Electrochemical in-situ polymerized ito solar cell electrode and method of making the same

Abstract

The present application relates to ITO flexible electrode in the field of application of flexible solar cell, specifically relates to electrochemical in-situ polymerization ITO solar cell electrode and its preparation method. In order to solve the problem of brittleness, conductivity and transparency of flexible electrode, the present application polymerizes polymer on ITO electrode by electrochemical in-situ polymerization, and prepares ITO polymer electrode which integrates the advantages of thermal stability, high conductivity, transparency and flexibility. The electrochemical in-situ polymerization ITO solar cell electrode provided by the present application comprises a transparent flexible bottom backing layer, an ITO layer, the ITO layer covers the transparent flexible bottom backing layer, and further comprises a polymer polymer in the non-crystalline part of the ITO layer. The product provided by the present application provides the flexible organic solar cell industry, and provides the electrode which simultaneously integrates the advantages of high light transmittance, high conductivity and flexibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the application of ITO flexible electrode in the field of flexible solar cell, in particular to an electrochemical in-situ polymerized ITO solar cell electrode and a preparation method thereof. BACKGROUND

[0002] With the rapid growth of China's economy, energy demand is rising year by year, and energy imports are also increasing year by year, while China's energy is mainly coal-based, which has brought energy security and environmental problems. From the aspects of energy security, pollution reduction, ecological environment improvement and world resources, developing and utilizing safe, reliable and clean new energy and renewable energy-solar energy has become a hot topic of world attention. At present, due to the problems of high cost, complex production process and low absorption coefficient, the traditional single crystal silicon, polycrystalline silicon and amorphous silicon solar cells are limited in further development and application. Because the molecular structure of organic solar cells can be designed and synthesized by itself, the material selection is large, easy to process, light in quality, low in cost, and can be prepared into large-area flexible or semi-transparent devices, so it has attracted people's high attention. With the development of various new active layer materials and device structure improvement, in recent years, the development of new type of organic solar cells with high efficiency, low cost and non-toxicity has been relatively mature, but the flexible commercial application of organic solar cells is still a challenge.

[0003] Flexible organic solar cells integrate the advantages of flexibility, dip-coating, large-area screen printing, inkjet printing and large-area roll-to-roll processing, and have great application prospects in many fields such as life and medical care, health monitoring, Internet of Things, electric vehicles, etc. Unlike traditional rigid and bendable flexible devices, stretchable flexible organic solar cells can realize conformal contact with human skin and meet the deformation requirements of various tissue parts, and have gradually become a research hotspot in the field of flexible electronics in recent years. Developing ultra-thin stretchable transparent electrodes with excellent performance is a key link to realize their application in new wearable electronic devices.

[0004] Flexible organic solar cells are organic solar cells prepared on electrodes with certain flexibility. For flexible organic solar cells, electrodes with flexibility, high conductivity and high light transmittance are one of the foundations. Traditional organic solar cells are prepared based on indium tin oxide (ITO) glass electrodes with the advantages of non-toxicity, low cost, transparency, high conductivity and thermal stability, etc. At present, the photoelectric conversion efficiency (PCE) of single heterojunction organic solar cells prepared on rigid ITO glass is more than 18%. Although these high-efficiency organic solar cells have achieved the requirements of inkjet printing and large-area preparation, etc., the ITO glass electrodes have mechanical brittleness and other characteristics, which limit the demand for large-area flexible commercial application of organic solar cells. Therefore, flexible electrodes that can replace ITO glass are a major issue that must be studied for the future development and application of organic solar cells.

[0005] Common flexible electrodes of organic solar cells include poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and silver nanowires (AgNWs), etc. In recent years, there have been more researches on flexible electrodes of flexible organic solar cells. Although the conductivity of flexible AgNWs electrodes is high, the organic solar cells prepared therefrom have the advantages of large-area preparation and compatibility with roll-to-roll printing, etc., but the AgNWs electrodes have poor transparency and solution processability, and the surface of the AgNWs electrodes is rougher than that of traditional ITO electrodes, and the complex accumulation process of silver wires on the substrate is easy to cause poor repeatability and uniformity, which to some extent also limits the further development of the application of the electrodes as organic solar cell electrodes. Therefore, although the PCE of flexible organic solar cells has been significantly improved in recent years, the high requirements of thermal stability, flexibility, high conductivity and high transparency of electrode materials restrict the further development of large-area flexible or semi-transparent organic solar cells. Only by obtaining electrodes with the advantages of thermal stability, flexibility, high conductivity and high transparency, etc. can organic solar cells have a broader research prospect. In addition, light transmittance, conductivity and PCE are the main parameters for evaluating the performance of flexible electrodes and flexible cells, however, they are a kind of trade-off relationship in nature, therefore, it is still a challenge to simultaneously obtain electrodes with the advantages of high light transmittance, high conductivity and flexibility, etc. and cells with high PCE in flexible organic solar cells. SUMMARY

[0006] In order to solve the problems of brittleness, conductivity and transparency of the flexible electrode, the ITO@polymer electrode integrating the advantages of high thermal stability, high conductivity, transparency and flexibility is prepared by in-situ electrochemical polymerization of polymer on the ITO electrode. The ITO electrode is used, and the small molecule monomer solution is used as the electrolyte for electrochemical polymerization to realize the directional in-situ polymerization of the monomer molecules in the amorphous structure of ITO. The small molecule monomer is preferably a monomer with a polar functional group, such as epoxy ethylene, methyl methacrylate, hydroxy ethylene and aniline. Through the optimization of the reaction conditions, the new ITO@polymer electrode integrating the advantages of high thermal stability, high conductivity, flexibility and high transparency is obtained. The electrode integrating the advantages of high light transmittance, high conductivity and flexibility is combined with the active layer structure design and device optimization, so that the commercial application of the large-area screen printing, inkjet printing and roll-to-roll processing of the organic solar cell can be realized on the basis of ensuring the high PCE of the organic solar cell, and the ideal super-flexible wearable organic solar cell electrode is realized.

[0007] The ITO electrode has the advantages of low cost, good thermal stability, high light transmittance and high conductivity, and has always been the preferred electrode of the organic solar cell.

[0008] The polymer has excellent flexibility and adhesion, and can be bonded into a multi-phase solid material with other materials with different compositions, shapes and properties, and the material interface has flexibility. The biggest advantage of the polymer composite material is to combine the advantages of various materials, and according to the application purpose, the polymer material and other materials with special properties are selected to make the composite material meeting the needs.

[0009] The principle analysis of the compatibility of the polymer chain with the ITO amorphous structure: a large number of literature studies show that the ITO / polymer material formed by simple physical spin coating or immersion has the problem that the polymer chain size is too large to enter the ITO amorphous structure, which leads to the formation of a thin film layer of the polymer on the ITO surface, which cannot improve the problem of large brittleness of ITO. Research reports that the polycyclic aromatic small molecule can be introduced into the functionalized few-wall carbon nanotube matrix to realize the interaction between the organic small molecule and the functionalized few-wall carbon nanotube matrix, and form the transformation of the new chemical configuration and electronic structure of the carbon nanotube. Therefore, the small molecule monomer solution of the polymer is expected to be compatible with the ITO amorphous structure, and under certain polymerization conditions, the small molecule monomers are polymerized into polymer chains in the ITO amorphous structure to realize the compatibility of the polymer chain with the ITO amorphous structure. The ITO and the polymer adhere firmly to the thin film. The electrochemical polymerization method refers to the electrochemical polymerization or chemical synthesis of monomers to obtain the corresponding polymer. This preparation method has the characteristics of simplicity, convenience, low price of monomers and small size of small molecule monomers, and is an effective method for synthesizing polymer materials. The ITO electrode and the small molecule monomer solution are used as the electrolyte for electrochemical polymerization to realize the directional polymerization of the monomer molecules in the ITO microstructure.

[0010] Therefore, the polymer ITO@polymer electrode prepared by electrochemical in-situ in the ITO amorphous structure region has the flexibility, processability and adhesion of the polymer, and retains the high conductivity, high light transmittance and chemical and thermal stability of the ITO, realizes the ITO@polymer new electrode integrating the advantages of high stability, high conductivity, flexibility and transparency, and solves the problem of brittleness of the electrode of the organic solar cell.

[0011] The application provides an electrochemical in-situ polymerized ITO solar cell electrode, which comprises a transparent flexible bottom backing layer (1) and an ITO layer (2) fixed on the transparent flexible bottom backing layer (1), characterized in that the amorphous part of the ITO layer (2) further has a polymer.

[0012] Preferably, the monomer used for polymerization to form the polymer has a polar functional group.

[0013] Preferably, the monomer with the polar functional group is a methacrylate methyl ester monomer, and the polymer is a homopolymer.

[0014] The application further provides a preparation method of the electrochemical in-situ polymerized ITO solar cell electrode.

[0015] S1, a methacrylate methyl ester monomer aqueous solution is configured, and the concentration of the methacrylate methyl ester monomer is 0.01 mol / L-0.1 mol / L;

[0016] S2, in an electrochemical workstation, the ITO electrode comprising the transparent flexible bottom backing layer is used as a working electrode, the monomer small molecule solution is used as an electrolyte, the methacrylate methyl ester monomer is distributed to the amorphous part of the ITO through the polar functional group, hydrogen bond or electrostatic action;

[0017] S3, the monomer molecules are in-situ polymerized into an ITO@polymer flexible electrode in the amorphous part of the ITO by an electrochemical in-situ polymerization method.

[0018] Preferably, in the step S3, the reaction conditions of the electrochemical in-situ polymerization method are as follows: cyclic voltammetry, the composition of the electrolyte is an acetic acid aqueous solution, the concentration of the acetic acid is 0.1 mol / L-0.6 mol / L, the scanning range during polymerization is 1.5 V--1.5 V, and the scanning speed is 0.1-1 V / s. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed in the description of the specific embodiments or prior art will be briefly introduced below, and some specific embodiments of the present application will be described in detail below with reference to the drawings in an exemplary but non-limiting manner. The same reference signs in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0020] Figure 1 Synthesis scheme of ITO@polymer.

[0021] Figure 2 SEM images of mechanical bending test of ITO and ITO@polymer.

[0022] Figure 3 Transmittance test of ITO and ITO@polymer.

[0023] Figure 4 Conductivity test of ITO.

[0024] Figure 5 Conductivity test of ITO.

[0025] Figure 6 Structure schematic diagram of electrochemical in-situ polymerization ITO solar cell electrode. DETAILED DESCRIPTION

[0026] In order to make the purposes, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0027] Example 1

[0028] S1: Prepare a methyl methacrylate ester monomer aqueous solution with a concentration of 0.01 mol / L.

[0029] S2: In an electrochemical workstation, use ITO electrode as working electrode and monomer small molecule solution as electrolyte. Methyl methacrylate ester monomer is distributed to the non-crystalline part of ITO through hydrogen bonding or electrostatic interaction through polar functional groups.

[0030] S3: In-situ polymerize the monomer molecules into ITO@polymer flexible electrode in the non-crystalline part of ITO by electrochemical in-situ polymerization method. The reaction conditions are as follows: cyclic voltammetry method, electrolyte composition is acetic acid aqueous solution, acetic acid concentration is 0.1 mol / L, and the scanning range during polymerization is 1.5V—-1.5V with a scanning speed of 0.1—1V / s.

[0031] Example Two

[0032] S1: Prepare a methyl methacrylate ester methyl ester monomer aqueous solution with a concentration of 0.05 mol / L.

[0033] S2: In an electrochemical workstation, use an ITO electrode as a working electrode and a monomer small molecule solution as an electrolyte, and make the methyl methacrylate ester methyl ester monomer orientally distribute to the amorphous part of the ITO through the polar functional groups, hydrogen bonds or electrostatic interactions.

[0034] S3: Polymerize the monomer molecules in the amorphous part of the ITO in situ into an ITO@polymer flexible electrode through an electrochemical in-situ polymerization method, and the reaction conditions are as follows: cyclic voltammetry: the electrolyte is an acetic acid aqueous solution with an acetic acid concentration of 0.3 mol / L, and the scanning range is 1.5 V-1.5 V during polymerization, and the scanning speed is 0.1-1 V / s.

[0035] Example Three

[0036] S1: Prepare a methyl methacrylate ester methyl ester monomer aqueous solution with a concentration of 0.1 mol / L.

[0037] S2: In an electrochemical workstation, use an ITO electrode as a working electrode and a monomer small molecule solution as an electrolyte, and make the methyl methacrylate ester methyl ester monomer orientally distribute to the amorphous part of the ITO through the polar functional groups, hydrogen bonds or electrostatic interactions.

[0038] S3: Polymerize the monomer molecules in the amorphous part of the ITO in situ into an ITO@polymer flexible electrode through an electrochemical in-situ polymerization method, and the reaction conditions are as follows: cyclic voltammetry: the electrolyte is an acetic acid aqueous solution with an acetic acid concentration of 0.5 mol / L, and the scanning range is 1.5 V-1.5 V during polymerization, and the scanning speed is 0.1-1 V / s.

[0039] In the amorphous structure of ITO, electrochemical in-situ polymerization of polymer is carried out to prepare ITO@polymer electrode, that is, ITO is used as electrode and monomer solution as electrolyte for electrochemical polymerization. This method can realize the compatibility of polymer chain with the amorphous structure of ITO. A large number of literature studies show that the ITO / polymer material formed by simple physical spin coating or immersion method has the problem that the polymer chain size is too large to enter the amorphous structure of ITO, resulting in the formation of a thin film layer of polymer on the surface of ITO, which cannot improve the problem of large brittleness of ITO. Research reports that polycyclic aromatic small molecules can be introduced into the functionalized few-walled carbon nanotube matrix to realize the interaction between organic small molecules and the functionalized few-walled carbon nanotube matrix, and form a new chemical configuration and electronic structure transformation of carbon nanotubes. Therefore, the small molecule monomer solution of polymer is expected to be compatible with the amorphous structure of ITO, and under certain polymerization conditions, the small molecule monomers are polymerized into polymer chains in the amorphous structure of ITO, realizing the compatibility of polymer chains with the amorphous structure of ITO. In addition, it can also realize the firm adhesion of ITO and polymer chain film. The electrochemical polymerization method refers to the electrochemical polymerization or chemical synthesis of monomers to obtain the corresponding polymer. This preparation method has the characteristics of simplicity, convenience, low price of monomers and small size of small molecule monomers, and is an effective method for synthesizing polymer materials. Electrochemical polymerization with ITO as electrode and monomer solution as electrolyte can realize the directional polymerization of monomer in the microstructure of ITO. This electrochemical in-situ polymerization of ITO@polymer electrode not only has the flexibility, processability and adhesion of polymer, but also retains the high conductivity, high transmittance and chemical and thermal stability of ITO, realizing the integration of heat stability, high conductivity, flexibility and transparency of ITO@polymer new electrode, and providing an optimal solution to the problem of brittleness of organic solar cell electrode.

[0040] The products obtained in the above three examples have similar performance, and the test methods are described below.

[0041] Test of electrode bending test:

[0042] The prepared ITO@polymer electrode is bent on the curved surface of a cylinder with a diameter of 2 cm. Figure 2 The crack development process of the electrode is studied by scanning electron microscope (SEM, Inspect F50, FEI, USA), and no crack is generated after bending 800 times. An ultra-thin stretchable transparent electrode with excellent performance is developed, which is a key link for realizing new wearable electronic applications.

[0043] Test of electrode conductivity:

[0044] The resistance change process of the electrode bending process is tested by voltage-current test, and the results are as follows. Figure 5As shown in the figure, the slope of the curve in the figure slowly decreases only after several hundred bends, and the polymer in the non-crystalline region of ITO is beneficial to the slow decrease of the conductivity of the electrode after several hundred bends; compared with the traditional ITO without the polymer in the non-crystalline region, the conductivity of the electrode decreases slowly after several hundred bends. Figure 4 As shown in the figure, the slope of the curve in the figure obviously decreases after 5-15 bends, and the conductivity of the ITO electrode obviously decreases.

[0045] Electrode transmittance test:

[0046] The transmittance change of the electrode is tested by using an ultraviolet-visible spectrometer, as shown in the figure. Figure 3 As shown in the figure, the transmittance of ITO@polymer does not obviously decrease compared with ITO, and the excellent transmittance is still ensured.

[0047] The above is only part of the specific embodiments of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for the preparation of an electrode for an ITO solar cell by electrochemical in situ polymerization, characterized in that, The method comprises the following steps: S1: configuring a methyl methacrylate monomer aqueous solution, the concentration of the methyl methacrylate monomer being 0.01-0.1 mol / L; S2: on an electrochemical workstation, taking an ITO electrode comprising a transparent flexible base layer as a working electrode, a monomer small molecule solution as an electrolyte, and the methyl methacrylate monomer being oriented and distributed to the non-crystalline part of the ITO through a polar functional group, hydrogen bond or electrostatic action; S3: in-situ polymerizing the monomer molecules into an ITO@polymer flexible electrode in the non-crystalline part of the ITO through an electrochemical in-situ polymerization method; The electrochemical in-situ polymerization ITO solar cell electrode comprises a transparent flexible base layer (1) and an ITO layer (2), the ITO layer (2) being fixed on the transparent flexible base layer (1), the non-crystalline part of the ITO layer (2) further having a polymer, and the monomer used for polymerizing the polymer being a small molecule monomer with a polar functional group; the small molecule monomer with a polar functional group being a methyl methacrylate monomer, and the polymer being a homopolymer. The reaction conditions of the electrochemical in-situ polymerization method are as follows: the electrolyte composition is an acetic acid aqueous solution, and the acetic acid concentration is 0.1-0.6 mol / L.

2. The method for preparing an electrochemically in-situ polymerized ITO solar cell electrode as described in claim 1, characterized in that, In the step S3, the reaction conditions of the electrochemical in-situ polymerization method are as follows: in the cyclic voltammetry method, the scanning range during polymerization is 1.5-1.5 V, and the scanning speed is 0.1-1 V / s.

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