KR20060124055A - Dye-sensitized solar cell having a long service life time - Google Patents

Abstract

A dye-sensitized solar cell having a long lifetime is provided to prevent the lifetime of a dye-sensitized solar cell from being decreased by UV rays by including an oxide layer in the surface layer of the solar cell such that the oxide layer is capable of blocking UV rays having a wavelength not higher than 400 nanometers. A transparent substrate(1) is positioned under an oxide layer(7) having a thickness of 0.05~1.0 micrometer wherein the opposite side of the transparent substrate to the oxide layer is coated with ITO or FTO. A TiO2 layer(2) is positioned under the transparent substrate. A dye layer(3) is positioned under the TiO2 layer wherein a part of the dye layer is deposited on the TiO2 layer. An electrolyte layer(4) is positioned under the dye layer. An electrode(5) is positioned under the electrolyte layer. A substrate is disposed under the electrode.

Description

Long life dye-sensitized solar cell {DYE-SENSITIZED SOLAR CELL HAVING A LONG SERVICE LIFE TIME}

1 is a schematic view showing the structure of a conventional solar cell, and

2 is a schematic view showing the structure of a solar cell having an oxide layer for blocking ultraviolet rays according to the present invention.

The present invention relates to a long-life dye-sensitized solar cell, and more particularly, to a long-life dye-sensitized solar cell that improves durability by forming a blocking film on the surface of the solar cell to block ultraviolet rays of some wavelengths of sunlight.

A solar cell refers to a battery in which an internal semiconductor absorbs light and flows current using a photovoltaic effect in which electrons and holes are generated. Conventionally, as the semiconductor of the solar cell as described above, a semiconductor in the form of a diode by n-p junction of an inorganic material such as silicon or gallium arsenide (GaAs) has been mainly used. The inorganic semiconductor has high energy conversion efficiency but high manufacturing cost, and thus, the utilization of the inorganic semiconductor was not sufficient.

In order to overcome the problems of the inorganic semiconductor as described above, a technique for replacing the inorganic semiconductor with an organic dye has been proposed. In general, dyes have a color mainly by absorbing light in the visible light band, and the solar cell using the same has a so-called redox reaction in which the organic dye is separated into electrons and holes and then recombined when the organic dye absorbs light. To generate a current. This type of solar cell is called a dye-sensitized solar cell.

1 shows the dye-sensitized solar cell. In the conventional solar cell, as shown in FIG. 1, the transparent substrate 1, the titanium dioxide layer 2, the dye layer 3, the electrolyte layer 4, It is formed of the electrode layer 5 and the substrate 6. The transparent substrate is a substrate made of a transparent material such as glass coated with a transparent electrode such as ITO (In-doped SnO2) or FTO (F-doped SnO2) on the entire surface, so that light is transmitted well, Titanium dioxide formed in the porous layer is formed so that light transmittance is increased and the dye is easily colored. The titanium dioxide layer also serves as an electrode that serves as a conductive path for electrons generated by the electron and hole separation reaction of the dye. In addition, the dye layer is deposited from one side of titanium dioxide, that is, from the side of titanium dioxide located on the opposite side of the transparent substrate, resulting in a layer substantially the same as titanium dioxide.

An electrolyte layer is positioned below the dye layer, and exists in a liquid state for easy characteristics in manufacturing a solar cell. The electrolyte layer provides a place where holes generated by the electron and hole separation reaction generated in the dye layer react with the electrons returned through the circuit to disappear.

However, as described above, the electron and hole separation reactions do not occur in light having a short wavelength (particularly, a wavelength of 400 nm or less) in the ultraviolet band due to the characteristics of the organic dyes mainly reacting in the visible light band. In addition, when the ultraviolet light is absorbed into the solar cell, it has a fatal adverse effect on the solar cell. That is, when the ultraviolet light is absorbed into the solar cell, there is a possibility that the liquid electrolyte contacting the titanium dioxide with the dye and the very thin dye layer interposed therebetween by the photocatalytic reaction of titanium dioxide. In addition, due to the nature of the solar cell using a liquid electrolyte is sealed (not shown) around the electrolyte, when the electrolyte is exposed to ultraviolet light due to the high energy of the ultraviolet light to generate a gas from the electrolyte and the dye to the gas The sealing of the solar cell may be broken by this.

As a result, the life of the solar cell is reduced and the above lifespan acts as a cause of lowering the utilization of the solar cell.

Accordingly, it is an object of the present invention to provide a dye-sensitized solar cell capable of preventing a decrease in life due to ultraviolet rays.

The solar cell of the present invention for achieving the above object, the oxide layer; A transparent substrate disposed under the oxide layer and coated with ITO or FTO on an opposite side of the oxide layer; A titanium dioxide (TiO 2) layer positioned below the transparent substrate; A dye layer disposed under the titanium dioxide layer and partially deposited on the titanium dioxide layer; An electrolyte layer positioned below the dye layer; An electrode located under the electrolyte layer; And a substrate positioned below the electrode.

At this time, the oxide layer preferably has a band gap in the range of 3.0 ~ 3.2eV.

In addition, the oxide layer is preferably one or two or more selected from the group consisting of TiO ₂ , CeO ₂ , ZnO, SrTiO ₃ , and the like.

In addition, the oxide layer preferably has a thickness of 0.05 μm to 1.0 μm.

Hereinafter, the present invention will be described in detail with reference to FIG. 2.

The inventors of the present invention have studied in depth the configuration of a solar cell to block harmful ultraviolet rays as much as possible, so that there is no problem in the power production due to visible light, as a result, only the ultraviolet light is selected on the light transmission side of the solar cell It was found that visible light could easily penetrate without blocking UV rays into the cell.

As a result, the solar cell of the present invention, as shown in FIG. 2, has an oxide layer 7 on the surface thereof and a transparent substrate 1 coated with ITO or FTO on the opposite side of the oxide layer when viewed from the top. And a titanium dioxide layer (2) located below the transparent substrate (1), a dye layer (3) deposited in the titanium dioxide, an electrolyte layer (4) located below the dye layer, and an electrode layer (5) located below the electrolyte layer (5). ) And the substrate 6 positioned below the electrode layer.

Here, the oxide layer 7 is a constituent element of the present invention. The oxide layer 7 needs to be able to block ultraviolet light having a wavelength of 400 nm or less and to transmit light in the visible light region required for power generation. In order to block the ultraviolet light as described above, it is preferable to use an oxide having a band gap in a predetermined range. Since the ultraviolet light targeted by the present invention is light in the ultraviolet band of 400 nm or more, the band gap of the oxide layer is preferably in the range of 3.0 to 3.2 eV.

In addition, according to the results of the inventors of the present invention, the oxide layer is preferably made of an oxide such as TiO ₂ , CeO ₂ , ZnO or SrTiO ₃ . Since the oxide layer has a band gap in the range of 3.0 to 3.2 eV, which is the object of the present invention, when it comes into contact with light having a wavelength of 400 nm or less, electrons are excited from the valence band to the conduction band to absorb the light. do. Therefore, light having a wavelength of 400 nm or less does not pass through the oxide layer and is absorbed in the oxide layer. However, since visible light is not large enough to excite electrons from the valence band to the conduction band (the wavelength is not small), the visible light is not absorbed by the oxide layer and propagates into the solar cell, thereby separating electrons and holes from the dye. To generate power.

At this time, the oxide layer preferably has a thickness of 0.05 ~ 1㎛ range. If the thickness of the oxide layer is less than 0.05 μm, ultraviolet rays may not be completely absorbed by the oxide layer, and a part of the oxide layer may penetrate into the solar cell. If the thickness of the oxide layer exceeds 1 μm, visible light may be lost. This is because it may be reflected or scattered without passing through the oxide layer. Therefore, it is preferable that the thickness of an oxide layer is between 0.05-1 micrometer.

The transparent substrate 1 formed under the oxide layer 7 may be used if only the transparency is secured because the transparent substrate 1 is used to physically support the solar cell without disturbing the transmission of light when the solar cell itself is used as a transparent glass window. If not used as a transparent glass window, an opaque substrate may be used. However, the glass substrate is preferable in consideration of securing the material and ease of handling.

The titanium dioxide layer 2 formed below the glass substrate and onto which the dye is deposited is preferably porous. This is to allow the dye to be easily deposited between the porous pores and to allow the light to easily reach the dye. At this time, the titanium dioxide layer preferably has a porosity of 5 to 40%. The reason is that when the porosity is less than 5%, the rate of visible light reaching the dye is too low, and when the porosity is more than 40%, the amount of titanium dioxide is too large so that the dye is uniformly colored on titanium dioxide. Because it is difficult to be.

The dye may be used as long as electron and hole separation occur in the visible light band, and all dyes used in conventional dye-sensitized solar cells may be used. Examples of such dyes include polypyridyle ruthenium complexes.

In addition, the electrolyte layer 4 is preferably a liquid electrolyte, and specifically, I ⁻ / I ^3- electrolyte type. If a solid electrolyte having a high electrical conductivity performs the same function as the liquid electrolyte described above, it may be applied.

The electrode 5 positioned below the electrolyte layer may be a metallic or oxide material through which current can easily flow, and there is no particular limitation on the material. In addition, the lower substrate 6 may also be used as long as it is transparent or opaque, as long as it can structurally support the solar cell.

(Example)

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that the following examples are provided to aid the understanding of the present invention, and not to limit the scope of the present invention to the following examples. This is because the scope of the present invention extends only to the matters described in the claims and all matters legally expanded therefrom.

1. Light transmittance test

After forming a titanium dioxide layer as an oxide layer for blocking UV rays on the transparent glass substrate, and then irradiated with sunlight, the absorption of visible light and ultraviolet light of wavelength 400nm or less was measured from the absorption spectrum. The titanium dioxide layer was formed on the surface of the glass substrate by spin coating. In order to observe the effect of the thickness of the titanium dioxide layer, the thickness of the titanium dioxide layer was changed to 0, 0.2, 0.8, 1.5 μm by repeated coating. As a result of measuring the light absorbency by the above experiment, when the thickness of the layer was 0 μm, both the visible light and the ultraviolet light showed less than 5%. When the thickness of the layer is 0.2 μm, the absorbance of visible light is hardly absorbed by 0.1%, while the absorbance of ultraviolet light is 8% (400 nm) and 98% (300 nm), and most of the ultraviolet light is absorbed by the oxide layer. It could be confirmed.

Similarly, even when the layer thickness was 0.8 μm, the absorbance of visible light was 0.3% and the ultraviolet light absorption was 28-99%, respectively, which was higher than that of 0.2 μm. Indicated. However, when the thickness of the layer is 1.5 µm, the absorbance of visible light is remarkably reduced, which makes it difficult to perform the role of a solar cell (0.3% visible light, 46-100% ultraviolet light). It was found that the thickness of the oxide layer was between 0.05 and 1.0 µm.

2. Solar Cell Life Test

According to the present invention, a life test of a solar cell having a titanium dioxide layer of 0.5 µm on a glass substrate surface and a conventional solar cell having no oxide layer at all was carried out. Life was based on the reduction in energy conversion efficiency to less than 50% of the initial stage. As a result of the test, the solar cell according to the present invention has a 50% longer life span than the conventional solar cell.

As described above, the dye-sensitized solar cell of the present invention in which an oxide layer capable of blocking ultraviolet rays having a wavelength of 400 nm or less on the surface layer is prevented from reducing the lifespan due to ultraviolet rays, thereby providing a much longer life than conventional dye-sensitized solar cells. Can have

Claims (4)

Oxide layer; A transparent substrate disposed under the oxide layer and coated with ITO or FTO on an opposite side of the oxide layer; A titanium dioxide (TiO 2) layer positioned below the transparent substrate; A dye layer disposed under the titanium dioxide layer and partially deposited on the titanium dioxide layer; An electrolyte layer positioned below the dye layer; An electrode located under the electrolyte layer; And A substrate under the electrode; Long life dye-sensitized solar cell, characterized in that consisting of. The long life dye-sensitized solar cell of claim 1, wherein the oxide layer has a band gap in a range of 3.0 to 3.2 eV. The long life dye-sensitized solar cell of claim 2, wherein the oxide layer is one or two or more selected from the group consisting of TiO ₂ , CeO ₂ , ZnO, SrTiO ₃ , and the like. The long life dye-sensitized solar cell according to any one of claims 1 to 3, wherein the oxide layer has a thickness of 0.05 to 1.0 mu m.

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