JP2004055686A - Solar cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell that is manufactured at a low cost and has a high conversion factor, and to provide a method for manufacturing the solar cell. <P>SOLUTION: The solar cell 110 has a photoelectric conversion layer 108 and a pair of electrodes 101, 107 where one of the electrodes 101, 107 for sandwiching the photoelectric conversion layer is transparent. The photoelectric conversion layer comprises a p-type organic semiconductor layer 105 and n-type organic semiconductor powder 106 dispersed on one surface of the p-type organic semiconductor layer. Therefore, the photoelectric conversion layer for efficiently separating charge can be formed by the combination of an organic semiconductor, having satisfactory manufacturing costs and a powered inorganic semiconductor, thus reducing the manufacturing costs and providing a superior conversion factor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a highly efficient and inexpensive sheet-type solar cell.
[0002]
[Prior art]
As a conventional solar cell, a solar cell that performs photoelectric conversion using crystalline silicon or amorphous silicon is known.
Among them, the crystal type uses a plate-shaped thin slice of crystalline silicon for effective use of incident light and cost reduction.
The amorphous type can be thinner than the crystalline type, so that cost can be reduced. However, it is necessary to form a thin film by a method such as CVD using dangerous self-combustible gas, and the conversion efficiency is also higher than that of the crystalline type. It is reduced by about 10%.
[0003]
On the other hand, there has been an attempt to apply a semiconductor made of an organic substance to a film to form a solar cell. For example, a layer in which an n-type organic semiconductor is dispersed in a binder resin (an electron donating organic pigment) and a p-type organic semiconductor layer 2. Description of the Related Art A solar cell formed by stacking (electron-accepting organic pigments) is known (for example, see Japanese Patent Application Laid-Open No. 7-240530).
[0004]
[Problems to be solved by the invention]
In the case of a crystal-type solar cell, it is inevitable that a portion of the margin when cutting out thinly is wasted, and there is a limit in cost reduction.
In addition, the amorphous type not only has lower conversion efficiency than the crystalline type, but also requires a large-scale vacuum device when forming a thin film having uniform characteristics over a large area, which causes an increase in cost.
Solar cells using inorganic semiconductors, especially silicon, have high performance, but no effective measures have been found to reduce material and manufacturing costs.
[0005]
On the other hand, solar cells using organic semiconductors still have a low conversion efficiency and are not practical.
This is often due to the low charge mobility in the organic semiconductor, and there is a problem that the charge excited by light is deactivated before traveling through the organic semiconductor and being separated.
If charge separation by a pn junction, which is relatively frequently used in inorganic semiconductors, can also be realized in organic semiconductors, it is considered that a solar cell with low manufacturing cost and high conversion efficiency can be provided.
[0006]
Among organic semiconductors, p-type organic semiconductors widely exist, and the charge mobility is at a practical level.
On the other hand, the n-type organic semiconductor is unstable in the air, and when bonded to oxygen, its properties change and the p-type is inverted, and the charge mobility is low.
For this reason, it is difficult to stably form a good pn junction using an organic semiconductor, but if at least a p-type organic semiconductor at a practical level can be used well, a solar cell with excellent manufacturing cost and high conversion efficiency can be obtained. May be possible.
[0007]
The present invention has been made in view of the above circumstances, and provides a solar cell with low manufacturing cost and high conversion efficiency, and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
The present invention includes a photoelectric conversion layer and a pair of electrodes at least one of which sandwiches the photoelectric conversion layer, wherein the photoelectric conversion layer is dispersed on one surface of a p-type organic semiconductor layer and one surface of the p-type organic semiconductor layer. And a solar cell comprising the n-type inorganic semiconductor powder.
[0009]
That is, in the solar cell according to the present invention, the photoelectric conversion layer is composed of the p-type organic semiconductor layer and the n-type inorganic semiconductor powder dispersed on one surface thereof.
For this reason, it is possible to form a photoelectric conversion layer capable of efficiently separating charges from a combination of an organic semiconductor and a powdery inorganic semiconductor with excellent manufacturing cost, and as a result, the manufacturing cost is low and the conversion efficiency is excellent. We can provide solar cells.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The solar cell according to the present invention includes a photoelectric conversion layer, and a pair of electrodes at least one of which sandwiches the photoelectric conversion layer. The photoelectric conversion layer is formed on a p-type organic semiconductor layer and on one surface of the p-type organic semiconductor layer. Characterized by comprising an n-type inorganic semiconductor powder dispersed in
[0011]
In the solar cell according to the present invention, for example, a transparent electrode made of ITO (indium tin oxide), SnO ₂ (tin oxide), ZnO, etc. And a metal electrode made of silver, copper, or the like.
[0012]
In the solar cell according to the present invention, the p-type organic semiconductor layer may be made of any one of pentacene, thiophene, tetracene, polyphenylenevinylene, and phthalocyanine.
Of the above, pentacene is preferred for high charge mobility, and polyphenylenevinylene is preferred for ease of formation by coating.
[0013]
In the solar cell according to the present invention, the n-type inorganic semiconductor powder may be composed of silicon powder or compound semiconductor powder.
Here, examples of the compound semiconductor include gallium arsenide and indium phosphide.
However, in these compound semiconductors, if the band gap is large, holes generated by the irradiated light are not used for charge transfer to the p-type organic semiconductor layer, but are used for oxidizing the p-type organic semiconductor film. I will.
For this reason, a semiconductor having a small band gap is suitable as the n-type inorganic semiconductor powder, and an n-type silicon powder is suitable in consideration of cost and the like.
[0014]
In the solar cell according to the present invention, the n-type inorganic semiconductor powder having an average particle diameter of about several nm to several tens of μm can be used.
However, from the viewpoint of the conversion efficiency of the photoelectric conversion layer, the average particle size is preferably in the range of about 20 nm to 20 μm, more preferably in the range of about 20 to 100 nm, or in the range of about 1 to 20 μm. Is preferred.
[0015]
In the solar cell according to the present invention, the n-type inorganic semiconductor powder may have an organic compound on its surface.
With such a configuration, the n-type inorganic semiconductor powder is more familiar with the interface of the p-type organic semiconductor layer, and the movement of charges is performed more smoothly.
Here, a hydrocarbon can be used as the organic compound, and when modifying the surface of the silicon powder, for example, hexamethyldisilane or a derivative thereof can be used.
[0016]
These chemicals are used in the fields of LSIs and the like as an adhesion enhancer between a photoresist and a silicon substrate or between a silicon oxide film and a silicon substrate. The silicon powder is simply immersed in a chemical solution or exposed to a vapor atmosphere. A methyl group attached to the surface is formed.
[0017]
From another viewpoint, the present invention is a method for manufacturing a solar cell according to the above-described present invention, in which a solution in which a p-type organic semiconductor is dissolved in a solvent is prepared, and the solution is applied to an electrode. Production of a solar cell including a step of forming a p-type organic semiconductor layer, dispersing an n-type inorganic semiconductor powder on the surface of the p-type organic semiconductor layer to form a photoelectric conversion layer, and forming an electrode on the photoelectric conversion layer It also provides a way.
[0018]
In the above manufacturing method according to the present invention, the p-type organic semiconductor and polyphenylenevinylene and chloroform may be used as the solvent, and the solution may be applied by spin coating.
As a specific solution, for example, a solution obtained by dissolving about 1.0 to 2.0% by weight of polyphenylenevinylene in chloroform can be used.
[0019]
【Example】
Hereinafter, a solar cell according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, common members will be described using the same reference numerals.
[0020]
Example 1
FIG. 1 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 1 of the present invention.
As shown in FIG. 1, the solar cell 110 according to the first embodiment includes a photoelectric conversion layer 108, a pair of transparent electrodes 107 sandwiching the photoelectric conversion layer 108, and a metal electrode 101, and the photoelectric conversion layer 108 is a p-type organic compound. The semiconductor layer 105 includes an n-type inorganic semiconductor powder 106 dispersed on one surface of the p-type organic semiconductor layer 105.
[0021]
Specifically, an extraction electrode 102 is provided on one surface of the substrate 100, and the extraction electrode 102 is connected to the metal electrode 101.
The metal electrode 101 is made of a metal having a low work function so as to make ohmic contact with the n-type inorganic semiconductor powder 106.
Although the n-type inorganic semiconductor powder 106 is partially buried in the p-type organic semiconductor layer 105, a part of the n-type inorganic semiconductor powder 106 forms an ohmic contact with the metal electrode 101.
[0022]
The p-type organic semiconductor layer 105 is in contact with a transparent electrode 107 made of an oxide of indium tin, and the transparent electrode 107 is provided on one surface of the transparent substrate 104.
Further, the periphery of the photoelectric conversion layer 108 is sealed with a protective resin 103 for preventing entry of moisture.
[0023]
The solar cell according to the first embodiment can be manufactured, for example, as follows.
A transparent electrode 107 made of indium tin oxide is formed on a transparent substrate 104 made of glass, and a chloroform solution of polyphenylenevinylene is applied on the transparent electrode 107 to form a p-type organic semiconductor layer 105.
Specifically, the solution is uniformly applied on the transparent electrode 107 by spin coating so as to have a thickness of about 0.1 μm, and baked at about 100 ° C. for about 10 minutes under a nitrogen atmosphere.
[0024]
Thereafter, the solution is further applied to a thickness of about 2 to 3 μm, and before drying, the n-type inorganic semiconductor powder 106 made of n-type silicon powder is dispersed on the surface of the coating layer.
That is, the n-type inorganic semiconductor powder 106 is settled in the coating layer (polyphenylene vinylene film) by its weight by dispersing it before drying.
[0025]
In Example 1, as the n-type inorganic semiconductor powder 106, four types of n-type silicon having an average particle diameter of about 1 μm, about 2 μm, about 10 μm, and about 20 μm were used for a comparative experiment described in a later section. Powders were each used.
Thereafter, the metal electrode 101 was formed so as to be able to contact the n-type inorganic semiconductor powder. As a method for forming the metal electrode 101, a method such as an evaporation method, a sputtering method, or application of a metal paste can be used.
The thickness of the metal electrode 101 may be such that the n-type inorganic semiconductor powder 106 exposed from the p-type organic semiconductor layer 105 is hidden.
[0026]
Thereafter, the periphery of the photoelectric conversion layer 108 is sealed with a protective resin 103, and the substrate 100 on which the extraction electrode 102 is formed is placed so that the metal electrode 101 and the extraction electrode are in contact with each other. Complete 110.
In addition, since the protective resin 103 affects the reliability of the solar cell, it is preferable to use an epoxy resin, an acrylic resin, or the like that is excellent in preventing moisture penetration.
[0027]
Although a glass substrate is used as the transparent substrate 104, a substrate made of a transparent resin such as polyethylene terephthalate, polyethylene, or acrylic may be used.
The same applies to the substrate 100, which may be made of either resin or glass.
When the substrate 100 and the transparent substrate 104 are made of resin, a flexible solar cell can be obtained.
[0028]
When the conversion efficiency was determined by irradiating the four types of solar cells 110 thus manufactured with solar simulated light, the particle size of the n-type inorganic semiconductor powder 106 was reduced as shown in line (a) of FIG. The conversion efficiency tended to increase as the size became smaller, and the conversion efficiency was about 8% when the average particle size was about 1 μm.
[0029]
As described above, the photoelectric conversion layer 108 formed by dispersing the n-type inorganic semiconductor powder 106 on the surface of the p-type organic semiconductor layer 105 can smoothly separate charges generated by light and improve the conversion efficiency of the solar cell. Was found to be effective.
Further, since the photoelectric conversion layer 108 can be formed using an organic semiconductor and an inorganic semiconductor powder without using a single crystal silicon plate or a polysilicon plate which is disadvantageous in terms of manufacturing cost, it is effective in reducing manufacturing cost. Was obtained.
[0030]
Example 2
FIG. 2 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 2 of the present invention.
The solar cell according to the second embodiment is different from the solar cell 110 according to the first embodiment (see FIG. 1) in that the n-type inorganic semiconductor powder 106 is changed to the n-type inorganic semiconductor powder 206 shown in FIG. Has not changed.
[0031]
As shown in FIG. 2, the n-type inorganic semiconductor powder 206 of the solar cell 210 according to the second embodiment is obtained by performing a treatment on the surface of the n-type silicon powder to modify the hydrocarbon 206a.
Since the surface of the n-type silicon powder 206 is modified with the hydrocarbons 206a, the interface with the p-type organic semiconductor layer 205 is improved, and the charge transfer is performed more smoothly.
In addition, in Example 2, similarly to Example 1 described above, four types of solar cells were manufactured using four types of n-type silicon powders each having an average particle size of about 1 μm, about 2 μm, about 10 μm, and about 20 μm. did.
[0032]
When these four types of solar cells were irradiated with solar simulation light and compared, as shown in line (b) of FIG. 4, the tendency that the conversion efficiency increased as the average particle size became smaller was the same as in Example 1. Was seen in
Further, due to the effect of modifying the surface of the n-type inorganic semiconductor powder 206 with the hydrocarbon 206a, the conversion efficiency is improved by about 2% as compared with Example 1 for any particle diameter, and about 1% for the average particle diameter of about 1 μm. It showed a conversion efficiency of 10%.
[0033]
Example 3
FIG. 3 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 3 of the present invention.
The solar cell according to Example 3 is obtained by changing the n-type inorganic semiconductor powder 106 of the solar cell 110 (see FIG. 1) according to Example 1 to the n-type inorganic semiconductor powder 306 shown in FIG. Has not changed.
[0034]
As shown in FIG. 3, the n-type inorganic semiconductor powder 306 of the solar cell 310 according to the third embodiment is obtained by pulverizing the n-type silicon powder to about 20 to 100 nm and forming a hydrocarbon on the surface in the same manner as in the second embodiment. 306a.
For this reason, conformity to the interface of the p-type organic semiconductor layer 305 is improved, and charge transfer is performed smoothly.
[0035]
As a method of pulverizing n-type silicon, for example, the following method is available.
A first method is a method in which a liquid silicon compound is sprayed using ultrasonic waves or the like to precipitate silicon particles. In this method, the size of the particles can be made uniform by adjusting the spraying conditions.
[0036]
As another method, there is a method in which a silicon powder is suspended in an alcohol such as ethyl alcohol or methyl alcohol and irradiated with light of a specific wavelength.
According to this method, carriers are generated in a portion irradiated with light of a specific wavelength, and the generated carriers oxidize the surface of silicon to cause cracks, whereby the powder is finely powdered.
If such a photoreaction is continued for a long time, any particles will break down and become smaller, but the smaller particles will have a larger band gap due to the particle effect and will not respond to the light of the original wavelength, forming fine particles of a certain size. It is possible to do.
[0037]
When this method is used, alcohol is used as a solvent as described above. This is because when water is used, the surface oxidation of silicon particles caused by light irradiation becomes excessive, and the photoactivity of the finely divided silicon powder is impaired.
In Example 3, five types of solar cells were manufactured using five types of n-type silicon powders each having an average particle size of about 20 nm, about 40 nm, about 60 nm, about 100 nm, and about 120 nm.
[0038]
When these five types of solar cells 310 were irradiated with solar simulated light and compared, as shown in line (c) of FIG. 4, those having an average particle size of about 100 nm had the highest conversion efficiency of about 12%. It was confirmed that pulverization of the n-type silicon powder contributed to further improvement of the conversion efficiency.
[0039]
However, unlike Example 1 and Example 2 described above, the conversion efficiency does not tend to increase as the average particle size decreases, and the conversion efficiency is maximized when the average particle size is about 100 nm. A phenomenon was seen in which the conversion efficiency gradually decreased as the distance deviated.
This is because if the n-type silicon powder is excessively finely divided, a problem occurs in terms of effective use of light, or the thickness of the oxide formed on the surface of the silicon powder is not negligible with respect to the particle size. It is thought to be due to the thickness.
[0040]
【The invention's effect】
According to the present invention, since the photoelectric conversion layer is composed of the p-type organic semiconductor layer and the n-type inorganic semiconductor powder dispersed on one surface of the p-type organic semiconductor layer, the organic semiconductor and the powdery inorganic semiconductor which are excellent in production cost are provided. A photoelectric conversion layer capable of efficiently separating charges can be formed from the combination of the above, and as a result, a solar cell with low manufacturing cost and excellent conversion efficiency can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 1 of the present invention.
FIG. 2 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 2 of the present invention.
FIG. 3 is an explanatory view schematically showing a configuration of a solar cell according to Embodiment 3 of the present invention.
FIG. 4 is a graph showing the correlation between the particle size of n-type inorganic semiconductor powder and the conversion efficiency in solar cells according to Examples 1 to 3 of the present invention.
[Explanation of symbols]
100 ... substrate 101 ... metal electrode 102 ... extraction electrode 103 ... protective resin 104 ... transparent substrate 105 ... p-type organic semiconductor layer 106 ... n-type inorganic semiconductor powder 107 ... -Transparent electrode 108-Photoelectric conversion layer 110-Solar cell

Claims (8)

A photoelectric conversion layer, and a pair of electrodes, at least one of which sandwiches the photoelectric conversion layer, is transparent. Solar cells made of semiconductor powder. The solar cell according to claim 1, wherein the p-type organic semiconductor layer is made of any one of pentacene, thiophene, tetracene, polyphenylenevinylene, and phthalocyanine. The solar cell according to claim 1, wherein the n-type inorganic semiconductor powder comprises a silicon powder or a compound semiconductor powder. The solar cell according to claim 1, wherein the n-type inorganic semiconductor powder has an organic compound on a surface thereof. The solar cell according to claim 1, wherein the n-type inorganic semiconductor powder has an average particle size in a range of 1 to 20 μm. The solar cell according to any one of claims 1 to 4, wherein the n-type inorganic semiconductor powder has an average particle size in a range of 20 to 100 nm. The method for producing a solar cell according to any one of claims 1 to 6, wherein a solution is prepared by dissolving a p-type organic semiconductor in a solvent, and the solution is applied on an electrode to form the p-type organic semiconductor. A method for manufacturing a solar cell, comprising: forming a layer; dispersing an n-type inorganic semiconductor powder on a surface of a p-type organic semiconductor layer to form a photoelectric conversion layer; and forming an electrode on the photoelectric conversion layer. The method for manufacturing a solar cell according to claim 7, wherein the p-type organic semiconductor and polyphenylenevinylene and chloroform are used as the solvent, and the solution is applied by spin coating.

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