JPH11145493A - Manufacture of thin-film solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exchange efficiency and yield rate of a thin-film solar battery with a hetero junction, to enable to mass-produce the solar battery using an existing device, and to reduce manufacturing cost of the solar battery. SOLUTION: A manufacturing method of a thin-film solar battery is provided, wherein a metal backside electrode 3, a multiple element compound semiconductor thin film 4 having a P-type conductivity and used as a light absorbing layer, a transparent and high resistant sulfur-containing zinc mixed crystal compound semiconductor thin film 5 which is formed between the semiconductor thin film 4 and a metal oxide semiconductor thin film 6 and used as an interfacial layer, a metal oxide semiconductor thin film 6, and an upper electrode 7, are successively formed on a glass substrate 2. In this case, the conversion efficiency and yield of production of the thin film solar battery can be improved by performing high temperature drying treatment, such as an annealing at 100 to 250 deg.C in the vacuum atmosphere of 1 to 100 Torr for 10 to 120 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a hetero-junction thin-film solar cell using multinary compound semiconductor thin film as a light absorbing layer, in particular Cu-III-VI ₂ Group Karukopaito semiconductor as a light absorbing layer, for example, copper indium diselenide ( CIS), copper indium gallium diselenide (CIGS) or copper indium gallium indium selenide (CIGSS), thin-film copper indium gallium indium selenide (CIGS)
The present invention relates to a method for manufacturing a thin-film solar cell having a pn heterojunction and a light-absorbing layer of a p-type semiconductor such as copper indium gallium diselenide (CIGS) having a GSS) layer as a surface layer.

[0002]

2. Description of the Related Art Conventionally, thin film solar cells of the above type have been considered to be widely practicable and are disclosed in US Pat.
No. 226, issued by Michelsen et.al, issued June 15, 1982, and cadmium sulfide (CdS) on a light absorbing layer made of CIS to provide a thin film solar cell having high conversion efficiency. It discloses growing a layer.

[0003] Among many publications aimed at developing a thin film solar cell having such a high conversion efficiency,
U.S. Pat. No. 4,610,091 (Choudray et.al, issued September 9, 1986) and U.S. Pat.
No. 5409 (1992 by Eberspacher et.al).
(Issued September 3, 2001) is important.

US Pat. No. 5,045,409 describes a method for improving selenization of a CIS thin film light absorbing layer, and US Pat. No. 4,611,091 chemically grows a solution on a CIS thin film light absorbing layer from a solution. By growing a transparent and conductive n-type semiconductor thin film layer having a wide band gap such as zinc oxide formed by metal organic chemical vapor deposition (MOCVD) on the CdS thin film,
A manufacturing method is disclosed that significantly reduces the thickness of the layer.

The above two patent specifications minimize the use of highly toxic components such as hydrogen selenide and CdS, which are considered to be extremely important in a method for manufacturing a large-area thin-film solar cell module. Disclosed are methods of manufacture that are useful for minimizing or eliminating.

The method of growing a CdS thin film chemically from a solution described in the above-mentioned US Pat. No. 4,611,091 uses a CIS thin film light absorbing layer and a higher quality than a thick CdS formed by other methods. Form a heterojunction,
In addition, it has the effect of increasing the shunt resistance, but such an improvement is attributable to the etching or selective cleaning effect of the heterojunction interface formed by immersing the CIS thin film light absorbing layer in a solution, particularly the thin film light absorbing layer surface. It is considered included.

[0007]

In recent years, attempts have been actively made or implemented to essentially eliminate toxic materials such as cadmium from thin-film solar cells. However, it has not been successful to form a high-quality heterojunction without using a toxic material such as cadmium to produce a thin-film solar cell with high conversion efficiency. For example, a zinc compound layer grown from a solution obtained by dissolving zinc acetate in ammonium hydroxide can be dried by annealing in air after film formation, and can contain zinc oxide containing a large amount of zinc hydroxide up to about 30 mol%. Since the film is a thin film, there is a problem that a hydroxyl group is present on the surface, the film density is reduced, the coating on the surface is insufficient, and a thin film layer as good as that using CdS cannot be obtained.

As a thin-film solar cell using a material which does not contain toxicity such as cadmium, a metal back electrode 2 having a p-type conductive type on a glass substrate 2 as shown in FIG. A first multi-component compound semiconductor thin film 4 serving as a light absorbing layer, formed at an interface between the first multi-component compound semiconductor thin film 4 and the second metal oxide semiconductor thin film 6,
Sulfur-containing zinc mixed crystal compound semiconductor thin film 5 which is transparent and has high resistance and is provided as an interface layer, formed on the sulfur-containing zinc mixed crystal compound semiconductor thin film 5 and opposite to the first multi-element compound semiconductor thin film Having a conductivity type, serving as a window layer,
Second metal oxide semiconductor thin film 6 having a wide band gap, being transparent and conductive, and upper electrode or scribe line 7
Were formed in this order. However, in the case of manufacturing a thin film solar cell having the above structure, particularly in a manufacturing process of a sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer, in a conventional manufacturing method, the first multi-element compound semiconductor thin film is formed. After a sulfur-containing zinc mixed crystal compound semiconductor thin film is grown by chemical growth and then dried at room temperature, device characteristics such as conversion efficiency and yield are lower than those of thin film solar cells using materials such as cadmium. Was inferior.

The present invention has been made to solve the above problems, and provides a method of manufacturing a thin film solar cell having a heterojunction using the multiplexed compound semiconductor thin film of high conversion efficiency containing no cadmium as a light absorbing layer. The purpose is to provide.

Another object of the present invention is to provide a method of manufacturing a thin-film solar cell in which the device characteristics of the thin-film solar cell having the heterojunction, that is, the conversion efficiency and the yield (yield) are improved.

Another object of the present invention is to provide a method of manufacturing a thin-film solar cell which can be mass-produced and which reduces the use and concentration of chemicals when manufacturing the thin-film solar cell having the heterojunction. And

[0012]

SUMMARY OF THE INVENTION The present invention provides a metal back electrode and a first multi-element compound semiconductor formed on the metal back electrode, having a p-type conductivity and serving as a light absorbing layer. A thin film, formed on the first multi-compound semiconductor thin film, having a conductivity type opposite to that of the first multi-compound semiconductor thin film, serving as a window layer, having a wide band gap, being transparent and having conductivity. Formed at the interface between the second metal oxide semiconductor thin film and the first multi-component compound semiconductor thin film and the second metal oxide semiconductor thin film, which is transparent, has high resistance, and serves as an interface layer. A sulfur-containing zinc mixed crystal compound semiconductor thin film,
A method for manufacturing a thin-film solar cell comprising an upper electrode,
After chemically growing the sulfur-containing zinc mixed crystal compound semiconductor thin film containing oxygen, sulfur and hydroxyl groups on the first multi-component compound semiconductor thin film from a solution, the sulfur-containing zinc mixed crystal compound semiconductor thin film is This is a method for manufacturing a thin-film solar cell in which a transparent and high-resistance interface layer is formed by drying at a high temperature in a vacuum.

In the present invention, the first multi-element compound semiconductor thin film serving as the light absorbing layer may be made of copper indium diselenide (CIS) or copper indium gallium diselenide (CI).
GS), manufacture of thin-film solar cells composed of copper-indium-gallium-diselene-copper-indium-gallium (CIGS) having a thin layer of copper-selenium-copper-indium-iodide-gallium (CIGS) as a surface layer Is the way.

The present invention is a method for manufacturing a thin-film solar cell, wherein the second metal oxide semiconductor thin film serving as the window layer is made of zinc oxide.

In the present invention, a zinc salt is used to form a sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer, and the zinc salt is one of zinc sulfate, zinc chloride and zinc acetate. This is a method for manufacturing a thin-film solar cell selected from the following.

The present invention is a method for producing a thin-film solar cell containing a sulfur-containing salt in addition to a zinc salt to form a sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer.

The present invention is a method for manufacturing a thin-film solar cell, wherein the temperature is 100 to 250 ° C. when the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum.

The present invention is a method for producing a thin-film solar cell wherein the degree of vacuum is 1 to 100 Torr when the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum.

The present invention is a method for producing a thin-film solar cell, wherein when the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum, the drying time is 10 to 120 minutes.

[0020]

Embodiments of the present invention will be described below. As a thin-film solar cell using a material that does not contain toxicities such as cadmium, a first multi-element compound having a metal back electrode, a p-type conductivity type, and serving as a light absorbing layer on a glass substrate is conventionally used. A semiconductor thin film, a sulfur-containing zinc mixed crystal compound semiconductor formed at an interface between the first multi-component compound semiconductor thin film and the second metal oxide semiconductor thin film, having high transparency and being provided as an interface layer; A thin film, formed on the sulfur-containing zinc mixed crystal compound semiconductor thin film, having a conductivity type opposite to that of the first multi-component compound semiconductor thin film, serving as a window layer, and having a wide band gap and being transparent and conductive. There is a thin film solar cell having a structure in which a second metal oxide semiconductor thin film and an upper electrode or a scribe line are sequentially formed.

When manufacturing a thin film solar cell having the above structure,
In particular, in the manufacturing process of the sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer, in the conventional manufacturing method, the sulfur-containing zinc mixed crystal compound semiconductor thin film is formed by chemical growth on the first multi-component compound semiconductor thin film. Was grown at room temperature, but in the manufacturing method of the present invention, instead of the conventional room temperature drying process, a high temperature drying process was performed in a vacuum to obtain device characteristics such as conversion efficiency. And the yield can be improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thin-film solar cell 1 comprises a glass substrate 2, a metal back electrode 3, a first multi-component semiconductor thin film 4, a sulfur-containing zinc mixed crystal compound semiconductor thin film 5, a second metal oxide semiconductor thin film 6, This is a structure in which upper electrodes or scribe lines 7 are sequentially formed.

The present invention relates to a method for manufacturing a thin-film solar cell. The thin-film solar cell 1 has a structure as shown in FIG. 1, and a metal back electrode 3, a first multi-component compound semiconductor thin film 4, a sulfur-containing zinc mixed crystal compound semiconductor thin film 5, a second metal The oxide semiconductor thin film 6 and the upper electrode or scribe line 7 are sequentially formed in a laminated structure.

Further, details of the thin-film solar cell 1 will be described.
The glass substrate 2 has a thickness of 1 to 3 mm. The metal back electrode 3 is made of a metal such as molybdenum, titanium or tantalum or a metal laminated structure having a thickness of 1 to 2 μm. The first multi-element compound semiconductor thin film 4 serves as a light absorbing layer and has a thickness of 1 to 3 of a p-type conductivity type Cu-III-VI group ₂ chalcopyrite structure.
3 μm thin film, CIS, CIGS, CIGSS or CI
It is composed of a thin film of a multiple compound semiconductor such as CIGS having a GSS layer as a surface layer. Sulfur-containing zinc mixed crystal compound semiconductor thin film 5
Are high resistance, serve as an interfacial layer, and use a zinc salt, specifically a solution selected from one of zinc sulfate, zinc chloride or zinc acetate to form this thin film. If necessary, a sulfur-containing salt can be used in addition to zinc acid. The second metal oxide semiconductor thin film 6 is provided as a window layer, and is made of zinc oxide having a wide bandgap having an n-type conductivity type and a thickness of 0.5 to 3 μm which is transparent and conductive.
An upper electrode or scribe line 7 is formed on an exposed surface of the second metal oxide semiconductor thin film 6.

The method for manufacturing a thin-film solar cell of the present invention is characterized by the following steps for preparing a sulfur-containing zinc mixed crystal compound semiconductor thin film 5. After chemically growing a thin film containing oxygen, sulfur and hydroxyl groups from a solution containing a zinc salt or a sulfur-containing salt on the first multi-component compound semiconductor thin film 4 serving as a light absorbing layer, By performing a high-temperature drying treatment, a high-resistance sulfur-containing zinc mixed crystal compound semiconductor thin film 5 is formed.

The vacuum high-temperature drying process in the method for manufacturing a thin-film solar cell will be described in detail below. The first multi-component semiconductor thin film 4 serving as a light absorbing layer is immersed in a solution containing a zinc salt or a sulfur-containing salt to form a sulfur-containing zinc mixed crystal compound semiconductor on the first multi-component semiconductor thin film 4. After chemically growing the thin film 5, the grown sulfur-containing zinc mixed crystal compound semiconductor thin film 5 is annealed in a vacuum of 1 to 100 Torr at a set temperature of 100 to 250 ° C. for 10 to 120 minutes to dry and At the same time as converting zinc hydroxide in the film to zinc oxide, it promotes the reforming of the surface of the first multi-component compound semiconductor thin film 4 with sulfur.

The test results of the element characteristics of the thin-film solar cell 1 manufactured by the method for manufacturing a thin-film solar cell of the present invention will be described below.

The effects of the vacuum drying process on conversion efficiency and yield (yield) will be described with reference to Tables 1 to 4.

Influence on conversion efficiency and yield (yield) by processing time in vacuum drying processing

[0030]

[Table 1]

The above Table 1 shows a normal-temperature drying treatment (temperature: 200 ° C., pressure: normal pressure, drying time: 15) which is a conventional production method.
2) shows the element characteristics of the thin-film solar cell manufactured according to the above method.

[0032]

[Table 2]

Table 2 shows that temperature: 200 ° C., pressure: 30
This shows the device characteristics of a thin-film solar cell manufactured at a constant Torr while varying the drying time.

A normal temperature drying treatment (temperature: 200 ° C., pressure: normal pressure, drying time: 1) which is a conventional production method shown in Table 1 above.
5 minutes), the temperature: 200 ° C., the pressure: 30 Torr, as shown in Table 2 above.
In the case of thin-film solar cells manufactured by changing the drying time,
In all the drying times of 15 to 120 minutes, both the conversion efficiency and the standard deviation β are improved. And the drying time is 15
Between ６０60 minutes, the conversion efficiency and standard deviation β improve with increasing drying time.

The standard deviation β is the variation α of the conversion efficiency.
And the variation α = (conversion efficiency × β) ÷ 2.

For example, a comparison between the one manufactured by the conventional manufacturing method shown in Table 1 and the one with a drying time of 60 minutes shown in Table 2 shows that the conversion efficiency of the conventional one is 10.0 ± 10%.
While 1.105 (10.0 × 0.0221 ÷ 2) solar cells can be obtained with a yield (yield) of 65%,
When the drying time is 60 minutes, the conversion efficiency is 11.0 ± 0.
A 0462 (11.0 × 0.0084 ÷ 2) solar cell has a 65% yield (yield), and both efficiency and yield (yield) are improved.

The yield (yield) of the two is the same.
Even if it is 5%, the variation α is 0.0462.
On the other hand, since the former is 1.105, the latter substantially has a higher yield (yield).

However, when the drying time is 60 minutes, the conversion efficiency and the standard deviation β decrease when the drying time reaches 120 minutes. β is improving.

The reason why the conversion efficiency and the standard deviation β decrease when the drying time is too long is considered to be the deterioration of the interface state.

Effect of drying temperature on conversion efficiency and yield (yield) in vacuum drying process

[0041]

[Table 3]

Table 3 shows that time: 60 minutes, pressure: 30 To.
rr Indicates the device characteristics of a thin-film solar cell manufactured at a constant temperature while varying.

As shown in Table 1 above, a normal temperature drying treatment (temperature: 200 ° C., pressure: normal pressure, drying time:
15 minutes), the time: 60 minutes, the pressure: 30 Torr, as shown in Table 3 above,
In the case of the thin-film solar cell manufactured by changing the temperature, the conversion efficiency and the standard deviation β are improved over the conventional one shown in Table 1 at all the drying temperatures of 100 to 230 ° C. 2
Up to 00 ° C., the conversion efficiency and the standard deviation β increase with an increase in the temperature. However, as the temperature increases to 230 ° C., the conversion efficiency and the standard deviation β are more excellent than those of the prior art shown in Table 1. , But slightly lower. The cause is considered to be the influence of interdiffusion of the interface due to the temperature rise.

Effect of Drying Pressure on Conversion Efficiency and Yield (Yield) in Vacuum Drying

[0045]

[Table 4]

Table 4 shows that time: 60 minutes, temperature: 200
This shows the device characteristics of a solar cell manufactured at a constant ° C and a varied drying pressure.

As shown in Table 1, a normal-temperature drying treatment (temperature: 200 ° C., pressure: normal pressure, drying time: 15) which is a conventional production method is performed.
Min), the solar cell manufactured by changing the drying pressure at a constant time of 60 minutes and at a temperature of 200 ° C. as shown in Table 4 above has a drying pressure of 1 to
In the range of 50 Torr, both the conversion efficiency and the standard deviation β are improved as compared with the conventional one shown in Table 1. But 100 Torr
Becomes almost the same value as the conventional one shown in Table 1.
This is considered to be because the effect of drying moisture decreases as the pressure increases.

In view of the above experimental examples, the processing time was determined for the entire time range of the experiment, ie, 15 to 12 hours.
In the range of 0 minutes, the drying temperature was in the entire temperature range tested, that is, in the range of 100 to 230 ° C., and the drying pressure was in the range of 1 to 100 Torr. And the standard deviation β are both improved.

[0049]

According to the manufacturing method of the present invention, a thin-film solar cell having high conversion efficiency and high yield can be manufactured without using toxic materials such as cadmium.

Further, since the manufacturing method of the present invention is manufactured using an existing relatively simple apparatus called a vacuum high-temperature drying process, when manufacturing a thin-film solar cell, it can be mass-produced and the amount of chemicals used can be reduced. And the concentration can be reduced, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic structure of a thin film solar cell to be manufactured by a manufacturing method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Thin film solar cell 2 Substrate 3 Metal back electrode 4 First multi-component compound semiconductor thin film (light absorption layer: p-type semiconductor) 5 Sulfur-containing zinc mixed crystal compound semiconductor thin film (interface layer) 6 Second metal oxide semiconductor thin film ( (Window layer: n-type semiconductor) 7 Upper electrode or scribe line

Claims (8)

[Claims] 1. A metal back electrode, a first multi-compound semiconductor thin film formed on the metal back electrode, having a p-type conductivity, and serving as a light absorbing layer; A second metal oxide semiconductor formed on the compound semiconductor thin film, having a conductivity type opposite to that of the first multi-element compound semiconductor thin film, serving as a window layer, and having a wide bandgap, and being transparent and conductive; A thin film, the first multi-component compound semiconductor thin film, and a second
A thin-film solar cell manufacturing method comprising: a sulfur-containing zinc mixed crystal compound semiconductor thin film formed at an interface between a metal oxide semiconductor thin film of the present invention, which is transparent, has high resistance and serves as an interface layer, and an upper electrode In the above, after the sulfur-containing zinc mixed crystal compound semiconductor thin film containing oxygen, sulfur and hydroxyl groups is chemically grown from a solution on the first multi-component compound semiconductor thin film, the sulfur-containing zinc mixed crystal compound semiconductor thin film To
A method for producing a thin-film solar cell, wherein a transparent and high-resistance interface layer is formed by drying at a high temperature in a vacuum. 2. The method according to claim 1, wherein the first multi-element compound semiconductor thin film serving as the light absorbing layer is made of copper indium diselenide, copper indium gallium diselenide (CIGS),
2. The thin film according to claim 1, comprising copper indium gallium iodide or copper indium gallium diselenide (CIGS) having a thin film of diselene-copper indium-gallium iodide (CIGSS) as a surface layer. Solar cell manufacturing method. 3. The method according to claim 1, wherein the second metal oxide semiconductor thin film serving as the window layer is made of zinc oxide. 4. A zinc salt is used for forming a sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer, wherein the zinc salt is formed from one of zinc sulfate, zinc chloride and zinc acetate. 2. The method according to claim 1, wherein the selection is performed.
A method for manufacturing the thin-film solar cell according to the above. 5. The thin-film solar cell according to claim 1, further comprising a sulfur-containing salt in addition to the zinc salt to form the sulfur-containing zinc mixed crystal compound semiconductor thin film serving as the interface layer. Production method. 6. The method according to claim 1, wherein when the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum, the temperature is 100 to 250 ° C.
6. The method for producing a thin-film solar cell according to 4 or 5. 7. The method according to claim 1, wherein when the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum, the degree of vacuum is 1 to 100 Torr.
6. The method for producing a thin-film solar cell according to 4 or 5. 8. When the sulfur-containing zinc mixed crystal compound semiconductor thin film is dried at a high temperature in a vacuum, the drying time is 10 minutes.
1 to 2, wherein the time is from 120 to 120 minutes.
6. The method for producing a thin-film solar cell according to 3, 4, or 5.