JP3011319B2 - Plating method and solar cell manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention comprises a plating method carried out using a solution containing a metal ion and a metal or non-metal particles, the production method, in particular the periodic table of the solar cell using this method 1
The present invention relates to a method for manufacturing a thin-film solar cell having an absorption layer of a compound semiconductor containing Group B, 3B, and 6B elements.

[0002]

Recently, it has excellent photoelectric conversion efficiency, peripheral as a thin-film solar cell having a large area can be manufactured at a low cost
Attention has been paid to compound semiconductors composed of Group 1B-3B-6B elements in the period table , and in particular, CuInSe ₂ is (1)
That the absorption coefficient α is as high as about 10 ⁵ / cm, and that a thin film of about 2 μm can sufficiently absorb sunlight, (2) the bandgap 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. In order to manufacture a large-area thin-film solar cell at low cost, Japanese Patent Application Laid-Open No. Hei 5-506334 (WO9)
As disclosed in Japanese Patent Publication No. 2/05586), a method for manufacturing a solar cell using a dispersion plating method has been proposed.

FIG. 12 is a cross-sectional view illustrating a conventional method of manufacturing a thin-film solar cell using a compound semiconductor in the order of steps for explaining the method.

First, as shown in FIG. 12A, a Mo film 2 is formed on a glass substrate 1 by a method such as evaporation or sputtering.
Prepare the one formed.

The plating solution is prepared, for example, at the following ratio. Copper sulfamate 0.01 M Indium sulfamate 0.5 M Sulfamate 0.104 M Se powder 0.633 M Here, M indicates mol / liter. Since the Se powder has poor affinity with the plating solution, a surfactant may be added to improve the affinity between the Se powder and the plating solution and improve the dispersion of the Se powder. Using the plating solution, electrodeposition is performed at a current density of 3 A / dm ² using the Mo film 2 as a cathode to form a Cu—In / Se dispersed plating layer 73. Tokuyohei Hei 5-506334 (International Publication WO92 / 0)
According to the data disclosed in Japanese Patent No. 5586), the composition of the plating layer is expressed by weight ratio (wt%): Cu: In: Se = 20.5: 44.1: 35.4 atomic ratio (at %), Cu: In: Se = 28.0: 33.2: 38.8.

Next, as shown in FIG. 12B, CuInSe is heat-treated in an Ar + H ₂ Se gas atmosphere in which Ar gas and H ₂ Se gas are mixed or in an Ar + Se gas atmosphere in which Ar gas and Se vapor are mixed. _The film is converted into _two films 74. As shown in FIG. 13, 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 400 ° C at 30 ° C / min
The temperature is raised to 条件 450 ° C., maintained at this temperature for about 2 to 4 hours, and then cooled to room temperature. 200 ° C ~ 250
It is said that the temperature of ° C. is the temperature at which alloying starts, and the temperature of 400 ° C. to 450 ° C. is the temperature at which CuInSe ₂ crystals grow.

[0007]

The absorption layer of the solar cell is C
When manufacturing using the u-In / Se dispersion plating method, what is ultimately desired is a CuInSe ₂ alloy layer, that is, an alloy layer having an atomic ratio of Cu: In: Se = 1: 1: 2. Since Se can be supplemented by heat treatment in an atmosphere containing Se gas, Se need not be 2, but Cu and In cannot be supplemented by heat treatment, so that Cu: In =
It is necessary that the ratio be close to 1: 1. According to the data of Japanese Patent Application Laid-Open No. 5-506334, this plating layer has an atomic ratio of Cu: In = 1: 1.186, and although there is a difference of nearly 20%, : 1. However, in order to obtain this composition, the plating solution contains Cu ions and In ions in a molar ratio of 1:50.
It is prepared at the ratio of That is, In ions are added 50 times as much as Cu ions. This is because the amount of deposited In is low, so that a large amount of In is required.

If the percentage of a certain element in the prepared plating solution that is deposited in the plating layer is defined as the utilization of that element, the utilization of In with respect to Cu is considerably low. Cu
As a result, the utilization ratio of In is only about 2% of that of Cu. This is considered to be due to the fact that the reduction potentials of Cu and In are apart. The reduction reaction between Cu and In is represented by the following equation. Cu ⁺⁺ + 2e ⁻ → Cu (reduction potential V = + 0.337 V) (1) In ⁺⁺⁺ + 3e ⁻ → In (reduction potential V = −0.3382 V) (2) where reduction potential V is , NHE (Normal Hyd)
(Reggen Electrode, standard hydrogen electrode). As described above, there is a difference of 0.6752 V in reduction potential between Cu and In, which is considered to be the cause of the fact that In is less likely to precipitate than Cu.

If the utilization of In is low, the amount of In must be increased, so that the cost of a Cu-In plating layer and a solar cell manufactured using a plating solution containing Cu and In increases. There's a problem.

An object of the present invention is to increase the utilization rate of In ions and reduce costs in a plating method for forming a Cu-In plating layer on a body to be plated using a plating solution containing Cu ions and In ions. To provide a plating method.

An object of the present invention is to increase the utilization rate of In ions and reduce costs in a method of manufacturing a solar cell using a plating method using a plating solution in which Cu ions and In ions are dissolved. An object of the present invention is to provide a method for manufacturing a solar cell.

[0012]

According to the present invention, there is provided a plating method for forming a plating layer containing copper-indium on a body to be plated using a plating solution containing copper ions and indium ions. And tartaric acid as an organic acid which forms a complex ion of copper and indium having a reduction potential close to each other by a complexing reaction with indium ions.

[0013]

[0014]

The present invention is characterized in that, in the plating method, the amount of the tartaric acid is 1 to 3.3 times the total of the moles of the copper ions and the indium ions in a molar ratio.

According to the present invention, in the plating method, the plating solution contains selenium particles dispersed therein, and the plating layer is a plating layer containing selenium.

According to the present invention, a copper-indium-selenium plating layer is formed on a conductive film provided on a substrate using a plating solution in which selenium particles are dispersed in a solution containing copper ions and indium ions. And a heat treatment of the plating layer to convert the plating layer to a copper-indium-selenium alloy film, wherein the plating solution undergoes a complexing reaction with the copper ions and indium ions to have a reduction potential. An organic acid which forms a complex ion of copper and indium close to each other is added.

According to the present invention, in the method for manufacturing a solar cell, the organic acid is citric acid or tartaric acid.

According to the present invention, in the method for manufacturing a solar cell, the amount of the citric acid added is 1 to 20 times the total number of moles of the copper ions and the indium ions in a molar ratio.

According to the present invention, in the method for manufacturing a solar cell, the amount of tartaric acid added is 1 to 3.3 times the total of the moles of the copper ion and the indium ion in a molar ratio. .

According to the present invention, in the method for manufacturing a solar cell, the selenium particles are colloidal selenium.

The present invention comprises a step of forming a copper-indium plating layer on a conductive film provided on a substrate using a plating solution containing copper ions and indium ions, and forming the plating layer on a gas containing selenium. Heat-treating in an atmosphere to form a copper-indium-selenium alloy film, wherein the plating solution is subjected to a complexing reaction with the copper ions and the indium ions to reduce the potential of copper and copper which are close to each other. An organic acid which forms an indium complex ion is added.

In the present invention, the copper-indium plating layer is formed and then heat-treated in a gas atmosphere containing selenium.
In a method for manufacturing a solar cell having a step of forming an indium-selenium alloy film, the organic acid is citric acid or tartaric acid.

According to the present invention, the copper-indium plating layer is formed and then heat-treated in a gas atmosphere containing selenium.
In a method for manufacturing a solar cell having a step of forming an indium-selenium alloy film, the amount of citric acid added is 1 to 20 times the total number of moles of the copper ions and indium ions in a molar ratio. And

According to the present invention, the copper-indium plating layer is formed and then heat-treated in a gas atmosphere containing selenium.
In a method for manufacturing a solar cell having a step of forming an indium-selenium alloy film, the amount of tartaric acid added is 1 in the molar ratio of the total number of moles of the copper ions and indium ions.
It is characterized in that it is double to 3.3 times.

[0026]

The reduction potential of Cu and In is set at 0.1 as described above.
Since they are separated from each other by 6752 V, it is necessary to bring their reduction potentials closer to each other in order to increase the indium utilization rate.
For this purpose, it is most preferable and most effective to add an organic acid which forms a complex ion of copper and indium having a reduction potential close to each other by a complexing reaction with copper ions and indium ions.

Citric acid or tartaric acid is selected as the organic acid. When citric acid is added, a complex ion having the following reduction potential Cu (citric acid) ⁺⁺ (reduction potential V = −0.27 V) (3) In (citric acid) ⁺⁺⁺ (reduction potential V = −0) .28V) (4) is generated, the reduction potential difference becomes only 0.01 V, and Cu
And the precipitation rate of In become very close to 1: 1 and the utilization rate of In is remarkably improved.

When tartaric acid is added, a complex ion having the following reduction potential Cu (tartaric acid) ⁺⁺ (reduction potential V = 0.12 V) (5) In (tartaric acid) ⁺⁺⁺ (reduction potential V = 0.08 V ) (6) is generated, the reduction potential difference becomes only 0.04 V, and Cu
And the precipitation rate of In become very close to 1: 1 and the utilization rate of In is remarkably improved.

Since the complex ion of citric acid has one ligand, the amount of citric acid must be at least that of copper ion and indium ion in order for all copper ions and indium ions in the plating solution to be complex ions. Must be equal to moles. Further, since not all of the citric acid added forms complex ions, the amount of citric acid added must be greater than the number of moles of copper ions and indium ions. According to experiments, it is effective to add citric acid up to 20 times the total number of moles of copper ions and indium ions. Therefore, the addition amount of citric acid is set to be 1 to 20 times the total number of moles of copper ions and indium ions in a molar ratio.

The amount of tartaric acid to be added is 1 to 3.3 times the total number of moles of copper ions and indium ions in a molar ratio for the same reason as in the case of citric acid.

The addition of citric acid or tartaric acid can be directly applied to a dispersion plating method for forming a copper-indium-selenium plating layer on a body to be plated using a plating solution in which selenium particles are dispersed.

The addition of an organic acid which forms a complex ion of copper and indium having a reduction potential which is close to each other by complexing reaction with copper ion and indium ion to the plating solution can be achieved by adding selenium particles to a solution of copper ion and indium ion. A copper-indium-selenium plating layer is formed using a plating solution in which is dispersed, and this is heat-treated to be converted to a copper-indium-selenium alloy film, and when a solar cell using this as an absorption film is manufactured. It can be applied as it is, can increase the indium utilization rate, and can manufacture a low-cost solar cell.

In the case of manufacturing the solar cell, citric acid or tartaric acid is selected as the organic acid.

In the manufacture of the solar cell, for the same reason as in the plating method, the amount of citric acid added is one mole of the total number of moles of copper ions and indium ions in a molar ratio.
Double to 20 times.

In the manufacture of the solar cell, the amount of tartaric acid added is 1 to 3.3 times the total number of moles of the copper ions and the indium ions in a molar ratio for the same reason as in the plating method. Double it.

When colloidal selenium is used as the selenium particles in the production of the solar cell, the dispersibility of selenium in the plating solution is remarkably improved. Reduction can be achieved.

The addition of an organic acid which forms a complex ion of copper and indium having a reduction potential close to each other by complexing with the copper ion and indium ion to the plating solution includes copper ion and indium ion, and contains selenium. The method can be applied as it is to a method of manufacturing a solar cell using a plating solution that does not contain it, and is effective.

In a method of manufacturing a solar cell using a plating solution containing copper ions and indium ions and not containing selenium, citric acid or tartaric acid is selected as the organic acid.

In a method of manufacturing a solar cell using a plating solution containing copper ions and indium ions and not containing selenium, the same reason as in the case of the above-described plating method is used.
The amount of citric acid added is 1 to 20 times the total number of moles of copper ions and indium ions in a molar ratio.

In a method of manufacturing a solar cell using a plating solution containing copper ions and indium ions and not containing selenium, the same reason as in the case of the above-mentioned plating method is used.
The amount of tartaric acid is 1 to 3.3 times the total number of moles of copper ion and indium ion in molar ratio.

[0041]

First, the plating method of the present invention will be described.

(Dispersion plating bath)

FIG. 2 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 (plated object 1
This is a potential for keeping the potential of 3) constant at a target potential, and is usually referred to as SSE (Saturated Sul) as a reference.
fat Electrode (saturated sulfuric acid electrode) or NHE (Normal Hydrogen Elect)
rod, standard hydrogen electrode). Here, NHE is used as the reference potential. Reference electrode RE
Is also used to change the working electrode (plated object 13) to a target potential. Working electrode (plated object 1
3) When the electrochemical reaction proceeds, the potential of the working electrode may change. The potentiostat 15 suppresses such a potential change, and changes the potential of the working electrode (plated object 13) with respect to the reference electrode RE to a target potential. Further, the potentiostat 15 is also used for controlling the current flowing through the working electrode to be constant . As the electrochemical reaction proceeds, the resistance of the plating solution changes, and the flowing current changes. The potentiostat 15 functions to adjust the voltage and keep the current constant.

(Example 1) First, a plating method when citric acid is added will be described. The plating solution was prepared as follows. CuSO as the copper ion source ₄ · 5H ₂ 0
The, In ₂ (SO ₄₎ as a source of indium ions _3.9
Using H ₂ 0, two types of copper ion amount of 0.01 mol and 0.05 mol, indium ion amount of 0.5 mol, 0.2 mol
5 mol, 3 mol of 0.05 mol, 1 mol of citric acid,
2 moles of 2 moles and a Cu / In mole ratio of 1/5
The combinations were made to be four types, 0, 1/10, 1/5, and 1/1. The combinations are as shown in Table 1. Table 1
, The pH (hydrogen ion concentration) is a measured value for each plating solution and is an unadjusted value. For each plating solution, the current density is changed and C
The u-In alloy plating layer is applied to an energy dispersive X-ray analyzer (Energy Dispersion X-ray).
Analyze) and analyze the atomic ratio (at
%), And the Cu / In ratio was calculated. These results are also shown in Table 1.

[0046]

[Table 1]

FIG. 3 is a diagram showing the data shown in Table 1 in the relationship between the current density and the Cu / In ratio to be deposited.
Kind of Cu / In molar ratio 1/50, 1/10, 1/5,
1/1 is represented as a parameter.

As can be seen from FIG. 3, the Cu / In ratio of the deposited plating layer largely depends on the current density. When a solar cell is manufactured, the Cu / In ratio is desirably close to 1, so that the current density that satisfies Cu / In = 1 may be selected.

FIG. 4 shows the data shown in Table 1 for the Cu of the plating solution.
FIG. 6 is a diagram showing the relationship between Cu / In and Cu / In of the plating layer,
Five types of current densities during plating are represented as parameters.

As can be seen from FIG. 4, the current density is 2.5
A / dm ² and Cu / I of plating solution
Except for the n mole ratio of 1/5 (= 0.2) or less, the Cu / In ratio of the deposited plating layer is proportional to the Cu / In mole ratio of the plating solution. When manufacturing solar cells, Cu / I
Since the n ratio is desirably close to 1, the Cu / In molar ratio and the current density of the plating solution may be selected so that Cu / In = 1.

FIG. 5 is a graph showing the data shown in Table 1 as a relationship between the current density and the Cu / In ratio to be deposited, and shows the amount of citric acid added to the plating solution as a parameter.

As can be seen from FIG. 5, the Cu / In ratio of the deposited plating layer is not significantly affected by the current density when the current density is higher than 4.5 A / dm ² . Also, C
The u / In ratio is higher when the amount of citric acid added is 1 mol / liter than when it is 2 mol / liter.

In Japanese Unexamined Patent Publication No. 5-506334, Cu: In = 28.0: 33.2 = 1: 1.18 in the plating layer.
In order to obtain No. 6, Cu / In = 1/50 was used in the plating solution. That is, 50 times as many In ions as Cu ions were required. In Sample Nos. 1, 2, and 3 of this example, which were prepared at the same ratio and to which citric acid was added, the amount of precipitation I
n is about 6 times as large as Cu. Cu / In precipitation ratio is 1
Nos. 5, 9, and 10 for Cu / In plating solution
The molar ratio is 1/10, 1/5, which is 1/5 to 1 /
It is 10. This means that the utilization rate of In is 5 to 1
This indicates that it has increased to 0 times.

The increase in the utilization rate of In is due to the fact that Cu and In
It is considered that the complex ions respectively formed complex ions with citric acid, and the reduction potential approached. Cu and citric acid form a complex ion having the structure shown in Chemical formula 1, and In and citric acid form a complex ion having the structure shown in Chemical formula 2, respectively. It is known that the number of ligands is 1 in the case of Cu. Although the number of ligands in the case of In has not been confirmed, it is estimated that the number of ligands will also be 1 from an example of a complex ion of trivalent Al and citrate.

[0055]

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[0056]

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The reduction potential of these complex ions is Cu (citric acid) ⁺⁺ (reduction potential V = −0.27 V) (3) In (citric acid) ⁺⁺⁺ (reduction potential V = −0.28 V) ) (4), and the reduction potential difference is only 0.01 V. Therefore, the precipitation ratio of Cu and In becomes very close to 1: 1 and In and
The usage rate of the system is significantly improved.

Since the number of ligands of the complex ion of citric acid is 1, in order for all the copper ions and indium ions in the plating solution to be complex ions, the amount of citric acid must be at least that of copper ions and indium ions. Must be equal to moles. Further, since not all of the citric acid added forms complex ions, the amount of citric acid added must be greater than the number of moles of copper ions and indium ions. As shown in Sample No. 23 of Table 2, the effect can be seen even if 2 mol of citric acid is added to the total of 0.1 mol of the copper ion and the indium ion, so that the amount of citric acid added is And the total number of moles of copper ions and indium ions is 1 to 20 times.

(Example 2) Next, an example of a method for manufacturing a solar cell of the present invention using citric acid will be described.

FIG. 1 is a sectional view showing the steps of a method for manufacturing a solar cell according to an embodiment of the present invention using citric acid in the order of steps.

First, as shown in FIG. 1A, a glass substrate 1 on which a Mo film 2 is formed by a method such as vapor deposition or sputtering is prepared.

The dispersion plating solution was prepared with the following composition. _{CuS0 4 · 5H 2 O 0.05M In} 2 (S0 4) 3 · 9H 2 O 0.5 M citric put acid 1.0 M Se powder 0.63M plating solution in a plating bath of Fig. 2, the current density 3A /
dm ² , and a CuIn / Se dispersed plating layer 3
Was formed. The composition of the plating layer 3 was analyzed by an energy dispersive X-ray analyzer, and a result of atomic ratio (at%) of Cu: In: Se = 31.5: 30.8: 37.7 was obtained. Looking at the amount of In with respect to Cu, the plating solution had a Cu / In molar ratio of 1/10, and
Although it is 1/5 of the data of JP-A-334, it is equivalent in the amount of precipitation. That is, comparing with the data described in Japanese Patent Application Laid-Open No. 5-506334, In
It can be seen that the utilization rate of is increased by 5 times.

Next, as shown in FIG. 1B, 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. The heat treatment is shown in FIG.
As shown in the figure, the temperature is raised from room temperature to 200 ° C. at a rate of 30 ° C./min, held at this temperature for about 30 minutes, then raised to 400 ° C. at a rate of 30 ° C./min, and held at this temperature for about 2 hours And then cooled to room temperature. The obtained CuInSe
_The composition analysis of the _two films 4 was performed by an energy dispersive X-ray analyzer, and the result was Cu: In: Se = 24: 25: 51.

Embodiment 3 Next, another embodiment of the method of manufacturing a solar cell according to the present invention using citric acid will be described.

FIG. 6 is a sectional view showing the steps of a method for manufacturing a solar cell according to another embodiment of the present invention when citric acid is used.

First, as shown in FIG. 6A, a glass substrate 1 on which a Mo film 2 is formed by a method such as vapor deposition or sputtering is prepared.

The dispersion plating solution was prepared with the following composition. _{CuS0 4 · 5H 2 O 0.05M In} 2 (S0 4) 3 · 9H 2 O 0.25M citric put acid 1.0 M plating solution in a plating bath of Fig. 2, current density 3.3
Plating was performed at 3 A / dm ² to form a Cu—In alloy plating layer 23. The composition of the plating layer 23 was analyzed by an energy dispersive X-ray analyzer, and the result was Cu: In = 52.78: 47.22. Looking at the amount of In with respect to Cu, the plating solution had a Cu / In molar ratio of 1/5, and
Although it is 1/10 of the data of JP-A No. 34, it is equivalent in the amount of precipitation. That is, comparing with the data described in Japanese Patent Application Laid-Open No. 5-506334, In
It can be seen that the utilization rate of is increased by 10 times.

Next, in the same manner as in Example 2, heat treatment is performed in an atmosphere containing Se gas, and as shown in FIG.
It was converted to a CuInSe ₂ film 24. Obtained CuInS
The composition analysis of the e ₂ film 24 was performed with an energy dispersive X-ray analyzer, and the result was that the atomic ratio (at%) was Cu: In: Se = 23: 25: 52.

Example 4 In Example 4, in preparing a dispersion plating solution, a Se colloid was used instead of using Se particles. The Se colloid was prepared as follows. First, a Se colloid solution was prepared by the following formulation. Selenous acid (H ₂ SeO ₃ ) (0.1 M) 5 ml Hydrazine sulfate (N ₂ H ₆ SO ₄ ) (0.1 M) 5 ml Gelatin (4 g / l) 2 ml Pure water 18 ml where M is mol / liter Show. After mixing these,
The mixture was heated at 40 ° C. for about 45 minutes to prepare a Se colloid solution. The gelatin is added to stabilize the colloid. Further, the pH was adjusted to 2 to stabilize the colloid. When the Se colloid solution thus prepared was examined with a scanning electron microscope, the particle size of the Se colloid was about 10
~ 100 nm, 1/150 of the particle size of conventional Se particles
It was 1/15. Since the particle size was so small, Se particles did not precipitate even after a long period of time, and the Se colloid solution was very stable.

Next, a plating solution having the following composition was prepared using the Se colloid solution. _{CuS0 4 · 5H 2 O (1.2g} / l) 5mM In 2 (S0 4) 3 · 9H 2 O (34.0g / l) 50mM citric acid _{(53.0g / l) 250mM Na 2} SO 4 (11. (4 g / l) 80 mM Se colloid (2.4 g / l) 30 mM Here, mM indicates mmol / liter. This plating solution was put into the plating bath of FIG. 2 and plating was performed at a current density of 3 A / dm ² , and as shown in FIG.
The dispersion plating layer 33 was formed. The composition of the plating layer 33 was analyzed by an energy dispersive X-ray analyzer, and a result of atomic ratio (at%) of Cu: In: Se = 28: 32: 41 was obtained.

Next, as in the second embodiment, a heat treatment is performed in an atmosphere containing Se gas to form a C gas as shown in FIG.
The film was converted to a uInSe ₂ film. The obtained CuInSe
_The composition analysis of the _two films 34 was performed by an energy dispersive X-ray analyzer, and the result was that Cu: In: Se = 23: 25: 52 in atomic ratio (at%).

(Example 5) Next, a plating method when tartaric acid is added will be described. The plating solution was prepared as follows. The CuSO ₄ · 5H ₂ O as source of copper ions,
As the source of indium ions _{In 2 (SO 4) 3 ·} 9H 2
O was used, the amount of copper ions was 0.05 mol, the amount of indium ions was 0.25 mol, two kinds of 0.5 mol, the amount of tartaric acid was 1 mol, and the Cu / In molar ratio was 1/5, 1 /. 10
Were combined to be two types. Table 2 shows the combinations.
As shown in FIG. In Table 2, pH (hydrogen ion concentration) is a measured value for each plating solution and is an unadjusted value. For each plating solution, the current density was changed, and the Cu-In alloy plating layer deposited on the plate 13 was converted to an energy dispersive X-ray analyzer (Energy Disperser).
A composition analysis was performed by using an X-ray Analyzer (sion X-ray Analyzer), the composition was represented by an atomic ratio (at%), and a Cu / In ratio was calculated. These results are also shown in Table 2.

[0073]

[Table 2]

FIG. 8 is a diagram showing the data shown in Table 2 in relation to the current density and the Cu / In ratio of the plating layer to be deposited, and shows the Cu / In ion ratio in the plating solution as a parameter.

As can be seen from FIG. 8, the Cu / In ratio of the deposited plating layer tends to decrease as the current density increases, and approaches 1.0. The slope of the decrease is smaller when the Cu / In ion ratio in the plating solution is smaller. This is probably because Cu, In and tartaric acid formed a complex ion, and the reduction potential changed.

In Japanese Unexamined Patent Publication No. 5-506334, in order to obtain the same precipitation of Cu and In in the plating layer, the plating solution requires 50 times as many In ions as Cu ions. On the other hand, in the present embodiment, even when the molar ratio of Cu / In is 1/10 to 1/5, almost the same precipitation of Cu and In is obtained. This indicates that the utilization rate of In increased by 5 to 10 times depending on the amount of tartaric acid added.

The increase in the utilization rate of In is because Cu and In
Is thought to form a complex ion with tartaric acid, respectively, and the reduction potential was approached. Cu and tartaric acid form a complex ion having the structure shown in Chemical formula 3, and In and tartaric acid form a complex ion having the structure shown in Chemical formula 4, respectively. The number of ligands is Cu, I
It is known that both n are 1.

[0078]

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[0079]

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The reduction potential V of these complex ions is Cu (tartaric acid) ⁺⁺ (reduction potential V = 0.12 V) (5) In (tartaric acid) ⁺⁺⁺ (reduction potential V = 0.08 V) ( 6) and the reduction potential difference is only 0.04 V. Therefore, the precipitation ratio of Cu and In becomes very close to 1: 1 and In and
The usage rate of the system is significantly improved.

Since the complex ion of tartaric acid has one ligand, the amount of tartaric acid must be at least the number of moles of copper ion and indium ion in order for all copper ions and indium ions in the plating solution to be complex ions. Must be equal to In addition, since not all of the tartaric acid added forms complex ions, the amount of tartaric acid needs to be larger than the number of moles of copper ions and indium ions. Table 2
As shown in Sample No. 1, the effect can be seen even if 1 mol of tartaric acid is added to the total of 0.3 mol of the copper ion and the indium ion, so that the amount of tartaric acid added is
1 times the total number of moles of copper ion and indium ion
3.3 times.

(Example 6) Next, an example of a method for manufacturing a solar cell of the present invention using tartaric acid will be described.

FIG. 9 is a sectional view showing the steps of a method for manufacturing a solar cell according to an embodiment of the present invention using tartaric acid in the order of steps.

First, as shown in FIG. 9A, a glass substrate 1 having a Mo film 2 formed thereon by a method such as vapor deposition or sputtering is prepared.

The dispersion plating solution was prepared with the following composition. _{CuS0 4 · 5H 2 O (12.5g} / l) 0.05M In 2 (S0 4) 3 · 9H 2 O (170.0g / l) 0.25M tartaric acid (150.0g / l) 1.0 M Se powder (50.0 g / l) 0.63M This plating solution was put into the plating bath of FIG.
dm ² , and a CuIn / Se dispersed plating layer 4
3 was formed. This plating layer 43 is formed by an energy dispersing type X
The composition was analyzed by a line analyzer, and the result was that Cu: In: Se = 42.0: 44.0: 14.0 in atomic ratio (at%). Looking at the amount of In with respect to Cu, the plating solution had a Cu / In molar ratio of 1/5, and
Although it is 1/10 of the data of JP-A No. 34, the amount of precipitation is larger in In than in Cu. That is,
Comparing with the data described in Japanese Patent Application Laid-Open No. 5-506334, it can be seen that the utilization rate of In is increased by 10 times or more.

Next, in the same manner as in Example 2, heat treatment is performed in an atmosphere containing Se gas, and as shown in FIG.
It was converted to a CuInSe ₂ film 44. Obtained CuInS
The composition analysis of the e ₂ film 34 was performed by an energy dispersive X-ray analyzer, and the result was Cu: In: Se = 23: 25: 52.

Embodiment 7 FIG. 10 is a sectional view showing the steps of a method of manufacturing a solar cell according to another embodiment of the present invention using tartaric acid in the order of steps.

First, as shown in FIG. 10A, a Mo film 2 is formed on a glass substrate 1 by a method such as evaporation or sputtering.
Prepare the one formed.

The dispersion plating solution was prepared with the following composition. _{CuS0 4 · 5H 2 O 0.05M In} 2 (S0 4) Put ₃ · 9H ₂ O 0.50 M tartaric acid 1.0 M plating solution in a plating bath of Fig. 2, current density 3.5
Plating with A / dm ² , Cu-In alloy plating layer 5
3 was formed. This plating layer 53 is formed by an energy dispersing type X
A composition analysis was performed by a line analyzer, and a result of atomic ratio (at%) of Cu: In: Se = 56.17: 43.83 was obtained. Looking at the amount of In with respect to Cu, the plating solution had a Cu / In molar ratio of 1/10, and
Although it is 1/5 of the data of JP-A-334, the amount of precipitation is larger in In than in Cu. That is,
Comparing with the data of Japanese Patent Application Laid-Open No. 5-506334 described above, it can be seen that the utilization rate of In is increased by 5 times or more.

Next, as in the second embodiment, the Se gas is
Heat treatment in an atmosphere containing
In addition, CuInSe_TwoConverted to membrane 54. The obtained CuI
nSe _TwoComposition of film 44 with energy dispersive X-ray analyzer
The analysis was performed, and the result of Cu: In: Se = 23: 25: 52 was obtained.

Example 8 In Example 8, in preparing a dispersion plating solution, a Se colloid was used instead of using Se particles. The Se colloid was prepared in exactly the same manner as in Example 4. Using this Se colloid solution, a plating solution was prepared with the following composition. _{CuS0 4 · 5H 2 O (1.2g} / l) 5mM In 2 (S0 4) 3 · 9H 2 O (34.0g / l) 50mM tartrate _{(37.5g / l) 250mM Na 2} SO 4 (11.4g / l) 80mM Se colloid (2.4 g / l) 30 mM This plating solution was put into the plating bath of FIG.
dm ² , and as shown in FIG.
The uIn / Se dispersed plating layer 63 was formed. The composition of the plating layer 63 was analyzed by an energy dispersive X-ray analyzer, and a result of atomic ratio (at%) of Cu: In: Se = 30: 35: 35 was obtained.

Next, in the same manner as in Example 2, heat treatment was performed in an atmosphere containing Se gas to convert into a CuInSe ₂ film 64 as shown in FIG. Obtained CuInS
The composition analysis of the e ₂ film 34 was performed by an energy dispersive X-ray analyzer, and a result of atomic ratio (at%) of Cu: In: Se = 23: 26: 51 was obtained.

As shown in the above examples, when citric acid or tartaric acid is added to a plating solution as an organic acid which forms a complex ion which causes a complexing reaction with Cu and In to bring the reduction potentials closer to each other, The utilization rate of In can be remarkably increased as compared with. Examples have confirmed that the addition of such an organic acid is effective regardless of the presence or absence of selenium particles.

[0094]

As described above, according to the present invention, Cu
Since citric acid or tartaric acid was added to the plating solution as an organic acid that forms a complex ion that forms a complex ion by causing a complexing reaction with In and the mutual reduction potential, the amounts of Cu and In deposited approach, and the utilization rate of In decreases. It is possible to obtain a plating method which increases the cost and reduces the cost.

In the present invention, since the above-described plating method is used, a solar cell in which the utilization rate of In is increased and the cost is reduced can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention using citric acid in a process order.

FIG. 2 is a side view of a plating bath used for the dispersion plating of the present invention.

FIG. 3 Current density in plating bath and Cu / I deposited
It is a figure showing the relation with n ratio.

FIG. 4 is a diagram showing a relationship between a Cu / In ratio in a plating solution and a Cu / In ratio in a deposited plating layer.

FIG. 5: Current density in plating bath and Cu / I deposited
It is a figure which shows the effect of citric acid on n ratio.

FIG. 6 is a cross-sectional view shown in the order of steps for explaining another embodiment of the method of manufacturing a solar cell of the present invention using citric acid.

FIG. 7 is a cross-sectional view illustrating a method of manufacturing a solar cell according to still another embodiment of the present invention using citric acid in the order of steps for explaining the embodiment.

FIG. 8: Current density in plating bath and Cu / I deposited
It is a figure which shows the influence of the Cu / In ion ratio in the plating solution on n ratio.

FIG. 9 is a cross-sectional view illustrating a method of manufacturing a solar cell according to an embodiment of the present invention in the case of using tartaric acid, in the order of steps for explaining the example.

FIG. 10 is a sectional view shown in order of steps for explaining another embodiment of the method of manufacturing a solar cell of the present invention when tartaric acid is used.

FIG. 11 is a cross-sectional view illustrating a method of manufacturing a solar cell according to another embodiment of the present invention using tartaric acid in the order of steps for explaining the embodiment.

FIG. 12 is a cross-sectional view illustrating a conventional method of manufacturing a solar cell in the order of steps for explaining the example.

FIG. 13 is a temperature profile diagram showing heat treatment conditions performed in the manufacture of a conventional solar cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Mo film 3 Cu-In / Se dispersed plating layer 4 CuInSe ₂ alloy layer 11 Plating tank 12 Plating solution 13 Plated object 14 Counter electrode 15 Potentiostat RE Reference electrode

Claims (12)

(57) [Claims] In a plating method for forming a plating layer containing copper-indium on a body to be plated using a plating solution containing copper ions and indium ions, the plating solution undergoes a complexing reaction with the copper ions and indium ions. A plating method , wherein tartaric acid is added as an organic acid which forms a complex ion of copper and indium whose reduction potentials are close to each other. 2. The amount of tartaric acid added in a molar ratio of 1 to 3 times the total number of moles of said copper ions and indium ions.
2. The plating method according to claim 1 , wherein the plating method is tripled. 3. The plating method according to claim 1, wherein the plating solution contains selenium particles dispersed therein, and the plating layer is a plating layer containing selenium. 4. A step of forming a copper-indium-selenium plating layer on a conductive film provided on a substrate using a plating solution in which selenium particles are dispersed in a solution containing copper ions and indium ions. Heat-treating the plating layer,
Converting the indium-selenium alloy film to a solar cell, wherein the plating solution forms a complex reaction between the copper ion and the indium ion with the copper ion and the indium ion to form copper and indium complex ions whose reduction potentials are close to each other. A method for producing a solar cell, comprising adding an acid. 5. The method according to claim 4, wherein the organic acid is citric acid or tartaric acid. 6. The amount of citric acid added is 1 to 2 times the total number of moles of said copper ions and indium ions in a molar ratio.
Claim 4 or method of manufacturing a solar cell according to claim 5, characterized in that a 0-fold. 7. The amount of tartaric acid added in a molar ratio of 1 to 3 times the total number of moles of the copper ions and indium ions.
6. The method for manufacturing a solar cell according to claim 5 , wherein the number is three times. 8. The method according to claim 4, wherein the selenium particles are colloidal selenium. 9. A step of forming a copper-indium plating layer on a conductive film provided on a substrate using a plating solution containing copper ions and indium ions, and forming the plating layer in a gas atmosphere containing selenium. Heat-treated with copper-indium-
Forming a selenium alloy film, wherein the plating solution comprises an organic acid which forms a complex ion of copper and indium having a reduction potential close to each other by a complexing reaction with the copper ion and indium ion. A method for manufacturing a solar cell, wherein the method further comprises adding the solar cell. 10. The method according to claim 9, wherein the organic acid is citric acid or tartaric acid. 11. The method for manufacturing a solar cell according to claim 10 , wherein the amount of citric acid added is 1 to 20 times the total number of moles of said copper ions and indium ions in a molar ratio. 12. The method for manufacturing a solar cell according to claim 10 , wherein the amount of tartaric acid added is 1 to 3.3 times the total number of moles of said copper ions and indium ions in a molar ratio. .