JPH0992861A - Photovoltaic element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form at low cost a high-adhesion metal layer and transparent conductive layer, without using expensive apparatus by depositing first and second metal layers and transparent conductive layer from acid water solns. SOLUTION: On an Fe-contained support 201 a first metal layer 202, second metal layer 203, first transparent conductive layer 204, semiconductor layer 205 and second transparent conductive layer 206 are laminated. The layer 202 is made by dipping a support 201 in a water soln. contg. S ions and Zn ions or a water soln. contg. Cl ions, Zn ions and ammonia to plate Zn on the support used as a cathode. The layer 203 is made by dipping the support 201 in a water soln. contg. sulfate ions and Cu ions to plate Cu with the support used as a cathode. The layer 204 is made by dipping the support 201 with the layer 203 formed thereon in a water soln. contg. Zn ions and nitrate ions to plate ZnO2 on the support used as a cathode 203.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a photovoltaic device. More specifically, non-single-crystal semiconductor materials containing silicon atoms and germanium atoms, such as hydrogenated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated amorphous silicon carbide, microcrystalline silicon or polycrystalline silicon. The present invention relates to a method of manufacturing a photovoltaic element having the improved light reflection layer.

A photovoltaic element manufactured by the method of the present invention is
For example, it is applied to solar cells, sensors, image pickup devices, etc., and further, the devices are connected in multiple stages as an array and should be stably operated in an outdoor environment for a long period of time, such as a house, a collective building or a system. It is preferably applied to a solar power generation system or the like that is used by connecting to.

[0003]

2. Description of the Related Art Conventionally, photovoltaic devices made of hydrogenated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated amorphous silicon carbide, microcrystalline silicon or polycrystalline silicon, etc. To improve the light collection rate,
Backside reflective layers have been utilized. It is desirable that such a reflective layer has an effective reflective characteristic at a wavelength near the band edge of the semiconductor material where the absorption is small, that is, 800 nm to 1200 nm. A metal layer made of gold, silver, copper, or the like can be given as an example that sufficiently satisfies this condition. Further, in order to prevent the characteristic deterioration due to the shunt path, a technique of providing a layer made of a translucent material having conductivity, that is, a transparent conductive layer, is used between the metal layer and the semiconductor layer. Generally, the metal layer and the transparent conductive layer are
For example, it is formed by a vacuum deposition method or a sputtering method, and
_SC (short circuit current: current generated by sunlight is a current that is collected and output to the electrodes by the internal electric field when the solar cell is short-circuited, and increases when sunlight is effectively used), and improved by 1 mA or more Has been obtained.

However, the above conventional technique has the following problems. (1) Although the metal layer and the transparent conductive layer formed by vacuum vapor deposition or sputtering have sufficient electric and optical characteristics, there is a problem related to the adhesiveness such that they are easily peeled off. The long-term reliability remains uncertain when the photovoltaic element is installed outdoors for a long period of time to generate electricity.

(2) The depreciation cost of the vacuum device is large,
The low utilization efficiency of materials has been a major impediment to the industrial application of solar cells, with the cost of photovoltaic devices using these technologies being extremely high. Due to its pollution-free nature, governments are promoting the next generation power generation system, power companies and consumers who want to reduce power generation costs, and industries that want to accumulate installation results and use them as a foothold for the next technology. We are eager for lower prices.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for manufacturing a photovoltaic element, which can inexpensively form a metal layer having excellent adhesion and a transparent conductive layer in contact with the metal layer. The purpose is to contribute to.

Another object of the present invention is to provide a method for stably forming a metal layer and a transparent conductive layer in contact with the metal layer, which is not inferior to conventional methods in spite of being inexpensive.

[0008]

A method of manufacturing a photovoltaic element according to the present invention comprises: a support containing iron; a first metal layer;
A second metal layer, a first transparent conductive layer, a semiconductor layer, and a method for manufacturing a photovoltaic element comprising a second transparent conductive layer sequentially stacked, wherein the first metal layer, the second Both the metal layer and the first transparent conductive layer are deposited from an acidic aqueous solution.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In claim 1 of the present invention, a first metal layer, a second metal layer, a first transparent conductive layer, a semiconductor layer, and a second layer are provided on a support containing iron. In the method for producing a photovoltaic element, which comprises sequentially laminating transparent conductive layers of, the first metal layer, the second metal layer, and the first transparent conductive layer, both from an acidic aqueous solution. Because of the precipitation, the expensive thin film forming apparatus by the vacuum vapor deposition method or the sputtering method, which is conventionally used for producing each layer, becomes unnecessary. Therefore,
Each layer can be formed inexpensively.

According to the second aspect of the present invention, since the support containing iron is etched with an acidic solution, the surface of the support can be made uneven. As a result, by sequentially laminating the first metal layer, the second metal layer, and the first transparent conductive layer on this support, each layer is provided with an uneven shape. Therefore, each layer can confine the reflected light on the back surface, so that the incident light can be effectively used.

In claim 3 of the present invention, since the first metal layer is zinc and the second metal layer is copper, light in the near-infrared region effective as back surface reflected light is reflected without loss. It is possible to realize a layer having a high effect of confining reflected light with long-term reliability.

According to a fourth aspect of the present invention, since the first transparent conductive layer is zinc oxide, it has good transparency to light in the near-infrared region, which is effective as reflected light, and has crystal grains of a wavelength order. It is possible to greatly increase the scattering component of the reflected light by forming the light beam, and as a result, it is possible to increase J _SC .

Embodiments of the present invention will be described below with reference to the drawings.

(Photovoltaic Element) As the photovoltaic element according to the present invention, the one shown in the schematic sectional view of FIG. 2 can be mentioned. In FIG. 2, 201 is a support containing iron, 2
02 is a first metal layer, 203 is a second metal layer, 204 is a first transparent conductive layer in contact with the second metal layer 203, 20
5 is a semiconductor layer, and 206 is a second transparent conductive layer.

(Support Containing Iron) As the support 201 containing iron according to the present invention, its surface is etched with hydrofluoric acid / nitric acid, and a plate-like or foil-like one is used. .
It is also possible to make it into a roll for continuous treatment. In order to prevent the generation of rust on the end faces, stainless steel containing nickel or chromium may be used. Etching is 1 μm
The purpose is to form irregularities to some extent, which is for confining the well-known back surface reflected light.

The support 201 containing iron is determined by the strength, bendability, rust resistance of the end, etc. of the support.
It may include carbon, silicon, magnesium, chromium, nickel, and the like. In particular, ferritic stainless steels containing nickel and martensitic stainless steels containing nickel / chromium are easy to handle because they do not require rust prevention treatment.
Further, from the viewpoint of cost, cold rolled steel plate can be used. Further, the shape may be a foil, a plate, etc. in addition to a steel plate wound in a roll type.

(First Metal Layer) The first metal layer 202 according to the present invention is prepared by immersing the support in an aqueous solution containing sulfate ion and zinc ion or an aqueous solution containing chloride ion, zinc ion and ammonia. , Is formed by plating zinc with the support as a cathode.

Layers can be formed, for example, with the apparatus shown in FIG. Reference numeral 301 in the figure denotes an acid resistant container, which holds an aqueous solution containing sulfate ions and zinc ions or an aqueous solution 302 containing chlorine ions, zinc ions and ammonia. Three
Reference numeral 03 denotes a support containing iron used in the present invention, which serves as a cathode.

304 is a counter electrode, and zinc is used in this case. The counter electrode 304 serves as an anode. The support 303 which is a cathode and the counter electrode 304 which is an anode are
It is connected to a power source 305 via a load resistor 306 so that a substantially constant current flows.

A suction bar 308 having a plurality of solution inlets and an injection bar having a plurality of solution outlets are also provided in order to stir the solution to reduce layer formation unevenness and increase the layer forming speed to improve efficiency. 307, a solution circulation pump 311, a suction solution pipe 309 connecting the solution suction bar 308 and the solution circulation pump 311, a solution injection bar 307, and a solution circulation pump 3
A solution circulation system including an injection solution pipe 310 connecting 11 is used.

The solution 302 is preferably adjusted to a pH of 1.5 to 4.5 in the case of an aqueous solution containing sulfate ions and zinc ions, and in the case of an aqueous solution containing chlorine ions, zinc ions and ammonia. It is preferable to adjust the pH to 4.0 to 7.0. The temperature range is preferably 10 to 70 ° C. for an aqueous solution containing sulfate ions and zinc ions, and 10 to 40 ° C. for an aqueous solution containing chlorine ions, zinc ions and ammonia. Further, the cathode current density is 2 to 8 in the case of an aqueous solution containing sulfate ions and zinc ions.
0 A / cm ² and 0.05 to 20 A / cm ^{2 in} the case of an aqueous solution containing chlorine ions, zinc ions and ammonia
It is said.

(Second Metal Layer) For the second metal layer 203 of the present invention, the support 201 is immersed in an aqueous solution containing sulfate ions and copper ions, and copper is plated using the support as a cathode. Formed by. As with the first metal layer, the layer can be formed with the apparatus shown in FIG. The acid resistant container 301 holds an aqueous solution 302 containing sulfate ions and copper ions. Copper is used for the counter electrode 304. The stirring of the solution is performed by the method already described using a circulation pump. The temperature range of the solution 302 containing sulfate ions and copper ions is preferably 10 to 70 ° C.
The cathode current density is 0.05 to 20 A / cm ² .

(First Transparent Conductive Layer) The first transparent conductive layer 204 according to the present invention is formed by immersing a support having the second metal layer 203 in an aqueous solution containing zinc ions and nitrate ions. And using the support as the cathode 303 in the apparatus of FIG.
It is formed by depositing zinc oxide. Zinc is used for the counter electrode 304 which is an anode.

The pH of the solution is preferably adjusted to 4.0 to 6.3, and the temperature range is preferably 40 to 70 ° C. The cathode current density is 0.002 to 10 A / cm ² ,
Particularly, 0.01 to ^{2 A} / cm ² is preferable. Acetic acid and nitric acid can be added to stabilize the pH. Further, benzoic acid, formic acid, citric acid, glycolic acid, which can be mixed in the solution as an additive for stabilizing the pH,
Succinic acid, oxalic acid, etc. are used as appropriate.

(Washing) Etching of the support 201, formation of the first metal layer 202, formation of the second metal layer 203, and formation of the first transparent conductive layer 204 are all processes involving an aqueous solution. , Can be continuously performed through a washing process. In the case of a vacuum process in which the semiconductor layer 205 does not like water, a drying process is performed after forming the first transparent conductive layer 204. Drying may be performed by heating with an IR heater in the atmosphere, drying with warm air using hot oxygen, vacuum drying, or the like.

The method of manufacturing a photovoltaic element according to the present invention comprises:
It is characterized in that it can be kept acidic in all solution processes, which minimizes deterioration of the bath due to carry-in of liquid during washing with water or when the support is transferred to the tank for the next process. be able to. Further, the path of washing in the intermediate step can be shortened, which is extremely advantageous in the construction of the manufacturing apparatus.

(Semiconductor Layer and First Transparent Conductive Layer) The semiconductor layer 205 according to the present invention has at least one of a pn junction, a pin junction, a Schottky junction, and a hetero junction, and is resistant to incident light. Correspondingly, electromotive forces are generated on both sides of the layer. Current generated by the electromotive force is generated by the second transparent conductive layer 206 formed on the upper side, the first transparent conductive layer 204 formed on the lower side, the first metal layer 202, and the second metal layer 203. The support 201 and the load connected to the support 201 flow through the configured current path. The second transparent conductive layer 206 formed on the upper side also serves as an antireflection layer, so that the layer thickness is limited and may not have sufficient current capability. In that case, a grid electrode is further arranged. .

The semiconductor layer 205 has LF discharge, RF discharge,
A pn junction and a pin using amorphous or crystalline silicon, amorphous or crystalline silicon / germanium, amorphous or crystalline silicon carbide, etc. by a CVD method for exciting a gas by VHF discharge or microwave discharge. In addition to those having a junction, a Schottky junction, and a heterojunction, those having a structure called a tandem or triple in which they are laminated can be used.

The second transparent conductive layer 206 is formed by vacuum evaporation,
Sputtering, reactive sputtering, is formed by a CVD _{method, ITO, In 2 O 3,} SnO 2, ZnO, etc. TiO ₂ can be used. Of course, they may be used in a laminated state.

Light incident from above the photovoltaic element enters the semiconductor layer 205 in an antireflection state at the central wavelength of the second transparent conductive layer 206, and generates photocarriers in the semiconductor layer 205. Then, the generated photocarriers are transferred to the second transparent conductive layer 20 according to the two charges.
6 or through the first transparent conductive layer 204, the second metal layer 203 and the first metal layer 202, and is collected on the support 201 side. The light not absorbed by the semiconductor layer 205 is
The light is reflected by the second metal layer 203 through the first transparent conductive layer 204, and returns to the semiconductor layer 205 through the first transparent conductive layer 204 again. Therefore, the second metal layer 203
The reflectivity of is extremely important.

Light having a wavelength much longer than the band edge of the semiconductor layer 205 is hardly absorbed by the semiconductor layer 205 even if it is reflected and returned to the semiconductor layer 205. The reflectivity of 203 is the semiconductor layer 205.
It is necessary to be excellent near the absorption edge of.

Further, when the second metal layer 203 has irregularities or the first transparent conductive layer 204 has irregularities, the reflection on the second metal layer 203 and the first transparent conductive layer 204 The refraction of light causes the light to bounce back and take a large optical path, so that the amount of light absorbed in the semiconductor layer 205 can be increased by an effect usually called light confinement, resulting in an increase in photocurrent. This unevenness is preferably on the order of the wavelength at the absorption edge of the semiconductor layer 205.

In the unevenness according to the present invention, the first unevenness is formed when the support 201 is etched, and the subsequent unevenness is formed when the first metal layer 202 and / or the second metal layer 203 is formed. When the transparent conductive film is formed, unevenness is formed. Unevenness formed at the interface between the second metal layer 203 and the first transparent conductive layer 204,
The uneven shape formed by the first transparent conductive layer 204 and the semiconductor layer 205 has a different shape than the copying shape, which gives a preferable result for increasing the current of the photovoltaic element.

As described above, the photovoltaic element is required to operate stably for a long period in the outdoor environment. For this purpose, sufficient durability against mechanical bending is required depending on temperature / humidity and installation conditions. Due to the fate that the photovoltaic element is placed under sunlight, the temperature changes from a high temperature close to 100 ° C in the daytime in summer to −30 at dawn in winter.
We have to deal with the environment below ℃. Furthermore, there is a temperature change of several tens of degrees Celsius during one day, and the laminated layers 2
Frequent peeling occurs at the interface because 02-206 have different coefficients of thermal expansion. Especially, when the film thickness becomes large, this obstacle becomes remarkable.

The semiconductor layer 205 composed of amorphous silicon or amorphous silicon-germanium has a thickness of about several hundreds of nm, the second transparent conductive layer 206 has a thickness of about 60 nm, and the first transparent conductive layer 204. Is about 1 μm, and the second metal layer 203 has a thickness of 200 to 500 nm. Therefore, when peeling off, first between the first transparent conductive layer 203 and the second metal layer 203, and then the first metal layer. 202 and support 20
Peeling is observed between 1 and 1.

Such peeling is performed by preparing an underlayer at the interface as a clean surface and forming a film, forming irregularities on the ground surface of the interface to increase the surface area and improving adhesion, and thermal expansion / It is prevented by dividing into small areas so that the heat shrinkage does not reach the whole.

As a concrete method according to the present invention, the surface of the support 201 containing iron is removed by etching with an aqueous solution containing hydrofluoric acid and nitric acid to form an uneven surface. Further, the first metal layer 202 and / or the second metal layer 203 deposited on this is formed to be uneven. Further, the first transparent conductive layer 204 deposited thereon has crystal grains of the order of the wavelength of light grown, and since the crystal grains are filled with different phases, thermal expansion and contraction are all performed. There are no layers. This is also an important point when the support is bent by applying a physical force, and when the support is flexible and a flexible photovoltaic element is manufactured, Particularly advantageous. In addition, the film formation of the second metal layer 203 and the first transparent conductive layer 204 according to the present invention does not require a high temperature such as several hundreds of degrees Celsius to obtain the necessary unevenness, and a large thermal shock is originally applied. Not a thing.

According to the experiments conducted by the present inventors, when the temperature cycle is repeated in a humid environment, a crack is introduced into the first transparent conductive layer 204, and this crack becomes a water entry path, and the photovoltaic element. In a module configured by connecting several sub-modules in series with each other, a reverse voltage is applied to the photovoltaic element in a state called a partial shade in which only a part is shaded, and the second metal layer 203 is formed. It was revealed that the formed metal causes dendritic growth based on electrochemical migration, resulting in shunting of the device.

This occurs when the first transparent conductive layer 204 is densely and hardly formed over all the layers, and is particularly noticeable when it is formed by a vacuum high temperature process such as sputtering. A shunt for a device based on such tree growth is
After that, it will not recover even if the environmental humidity drops and the water disappears. First transparent conductive layer 204 based on the manufacturing method of the present invention
Since is originally grown from an aqueous solution, it relaxes against water, and the above-mentioned problems can be minimized.

[0040]

EXAMPLES The method for manufacturing a photovoltaic element according to the present invention will be described below in detail based on examples, but the present invention is not limited to these examples.

Example 1 In this example, the manufacturing apparatus shown in FIG. 1 was used to form a first metal layer, a second metal layer, and a first transparent conductive layer. A method of manufacturing the photovoltaic element having the layer structure shown will be described.

In FIG. 1, the support is etched with an acidic solution, and the first metal layer, the second metal layer and the first transparent conductive layer are all deposited on the support from an acidic aqueous solution. It is the schematic of the apparatus used for doing. As the support, a thin plate of stainless steel 430BA configured in a roll shape was used.

In FIG. 1, 101 is a feed roller, which feeds the support roll 103 and finally winds it up on a winding roller 102. Sending roller 1
01 and the take-up roller 102 between the etching tank 10
6, water washing tank 110, first metal layer forming bath 117, water washing tank 124, second metal layer forming bath 131, water washing tank 13
8, a transparent conductive layer forming bath 145, a water washing bath 153, and a drying oven 156 were sequentially provided. In each tank, rollers 104 and 10 for controlling the conveyance path of the support roll are provided.
9, 114, 120, 123, 128, 134, 13
7, 142, 148, and 152 are provided.

The process speed of the support roll 103 was 20 cm / min. The tension applied to the support roll 103 was 10 kg. The tension was controlled by a tension adjusting clutch (not shown) incorporated in the winding roller 102.

The process steps will be described below. (1) The support roll 103 was passed through the acidic etching bath 106 and etched with hydrofluoric acid and nitric acid. The acidic etching bath used was a mixture of nitric acid 5, hydrofluoric acid (46% hydrofluoric acid, the same applies hereinafter) 3, and acetic acid 1, and the liquid temperature was room temperature.

(2) Support roll 1 after step (1)
03 was conveyed to the water washing tank 110 via the conveyance roller 107. Washing with water was thoroughly performed using the washing showers 108 and 111. At that time, it is preferable that the amount of water is at least 2 liters per minute.

(3) Support roll 1 after step (2)
03 is transported to the first metal layer forming bath 117 via the transport rollers 112 and 113, and is etched.
A first metal layer was formed on top of 3. The first metal layer forming bath 116 is a mixture of 300 g of zinc sulfate and 30 g of ammonium sulfate in 1 liter of water, and the liquid temperature is 5
The temperature was controlled to 0 to 60 ° C. The pH of the liquid was in the range of 3.0 to 4.0.

A zinc plate was used as the anode. In this apparatus, since the support roll 103 is set to the ground potential, the layer formation is controlled by reading the current in the anode zinc plate. In this example, the current density was 30 A / cm ² . The layer formation speed is 5n
m / s, and the layer thickness of the first metal layer 202 formed in the first metal forming bath was 200 nm. Then, it is conveyed to the washing tank 124 via the conveying roller 121. The washing showers 122 and 125 were thoroughly washed with water.

(4) Support roll 1 after step (3)
03 was conveyed to the 2nd metal layer formation bath 131 via the conveyance rollers 126 and 127, and the 2nd metal layer was formed on the 1st metal layer. Second metal forming bath 131
Is a mixture of 150 g of copper sulfate and 50 g of sulfuric acid in 1 liter of water, and the liquid temperature was controlled at 20 ° C to 25 ° C. A copper plate was used as the anode. The current density of this anode is 3A
/ Cm ² . Thus, a second metal layer having a layer thickness of 300 nm was obtained.

(5) Support roll 1 after step (4)
03 was washed with water in the washing tank 138. Then, the support roll 103 was transported to the transparent conductive layer forming bath 145 via the transport rollers 140 and 141, and the first transparent conductive layer 204 was formed on the second metal layer. The transparent conductive layer forming bath 144 was prepared by adding zinc nitrate.6 in 1 liter of water.
It was a mixture of 30 g of water salt and 10 ml of nitric acid, and the liquid temperature was kept at 60 ° C. The pH of the liquid was set to 5.2 to 5.8. Zinc whose surface was buffed was used as the counter electrode. The current density applied to the counter electrode was 2 A / cm ² . The layer forming rate was 18 nm / s, and the layer thickness of the first transparent conductive layer 204 formed in the transparent conductive layer forming bath was 1 μm.

(6) Support roll 1 after step (5)
03 was washed with water in the washing tank 153. After that, the support roll 103 passes through the transport roller 155, and then the drying furnace 15
Sent to 6. The drying furnace 156 includes a warm air nozzle 157 and an infrared heater 158.
Then I went to water refilling at the same time. The temperature of the warm air in the warm air nozzle 157 was set to 150 ° C. Also, infrared heater 15
The temperature of 8 was 200 ° C.

(7) The support roll 103 that has undergone the drying process of the process (6) has the first metal layer 202, the second metal layer 203, and the first transparent conductive layer on the support 201 containing iron. Rolling-up roller 1 with the elastic layer 204 formed
It was wound up in 02.

The first metal layer forming bath 117 and the second metal layer forming bath 131 described above were agitated by air, and the transparent conductive layer forming bath 145 was mechanical agitated. In addition, the pH of the baths was constantly monitored by a pH meter having a temperature correction using glass electrodes in all three tanks. Zinc sulfate is used in the first metal layer forming bath 117, copper sulfate and ammonia are used in the second metal forming bath 131, and the transparent conductive layer forming bath 14 is used.
In 5, the pH in the bath was controlled by adding nitric acid.

(8) The first metal layer 2 is formed on the substrate formed by the steps (1) to (7), that is, the support 201.
02, the second metal layer 203, and the first transparent conductive layer 2
A semiconductor layer 205 having a triple structure was formed on a substrate in which 04 was sequentially laminated by a roll-compatible CVD device.

(9) Using a mixed gas of silane, phosphine, and hydrogen, the substrate was heated to 340 ° C., and RF of 400 W was applied.
Power is applied to form an n-type layer, and then a mixed gas of silane, germane, and hydrogen is used to bring the substrate temperature to 450 ° C. and microwave power is applied to form an i-type layer. At a temperature of 0 ° C., a p-type layer was formed from a mixed gas of boron trifluoride, silane and hydrogen to form a bottom pin layer.

(10) Same as (9) above except that the mixing ratio of silane and germane is increased when forming the i layer.
A middle pin layer was formed. (11) A top pin layer was formed in the same manner as in (9) above, except that silane and hydrogen were used when forming the i layer.

(12) A second transparent conductive layer 206 made of ITO was deposited on the semiconductor layer 205 formed in steps (8) to (11). As the deposition device, a roll-compatible sputtering device was used. (13) Perform electrode extraction treatment using silver paste,
The fabrication of the photovoltaic device was completed.

A simulator lamp was irradiated on the photovoltaic element manufactured by the above steps (1) to (13) to examine the photoelectric conversion characteristics.

As a result, compared with the photovoltaic element in which copper and zinc oxide were deposited on stainless steel by a sputtering device,
It was found that the photovoltaic element manufactured in this example had an energy conversion efficiency of 1.12 times.

Next, the photovoltaic element was changed to 85 ° C.-85% R.
The sample was placed in an H environment test box, a reverse bias of 1 V was applied, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic element when copper and zinc oxide were deposited on stainless steel by a sputtering apparatus approached an unusable shunt level in 10 minutes and became unusable in 1 hour. On the other hand, the photovoltaic element manufactured in this example was able to maintain a usable shunt level for 15 hours.

In this example, as the first metal forming bath 116, an aqueous solution of 300 g of zinc sulfate and 30 g of ammonium sulfate in 1 liter of water was selected.
50 to 450 g and ammonium sulfate can be used in the range of 5 to 50 g. Other buffering agents include magnesium sulfate, sodium sulfate, aluminum sulfate, sodium acetate, sodium chloride, boric acid and the like. As the amount of these buffers, 1 to 80 g can be used.

In this example, the transparent conductive layer forming bath 14 is used.
4, 30 g of zinc nitrate hexahydrate in 1 liter of water,
An aqueous solution containing 10 ml of nitric acid was selected, but 1 g to 80 g of zinc nitrate hexahydrate, no nitric acid, or 50 m
1 may be added as an upper limit, or 3 to 20 ml of acetic acid may be added for the purpose of facilitating pH control. The unevenness of the formed film depends on the temperature and the film formation speed, and when the layer is slowly formed at a high temperature, a relatively flat layer having good crystal orientation and good adhesion is obtained. When the layer is formed at a low temperature and at a high speed, the layer has large irregularities. These should be selected according to the wavelength of light that is expected to have a light confinement effect necessary for the semiconductor layer 205.

Further, in the present example, the semiconductor layer 205 has an example of a triple structure having a pin structure, but any method other than the CVD method can be applied as long as a thin film can be formed at several 100 ° C. Examples of the material of the semiconductor layer 205 to which the above-described method for manufacturing a photovoltaic element can be applied include:
Examples thereof include ZnS, ZnSe, crystalline silicon, CuInSe and the like.

Example 2 This example is different from the example in that the temperature of each water washing and each bath was set to about 50 ° C. in all steps.

However, the etching bath is 3 nitric acid, 2 hydrofluoric acid, and vinegar.
Acid 3 is mixed and the first metal layer forming bath and the second metal layer forming bath
The same metal layer forming bath as in Example 1 was used as the transparent conductive layer.
The forming bath 139 has 3 liters of zinc nitrate hexahydrate in 1 liter of water.
Use 0g, nitric acid 10ml, acetic acid 5ml
Was. The current density is 2 A / c in the metal layer forming bath.
m ², 0.4 A / cm in transparent conductive layer forming bath 139²age
Was. At this time, the layer formation rate of the first metal layer 202 is 7 nm /
s, the layer thickness is 100 nm, and the layer shape of the second metal layer 203 is
First transparent with a growth rate of 5 nm / s and a layer thickness of 200 nm
Layer formation rate of the conductive layer 204 is 1 nm / s, layer thickness is 1200
nm.

On the first transparent conductive layer 204 thus formed, a semiconductor layer 205 having a triple structure was formed by the same method as in Example 1. Other points were the same as in Example 1.

The photovoltaic element manufactured in this example was irradiated with a simulator lamp to examine the photoelectric conversion characteristics.
The measurement conditions were the same as in Example 1.

As a result, as compared with the photovoltaic element when copper and zinc oxide were deposited on stainless steel by a sputtering device,
It was found that the photovoltaic element manufactured in this example had an energy conversion efficiency of 1.07 times.

Next, the photovoltaic element was changed to 85 ° C.-85% R.
The sample was placed in an H environment test box, a reverse bias of 1 V was applied, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic element manufactured in this example could maintain a shunt level usable for 17 hours and showed excellent stability.

In the method of this embodiment, since the temperature is constant throughout the entire process, it is possible to avoid the disadvantage that the condition changes greatly with the set value each time the support roller enters each bath. It is also possible to keep the length of the entire device to a minimum. Therefore, it is possible to contribute to the cost reduction of the device, which in turn contributes to the cost reduction of the photovoltaic element.

(Embodiment 3) In this embodiment, a support 20 is made of stainless steel 304 with a thickness of 1 mm and 5 cm square, which is polished to a mirror surface.
1 is different from that of Example 1 in that the photovoltaic device is manufactured by a batch process using a plurality of devices shown in FIG.

The support was held by being sandwiched by clips made of stainless steel. This clip was also used as a current path when the support was used as a cathode.

The washing with water was carried out by using two water tanks of the same size as shown in FIG. 3 for each washing step.

The etching bath used was a mixture of nitric acid and hydrofluoric acid in a ratio of 1: 1 and acid etching was carried out at 25 ° C. for 3 minutes.

The first metal layer forming bath is in 1 liter of water.
In addition, 200g of zinc sulfate and 60g of magnesium sulfate
Solution at 25 ° C. and cathode current density of 20 A
/ Cm ²The first metal layer 202 having an unevenness of 150 nm
Was formed on the support 201.

For the second metal layer forming bath, an aqueous solution of 240 g of copper sulfate and 60 g of sulfuric acid in 1 liter of water was used, and the bath temperature was 25 ° C. and the cathode current density was 2 A / cm ² .
A second metal layer 203 having an unevenness of 50 nm was formed.

As the transparent conductive layer forming bath, an aqueous solution containing 50 g of zinc nitrate hexahydrate and 20 ml of nitric acid in 1 liter of water was used, and the cathode current density was 0.2 A / cm ^{2 at} a liquid temperature of 62 ° C. At the first transparent conductive layer 204 of 500 nm
Was formed.

All of the etching bath, the first metal layer forming bath, the second metal layer forming bath and the transparent conductive layer forming bath were agitated by the bath circulation device shown in FIG. The first transparent conductive layer 204 thus formed showed a wurtzite crystal structure according to RHEED, and exhibited 1 μm crystal grains in the SEM image.

A single p-layer having an i-type layer containing silicon and germanium was formed on the first transparent conductive layer 204 thus formed by the same CVD method as in Example 1.
A semiconductor layer 205 having an in structure was formed. Other points were the same as in Example 1.

The photovoltaic element produced in this example was irradiated with a simulator lamp to examine the photoelectric conversion characteristics.
The measurement conditions were the same as in Example 1.

As a result, as compared with the photovoltaic element when copper and zinc oxide were deposited on stainless steel by a sputtering device,
It was found that the photovoltaic element manufactured in this example had an energy conversion efficiency of 1.17 times. Therefore, it was determined that the photovoltaic element of this example had a large light confinement effect.

Next, the photovoltaic element was changed to 85 ° C.-85% R.
The sample was placed in an H environment test box, a reverse bias of 1 V was applied, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic element when copper and zinc oxide were deposited on stainless steel by a sputtering apparatus approached an unusable shunt level in 5 minutes and became unusable in 40 minutes. On the other hand, the photovoltaic element manufactured in this example was able to maintain a usable shunt level for 11 hours.

In the method of this example, the working time and the liquid temperature can be set freely as compared with the roll process, and the current can be controlled by directly controlling the cathode current. Moreover, since maintenance and inspection of each tank can be carried out individually, a process with a high degree of freedom can be constructed.

[0087]

As described above, according to the present invention,
It is possible to obtain a method for manufacturing a photovoltaic element which is excellent in initial characteristics, long-term environmental stability, and reliability at extremely low cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used for etching a support and depositing a first metal layer, a second metal layer, and a first transparent conductive layer according to the present invention. .

FIG. 2 is a schematic sectional view of a photovoltaic element according to the present invention.

FIG. 3 is a schematic diagram of an apparatus used for precipitation from an aqueous solution according to the present invention.

[Explanation of symbols]

101 feeding roller, 102 winding roller, 103 support roll, 104, 109, 114, 120, 123, 128, 1
34, 137, 142, 148, 152 rollers, 106 etching tank, 107, 112, 113, 121, 126, 127, 1
35, 140, 141, 149, 155 Conveying rollers, 108, 111, 122, 125, 136, 139, 1
50, 154 washing shower, 110, 124, 138, 153 washing bath, 116 first metal forming bath, 117 first metal layer forming bath, 131 second metal layer forming bath, 144 transparent conductive layer forming bath, 145 transparent conductive layer forming bath, 156 drying furnace, 157 warm air nozzle, 158 infrared heater, 201 support, 202 first metal layer, 203 second metal layer, 204 first transparent conductive layer, 205 semiconductor Layer, 206 second transparent conductive layer, 301 acid resistant container, 302 solution, 303 support, 304 counter electrode, 305 power supply, 306 load resistance, 307 solution injection bar, 308 solution suction bar, 309 suction solution pipe, 310 Injection solution pipe, 311 solution circulation pump.

Claims (4)

[Claims] 1. A first metal layer, a second metal layer, a first transparent conductive layer, a semiconductor layer, and a second transparent conductive layer are sequentially laminated on a support containing iron. In the method for manufacturing a photovoltaic element, the first metal layer, the second metal layer, and the first transparent conductive layer are both precipitated from an acidic aqueous solution, Device manufacturing method. 2. The method for manufacturing a photovoltaic element according to claim 1, wherein the support containing iron is etched with an acidic solution. 3. The first metal layer is zinc, and the second metal layer is copper.
A method for manufacturing the photovoltaic element according to 1. 4. The method for manufacturing a photovoltaic element according to claim 1, wherein the first transparent conductive layer is zinc oxide.