JP4829926B2 - Solar cell and method for manufacturing solar cell - Google Patents

Description

  The present invention relates to a solar cell and a method for manufacturing a solar cell, for example, a solar cell suitable for use in a chalcopyrite solar cell and a method for manufacturing the solar cell.

In general, a chalcopyrite solar cell has a Mo (molybdenum) electrode layer to be a back electrode formed on a glass substrate, and a CIGS light absorption layer made of Cu (In + Ga) Se ₂ is formed on the Mo electrode layer. A transparent electrode layer made of ZnO: Al or the like is formed on the CIGS light absorption layer via a buffer layer made of ZnS, CdS, or the like (see, for example, Patent Document 1).

  The CIGS light absorption layer is formed by a selenization method in which a Se compound is generated by a thermochemical reaction using a Se source such as H2Se gas using a metal precursor (precursor) film, for example. Furthermore, it has been found that a MoSe layer is formed between the CIGS light absorption layer and the Mo electrode layer.

  This MoSe film is thought to improve the heterocontact at the interface between the CIGS light absorption layer and the Mo electrode layer from a Schottky junction to an ohmic junction, and contributes to improvement of characteristics such as open-circuit voltage characteristics of chalcopyrite solar cells. It functions as an important interface layer (see, for example, Patent Document 2).

Japanese Patent No. 3876440 JP 2006-13028 A

  By the way, the performance evaluation of the solar cell is performed with the open circuit voltage (Voc), the short circuit current (Isc), the fill factor (FF), and the conversion efficiency (η).

  Here, the open circuit voltage refers to the voltage between the output terminals when the output terminal of the solar cell (module) is opened. The fill factor (FF) is a value obtained by dividing the maximum output by the product of the open circuit voltage and the short circuit current. The conversion efficiency is a value (%) obtained by dividing the maximum output by the product of the surface of the solar cell (module) and the irradiance.

  The MoSe layer described above has a problem that the electrical resistance is large, and when it grows excessively thick, the fill factor (FF) is lowered. Since the MoSe layer is naturally generated as a secondary, it is conceivable to terminate selenization in a short time to limit the growth of the MoSe layer. However, CIGS light composed of a CIS single phase with a uniform composition There arises a problem that the absorption layer cannot be formed and a new problem that peeling (interface peeling) occurs at the interface between the CIGS light absorption layer and the Mo electrode layer. Thus, it was difficult to arbitrarily control the generation of the MoSe layer.

  The present invention has been made in consideration of such problems, and an interface layer that contributes to improvement of characteristics such as open-circuit voltage characteristics of chalcopyrite solar cells is formed uniformly and with an appropriate film thickness. An object of the present invention is to provide a solar cell and a method for manufacturing the solar cell, which can improve the photoelectric conversion efficiency while simultaneously suppressing the increase in resistance of the back electrode and the suppression of the interface peeling with the light absorption layer.

The solar cell according to the first invention is
A back electrode layer;
A CIGS light absorbing layer formed on the back electrode layer;
A transparent electrode formed on the CIGS light absorption layer via a buffer layer;
The back electrode layer has a first electrode layer and a second electrode layer containing oxygen formed on the first electrode layer,
Between the CIGS light absorption layer and the second electrode layer of the back electrode layer, a reaction layer of a metal constituting the second electrode layer and selenium constituting the CIGS light absorption layer is interposed ,
The metal constituting the second electrode layer of the back electrode layer is Mo (molybdenum),
The reaction layer is characterized MoSe Sodea Rukoto.

  Thereby, the interface layer (reaction layer) contributing to the improvement of the characteristics of the chalcopyrite solar cell can be formed uniformly and with an appropriate film thickness, the resistance increase of the back electrode can be suppressed, the light absorption layer and The photoelectric conversion efficiency can be improved while simultaneously suppressing the interfacial peeling.

Then, in the first aspect of the present invention, as the material of the first electrode layer before Symbol back electrode, in addition to Mo, TiN (titanium nitride), Fe (iron), a conductive metal such as Al (aluminum) Can be used.

Then, in the first aspect of the present invention, the metal constituting the first electrode layer of the back electrode layer, the metal constituting the second electrode layer may be both Mo (molybdenum).

Next, the manufacturing method of the solar cell according to the second aspect of the present invention is as follows.
A first electrode layer forming step of forming a first electrode layer on the substrate;
A second electrode layer forming step of forming a second electrode layer containing oxygen on the first electrode layer;
A surface treatment step of removing a part of the surface of the second electrode layer;
A precursor forming step of forming a CIGS light absorbing layer precursor on the second electrode layer;
The precursor was treated selenide to have a selenide step of the CIGS absorber layer,
The metal constituting the second electrode layer is Mo (molybdenum).
The surface treatment step removes oxygen from the surface of the second electrode layer with an alkaline solution,
By the selenization step, the precursor becomes the CIGS light absorption layer, and the metal constituting the second electrode layer and the CIGS light absorption layer are formed between the CIGS light absorption layer and the second electrode layer. the reaction layer of selenium which is formed, characterized in Rukoto.

  In the second aspect of the present invention, the interface layer (reaction layer) contributing to the improvement of the characteristics of the chalcopyrite solar cell can be formed uniformly and with an appropriate film thickness, which increases the resistance of the back electrode. Photoelectric conversion efficiency can be improved while achieving both suppression and suppression of interface peeling with the light absorption layer.

In the second aspect of the present invention, the metal constituting the pre-Symbol first electrode layer, the metal constituting the second electrode layer may be both Mo (molybdenum). By using Mo, an electrode layer having a low electrical resistivity can be formed as the back electrode, and when the back electrode layer is formed on the glass substrate, the thermal expansion coefficient is substantially the same as that of the glass substrate. Therefore, it is advantageous for suppressing film peeling and the like due to heat stress. Mo has a relatively high corrosion resistance against selenium, but since the second electrode layer containing oxygen is present on the upper layer, the corrosion resistance against selenium is further improved. That is, the progress of the reaction between selenium and Mo by selenization can be stopped at the second electrode layer. As a result, a reaction layer (MoSe layer) of selenium and Mo can be formed only in a portion where a part of the surface is removed. That is, in the surface treatment process, it is possible to arbitrarily control the growth of the reaction layer (MoSe layer) of selenium and Mo.

  In the second aspect of the present invention, the second electrode layer forming step uses a sputtering method to form the second electrode layer by mixing oxygen, water vapor, or air containing oxygen in a sputtering gas. It may be.

  Thus, for example, after the first electrode layer is formed by sputtering, oxygen, water vapor, or air containing oxygen is mixed into the sputtering gas introduced into the sputtering chamber, thereby continuously forming the second electrode layer. can do. This can shorten the film formation time of the electrode layer and simplify the manufacturing equipment.

  In the second aspect of the present invention, in the second electrode layer forming step, the sputtering chamber used in the first electrode layer forming step is used, and air or water vapor remaining in the sputtering chamber is taken into Mo. The second electrode layer may be formed by performing sputtering under conditions (for example, increasing the gas pressure of the sputtering gas).

  Thereby, for example, air or water vapor remaining in the sputtering chamber in which the first electrode layer is formed can be used as it is, so that it is possible to further shorten the time for forming the electrode layer and simplify the manufacturing equipment.

Pre Symbol surface treatment step, with an alkaline solution, so that removal of oxygen from the surface of the second electrode layer. That is, by removing oxygen from the surface of the second electrode layer by a reduction reaction of the alkaline solution, a layer having a sparse metal element density can be formed on the surface of the second electrode layer.

  Accordingly, in the subsequent selenization step, the metal element in the layer having a low density of the metal element is easily bonded to selenium, and a reaction layer with selenium is formed on the surface of the second electrode layer. Since the second electrode layer containing oxygen exists in the lower layer of the layer having a low density of the metal element, the reaction of selenium stops at the surface portion of the second electrode layer, or the reaction to the lower layer than that. Will almost never happen. As a result, an extremely thin reaction layer is formed between the second electrode layer containing oxygen and the light absorption layer.

  As the alkaline solution, a sodium tetraborate solution, an ammonium tetraborate solution, or an ammonia solution can be used. In particular, when a sodium-containing alkaline solution is used as the alkaline solution, it is preferable to have a washing step of washing away sodium after the surface treatment step in order to improve photoelectric conversion efficiency.

  As described above, according to the solar cell and the method for manufacturing a solar cell according to the present invention, the interface layer contributing to the improvement of the characteristics of the chalcopyrite solar cell is formed uniformly and with an appropriate film thickness. Thus, it is possible to improve the photoelectric conversion efficiency while simultaneously suppressing the resistance increase of the back electrode and the interface peeling with the light absorption layer.

  Hereinafter, an embodiment in which a solar cell and a method for manufacturing a solar cell according to the present invention are applied to, for example, a chalcopyrite solar cell will be described with reference to FIGS.

  As shown in FIG. 1, a solar cell 10 according to the present embodiment includes a glass substrate 12 such as soda lime glass, and a back electrode layer 14 formed on the glass substrate 12 and serving as a back electrode (plus electrode). And a CIGS light absorption layer 16 formed on the back electrode layer 14, and a buffer layer 18 made of, for example, InS on the CIGS light absorption layer 16 and made of ZnO: Al or the like serving as a negative electrode. A transparent electrode layer 20.

  And in this Embodiment, the back surface electrode layer 14 has the 1st electrode layer 14a and the 2nd electrode layer 14b containing the oxygen formed on this 1st electrode layer 14a. Further, a reaction layer 22 of a metal constituting the second electrode layer 14b and selenium constituting the CIGS light absorption layer 16 is interposed between the CIGS light absorption layer 16 and the second electrode layer 14b of the back electrode layer 14. ing. In particular, the metal constituting the first electrode layer 14a of the back electrode layer 14 and the metal constituting the second electrode layer 14b are both Mo (molybdenum), and the reaction layer 22 with selenium is a MoSe layer. Of course, as a constituent material of the first electrode layer 14a, a conductive metal such as TiN, Fe, or Al can be used in addition to the above-described Mo.

  Here, a method for manufacturing solar cell 10 according to the present embodiment will be described with reference to FIGS.

  First, in step S1 (first electrode layer forming step) in FIG. 2, as shown in FIG. 3A, a first electrode layer 14a serving as a back electrode is formed on the glass substrate 12 by, for example, sputtering. As the metal material of the first electrode layer 14a, a wide range of inexpensive materials with low electrical resistivity can be selected as the back electrode, and in particular, a metal material having a thermal expansion coefficient almost the same as the thermal expansion coefficient of the glass substrate 12 is selected. By doing so, it becomes advantageous for suppression of film peeling or the like due to thermal stress. In the present embodiment, Mo (molybdenum) is used as a metal material that satisfies these conditions. Mo is suitable as a metal material for the back electrode because it satisfies the above conditions and has high corrosion resistance to selenium.

  Thereafter, in step S2 (second electrode layer forming step) in FIG. 2, as shown in FIG. 3B, a second electrode layer 14b containing oxygen is formed on the first electrode layer 14a. It is preferable to select the same Mo as the metal material of the first electrode layer 14a as the metal material of the second electrode layer 14b.

When Mo is selected as the metal material of the second electrode layer 14b, the second electrode layer 14b becomes a Mo layer containing oxygen, and the Mo layer containing oxygen is a MoO ₂ (molybdenum dioxide) layer, MoO ₃ ( In addition to the molybdenum trioxide layer, a MoO _m (0 <m <2) layer, a MoO _n (2 <n <3) layer, and the like are included.

  Here, as a method of forming the second electrode layer 14b containing oxygen, there are the following two methods (first method and second method).

  The first method is a method in which oxygen, water vapor, or air containing oxygen is mixed in a sputtering gas to form the second electrode layer 14b containing oxygen by using a sputtering method.

  For example, after the first electrode layer 14a is formed by sputtering, oxygen, water vapor, or air containing oxygen is mixed into the sputtering gas (rare gas) introduced into the sputtering chamber, so that the first electrode layer 14a continuously contains oxygen. A two-electrode layer 14b can be formed. This can shorten the film formation time of the second electrode layer 14b and simplify the manufacturing equipment.

  The second method uses a sputtering chamber in which the first electrode layer 14a is formed, and performs sputtering under conditions that allow air or water vapor remaining in the sputtering chamber to be taken into Mo (for example, increasing the gas pressure of the sputtering gas). And the second electrode layer 14b containing oxygen is formed. For example, the product of the gas pressure and the distance between the target and the substrate is preferably 30 Pa · cm or more, and the second electrode layer 14b is preferably formed. In this case, for example, air or water vapor remaining in the sputtering chamber in which the first electrode layer 14a is formed can be used as it is, so that the film formation time of the second electrode layer 14b can be further shortened and the manufacturing equipment can be further simplified. be able to.

  Thereafter, the glass substrate 12 on which the second electrode layer 14b is formed is taken out of the sputtering chamber, and in step S3 (surface treatment step) in FIG. 2, a part of the surface of the second electrode layer 14b is removed as shown in FIG. 3C. Remove (surface etching). Specifically, oxygen is removed from the surface of the second electrode layer 14b by bringing the surface of the second electrode layer 14b into contact with an alkaline solution. That is, by removing oxygen from the surface of the second electrode layer 14b by a reduction reaction of the alkaline solution, a layer 24 having a sparse Mo density is formed on the surface of the second electrode layer 14b. In this surface treatment step, part of molybdenum oxide is removed from the surface of the second electrode layer 14b in addition to oxygen. As the alkaline solution, a sodium tetraborate solution, an ammonium tetraborate solution, or an ammonia solution can be used. In particular, when a sodium-containing alkaline solution (for example, a sodium tetraborate solution) is used as the alkaline solution, a washing step for washing away sodium after that to improve photoelectric conversion efficiency (shown in parentheses in FIG. 2) It is preferable to have.

  The thickness of the layer 24 in which the density of Mo is sparse can be controlled to a thickness of one atomic level (0.1 nm) by appropriately changing the type, concentration, coating time, etc. of the alkaline solution.

  Thereafter, in step S4 (precursor forming step) in FIG. 2, as shown in FIG. 4A, an In layer is first formed by sputtering on the second electrode layer 14b, and then Cu—Ga is formed thereon. The alloy layer is formed by sputtering to form a laminated precursor 26 (precursor) composed of an In layer and a Cu—Ga alloy layer.

  Thereafter, in step S5 (selenization step) of FIG. 2, as shown in FIG. 4B, the laminated precursor 26 is heat-treated in a hydrogen selenide gas atmosphere, thereby making the laminated precursor 26 a light absorption layer (CIGS) by a CIGS thin film. The light absorption layer 16) is used. At this time, since the layer 24 having a low Mo density exists between the CIGS light absorption layer 16 and the second electrode layer 14b containing oxygen, the Mo density is low in this selenization step. Thus, Mo in the layer 24 is easily bonded to selenium, and a reaction layer 22 (MoSe layer) of Mo and selenium is formed between the CIGS light absorption layer 16 and the second electrode layer 14b. Since the second electrode layer 14b containing oxygen is present in the lower layer of the layer 24 where the density of Mo is sparse, the reaction of selenium stops at the surface portion of the second electrode layer 14b, or lower than that. The reaction of hardly occurs. As a result, an extremely thin reaction layer 22 (MoSe layer) is formed between the second electrode layer 14 b containing oxygen and the CIGS light absorption layer 16.

  Thereafter, in step S6 (buffer layer forming step) in FIG. 2, as shown in FIG. 1, a buffer layer 18 made of, for example, InS or the like is formed on the CIGS light absorption layer 16 by a solution growth method.

  Thereafter, in step S7 (transparent electrode forming step) in FIG. 2, a transparent electrode layer 20 made of, for example, ZnO: Al is formed on the buffer layer 18 by sputtering as shown in FIG. The solar cell 10 according to the embodiment is completed.

  Thus, in the solar cell 10 and the manufacturing method thereof according to the present embodiment, the interface layer (reaction layer 22) that contributes to the improvement of characteristics such as the open-circuit voltage characteristics of the chalcopyrite solar cell is uniformly formed. The film can be formed with an appropriate film thickness, and the photoelectric conversion efficiency can be improved while simultaneously suppressing the resistance increase of the back electrode and the interface peeling with the CIGS light absorption layer 16.

  Here, various experimental examples (first experimental example to fourth experimental example) will be described with reference to FIGS. 5A to 11.

  The first experimental example looks at the difference in conversion efficiency between Reference Example 1 and Reference Example 2.

  5A, the reference example 1 has a configuration in which a glass substrate 100, a single back electrode layer 102, a CIGS light absorption layer 104, a buffer layer 106, and a transparent electrode layer 108 are stacked. . In Reference Example 2, as shown in FIG. 5B, a glass substrate 100, a single back electrode layer 102, an oxide film 110, a CIGS light absorption layer 104, a buffer layer 106, and a transparent electrode layer 108 are laminated. It has the structure made. The oxide film 110 is obtained by forcibly oxidizing the surface of the lower back electrode layer 102, and thereafter, surface etching with an alkaline solution is not performed.

  The conversion efficiency measurement results of Reference Example 1 and Reference Example 2 are shown in FIG. The measurement results are displayed by connecting the upper limit (best value) and the lower limit (worst value) with a vertical line, taking into account the variation of each sample. It should be noted that the extremely bad data is not shown in FIG. 6 because it seems that there is a cause in the measuring device, the measurement state, etc. (the same applies hereinafter).

  6 that the reference example 2 in which the oxide film 110 is present is worse than the reference example 1 in which the oxide film 110 is not present. This is because the open circuit voltage and the fill factor are lowered due to the presence of the oxide film 110, and as a result, the conversion efficiency is lowered. Thus, the characteristics cannot be improved by simply oxidizing the surface of the back electrode layer 102.

  Next, the second experimental example looks at the difference in conversion efficiency between Example 1 and Comparative Example 1.

  Example 1 was produced using the manufacturing method according to the present embodiment. In particular, in step S3 (surface treatment step) shown in FIG. 2, a sodium tetraborate solution containing oxygen was used. The surface of the two-electrode layer 14a is etched (reduced). In Comparative Example 1, the surface treatment step described above is omitted.

  The measurement results of the conversion efficiency of Example 1 and Comparative Example 1 are shown in FIG. From FIG. 7, the conversion efficiency is improved in Example 1 in which the surface treatment was performed with the sodium tetraborate solution, compared with Comparative Example 1 in which the surface treatment was omitted. This is because the open circuit voltage and the fill factor are improved by performing the surface treatment, and as a result, the conversion efficiency is improved. Thus, it can be seen that the characteristics can be improved by oxidizing the surface of the back electrode layer 14 and then performing surface treatment (reduction treatment) with an alkaline solution.

  Next, the third experimental example looks at the difference in conversion efficiency between Examples 2 and 3.

  Examples 2 and 3 were both produced using the manufacturing method according to the present embodiment. In step S3 (surface treatment step) shown in FIG. 2, a sodium tetraborate solution (pH = 12. In 8), the surface of the second electrode layer 14b containing oxygen is etched (reduced). In particular, Example 2 was cleaned for 60 seconds using pure water in the cleaning step after the surface treatment step. Pure water was circulated. In Example 3, the cleaning step was omitted.

  The measurement results of the conversion efficiencies of Example 2 and Example 3 are shown in FIG. FIG. 8 shows that the conversion efficiency is improved in Example 2 in which the cleaning treatment is performed after the surface treatment with the sodium tetraborate solution, compared to Example 3 in which the cleaning treatment is not performed. Therefore, when a sodium-containing alkaline solution is used as the alkaline solution, it is preferable to have a washing step of washing away sodium after the surface treatment step in order to improve conversion efficiency.

  Next, the fourth experimental example looks at the difference in conversion efficiency for Examples 4 to 6.

  Each of Examples 4 to 6 was manufactured using the manufacturing method according to the present embodiment. Example 4 has a volume molarity of 0 in step S3 (surface treatment step) shown in FIG. The surface of the second electrode layer 14b containing oxygen is etched (reduced) with a 0.02 M (mol / liter) sodium tetraborate solution. In the surface treatment step, Example 5 is obtained by etching (reducing treatment) the surface of the second electrode layer 14b containing oxygen with an ammonium tetraborate solution having a volume molarity of 0.014M. In the surface treatment step, the surface of the second electrode layer 14b containing oxygen is etched (reduced) with an ammonium tetraborate solution having a volume molarity of 0.007M.

  The measurement results of the conversion efficiencies of Examples 4 to 6 are shown in FIG. From FIG. 9, by using an ammonium tetraborate solution as the alkaline solution, a result equal to or exceeding that obtained when using a sodium tetraborate solution was obtained. Moreover, even when the volume molar concentration of the ammonium tetraborate solution is 0.014M or 0.007M, almost the same result is obtained, and it can be seen that the effect is obtained even if the concentration is reduced. In particular, when an ammonium tetraborate solution is used, it is not necessary to go through a washing step, unlike a sodium tetraborate solution, so that simplification of the manufacturing process can be promoted.

  Next, the fifth experimental example looks at the difference in conversion efficiency between Examples 7 and 8.

  Examples 7 and 8 are both produced using the manufacturing method according to the present embodiment. Example 7 has a volume molarity of 0 in step S3 (surface treatment step) shown in FIG. The surface of the second electrode layer 14b containing oxygen is etched (reduced) with a 0.02 M (mol / liter) sodium tetraborate solution. In Example 8, in the surface treatment process, the surface of the second electrode layer 14b containing oxygen was etched (reduced) with an ammonia solution having a volume molarity of 7.5M.

  The measurement results of the conversion efficiencies of Examples 7 and 8 are shown in FIG. From FIG. 10, by using an ammonia solution as an alkaline solution, a result equal to or exceeding that obtained when a sodium tetraborate solution was used was obtained.

  Next, the sixth experimental example looks at the difference in conversion efficiency for Examples 9 to 13.

  Each of Examples 9 to 13 was manufactured using the manufacturing method according to the present embodiment. After the first electrode layer 14a was formed by sputtering, air was intentionally supplied to the sputtering chamber. The second electrode layer 14b containing oxygen is formed by introducing and changing the degree of vacuum. In step S3 (surface treatment step) shown in FIG. 2, the surface of the second electrode layer 14b containing oxygen is etched (reduction treatment) with a sodium tetraborate solution having a volume molar concentration of 0.02 M (mol / liter). )did.

In Example 9, the second electrode layer 14b containing oxygen was formed at an ultimate vacuum of 1.0 × 10 ⁻⁵ (Pa). In Example 10, the ultimate vacuum was 1.0 × 10 ^-4 (Pa) to form a second electrode layer 14b containing oxygen. In Example 11, the second electrode layer 14b containing oxygen was set to an ultimate vacuum of 1.0 × 10 ^-3 (Pa). In Example 12, the second electrode layer 14b containing oxygen was formed with an ultimate vacuum of 1.0 × 10 ⁻² (Pa), and in Example 13, the ultimate vacuum was 5.0. The second electrode layer 14b containing oxygen was formed to × 10 ⁻² (Pa).

The measurement results of the conversion efficiencies of Examples 9 to 13 are shown in FIG. From FIG. 11, all exceed the conversion efficiency of Comparative Example 1 in FIG. 7, and the ultimate vacuum is oxygen in the range of 1.0 × 10 ⁻⁵ (Pa) to 5.0 × 10 ⁻² (Pa). It can be seen that the second electrode layer 14b containing can be deposited.

  It should be noted that the solar cell and the method for manufacturing the solar cell according to the present invention are not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention.

It is sectional drawing which abbreviate | omits and shows the solar cell which concerns on this Embodiment. It is a process block diagram which shows the manufacturing method of the solar cell which concerns on this Embodiment. 3A is a process diagram showing a state in which a first electrode layer is formed on a glass substrate, and FIG. 3B is a process diagram showing a state in which a second electrode layer containing oxygen is formed on the first electrode layer. 3C is a process diagram showing a state in which the surface of the second electrode layer is subjected to surface etching (reduction treatment) with an alkaline solution. FIG. 4A is a process diagram showing a state in which a laminated precursor (a precursor of a CIGS light absorption layer) is formed on the second electrode layer, and FIG. 4B shows a state in which the laminated precursor is made into a CIGS light absorption layer by performing selenization. It is process drawing shown. FIG. 5A is a cross-sectional view showing Reference Example 1 (sample not subjected to forced oxidation) used in the first experimental example (experimental example in which the effect on the conversion efficiency due to the surface oxidation of the back electrode layer) was observed. It is sectional drawing which shows the reference example 2 (sample forcedly oxidized) used in the 1st experiment example. It is a graph which shows the measurement result of the 1st example of an experiment. It is a graph which shows the measurement result of the 2nd experiment example (experiment example which looked at the improvement of conversion efficiency at the time of carrying out the reduction process of the surface of the 2nd electrode layer containing oxygen). It is a graph which shows the measurement result of the 3rd experiment example (experiment example which looked at the improvement of the conversion efficiency by the washing process after reducing the surface of the 2nd electrode layer containing oxygen with the alkaline solution containing sodium). 4th experiment example (experimental example showing improvement in conversion efficiency when reducing surface of second electrode layer containing oxygen with sodium tetraborate solution and reducing treatment with ammonium tetraborate solution) It is a graph which shows a measurement result. The measurement results of the fifth experimental example (the experimental example in which the conversion efficiency when the surface of the second electrode layer containing oxygen is reduced with a sodium tetraborate solution and the reduction treatment with an ammonia solution) are shown. It is a graph to show. It is a graph which shows the measurement result of the 6th experiment example (experiment example which looked at the improvement of the conversion efficiency by the ultimate vacuum at the time of film-forming of the 2nd electrode layer containing oxygen in a sputtering chamber).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solar cell 12 ... Glass substrate 14 ... Back electrode layer 14a ... 1st electrode layer 14b ... 2nd electrode layer 16 containing oxygen ... CIGS light absorption layer 18 ... Buffer layer 20 ... Transparent electrode layer 22 ... Reaction layer (MoSe layer) )
24 ... Layer with a low density of Mo 26 ... Laminated precursor (precursor)

Claims (8)

A back electrode layer;
A CIGS light absorbing layer formed on the back electrode layer;
A transparent electrode formed on the CIGS light absorption layer via a buffer layer;
The back electrode layer has a first electrode layer and a second electrode layer containing oxygen formed on the first electrode layer,
Between the CIGS light absorption layer and the second electrode layer of the back electrode layer, a reaction layer of a metal constituting the second electrode layer and selenium constituting the CIGS light absorption layer is interposed ,
The metal constituting the second electrode layer of the back electrode layer is Mo (molybdenum),
The reaction layer, a solar cell characterized by MoSe Sodea Rukoto. The solar cell according to claim 1,
A metal constituting the first electrode layer of the back electrode layer, wherein the metal constituting the second electrode layer, a solar cell, which is a both Mo (molybdenum). A first electrode layer forming step of forming a first electrode layer on the substrate;
A second electrode layer forming step of forming a second electrode layer containing oxygen on the first electrode layer;
A surface treatment step of removing a part of the surface of the second electrode layer;
A precursor forming step of forming a CIGS light absorbing layer precursor on the second electrode layer;
The precursor was treated selenide to have a selenide step of the CIGS absorber layer,
The metal constituting the second electrode layer is Mo (molybdenum).
The surface treatment step removes oxygen from the surface of the second electrode layer with an alkaline solution,
By the selenization step, the precursor becomes the CIGS light absorption layer, and the metal constituting the second electrode layer and the CIGS light absorption layer are formed between the CIGS light absorption layer and the second electrode layer. method of manufacturing a solar cell characterized by Rukoto reaction layer is formed between the selenium to be. In the manufacturing method of the solar cell of Claim 3 ,
The metal constituting the first electrode layer and the metal constituting the second electrode layer are both Mo (molybdenum). In the manufacturing method of the solar cell of Claim 3 or 4 ,
The second electrode layer forming step includes
A method for manufacturing a solar cell, characterized in that the second electrode layer is formed by sputtering, using oxygen, water vapor, or air containing oxygen in a sputtering gas. In the manufacturing method of the solar cell of Claim 3 or 4 ,
The second electrode layer forming step includes
Using the sputter chamber used in the first electrode layer forming step, the second electrode layer is formed by performing sputtering under the condition that air or water vapor remaining in the sputter chamber is taken into Mo. A method for manufacturing a solar cell. In the manufacturing method of the solar cell of Claim 3 ,
The method for producing a solar cell, wherein the alkaline solution is a sodium tetraborate solution, an ammonium tetraborate solution, or an ammonia solution. In the manufacturing method of the solar cell of Claim 3 or 7 ,
As the alkaline solution, a sodium-containing alkaline solution is used,
A method of manufacturing a solar cell, comprising a washing step of washing away sodium after the surface treatment step.

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