KR101118187B1 - Method for forming Nano-Sized Blocking layer and Dye-Sensitized Photovoltaic Cell Having the Blocking Layer of Metal Oxide and Method for Manufacturing the Same - Google Patents

Abstract

The present invention relates to a method for forming a nano-sized metal oxide barrier layer, a solar cell having the barrier layer and a method of manufacturing the same.
The present invention comprises the steps of preparing a dispersion solution by uniformly dispersing the metal oxide nanoparticles in a solvent; Forming a blocking layer by electrospraying the dispersion solution so that the nanoparticles are stacked on the conductive substrate; Forming a porous membrane for dye-sensitization on top of the barrier layer; And adsorbing a dye on the porous membrane.

Description

Method for forming Nano-Sized Blocking layer and Dye-Sensitized Photovoltaic Cell Having the Blocking Layer of Metal Oxide and Method for Manufacturing the Same}

The present invention relates to a dye-sensitized solar cell and a method for manufacturing the same, a nano-sized metal oxide blocking layer that can be directly electrosprayed nano-sized metal oxide can be manufactured in the electrode manufacturing process to improve the workability The present invention relates to a dye-sensitized solar cell provided with the method and a blocking layer thereof and a method for producing the same.

Dye-sensitized photovoltaic cells are representative of photoelectrochemical solar cells published by Gratzel et al. In Switzerland in 1991. Generally, photo-electrode, counter electrode, And an electrolyte. Among them, a semiconductor electrode is used by adsorbing metal oxide nanoparticles having a wide bandgap energy and a photosensitive dye on a transparent conductive oxide substrate, and coated with platinum (Pt) as a counter electrode.

In the dye-sensitized solar cell, when the sunlight is incident, the photosensitive dye absorbing the sunlight is in an excited state to send electrons to the conduction band of the metal oxide. The conducted electrons move to the electrode and flow to the external circuit to transfer the electric energy, and as low as the electric energy is transferred, the electrons move to the counter electrode. After that, the photosensitive dye is supplied with electrons from the electrolyte solution as much as the number of electrons transferred to the metal oxide and returned to its original state. In this case, the electrolyte used receives the electrons from the counter electrode by an oxidation-reduction reaction and transfers them to the photosensitive dye. Play a role.

Such dye-sensitized solar cells are spotlighted as next generation solar cells that can replace conventional silicon solar cells due to their low production cost. However, dye-sensitized solar cells have a disadvantage in that commercialization is difficult due to lower energy conversion efficiency than conventional silicon solar cells.

In order to increase the energy conversion efficiency of the dye-sensitized solar cell, it is important to minimize the loss of sunlight reaching the photosensitive dye of the cell and to allow the charge generated from the dye to move to each electrode smoothly.

Of the two electrodes constituting the dye-sensitized solar cell, a semiconductor electrode including metal oxide nanoparticles is generally manufactured by applying a paste containing metal oxide nanoparticles onto a conductive substrate and sintering at high temperature. .

However, due to the nature of the nanoparticles, the paste cannot be completely applied to the conductive substrate, which causes the substrate of the portion where the metal oxide nanoparticles are not applied to come into direct contact with the electrolyte, and the electrons reaching the substrate are lost to the electrolyte. As a result, the energy conversion efficiency of the battery is lowered.

In addition, in the semiconductor electrode substrate, Fluorine-doped tin oxide (FTO), which is stable even at a high sintering temperature, is used. Since the FTO has a rough surface, sunlight reaching the substrate may be scattered on the rough surface of the substrate. Since the transparency of the electrode is inferior, the incident solar light cannot be effectively transmitted to the dye.

In order to solve the above problems, by forming a blocking layer, it is possible to block direct contact between the substrate and the electrolyte and to prevent electron transfer, thereby improving energy conversion efficiency, and to prevent scattering of light due to the rough surface of the substrate. We developed a dye-sensitized solar cell with excellent light transmittance.

Solar cells having such a blocking layer have been disclosed in Patent Registration Nos. 10-854711 and 10-908243, respectively.

Patent No. 10-854711 discloses a photoelectrode for a dye-sensitized solar cell including a blocking layer and a method of manufacturing the same. Referring to the disclosed contents, a conductive substrate is prepared to manufacture a photoelectrode for a dye-sensitized solar cell, a blocking layer including a metal oxide is formed on one surface of the substrate, and then a porous film including metal oxide nanoparticles is formed on the blocking layer. After forming, a technique of adsorbing a photosensitive dye is disclosed.

The barrier layer is formed by applying heat treatment after applying the metal oxide precursor solution, but the use of the precursor solution that is harmful to the human body is not environmentally friendly, and there is a problem that the workability is deteriorated since the heat treatment process is required.

Meanwhile, referring to Patent No. 10-908243, a dye-sensitized solar cell including an electron recombination blocking layer and a method of manufacturing the same are disclosed. Looking at the disclosure,

A technique of forming a metal layer on a conductive substrate, oxidizing the metal layer to form a metal oxide film as a blocking layer, and then forming a porous metal oxide semiconductor layer on the blocking layer is disclosed.

In order to form the barrier layer, a process of forming a metal layer on a substrate through a deposition process and then oxidizing it through heat treatment is required. Therefore, the barrier layer must be subjected to a deposition process to form a metal layer, and also has to be accompanied by heat treatment for the oxidation of the metal layer, the workability is poor. In addition, since the deposition process incurs high cost, it also affects an increase in manufacturing cost, and it is difficult to increase the area.

KR 10-0908243 B KR 10-0854711 B

Accordingly, an object of the present invention is to prepare a barrier layer by directly coating a metal oxide without using a precursor solution, so a method of forming a nano-sized metal oxide barrier layer can be simplified by omitting a separate deposition process or heat treatment process. And a solar cell provided with the blocking layer and a method of manufacturing the same.

It is also an object of the present invention to provide a solar cell and a method of manufacturing the same, which can improve photoelectric efficiency by providing a nano-sized metal oxide as a blocking layer.

According to an aspect of the present invention for achieving the above object, the step of preparing a dispersion solution by uniformly dispersing the metal oxide nanoparticles in a solvent; And forming a blocking layer by electrospraying the dispersion solution so that the nanoparticles are stacked on the conductive substrate.

According to another aspect of the present invention, the metal oxide nanoparticles are uniformly dispersed in a solvent to prepare a dispersion solution; Forming a blocking layer by electrospraying the dispersion solution so that the nanoparticles are stacked on the conductive substrate; Forming a porous membrane for dye-sensitization on top of the barrier layer; And it provides a method for producing a dye-sensitized solar cell comprising the step of adsorbing a dye on the porous membrane.

The applied voltage is characterized in that 5 ~ 14kV.

The solvent is characterized in that any one of an alcohol-based organic solvent, distilled water, and a mixed solution thereof.

The metal oxide nanoparticles may be at least one selected from titanium oxide, zinc oxide, tin oxide, nirium oxide, tungsten oxide, strontium oxide, or zirconium oxide.

The metal oxide nanoparticles are characterized by having a diameter of 1 to 50 nm.

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

Dye-sensitized solar cell manufacturing method can be divided into semiconductor electrode preparation step, counter electrode preparation step, assembling of two electrodes, and electrolyte injection step, the counter electrode preparation step, assembly of the two electrodes and electrolyte injection step according to the known technology It can be done in a usual way. A feature of the invention is described in detail because it is in the step of preparing a semiconductor electrode with a nanosized metal oxide blocking layer.

The present invention is to prepare a dispersion solution by mixing a metal oxide and a solvent, to prepare a semiconductor electrode formed by forming a blocking layer by electrospraying the dispersion solution so that the nanoparticles are stacked without pores by controlling the applied voltage to improve the photoelectric efficiency of the solar cell Improve.

The metal oxide nanoparticles used in the semiconductor electrode of the present invention may use titanium oxide, zinc oxide, tin oxide, nitric oxide, tungsten oxide, strontium oxide, or zirconium oxide, among which titanium oxide nanoparticles are used. It is desirable to.

These metal oxide nanoparticles have a diameter of 1 to 50 nm, an aspect ratio of 1 to 100, and preferably have a specific surface area of 10 to 300 m ² / g. In particular, it is more preferable to use nanoparticles having a diameter of 5 to 30 nm and a high specific surface area of about 50 to 250 m ² / g.

Here, the metal oxide nanoparticles of less than 1nm is not suitable because it is difficult to make the material itself and high cost even if made. In addition, nano-sized metal oxides are used to prevent the light structure from being scattered. For metal oxide nanoparticles larger than 50 nm, the particles are large so that scattering may start and pores of more than 10 nm may occur between the particles. Inappropriate.

When such nanoparticles are used, they have a high specific surface area and thus a closed core suitable for the barrier layer is formed.

The metal oxide nanoparticles are dispersed in a solvent to prepare a dispersion in the form of a semiconductor electrode.

As a dispersion solvent for preparing such a dispersion, a metal oxide is dispersible and volatile. An alcohol-based organic solvent is used. For example, ethanol is preferable. Titanium oxide nanoparticles are usually added to an ethanol solution by 10 weight. Prepare at a concentration of%. It is preferable to make concentration of a dispersion into about 0.1-30 weight%. In addition, the dispersion solvent may be an alcohol-based organic solvent, distilled water, and a mixed solution thereof.

The metal oxide nanoparticles are dispersed in the dispersion solvent of the present invention. In general, when the metal oxide nanoparticles are in powder form, the nanoparticle powders are already aggregated with each other in the size of several hundred nm, so that the prepared dispersion is not homogeneous. do. Therefore, in order to grind the aggregated nanoparticles, for example, ultrasonic dispersion, a micro bead mill (micro bead mill) is used for mechanical dispersion.

By the dispersion operation, the aggregated metal oxide nanopowders are completely separated into the size of the primary nanoparticles to prepare a homogeneous dispersion in which the nanoparticles are separated, thereby preparing a very homogeneous dispersion in which the nanoparticles are separated.

At this time, the addition amount of the metal oxide nanoparticles dispersed in the dispersion solvent is preferably 0.1 to 30% by weight relative to the weight of the total dispersion, if less than 0.1% by weight can greatly improve the dispersibility of the particles, but the productivity is too It is not preferable because the fall and the problem of volatilization of the solvent is not preferable, the dispersion of the nanoparticles is difficult to disperse when it exceeds 30% by weight, which is not preferable to the role of the barrier layer.

Such a metal oxide nanoparticle dispersion of the present invention is a solution in which the metal oxide nanoparticles are dispersed using only an organic solvent, and do not contain an organic binder including a polymer. It does not occur and has high photoelectric conversion efficiency.

The uniform dispersion of the metal oxide nanoparticles prepared as described above is electrosprayed onto the conductive substrate to prepare a semiconductor electrode.

Conductive substrates that can be used in the present invention include a conductive glass substrate, a transparent conductive plastic substrate and a metal substrate. The conductive glass substrate or the transparent conductive plastic substrate may use a conductive thin film coated on the transparent glass or plastic substrate. As the conductive thin film, indium tin oxide (ITO), FTO, or a thin film coated with antimony tin oxide (ATO) or FTO on the ITO may be used.

As a method of spraying a dispersion solution onto such a conductive substrate, the present invention uses an electrospray method for imparting a high voltage electric field between the spray nozzle and the conductive substrate, using the nanosized metal oxide of the present invention. The specific principle of the manufacturing process of the barrier layer will be described with reference to FIG.

Referring to FIG. 1, a uniform dispersion of metal oxide nanoparticles is filled in the dispersion supply apparatus 1, and then quantitatively supplied to the injection nozzle 3 and a high voltage generator is formed between the injection nozzle 3 and the conductive substrate 4. When a high voltage is applied from (2), the uniform dispersion is blown into the fine droplets and is blown to the conductive substrate 4. As the jetted microdroplets fly to the conductive substrate 4, the organic solvent rapidly evaporates, and the metal oxide nanoparticles dispersed in the microdroplets are very firmly aggregated with each other by electrostatic affinity, To form a closed pore structure, in which the nanoparticles accumulate on the conductive substrate.

At this time, the temperature of the electrospray is preferably 10 ~ 40 ℃, most preferably 20 ~ 30 ℃, the humidity is preferably 1 ~ 70%, most preferably 20-40%.

The distance between the injection nozzle 3 and the conductive substrate 4 is preferably 3 to 15 cm, most preferably 7 to 10 cm. In addition, the applied voltage is preferably 5 to 14 kV, most preferably 7 to 11 kV. In this case, when the applied voltage is less than 5kV, the electrospray is impossible, and when the applied voltage exceeds 14kV, the metal oxide nanoparticles agglomerate and do not form uniform nanoparticles.

FIG. 3 is a photograph of a metal oxide blocking layer of nanoparticles formed on a substrate according to the method of the present invention. As shown in the photo, the blocking layer of the present invention is formed without any pores by uniformly forming metal oxide nanoparticles. It shows the state and has the characteristics of closed pore structure.

As described above, a porous membrane is formed on the metal oxide blocking layer of the nanoparticles formed by electrospray to adsorb dye to the porous membrane to manufacture a semiconductor electrode for dye-sensitized solar cell. For example, an ethanol solution in which ruthenium-based dye molecules (such as N719 dye at a concentration of 3 × 10 ⁴ M) is dissolved is impregnated with a conductive substrate having a porous membrane for at least 12 hours to adsorb the dye, followed by washing and drying with ethanol. The absorbed semiconductor electrode is completed. The dye adsorbed on the porous membrane is preferably ruthenium-based dyes or coumarin-based organic dyes, but is not limited thereto.

The semiconductor electrode manufacturing process described above is a specific part of the dye-sensitized solar cell manufacturing process of the present invention, and the other electrode manufacturing process, the assembly of the two electrodes, and the electrolyte injection process can be carried out by a conventional method.

For example, the counter electrode may be manufactured by coating a platinum layer on a transparent plastic or glass substrate coated with ITO or FTO. In addition, instead of the platinum layer, a coating layer made of carbon particles, carbon nanofibers, carbon nanotubes, graphene monolayers and graphene multilayers (20 layers or less, thickness 5 nm or less), conductive polymers, or mixtures thereof may be used. have.

The counter electrode (anode) and the semiconductor electrode (anode) thus produced are assembled.

When assembling the positive electrodes, the conductive surfaces on the positive and negative electrodes face inward. Next, a liquid electrolyte or a polymer gel electrolyte is filled in the space between the two electrodes. For example, a liquid electrolyte in which hexyl dimethyl imidazolium iodine, guanidine thiocyanate, iodine and quaternary butylpyridine is dissolved in an acetonitrile / valeronitrile mixed solution can be used. The polymer gel electrolyte includes polyvinylidenefluoride-co-polyhexafluoropropylene, polyacrylonitrile, polyethyleneoxide and polyalkylacrylate. It is preferable to use a polymer selected from among, and it is preferable to contain 5 to 20 parts by weight of one or more of these polymers in the liquid electrolyte based on the weight of the liquid electrolyte.

FIG. 2 shows an example of a dye-sensitized solar cell having a nano-sized metal oxide barrier layer manufactured according to the method described so far, and the structure of the dye-sensitized solar cell of the present invention will be described below with reference to FIG. 2. .

The dye-sensitized solar cell according to the present invention has a structure largely including a semiconductor electrode 10, a counter electrode 20, and an electrolyte 30 injected between these two electrodes.

The cathode of the semiconductor electrode 10 is a nano-sized metal oxide blocking layer 12 prepared in accordance with the present invention on the conductive substrate (1l), the porous membrane 13 is a dye adsorbed on the blocking layer 12 ).

In addition, the counter electrode 20, which is an anode, includes a conductive substrate 21 and a platinum layer 22 coated on the substrate 21. Alternatively, a layer made of carbon particles, carbon nanofibers, carbon nanotubes, graphene monolayers, graphene multilayers, conductive polymers, or mixtures thereof may be used instead of the platinum layer 22.

The electrolyte 30 is filled in the empty space between the two electrodes 10. 20 and the pores of the porous membrane 13 of the semiconductor electrode 10. And this electrolyte is sealed with a spacer (not shown) so as not to leak.

As such, in a solar cell having a nano-sized metal oxide barrier layer, a barrier layer is prepared by directly coating a metal oxide without using a metal oxide precursor solution, thereby simplifying the process by eliminating a separate deposition process or heat treatment process. In addition, the blocking layer may be increased to increase the photoelectric efficiency.

4 is a graph showing the photocurrent amount of the solar cell excluding the blocking layer according to the present invention, Figure 5 is a graph showing the photocurrent amount of the solar cell provided with a blocking layer according to the present invention.

4 and 5, it can be seen that the photocurrent of the solar cell of FIG. 5 having the blocking layer of the present invention increases compared to the solar cell of FIG. 4 excluding the blocking layer. That is, the photovoltaic efficiency (EFF) of the solar cell of FIG. 4 is 4.99%, whereas the photovoltaic efficiency (EFF) of the solar cell of FIG.

Therefore, according to the present invention, since the barrier layer is manufactured by directly coating the metal oxide without using the metal oxide precursor solution, it does not require a separate deposition process or heat treatment process, thereby improving workability and reducing costs. do.

In addition, according to the present invention, since the metal oxide precursor solution that is harmful to the human body is not used, it is environmentally friendly.

Furthermore, according to the present invention, it is possible to maximize the photoelectric efficiency by providing a nano-sized metal oxide as a blocking layer.

1 is a schematic view for explaining an electrospray method for forming a blocking layer according to the present invention,
2 is a schematic view of a solar cell including a blocking layer according to the present invention,
Figure 3 is a SEM photograph of the nanoparticle sized metal oxide blocking layer according to the present invention by electron microscope,
4 is a graph showing the photocurrent amount of the solar cell excluding the blocking layer according to the present invention,
5 is a graph showing the photocurrent amount of the solar cell provided with a blocking layer according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely examples of the present invention, and the scope of the present invention is not limited thereto.

<Semiconductor Electrode Manufacturing Example>

Titanium oxide nanopowder (Aeroxide P25, Evonik Co., Ltd.) having a diameter of 21 nm and a specific surface area of 50 m ² / g was uniformly used in a ethanol solution at a concentration of 10% by weight to prepare a barrier layer according to the present invention. Dispersion to prepare a dispersion solution.

The dispersion solution was electrosprayed on the conductive transparent glass substrate to form a blocking layer. The electrospray environment was conducted in a controlled temperature and humidity space (25 ℃, 25%). The distance between the spray nozzle and the glass substrate was 10cm and the applied voltage was 10kV. The injection amount of the dispersion solution was 30 µl / min to constitute a barrier layer.

A porous membrane was formed on the barrier layer by electrospraying. In the porous membrane, a mesoporous titanium oxide nanoball was stacked in a range of 10 to 15 μm, and a heat treatment was performed at about 500 ° C. for about 30 minutes to prepare a semiconductor electrode having a barrier layer and a porous membrane. Here, the applied voltage used for electrospray was 15kV to form a nano-ball to form a porous membrane.

Comparative Example

Excluding the blocking layer of the above embodiment, a mesoporous titanium oxide nanoball, which was used as a porous membrane, was laminated on the conductive transparent glass substrate by 10 to 15 μm, and the semiconductor was provided with only the porous membrane by heat treatment at about 500 ° C. for about 30 minutes. An electrode was prepared.

<Solar Cell Manufacturing Example>

Each semiconductor electrode substrate obtained in Comparative Examples and Examples was impregnated with an ethanol solution containing 3 × 10 ^-4 M of ruthenium-based dye (D719, Everlight) for 12 hours to adsorb the dye, and then After washing five times and dried to prepare a dye-adsorbed semiconductor electrode. Next, a counter electrode was prepared by coating a platinum layer on the transparent conductive substrate coated with FTO. A thermosetting spacer (surlyn, Dupont) having a thickness of about 20 μm is placed between the semiconductor electrode and the counter electrode, and the two electrodes are attached by applying a slight pressure at a temperature of 120 ° C., and then an iodine-based liquid electrolyte is formed in the space between the two electrodes. To fill and seal the dye-sensitized solar cell was prepared. At this time, the iodine-based liquid electrolyte composition used was 0.6M butylmethylimidazolium iodine, 0.05M iodine, 0.1M lithium iodine and 0.5M quaternary butylpyridine dissolved in acetonitrile / valeronitrile (85:15) mixed solvent. It consists of a liquid electrolyte.

The photoelectric efficiency of each solar cell manufactured as described above is illustrated in FIGS. 4 and 5.

4 is a graph showing the photocurrent amount of the solar cell excluding the blocking layer according to the present invention, Figure 5 is a graph showing the photocurrent amount of the solar cell provided with a blocking layer according to the present invention.

4 and 5, it can be seen that the photocurrent of the solar cell of FIG. 5 having the blocking layer and the porous membrane according to the present invention was increased compared to the solar cell of FIG. 4 without the blocking layer and having only the porous membrane. have. That is, the photovoltaic efficiency (EFF) of the solar cell of FIG. 4 is 4.99%, whereas the photovoltaic efficiency (EFF) of the solar cell of FIG.

The present invention is used in the production of electrodes of dye-sensitized solar cells.

10: semiconductor electrode 20: counter electrode
30: electrolyte 11,21: conductive substrate
12: barrier layer 13: porous membrane
22: platinum layer

Claims (11)

Preparing a dispersion solution by uniformly dispersing the metal oxide nanoparticles in a solvent; And
Forming a blocking layer by electrospraying the dispersion solution such that nanoparticles are stacked on the conductive substrate. The method of claim 1, wherein the applied voltage during the electrospray is 5 ~ 14kV. The method of claim 1, wherein the solvent is any one of an alcohol-based organic solvent, distilled water, and a mixed solution thereof. The method of claim 1, wherein the metal oxide nanoparticles are at least one selected from titanium oxide, zinc oxide, tin oxide, nitric oxide, tungsten oxide, strontium oxide, and zirconium oxide. The method of claim 1, wherein the metal oxide nanoparticles have a diameter of 1 to 50 nm. Preparing a dispersion solution by uniformly dispersing the metal oxide nanoparticles in a solvent;
Forming a blocking layer by electrospraying the dispersion solution so that the nanoparticles are stacked on the conductive substrate;
Forming a porous membrane for dye-sensitization on top of the barrier layer; And
The dye-sensitized solar cell manufacturing method comprising the step of adsorbing the dye on the porous membrane. The method of manufacturing a dye-sensitized solar cell according to claim 6, wherein the applied voltage during electrospray is 5 to 14 kV. The method of claim 6, wherein the solvent is any one of an alcohol-based organic solvent, distilled water, and a mixed solution thereof. The method of manufacturing a dye-sensitized solar cell according to claim 6, wherein the metal oxide nanoparticles are at least one selected from titanium oxide, zinc oxide, tin oxide, nitric oxide, tungsten oxide, strontium oxide, and zirconium oxide. . The method of claim 6, wherein the metal oxide nanoparticles have a diameter of 1 to 50 nm. A dye-sensitized solar cell prepared by the method according to any one of claims 6 to 10.

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