KR20100074032A - Production method of the counter electrode for dssc - Google Patents

Abstract

PURPOSE: A method for manufacturing a counter electrode for a dye-sensitized solar cell is provided to improve profitability and efficiency by firmly coating a plating layer on a conductive flexible substrate. CONSTITUTION: A conductive substrate is plated with platinum by using pulse power of 5 to 20 Hz for 5 to 60 seconds under current density of 0.3 to 2ASD and a temperature of 40 to 60 degrees centigrade in a Pt plating solution of pH 1-2. Ti is used as an anode. A substrate plated with platinum is thermally processed at a temperature of 100 to 500 degrees centigrade for 5 to 60 minutes. A surfactant of 0.5 to 2 weight% is added to the plating solution. The surfactant is a polyethylene oxide or polypropylene oxide surfactant.

Description

Manufacturing method of counter electrode for dye-sensitized solar cell {Production Method of the Counter Electrode for DSSC}

The present invention relates to a manufacturing method of a counter electrode for a dye-sensitized solar cell, and more particularly to a manufacturing method of a counter electrode plated with platinum.

Conventional dye-sensitized solar cells, unlike silicon solar cells, are mainly composed of photosensitive dye molecules capable of absorbing visible light to produce electron-hole pairs, and transition metal oxides for transferring the generated electrons. It is a photoelectrochemical solar cell made of a constituent material.

In general, a dye-sensitized solar cell is a semiconductor electrode coated with a nanoparticle oxide adsorbed with a dye molecule on a transparent conductive substrate (called a "transparent electrode"), and an opposite electrode coated with platinum or carbon on a transparent conductive substrate ("counter electrode"). And an electrolyte layer filled therebetween.

The transparent electrode is manufactured by coating a colloidal solution of nanoparticle oxide on a conductive glass substrate and heat-treating in an electric furnace at 450 to 500 ° C.

The counter electrode is a method of coating or depositing a platinum compound dissolved in a solvent on a conductive glass substrate, followed by heat treatment in an electric furnace at 450 to 500 ° C. (immersion sintering method), DC plating of a conductive substrate in a platinum solution (DC plating method), and deposition method. It is produced through the back. In the case of the sintering method, the photoelectric characteristics of the counter electrode can be obtained only by performing a relatively high temperature heat treatment (sintering). In the case of the sputtering method, it is difficult to control the deposition thickness as well as expensive vacuum deposition equipment. After deposition, there is also a difficulty in performing high temperature sintering at the same temperature. In addition, the DC method has a merit that high temperature heat treatment (sintering) can be omitted, but the adhesion (physical stability) of the plating layer is very weak, so it must be handled with great care during the manufacturing process of the solar cell, and adversely affect the life of the completed solar cell. There is a problem. In addition, according to the DC method, it was impossible to apply to a flexible substrate because of the weak adhesion of the plating layer.

The present invention is a high temperature heat treatment It is an object of the present invention to provide a method for manufacturing a counter electrode for an economical and efficient dye-sensitized solar cell based on a technique of firmly coating a platinum layer on a conductive glass substrate without a process.

In addition, an object of the present invention is to provide a method for manufacturing a glass substrate and a counter electrode for a flexible dye-sensitized solar cell, which is economically and highly efficient by guaranteeing a solid coating of a platinum layer on a conductive flexible substrate.

The present invention for solving the above problems, (A) Ti as an anode, in a platinum (Pt) plating solution of pH 1 ~ 2, the temperature of 5 ~ 20Hz at a temperature of 40 ~ 60 ℃, current density 0.3 ~ 2ASD conditions Plating step of plating the conductive substrate for 5 to 60 seconds with a pulse power source; And (B) heat-treating the platinum-plated substrate at 100 to 500 ° C. for 5 to 60 minutes. At this time, in order to increase the efficiency of the manufacturing, before the plating step (A), it may further include a pre-treatment process of degreasing and washing the substrate again, and a post-treatment process of washing the plated substrate.

By plating with a pulsed power supply, it is possible to obtain an effect of improving the adhesion of the plating layer which is much superior to the conventional DC plating method. At this time, the current density and the plating time are in inverse proportion to each other. If the pulse power is less than 5Hz, the effect of increasing the adhesion of the plated layer is insignificant, and if the pulse power is more than 20Hz, the pulse power supply becomes expensive compared to the effect of increasing the adhesion, resulting in low economic efficiency.

The platinum-plated substrate is heat-treated at 100 to 500 ° C. for 5 to 60 minutes. The heat treatment temperature is sufficient to obtain a sufficient effect even 100 ~ 250 ℃, but does not exclude the temperature higher.

On the other hand, the present inventors found that when 0.5 to 2% by weight of surfactant is added to the plating solution during pulse plating according to the present invention, the size of the plated particles becomes uniform and the distribution of the plated particles becomes uniform. If the surfactant is less than 0.5% by weight, the plated particle control effect is inferior, and if it is more than 2% by weight, the increase of plated particle control effect is insignificant. The surfactant may be a polyethylene oxide (hereinafter referred to as "EO") system or a polypropylene oxide (hereinafter referred to as "PO") system.

In the present invention, the substrate coated with the conductive material may be glass or a flexible synthetic resin material. In the case of synthetic resin, polyethylene terephthalate, polycarbonate, polyimide, or polyethylene naphthalate is preferable.

The conductive material may be fluorine doped tin oxide, indium tin oxide or other metal. However, the conductive material itself is not limited to the present invention because it is irrelevant to the spirit of the present invention.

According to the present invention, it is possible to provide a counter electrode for a dye-sensitized solar cell coated with a platinum layer, which is much more economical than a conventional method for high temperature sintering a platinum layer on a conductive substrate.

In addition, according to the present invention, ITO glass substrates or flexible conductive materials, which were not applicable to conventional high temperature firing results, could not be applied. Plastic substrates can be applied to dye-sensitized solar cells.

According to the present invention, it is possible to obtain a counter electrode having adhesion superior to that of the conventional high temperature sintering method or DC plating method, so that the dyeing can reduce excessive attention for protecting the platinum layer in the manufacturing process of the solar cell.

In addition, by the present invention it is possible to make the plating particles and the plating more uniform, it is possible to manufacture a dye-sensitized solar cell which is inexpensive and excellent in photochemical properties and stable for long-term use.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and pre-experiments and examples. However, these drawings and embodiments are only examples for easily explaining the contents and scope of the technical idea of the present invention, and thus the technical scope of the present invention is not limited or changed. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention based on these examples.

In the following examples, the FTO substrate was manufactured, but since it was confirmed that the same effect can be obtained regardless of the material of the substrate in a preliminary experiment, the present invention is not limited to the material of the substrate.

<Pretest>

Pre-experimental experiments were performed using conventional DC plating methods to estimate the thickness and heat treatment temperature range of Pt plating layers available for electroplating.

(1) Confirmation of possible Pt plating layer thickness

A Pt plating layer was formed on the FTO glass substrate at 5 kW and 25 kW to form a counter electrode, and the light conversion efficiency of the counter electrode was examined (not shown in the diagram).

As a result of the preliminary experiment, it was confirmed that the heat treatment temperature of 100 ° C., 150 ° C. or 200 ° C., and the thickness of the Pt plating layer 5 μs or 25 μs showed similar or better characteristics to the counter electrode by the conventional deposition-sintering method. In particular, the thinner the thickness of the Pt plated layer, the better the results. Even though no additional verification experiment was performed, it could be estimated that a sufficient effect could be obtained even in the case of a Pt plated layer of 1 ~ 30Å.

(2) Confirmation of possible substrate material and heat treatment temperature range

① After manufacturing the counter electrode with different Pt plating thickness on FTO glass substrate , the resistance value was measured to determine the optimum heat treatment temperature range (not shown in the diagram).

As a result of the preliminary experiments, it was found that the resistance value after sintering at 200 ° C. was the lowest, and that the resistance value was sufficiently low even at 250 ° C. or lower (and therefore, of course, below the conventional sintering temperature). However, even if the sintering temperature (400 ~ 500 ℃) by the conventional sintering method was applied, there was almost no difference in characteristics with the counter electrode manufactured by the sintering method.

Low resistance value is advantageous in terms of efficiency increase because it can reduce the resistance inside the solar cell during photoconversion.

(2) A counter electrode was formed by forming a Pt plating layer having a thickness of 5 에 on an ITO glass substrate , and the light conversion efficiency of the counter electrode was measured (not shown).

As a result, it was confirmed that even if the ITO substrate was heat treated at 250 ° C., which was slightly lower than 300 ° C., the performance characteristics were similar or better than those of the conventional deposition-sintering method or the FTO substrate.

For reference, when the heat treatment at a high temperature (300 ℃ or more), the substrate is turned into a resistor, the performance characteristics deteriorate sharply, it is determined that the indium (Indium) of the substrate evaporates due to the high temperature treatment.

③ Pt plating the conductive plastic substrate (ITO Plastic Film, PLASTICS Co., Ltd., sheet resistance 400Ω / square) with thickness of 5 에 according to DC method and heat-processing at 150 ℃ to manufacture the counter electrode, and improve the light conversion efficiency of the counter electrode. It measured (not shown in figure).

As a result, when the electroplating method is applied to the conductive plastic substrate, it was confirmed that the electrode having excellent performance characteristics rather than the counter electrode by the conventional deposition-high sintering method.

<Examples>

Comparative Example 1: Preparation of the counter electrode substrate by platinum solution deposition-sintering method

1 to 2 ml of a Pt solution (25 mM H ₂ PtCl ₆ in 2-propanol) was dropped on the FTO conductive substrate 15 mm × 15 mm, followed by sintering at 400 to 500 ° C. for 30 minutes to form a Pt layer (FIG. 1). For reference, it was very difficult to control the uniformity of the thickness of the Pt layer according to the concentration of Pt solution and the amount (or the number of times) dropped.

Comparative Example 2 Fabrication of Counter Electrode Substrate by DC Plating

The counter electrode was manufactured by performing Pt plating on a FTO substrate using DC power under the conditions of Table 1 and performing heat treatment at 200 to 250 ° C. for 30 minutes. At this time, the concentration and pH of the plating liquid was controlled to maintain the range of the following table.

The plating thickness can be determined by adjusting the plating time or the current density, and the Pt layer was formed at a thickness of 5 to 10 angstroms under the above conditions.

Example 1 Fabrication of Counter Electrode Substrate by Pulse Plating

A counter electrode was manufactured in the same manner as in Comparative Example 2 except that a pulse power source of 10 Hz was applied instead of a DC power source.

Example 2 Preparation of Counter Electrode Substrate by Pulse Plating Method-Surfactant Addition

A counter electrode was prepared in the same manner as in Example 1, except that 1 wt% of 1-naphthyl-polyethylene oxide was added to the plating solution as a surfactant.

For reference, in this embodiment, 1-naphthyl-polyethylene oxide was used, but according to a preliminary experiment, biphenyl-4,4'-di (polyethylene oxide) of EO series, 4- (1-methyl-1-phenyl-) Ethyl) -phenyl-polyethylene oxide, 4-methyl-phenyl-polyethylene oxide, PO-based biphenyl-4,4'-di (polypropylene oxide), 4- (1-methyl-1-phenyl-ethyl) -phenyl Similar effects were obtained even when -polypropylene oxide and 4-methyl-phenyl-polypropylene oxide were used.

<Result analysis>

(1) Adhesion test of Pt plating

Before and after the heat treatment, the Pt plating layer of the counter electrode was rubbed by 10 mm at the same pressure by using a cotton swab to test whether the plating layer appeared on the cotton swab (Table 2). In the case of Comparative Example 1, in the case of Comparative Example 1, the deposited Pt solution is in a dried state, and in Comparative Example 2 and Examples, the plating is completed and washed after being washed.

As can be seen from the table, after the heat treatment, the plated layer of the counter electrode according to the embodiment of the present invention exhibited the same strong adhesion as that of Comparative Example 1 according to the conventional method sintered at a high temperature. However, the plating layer of the counter electrode according to the embodiment exhibited almost the same adhesive strength as after the heat treatment even before the heat treatment. On the other hand, in the case of the conventional sintering method, there was almost no adhesion before heat treatment, and the adhesion of the plated layer by the DC method showed moderate adhesion.

Therefore, according to the present invention, since the plating layer is strongly attached before and after heat treatment, the coating layer is strongly attached to the solar cell fabrication process, and thus the coating layer adhesion is the same as that of the conventional high temperature sintering process. In the process of using the battery, it can be expected that the electric and life characteristics will be much better than the solar cell by the DC method.

(2) Analysis of electron microscope of Pt plating layer

The surface of the counter electrode subjected to the heat treatment was observed with an electron microscope (FIG. 2).

As can be seen in the photo, in the case of Example 1 (B of Fig. 2) and Example 2 (C of the present invention) the number of particles of Pt plated compared to the conventional plating layer (A of Fig. 2) by the DC method Not only were they extremely high, but the distribution of particles was very uniform.

This makes it possible to expect that the solar cell to which the counter electrode by the pulse plating method according to the present invention will show excellent electrical characteristics compared with the counter electrode according to the conventional DC method.

(3) Characteristic test of solar cell

Using the counter electrode thus prepared, a conventional dye-sensitized solar cell was manufactured, and the light conversion efficiency of the manufactured solar cell was measured and shown in Table 3.

Each unit in Table 3 has the following meaning.

① Voc: It is an open voltage, the voltage appearing on both ends of solar cell when current is 0. It is the maximum voltage that can be obtained from solar cell.

② Jsc: It is the current density. It means the current flowing per certain area as the current flowing when the voltage across the solar cell is 0.

③ FF: Defined as the ratio of output to product of open voltage and short circuit current, and corresponds to the largest rectangular area that can be filled in the current-voltage curve. Along with Voc and Isc (Jsc), it is an important parameter that directly affects battery efficiency.

④ Efficiency: It is defined as the ratio of output energy to energy incident from the solar cell as the most important factor that indicates the performance of the solar cell and is expressed as the following equation.

η (efficiency,%) = (Voc × Isc × FF) / P _in

{Voc is Open circuit voltage, Isc is Short circuit current, FF is Fill Factor, η is Efficiency}

As can be seen from Table 3, this means that the solar cell to which the counter electrode according to the pulse plating method according to the present invention is applied is based on the conventional deposition sintering method (Comparative Example 1) or on the average compared with the conventional DC method (Comparative Example 2). The same or better electrical properties were shown. In particular, it can be seen that the performance (efficiency) of the solar cell having an industrial significance is significantly increased compared to the comparative example.

1 is a photograph showing the manufacturing process of the counter electrode by the conventional deposition-sintering method.

Figure 2 is an electron micrograph of the surface of the counter electrode prepared by Comparative Example and Example.

Claims (5)

(A) Platinum-plating a conductive substrate for 5 to 60 seconds using Ti as the anode and a pulsed power source of 5 to 20 Hz at a temperature of 40 to 60 ° C and a current density of 0.3 to 2 ASD in a Pt plating solution with a pH of 1 to 2. Plating step; (B) heat-treating the platinum plated substrate at 100 to 500 ° C. for 5 to 60 minutes; Method for producing a counter electrode for a dye-sensitized solar cell comprising a. The method of claim 1, Method for producing a counter-electrode for dye-sensitized solar cell, characterized in that 0.5 to 2% by weight of the surfactant is added to the plating solution. The method of claim 2, The surfactant is a method of manufacturing a counter electrode for a dye-sensitized solar cell, characterized in that the polyethylene oxide or polypropylene oxide-based surfactant. 4. The method according to any one of claims 1 to 3, The conductive substrate is a manufacturing method of the counter electrode for a dye-sensitized solar cell, characterized in that the glass substrate or a substrate made of a synthetic resin material. The method of claim 4, wherein The synthetic resin is a method for producing a counter electrode for a dye-sensitized solar cell, characterized in that the polyethylene terephthalate, polycarbonate, polyimide, or polyethylene naphthalate.

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