KR20070075185A - Paste composition for forming semiconductive electrode and preparation method of semiconductive electrode using the same - Google Patents

Abstract

A paste composition for forming a semiconductor electrode is provided to enable fabrication of a semiconductor electrode in which electrons flow well and the absorption quantity of dye is high by including a conductive binder and dye that are electrochemically commercial and by performing a low-temperature sintering process at a temperature of 80~200 °C. A paste composition for forming a semiconductor electrode includes metal oxide powder, dye, a conductive binder and a solvent. The paste composition can include metal oxide powder of 20~50 weight percent, dye of 0.1~10 weight percent with respect to the metal oxide powder, a conductive binder of 1~10 weight percent, and a solvent of the rest. The conductive binder can be selected from a group of PVDF(polyvinylidene fluoride), thiophene, PVA(polyvinyl alcohol), PEG(polyethylene glycol) and PTFE(polytetrafluoroethylene).

Description

Paste composition for forming semiconductive electrode and preparation method of semiconductive electrode using the same

The present invention relates to a paste composition for forming a semiconductor electrode and a method for manufacturing a semiconductor electrode using the same. More specifically, it is possible to perform a low-temperature firing process including an electrochemically compatible conductive binder and a dye and to increase the adsorption amount of the dye. The present invention relates to a paste composition for forming a semiconductor electrode that can increase and smoothly induce a flow of electrons generated from a dye, a method of manufacturing a semiconductor electrode using the same, a semiconductor electrode manufactured therefrom, and a solar cell including the same.

Dye-sensitized solar cells are photoelectrochemical solar cells whose main constituent materials are photosensitive dye molecules capable of absorbing visible light to produce electron-hole pairs and transition metal oxides that deliver the generated electrons.

The dye-sensitized solar cell has a structure including a semiconductor electrode, an electrolyte, and a counter electrode, and the semiconductor electrode is formed of a conductive transparent substrate and a light absorbing layer including a metal oxide and a dye.

The semiconductor electrode is generally formed by forming a metal oxide film on a substrate and then adsorbing a dye on the surface of the film. Specifically, the paste composition of the metal oxide is applied on a transparent substrate to form a metal oxide film through a baking process at 350 ° C. to 500 ° C., and the film is impregnated with a solution in which the dye is dissolved for a predetermined time. It is formed by allowing dye to adsorb on the surface of the film.

The reason why the firing process of the metal oxide is performed at a high temperature of 350 ° C. to 500 ° C. is because the existing binder component constituting the paste composition can be removed only by heat treatment at 350 ° C. or higher. The binder is electrochemically acting as an insulator, thereby preventing the flow of electrons generated in the dye.

For this reason, the manufacturing process of the conventional semiconductor electrode requires high-temperature firing at 350 ° C to 500 ° C, and therefore, there is a problem that it is difficult to apply to a flexible plastic substrate, which is recently attracting attention.

In this regard, Japanese Laid-Open Patent Publication No. 2002-93475 discloses a dye-sensitized solar cell by dispersing TiO ₂ fine particles in a liquid containing polyethylene glycol to prepare a paste composition, then applying it onto a pattern, and preliminarily drying and baking at 100 to 350 ° C. Disclosed is a content for producing a cell.

However, since the disclosed patent forms a metal oxide film on a substrate as in the prior art, a dye is adsorbed in the film state to produce a semiconductor electrode, and thus the amount of dye adsorbed to the metal oxide particles cannot be utilized. Compared to the optical cross-section of the light (light) is very small, there is a problem that it is difficult to apply to the still flexible substrate by performing the firing process at a relatively high temperature of 100 to 350 ℃.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention including an electrochemically stable conductive binder and dye paste capable of manufacturing a semiconductor electrode with an increased amount of dye adsorption through a low-temperature baking process It is to provide a composition.

Another object of the present invention is to provide a method for manufacturing a semiconductor electrode which can easily and inexpensively manufacture a semiconductor electrode having a high adsorption amount of dye and a smooth flow of electrons using the paste composition.

It is still another object of the present invention to provide a semiconductor electrode manufactured by the above manufacturing method and showing improved manufacturing processability and photoelectric conversion efficiency, and a solar cell including the same.

One aspect of the present invention for achieving the above object is a metal oxide powder; dyes; Conductive binders; And a paste composition for forming a semiconductor electrode comprising a solvent.

Another aspect of the invention comprises the steps of applying a paste composition according to the present invention on a transparent substrate coated with a conductive material; And baking the applied composition at a low temperature for 30 minutes to 5 hours at a temperature of 80 to 200 ° C. to form a light absorption layer.

Another aspect of the invention relates to a semiconductor electrode produced by the method.

Another aspect of the invention is a semiconductor electrode according to the present invention; An electrolyte layer; And a dye-sensitized solar cell having a counter electrode.

Hereinafter, the present invention will be described in more detail.

The present invention is a metal oxide powder; dyes; Conductive binders; And it provides a paste composition for forming a semiconductor electrode comprising a solvent.

The paste composition for forming a semiconductor electrode of the present invention includes a conductive binder which is electrochemically compatible as a binder component. The conductive binder of the present invention is a binder remaining in the film after a low temperature baking process of 200 ° C. or lower, and unlike the conventional binder that acts as an insulator and prevents the flow of electrons generated in the dye, it is electrochemically It is stable, rather it induces a smooth flow of electrons. Therefore, the paste composition of the present invention can perform a firing process at a low temperature of 200 ° C. or less, and thus there is an advantage that it can be applied to a flexible substrate such as plastic without limitation.

The paste composition of the present invention further comprises a dye together with the metal oxide powder. In the conventional dye-sensitized solar cell, since the metal oxide film is first formed on the substrate and then the dye is adsorbed in the film state, the dye-sensitized solar cell does not utilize the entire surface area of the metal oxide particles, and thus the amount of dye adsorption to the dye electrode. There was a problem that only 1/10 of the optical cross-section of the light. Therefore, in the present invention, when the paste composition for forming the semiconductor electrode is prepared, the dye is added in advance in the slurry dispersion step, so that the dye can be evenly adsorbed onto the entire surface of the metal oxide particles.

Such paste composition of the present invention is 20 to 50% by weight of the metal oxide powder; 0.1 to 10% by weight of the dye, based on the powder; 1 to 10 wt% conductive binder; And a solvent as a residual amount.

In the above, when the amount of the dye used is less than 0.1% by weight relative to the metal oxide powder, the effect of the injection of the excitation electrons into the metal oxide conduction band due to the increase in the adsorption amount of the desired dye and the sufficient light absorption of the dye, etc. On the contrary, when the amount of dye used exceeds 10% by weight, excess dye adsorbed on the TiO ₂ surface may interfere with the flow of electrons, thereby reducing the efficiency of the device.

In addition, when the conductive binder is used in less than 1% by weight, it is impossible to achieve the inherent adhesion effect of the binder and the effect of facilitating the flow of electrons. This can reduce the interaction between the light energy and the dye, leading to a decrease in efficiency.

As the conductive binder of the present invention, a binder capable of inducing conductivity while being electrochemically stable in a binder remaining after low temperature baking at 200 ° C. or lower may be used. Specific examples include polyvinylidene fluoride (PVDF), thiophene, polyvinyl alcohol (PVA), polyethylene glycol (PEG), polytetrafluoroethylene (PTFE), and the like. It is most preferred to use leaden fluoride (PVDF).

Polyvinylidene fluoride (PVDF) is a binder generally used for the positive electrode of lithium secondary batteries. It is excellent in adhesive strength and electrochemically stable, so it does not react even when charging and discharging continues. There is an advantage in the degree of dispersion to fully satisfy the binder conditions of the present invention described above.

As the solvent for dissolving the binder, conventional organic solvents or water, which are conventionally used in the art, can be used without limitation. Preferably, the conductive binder can be dissolved well while the volatilization is good and the viscosity of the paste can be properly adjusted. It is good to be able to adjust. Specifically, aliphatic hydrocarbon solvents such as hexane and heptane; Aromatic hydrocarbon solvents including pyridine, quinoline, anisol, mesitylene and xylene; Methyl isobutyl ketone, N-methyl-2-pyrrolidone (NMP), 1-methyl-2-pyrrolidinone (1-methyl-2-pyrrolidinone), Ketone-based solvents including cyclohexanone and acetone; Ether-based solvents including tetrahydrofuran and isopropyl ether; Alcohol-based solvents including isopropyl alcohol, butyl alcohol and t-butanol; Amide solvents including dimethylacetamide and dimethylformamide; Silicon-based solvents; Nitrile solvents including acetonitrile; water; And one or more selected from the group consisting of a mixture of the solvents may be used, these may be used alone or in combination of two or more.

More preferably, the solvent comprises N-methyl-2-pyrrolidone (NMP), acetonitrile, t-butanol, acetone, dimethylformamide, isopropyl alcohol and ethyl acetate. One or more kinds selected from may be used, and most preferably, N-methyl-2-pyrrolidone (NMP) may be used.

As the metal oxide powder used in the paste composition of the present invention, one or more selected from the group consisting of titanium oxide, niobium oxide, hafnium oxide, indium oxide, tin oxide and zinc oxide may be used, and these may be used alone or in combination of two or more thereof. Can be used. Preferably, titanium oxide (TiO ₂ ) may be used.

In addition, such metal oxides preferably have a large surface area in order to absorb more light from the dye adsorbed on the surface and to improve the degree of adsorption with the electrolyte layer. Thus, quantum dots, nano dots, nanotubes, nanowires, and nanobelts Or nanomaterials consisting of nanoparticles. The particle size of such metal oxides is preferably in the range of 5 to 400 nm.

The dye used in the paste composition of the present invention can be used without limitation as long as it is generally used in the field of solar cells, but ruthenium complex is preferable. However, as long as it has a charge separation function and exhibits a sensitive action, it is not particularly limited, and in addition to ruthenium complexes, for example, xanthine-based pigments such as rhodamine B, rosebengal, eosin, and erythrosin; Cyanine-based pigments such as quinocyanine and cryptocyanine; Basic dyes such as phenosafranin, capriblue, thiosine, and methylene blue; Porphyrin-based compounds such as chlorophyll, zinc porphyrin, and magnesium porphyrin; Other azo pigments; Phthalocyanine compounds; Complex compounds such as Ru trisbipyridyl; Anthraquinone pigments; And polycyclic quinone dyes. These may be used alone or in combination of two or more thereof. As the ruthenium complex, RuL ₂ (SCN) ₂ , RuL ₂ (H ₂ O) ₂ , RuL ₃ , RuL _2, etc. may be used (wherein L is 2,2′-bipyridyl-4,4′-dica). Carboxylate and the like).

Furthermore, at least one other additive such as a plasticizer, leveling agent, leveling agent, antifoamer and the like is added to the semiconductor composition for forming a semiconductor electrode in the range of 0.1 to 5% by weight within the range that does not impair the physical properties of the composition. Can be added.

Other additives such as the plasticizer, the leveling agent, the leveling agent, and the defoamer may be the same or similar to those conventionally used in the conventional paste composition.

The paste composition of the present invention may be prepared by dissolving a metal oxide powder and a dye in a primary solvent to prepare a slurry dispersion solution, and then adding a mixed solution of a conductive binder and a secondary solvent to the slurry dispersion solution to uniformly mix the same. Can be. That is, the paste is prepared by first adsorbing the dye to the metal oxide particles in a slurry dispersed state and then adding a conductive binder. In this case, as the primary solvent and the secondary solvent, the above-described conventional solvents may be used without limitation, and the same or different solvents may be used. Preferably, N-methyl-2-pyrrolidone (NMP) is used as both the primary solvent and the secondary solvent.

Meanwhile, the present invention provides a new method for manufacturing a semiconductor electrode using the paste composition.

Specifically, the present invention,

Applying the paste composition of the present invention onto a transparent substrate coated with a conductive material; And

It provides a method for manufacturing a semiconductor electrode comprising the step of forming a light absorption layer by low-temperature baking the applied composition at a temperature of 80 to 200 ℃ for 30 minutes to 5 hours.

The method for manufacturing a semiconductor electrode according to the present invention is carried out using a conductive binder which is electrochemically stable as a binder remaining in the film after low temperature firing and does not disturb the flow of electrons generated in the dye. Therefore, according to the manufacturing method of the present invention, the semiconductor electrode can be manufactured without any problem even at low temperature firing process at 80 to 200 ° C., as well as glass substrates and silica substrates, as well as substrates of various materials such as flexible substrates such as plastics. There is an advantage that can be easily applied.

In addition, the method of manufacturing a semiconductor electrode of the present invention is carried out using a paste composition containing a dye and a metal oxide at the same time. As a result, by increasing the adsorption amount of the dye to the entire surface of the metal oxide particles, it is possible to increase the absorption of light as much as possible, and after forming a metal oxide layer, it is necessary to proceed separately to adsorb the dye on the surface of the oxide layer It is economical in terms of manufacturing process.

As the substrate to which the method for manufacturing a semiconductor electrode of the present invention can be applied, any substrate can be used without particular limitation, and specifically, a glass substrate, a silica substrate, a plastic substrate, or the like can be used.

Examples of the conductive material coated on the substrate include indium tin oxide (ITO), florin doped tin oxide (FTO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , SnO ₂ -Sb ₂ O ₃ , and the like. The coating method may be a general coating method such as spraying, spin coating, dipping, printing, doctor blading, sputtering.

In addition, a general coating method such as tape casting (doctor blading), screen printing, spin coating, dipping, and the like may be used as a method of applying the paste composition.

The composition applied on the transparent substrate may be dried according to a conventional method and then calcined at a low temperature for 30 minutes to 5 hours at a temperature of 80 to 200 ° C. to form a light absorbing layer, preferably at about 90 to 150 ° C. It may be calcined for 1 to 3 hours. When the firing step is performed at a temperature below 80 ° C., the organic solvent may not be completely removed, and thus the adhesiveness between the binder and the substrate may be deteriorated and current may not flow to the electrode, and the firing step may be performed at a temperature above 200 ° C. In the case of performing, there is a difficulty in applying the flexible substrate, economical effects cannot be obtained in terms of manufacturing cost, and there is a problem in that the efficiency of the device may be lowered due to damage due to heat of the dye.

On the other hand, the light absorption layer may be formed in a planar structure or uneven structure to increase the surface area to improve the degree of adsorption with the electrolyte layer. The concave-convex structure may include a step shape, a needle shape, a mesh shape, a ska shape, and the like, but is not limited thereto.

In addition, the light absorption layer may be formed as a single layer, but in order to improve light transmittance, it may be formed as a two layer using two paste compositions containing two kinds of metal oxides having different particle sizes. Preferably, the paste composition including the metal oxide having a size of 5 to 50 nm is stacked to have a thickness of 10 to 20 μm, and the paste composition containing the metal oxide having a size of 100 to 400 nm to have a thickness of 3 to 5 μm to form a double layer structure.

The present invention provides a semiconductor electrode manufactured by the above-described manufacturing method.

Specifically, the semiconductor electrode of the present invention, a transparent electrode coated with a conductive material on the substrate; And a light absorption layer formed on the transparent electrode using the paste composition of the present invention.

The semiconductor electrode according to the present invention not only has excellent manufacturing processability but also has a high adsorption amount of dyes to metal oxides and a smooth flow of electrons. Therefore, when used in dye-sensitized solar cells, light absorption is increased to improve photoelectric conversion efficiency. You can.

The dye-sensitized solar cell including the semiconductor electrode according to the present invention includes a semiconductor electrode, an electrolyte layer, and an opposite electrode.

The electrolyte layer is made of an electrolyte solution, for example, an acetonitrile solution of iodine, an NMP solution, 3-methoxypropionitrile, and the like may be used, but is not limited thereto. Can be used.

The counter electrode can be used without limitation as long as it is a conductive material. If the conductive material is provided on the side facing the semiconductor electrode, this can also be used. However, it is preferable to use an electrochemically stable material as an electrode, and it is preferable to use platinum, gold, carbon, etc. specifically ,.

In order to improve the catalytic effect of the redox, the side facing the semiconductor electrode is preferably in a fine structure, and the surface area thereof is increased. For example, it is preferable that platinum is in a platinum black state and carbon is in a porous state. The platinum black state can be formed by anodic oxidation of platinum, platinum chloride treatment, or the like, and carbon in the porous state can be formed by sintering of carbon fine particles or firing of an organic polymer.

The manufacturing method of the dye-sensitized solar cell according to the present invention having such a structure is not particularly limited, and any method known in the art can be used without limitation.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the protection scope of the present invention.

[ Example  1: Preparation of Paste Composition for Semiconductor Electrode Formation]

3.3 g of TiO ₂ powder having a particle diameter of 13 nm and 50 mg of ruthenium dithiocyanate 2,2'-bipyridyl-4,4'-dicarboxylate were used as a primary solvent, N-methyl-2-pyrrolidone (NMP 5g), followed by stirring for 30 minutes with ultrasonic to prepare a slurry dispersion solution. Separately, 1.76 g of polyvinylidene fluoride (PVDF) was mixed with 10 g of N-methyl-2-pyrrolidone (NMP) as a secondary solvent, followed by stirring to prepare a mixed solution. 2.53 g of the mixed solution was added to the slurry dispersion solution, followed by stirring for 30 minutes to obtain a paste composition according to the present invention.

[ Example  2: Fabrication of Semiconductor Electrodes]

Florin doped tin oxide (FTO) was applied onto the plastic substrate using a sputter. Thereafter, the paste composition obtained in Example 1 was applied by screen printing and baked at 120 ° C. for 1 hour to form a light absorption layer having a thickness of about 20 μm, thereby manufacturing a semiconductor electrode according to the present invention.

[ Example  3: manufacture of solar cells]

A counter electrode was prepared by coating platinum on the surface of a conductive transparent plastic substrate coated with ITO. Next, the opposite electrode which is an anode and the semiconductor electrode obtained in Example 2 were assembled as a cathode. When assembling the positive electrode, the platinum layer and the light absorbing layer faced each other so that the conductive surface of the positive electrode and the negative electrode was brought into the battery. At this time, between the anode and the cathode was placed about 40 microns thick polymer made of SURLYN (manufactured by Du Pont), the two electrodes were brought into close contact with each other at about 1 to 3 atm on a heating plate of about 100 to 140 ℃. The polymer was in close contact with the surfaces of the two electrodes by heat and pressure.

Next, the electrolyte solution was filled in the space between the two electrodes through the micropores formed on the surface of the anode to complete the dye-sensitized solar cell according to the present invention. The electrolyte solution was 0.6M 1,2-dimethyl-3-octyl-imidazolium iodide (1,2-dimethyl-3-octyl-imidazolium iodide), 0.2M LiI, 0.04MI ₂ and It was used as an electrolyte solution of the ^-: (4-tert- butyl-pyridin-TBP) to which I ³ dissolved in acetonitrile ^- / I 0.2M 4-tert- butyl-pyridine.

As described above, the paste composition of the present invention includes an electrochemically compatible conductive binder and a dye to prepare a semiconductor electrode having a high adsorption amount of dye and a smooth flow of electrons through a low temperature baking process at 80 to 200 ° C. Since it is possible to easily apply to a flexible plastic substrate, there is an advantage to greatly improve the manufacturing process and photoelectric conversion efficiency of the semiconductor electrode and solar cell manufactured therefrom.

Claims (16)

Metal oxide powders; dyes; Conductive binders; And A paste composition for forming a semiconductor electrode comprising a solvent. The method of claim 1 wherein the paste composition is 20 to 50 wt% metal oxide powder; 0.1 to 10 weight percent dye based on the powder; 1 to 10 wt% conductive binder; And A paste composition comprising a solvent as a residual amount. The method of claim 1, wherein the conductive binder is selected from the group consisting of polyvinylidene fluoride (PVDF), thiophene, polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polytetrafluoroethylene (PTFE). Paste composition, characterized in that selected. The paste composition of claim 3, wherein the conductive binder is polyvinylidene fluoride (PVDF). The method of claim 1, wherein the solvent is aliphatic hydrocarbon solvent (aliphatic hydrocarbon solvent) such as hexane, heptane; Aromatic hydrocarbon solvents including pyridine, quinoline, anisol, mesitylene and xylene; Methyl isobutyl ketone, N-methyl-2-pyrrolidone (NMP), 1-methyl-2-pyrrolidinone (1-methyl-2-pyrrolidinone), Ketone-based solvents including cyclohexanone and acetone; Ether-based solvents including tetrahydrofuran and isopropyl ether; Alcohol-based solvents including isopropyl alcohol, butyl alcohol and t-butanol; Amide solvents including dimethylacetamide and dimethylformamide; Silicon-based solvents; Nitrile solvents including acetonitrile; water; And at least one selected from the group consisting of a mixture of the solvents. The method of claim 5, wherein the solvent is N-methyl-2-pyrrolidone (NMP), acetonitrile, t-butanol, acetone, dimethylformamide, isopropyl alcohol and ethyl acetate Paste composition, characterized in that at least one selected from the group consisting of. 7. The paste composition of claim 6, wherein the solvent is N-methyl-2-pyrrolidone (NMP). The paste composition of claim 1, wherein the metal oxide is at least one selected from the group consisting of titanium oxide, niobium oxide, hafnium oxide, indium oxide, tin oxide and zinc oxide. The method of claim 1, wherein the dye is selected from ruthenium complexes; Xanthine pigments including rhodamine B, rosebengal, eosin, erythrosin; Cyanine-based pigments including quinocyanine and cryptocyanine; Basic dyes, including phenosafranin, capriblue, thiocine, methylene blue; Porphyrin-based compounds including chlorophyll, zinc porphyrin, magnesium porphyrin; Azo pigments; Phthalocyanine compounds; Complexes including Ru trisbipyridyl; Anthraquinone pigments; And at least one member selected from the group containing polycyclic quinone dyes. The paste composition of claim 1, wherein the composition further comprises at least one additive selected from the group consisting of plasticizers, leveling agents, leveling agents, and defoamers. Applying the paste composition according to claim 1 on a transparent substrate coated with a conductive material; And Baking the applied composition at a low temperature for 30 minutes to 5 hours at a temperature of 80 to 200 ° C. to form a light absorption layer. 12. The method of claim 11, wherein the substrate is a glass, plastic, or silica substrate. 12. The method of claim 11, wherein the conductive material comprises indium tin oxide (ITO), florin doped tin oxide (FTO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , and SnO ₂ -Sb ₂ O ₃ . A method for producing a semiconductor electrode, characterized in that selected from the group. The method of claim 11, wherein the method of applying the paste composition is selected from the group consisting of tape casting (doctor blading), screen printing, spin coating, and dipping. The semiconductor electrode manufactured by the manufacturing method of any one of Claims 11-14. The semiconductor electrode of claim 15; An electrolyte layer; And Dye-sensitized solar cell comprising a counter electrode.