KR100931134B1 - Dye-Sensitized Solar Cell Using Titanium Oxide Nanotubes and Its Manufacturing Method - Google Patents

Abstract

The present invention relates to a dye-sensitized solar cell using titanium oxide nanotubes and a method for manufacturing the same, wherein a semiconductor electrode is constructed using titanium oxide nanotubes prepared by anodizing alumina, and sintered titanium oxide fine particles The problem of low light conversion efficiency, which is a problem of the conventional dye-sensitized solar cell using the electrode, is overcome, and the improvement of device characteristics and formation of a titanium dioxide film having a large specific surface area can absorb a lot of sunlight and improve the permeability of the electrolyte. It relates to a dye-sensitized solar cell using a titanium oxide nanotube having a and a method of manufacturing the same.

Dye-sensitized, solar cell, titanium oxide nanotubes, anodization, porous alumina template

Description

Dye-sensitized solar cell using titanium dioxide nanotube and method for manufacturing the same}

The present invention relates to a dye-sensitized solar cell and a method of manufacturing the same, and more particularly, to a dye-sensitized solar cell having a semiconductor electrode comprising titanium oxide nanotubes produced by anodized alumina method and a method of manufacturing the same. will be.

In general, solar cells are devices that convert solar energy into electrical energy.

Since the development of dye-sensitized nanoparticle titanium dioxide (Anatase structure) solar cells in 1991 by Michael Gratzel of the Swiss National Lausanne Institute of Advanced Technology (EPFL) [B. O'Regen, M. Gratzel, Nature 353, 737 (1991)] There is much research in this area.

Dye-sensitized solar cells have the potential to replace conventional amorphous silicon solar cells because they have lower manufacturing costs and higher energy conversion efficiency than conventional p-n solar cells.

Dye-sensitized solar cells by Gratzel et al., Unlike silicon solar cells, are photosensitive dye molecules capable of absorbing visible light to generate electron-hole pairs, and nanocrystals for transferring the generated electrons. as Photoelectrochemical solar cell using an oxide semiconductor electrode made of a castle titania particles, passing the excited electrons in the dye receiving light of visible light to the n type semiconductor titanium oxide, and I that is included in the liquid ^electrolyte in the ^- / I ³ Current is generated by regenerating the dye through an electrochemical redox reaction.

The dye-sensitized solar cell is expected to be greatly expected as a solar conversion device because the manufacturing cost is lower than the conventional silicon solar cell and the energy conversion efficiency is higher than the thin film type solar cell, and many studies for practical use have been conducted.

Since the energy conversion efficiency in such a solar cell is proportional to the amount of electrons generated by light absorption, the amount of adsorption of dye molecules must be increased in order to generate a large amount of electrons.

Therefore, in order to increase the concentration of the dye molecules adsorbed per unit area, it is required to prepare the transition metal oxide particles in nano size, and such nano particle manufacturing technology is one of the very important core technologies in manufacturing dye-sensitized solar cells.

However, conventional dye-sensitized solar cells have lower light conversion efficiency than crystalline silicon solar cells, and various methods for increasing efficiency have been sought for commercialization.

For example, various methods are known such as electrode material development using titanium oxide, dye development of high efficiency, and development of counter electrode using carbon nanotube (CNT).

Among them, electrode material development using titanium oxide is being developed in various forms such as nanoparticle type, thin film type, porous particle based on the influence of titanium oxide nanoparticles depending on the crystal form, particle size and particle structure.

As a method for producing nanotube-type and nanorod-type titanium oxide, which has been of great interest recently, a method of growing spherical nanoparticles in strong alkali to grow into nanotubes (US Patent 6,537,517 2003.03.25), in a micelle of a surfactant Wet methods, such as methods for growing nanorods (US Pat. No. 6,855,202 B2 2005.02.15) and the like, are known.

However, the above method requires several washing and filtration processes to remove the strong alkalis and surfactants used to obtain high purity titanium oxide nanoparticles, but the process of separating, washing and drying nano-sized particles is complicated.

In fact, in order to apply titanium oxide nanoparticles as a device, a large amount of pure particles should be obtained, but there is a problem that is not practical by the conventional method.

Therefore, there is a need for a method capable of manufacturing a titanium oxide nanoelectrode having a large specific surface area, a high light conversion efficiency, and a simple manufacturing method by a newer method.

Therefore, the present invention was invented in view of the above, and by using a titanium oxide nanotube manufactured by the anodized alumina method to construct a semiconductor electrode, the conventional electrode used to sinter titanium oxide fine particles using Dye-sensitized solar cells have the advantages of low light conversion efficiency, which is a problem of dye-sensitized solar cells, and the advantages of device absorption and formation of a titanium dioxide film with a large specific surface area. The present invention provides a method for manufacturing a battery and a nanotube electrode.

In order to achieve the above object, the present invention provides a semiconductor electrode having a dye layer, a counter electrode disposed to face the semiconductor electrode, and an electron in the dye layer by an oxidation-reduction reaction interposed between the two electrodes. In the dye-sensitized solar cell comprising an electrolyte solution for supplying,

The semiconductor electrode is composed of a substrate, an ITO or FTO transparent conductive layer formed on the substrate, and a titanium oxide layer formed by laminating on the transparent conductive layer to form a dye layer, wherein the titanium oxide layer is made of titanium oxide nanotubes. Provided is a dye-sensitized solar cell using titanium oxide nanotubes.

In a preferred embodiment, the titanium oxide layer is characterized in that formed to a thickness of 5 ~ 20 ㎛.

The present invention also includes a semiconductor electrode on which a dye layer is formed, a counter electrode disposed to face the semiconductor electrode, and an electrolyte solution interposed between the two electrodes to supply electrons to the dye layer by an oxidation-reduction reaction. In the manufacturing method of the dye-sensitized solar cell,

Preparing a porous alumina template for preparing titanium oxide nanotubes;

Forming a titanium oxide nanotube layer using the template on a transparent electrode for a semiconductor electrode comprising a substrate and an ITO or FTO transparent conductive layer formed on the substrate;

Adsorbing a dye on the titanium oxide nanotube layer to form a dye layer;

Assembling the semiconductor electrode formed by forming the titanium oxide nanotube layer and the dye layer to face the counter electrode, and injecting and encapsulating an electrolyte solution between the two electrodes;

It provides a method for producing a dye-sensitized solar cell comprising a.

In a preferred embodiment, forming the titanium oxide nanotube layer,

Adding distilled water and hydrochloric acid to an organic solution having a titanium concentration of 2.0 to 2.4 M to prepare a reaction solution having a titanium concentration of 0.03 to 0.07 M and a hydrochloric acid concentration of 0.09 to 0.1 M;

Depositing a porous alumina template on the transparent electrode on which the organic self-assembled thin film is formed on the reaction solution at a reaction temperature to form a titanium oxide film on the surface of the organic self-assembled thin film;

After washing and vacuum drying, the template on which the titanium oxide film was formed was immersed in a mixed solution of chromic trioxide and phosphoric acid to dissolve and remove the template, followed by washing and vacuum drying to obtain titanium oxide nanotubes on the transparent electrode. ;

Characterized in that it comprises a.

In the forming of the titanium oxide film, the porous alumina mold is deposited on the reaction solution for 1 hour at a reaction temperature of 25 to 70 ° C. to form a titanium oxide film.

In addition, the organic solution is characterized in that the titanate as a solvent.

In addition, the template formed with the titanium oxide film is immersed in a mixed solution of 20-50 ml of chromic trioxide and 1-5 M phosphate to dissolve and remove.

According to the dye-sensitized solar cell of the present invention having the above-described characteristics and a method of manufacturing the same, a semiconductor electrode is constructed using titanium oxide nanotubes prepared by anodizing alumina, thereby sintering titanium oxide fine particles. The problem of low light conversion efficiency, which is a problem of the conventional dye-sensitized solar cell used, is overcome, and the improvement of device characteristics and formation of a titanium dioxide film having a large specific surface area have advantages of absorbing a lot of solar light and improving the permeability of the electrolyte. do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a dye-sensitized solar cell having a semiconductor electrode comprising titanium oxide nanotubes prepared by anodizing alumina and a method of manufacturing the same.

1 is a schematic diagram of a dye-sensitized solar cell according to the present invention. As shown in FIG. 1, the semiconductor electrode 10 and the counter electrode 20 fixedly coupled to each other by a spacer 14, It is composed of an electrolyte solution 30 interposed therebetween, and the basic configuration in which the electrolyte solution 30 is enclosed and enclosed in the state in which the semiconductor electrode 10 and the counter electrode 20 are assembled in this way is usually Is the same as the dye-sensitized solar cell.

Here, the semiconductor electrode 10 serving as the cathode and the counter electrode 20 serving as the anode are disposed to face each other with the conductive surfaces facing inwards when the two electrodes are assembled together, and the electrolyte solution 30 reacts to the oxidation-reduction reaction. This serves to supply electrons to the dye layer.

However, in the dye-sensitized solar cell of the present invention, the semiconductor electrode 10 includes titanium oxide nanotubes by anodizing alumina, specifically, a substrate 11 such as a glass substrate, and the substrate 11. Titanium oxide layer 13 formed on the transparent conductive layer 12 by adsorbing dye molecules to the formed ITO or FTO transparent conductive layer 12 and titanium oxide nanotubes produced by the anodized alumina method.

Here, the titanium oxide layer 13 is preferably formed to have a thickness of 5 to 20 ㎛ (length of the titanium oxide nanotubes).

At this time, by having a thickness of 5 to 20 ㎛, it is possible to provide a passage for electron transfer to maximize the photocurrent, the specific surface area can be maximized to facilitate the adsorption of the dye.

In addition, the counter electrode 20 may be formed of a substrate 21 such as a glass substrate, an ITO or FTO transparent conductive layer 22 formed on the substrate 21, and a platinum layer formed on the transparent conductive layer 22. 23).

In order to manufacture the dye-sensitized solar cell formed as described above, titanium oxide nanotubes should be manufactured. In order to manufacture the titanium oxide nanotubes, the present invention is made by anodizing an alumina thin film and having nano-sized pores. Anodic Aluminum Oxide (AOO) is prepared, and titanium oxide nanotubes are prepared using the porous Alumina template.

More specifically, the solar cell manufacturing method of the present invention comprises the steps of preparing a porous alumina template for the production of titanium oxide nanotubes; Forming a titanium oxide nanotube layer (13) using the template on a transparent electrode; Adsorbing a dye on the titanium oxide nanotube layer (13); Fixing and encapsulating the semiconductor electrode 10 and the counter electrode 20 including the titanium oxide nanotube layer 13 in the state in which the electrolyte solution 30 is injected through the spacer 14. do.

(1) step of preparing porous alumina mold

The porous alumina template used in the solar cell manufacturing method of the present invention is already used for nanotube synthesis (Registration No. 309293, Registration No. 335384, Registration No. 534845), and in the present invention, such porous alumina mold Titanium oxide nanotubes are manufactured by using the method, and a process of preparing the porous alumina template is a known technique as follows.

2 is a schematic view showing a process of manufacturing a porous alumina mold, and the anodized alumina mold is manufactured using a thin aluminum plate, and a two-step anodization method is used.

Using the two-stage anodization method, it is possible to produce a mold in which pores of uniform diameter are regularly arranged vertically [H. Masuda and M. Satch, Jpn. J. Appl. Phys., 35, (1996) L 126].

In the anodization method, pores are formed by the voltage applied by using an aluminum thin plate as an anode and a carbon electrode as a cathode, through which oxygen ions in the electrolyte solution diffuse into the aluminum, while aluminum ions It comes out and aluminum oxide continues to be produced.

Oxalic acid, phosphoric acid, sulfuric acid, etc. are used as the electrolyte solution in the anodization method.

In the two-step anodization method, as shown in (b) of FIG. 2, the alumina layer is removed from the acid solution after forming the pores. The same electrolyte solution is used to remove the alumina layer. To form the final.

The pore spacing is determined by the voltage and electrolyte solution applied during anodization, and the pore depth is known to be proportional to the anodization time.

Porous alumina molds made in this way have aluminum on the bottom, which can be removed by immersing in a saturated aqueous solution of mercury chloride.

FIG. 2 (f) is a diagram showing a protective film for protecting pores on the top surface of the aluminum to remove the barrier layer between the pores and the aluminum after removing the aluminum.

In order to remove the barrier layer, both a method of dissolving using a base solution or an acid solution capable of dissolving alumina, such as sodium hydroxide, chromic acid, and phosphoric acid, and a mechanical removal method using argon plasma ion milling are all available.

In order to dissolve the barrier layer uniformly, it is preferable to use a 30 ° C. 0.1 M phosphoric acid solution.

As such, after removing the barrier layer, the protective layer is removed with acetone to complete the porous alumina mold in the form of a membrane as shown in FIG.

FIG. 3 is an SEM image of the porous alumina mold prepared by the above method.

(2) titanium oxide nanotube layer formation step

In this step, a titanium oxide nanotube layer is formed by using a porous alumina template on the transparent electrode for semiconductor electrodes formed by forming an ITO or FTO transparent conductive layer on a glass substrate.

As a process for synthesizing titanium oxide nanotubes, first, distilled water and hydrochloric acid are added to an organic solution having a titanium concentration of 2.0 to 2.4 M to prepare a reaction solution having a titanium concentration of 0.03 to 0.07 M and a hydrochloric acid concentration of 0.09 to 0.1 M.

The organic solution may be one using titanate as a solvent, and as an example of the organic solution, a Tizor LATM solution having a titanium concentration of 2.2 M may be used.

Subsequently, a porous alumina mold on the transparent electrode having the organic self-assembled thin film formed on the surface of the pores or the like was immersed in the reaction solution for 1 hour at a reaction temperature of 25 to 70 ° C. to form a titanium oxide film on the surface of the organic self-assembled thin film. Let's do it.

After the completion of the reaction, the solution was immersed in water, washed sufficiently, and vacuum dried at 70 ° C. for 24 hours. Thus, a mixed solution of 20 to 50 ml of chromic trioxide and 1 to 5 M of phosphoric acid was deposited on a template where a titanium oxide film was formed. After dipping at room temperature for 2 hours to dissolve and remove the mold, the resulting residue was sufficiently washed with tertiary distilled water (resistance: 18.3㏁cm), which was vacuum dried at 90 ° C. for 24 hours, and deposited on a transparent electrode. Titanium oxide nanotubes are obtained.

4 is a schematic diagram illustrating a titanium oxide nanotube synthesis, and FIG. 5 shows titanium oxide nanoparticles prepared by (a) 25 ° C, (b) 40 ° C and (c) 70 ° C, respectively. TEM picture of the tube.

When the titanium oxide nanotube layer is formed using the porous alumina template as described above, it is possible to synthesize titanium oxide nanotubes having a large aspect ratio, and to easily control the diameter, length, and density of the titanium oxide nanotubes. There is an advantage.

(3) dye adsorption step

In the semiconductor electrode 10 having the titanium oxide nanotube layer formed as described above, the dye is adsorbed onto the upper titanium oxide nanotube layer, which may be applied to conventional methods well known in the solar cell manufacturing art.

As a photosensitive dye, a widely used ruthenium dye may be used, and a semiconductor layer in which a titanium oxide nanotube layer is laminated is impregnated in a solution containing the dye for at least 12 hours.

Examples of the solvent used for the solution containing the photosensitive dye include tertiary butyl alcohol, acetonitrile, a mixture thereof, and the like.

(4) Solar cell assembly and encapsulation step

When the semiconductor electrode 10 including the titanium oxide nanotube layer on which the dye is adsorbed is manufactured through the above processes, the semiconductor electrode 10 and the counter electrode 20 are assembled and formed on the counter electrode 20. The electrolyte is injected into the dye layer by the oxidation-reduction reaction through the fine pores.

This step of assembling the semiconductor electrode 10 and the counter electrode 20 and then injecting and encapsulating the electrolyte may also be applied to a conventional method well known in the solar cell manufacturing art. First, the counter electrode 20 and the cathode, which are anodes, are applied. The phosphorus semiconductor electrode 10 is assembled.

When assembling the counter electrode 20 and the semiconductor electrode 10, the conductive surfaces of the two electrodes are disposed to face each other with the conductive surfaces facing inwards.

At this time, between the counter electrode 20 and the semiconductor electrode 10, a polymer layer having a thickness of about 30 to 50 μm, which is, for example, a spacer 14 made of SURLYN (trade name manufactured by Du Pont), is placed. The two electrodes are brought into close contact with each other at about 1 to 3 atmospheres on a heating plate of ˜140 ° C.

The polymer layer is strongly attached to the surfaces of the two electrodes by heat and pressure.

Next, after forming the fine hole in the counter electrode 20, the electrolyte solution 30 is filled in the internal space between two electrodes through this fine hole.

Here, the micro holes are typically formed by using a drill of 0.75 mm diameter, and after the electrolyte 30 is completely filled, the micro holes are instantaneously heated to block the micro holes.

The dye-sensitized solar cell of the present invention and its manufacturing method have been described above.

The dye-sensitized solar cell of the present invention includes a semiconductor electrode 10 made of titanium oxide nanotubes prepared by anodizing alumina, and thus has a very small pupil channel because of using titanium oxide nanotubes. The specific surface area is considerably larger than using nanoparticles.

This facilitates penetration of the electrolyte solution, absorbs more sunlight, and facilitates electron transfer, thereby increasing the light conversion efficiency.

Due to the two-dimensional electronic structure of the nanotubes, the electron band spacing of 3.87 eV is larger than that of a general TiO ₂ having an electron band spacing of 3.2 eV, which facilitates electron transfer and absorbs light of various wavelengths.

In addition, when a dye having a positive charge on the surface is adsorbed onto a titanium oxide nanotube, a dye can be obtained more efficiently dye-sensitized solar cell.

Table 1 is a table comparing the light conversion efficiency according to the titanium oxide electrode, the light conversion efficiency through the experiment using the titanium oxide nanotube electrode according to the present invention and the case of using a conventional titanium oxide nanoparticle electrode I saw a comparison.

When a ruthenium dye having a negative charge, which is a common dye material, was used, an open current voltage of 0.704 V, a short current of 12.6 mA / cm ² , and an energy conversion efficiency of 7.1% were shown.

Therefore, a dye having a positive charge can be used to obtain a highly efficient dye-sensitized solar cell.

1 is a block diagram of a dye-sensitized solar cell according to the present invention,

Figure 2 is a schematic diagram showing the manufacturing process of the porous alumina mold used in the present invention,

3 is an SEM image of the porous alumina template used in the present invention,

4 is a conceptual diagram of titanium oxide nanotube synthesis in the present invention,

Figure 5 is a TEM photograph of the titanium oxide nanotubes prepared by the reaction temperature in the present invention (a) 25 ℃, (b) 40 ℃, (c) 70 ℃, respectively.

<Explanation of symbols for the main parts of the drawings>

10 semiconductor electrode 11 substrate

12: transparent conductive layer 13: titanium oxide nanotube layer

Claims (7)

delete delete A dye-sensitized composition including a semiconductor electrode having a dye layer, a counter electrode disposed to face the semiconductor electrode, and an electrolyte solution interposed between the two electrodes to supply electrons to the dye layer by an oxidation-reduction reaction. In the manufacturing method of the type solar cell, Preparing a porous alumina template for preparing titanium oxide nanotubes; Forming a titanium oxide nanotube layer using the template on a transparent electrode for a semiconductor electrode comprising a substrate and an ITO or FTO transparent conductive layer formed on the substrate; Adsorbing a dye on the titanium oxide nanotube layer to form a dye layer; Assembling the semiconductor electrode formed by forming the titanium oxide nanotube layer and the dye layer to face the counter electrode, and injecting and encapsulating an electrolyte solution between the two electrodes; Dye-sensitized solar cell manufacturing method comprising a. The method according to claim 3, Forming the titanium oxide nanotube layer, Adding distilled water and hydrochloric acid to an organic solution having a titanium concentration of 2.0 to 2.4 M to prepare a reaction solution having a titanium concentration of 0.03 to 0.07 M and a hydrochloric acid concentration of 0.09 to 0.1 M; Depositing a porous alumina template on the transparent electrode on which the organic self-assembled thin film is formed on the reaction solution at a reaction temperature to form a titanium oxide film on the surface of the organic self-assembled thin film; Subsequently, after washing and vacuum drying, the template on which the titanium oxide film was formed was deposited on a mixed solution of chromic trioxide and phosphoric acid to dissolve and remove the template, followed by washing and vacuum drying to obtain titanium oxide nanotubes on the transparent electrode. step; Dye-sensitized solar cell manufacturing method comprising a. The method according to claim 4, In the step of forming the titanium oxide film, a method of manufacturing a dye-sensitized solar cell, characterized in that to form a titanium oxide film by depositing a porous alumina template in the reaction solution for 1 hour at a reaction temperature condition of 25 ~ 70 ℃. . The method according to claim 4, The organic solution is a manufacturing method of a dye-sensitized solar cell, characterized in that the titanate as a solvent. The method according to claim 4, The method of manufacturing a dye-sensitized solar cell, characterized in that the titanium oxide film is formed by immersing and dissolving the template in a mixed solution of 20-50 ml of chromic trioxide and 1-5 M of phosphoric acid.

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