CN102354608B - Dye sensitized solar cell by utilizing complex film with carbon nanotubes and polymers as counter electrode - Google Patents

Abstract

The invention belongs to the technical field of solar cells, in particular to a method for preparing a dye-sensitized solar cell based on a vertically aligned carbon nanotube/polymer composite film as a counter electrode. The invention adopts an infiltration method to infiltrate the polymer monomer into the array, and then heat and solidify to form a composite material; finally, the sample is sliced by a microtome to obtain a carbon nanotube/polymer composite film. The carbon nanotubes in the film are perpendicular to the surface of the film and uniformly distributed, so that the upper and lower surfaces of the film have good electrical conductivity, and there are a large number of carbon nanotube end openings on the film surface to facilitate other applications such as modification or catalysis. We used this thin film instead of platinum as the counter electrode to construct dye-sensitized solar cells, and achieved good results, thereby greatly reducing the cost. Therefore, the present invention opens up a series of solar cells using aligned carbon nanotubes as electrodes.

Description

carbon nanotubes / Dye-sensitized solar cells with polymer composite film as counter electrode

technical field

The invention belongs to the technical field of solar cells, and in particular relates to a dye-sensitized solar cell.

Background technique

The discovery of carbon nanotubes is a milestone in the history of world science. In 1991, Iijima, Japan discovered carbon nanotubes (Carbon Since Nanotubes, CNTs)[1], carbon nanotubes are known for their unique high tensile strength, high elasticity, electrical properties from metal to semiconductor, high current load capacity and high thermal conductivity, and unique quasi-one-dimensional tubular molecular structure. , has many potential application values in the high-tech field in the future, and has become the focus of people's attention.

Since Ajayan et al[2] added CNTs as inorganic fillers to the polymer matrix to prepare polymer-CNT composites in 1994, a lot of research work has been carried out. In general, carbon nanotubes are considered short fibers when filled with polymers, and their distribution and orientation are random. Its large aspect ratio and specific surface area significantly enhance the van der Waals force between the tubes, resulting in easy aggregation, winding into bundles or clusters [3], forming defects and stress concentration points in the polymer matrix and reducing the mechanical properties of the material. and reduce the functionalization effect. With the in-depth study of carbon nanotube arrays (ACNTs), the macroscopic length of nanotube arrays is sufficient to allow a single carbon tube to penetrate the entire material in a composite material. Using the order of carbon nanotube arrays to prepare polymer-carbon nanotube composites with uniform dispersion and anisotropy and special functions has become a new research hotspot. Currently, there are two main methods for preparing polymer-carbon nanotube array composites: in-situ polymerization and polymer infiltration. In situ polymerization method, the thermosetting polymer prepolymer or thermoplastic polymer monomer has a small molecular weight and good fluidity, so it is easier to penetrate into the ACNT gap, and then undergo in situ polymerization to form a polymer-ACNT composite material. Polymer infiltration method, some polymers with relatively good compatibility with ACNT, molten state or low viscosity in solution can also be heated and melted or dispersed in a solvent, and immersed in the array by infiltration method, cooled and solidified Or after the solvent is volatilized, a composite material is formed.

Similarly, carbon nanotubes are widely used in the construction of high-efficiency organic solar cells [4-13], for example, carbon nanotubes are used in dye-sensitized solar cells to replace platinum to catalyze the reduction of triiodide Carbon nanotubes are dispersed in titanium dioxide slurry to promote electron diffusion [14], and carbon nanotubes can also be dispersed in electrolyte to promote electron transport and catalytic effect [15]. Some research groups dispersed carbon nanotubes and spin-coated them on the surface of FTO glass to form a counter electrode, and achieved good results [16]; some research groups also achieved good results by dispersing carbon nanotubes and using inkjet printing to form counter electrodes. efficiency [17]. However, since the random dispersion of carbon nanotubes reduces the separation and transport of charges, in order to further improve the efficiency of organic solar cells based on carbon nanotube counter electrodes, it is urgent to obtain counter electrodes with aligned carbon nanotube films, thereby improving the performance of batteries. performance. The highly oriented carbon nanotube film has been extensively studied due to its remarkable mechanical and electrical properties [18-25]. For example, it has a conductivity of 10 ² S/cm at room temperature, so based on the , we fabricated high-efficiency, low-cost dye-sensitized solar cells.

At present, the research on polymer-carbon nanotube arrays is mainly concentrated in the fields of high-performance structural materials and optoelectronic devices. How to expand its application range and improve its functional effect has become the direction of its development.

Contents of the invention

The object of the present invention is to provide a dye-sensitized solar cell with high efficiency and low cost.

The dye-sensitized solar cell provided by the invention is obtained by using carbon nanotube/polymer composite film platinum as a counter electrode in the dye-sensitized solar cell.

In the present invention, as the carbon nanotube/polymer composite film of the counter electrode of the dye-sensitized solar cell, wherein the carbon nanotubes are perpendicular to the surface of the film and are evenly distributed, so that the upper and lower surfaces of the film have good conductivity, and the film There are a large number of carbon nanotube end openings on the surface, which is convenient for other applications such as modification or catalysis. In the invention, the dye-sensitized solar cell is constructed by using the thin film instead of platinum as a counter electrode, so that the conversion efficiency is improved and the cost is reduced.

The present invention also proposes a method for preparing a dye-sensitized solar cell, the specific steps of which are as follows:

(1) For the preparation of the counter electrode, the solvent is added dropwise on the surface of the FTO glass substrate with the carbon nanotube/polymer composite film. After volatilization, the composite film and the FTO glass are tightly connected by van der Waals force, and Annealing at 120-200 degrees centigrade to finally obtain a counter electrode containing a carbon nanotube/polymer composite film.

(2) Preparation of the working electrode. Print a 4-15 micron thick nanocrystalline titanium dioxide layer on the FTO glass by screen printing. Experiments have proved that the 10 micron thick nanocrystalline titanium dioxide layer has the best efficiency. Calcined at 550 degrees Celsius for 25--35 minutes and annealed. When the temperature of the working electrode drops to 25-150 degrees Celsius, transfer them to 0.5mM/L N719 dye solution for soaking. The experiment proves that the efficiency of transferring into the dye solution is the best at 120 degrees Celsius. After 12-18 hours, take out the adsorption The working electrode was heavily dyed and cleaned with acetonitrile.

(3) Finally, the working electrode and the counter electrode are packaged through a ring-shaped substrate, the package pressure is 0.1-0.5 MPa, the temperature is 110-140 degrees Celsius, and the electrolyte is injected through the small hole on the counter electrode. Finally, a micro-coverslip and a substrate are used to seal the hole to obtain a complete cell.

In the present invention, the preparation method of the carbon nanotube vertically oriented carbon nanotube/polymer composite film is as follows: firstly, the carbon nanotube array is obtained by the chemical vapor deposition method, and the carbon nanotube in the array has a high degree of orientation; The method is to infiltrate the polymer monomer into the interior of the carbon nanotube array, and then heat and solidify to form a composite material; finally, the sample is sliced by a microtome to obtain a carbon nanotube/polymer composite film.

Taking carbon nanotubes embedded in epoxy resin as an example, the specific operation steps for the preparation of carbon nanotubes/polymer composite films are introduced below:

First, preparation of embedding stock solution

On the basis of the classic "EPON 812" formula, add DT-2 toughening agent; the preparation method is: first, configure solution A and solution B: solution A is composed of epoxy resin and dodecenyl succinic anhydride by volume Ratio of 62:100, solution B is composed of epoxy resin and methyl nadic acid anhydride in a volume ratio of 100:89; prepared liquid A and liquid B are ultrasonically ultrasonicated for 10-30 minutes in an ultrasonic cleaner to make the uniform dispersion;

Then mix solution A and solution B at a volume ratio of 2:8, then add 10% of the total volume of solution A and solution B toughening agent, and finally add 1% to 2% of the total volume of solution A and solution B curing accelerator Agents 2, 4, and 6 tris(dimethylaminomethyl)phenol, ultrasonicated for 10-30 minutes, mixed thoroughly to obtain embedding stock solution;

Second, the penetration of epoxy resin

First, prepare reagent 1, reagent 2, reagent 3 and reagent 4. Reagent 1 is prepared according to the volume ratio of acetone: embedding stock solution = 10:1 to 2:1, and reagent 2 is prepared according to acetone: embedding stock solution = 2:1 to 1 : 2 volume ratio, reagent 3 is prepared according to the volume ratio of acetone: embedding stock solution = 1:2 to 1:10, reagent 4 is pure embedding stock solution; then, immerse the carbon nanotube array in reagent 1, soak 3-24 hours, then transferred to reagent 2, soaked for 3-24 hours, then transferred to reagent 3, soaked for 3-24 hours, finally transferred to reagent 4, soaked for 12-36 hours;

Third, embedding solidification

Put the sample soaked in reagent 4 into a suitable mold, then inject the embedding stock solution, and cure it in a polymerization box at 40-100 degrees Celsius for 10-100 hours under normal pressure to obtain carbon nanometers embedded in epoxy resin. tube array;

Fourth, slice the embedded sample

The embedded sample is sliced with a microtome to obtain a carbon nanotube/polymer composite film, and the thickness of the composite film ranges from 50 nanometers to 50 microns.

The carbon nanotube array used in the carbon nanotube/polymer composite film is prepared by conventional technology, and the specific steps are:

The catalyst structure for the synthesis of carbon nanotube arrays is Si/SiO ₂ /Al ₂ O ₃ /Fe, in which the thickness of SiO ₂ is 300-1000 μm, the thickness of Al ₂ O ₃ is 10-30 nm, and the thickness of Fe is 0.5-1.5 nm , Al ₂ O ₃ is located between the silicon wafer and Fe, as a buffer layer, and Fe as a catalyst, which are prepared by depositing a nanometer-thick film on a silicon wafer by an electron beam evaporation coating device; As a carbon source, use argon and hydrogen as carrier gases to synthesize high-degree Celsius oriented carbon nanotube arrays on Si substrates with oxide layers; the flow rate of ethylene is 190-290 sccm, the flow rate of argon is 400-620 sccm, and the flow rate of hydrogen 20-48 sccm, grown in a tube furnace for 5-20 min.

FIG. 7 is a scanning electron microscope image of a section of a carbon nanotube array, wherein the diameter of the multi-walled carbon nanotubes is between 7-12 nanometers, as shown in FIG. 8 . Figure 1a illustrates a schematic diagram of a carbon nanotube/polymer composite array, and the carbon nanotube/polymer composite film is obtained by slicing using a common microtome or an ultramicrotome. The thickness of the composite film can be adjusted precisely. The composite film from 1 micron to hundreds of microns can be obtained by ordinary microtome, and the composite film from tens of nanometers to hundreds of nanometers can be obtained by ultra-thin microtome. The size of the composite film depends on the size of the embedding array, and the high orientation of carbon nanotubes in the composite array has not been destroyed. This method is applicable to both single-walled and multi-walled carbon nanotubes, and here mainly multi-walled carbon nanotubes and resin for research.

The obtained vertically oriented carbon nanotube/resin composite film is transparent below 5 microns, but becomes opaque when it is larger than 5 microns. These composite films have good flexibility and can be bent, curled, bent, etc. for many times. without being destroyed. Figure 2a is a composite film with a thickness of 40 microns, while Figure 2b is the composite film after crimping. At the same time, we further studied the internal structure of the composite film. Figure 2c and d are the scanning electron micrographs of the top and side of the composite film, respectively. We can see that in the thin film obtained after slicing, the nozzles are all cut off, and the carbon nanotubes inside are still highly oriented. The density of carbon nanotubes can also be tuned by changing the synthesis parameters. In the present invention, the density of carbon nanotubes in the film is 10 ¹¹ /cm ² .

The scanning electron microscope photos also show that there is good compatibility between the carbon nanotubes and the resin, and the carbon nanotubes are cut off precisely without being pulled out. Due to the high orientation of the carbon nanotubes in the composite film, the carbon nanotubes exhibit excellent electrical properties. The resistivity in the direction perpendicular to the aligned carbon nanotubes is 10 ^-4 Ω•cm, and the surface resistivity is 10 ^-2 Ω• cm. It is particularly important that the electrical properties of the composite film do not change substantially during bending deformation. Figure 3 shows the changes in the electrical properties of the composite film at a bending angle from 0°C to 180°C. In addition, since the composite film has transparency below 5 microns, it can be used as a flexible electrode in the field of optoelectronics. For example, it can replace platinum electrodes in dye-sensitized solar cells, and if it is below 5 microns, it can replace ITO in organic solar cells.

The basic principle of dye-sensitized solar cells is as follows: under light, dye molecules absorb sunlight energy, and their electrons transition to an excited state; the excited state electrons are unstable, and the electrons quickly transition to the lower energy level of the Ti0 ₂ conduction band. When the dye is oxidized; the electrons injected into the conduction band of Ti0 ₂ are enriched on the conductive substrate, and flow to the external circuit counter electrode (aligned carbon nanotube film) through the conductive film to generate current; the dye molecule is in an oxidized state and is obtained from the electrolyte The electrons return to the reduced state (ground state) to be regenerated; the electrolyte I ^3- is reduced to I ^- by the electrons from the conduction band of Ti0 ₂ , entering the external circuit through the electrode, and finally reaching the cathode. This completes a cycle. This excites. Oxidation. The regeneration cycle of reduction is carried out again and again, and a continuous photocurrent is obtained.

In the present invention, the composite thin film is used to replace the platinum in the traditional counter electrode to construct a new type of dye-sensitized solar cell. Figure 1b shows the specific structure of this new dye-sensitized solar cell. A 10-micron titanium dioxide layer was screen-printed on the FTO glass as the working electrode, and the FTO was covered with a composite film as the counter electrode. With N719 as the dye, it is finally encapsulated by Surlyn, and then the electrolyte is injected and the hole is encapsulated. The battery made of the composite film has good performance, because the open ends of the carbon nanotubes can catalyze the reduction of I ^3- more effectively than the side walls of the carbon nanotubes.

Fig. 4 is a JV curve measured under one sunlight of a dye-sensitized solar cell constructed with vertically aligned carbon nanotubes/polymer composite films of different thicknesses as a counter electrode. As the slice thickness decreases, the open circuit voltage basically does not change, while the short circuit current and filling shadow are increasing.

In order to further understand the reasons for the short-circuit current and the increase of the fill factor, we tested the electrochemical impedance spectrum of the battery under one sunlight. It can be seen from Figure 6 that the first semicircle in the high-frequency region increases with the thickness of the composite film Decrease and decrease, and the first semicircle just reflects the transmission resistance of electrons on the interface between the counter electrode and the electrolyte, and its decrease leads to the increase of filling shadow and short-circuit current.

Figure 5d shows the photoelectric conversion efficiency of cells made of composite films with different thicknesses. Obviously, the efficiency increases with the decrease of the film thickness. Now, when the film thickness of the battery is 10 microns, the efficiency can reach 2.77%. The efficiency can be further reduced by reducing the At the same time, we can also increase the density of carbon nanotubes, the degree of orientation, the compatibility of carbon nanotubes and polymers, and select other polymers to improve efficiency.

Description of drawings

Figure 1, a is a schematic diagram of preparing a vertically aligned carbon nanotube/polymer composite film, and b is a schematic diagram of the structure of a dye-sensitized solar cell after applying the composite film.

Figure 2, a and b are the tiled and curled images of the vertically oriented carbon nanotube/polymer composite film, respectively, c is the SEM image of the top of the composite film, and d is the side cross-sectional view of the composite film.

Figure 3 shows the changes in electrical properties of the vertically aligned carbon nanotube/polymer composite film after being bent at different angles.

Fig. 4 is a JV curve measured under one sunlight of a dye-sensitized solar cell constructed with vertically aligned carbon nanotubes/polymer composite films of different thicknesses as a counter electrode.

Fig. 5, the changes of various parameters of the dye-sensitized solar cell constructed by vertically aligned carbon nanotubes/polymer composite films with different thicknesses as the counter electrode were measured under one sunlight. a is the open circuit voltage, b is the short circuit current, c is the fill factor, and d is the photoelectric conversion efficiency.

Figure 6, the electrochemical impedance spectrum of a dye-sensitized solar cell constructed with vertically aligned carbon nanotubes/polymer composite films of different thicknesses as a counter electrode was measured under a single sunlight.

Figure 7, SEM sectional view of a highly aligned carbon nanotube array.

Figure 8, transmission electron microscope image of a single carbon nanotube.

Detailed ways

1. Synthesis of aligned carbon nanotube arrays [26].

Vertically grown carbon nanotube arrays were synthesized using a typical chemical vapor deposition method in a quartz tube of a tube furnace with Fe(1 nm)/Al ₂ O ₃ (10 nm)/SiO ₂ /Si as catalyst. In the catalyst, Al ₂ O ₃ is located between the silicon wafer and Fe, as a buffer layer, and Fe as a catalyst, which are prepared by depositing a nanometer-thick film on a silicon wafer by an electron beam evaporation coating device. Using chemical vapor deposition method, ethylene is used as carbon source, argon and hydrogen are used as carrier gas, and high-degree Celsius-oriented carbon nanotube arrays are synthesized on Si substrates with oxide layers. The details of the synthesis and the self-assembly of carbon tubes in fibers can be referred to the existing literature reports.

2. The method of composite film.

First, preparation of embedding stock solution

On the basis of the classic "EPON 812" formula, DT-2 type toughening agent is added; the preparation method is as follows: first, configure solution A and solution B: solution A is composed of epoxy resin and dodecenyl succinic anhydride The volume ratio is 62:100. The B liquid is composed of epoxy resin and methyl nadic acid anhydride in a volume ratio of 100:89. The prepared A liquid and B liquid are ultrasonicated in the ultrasonic cleaner for 10-30 minutes. to disperse evenly;

Then mix liquid A and liquid B at a volume ratio of 2:8, then add 10% of the total volume of liquid A and liquid B toughening agent, and finally add 1% to 2% of the total volume of curing accelerators 2, 4, 6 Tris(dimethylaminomethyl)phenol, ultrasonic for 10-30 minutes, fully mixed to obtain embedding stock solution;

Second, the penetration of epoxy resin

First, prepare reagent 1, reagent 2, reagent 3 and reagent 4. Reagent 1 is prepared according to the volume ratio of acetone: embedding stock solution = 10:1 to 2:1, and reagent 2 is prepared according to acetone: embedding stock solution = 2:1 to 1 : 2 volume ratio, reagent 3 is prepared according to the volume ratio of acetone: embedding stock solution = 1:2 to 1:10, reagent 4 is pure embedding stock solution; then, immerse the carbon nanotube array in reagent 1, soak 3-24 hours, then transferred to reagent 2, soaked for 3-24 hours, then transferred to reagent 3, soaked for 3-24 hours, finally transferred to reagent 4, soaked for 12-36 hours;

Third, embedding solidification

Put the sample soaked in reagent 4 into a suitable mold, then inject the embedding stock solution, and cure it in a polymerization box at 40-100 degrees Celsius for 10-100 hours under normal pressure to obtain the epoxy resin-embedded sample. carbon nanotube arrays;

Fourth, slice the embedded sample

The embedded sample is sliced with a microtome to obtain a carbon nanotube/polymer composite film, and the thickness of the composite film ranges from 50 nanometers to 50 microns.

3. Preparation of Counter Electrode.

After the composite film is obtained, the solvent is dripped on the surface of the FTO glass substrate with the carbon nanotube film. After volatilization, the composite film and the FTO glass are tightly connected together by van der Waals force, and are heated at 120-200 degrees Celsius. and annealing at the bottom to finally obtain the counter electrode containing carbon nanotube/polymer composite film.

4. Assembly of dye-sensitized solar cells.

The working electrode of the battery was printed with a 10-micron-thick layer of nanocrystalline titanium dioxide on FTO glass using a screen-printing method, followed by calcination at 500°C for 30 minutes and annealing. Then the titanium dioxide surface was treated with 50 mM/L TiCl ₄ aqueous solution at 70 degrees Celsius for 30 minutes, then calcined at 450 degrees Celsius in air for 30 minutes and annealed to optimize the surface morphology of the titanium dioxide layer. When the temperature of the working electrodes dropped to 120 degrees Celsius, they were transferred to 0.5mM/L N719 dye solution for soaking. After 16 hours, the working electrodes with a large amount of dye absorbed were taken out and cleaned with acetonitrile.

Finally, the working electrode and the counter electrode are packaged through a ring-shaped substrate, the package pressure is 0.2 MPa, the temperature is 125 degrees Celsius, and the electrolyte is injected through the small hole on the counter electrode. Finally, a micro-coverslip and a substrate are used to seal the hole to obtain a complete cell.

The structure of carbon nanotubes was characterized by transmission electron microscopy (TEM, JEOL JEM-2100F operated at 200 kV), and the structure of carbon nanotubes/polymer composite films was characterized by scanning electron microscopy (SEM, Hitachi FE-SEM S-4800 operated at 1 kV) to characterize. The J-V curve of the solar cell is measured under the intensity of one sunlight. The solar simulator used is Oriel-94023 type, with Keithley 2400 source meter, and 1000WXe lamp. The AC impedance spectrum of the battery is obtained under a sunlight through CHI 660a (Shanghai, China) electrochemical workstation measured. The Raman spectrum was measured on a Renishaw inVia Reflex instrument with an excitation wavelength of 514.5 nm, the energy of the laser is 20 mW at room temperature. The light transmittance of the composite film is in Shimadz Measured on UV-3150.

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Claims (3)

1. A preparation method of a dye-sensitized solar cell with carbon nanotube/polymer composite film as counter electrode, in the described dye-sensitized solar cell, with carbon nanotube/polymer composite film as counter electrode; The carbon nanotubes in the carbon nanotube/polymer composite film are perpendicular to the surface of the film, and are evenly distributed, and there are a large number of carbon nanotube end openings on the film surface; it is characterized in that the specific steps of preparation are as follows: (1) To prepare the counter electrode, drop the solvent on the surface of the FTO glass substrate with the carbon nanotube/polymer composite film. After volatilization, the composite film and the FTO glass are closely connected by van der Waals force, Annealing at 120-200 degrees Celsius to obtain a counter electrode containing a carbon nanotube/polymer composite film; (2) To prepare the working electrode, print a layer of nanocrystalline titanium dioxide layer with a thickness of 4-15 microns on the FTO glass by screen printing, then calcinate at 450-550 degrees Celsius for 25--35 minutes and anneal; wait for the temperature to drop When it reaches 25-150 degrees Celsius, transfer it to 0.5mM/L N719 dye solution for soaking 12--18 hours, take it out, get the working electrode that has adsorbed a lot of dye, and clean it with acetonitrile; (3) Finally, the working electrode and the counter electrode are packaged through a ring-shaped substrate, the packaging pressure is 0.1-0.5MPa, the temperature is 110-140 degrees Celsius, and the electrolyte is injected through the small hole on the counter electrode; then use a micro cover glass Seal the small hole with the substrate to obtain a complete battery; Wherein, the preparation steps of carbon nanotube/polymer composite film are: First, preparation of embedding stock solution On the basis of "EPON 812" formula, add DT-2 toughening agent; the preparation method is: First, configure solution A and solution B: solution A is composed of epoxy resin and dodecenyl succinic anhydride in a volume ratio of 62:100, and solution B is composed of epoxy resin and methyl nadic anhydride in a volume ratio of 100: The ratio of 89 is composed; the prepared liquid A and liquid B are ultrasonicated in the ultrasonic cleaner for 10-30 minutes to make them evenly dispersed; Then, mix solution A and solution B at a volume ratio of 2:8, add 10% of the total volume of solution A and solution B toughening agent, and finally add 1% to 2% of the total volume of solution A and solution B Agents 2, 4, and 6 tris(dimethylaminomethyl)phenol, ultrasonicated for 10-30 minutes, mixed thoroughly to obtain embedding stock solution; Second, the penetration of epoxy resin First, prepare reagent 1, reagent 2, reagent 3 and reagent 4. Reagent 1 is prepared according to the volume ratio of acetone: embedding stock solution = 10:1 to 2:1, and reagent 2 is prepared according to acetone: embedding stock solution = 2:1 to 1 : 2 volume ratio, reagent 3 is prepared according to the volume ratio of acetone: embedding stock solution = 1:2 to 1:10, reagent 4 is pure embedding stock solution; then, immerse the carbon nanotube array in reagent 1, soak 3-24 hours, then transferred to reagent 2, soaked for 3-24 hours, then transferred to reagent 3, soaked for 3-24 hours, finally transferred to reagent 4, soaked for 12-36 hours; Third, embedding solidification Put the sample soaked in reagent 4 into a suitable mold, then inject the embedding stock solution, and cure it in a polymerization box at 40-100 degrees Celsius for 10-100 hours under normal pressure to obtain carbon nanometers embedded in epoxy resin. tube array; Fourth, slice the embedded sample The embedded sample is sliced with a microtome to obtain a carbon nanotube/polymer composite film, and the thickness of the composite film ranges from 50 nanometers to 50 microns. 2. the preparation method of dye-sensitized solar cell according to claim 1 is characterized in that the preparation step of the carbon nanotube array in the carbon nanotube/polymer composite film is: The catalyst structure for the synthesis of carbon nanotube arrays is Si/SiO ₂ /Al ₂ O ₃ /Fe, in which the thickness of SiO ₂ is 300-1000 μm, the thickness of Al ₂ O ₃ is 10-30 nm, and the thickness of Fe is 0.5-1.5 nm , Al ₂ O ₃ is located in the middle of the silicon wafer and Fe, as a buffer layer, and Fe as a catalyst, and they respectively deposit a nanometer-thick film on the silicon wafer through an electron beam evaporation coating device; use chemical vapor deposition method, use ethylene as Carbon source, with argon and hydrogen as carrier gases, synthesize highly oriented carbon nanotube arrays on Si substrates with oxide layers; the flow of ethylene is 190-290 sccm, the flow of argon is 400-620 sccm, and the flow of hydrogen is 20 -48 sccm, grown in a tube furnace for 5-20 min. 3. prepared by the preparation method according to claim 1, the dye-sensitized solar cell with the carbon nanotube/polymer composite film as the counter electrode.

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