JP3017431B2 - Method for manufacturing photovoltaic element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a photovoltaic device. More specifically, non-single-crystal semiconductor materials containing silicon 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 for manufacturing a photovoltaic device comprising an improved light reflection layer.

[0002] The photovoltaic device according to the manufacturing method of the present invention comprises:
For example, it is applied to a solar cell, a sensor, an image pickup device, etc., and further, an application in which the devices are connected in multiple stages as an array to operate stably in an outdoor environment or the like for a long period of time, such as a house or a collective building or system. The present invention is suitably applied to a photovoltaic power generation system or the like used by being connected to a device.

[0003]

2. Description of the Related Art Conventionally, a photovoltaic element made of hydrogenated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated amorphous silicon carbide, microcrystalline silicon or polycrystalline silicon has been used in a long wavelength region. To improve the light collection rate,
A reflective layer on the back has been used. Such a reflective layer desirably exhibits an effective reflection characteristic at a wavelength near the band edge of the semiconductor material where its absorption is reduced, that is, from 800 nm to 1200 nm. As a material that sufficiently satisfies this condition, for example, a metal layer made of gold, silver, copper, or the like can be given. Further, in order to prevent deterioration in characteristics due to a shunt path, a technique of providing a layer made of a light-transmitting material having conductivity between the metal layer and the semiconductor layer, that is, a transparent conductive layer is used. Generally, the metal layer and the transparent conductive layer are
For example, it is formed by a vacuum evaporation method or a sputtering method.
_SC (short-circuit current: the current that photocarriers generated by sunlight are collected and output by the electrodes in the internal electric field when the solar cell is short-circuited and increase when sunlight is used effectively) and improved by 1 mA or more Has been obtained.

[0004] However, the above prior art has the following problems. (1) Although a metal layer and a transparent conductive layer formed by vacuum deposition or sputtering have sufficient electrical and optical characteristics, they have a problem with adhesion, which is easy to peel off. For applications in which a photovoltaic element is installed outdoors for a long period to generate power, long-term reliability remains uneasy.

(2) The amortization cost of the vacuum device is large,
The inefficient use of materials has been a major obstacle to industrial application of solar cells, assuming that the cost of photovoltaic devices using these technologies is extremely high. The government is trying to promote the next generation system because of its non-polluting properties, the power companies and consumers who want to reduce the power generation cost, and the industrial world who wants to build up the installation results and gain a foothold in the next technology. We are eager to lower prices.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a photovoltaic element which can form a metal layer having excellent adhesion and a transparent conductive layer in contact therewith at low cost. 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 inexpensive and is not inferior to conventional methods.

[0008]

According to a method of manufacturing a photovoltaic element of the present invention, a first metal layer, a second metal layer,
In a method for manufacturing a photovoltaic element comprising sequentially laminating a first transparent conductive layer, a semiconductor layer, and a second transparent conductive layer, the support has conductivity and has an uneven shape on the surface. The second metal layer has an uneven shape on the surface, the first transparent conductive layer, crystal grains of the order of the wavelength of light are grown by an electrolytic deposition method using the support as a cathode, The semiconductor layer is formed so as to have irregularities on the wavelength order of the absorption edge of the semiconductor layer different from the irregularities on the surface of the second metal layer. Further, the solar cell module of the present invention is a solar cell module configured by serially connecting sub-modules as photovoltaic elements, wherein the sub-module has a first metal layer and a second metal layer on a support. Layer, a first transparent conductive layer, a semiconductor layer, and a second transparent conductive layer are sequentially laminated, the support has conductivity and has an uneven shape on the surface, and the second metal The layer has an uneven shape on the surface, the first transparent conductive layer,
Crystal grains of the order of the wavelength of light are grown by electrolytic deposition using the support as a cathode, and have irregularities on the wavelength order of the absorption edge of the semiconductor layer different from the irregularities on the surface of the second metal layer. It is characterized by being formed as follows.

In a preferred embodiment of the present invention, a first metal layer, a second metal layer, a first transparent conductive layer, a semiconductor layer, and a second transparent conductive layer are provided on a support containing iron. In the method of manufacturing a photovoltaic element by sequentially laminating, the first metal layer, the second metal layer, and the first transparent conductive layer, both of which are precipitated from an acidic aqueous solution, The expensive thin-film forming apparatus used for producing each layer by a vacuum evaporation method or a sputtering method is unnecessary. Therefore, each layer can be formed at low cost.

In a preferred embodiment 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 the support, each layer is also provided with an uneven shape. Therefore, each layer can confine the reflected light from the back surface, so that the incident light can be further effectively used.

In a preferred embodiment of the present invention, the first metal layer is made of zinc, and the second metal layer is made of copper. And a layer having a high effect of confining reflected light can be realized with long-term reliability.

In a preferred embodiment of the present invention, since the first transparent conductive layer is made of zinc oxide, it has good transparency to near-infrared light effective as reflected light and forms crystal grains of a wavelength order. As a result, the scattering component of the reflected light can be greatly increased, and as a result, J _SC can be increased.

An embodiment 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, reference numeral 201 denotes a support containing iron, 2
02 is the first metal layer, 203 is the second metal layer, 204 is the 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.

(Iron-Containing Support) As the iron-containing support 201 according to the present invention, a plate-like or foil-like support whose surface is etched with hydrofluoric acid / nitric acid is used. .
Further, for continuous processing, it is also possible to form a roll. In order to prevent generation of rust on the end face, stainless steel in which nickel or chromium is introduced may be used. Etching is 1μm
The purpose is to form a degree of unevenness, which is for confining the well-known back surface reflected light.

The support 201 containing iron is determined based on the strength, bendability, rust at the end, etc. of the support.
It may include carbon, silicon, magnesium, chromium, nickel, and the like. In particular, ferrite stainless steel containing nickel and martensitic stainless steel containing nickel and chromium are easy to handle because they do not require rust prevention treatment.
In addition, a cold-rolled steel sheet can be used in terms of cost. In addition, the shape may be a steel plate wound in a roll shape, or a foil, a plate, or the like.

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

For example, a layer can be formed by an apparatus shown in FIG. In the drawing, reference numeral 301 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. 3
Reference numeral 03 denotes a support containing iron used in the present invention, which is used as a cathode.

Reference numeral 304 denotes a counter electrode, in which zinc is used in this case. The counter electrode 304 is an anode. The support 303 serving as a cathode and the counter electrode 304 serving as an anode include:
The power supply 305 is connected to the power supply 305 via a load resistor 306 so that a substantially constant current flows.

Also, in order to stir the solution to reduce unevenness of layer formation and to increase the speed of layer formation for higher efficiency, a suction bar 308 having a plurality of solution inlets, and similarly an injection bar having a plurality of solution outlets. 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 ejection bar 307 and the solution circulation pump 3
11 is used.

The pH of the solution 302 is preferably adjusted to 1.5 to 4.5 in the case of an aqueous solution containing sulfate ions and zinc ions, and is preferably adjusted to 1.5 to 4.5 in the case of an aqueous solution containing chloride ions, zinc ions and ammonia. Preferably, the pH is adjusted to between 4.0 and 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. 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) In the second metal layer 203 according to 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 Like the first metal layer, the layer can be formed by the apparatus shown in FIG. The acid-resistant container 301 holds an aqueous solution 302 containing sulfate ions and copper ions. The counter electrode 304 uses copper. The stirring of the solution is performed by the method described above using a circulation pump. The temperature range of the solution 302 containing sulfate ions and copper ions is preferably 10 to 70 ° C.
Further, the cathode current density is set to 0.05 to 20 A / cm ² .

(First Transparent Conductive Layer) The first transparent conductive layer 204 according to the present invention is obtained by immersing the support on which the second metal layer 203 is formed in an aqueous solution containing zinc ions and nitrate ions. And using the support as a cathode 303 with the apparatus of FIG.
It is formed by depositing zinc oxide. Zinc is used for the counter electrode 304 serving as the 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 set to 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. Furthermore, benzoic acid, formic acid, citric acid, glycolic acid,
Succinic acid, oxalic acid and the like are appropriately used.

(Washing) The etching of the support 201, the formation of the first metal layer 202, the formation of the second metal layer 203, and the formation of the first transparent conductive layer 204 are all processes involving an aqueous solution. And can be continuously performed through a water washing step. In the case where the semiconductor layer 205 is a vacuum process that dislikes water, a drying step is performed after the formation of the first transparent conductive layer 204. Drying is performed by drying by heating with an IR heater in the atmosphere, hot air drying with hot oxygen, vacuum drying, or the like.

The method for manufacturing a photovoltaic device according to the present invention comprises:
It is characterized in that it can be kept acidic in all solution-based processes, thereby minimizing bath deterioration due to carry-in of the solution during washing and transfer of the support to the tank for the next process. be able to. In addition, the water washing path in the middle step can be shortened, which has an extremely great advantage in the configuration 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 heterojunction. Correspondingly, an electromotive force is generated on both sides of the layer. The current generated by the generated electromotive force includes a second transparent conductive layer 206 formed on the upper side, a first transparent conductive layer 204 formed on the lower side, a first metal layer 202, and a second metal layer 203. Flows through a current path composed of the support 201 via the support and a load connected thereto. The second transparent conductive layer 206 formed on the upper side also serves as an anti-reflection layer, and thus has a limited thickness and may not have sufficient current capability. In this case, a grid electrode is further provided. .

The semiconductor layer 205 includes an LF discharge, an RF discharge,
Pn junction, pin using amorphous or crystalline silicon, amorphous or crystalline silicon / germanium, amorphous or crystalline silicon carbide, etc. by a CVD method in which a gas is excited by VHF discharge or microwave discharge. In addition to those having a junction, a Schottky junction, and a hetero junction, those having a structure called a tandem or triple in which these are stacked can be used.

The second transparent conductive layer 206 is formed by vacuum evaporation,
ITO, In ₂ O ₃ , SnO ₂ , ZnO, TiO _2, etc., formed by sputtering, reactive sputtering, or CVD can be used. Of course, they may be used in a laminated state.

Light incident from above the photovoltaic element is in an anti-reflection state at the central wavelength, which is the second transparent conductive layer 206, enters the semiconductor layer 205, 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 via the first transparent conductive layer 204, the second metal layer 203 and the first metal layer 202 to the support 201 side. Light not absorbed by the semiconductor layer 205 is
The light is reflected by the second metal layer 203 via the first transparent conductive layer 204, and returns to the semiconductor layer 205 via the first transparent conductive layer 204 again. Therefore, the second metal layer 203
Is very important.

Further, light having a wavelength much longer than the band edge of the semiconductor layer 205 is hardly further absorbed by the semiconductor layer 205 even when reflected and returned to the semiconductor layer 205. The reflectivity of the semiconductor layer 205
It is necessary to be excellent near the absorption edge.

If the second metal layer 203 has irregularities or the first transparent conductive layer 204 has irregularities, the reflection on the second metal layer 203 or the first transparent conductive layer 204 Due to the refraction of light, the reflected light is inclined and a large optical path is taken, so that the amount of light absorbed by the semiconductor layer 205 can be increased by an effect generally called light confinement, and as a result, the photocurrent increases. This unevenness is preferably on the order of the wavelength at the absorption edge of the semiconductor layer 205.

The unevenness according to the present invention is obtained by first forming the first unevenness when etching the support 201 and then forming the first unevenness when forming the first metal layer 202 and / or the second metal layer 203. The unevenness is formed when the transparent conductive film is formed. Irregularities formed at the interface between the second metal layer 203 and the first transparent conductive layer 204;
The unevenness formed by the first transparent conductive layer 204 and the semiconductor layer 205 has a different shape than a shape following the shape, and gives a preferable result in increasing the current of the photovoltaic element.

As described above, the photovoltaic element is desired to operate stably for a long time in an outdoor environment. For this purpose, sufficient durability against mechanical bending is required depending on the temperature, humidity, and installation conditions. The change in temperature can range from the fate of the photovoltaic element being exposed to sunlight, to high temperatures approaching 100 ° C. during the daytime in summer, to −30 at dawn in winter.
It has to cope with the environment below ℃. Furthermore, there is a temperature change of several tens of degrees Celsius even during one day,
Because 02 to 206 have different coefficients of thermal expansion, peeling off at the interface often occurs. In particular, as the film thickness increases, this obstacle becomes remarkable.

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

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

As a specific method according to the present invention, the surface of the support 201 containing iron is etched and removed with an aqueous solution containing hydrofluoric acid and nitric acid, and at the same time, the surface is made uneven. Further, the first metal layer 202 and / or the second metal layer 203 deposited thereon are formed with irregularities. Further, in the first transparent conductive layer 204 deposited thereon, crystal grains on the order of the wavelength of light grow, and the crystal grains are filled with different phases. Does not span layers. This is an important point when the support is bent by the application of a physical force, and when the support is flexible and a photovoltaic element with high flexibility is manufactured, Works particularly well. In addition, the 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 hundred degrees Celsius to obtain the necessary unevenness, and a large thermal shock is originally applied. Not something.

According to the experiments by the present inventors, when the temperature cycle is repeated in a humid environment, cracks enter the first transparent conductive layer 204, and the cracks serve as a water ingress path, and the photovoltaic element In a module configured by connecting several sub-modules in series, a reverse voltage is applied to the photovoltaic element in a state called a partial shade in which only a part is shadowed, and the second metal layer 203 It has been found 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 formed densely and hardly over the entire layer, and is particularly remarkable when formed by a vacuum high-temperature process such as sputtering. The shunt of the element based on such tree growth is
After that, even if the environmental humidity decreases and the moisture disappears, it does not recover. First transparent conductive layer 204 based on the method of the present invention
Is originally grown from an aqueous solution, so the relaxation of water works, and the above-mentioned problem can be minimized.

[0040]

EXAMPLES Hereinafter, the method for manufacturing a photovoltaic device according to the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 In this example, a first metal layer, a second metal layer, and a first transparent conductive layer were formed using the manufacturing apparatus shown in FIG. A method for manufacturing a photovoltaic device having the above-described layer configuration will be described.

FIG. 1 shows that a support is etched with an acidic solution, and a first metal layer, a second metal layer, and a first transparent conductive layer are further deposited on the support from an acidic aqueous solution. FIG. 1 is a schematic view of an apparatus used for performing the above. As the support, a thin plate of stainless steel 430BA formed in a roll shape was used.

In FIG. 1, reference numeral 101 denotes a feed roller, which feeds out a support roll 103 and finally winds it up on a take-up roller 102. Delivery roller 1
01 and the take-up roller 102, the etching tank 10
6. Rinse tub 110, first metal layer forming bath 117, rinsing tank 124, second metal layer forming bath 131, rinsing tank 13
8. A bath 145 for forming a transparent conductive layer, a washing bath 153, and a drying furnace 156 were sequentially provided. Rollers 104, 10 for controlling the transport path of the support roll are provided in each tank.
9, 114, 120, 123, 128, 134, 13
7, 142, 148, and 152 were 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.

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

(2) Support roll 1 after step (1)
03 was transported to the washing tank 110 via the transport roller 107. Washing was sufficiently performed using the washing showers 108 and 111. At this time, the amount of water is preferably 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 the etched support 10
A first metal layer was formed on 3. The first metal layer forming bath 116 is a mixture of 300 g of zinc sulfate and 30 g of ammonium sulfate in one liter of water.
The temperature was controlled at 0 to 60 ° C. The pH of the solution was in the range of 3.0 to 4.0.

A zinc plate was used for the anode. In this apparatus, since the support roll 103 is set to the ground potential, the current is read from the anode zinc plate to control the layer formation. In this example, the current density was 30 A / cm ² . The layer formation speed is 5n
m / s, and the thickness of the first metal layer 202 formed in the first metal forming bath was 200 nm. Thereafter, the sheet is conveyed to a washing tank 124 via a conveying roller 121. Washing was sufficiently performed in the washing showers 122 and 125.

(4) Support roll 1 after step (3)
03 was transported to the second metal layer forming bath 131 via the transport rollers 126 and 127, and the second metal layer was formed on the first metal layer. Second metal forming bathtub 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 for the anode. The current density of this anode is 3A
/ Cm ² . Thus, a 300 nm-thick second metal layer was obtained.

(5) Support roll 1 after step (4)
03 was washed in a washing tank 138. Thereafter, 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 contains 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 solution was set to 5.2 to 5.8. As the counter electrode, zinc whose surface was buffed was used. The current density applied to the counter electrode was 2 A / cm ² . The layer formation speed was 18 nm / s, and the 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 in the washing tank 153. After that, the support roll 103 passes through the conveying roller 155 and the drying furnace 15.
Sent to 6. The drying furnace 156 includes a hot air nozzle 157 and an infrared heater 158.
Then we did water refreshment at the same time. The temperature of the hot air at the hot air nozzle 157 was 150 ° C. In addition, infrared heater 15
The temperature of 8 was 200 ° C.

(7) The support roll 103, which has been subjected to the drying step of the step (6), is provided on the iron-containing support 201 on the first metal layer 202, the second metal layer 203, and the first transparent conductive layer. Roller 1
02.

The first metal layer forming bath 117 and the second metal layer forming bath 131 were agitated with air, and the transparent conductive layer forming bath 145 was mechanically stirred. In all three tanks, the pH of the bath was constantly monitored by a pH meter having a built-in temperature correction using a glass electrode. The first metal layer forming bath 117 contains zinc sulfate, the second metal forming bath 131 contains copper sulfate and ammonia, and the transparent conductive layer forming bath 14
In 5, the pH in the bath was controlled by adding nitric acid.

(8) On the substrate formed by the steps (1) to (7), that is, on the support 201, the first metal layer 2
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 on which the semiconductor layers 04 were sequentially stacked by a roll-compatible CVD apparatus.

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

(10) The same as (9) 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) 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 the steps (8) to (11). As a deposition apparatus, a sputtering apparatus corresponding to a roll was used. (13) Perform electrode extraction processing using silver paste,
The fabrication of the photovoltaic element has been completed.

The photovoltaic elements produced in the above steps (1) to (13) were irradiated with a simulator lamp to examine the photoelectric conversion characteristics.

As a result, compared to a photovoltaic element in which copper and zinc oxide were deposited on stainless steel by a sputtering apparatus,
The photovoltaic element manufactured in this example was found to have 1.12 times the energy conversion efficiency.

Next, the photovoltaic element was set at 85 ° C.-85% R
H, placed in an environmental test box, and applied with a reverse bias of 1 V, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic element in the case where copper and zinc oxide were deposited on stainless steel by a sputtering device approached an unusable shunt level in 10 minutes, and could not withstand use in 1 hour. In contrast, the photovoltaic element manufactured in this example was able to maintain a usable shunt level for 15 hours.

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

In this embodiment, the transparent conductive layer forming bath 14 is used.
As 4, 30 g of zinc nitrate hexahydrate in 1 liter of water,
An aqueous solution containing 10 ml of nitric acid was selected, but zinc nitrate hexahydrate was 1 g to 80 g, and no nitric acid was added 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 forming speed. If the layer is formed slowly at a high temperature, a relatively flat layer with good crystal orientation and good adhesion is obtained. When a layer is formed at a high temperature at a low temperature, a layer having large irregularities is formed. These should be selected according to the wavelength of light for which a light confinement effect required for the semiconductor layer 205 is expected.

Further, in this embodiment, an example of a triple structure having a pin structure is shown as the semiconductor layer 205. However, 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 method for manufacturing a photovoltaic element described above can be applied include, for example,
Examples include ZnS, ZnSe, crystalline silicon, and CuInSe.

(Embodiment 2) This embodiment is different from the embodiment in that the temperature of each washing and each bath is set to approximately 50 ° C. in all steps.

However, the etching bath was composed of nitric acid 3, hydrofluoric acid 2, vinegar.
Acid 3 is mixed, the first metal layer forming bath and the second
The metal layer forming bath of Example 1 is the same as that of Example 1, and the transparent conductive layer
The forming bath 139 contains zinc nitrate hexahydrate 3 in 1 liter of water.
0 g, nitric acid 10 ml, acetic acid 5 ml
Was. The current density was 2 A / c in the metal layer forming bath.
m ^Two0.4 A / cm in a transparent conductive layer forming bath 139^Twoage
Was. At this time, the layer forming speed 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
The formation rate is 5 nm / s, the layer thickness is 200 nm, and the first transparent
The layer forming speed of the conductive layer 204 is 1 nm / s, and the layer thickness is 1200.
nm.

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

The photovoltaic device 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, compared to a photovoltaic element in which copper and zinc oxide were deposited on stainless steel by a sputtering apparatus,
The photovoltaic element manufactured in this example was found to have an energy conversion efficiency of 1.07 times.

Next, the photovoltaic element was set at 85 ° C.-85% R
H, placed in an environmental test box, and applied with a reverse bias of 1 V, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic device manufactured in this example was able to maintain a usable shunt level for 17 hours and exhibited excellent stability.

In the method of this embodiment, since the temperature is constant over the entire process, it is possible to avoid the inconvenience that the condition is largely changed from the set value every time the support roller enters each bath. In addition, it is possible to minimize the length of the entire apparatus. Therefore, it is possible to contribute to the cost reduction of the device, and further to the cost reduction of the photovoltaic element.

Example 3 In this example, a mirror-polished stainless steel 304 having a thickness of 1 mm and a square of 5 cm was used as the support 20.
Example 1 is different from Example 1 in that a photovoltaic element was manufactured in a batch process using a plurality of apparatuses shown in FIG.

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

The rinsing was performed using two water tanks having the same size as that shown in FIG. 3 for each rinsing step.

The etching bath used was a mixture of nitric acid and hydrofluoric acid at a ratio of 1: 1 and was subjected to acidic etching at 25 ° C. for 3 minutes.

[0077] The first metal layer forming bath is
From zinc sulfate 200g and magnesium sulfate 60g
At a liquid temperature of 25 ° C. and a cathode current density of 20 A
/ Cm ^Two150 nm uneven first metal layer 202
Was formed on the support 201.

The second metal layer forming bath uses an aqueous solution consisting of 240 g of copper sulfate and 60 g of sulfuric acid in 1 liter of water at a liquid temperature of 25 ° C. and a cathode current density of 2 A / cm ² .
A 50-nm uneven second metal layer 203 was formed.

The bath for forming the transparent conductive layer was an aqueous solution containing 50 g of zinc nitrate hexahydrate and 20 ml of nitric acid in 1 liter of water, and the liquid temperature was 62 ° C., and the cathode current density was 0.2 A / cm ^2. 500 nm first transparent conductive layer 204
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 subjected to bath liquid stirring by the bath circulation device shown in FIG. The first transparent conductive layer 204 thus formed exhibited a wurtzite crystal structure according to RHEED, and exhibited crystal grains of 1 μm in the SEM image.

A single p-type layer having an i-type layer containing silicon and germanium is formed on the first transparent conductive layer 204 thus formed by the same CVD method as in the first embodiment.
A semiconductor layer 205 having an in structure was formed. 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, compared to a photovoltaic element in which copper and zinc oxide were deposited on stainless steel by a sputtering apparatus,
The photovoltaic element manufactured in this example was found to have 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 set at 85 ° C.-85% R
H, placed in an environmental test box, and applied with a reverse bias of 1 V, and the photoelectric conversion characteristics were monitored over time.

As a result, the photovoltaic element in the case where copper and zinc oxide were deposited on stainless steel by a sputtering device approached an unusable shunt level in 5 minutes, and could not withstand use in 40 minutes. In contrast, the photovoltaic device manufactured in this example was able to maintain a usable shunt level for 11 hours.

In the method of this embodiment, the working time and the liquid temperature are freer than in the roll process, and the current can be controlled by directly controlling the cathode current. In addition, since maintenance and inspection of each tank can be performed individually, a process with a high degree of freedom can be constructed.

[0087]

As described above, according to the present invention,
A method for manufacturing a photovoltaic device having excellent initial characteristics and long-term environmental stability and reliability can be obtained at extremely low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view 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 device according to the present invention.

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

[Explanation of symbols]

101 delivery roller, 102 take-up roller, 103 support roll, 104, 109, 114, 120, 123, 128, 1
34, 137, 142, 148, 152 roller, 106 etching tank, 107, 112, 113, 121, 126, 127, 1
35, 140, 141, 149, 155 Transport rollers, 108, 111, 122, 125, 136, 139, 1
50, 154 washing shower, 110, 124, 138, 153 washing tank, 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 hot 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.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-196734 (JP, A) JP-A-6-204519 (JP, A) JP-A-5-218469 (JP, A) JP-A-5-218469 106089 (JP, A) JP-A-2-47292 (JP, A) JP-A-2-47293 (JP, A) JP-A-4-99882 (JP, A) Ito, Omi, "Prepared by aqueous electrolysis ZnO film, "Proceedings of the 42nd Joint Lecture on Applied Physics, March 1995, No. 2, p447 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 31/04 C25D 9/04

Claims (11)

(57) [Claims] 1. A photovoltaic device in which 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. in the method of manufacturing, the irregularities on the surface together with the support to have a conductivity
A, the second metal layer has an irregular shape on a surface, said first transparent conductive layer, the crystal grains of growth of the wavelength order of light by electrolytic deposition to a cathode of said support
And forming the semiconductor layer so as to have irregularities on the wavelength order of the absorption edge of the semiconductor layer different from the irregularities on the surface of the second metal layer . 2. The method according to claim 1, wherein the first transparent conductive layer mainly includes zinc oxide. 3. The method according to claim 2, wherein the first transparent conductive layer is formed using an aqueous solution containing nitrate ions and zinc ions. 4. The aqueous solution containing nitrate ions and zinc ions is prepared by mixing zinc nitrate hexahydrate 1 to 8 with respect to 1 liter of water.
The method according to claim 3, wherein the concentration is adjusted to 0 g. 5. The method according to claim 3, wherein the pH of the aqueous solution containing nitrate ions and zinc ions is adjusted to 4.0 to 6.3. . 6. The method according to claim 1, wherein a cathode current density at the time of forming said first transparent conductive layer is adjusted to 0.002 to 10 A / cm ^2. 13. The method for producing a photovoltaic device according to item 10. 7. The method according to claim 1, wherein the support is etched with an acidic solution. 8. The method according to claim 1, wherein the support is a long support housed in a roll shape. 9. A series of sub-modules which are photovoltaic elements
A solar cell module configured by connection, The sub-module comprises a first metal layer on a support, a second metal layer.
A metal layer, a first transparent conductive layer, a semiconductor layer, and a second transparent layer.
Bright conductive layers are sequentially laminated, The support has conductivity and has an uneven shape on the surface.
Have The second metal layer has an uneven shape on the surface, The first transparent conductive layer includes an electrode having the support as a cathode.
Crystal grains of the order of the wavelength of light are grown by the analytical method.
The half of the surface of the second metal layer is different from the unevenness of the surface of the second metal layer.
Make sure that the absorption edge of the conductor layer has irregularities on the order of the wavelength
Solar cell module characterized by being formed in 10. The first transparent conductive layer is made of zinc oxide.
Is a main component.
Solar cell module. 11. The method according to claim 11, wherein the first transparent conductive layer comprises
Formed using an aqueous solution containing zinc and zinc ions
The solar cell module according to claim 10, wherein
Le.