JP2004327850A - Integrated solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell which can be easily manufactured with a high versatility, and to provide a method for manufacturing the cell. <P>SOLUTION: The solar cell comprises a substrate 11 including an insulating layer 11b and a plurality of unit cells 15 formed on the upper side of the insulating layer 11b to be connected in series. The unit cell 15 includes a semiconductor layer which contains a Group Ib element, a Group IIIb element, and a Group VIb element and which functions as a light absorbing layer. The substrate 11 has a base 11a containing FGe, Cr and Al, and an insulating layer 11b positioned on the base 11a. The insulating layer is formed by heating and oxiding the base 11a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an integrated solar cell and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, CuInSe ₂ (CIS), which is a compound semiconductor thin film (chalcopyrite structure semiconductor thin film) composed of a group Ib element, a group IIIb element, and a group VIb element, or Cu (In, Ga) Se in which Ga is dissolved in the compound semiconductor thin film ₂ (CIGS) or a structure and a manufacturing method of a CIS-based thin film solar cell module using CuInS ₂ for the light absorbing layer have been reported (for example, see Non-Patent Document 1). In such a CIS-based thin film solar cell, an integrated structure in which a plurality of unit cells are connected in series on a substrate is generally used.
[0003]
An example of a conventional method for manufacturing a CIS-based integrated solar cell will be described with reference to FIG. First, as shown in FIG. 5A, a first electrode film 2 is formed on an insulating substrate 1 made of glass or the like by a sputtering method, and then the first electrode film 2 is irradiated with a continuous wave laser beam L1, thereby forming a first electrode film. The electrode film 2 is removed in a stripe shape to form a strip-shaped first electrode film 2. Thereafter, as shown in FIG. 5B, a semiconductor film 3 composed of a laminated film of a p-type Cu (In, Ga) Se ₂ thin film and an n-type CdS thin film is formed. Thereafter, as shown in FIG. 5C, the semiconductor film 3 is divided into strips by a mechanical scribe method. After that, as shown in FIG. 5D, a transparent conductive film is formed as the second electrode film 4. Finally, as shown in FIG. 5E, the second electrode film 4 is divided into strips by a mechanical scribe method. In the integrated solar cell of FIG. 5E, the second electrode film 4 of each unit cell 5 is connected to the first electrode film 2 of the adjacent unit cell 5 so that each unit cell 5 is connected in series. are doing. Note that in the steps of FIG. 5C and FIG. 5E, it is also possible to divide using a laser beam instead of the mechanical scribe method.
In such an integrated thin-film solar cell, versatility is enhanced by using a flexible substrate such as a stainless steel substrate. Further, when a flexible substrate is used, the substrate wound around a roll can be pulled out and a solar cell can be continuously formed thereon, which is advantageous in manufacturing.
[0004]
[Non-patent document 1]
The 13th European Photovoltaic Solar Conference (13TH EUROPEAN PHOTOVOLTAIC SOLAR CONFERENCE) 1995 p. 1451-1455
[0005]
[Problems to be solved by the invention]
However, when a non-insulating substrate such as a metal flexible substrate (for example, a stainless steel substrate) is used, it is necessary to impart insulation to the surface of the substrate in order to constitute an integrated solar cell. If the substrate surface is not insulative, the unit cells are short-circuited, so that it is impossible to form an integrated solar cell.
[0006]
In addition, even when an insulating film is formed over a metal substrate, the insulating film may not be able to withstand high temperatures when the semiconductor film is formed, and may be separated from the substrate by thermal stress.
[0007]
An object of the present invention is to provide a solar cell that is highly versatile and easy to manufacture, and a method for manufacturing the same, in order to solve the above-mentioned problems of the related art.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a solar cell of the present invention is an integrated solar cell including a substrate including an insulating layer, and a plurality of unit cells formed above the insulating layer and connected in series, The unit cell includes a semiconductor layer made of a semiconductor containing a group Ib element, a group IIIb element, and a group VIb element, and functions as a light absorption layer. The substrate has a base containing Fe, Cr, and Al, and a base on the base. And the insulating layer disposed, wherein the insulating layer is an insulating layer formed by thermally oxidizing the base.
[0009]
The solar cell may further include an insulating film disposed between the insulating layer and the unit cell.
[0010]
In the above solar cell, the Al content in the substrate may be 2 atomic% or more.
[0011]
In the solar cell, the base may include a rare earth element.
[0012]
In addition, the method for manufacturing a solar cell according to the present invention is directed to an integrated solar cell including a plurality of unit cells including a semiconductor layer including a semiconductor including a group Ib element, a group IIIb element, and a group VIb element and functioning as a light absorption layer. (I) forming an insulating layer on at least one principal surface of the base by thermally oxidizing a base containing Fe, Cr, and Al; and (ii) forming an insulating layer on the insulating layer. And forming a plurality of the unit cells connected in series.
[0013]
In the above manufacturing method, the thermal oxidation may be performed at a temperature of 800 ° C. or more in the step (i).
[0014]
In the above manufacturing method, the Al content in the substrate may be 2 atomic% or more.
[0015]
In the above manufacturing method, the base may include a rare earth element.
[0016]
The manufacturing method may further include a step of forming an insulating film on the insulating layer after the step (i) and before the step (ii).
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an integrated thin-film solar cell of the present invention and a method of manufacturing the same will be described with reference to the drawings. In the following description, the same portions are denoted by the same reference numerals, and redundant description will be omitted.
[0018]
The integrated solar cell of the present invention and a method of manufacturing the same will be described with reference to FIG. First, as shown in FIG. 1A, a base 11a containing iron as a main component is prepared. The base 11a is an iron plate containing iron (Fe) as a main component (50 at% or more, usually 70 at% or more) and further containing a small amount of an additional element. The additional element contains at least chromium (Cr) and aluminum (Al), and may further contain a rare earth element such as yttrium (Y). The Cr content is, for example, not less than 10 atomic% and not more than 35 atomic%. The Al content is, for example, not less than 2 atomic% and not more than 10 atomic%. As the base 11a, for example, an iron substrate containing 20 atomic% of Cr and 5 atomic% of Al can be used. Further, when the base 11a contains Cr, the corrosion resistance and durability of the base are improved. Further, the base 11a may contain an alkali metal such as sodium or potassium. When the base 11a contains an alkali metal, the growth of the CIS film and the CIGS film in the semiconductor film 13 can be promoted. The substrate 11a preferably has flexibility, and its thickness is preferably in the range of 30 μm to 200 μm.
[0019]
Next, as shown in FIG. 1B, an insulating layer 11b is formed on at least one main surface of the base 11a by thermally oxidizing the base 11a (step (i)). The substrate 11 after the thermal oxidation includes a portion of the base 11a and a portion where the substrate 11a is oxidized to become the insulating layer 11b. The thermal oxidation is performed in an atmosphere containing oxygen, and is preferably performed at a temperature of 800 ° C. or higher. The thickness of the insulating layer 11b is, for example, 0.1 μm to 3 μm, and preferably 0.4 μm or more.
[0020]
FIG. 2 schematically shows an example of an electric furnace used in the thermal oxidation step. The electric furnace 30 of FIG. The inside of the electric furnace 30 can be set to a desired atmosphere (for example, an oxygen-rich atmosphere). The substrate 11a wound on the roll is sent out from the roll 32, and moves slowly while being heated by the heater 31. The base 11a is heated by the heater 31 at a temperature of 800 to 1100 ° C. for about one hour, thereby forming an oxide film (insulating layer). For example, in the case of forming an aluminum oxide film (an aluminum oxide film such as Al ₂ O ₃ ), heating at about 1000 ° C. for about 1 hour forms an oxide film having a thickness of about 1 μm. The oxide film forms a substrate having an insulating surface. Note that this oxide film may include iron oxide and chromium oxide in some cases. The substrate 11 on which the oxide film is formed is taken up by a roll 33.
[0021]
Next, as shown in FIG. 1C, a plurality of unit cells 15 connected in series are formed above the insulating layer 11b (step (ii)). Thus, the integrated solar cell 10 of the present invention can be manufactured.
[0022]
An example of a method for forming the unit cell 15 will be described with reference to FIG. First, as shown in FIG. 3A, a stripe-shaped resist pattern 21 is formed on the insulating layer 11b of the substrate 11. The resist pattern 21 can be formed by arranging a resist solution in a stripe shape and then fixing (curing) the resist solution. The width of the resist pattern 21 is in the range of 50 μm to 200 μm, and the interval (pitch) is in the range of 3 mm to 8 mm and substantially equal.
[0023]
Next, as shown in FIG. 3B, the first electrode film 12 is formed so as to cover the resist pattern 21. At this time, the first electrode film 12 formed on the resist pattern 21 is formed so as to float by the thickness of the resist pattern 21.
[0024]
Next, as shown in FIG. 3C, the resist pattern 21 and the first electrode film 12 formed on the resist pattern 21 are removed. The first electrode film 12 formed on the resist pattern 21 is simultaneously removed by removing the resist pattern 21. Thus, the first electrode film 12 can be divided into strips.
[0025]
When the resist liquid contains a water-soluble compound (such as a water-soluble resin) or when the resist liquid is a water-soluble ink, the resist pattern 21 can be removed by using a liquid containing water (for example, water). When the resist solution contains a polymer compound soluble in an organic solvent, the resist pattern 21 can be removed by using an organic solvent.
[0026]
As one of the methods of removing the resist pattern 21, there is a method of performing ultrasonic cleaning in a liquid. However, when the viscosity of the resist solution is high, a cleaning method using mechanical means such as cleaning using a brush may be used.
[0027]
Next, as shown in FIG. 3D, a semiconductor film 13 including a pn junction is formed on the first electrode film 12. Then, as shown in FIG. 3E, the semiconductor film 13 is divided into strips by removing a part of the semiconductor film 13 in a stripe shape to form a groove 13a. The groove 13a is formed at a position where a part of the first electrode film 12 is exposed by the groove 13a, and is formed, for example, so as to be adjacent to the groove 12a. Part of the semiconductor film 13 can be removed by a mechanical scribe method or a laser scribe method.
[0028]
The semiconductor film 13 includes a p-type semiconductor layer (light absorbing layer) and an n-type semiconductor layer. As the p-type semiconductor, for example, a chalcopyrite structure semiconductor can be used, and specifically, a semiconductor containing a group Ib element, a group IIIb element, and a group VIb element can be used. More specifically, CuInSe ₂ (CIS), Cu (In, Ga) Se ₂ (CIGS) in which Ga is dissolved in Ga, or a semiconductor in which part of these Se is replaced by sulfur (S) is used. be able to. These can be formed by a vapor deposition method or a sputtering method. Further, as the n-type semiconductor, for example, a compound containing at least a group II element and a group VIb element such as CdS, ZnO, Zn (O, OH), Zn (O, OH, S), and ZnMgO may be used. it can. These can be formed by a chemical bath deposition method or a sputtering method.
[0029]
Next, as shown in FIG. 3F, a second electrode film 14 is formed on the semiconductor film 13 and on the exposed first electrode film 12 from which the semiconductor film 13 has been removed. The second electrode film 14 is also formed in the groove 13a, and the first electrode film 12 and the second electrode film 14 are electrically connected through the groove 13a. Finally, as shown in FIG. 3G, the second electrode film 14 is divided into strips by removing a part of the second electrode film 14 in a stripe shape to form a groove 14a. In this step, a part of the semiconductor film 13 may be removed together with the second electrode film 14, as shown in FIG. As the second electrode film 14, a transparent conductive film such as a ZnO film, a ZnO: Al film, and an ITO film can be used, and can be formed by a sputtering method, a CVD method, or the like.
[0030]
In this way, an integrated solar cell 10 in which a plurality of unit cells (solar cell unit cells) 15 connected in series are formed on the substrate 11 can be manufactured. The second electrode film 14 of each unit cell 15 is connected to the first electrode film 12 of the adjacent unit cell 15, whereby the adjacent unit cells are connected in series. In the solar cell of the present invention, since the insulating layer is formed by oxidizing the element (Al) contained in the substrate, the adhesion between the substrate and the insulating layer is good, and the insulating layer does not peel off from the substrate.
[0031]
Note that the solar cell of the present invention may further include an insulating film disposed between the insulating layer 11b and the first electrode film 12. Such a solar cell 10a is shown in FIG.
The method for manufacturing the solar cell 10a is the same as the method for manufacturing the solar cell 10 except that the insulating film 41 is formed.
[0032]
The insulating film 41 is formed after forming the insulating layer 11b. Although the insulating layer 11b is formed by thermal oxidation, when the substrate cannot be heated uniformly, the insulating layer formed by surface oxidation, for example, an oxide layer of aluminum (an aluminum oxide film such as Al ₂ O ₃ ) has irregularities. It is formed in an accompanying form. If the unevenness of the substrate is large, pinholes are likely to be generated when the semiconductor film is formed. In such a case, it is preferable to form the insulating film 41 in order to fill the unevenness of the substrate and flatten the surface. As a method for forming the insulating film 41, there are a sol-gel method and a plating method. Here, an example of a method of forming an oxide film, for example, an aluminum oxide film (Al ₂ O ₃ film) by a sol-gel method will be described.
[0033]
First, for example, aluminum butoxide (Al (OC ₄ H ₉ ) ₃ ) is prepared as a metal alkoxide, and an alcohol is added thereto to prepare a mixed solution. To this mixed solution, water necessary for hydrolysis and an alcohol solution of an acid as a catalyst are added to prepare a starting solution. This starting solution is heated to a temperature of room temperature to 80 ° C., and while the substrate is immersed in this solution, stirring is performed to cause hydrolysis and polycondensation of the alkoxide. In the starting solution, metal oxide particles are formed and the solution becomes a sol, and as the reaction proceeds further, the whole becomes a solidified gel. Thereafter, the substrate is pulled up and the substrate is dried. Thereafter, an aluminum oxide film (Al ₂ O ₃ film) is formed by sintering the gel on the substrate at a temperature of 200 ° C. or higher.
[0034]
When the insulating film 41 and the insulating layer 11b are formed of the same material, a flat substrate having high connectivity between the two can be obtained. For example, when the insulating layer 11b is made of an aluminum oxide film (Al ₂ O ₃ film), the aluminum oxide film (Al ₂ O ₃ film) is formed by a sol-gel method, thereby bonding with the insulating layer 11b. The insulating film 41 having high property can be formed.
[0035]
As described above, the embodiments of the present invention have been described by way of examples. However, the present invention is not limited to the above embodiments, and can be applied to other embodiments based on the technical idea of the present invention.
[0036]
【The invention's effect】
As described above, according to the present invention, a solar cell having high versatility and easy to manufacture can be obtained.
[Brief description of the drawings]
FIG. 1 is a process sectional view showing one example of a method for manufacturing an integrated solar cell of the present invention.
FIG. 2 is a diagram schematically illustrating an example of a manufacturing apparatus used in the manufacturing method of the present invention.
FIG. 3 is a cross-sectional view showing some steps of an example of the method for manufacturing an integrated solar cell of the present invention.
FIG. 4 is a sectional view showing an example of the integrated solar cell of the present invention.
FIG. 5 is a process cross-sectional view showing one example of a conventional integrated solar cell manufacturing method.
[Explanation of symbols]
10, 10a Solar cell 11 Substrate 11a Base 11b Insulating layer 12 First electrode film 12a, 13a, 14a Groove 13 Semiconductor film 14 Second electrode film 15 Unit cell 21 Resist pattern 30 Electric furnace 31 Heater 32, 33 Roll 41 Insulation film

Claims (9)

An integrated solar cell including a substrate including an insulating layer, and a plurality of unit cells formed above the insulating layer and connected in series,
The unit cell includes a semiconductor layer including a semiconductor including a group Ib element, a group IIIb element, and a group VIb element, and serving as a light absorption layer;
The substrate includes a base including Fe, Cr, and Al, and the insulating layer disposed on the base,
The integrated solar cell, wherein the insulating layer is an insulating layer formed by thermally oxidizing the base. The integrated solar cell according to claim 1, further comprising: an insulating film disposed between the insulating layer and the unit cell. The integrated solar cell according to claim 1, wherein the Al content in the substrate is 2 atomic% or more. The integrated solar cell according to claim 1, wherein the base includes a rare earth element. A method for manufacturing an integrated solar cell including a plurality of unit cells including a semiconductor layer which functions as a light absorption layer and includes a semiconductor including a group Ib element, a group IIIb element, and a group VIb element,
(I) forming an insulating layer on at least one principal surface of the base by thermally oxidizing the base including Fe, Cr, and Al;
(Ii) forming a plurality of the unit cells connected in series above the insulating layer. The method for manufacturing an integrated solar cell according to claim 5, wherein in the step (i), thermal oxidation is performed at a temperature of 800 ° C or higher. The method for manufacturing an integrated solar cell according to claim 5, wherein the Al content in the substrate is 2 atomic% or more. The method for manufacturing an integrated solar cell according to claim 5, wherein the base contains a rare earth element. The method of manufacturing an integrated solar cell according to claim 5, further comprising a step of forming an insulating film on the insulating layer after the step (i) and before the step (ii).

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