JP3097805B2 - Solar cell, method of manufacturing the same, and plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film solar cell having CuInSe ₂ as an absorbing layer, a method of manufacturing the same, and a plating method used for manufacturing a thin-film solar cell.

[0002]

2. Description of the Related Art Recently, compound semiconductors comprising elements of groups 1B-3B-6B of the periodic table have attracted attention as thin-film solar cells having excellent photoelectric conversion efficiency and large area can be manufactured at low cost. In particular, CuInSe ₂ is
(1) The absorption coefficient α is as high as about 10 ⁵ / cm, and it is possible to sufficiently absorb sunlight even with a thin film of about 2 μm. (2) The band gap is 1.1 eV, which is suitable for photoelectric conversion of sunlight. (3) It has received the most attention because it has features such as light degradation significantly smaller than that of amorphous silicon. To manufacture a large-area thin-film solar cell at low cost, Japanese Patent Application Laid-Open No. Hei 5-506334 (International Publication W
O92 / 05586) publication,
A method for manufacturing a solar cell using a dispersion plating method has been proposed.

FIG. 9 is a cross-sectional view illustrating a first example of a conventional method of manufacturing a thin-film solar cell in the order of steps for explaining the method.

[0004] First, a plating solution prepared at a ratio shown in Table 1 below is prepared and put into a plating tank. Since the Se powder has poor affinity for water, a surfactant may be added.

[0005]

[Table 1]

Next, as shown in FIG. 9A, a substrate on which a Mo film 2 is formed on a glass substrate 1 by a method such as vapor deposition or sputtering is prepared. The substrate is immersed in trichloroethylene, ethanol, and an alkaline degreasing solution in order to wash well, then thoroughly washed with pure water, and dried.
In this cleaning, an ultrasonic cleaner is used.

[0007] Next, as shown in FIG.
Electrodeposited at a current density of 3 A / dm ^{2 using}
The u-In / Se dispersed plating layer 3 is formed. Since Se powder precipitates during this plating, plating is performed while stirring the plating solution.

Next, as shown in FIG.
And H_TwoAr + H mixed with Se gas _TwoIn Se gas atmosphere
Or an Ar + Se gas atmosphere in which Ar gas and Se vapor are mixed.
CuInSe by heat treatment in atmosphere_TwoConvert to alloy layer 4
You. As shown in FIG. 10, the heat treatment is performed from room temperature to 30 ° C. /
At a rate of 200 minutes to 200 ° C to 250 ° C.
Hold for 0-60 minutes, then at 400C at a rate of 30C / min.
Raise to 450 ° C and hold at this temperature for about 2-4 hours, then
It is performed under the condition of cooling to room temperature. 200 ° C to 250 ° C
Is the temperature at which alloying starts, and 400 ° C to 450 ° C is C
uInSe_TwoIt is said that the temperature at which the crystal grows.

FIG. 11 is a cross-sectional view illustrating a second example of a conventional method of manufacturing a thin-film solar cell in the order of steps for explaining the second example.

As shown in FIG. 11A, a substrate is prepared in which a Cr film 5 is formed on a glass substrate 1 made of soda lime glass, and a Mo film 2 is formed thereon. The Cr film 5 is provided to prevent peeling due to a difference in thermal expansion coefficient between Mo and the glass substrate. Soda lime glass, M
The thermal expansion coefficients of o and Cr are as shown in Table 2. That is, Cr has almost the same coefficient of thermal expansion as soda lime glass, is well compatible with soda lime glass, and hardly peels off. Although the thermal expansion coefficients of Cr and Mo are far apart, both have the flexibility to absorb the stress caused by the difference in the thermal expansion coefficient, and the bonding between the metals is strong, so there is almost no peeling between the two. . For this reason C
r is sandwiched between Mo and glass. This substrate is
Wash well with the same method as in the example.

[0011]

[Table 2]

Next, as shown in FIG. 11B, a Cu—In / Se dispersed plating layer 3 is formed by performing electrodeposition at a current density of 3 A / dm ² using the Mo film 2 as a cathode. The stirring of the plating solution during the plating is the same as in the first example.

Next, as in the first example, heat treatment is performed in an atmosphere containing Se gas to form a CuInSe ₂ alloy layer 4 as shown in FIG.

[0014]

In the above two examples, when the heat treatment for alloying CuInSe ₂ is performed, the Mo film 2
Peeling may occur between the Cu film and the CuInSe ₂ alloy layer 4 or between the Mo film 2 and the glass substrate 1. Mo
The peeling between the film 2 and the glass substrate 1 can be greatly reduced by providing the Cr layer 5, but the Mo film 2 and the CuInS
there is a problem that the medium s difficult to reduce the peeling between e ₂ alloy layer 4.

Although there are various causes of the peeling, the Mo film 2 and the Se particles in the Cu—In / Se dispersed plating layer 3 come into contact with each other and react with Mo and Se to form a Mo—Se compound. There is a pinhole in the Mo film 2, and moisture or gas existing in the pinhole is vaporized or thermally expanded by heat treatment to push out the CuInSe ₂ alloy layer 4 on the pinhole and try to go outside. It is considered that the main cause is that Se evaporates due to heat during the heat treatment, enters into the pinhole, and reacts with Mo and Cr underneath.

More specifically, as shown in FIG. 12A, a Cu film is
-Assume that the In / Se dispersed plating layer 3 is applied.
Se particles 41 are contained in the Cu—In / Se dispersed plating layer 3.
Are dispersed, and some of the Se particles 41 are in contact with the Mo film 2. When heat treatment is performed in this state, FIG.
As shown in (b), a Mo-Se compound 43 is generated,
Since the generated compound has a volume, the CuInSe ₂ alloy layer 4 thereon is pushed up and peeled off. In addition, pinhole 4
2 is vaporized or thermally expanded by the heat treatment to push out the CuInSe ₂ alloy layer 4 on the pinhole 42 and try to go outside.
_{2 The} alloy layer 4 peels off. Further, as shown in FIG. 12C, Se is vaporized by the heat during the heat treatment, enters the pinhole 42, and reacts with Mo and Cr under the Mo.
For example, a Cr—Se compound 44 is generated, and CuInSe ₂
When the alloy layer 4 is pushed up, the CuInSe ₂ alloy layer 4 is peeled off. Peeling does not occur very much, but even if it is a small amount, as long as peeling occurs, all products must be inspected and peeling defective products must be removed,
Inspection and sorting require man-hours, and the product yield is reduced, so that there is a problem that the cost of the solar cell is increased.

An object of the present invention is to provide a CuInS
An object of the present invention is to provide a solar cell having a structure in which an e ₂ alloy layer does not peel off and a method for manufacturing the same.

An object of the present invention is to provide a plating method which can reduce the equipment cost and equipment installation area of a plating apparatus and can be used efficiently in the manufacture of solar cells.

[0019]

[0020]

[0021]

[0022]

[0023]

SUMMARY OF THE INVENTION The present invention comprises a step of immersing a substrate having a molybdenum conductive film on a surface thereof in a plating solution obtained by adding selenium particles to a solution in which copper ions and indium ions are dissolved; In a state where is precipitated, a step of forming a copper layer on the molybdenum conductive film by applying a potential at which only copper is deposited on the molybdenum conductive film, and the selenium particles are stirred by stirring the plating solution. In a state of being dispersed in the plating solution, a step of applying a potential at which copper and indium are deposited on the molybdenum conductive film to form a copper-indium-selenium plating layer on the copper layer, and heat-treating at least the copper -Converting the indium-selenium plating layer to a copper-indium-selenium alloy layer.

The present invention comprises a step of immersing a substrate having a molybdenum conductive film on its surface in a plating solution obtained by adding selenium particles to a solution in which copper ions and indium ions are dissolved;
In the state where the selenium particles are precipitated, a step of applying a potential at which copper and indium are deposited on the molybdenum conductive film to form a copper-indium alloy layer on the molybdenum conductive film, and stirring the plating solution. Then, in a state where the selenium particles are dispersed in the plating solution, a potential at which copper and indium are deposited on the molybdenum conductive film is applied to form a copper-indium-selenium plating layer on the copper-indium alloy layer. And a step of converting at least the copper-indium-selenium plating layer into a copper-indium-selenium alloy layer by heat treatment.

The present invention comprises a step of immersing a substrate having a conductive film on a surface thereof in a plating solution containing at least copper ions and indium ions, and a step of applying a potential at which only copper is deposited to the conductive film. Forming a plating layer containing at least copper-indium on the copper layer by applying a potential at which copper and indium are deposited to the conductive film. And

[0026]

The conductive intermediate layer prevents the molybdenum conductive film from directly contacting selenium, prevents the reaction between molybdenum and selenium, and prevents the copper-indium-selenium alloy layer from peeling off. Have.

A copper layer is selected as the conductive intermediate layer. This is because copper is difficult to form an alloy with molybdenum and is a constituent element of the copper-indium-selenium alloy layer, and thus strongly adheres to the copper-indium-selenium alloy layer.

An indium layer is selected as the conductive intermediate layer. Indium is difficult to form an alloy with molybdenum,
Since it is a constituent element of the indium-selenium alloy layer, copper-
This is because it firmly adheres to the indium-selenium alloy layer.

A copper-indium alloy layer is selected as the conductive intermediate layer. This is because the copper-indium alloy hardly forms an alloy with molybdenum and is a constituent element of the copper-indium-selenium alloy layer, so that it is firmly bonded to the copper-indium-selenium alloy layer.

Since the copper ion and the indium ion have different reduction potentials, only the copper layer can be formed on the molybdenum conductive film by applying a potential at which only copper is deposited, and then the plating solution is stirred. By doing so, the precipitated selenium particles are lifted up, and a copper-indium-selenium plating layer can be formed on the copper layer by applying a potential at which copper and indium are deposited. If selenium particles are suspended and dispersed in the plating solution during plating to form a copper layer, selenium particles also precipitate together with copper, so that the selenium particles are allowed to settle at the bottom of the plating tank without stirring during copper plating. . As described above, if the copper layer and the copper-indium-selenium plating layer can be formed with one plating tank and one kind of plating solution, the equipment cost of the plating apparatus is reduced, the equipment installation area is not increased, and the man-hour is reduced. Can be reduced,
Moreover, since the copper-indium-selenium alloy layer does not peel off, the solar cell can be manufactured at low cost.

By making use of the fact that selenium particles are settled at the bottom of the plating tank and plating is performed using a supernatant to obtain a plating layer containing no selenium particles, a copper-indium alloy layer is formed on the molybdenum conductive film. Then, the selenium particles that have precipitated are lifted by stirring the plating solution, and a copper-indium-selenium is deposited on the copper-indium alloy layer by applying a potential at which copper and indium are deposited. A plating layer can be formed. In this way, a copper-indium alloy layer and a copper-indium-selenium plating layer can be formed with one plating tank and one kind of plating solution, and equipment costs, equipment installation area, man-hours can be reduced, and copper-indium- Since the selenium alloy layer does not peel off, a solar cell can be manufactured at low cost.

The above manufacturing method is based on a plating method utilizing the fact that copper ions and indium ions have different reduction potentials. This plating method can be applied to a plating solution containing at least copper ions and indium ions and not containing selenium. When this plating method is used, similarly to the above, the equipment cost and equipment installation area of the plating apparatus can be reduced, and the number of steps can be reduced, so that plating can be performed at low cost.

[0033]

【Example】

(Example 1) First, a Cu base plating solution is prepared at the following ratio. Copper sulfate 160 g / l (1.0 M) Sulfuric acid 49 g / l (0.5 M) Next, a Cu—In / Se dispersed plating solution having the composition shown in Table 1 is prepared.

Two plating tanks were prepared, and the above plating solutions were put into separate plating tanks, and a Cu base plating bath and a Cu-
In / Se dispersion plating bath.

FIG. 1 is a sectional view showing a method of manufacturing a solar cell according to a first embodiment of the present invention in order of steps.

First, as shown in FIG. 1A, a glass substrate 1 having a Cr film 5 and a Mo film 2 formed thereon is prepared. This was put into a Cu base plating bath, and the current density was 3 A / d
m ² for 1 minute, and a thickness of about 0.1 mm on the Mo film 2.
A 2 μm Cu layer 6 was formed.

Next, as shown in FIG.
Put in u-In / Se dispersion plating bath, current density 3A / d
plating for 5 minutes at m ² , and 1.5 μm thick Cu-I
The n / Se dispersed plating layer 3 was formed. When this dispersed plating layer 3 was analyzed, it was Cu: In: Se = 30: 35: 35 in atomic%.

Next, as shown in FIG. 1C, the CuInSe ₂ film 4 was formed by heat treatment in an Ar + Se gas atmosphere in which Ar gas and Se vapor were mixed. Heat treatment is shown in FIG.
As shown in the figure, the temperature is raised from room temperature to 250 ° C. at a rate of 30 ° C./min and held at this temperature for about 30 minutes, then raised to 450 ° C. at a rate of 30 ° C./min and held at this temperature for about 2 hours And then cooled to room temperature. When this CuInSe ₂ film 4 was analyzed, it was Cu: In: Se = 25.3: 24.4: 50.3 in atomic%. The CuInSe ₂ film 4 was visually inspected, but no peeling of the film was observed.

As described above, the Mo film 2 and the Cu-In / Se
When the Cu layer 6 is provided between the dispersed plating layer 3 and Mo, S
e does not come into direct contact with the Mo-Se compound, as shown in FIG.
e evaporates into the pinholes of the Mo film 2 and reacts with Mo and Cr under the Mo to form a Cr—Se compound,
CuInSe ₂ alloy layer 4 pushed, it is possible to prevent occurrence of defects such as that CuInSe ₂ alloy layer 4 is peeled off, thus to improve the yield, the cost can be reduced.

(Example 2) First, an In base plating solution is prepared at the following ratio. Put this plating solution in the plating tank,
In plating bath. The indium sulfate 300 g / l (0.6 M) Cu-In / Se dispersion plating solution is the same as the plating solution used in Example 1.

FIG. 2 is a sectional view illustrating a method of manufacturing a solar cell according to a second embodiment of the present invention in the order of steps.

First, as shown in FIG. 2A, a glass substrate 1 having a Cr film 5 and a Mo film 2 formed thereon is prepared. This was put into an In base plating bath, and the current density was 3 A / d.
Plating was performed at m ² for 1 minute, and an In layer 7 having a thickness of about 0.2 μm was formed on the Mo film 2.

Next, Cu-In / S
e, and placed in a dispersion plating bath, plating was performed at a current density of 3 A / dm ² for 5 minutes, and as shown in FIG.
The Se dispersion plating layer 3 was formed. The thickness and composition of the Cu—In / Se dispersed plating layer 3 are the same as in Example 1.

Next, similarly to the first embodiment, a heat treatment is performed in an Ar + Se gas atmosphere, and as shown in FIG.
The film was converted to an InSe ₂ film 4.

In the second embodiment, the Mo film 2 and the Cu-I
Since the n / Se dispersed plating layer 3 is separated from the n / Se dispersed plating layer 3 by the In layer 7, Mo and Se do not come into direct contact with each other.
Mo-Se compound or Cr-Se as shown in
No compound is generated, and defects such as peeling of the CuInSe ₂ alloy layer 4 can be prevented. Therefore, the yield can be improved and the cost can be reduced.

(Example 3) First, a Cu-In base plating solution is prepared at a ratio shown in Table 3. This plating solution is put into a plating bath to form a Cu-In base plating bath. Cu-In
The / Se dispersion plating solution is the same as the plating solution used in Example 1 (see Table 1).

[0047]

[Table 3]

FIG. 3 is a sectional view showing a method of manufacturing a solar cell according to a third embodiment of the present invention in the order of steps.

First, as shown in FIG. 3A, a glass substrate 1 having a Cr film 5 and a Mo film 2 formed thereon is prepared. This was put into a Cu-In base plating bath, and a current density of 6
A / dm ² plating for 1 minute, 0.5μm thick C
The u-In alloy layer 8 was obtained. When this Cu—In alloy layer 8 was analyzed, it was Cu: In = 60: 40 in atomic%.

Next, as in the first embodiment, Cu-In / S
e, and placed in a dispersion plating bath, plating was performed at a current density of 3 A / dm ² for 5 minutes, and as shown in FIG.
The Se dispersion plating layer 3 was formed. The thickness and composition of the Cu—In / Se dispersed plating layer 3 are the same as in Example 1.

Next, as in the first embodiment, a heat treatment is performed in an Ar + Se gas atmosphere, and as shown in FIG.
The film was converted to an InSe ₂ film 4.

In the third embodiment, the Mo film 2 and the Cu-I
Since the n / Se dispersed plating layer 3 is separated from the n-Se dispersed plating layer 3 by the Cu-In alloy layer 8, Mo and Se do not come into direct contact with each other, and the Mo-Se compound or the Cr-Se as shown in FIG. No compound is formed and CuI
It is possible to prevent the occurrence of defects such as the nSe ₂ alloy layer 4 being peeled off, thereby improving the yield and reducing the cost.

In each of the three embodiments described above, the underlying plating bath and the Cu-In / Se dispersed plating bath were separately used. Separating the plating baths doubles the equipment cost and the installation area of the plating bath, and takes a lot of man-hours to transfer and clean the object to be plated, thus increasing the cost. Undercoating and C in continuous operation with one plating tank and one kind of plating solution
If u-In / Se dispersion plating can be performed, equipment costs and installation area can be halved, man-hours can be reduced, and costs can be reduced. The present invention has solved this problem,
This will be described below.

FIG. 4 is a side view of a plating bath used for plating of the present invention.

The plating tank 11 is formed in a rectangular parallelepiped, and is open at the top. The plating solution 12 is put into this tank, and the plate 13 as a working electrode, the counter electrode 14 and the reference electrode RE are immersed in the solution, and the plate 13, the counter electrode 14 and the reference electrode RE are placed in a potentiostat. 15, a negative potential is applied to the plate 13, a positive potential is applied to the counter electrode 14, and the reference electrode R
A reference potential is applied to E. The reference potential is a potential for keeping the potential of the working electrode (plated object 13) constant at a target potential, and is usually a reference SSE (Saturated) as a reference.
Sulfate Electrode (mercuric sulfate electrode) or NHE (Normal Hydrogen)
Electrode, a standard hydrogen electrode). Here, since the plating solution is strongly acidic,
SE is used as the reference potential. The reference electrode RE is also used for changing the working electrode (plated object 13) to a target potential. The working electrode (plated object 13) is changed to a target potential by adding or subtracting a certain voltage with reference to the potential of the reference electrode RE. Further, the potentiostat 15 is also used to keep the potential between the working electrode (plated object 13) and the reference electrode RE constant.

In plating, the reduction potential is important. The reduction reaction and reduction potential of Cu and In are as shown in Formula 1. In Equation 1, the reduction potential V is SSE (Sat
urated Sulfate Electrode)
, The potential is shown with respect to this.

[0057]

(Equation 1)

FIG. 5 shows Cu and Cu-In due to the reduction potential difference.
And FIG. 6 is a diagram for explaining the relationship between the set potential of the object to be plated and the amounts of Cu and Cu-In deposited.

A plating solution having the same composition as that of the Cu-In base plating solution used in Example 3 was put into the plating tank 11 and Cu-I
Use n base plating bath. When a negative potential is applied to the plated body 13 and the potential of the plated body 13 is reduced, a certain voltage a
Then, Cu starts to precipitate, and at a certain voltage b, Cu and In start to precipitate. An alloy is made with Cu and In. At a voltage higher than the voltage b, In does not precipitate. The minimum difference between voltage b and voltage a is equal to the reduction potential difference 0.675V. As shown in FIGS. 5 and 6, when the potential of the body to be plated 13 is gradually lowered,
Cu starts to precipitate at 0.278V, and the amount of Cu increases with a decrease in potential.
Also starts to precipitate, and a Cu—In alloy starts to precipitate.

FIG. 7 is a diagram for explaining the relationship between the set potential and the Cu / In ratio that precipitates.

The Cu / In ratio is infinite while only Cu is precipitated and In is not deposited, but as the set potential is lowered, In starts to precipitate at -0.953 V, and the Cu / In ratio becomes It rapidly decreases and approaches a certain value. FIG. 7 shows this state.

(Example 4) Cu-In used in Example 3
A plating solution having the same composition as the base plating solution is placed in a plating tank to form a plating bath. Cr film 5 and Mo film 2 on glass substrate 1
Is formed in a plating bath to obtain a plated object. Plating was performed for 1 minute while the potential of the object to be plated was set to −0.7 V, and a Cu layer 6 having a thickness of 0.6 μm was formed on the Mo film 2 as shown in FIG.

Next, the voltage of the object to be plated was lowered to -1.5 V, and plating was performed for 5 minutes.
An alloy layer was obtained. When this Cu-In alloy layer was analyzed, it was found that Cu: In = 44: 56 in atomic%.

As described above, by utilizing the fact that the reduction potentials of Cu and In are distant from each other, it is possible to perform Cu base plating and Cu-In plating in a continuous operation using one plating tank and one kind of plating solution. I knew I could do it. Applying this principle to Cu-In / Se dispersion plating, if one plating tank and one kind of plating solution can form Cu or Cu-In base plating and Cu-In / Se dispersion plating in a continuous operation, equipment cost This is advantageous because the equipment installation area and man-hour can be reduced, and plating can be performed at low cost. However, since Se particles are dispersed in the Cu-In / Se dispersed plating solution, Cu or Cu There is a possibility that Se may be mixed into the -In base plating layer. This is because if Se is mixed, the Mo film comes into contact with Se, and there is no point in providing an intermediate layer. Therefore, it is necessary to take measures to prevent Se from being mixed into the Cu or Cu-In base plating layer.

FIG. 8 is a diagram showing the relationship between the stirring flow rate and the Se deposition amount in Cu—In / Se dispersion plating.

C having the same composition as the plating solution used in Example 1
Using a u-In / Se dispersed plating solution, Se powder is allowed to settle at the bottom of the plating tank without operating a stirrer. Therefore, the supernatant liquid is a liquid containing only Cu ions and In ions. In this state, Cr is placed on the glass substrate 1.
The film 5 and the Mo film 2 formed were placed in a plating bath to form a body to be plated, and the voltage of the body to be plated was set to −0.7 V;
Plating was performed by changing the plating time at a current density of 0.2 A / dm ² , and as shown in FIG. 1A, ten samples in which a Cu layer 6 was formed on the Mo film 2 were formed. Was analyzed, but no Se was detected.

Next, the voltage of the object to be plated was lowered to -1.5 V so that In was deposited, the current density was kept at 2 A / dm ² , stirring of the plating solution was started, and plating was performed at various stirring flow rates. Then, as shown in FIG. 1B, Cu-
Ten samples on which the In / Se dispersed plating layer 3 was formed were prepared, and the amount of Se in the layer 3 was analyzed, and the results shown in FIG. 8 were obtained. From FIG. 8, it can be seen that when there is no stirring of the plating solution, there is no precipitation of Se, and when stirring is started, the Se deposition amount increases rapidly with an increase in the stirring flow rate, and eventually becomes saturated.

(Example 5) The same Cu-In / Se dispersed plating solution (see Table 1) as the plating solution used in Example 1 was placed in a plating tank to form a plating bath. At this time, the Se powder is settled at the bottom of the plating tank without operating the stirrer.
In this state, the one in which the Cr film 5 and the Mo film 2 are formed on the glass substrate 1 is placed in a plating bath to be a plated object. The voltage of the object to be plated was set at 0.7 V so that only Cu was deposited and In was not deposited, and the current density was 0.2 A.
/ Dm ² for 5 minutes to form a Cu layer 6 having a thickness of 1.5 μm on the Mo film 2 as shown in FIG. The Se content in the Cu layer 6 was analyzed, but no Se was detected.

Next, the stirrer was operated to stir at a flow rate of 3 liters / minute per unit time to float the Se powder precipitated at the bottom of the plating tank and disperse it in the plating solution. The voltage of the object to be plated was reduced to -1.5 V, plating was performed for 5 minutes while maintaining the current density at 3 A / dm ² , and as shown in FIG.
In / Se dispersed plating layer 3 was obtained. This Cu-In / S
When the e-dispersion plating layer 3 was analyzed, it was Cu: In: Se = 33: 37: 30 in atomic%.

Next, as in the first embodiment, a heat treatment is performed in an atmosphere containing Se gas, and as shown in FIG.
Convert to InSe ₂ film 4. As a result, a solar cell equivalent to that of Example 1 was obtained.

(Embodiment 6) The same Cu-In /
Make a Se dispersion plating bath. As in Example 5, the Se powder is settled at the bottom of the plating tank without operating the stirrer. In this state, the one in which the Cr film 5 and the Mo film 2 are formed on the glass substrate 1 is placed in a plating bath to be a plated object.
The plating was performed for 1 minute while setting the voltage of the object to be plated at ─1.0 V and maintaining the current density at 0.7 A / dm ² so that both Cu and In were precipitated, as shown in FIG. The Cu—In alloy layer 8 having a thickness of 0.2 μm was formed on the Mo film 2. The Se content in the Cu—In alloy layer 8 was analyzed.
Se was not detected.

Next, the stirrer was operated to stir at a flow rate of 3 liters / minute per unit time to float the Se powder precipitated at the bottom of the plating tank and disperse it in the plating solution. The voltage of the object to be plated was reduced to -1.5 V, and plating was performed at a current density of 3 A / dm ² for 5 minutes.
As shown in (b), Cu-In / S of 1.5 μm thickness
The e-dispersion plating layer 3 was formed on the Cu-In alloy layer 8. When the Cu—In / Se dispersed plating layer 3 was analyzed, it was Cu: In: Se = 32: 39: 29 in atomic%.

Next, as in the first embodiment, a heat treatment is performed in an atmosphere containing Se gas, and as shown in FIG.
Convert to InSe ₂ film 4. As a result, a solar cell equivalent to that of Example 3 was obtained.

[0074]

As described above, in the present invention, since the conductive intermediate layer is provided between the molybdenum conductive film and the copper-indium-selenium dispersed plating layer, the molybdenum conductive film and selenium come into direct contact. To prevent the reaction of molybdenum and selenium, prevent the copper-indium-selenium alloy layer from peeling off, increase the yield,
A solar cell with reduced cost can be obtained.

In the present invention, the copper layer and the copper-indium-selenium plating can be performed in one plating tank and one kind of plating solution by changing the applied potential by utilizing the difference in the reduction potential between copper ions and indium ions. Since the layer can be formed, the equipment cost of the plating apparatus can be reduced, the installation area of the equipment cannot be increased, and the number of steps can be reduced.
A solar cell can be manufactured at low cost.

The plating method utilizing the difference in the reduction potential between copper ions and indium ions can be applied not only to the production of solar cells but also to general copper-indium plating.
Equipment costs, equipment installation area, and man-hours can be reduced, and plating can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method of manufacturing a solar cell according to a first embodiment of the present invention in the order of steps for explaining the same.

FIG. 2 is a cross-sectional view illustrating a solar cell manufacturing method according to a second embodiment of the present invention in the order of steps for explaining the second embodiment.

FIG. 3 is a cross-sectional view illustrating a method of manufacturing a solar cell according to a third embodiment of the present invention in the order of steps for explaining the third embodiment.

FIG. 4 is a side view of a plating bath used for the dispersion plating of the present invention.

FIG. 5 is a diagram illustrating a difference in the initiation of precipitation of Cu and Cu—In due to a reduction potential difference.

FIG. 6 is a diagram for explaining the relationship between the potential of an object to be plated and the amounts of Cu and Cu—In deposited.

FIG. 7 is a diagram for explaining a relationship between a set potential and a Cu / In ratio deposited.

FIG. 8 is a diagram showing the relationship between the stirring flow rate and the Se deposition amount in Cu—In / Se dispersion plating.

FIG. 9 is a cross-sectional view illustrating a first example of a conventional method of manufacturing a solar cell in the order of steps for explaining the example.

FIG. 10 is a temperature profile diagram showing heat treatment conditions performed in manufacturing a conventional thin-film solar cell.

FIG. 11 is a cross-sectional view illustrating a second example of a conventional method of manufacturing a solar cell in the order of steps for explaining the second example.

FIG. 12 is a cross-sectional view illustrating a mechanism of occurrence of a defect in a conventional solar cell manufacturing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Mo film 3 Cu-In / Se dispersion plating layer 4 CuInSe ₂ alloy layer 5 Cr layer 6 Cu layer 7 In layer 8 Cu-In alloy layer 11 Plating tank 12 Plating solution 13 Plated object 14 Counter electrode 15 Potency Ostat RE Reference electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (3)

(57) [Claims] A step of immersing a substrate having a molybdenum conductive film on its surface in a plating solution in which selenium particles are added to a solution in which copper ions and indium ions are dissolved; Applying a potential at which only copper is deposited on the molybdenum conductive film to form a copper layer on the molybdenum conductive film, and stirring the plating solution while the selenium particles are dispersed in the plating solution. Applying a potential at which copper and indium are deposited on the molybdenum conductive film to form a copper-indium-selenium plating layer on the copper layer; and heat treating at least the copper-indium-selenium plating layer with copper. Converting the indium-selenium alloy layer into an indium-selenium alloy layer. 2. a step of immersing a substrate having a molybdenum conductive film on a surface thereof in a plating solution in which selenium particles are added to a solution in which copper ions and indium ions are dissolved; Applying a potential at which copper and indium are deposited on the molybdenum conductive film to form a copper-indium alloy layer on the molybdenum conductive film, and stirring the plating solution so that the selenium particles are contained in the plating solution. Forming a copper-indium-selenium plating layer on the copper-indium alloy layer by applying a potential at which copper and indium are deposited on the molybdenum conductive film in a dispersed state; Converting the indium-selenium plating layer into a copper-indium-selenium alloy layer. 3. A step of immersing a substrate having a conductive film on a surface thereof in a plating solution containing at least copper ions and indium ions, and applying a potential at which only copper is deposited to the conductive film by applying a potential to the conductive film. Forming a copper layer, and applying a potential at which copper and indium are deposited to the conductive film to form a plating layer containing at least copper-indium on the copper layer. Plating method.