KR101541448B1 - Counter electrode for dye-sensitized solar cell comprising composite material dispersed metal nanoparticle in conducting polymer layer and the method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a counter electrode of a dye-sensitized solar cell including a conductive polymer and metal nanoparticles and a method of manufacturing the same, and more particularly, to a dye-sensitized solar cell comprising a composite material in which metal nanoparticles are dispersed in a conductive polymer layer Preparing a metal nanoparticle-conductive polymer composite by mixing a counter electrode, a conductive polymer aqueous solution and a metal precursor, and then adding a reducing agent (step 1); Spin coating the composite material of step 1 on a substrate coated with a transparent electrode (step 2); And a step of heat treating the substrate coated with the composite material of step 2 to prepare a counter electrode (step 3); and a dye-sensitized solar cell manufactured by the manufacturing method of the dye-sensitized solar cell .
The present invention has transparency, flexibility, and conductivity, which are advantages of the conductive polymer and the metal nanoparticle, and can be provided at a relatively lower price than the case of using only the metal material. In addition, in the method of manufacturing a counter electrode according to the present invention, since the solution coating process is possible, the process is simple and the process can be performed at a low temperature, which is also applicable to a flexible substrate. Furthermore, since the conductive polymer plays a role of maintaining the dispersion and stability of the metal nanoparticles, the problem of deterioration of the conductivity and the charge transfer characteristics of the metal nanoparticles can be prevented by adding the stabilizer.

Description

TECHNICAL FIELD [0001] The present invention relates to a counter electrode for a dye-sensitized solar cell including a composite material in which metal nanoparticles are dispersed in a conductive polymer layer and a method for manufacturing the same. manufacturing thereof}

The present invention relates to a counter electrode of a dye-sensitized solar cell including a composite material in which metal nanoparticles are dispersed in a conductive polymer layer, and a method of manufacturing the same.

Recently, interest in renewable energy is rising due to soaring oil prices and depletion of fossil energy. Among them, researches on solar cells using solar energy are actively being carried out.

A solar cell is a device that converts light energy into electric energy by using photovoltaic effect. Depending on its constituent materials, a solar cell, a thin film solar cell, a dye-sensitized solar cell, an organic polymer solar cell and a hybrid solar cell .

The dual dye-sensitized solar cell has a lower manufacturing cost and a simpler manufacturing process than the conventional commercially available silicon solar cell, and has the energy conversion efficiency similar to that of an amorphous silicon solar cell, and has been attracting attention as a next generation solar cell.

In particular, in order to expand applications, research on a flexible dye-sensitized solar cell using a thin and light substrate has been actively conducted.

For flexible dye-sensitized solar cells, they are fabricated on plastic substrates or thin metal substrates instead of conventional glass substrates.

Although a metal substrate has an advantage of being able to carry out a high-temperature process, a transparent property, which is one of the merits of a dye-sensitized solar cell, is lost, and a plastic substrate has transparency, but a photoelectric conversion efficiency is lowered .

Generally, in the production of a dye-sensitized solar cell, a process of forming a photoelectrode by heat-treating TiO 2 nanoparticles and a process of forming a counter electrode by thermally reducing the Pt solution require a high-temperature process of 400 ^° C or more.

However, in the case of a plastic substrate, there are problems such as deformation of the substrate at a temperature of 150 ^° C or higher. To solve such a problem, studies on the development of a low-temperature process material that can proceed on a plastic substrate are underway.

For example, attempts have been made to apply electrochemical coating of PEDOT, which is a conductive polymer, or application of a composite material of PEDOT and various carbon-based materials (carbon nanotubes, carbon black, graphene, etc.).

However, these methods are complicated and difficult to apply to large-area and flexible substrates.

On the other hand, Korean Patent No. 10-0882503 discloses a high-efficiency counter electrode for a dye-sensitized solar cell and a manufacturing method thereof as a conventional technique related to a counter electrode material for a dye-sensitized solar cell. Specifically, a dye sensitized solar cell comprising a photoelectrode comprising a photo sensitive dye molecule layer, a counter electrode including a platinum catalyst layer facing the photo electrode, and an electrolyte solution interposed between the photo electrode and the counter electrode, (1) a structure in which a conductive polymer is coated as an electron transporting active layer on a platinum catalyst layer included in the counter electrode; (2) a structure coated with platinum nanoparticles; (3) a structure in which platinum nanoparticles and a conductive polymer are sequentially coated; (4) a structure coated with fullerene; (5) a structure in which fullerene and a conductive polymer are sequentially coated; (6) a structure in which fullerene and platinum nanoparticles are sequentially coated; (7) a structure in which fullerene, platinum nanoparticles and conductive polymer are sequentially coated; (8) a structure in which an inorganic oxide particle and a platinum thin film are sequentially coated; (9) a structure in which an inorganic oxide particle, a platinum thin film and a conductive polymer are sequentially coated; (10) a structure in which an inorganic oxide particle and a conductive polymer are sequentially coated; (11) a structure coated with a conductive polymer blend; (12) a structure in which a platinum nanoparticle and a conductive polymer blend are sequentially coated; (13) a structure in which fullerene and a conductive polymer blend are sequentially coated; (14) a structure in which fullerene, a platinum nanoparticle and a conductive polymer blend are sequentially coated; Or (15) a structure in which an inorganic oxide particle, a conductive polymer blend and a platinum thin film are sequentially coated, has been disclosed.

However, in the case of the counter electrode, one material characteristic is mainly exhibited, so that the series resistance of the device is increased and the surface activity is decreased.

Accordingly, the inventors of the present invention have conducted research on a counter electrode material for use in a dye-sensitized solar cell device, and have found that they can be manufactured in a low-temperature process for application to a flexible dye-sensitized solar cell device, A counter electrode of a dye-sensitized solar cell including a composite material in which metal nanoparticles are dispersed in a conductive polymer layer capable of realizing an activation effect, and a method for manufacturing the same, and completed the present invention.

SUMMARY OF THE INVENTION

And a counter electrode of the dye-sensitized solar cell.

Another object of the present invention is

And a method of manufacturing a dye-sensitized solar cell.

According to an aspect of the present invention,

A counter electrode of a dye-sensitized solar cell comprising a composite material in which metal nanoparticles are dispersed in a conductive polymer layer is provided.

Further, according to the present invention,

Preparing a metal nanoparticle-conductive polymer composite material by mixing a conductive polymer aqueous solution and a metal precursor with a reducing agent (step 1);

Spin coating the composite material of step 1 on a substrate coated with a transparent electrode (step 2); And

And a step of heat treating the substrate coated with the composite material of step 2 to prepare a counter electrode (step 3).

The counter electrode of the dye-sensitized solar cell including the composite material in which the metal nanoparticles are dispersed in the conductive polymer layer according to the present invention is characterized in that the counter electrode prepared by sequentially laminating the conductive polymer and the metal nano- , Which shows advantages of conductive polymers and metal nanoparticles, transparency, flexibility and conductivity, and can be provided at a relatively lower price than the case of using only a metal material have.

In addition, in the method of manufacturing a counter electrode according to the present invention, since the solution coating process is possible, the process is simple and the process can be performed at a low temperature, which is also applicable to a flexible substrate.

Furthermore, since the conductive polymer plays a role of maintaining the dispersion and stability of the metal nanoparticles, the problem of deterioration of the conductivity and the charge transfer characteristics of the metal nanoparticles can be prevented by adding the stabilizer.

FIG. 1 is a schematic view of a step 1 of a method for producing a counter electrode of a dye-sensitized solar cell according to the present invention;
FIG. 2 is a photograph of a metal nanoparticle-conductive polymer composite material for a dye-sensitized solar cell counter electrode prepared in step 1 of Example 1, observed with a scanning electron microscope (SEM);
3 is a schematic view showing the structure of the dye-sensitized solar cell manufactured in Example 2 and Comparative Example 1;
4 is a graph showing current densities of the dye-sensitized solar cell prepared in Example 2 and Comparative Example 1. FIG.

The present invention

A counter electrode of a dye-sensitized solar cell comprising a composite material in which metal nanoparticles are dispersed in a conductive polymer layer is provided.

Hereinafter, the counter electrode of the dye-sensitized solar cell according to the present invention will be described in detail.

The present invention provides a counter electrode of a dye-sensitized solar cell comprising a composite material in which metal nanoparticles are dispersed in a conductive polymer layer.

The counter electrode of the dye-sensitized solar cell has a problem in that the counter electrode manufactured by sequentially laminating the conductive polymer and the metal nano-particle sequentially exhibits only one characteristic of the material, thereby increasing the series resistance and reducing the surface activity. It has transparency, flexibility and conductivity, which are advantages of metal nanoparticles, and can be manufactured with a simple process and can be provided at a relatively low price.

In addition, since the process can be performed at a low temperature, it can be used as a counter electrode of a flexible dye-sensitized solar cell, and it can be provided at a lower cost than a metal material alone.

In this case, the composite material may be produced by reduction with a reducing agent.

The composite material may be prepared by synthesizing metal nanoparticles in a conductive polymer by a direct reduction method. Alternatively, the composite material may be prepared by reducing metal nanoparticles with a reducing agent, dispersing the metal nanoparticles in a conductive polymer, The method for producing the composite material is not limited thereto, and a method for manufacturing the composite material using the reducing agent can be appropriately selected and used.

The conductive polymer may be poly (3,4-ethylenedioxythiophene), poly (4-styrenesulfonate), or poly (3,4-ethylenedioxythiophene) wherein the polyaniline is selected from the group consisting of polyglycol (glycerol), PANI: poly (4-styrene sulfonate), PANI: polyaniline, camphor sulfonic acid, dioxythiophene derivatives, Or more, but the conductive polymer is not limited thereto, and any conventional conductive polymer material may be used.

The metal may be a precious metal, and the precious metal may be at least one selected from the group consisting of platinum, gold, silver, copper and palladium.

However, the metal is not limited thereto, and a metal capable of exhibiting normal catalytic activity can be used.

Further, according to the present invention,

Preparing a metal nanoparticle-conductive polymer composite material by mixing a conductive polymer aqueous solution and a metal precursor with a reducing agent (step 1);

Spin coating the composite material of step 1 on a substrate coated with a transparent electrode (step 2); And

And a step of heat treating the substrate coated with the composite material of step 2 to prepare a counter electrode (step 3).

Hereinafter, a method of manufacturing the dye-sensitized solar cell according to the present invention will be described in detail.

In the method of manufacturing a dye-sensitized solar cell according to the present invention, the step 1 is a step of preparing a metal nanoparticle-conductive polymer composite material by mixing a conductive polymer aqueous solution and a metal precursor and then adding a reducing agent, 1 shows a schematic view of a method for producing the metal nanoparticle-conductive polymer composite material of step 1 described above.

In the step 1, a metal nanoparticle-conductive polymer composite material is prepared by mixing a conductive polymer aqueous solution and a metal precursor and then adding a reducing agent.

Conventionally, stabilizers such as polyvinylpyrrole (PVP) or hexadecyltrimethylammonium bromide (CTAB) have been generally used for nanoparticle synthesis and prevention of agglomeration. Most of them are organic dielectric materials, And the conductivity and the charge transfer characteristics of the capacitor are hindered.

On the other hand, when the in-situ method for synthesizing metal nanoparticles in the conductive polymer according to the present invention is used, the conductive polymeric material simultaneously plays a role of maintaining dispersion and stability, and thus the problem can be avoided , Or simply by mixing a conductive polymer aqueous solution and a metal precursor, and then adding a reducing agent.

The reducing agent of step 1 may be at least one selected from the group consisting of borohydride, alkali metal or alkaline earth metal, N ₂ H ₄ , citric acid or its salt, and reducing sugar.

NaBH ₄ , KBH ₄ , and Mg (BH ₄ ) ₂ can be used as the alkali metal or alkaline earth metal borohydride. As the salt of citric acid, sodium citrate and potassium citrate can be used. As the reducing sugar, Fructose, maltose, galactose, lactose, cellulose and the like.

However, the reducing agent is not limited thereto, and a conventional metal reducing agent can be used.

Wherein the metal precursor of step 1 is selected from the group consisting of H ₂ PtCl _{6 ,} H ₂ PtCl ₄ , [Pt (NH ₃ ) ₄ ] Cl ₂ And H ₂ Pt (OH) ₆ may be used, but the metal precursor is not limited thereto.

In the method of manufacturing a dye-sensitized solar cell according to the present invention, step 2 is a step of spin-coating the composite material of step 1 on a substrate coated with a transparent electrode.

In the step 2, a counter electrode layer is formed by spin coating the metal nanoparticle-conductive polymer composite material prepared in the step 1 on a substrate coated with a transparent electrode, thereby preparing a counter electrode by a simple solution coating process.

At this time, the substrate of step 2 may be a flexible substrate.

As the flexible substrate, a plastic substrate may be used. However, the flexible substrate is not limited thereto, and the plastic may be, but not limited to, PET, PEN, PC, PI,

In the method of manufacturing a dye-sensitized solar cell according to the present invention, the step 3 is a step of preparing a counter electrode by heat-treating a substrate coated with the composite material of the step 2.

In the step 3, the counter electrode is manufactured by subjecting the substrate coated with the composite material of the step 2 to heat treatment.

Conventionally, a platinum counter electrode layer was fabricated by physical vapor deposition using a platinum target on a cathode substrate of a dye-sensitized solar cell, or by coating with a platinum aqueous solution and then thermally reducing the mixture at a high temperature of 400 ° C or more. It is not easy to apply the method of the present invention. As an alternative, a counter electrode layer was prepared by coating a conductive polymer solution and then drying at a low temperature of 150 ° C or less. However, there was a problem in that the device efficiency was low.

On the other hand, in the present invention, the metal nanoparticle-conductive polymer composite prepared by mixing the conductive polymer aqueous solution and the metal precursor and then adding a reducing agent is spin-coated on a substrate coated with a transparent electrode, and then heat- So that a process can be performed at a low temperature so as to be applicable to a flexible substrate.

At this time, the heat treatment in step 3 may be performed at a temperature of 100 to 200 ° C for 10 minutes to 10 hours.

If the heat treatment in step 3 is carried out at a temperature of less than 100 ° C., water as a solvent in the conductive polymer aqueous solution may remain in the finally formed counter electrode layer. If the heat treatment in step 3 is performed at 200 Deg.] C, deterioration of the conductive polymer may degrade the properties of the final counter electrode.

If the heat treatment in step 3 is performed for less than 10 minutes, water as a solvent in the conductive polymer aqueous solution may remain in the finally formed counter electrode layer, and if the heat treatment in step 3 is performed at 10 If the time is exceeded, the characteristics of the final counter electrode may deteriorate due to deterioration of the conductive polymer.

Further,

A dye-sensitized solar cell produced according to the above-described method is provided.

In the manufacturing method of the present invention, since the heat treatment can be performed at a low temperature of about 140 캜 and can be applied to a flexible substrate, a flexible dye-sensitized solar cell can be provided.

In comparison with the dye-sensitized solar cell comprising a counter electrode made of only a conductive polymer, the dye-sensitized solar cell has a high electrical conductivity and is excellent in electrical characteristics and is provided at a lower cost than a dye-sensitized solar cell comprising a counter electrode made of only metal nanoparticles It is possible.

Further, since the conductive polymer serves as a stabilizer, it is not necessary to use a stabilizer having an insulator property, so that a dye-sensitized solar cell having excellent conductivity can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

≪ Example 1 > Preparation of counter electrode

Step 1: 5 ml of PEDOT: PSS conductive polymer aqueous solution and 0.2 mM of H ₂ PtCl ₆ platinum aqueous solution are stirred for 1 hour on a magnetic stirrer.

The metal nanoparticles for a dye-sensitized solar cell counter electrode were prepared by using an in-situ method in which 0.5 mM NaBH ₄ aqueous solution was slowly dropped to the mixed solution and a metal nanoparticle was synthesized in the conductive polymer. To prepare a conductive polymer composite material.

Step 2: The glass substrate coated with the FTO was cut to the same size as the photoelectrode, and the ultrasonic cleaning was performed for 15 minutes in a state in which the powdery detergent was immersed in the solution dissolved in water. Then, the ultrasonic cleaning was carried out for 15 minutes .

Thereafter, the substrate was subjected to ultrasonic cleaning for 15 minutes using acetone, immersed in isopropyl alcohol, and ultrasonically cleaned for 15 minutes to complete the cleaning operation.

The cleaned FTO substrate was dried in a 60 ° C drying oven for 30 minutes or more.

The cleaned FTO substrate is cut to a size of 1.2 cm x 1.6 cm which is the same size as the optical electrode, and then two holes for injecting the electrolyte are drilled using a 0.7 mm diameter diamond drill.

Thereafter, the metal nanoparticle-conductive polymer composite material aqueous solution prepared in the step 1 after the cleaning in the same manner as the photoelectrode was coated using a spin coating method.

Step 3: In step 2, the substrate coated with the composite material was heat-treated at 140 ° C for 20 minutes to prepare a counter electrode.

Example 2: Preparation of dye-sensitized solar cell

Step 1: A glass substrate coated with fluorotin oxide (FTO) as a substrate for photoelectrode is subjected to ultrasonic cleaning for 15 minutes in a state of immersing in a solution in which a powder type cleaning agent is dissolved in water, followed by ultrasonic cleaning in a state of being contained in distilled water 15 minutes.

Thereafter, the substrate was subjected to ultrasonic cleaning for 15 minutes using acetone, immersed in isopropyl alcohol, and ultrasonically cleaned for 15 minutes to complete the cleaning operation.

The cleaned FTO substrate was dried in a 60 ° C drying oven for 30 minutes or more.

Step 2: Ti-Nanoxide T / SP of Solaronix Co. was coated on the cleaned FTO substrate using a doctor blade method.

Thereafter, the resultant was heated at 100 占 폚 for 20 minutes and then calcined at 500 占 폚 for 1 hour. In order to improve the inter-particle connection of the finished TiO ₂ film, the substrate coated with TiO ₂ was immersed in a 40 mM titanium (IV) chloride solution, heated at 70 ° C. for 30 minutes, rinsed with distilled water and ethanol After drying at 60 ° C for several minutes, it is baked at 500 ° C for 1 hour.

Step 3: The photosensitizer was adsorbed by immersing the substrate coated with the TiO ₂ film with the calcination process in a 0.5 mM N719 dye solution for about 24 hours.

After the completion of the adsorption, the non-adsorbed photosensitizer was washed with acetonitrile and dried through an oven at 60 ° C to prepare a photoelectrode.

A sealant for fabricating a dye-sensitized solar cell is formed around the completed photo-electrode portion.

Step 4: The formed photo-electrode unit and the counter electrode prepared in Example 1 are bonded in a sandwich form, and then they are clamped with a forceps for fixing the cell, heated to 100 ° C for about 10 minutes, and cooled to room temperature.

In the assembled dye-sensitized solar cell, an electrolyte was injected through an electrolyte injection port to prepare a dye-sensitized solar cell.

≪ Comparative Example 1 &

Example 2 was carried out in the same manner as in Example 2, except that the counter electrode prepared in Step 1 of Example 1 using a pure PEDOT: PSS conductive polymer aqueous solution without metal nanoparticles was used in Step 4 of Example 2, A battery was prepared.

<Analysis>

1. Observation of the metal nanoparticle-conducting polymer composite prepared in Step 1

Example 1 step 1, a dye-sensitized solar cell, the counter electrode metal nano-particles prepared in the - to conducting to observe the polymer composite material, and coating the composite material on the glass specimen, 140 ^o C dry after a scanning electron microscope (SEM) , And the results are shown in Fig.

As shown in FIG. 2, it was confirmed that platinum nanoparticles having a size of about 20 to 40 nm were well dispersed in the PEDOT: PSS conductive polymer matrix.

Thus, according to the present invention, even when a metal nanoparticle-conductive polymer composite material is prepared by simply mixing a conductive polymer aqueous solution and a platinum aqueous solution at a low temperature and adding a reducing agent, a composite material in which platinum nanoparticles are uniformly dispersed .

<Experimental Example 1>

In order to observe the electrical characteristics of the dye-sensitized solar cell manufactured in Example 2 and Comparative Example 1, the conditions were set to AM 1.5 (1 sun, 100 mW / cm ² ) using a solar simulator, Table 1 shows the results.

Open-circuit voltage
V _OC (V) Short circuit current density
J _SC (mA / cm ² ) Fill factor
FF (%) Photoelectric conversion efficiency
PCE (%) Series resistance
R _S (Ω) ^a Example 2 0.71 16.5 44.3 5.19 101 Comparative Example 1 0.65 15.1 29.4 2.89 217

As shown in Fig. 4 and Table 1, the photoelectric conversion efficiency of Example 2 produced using the counter electrode prepared in Example 1 was improved to about 80% higher than that of Comparative Example 1, and the filling factor was 44.3% , And the short-circuit current density was 16.5 mA / cm ^{2, which} was also greatly increased compared to Comparative Example 1.

As a result, it can be seen that the surface area and the catalytic activity of the counter electrode are increased by using the metal nanoparticles and the conductive polymer together, as compared with the case where the conductive polymer is used as a counter electrode alone and the solar cell is manufactured. In addition, it can be seen that in the case of Example 2, it decreases greatly.

Claims (9)

Preparing a metal nanoparticle-conductive polymer composite material by mixing a conductive polymer aqueous solution and a metal precursor with a reducing agent (step 1);
(Step 2) spin-coating the composite material of step 1 on a flexible substrate with a substrate coated with a transparent electrode; And
(Step 3) of heat treating the flexible substrate coated with the composite material of step 2 at a temperature of 100 to 200 ° C to produce a counter electrode,
Wherein the metal nanoparticles are dispersed in the conductive polymer layer.
The method of claim 1, wherein the heat treatment in step 3 is performed at a temperature of 100 to 150 ° C.
The method according to claim 1,
The conductive polymer of step 1 may be selected from the group consisting of poly (3,4-ethylenedioxythiophene): poly (4-styrenesulfonate), poly (3,4-ethylenedioxythiophene) : polyglycol (glycerol), PANI: poly (4-styrene sulfonate), PANI: polyaniline: camphor sulfonic acid, dioxythiophene derivatives and polyanilines Wherein the at least one dye is a dye.
The method according to claim 1,
Wherein the metal is a precious metal.
5. The method of claim 4,
Wherein the precious metals are at least one selected from the group consisting of platinum, gold, silver, copper, and palladium.
delete The method according to claim 1,
Wherein the reducing agent in step 1 comprises at least one selected from the group consisting of borohydride, N ₂ H ₄ , citric acid or a salt thereof, and reducing sugar of an alkali metal or an alkaline earth metal. Gt;
The method according to claim 1,
The metal precursor of step 1 is _{H 2 PtCl 6, H 2 PtCl} 4, [Pt (NH 3) 4] Cl 2 and H ₂ Pt (OH) a dye-sensitized, characterized in that at least one member selected from the group consisting of ₆ (Method for manufacturing a counter electrode of a solar cell).






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