditions; no experimental materials need to be prepared, and the cost is low and pollution-free;

[0049] 2) A standardized modeling and calculation process is proposed, which does not change with changes in metal or polymer types, making the entire calculation process convenient and fast;

[0050] 3) The calculation is performed directly based on the theoretical definition of the charge injection barrier in the energy band theory, which has a solid theoretical basis. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1This is a schematic flow chart of a method for obtaining a charge injection barrier at a metal / polymer interface disclosed in an embodiment of the present invention;

[0053] Figure 2 : is a schematic diagram of the structure of the aluminum / polytetrafluoroethylene interface established in an embodiment of the present invention; wherein, Figure 2 (a) is a top view. Figure 2 Middle (b) is a side view schematic diagram;

[0054] Figure 3 Schematic diagram of the plane average electrostatic potential distribution of the aluminum / polytetrafluoroethylene interface in an embodiment of the present invention;

[0055] Figure 4 This is a schematic diagram of a system for acquiring a charge injection barrier at a metal / polymer interface disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0057] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0058] The present invention is described in further detail below with reference to the accompanying drawings:

[0059] Example 1

[0060] See also Figure 1 The present invention discloses a method for obtaining the charge injection barrier at a metal / polymer interface based on first-principles calculations. The method has a solid theoretical foundation, accurate results, and a unified operational process. The method comprises the following steps:

[0061] First, the polymer molecular chain structure model, metal surface structure model and metal / polymer interface model were constructed;

[0062] Next, the plane-averaged electrostatic potential distribution of the metal / polymer interface model was calculated based on first-principles calculations. The metal work function and vacuum level shift were then calculated based on the plane-averaged electrostatic potential distribution curve. Furthermore, the polymer's electron affinity and ionization potential were calculated based on the polymer molecular chain structure model.

[0063] Finally, the charge injection barrier size at the metal / polymer interface is obtained based on the above physical quantities.

[0064] Example 2

[0065] An embodiment of the present invention provides a method for obtaining a charge injection barrier at a metal / polymer interface, which is a method for calculating the charge injection barrier at a metal / polymer interface based on first principles, and specifically includes the following steps:

[0066] Step S1, establishing a polymer molecular chain structure model, a metal surface structure model, and a metal / polymer interface model based on first principles;

[0067] For further specific example, step S1 specifically includes the following steps:

[0068] Step S1.1: Based on the polymer molecular formula, use Materials Studio software to establish a polymer molecular chain structure model with a degree of polymerization between 2 and n, and perform first-principles optimization calculations on the structure to obtain a stable configuration;

[0069] Step S1.2: Use Materials Studio software to slice the metal unit cell to create a 2-m-layer metal structure, and add a vacuum layer whose length is greater than the optimized polymer molecule length to form a metal surface structure model.

[0070] In step S1.3, using Materials Studio software, the polymer molecular chain structure model obtained in step S1.1 is inserted into the vacuum layer of the metal surface structure model obtained in step S1.2. The insertion method is to make the skeleton of the polymer molecular chain form an angle of 0 to 90 degrees with the metal surface to form a metal / polymer interface model.

[0071] Step S2, calculating the plane average electrostatic potential distribution of the metal / polymer interface model based on first principles, and obtaining the metal surface work function and vacuum energy level difference;

[0072] For further explanation, step S2 specifically includes the following steps:

[0073] Step S2.1, using the pw.x module of Quantum Espresso, a first-principles calculation software based on density functional theory, to perform structural optimization and single-point energy calculation on the metal / polymer interface model obtained in step S1, thereby obtaining a wave function file and Fermi level of the thermodynamically stable metal / polymer interface model;

[0074] Step S2.2, using the pp.x module of the first-principles calculation software Quantum Espresso, post-processing the wave function data of the metal / polymer interface model obtained in step S2.1 to obtain electrostatic potential data in a three-dimensional grid format; averaging the electrostatic potential data along a direction perpendicular to the interface (typically the Z-axis of the supercell) to obtain a planar average electrostatic potential distribution of the metal / polymer interface model;

[0075] Step S2.3, calculate the metal surface work function and vacuum energy level difference based on the plane average electrostatic potential distribution of the metal / polymer interface model; wherein the vacuum energy level difference is the difference between the vacuum energy levels (i.e., the magnitude of the electrostatic potential) on the metal side and the polymer side; the metal surface work function is the difference between the vacuum energy level on the metal side and the Fermi level.

[0076] Step S3, calculating the polymer electron affinity and ionization energy based on the polymer molecular chain structure model obtained in step S1.1;

[0077] For further explanation, step S3 specifically includes the following steps:

[0078] Based on first-principles calculations, the total energy of the system is obtained when the polymer molecular chain structure model is in a neutral state (no charge), with a negative charge, and with a positive charge.

[0079] The calculation formulas for polymer electron affinity and ionization energy are as follows:

[0080] EA=E 中 -E 负 ;

[0081] IP=E 正 -E 中 ;

[0082] Where EA is the polymer electron affinity; IP is the polymer ionization energy; E 中 、E 负 and E 正 They are the energies when the polymer molecular chain structure model is in a neutral state, with a negative charge, and with a positive charge, respectively.

[0083] Step S4, obtaining the charge injection barrier size at the metal / polymer interface; the specific steps include:

[0084] Based on the metal surface work function and vacuum energy level difference obtained in step S2, and the polymer electron affinity and ionization energy obtained in step S3, the metal / polymer interface charge (electron and hole) injection barrier is calculated according to the definition of the metal / insulating material charge injection barrier in energy band theory;

[0085] The calculation formula for the electron and hole injection barriers is:

[0086]

[0087]

[0088] Where, φ e is the electron injection barrier; h is the hole injection barrier; m is the metal work function; is the vacuum energy level difference.

[0089] Example 3

[0090] In the embodiment of the present invention, for aluminum conductors and polytetrafluoroethylene polymer insulation commonly used in power systems, the steps for calculating the charge injection barrier at the aluminum / polytetrafluoroethylene interface using the technical solution of the present invention are as follows:

[0091] Materials Studio software was used to establish a polytetrafluoroethylene molecular chain structure model with a degree of polymerization of 4, and the structure was optimized by first-principles calculation to obtain a stable configuration. The aluminum metal unit cell was cut to establish a 4-layer metal structure, and a 1.5nm vacuum layer was added to form a metal surface structure model. In the metal surface structure model, the skeleton of the polytetrafluoroethylene molecular chain was made to form a 0-degree angle with the metal surface, forming the following: Figure 2 Model of the aluminum / PTFE interface shown;

[0092] The plane average electrostatic potential distribution of the aluminum / polytetrafluoroethylene interface model was calculated based on the first principles. The results are as follows Figure 3 As shown; and based on the electrostatic potential calculation results, the surface work function of aluminum and the size of the vacuum energy level difference are obtained.

[0093] The total energy of the system when the polytetrafluoroethylene molecular chain structure model is in a neutral state (no charge), with a negative charge, and with a positive charge is further obtained. The electron affinity and ionization energy of polytetrafluoroethylene are also obtained.

[0094] Finally, according to the definition of electron and hole injection barriers, the calculated value of the charge injection barrier at the aluminum / polytetrafluoroethylene interface was obtained.

[0095] The principle of the technical solution of the embodiment of the present invention is explained. The traditional experimental method for testing the charge injection barrier at the metal / polymer interface is greatly affected by external interference factors; the experimental process is difficult to unify for different polymer materials and metal electrode materials; and the testing method is an indirect measurement and lacks a complete theoretical basis. To solve the above problems, the present invention proposes a method for calculating the charge injection barrier at the metal / polymer interface based on first principles. The method of the present invention is entirely based on first principles theoretical calculations and does not rely on experimental results. Therefore, it is not affected by any external interference factors; a standardized modeling and calculation process is proposed, and the process does not change due to changes in the type of metal or polymer; in addition, the calculation is directly based on the theoretical definition of the charge injection barrier in band theory, which has a solid theoretical basis.

[0096] Exemplary applications of the embodiments of the present invention are as follows: obtaining the accurate size of the charge injection barrier at the polymer / metal interface has important scientific significance and engineering value; under a strong electric field, the current density injected by the metal electrode / polymer insulation interface electrode in power equipment is usually evaluated based on the Richardson-Schottky equation or the Fowler-Nordheim equation, and the most important parameter in the above equation is the charge injection barrier at the polymer / metal interface; only by accurately obtaining the size of the charge injection barrier can the relationship between the electric field strength and the current density injected by the electrode be correctly judged; this has important reference value for verifying the electric field strength that the insulation of power equipment withstands, selecting suitable insulating materials, and designing the shape and size of insulation in power equipment.

[0097] The following are device embodiments of the present invention, which can be used to implement the method embodiments of the present invention. For details not disclosed in the device embodiments, please refer to the method embodiments of the present invention.

[0098] See also Figure 4 In yet another embodiment of the present invention, a system for acquiring a charge injection barrier at a metal / polymer interface is provided, comprising:

[0099] a model acquisition module for acquiring a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be acquired; wherein the metal / polymer interface model includes a polymer molecular chain structure model and a metal surface structure model, and the polymer molecular chain structure model is embedded in the metal surface structure model;

[0100] A physical quantity acquisition module, for obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on first principles, the polymer molecular chain structure model and the metal / polymer interface model;

[0101] The charge injection barrier acquisition module is used to calculate the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in the band theory.

[0102] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0103] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0104] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0105] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for obtaining a charge injection barrier at a metal / polymer interface, characterized in that: The following steps are involved: Obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface at which the charge injection barrier is to be obtained; wherein the metal / polymer interface model includes a polymer molecular chain structure model and a metal surface structure model, and the polymer molecular chain structure model is embedded in the metal surface structure model; Based on first principles, the polymer molecular chain structure model and the metal / polymer interface model, the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy are obtained; Based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, the charge injection barrier at the metal / polymer interface is calculated according to the definition of the charge injection barrier for metal / insulating materials in energy band theory; in, The step of obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on the first principles, the polymer molecular chain structure model and the metal / polymer interface model specifically includes: The pw.x module of Quantum Espresso, a first-principles calculation software based on density functional theory, was used to perform structural optimization and single-point energy calculations on the metal / polymer interface model, obtaining the wave function data and Fermi level of the thermodynamically stable metal / polymer interface model. The obtained wave function data of the metal / polymer interface model were post-processed using the pp.x module of Quantum Espresso, a first-principles calculation software, to obtain electrostatic potential data in a three-dimensional grid format. The electrostatic potential data were averaged along the direction perpendicular to the interface to obtain the plane-averaged electrostatic potential distribution of the metal / polymer interface model. Based on the plane-averaged electrostatic potential distribution of the metal / polymer interface model, the metal surface work function and vacuum energy level difference were calculated. The vacuum energy level difference is the difference between the vacuum energy levels on the metal side and the polymer side. The metal surface work function is the difference between the vacuum energy level on the metal side and the Fermi level. The calculation expression of polymer electron affinity and ionization energy is: YES=Yes 中 -Yes 负 ; IP=E 正 -E 中 ; Where EA is the polymer electron affinity; IP is the polymer ionization energy; E 中 、E 负 and E 正 They are the energies when the polymer molecular chain structure model is in a neutral state, with a negative charge, and with a positive charge, respectively.

2. The method for obtaining a charge injection barrier at a metal / polymer interface according to claim 1, characterized in that: The step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained specifically includes: According to the metal / polymer interface where the charge injection barrier is to be obtained, an initial polymer molecular chain structure model with a degree of polymerization between 2 and n is established according to the polymer molecular chemical formula; the initial polymer molecular chain structure model is optimized by first principles to obtain a polymer molecular chain structure model; the metal unit cell is cut to establish a 2-m layer metal structure, and a vacuum layer with a length greater than the optimized polymer molecule length is added to form a metal surface structure model; The polymer molecular chain structure model is placed in the vacuum layer of the metal surface structure model to obtain a metal / polymer interface model; wherein the placement is carried out in such a way that the skeleton of the polymer molecular chain forms an angle of 0° to 90° with the metal surface.

3. The method for obtaining a charge injection barrier at a metal / polymer interface according to claim 2, characterized in that: In the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained, the software tool used is Materials Studio software.

4. The method for obtaining a charge injection barrier at a metal / polymer interface according to claim 1, characterized in that: In the step of calculating the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in energy band theory, The charge injection barrier includes electron and hole injection barriers; the calculation expressions of the electron and hole injection barriers are respectively, Where, φ e is the electron injection barrier; h is the hole injection barrier; m is the metal work function; is the vacuum energy level difference; EA is the polymer electron affinity; IP is the polymer ionization energy.

5. A system for obtaining a charge injection barrier at a metal / polymer interface, characterized in that: include: a model acquisition module for acquiring a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be acquired; wherein the metal / polymer interface model includes a polymer molecular chain structure model and a metal surface structure model, and the polymer molecular chain structure model is embedded in the metal surface structure model; A physical quantity acquisition module, for obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on first principles, the polymer molecular chain structure model and the metal / polymer interface model; The charge injection barrier acquisition module is used to calculate the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy according to the definition of the metal / insulating material charge injection barrier in the band theory; The step of obtaining the metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy based on the first principles, the polymer molecular chain structure model and the metal / polymer interface model specifically includes: The pw.x module of Quantum Espresso, a first-principles calculation software based on density functional theory, was used to perform structural optimization and single-point energy calculations on the metal / polymer interface model, obtaining the wave function data and Fermi level of the thermodynamically stable metal / polymer interface model. The obtained wave function data of the metal / polymer interface model were post-processed using the pp.x module of Quantum Espresso, a first-principles calculation software, to obtain electrostatic potential data in a three-dimensional grid format. The electrostatic potential data were averaged along the direction perpendicular to the interface to obtain the plane-averaged electrostatic potential distribution of the metal / polymer interface model. Based on the plane-averaged electrostatic potential distribution of the metal / polymer interface model, the metal surface work function and vacuum energy level difference were calculated. The vacuum energy level difference is the difference between the vacuum energy levels on the metal side and the polymer side. The metal surface work function is the difference between the vacuum energy level on the metal side and the Fermi level. The calculation expression of polymer electron affinity and ionization energy is: YES=Yes 中 -Yes 负 ; IP=E 正 -E 中 ; Where EA is the polymer electron affinity; IP is the polymer ionization energy; E 中 、E 负 and E 正 They are the energies when the polymer molecular chain structure model is in a neutral state, with a negative charge, and with a positive charge, respectively.

6. The system for obtaining a charge injection barrier at a metal / polymer interface according to claim 5, characterized in that: The step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained specifically includes: According to the metal / polymer interface where the charge injection barrier is to be obtained, an initial polymer molecular chain structure model with a degree of polymerization between 2 and n is established according to the polymer molecular chemical formula; the initial polymer molecular chain structure model is optimized by first principles to obtain a polymer molecular chain structure model; the metal unit cell is cut to establish a 2-m layer metal structure, and a vacuum layer with a length greater than the optimized polymer molecule length is added to form a metal surface structure model; The polymer molecular chain structure model is placed in the vacuum layer of the metal surface structure model to obtain a metal / polymer interface model; wherein the placement is carried out in such a way that the skeleton of the polymer molecular chain forms an angle of 0° to 90° with the metal surface.

7. The system for obtaining a charge injection barrier at a metal / polymer interface according to claim 6, characterized in that: In the step of obtaining a metal / polymer interface model based on first principles according to the metal / polymer interface of the charge injection barrier to be obtained, the software tool used is Materials Studio software.

8. The system for obtaining a charge injection barrier at a metal / polymer interface according to claim 5, characterized in that: In the step of calculating the charge injection barrier at the metal / polymer interface based on the obtained metal surface work function, vacuum energy level difference, polymer electron affinity and ionization energy, according to the definition of the metal / insulating material charge injection barrier in energy band theory, The charge injection barrier includes electron and hole injection barriers; the calculation expressions of the electron and hole injection barriers are respectively, Where, φ e is the electron injection barrier; h is the hole injection barrier; m is the metal work function; is the vacuum energy level difference; EA is the polymer electron affinity; IP is the polymer ionization energy.

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