WO2012117731A1 - Manufacturing method for photoelectric converter - Google Patents

Abstract

[Problem] To establish the processes carried out before and after buffer layer deposition in a photoelectric converter manufacturing method using a flexible substrate. [Solution] The surface of a photoelectric conversion semiconductor layer of a substrate (A) is immersed in a surface treatment solution (24), and after being surface treated the substrate (A) is rinsed, and then the water is removed. The substrate (A) is adhered to a drum (3) in a manner such that the photoelectric conversion semiconductor layer (30) forms the surface, and with the section in which the end of the substrate (A) and the substrate of the drum (3) are not adhered overlapped by a protection member (6) and protected from a CBD reaction solution (4), part of the substrate (A) is immersed in the CBD reaction solution (4) by immersing part of the drum (3) in the CBD reaction solution (4), a buffer layer (40) is deposited on the photoelectric conversion semiconductor layer (30), and then the substrate (A) is further rinsed and the rinsing solution is removed.

Description

Method for manufacturing photoelectric conversion element

The present invention relates to a method for producing a compound semiconductor photoelectric conversion element.

A photoelectric conversion element including a photoelectric conversion layer and an electrode connected to the photoelectric conversion layer is used for applications such as solar cells. Conventionally, in the case of solar cells, Si-based solar cells using bulk single crystal Si or polycrystalline Si, or thin-film amorphous Si have been mainstream, but research and development of Si-independent compound semiconductor solar cells has been made. ing. Known compound semiconductor solar cells include bulk systems such as GaAs systems and thin film systems such as CIS or CIGS systems composed of group Ib elements, group IIIb elements, and group VIb elements. CI (G) S is represented by the general formula Cu _1-z In _1-x Ga _x Se _2-y S _y (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1). When x = 0, it is a CIS system, and when x> 0, it is a CIGS system. Hereinafter, CIS and CIGS are collectively referred to as “CI (G) S”.

In conventional thin-film photoelectric conversion elements such as CI (G) S, a CdS buffer layer and an environmental load are generally placed between a photoelectric conversion layer and a translucent conductive layer (transparent electrode) formed thereon. In consideration, a ZnS buffer layer not containing Cd is provided. The buffer layer plays a role such as (1) prevention of recombination of photogenerated carriers, (2) band discontinuous matching, (3) lattice matching, and (4) coverage of the surface irregularities of the photoelectric conversion layer. In the case of CI (G) S, etc., the surface irregularity of the photoelectric conversion layer is relatively large, and the film formation by the CBD (Chemical Bath Deposition) method, which is a liquid phase method, is particularly necessary because the condition (4) above must be satisfied satisfactorily. Is preferred.

Patent Documents 1 to 4 propose a process for forming a buffer layer using a CBD method. Patent Documents 1 to 3 disclose a so-called batch type (single-wafer type) film forming method in which an inflexible substrate such as a glass substrate is immersed in a reaction solution containing a raw material compound for a buffer layer. On the other hand, Patent Document 4 discloses a so-called roll-to-roll (Roll) roll that uses a supply roll obtained by winding a flexible substrate in a roll shape and a take-up roll for winding a film-formed substrate in a roll shape. A manufacturing apparatus for realizing a film formation method of “to Roll” method has been proposed.

International Publication 2008/120306 Pamphlet Japanese Patent No. 4549570 Special table 2008-510310 JP 2003-124487 A

Appropriate time is required to form a buffer layer having a predetermined thickness by the CBD method, and the film formation process of the buffer layer is one of the rate-determining processes in the entire process, so that productivity improvement is required. ing.

From the viewpoint of improving productivity, a roll-to-roll film forming method is preferable.
However, the manufacturing apparatus described in Patent Document 4 is configured so that the substrate is immersed in the CBD reaction solution with the front and back surfaces thereof exposed, and is transported through the reaction solution, and is dissolved in the CBD reaction solution. In the case of a substrate including such a portion (including a case where a soluble component such as a substrate end surface or a substrate back surface is exposed), the CBD is continuously applied after protecting the end surface or back surface of the substrate. The law cannot be enforced.

Also, it cannot be said that the manufacturing process before and after the buffer layer forming step in the method for manufacturing a photoelectric conversion element using a flexible substrate has been sufficiently established.

The present invention has been made in view of the above circumstances, and includes a step of forming a buffer layer without dissolving the substrate, and a step before and after the buffer layer, even if the substrate includes a portion that dissolves in the CBD reaction solution. An object of the present invention is to provide a method for manufacturing a photoelectric conversion element that can realize high productivity.

The method for producing a photoelectric conversion element of the present invention includes a laminated structure of a buffer layer and a light-transmitting conductive layer on the photoelectric conversion semiconductor layer of a flexible substrate including a lower electrode and a photoelectric conversion semiconductor layer. In the manufacturing method of the photoelectric conversion element having
A surface treatment step of immersing the photoelectric conversion semiconductor layer surface in a surface treatment liquid;
A post-surface treatment water washing step of washing the substrate that has been surface-treated in the surface treatment liquid with water;
A post-surface treatment water removal step for removing water adhering to the substrate in the post-surface treatment water washing step;
Of the drum that closely supports the substrate, a reaction tank filled with a CBD reaction solution that immerses a part of the drum that closely supports the substrate, the end of the substrate that is closely supported by the drum, and the drum Using a CBD film forming apparatus having a protective member that protects the CBD reaction liquid by overlapping a portion where the substrate does not adhere, and a portion of the end of the substrate and the drum that does not adhere to the drum by the protective member A part of the drum that tightly supports the substrate on which the substrate is overlapped is immersed in the CBD reaction solution in the reaction tank, so that a part of the substrate is immersed in the CBD reaction solution, and a predetermined film formation is performed. A CBD step of forming a buffer layer on the photoelectric conversion semiconductor layer in the CBD reaction solution adjusted to a temperature;
A post-CBD cleaning step of immersing and cleaning the substrate after the buffer layer is formed; and
A post-CBD cleaning liquid removing step of removing the cleaning liquid adhering to the substrate in the post-CBD cleaning step;
The above steps are performed in this order.

In the method for producing a photoelectric conversion element of the present invention, it is preferable to perform heat treatment for heat-treating the substrate at 150 ° C. or more and 250 ° C. or less after the post-CBD drying step.

Furthermore, it is preferable that the substrate is heated to a temperature equal to or higher than the predetermined film formation temperature in the CBD step before the CBD step.

Here, as a method of heating the substrate, the substrate is heated directly by the heater, or the surface treatment solution used in the surface treatment step, the water used in the post-surface treatment water washing step, and the heated solution. A method using indirect heating by immersing the substrate in the substrate can be applied.

Examples of the substrate include an anodized substrate in which an anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface side of an Al base material mainly composed of Al, and an Fe material mainly composed of Fe. An anodized substrate in which an anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface of a composite base material in which an Al material mainly composed of Al is composited on at least one surface; and Fe An anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface side of a base material on which an Al film composed mainly of Al is formed on at least one surface side of an Fe material containing bismuth as a main component It is preferable to use a substrate provided with any one of the anodized substrates.

As the CBD reaction solution,
In a mixed solution at room temperature in which water is mixed with component (Z) that is at least one zinc source, component (S) that is at least one sulfur source, component (C) that is at least one citric acid compound In addition, at least one component (N) selected from the group consisting of ammonia and ammonium salts is mixed at room temperature,
The concentration of the component (C) is 0.001 to 0.25M;
The concentration of the component (N) is 0.001 to 0.40 M;
It is preferable to use a CBD reaction solution having a pH of 9.0 to 12.0 before the start of the reaction.

In the CBD step, after the substrate is immersed in the CBD reaction solution adjusted to the film formation temperature of 70 to 95 ° C., Zn (S, O) and / or Zn (S, O) is formed at the film formation temperature. , OH) as a main component, a Zn compound layer is preferably formed as the buffer layer.

The surface treatment liquid is preferably an aqueous solution containing a compound having a cyano group or an amino group.

As the compound having a cyano group, potassium cyanide is preferable.

The compound having an amino group is preferably at least one selected from ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

In the method for producing a photoelectric conversion element of the present invention, the back surface of the substrate is brought into close contact with the drum, and the end portion of the substrate and the portion of the drum where the substrate does not adhere are overlapped by a protective member and protected from the CBD reaction liquid. Since the substrate is immersed in the CBD reaction solution, even if the substrate contains a component that dissolves in the CBD reaction solution, a buffer film is formed by the CBD method without eluting such a component from the substrate. Is possible.

According to the method for manufacturing a photoelectric conversion element of the present invention, a process before and after the formation of a buffer layer is clearly established from the surface treatment of the photoelectric conversion semiconductor layer to the cleaning after the formation of the buffer layer and the cleaning liquid removal treatment, and high photoelectric conversion is achieved. An efficient photoelectric conversion element can be manufactured with high productivity.

It is a schematic sectional drawing which shows the layer structure of the photoelectric conversion element produced with the manufacturing method of this invention. It is a schematic perspective view which shows the CBD film-forming apparatus used with the manufacturing method of this invention. It is a schematic sectional drawing of the CBD film-forming apparatus shown in FIG. It is a schematic sectional drawing which shows one Embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows another embodiment of the protection member which protects a board | substrate. It is a schematic sectional drawing which shows schematic structure of the manufacturing apparatus for enforcing the manufacturing method of this invention.

Hereinafter, the manufacturing method of the photoelectric conversion element of this invention is demonstrated with reference to drawings.
FIG. 1 is a schematic cross-sectional view showing a layer structure of a photoelectric conversion element manufactured by the manufacturing method of the present invention. In FIG. 1, only one photoelectric conversion element (cell) of an integrated solar cell is shown to show the layer structure of the photoelectric conversion element, but the manufacturing method of the present invention is an integration with a large number of photoelectric conversion elements. It is suitable for manufacturing a solar cell.

As shown in FIG. 1, the photoelectric conversion element 101 includes a lower electrode 20, a photoelectric conversion semiconductor layer 30 that generates hole / electron pairs by light absorption, a buffer layer 40, and a window layer 50 on a substrate 10. A light-transmissive conductive layer (transparent electrode) 60 and an upper electrode (grid electrode) 70 are sequentially stacked.

First, an embodiment of a CBD film forming apparatus used in the photoelectric conversion element of the present invention will be described. 2 is a schematic perspective view showing the CBD film forming apparatus, and FIG. 3 is a schematic cross-sectional view of the CBD film forming apparatus shown in FIG. In FIG. 2, the reaction vessel is illustrated as being transparent. The CBD film forming apparatus 1 shown in FIGS. 2 and 3 includes a drum 3 that closely supports a long flexible substrate A, and a CBD reaction solution 4 that immerses a part of the drum 3 that closely supports the substrate A. Protection that protects from the CBD reaction liquid 4 by overlapping the reaction tank 5 filled with 1, the short-side end of the substrate A that is closely supported by the drum 3, and the portion of the drum 3 where the substrate A does not adhere The member 6 is provided with a drive unit (not shown) for causing the substrate A, which is brought into close contact with the drum 3 in accordance with the peripheral speed of the drum 3, and the protective member 6 to co-run in the CBD reaction solution 4.

Further, an unwinding roll 11 for winding the substrate A in a roll shape on the upstream side of the drum 3, and the substrate A after the CBD thin film is formed on one side of the substrate A fed from the drum 3 on the downstream side. A take-up roll 12 is provided, and feed rolls 13 and 14 are provided between the take-up roll 11 and the drum 3, and between the take-up roll 12 and the drum 3, respectively. Further, a winding roll 15 for winding the protective member 6 in a roll shape is provided between the drum 3 and the feed roll 13, and a winding for winding the protective member 6 between the drum 3 and the feed roll 14. Each roll 16 is provided. The protective member 6 fed from the unwinding roll 15 can overlap the short-side end portion of the substrate A and the portion of the drum 3 where the substrate A does not adhere. Each of the winding rolls 12 and 16 is provided with a drive unit (not shown), and the substrate A and the protective member 6 which are brought into close contact with the drum 3 in accordance with the peripheral speed of the drum 3 (synchronized) are subjected to a CBD reaction. It can be made to co-run in the liquid 4.

Here, the drive units provided on the take-up rolls 12 and 16 drive the take-up rolls 12 and 16, respectively, and the substrate A and the protective member 6 after the CBD thin film is formed on the take-up rolls 12 and 16, respectively. Although the winding mode is described, the winding rolls 12 and 16 are simply rotatable and have a function of feeding out the substrate A and the protective member 6, and are controlled by separate driving units downstream thereof. The structure by which the wound winding roll was arrange | positioned may be sufficient. Further, the drum 3 itself is simply rotatable, and the drum 3 is transported in a state where only one surface of the substrate A is immersed in the CBD reaction solution 4 by driving the driving unit described above. However, the drum 3 may be provided with a drive source and rotate itself.

FIG. 4 is a schematic sectional view showing an embodiment of a protective member for protecting the substrate. As shown in FIG. 4, the protection member 6 can overlap the short-side end portion of the long substrate A and the portion of the drum 3 where the substrate A does not adhere. By overlapping in this way, the CBD reaction solution 4 does not enter and contact the back surface (side in close contact with the drum 3) and the end surface of the substrate A, and the substrate A is temporarily dissolved in the CBD reaction solution. Even if a component containing such a component is included, a CBD thin film can be formed without eluting such a component from the substrate A.

The protective member 6 is preferably made of a material such as Viton rubber or silicon rubber in order to ensure adhesion to the substrate A. Alternatively, even if the entire protective member 6 is not made of such a material, a mode in which a material having adhesiveness is applied to at least the side in close contact with the substrate A may be adopted.

In order to further improve the watertightness of the protective member 6 that overlaps the substrate A, it is preferable that the drum 3 is configured to be able to closely support the substrate A on the drum 3 by magnetism. For example, if a permanent magnet, which itself has the property of a magnet and can attract a magnetic material such as iron, is disposed inside the drum 3 at a portion where the substrate A is in close contact, the substrate A may be a magnetic material. In this case, the substrate A can be tightly supported on the drum 3 by magnetism.

Further, even when the substrate A is not a magnetic material, as shown in FIG. 5, a metal plate 7 (magnetic metal plate such as SUS316) that is a magnetic material is further overlapped on the protective member 6. In the same manner, the substrate A can be magnetically closely supported on the drum 3 (in FIG. 5, the same components as those in FIG. 4 are given the same reference numerals, and description thereof will be omitted unless particularly required). (Hereinafter, the same applies to other drawings). In this case, the metal plate 7 may be fixed by a holding spring 8 as shown in FIG. In addition, although this presser spring 8 is provided in multiple places over the perimeter of the drum 3, in the part in which the drum 3 is immersed in the reaction liquid, as shown in the upper figure of FIG. After being pressed from above and separated from the reaction solution, control is performed so as to leave the metal plate 7 as shown in the lower diagram of FIG.

Furthermore, as another aspect, as shown in FIG. 7, a pressure drum 9 that presses the protective member 6 against the drum 3 may be provided. It is preferable that a plurality of the pressure drums 9 are provided at the opposing portions of the drum 3 immersed in the reaction solution.

It is preferable that the drum 3 includes a heating unit that heats the substrate A that is closely supported from the back surface. Normally, the CBD reaction solution is heated to perform the reaction, but by heating the substrate A from the back surface, film formation with less variation in film thickness can be performed. At this time, it is preferable that the temperature of the substrate is equal to or higher than the temperature of the CBD reaction solution. By keeping the temperature of the substrate equal to or higher than the temperature of the CBD reaction solution, it is possible to preferentially advance the deposition on the substrate. In addition, if precipitation on the substrate proceeds even if the temperature of the reaction solution is lowered at that time, the generation of colloidal solids in the reaction solution will be suppressed. It can be used continuously. Preferred examples of the heating means include a mode in which a heater is provided in the drum 3 and a mode in which a medium (for example, water or oil) heated in the drum is circulated.

In the above, the substrate A is protected by the protective member 6 unwound from the unwinding roll 15 before being immersed in the reaction liquid 4, and the protective member 6 is unwound by the take-up roll 16 after being detached from the reaction liquid 4. Although the mode to be taken has been described as an example, the protective member 6 may be provided in advance on the long substrate A wound around the unwinding roll 11 in a roll shape. For example, as shown in FIGS. 8 and 9, the protective member 6 may protect the end of the long substrate A in the short direction from both sides. In this case, in order to ensure watertightness between the substrate A and the protective member 6 to be overlapped, the portion of the drum 3 where the substrate A is in close contact is formed as a convex portion as shown in FIG. 8, or as shown in FIG. As described above, a portion where the substrate A is in close contact may be formed as a convex portion, and a concave portion may be provided in advance in a part of the drum 3 on which the protective member 6 travels so as not to meander the substrate A.

Further, a plurality of protective members 6 as shown in FIG. 10 may be provided over the entire length of the substrate A from the beginning on the long substrate A wound around the unwinding roll 11 in a roll shape. In addition, in the figure, in order to make it easy to visually recognize the arrangement of the protective member 6, a state where one protective member 6 is arranged is shown. In this case, L ₁ <the width of the long substrate <L ₂ and L ₂ ≦ the width of the drum. In this case, L ₃ of the protection member 6 is preferably set to a length equal to or less than the circumference in the drum rotation direction.

In the method for producing a photoelectric conversion element of the present invention, a flexible substrate A comprising the lower electrode 20 and the photoelectric conversion semiconductor layer 30 after the lower electrode 20 and the photoelectric conversion semiconductor layer 30 are sequentially formed on the substrate 10. The surface of the photoelectric conversion semiconductor layer 30 is immersed in a surface treatment solution (surface treatment step), and the substrate A subjected to the surface treatment in the surface treatment solution is washed with water (water treatment step after surface treatment) and after the surface treatment. The water adhering to the substrate A is removed in the water washing step (water removal step after the surface treatment), and the substrate A is not in close contact with the end portion of the substrate A and the drum 3 by the protective member 6 using the CBD film forming apparatus 1 described above. A part of the drum 3 that closely supports and supports the overlapping substrate A is immersed in the CBD reaction solution 4 in the reaction tank 5, so that a part of the substrate A is immersed in the CBD reaction solution 4 to obtain a predetermined composition. CBD temperature controlled to membrane temperature The buffer layer 40 is formed on the photoelectric conversion semiconductor layer 30 in the reaction solution 4 (CBD process), and the substrate A after the buffer layer 40 is formed is immersed in the cleaning liquid and cleaned (post-CBD cleaning process). The cleaning liquid adhering to the substrate A is removed (post-CBD cleaning liquid removing step).

The substrate used in the manufacturing method of the present invention and each manufacturing process will be described in order.

(substrate)
The flexible substrate A used in the manufacturing method of the present invention is a flexible substrate in which the lower electrode 20 and the photoelectric conversion semiconductor layer 30 are formed in advance on the substrate 10.

Although there will be no restriction | limiting in particular if the board | substrate 10 has flexibility, In the CBD film-forming apparatus used with the manufacturing method of this invention, the board | substrate contains the component which melt | dissolves in a CBD reaction liquid. However, since there is an effect that such a component is not eluted from the substrate, when a substrate containing a metal, a metal oxide, a metal hydroxide or the like capable of forming a complex ion with a hydroxide ion is used. This effect can be obtained, and more specifically, it can be effectively applied to a substrate containing Al.

Specifically, the substrate 10 is an anodized substrate in which an anodized film containing Al ₂ O ₃ as a main component is formed on at least one surface side of an Al base material containing Al as a main component, and Fe as a main component. Anodization in which an anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface side of a composite base material in which an Al material composed mainly of Al is formed on at least one surface side of the Fe material Al ₂ O ₃ is the main component on at least one surface side of the substrate and the base material on which an Al film having an Al main component is formed on at least one surface side of the Fe material containing Fe as the main component It is preferable that any one of the anodized substrates on which the anodized film is formed.

The main component of the photoelectric conversion semiconductor layer 30 is not particularly limited and is preferably a compound semiconductor having at least one chalcopyrite structure because high conversion efficiency is obtained. The Ib group element, the IIIb group element, and the VIb group More preferably, it is at least one compound semiconductor composed of an element.

As a main component of the photoelectric conversion semiconductor layer 30,
At least one group Ib element selected from the group consisting of Cu and Ag;
At least one group IIIb element selected from the group consisting of Al, Ga and In;
It is preferably at least one compound semiconductor comprising at least one VIb group element selected from the group consisting of S, Se, and Te.

As the compound semiconductor,
CuAlS ₂ , CuGaS ₂ , CuInS ₂ ,
CuAlSe ₂ , CuGaSe ₂ ,
AgAlS ₂ , AgGaS ₂ , AgInS ₂ ,
AgAlSe ₂ , AgGaSe ₂ , AgInSe ₂ ,
AgAlTe ₂ , AgGaTe ₂ , AgInTe ₂ ,
Cu (In, Al) Se ₂ , Cu (In, Ga) (S, Se) ₂ ,
Cu _1-z In _1-x Ga _x Se _2-y S _y (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1) (CI (G) S),
Examples include Ag (In, Ga) Se ₂ and Ag (In, Ga) (S, Se) ₂ .
_{Further, Cu 2 ZnSnS 4, Cu 2} ZnSnSe 4, Cu 2 ZnSn (S, Se) may be a _four.
The film thickness of the photoelectric conversion semiconductor layer is not particularly limited, and is preferably 1.0 μm to 4.0 μm, particularly preferably 1.5 μm to 3.5 μm.

(Surface treatment process)
At least the surface of the photoelectric conversion semiconductor layer 30 of the substrate A is immersed in the surface treatment liquid 24, and surface treatment such as impurity removal by the surface treatment liquid is performed on the surface of the photoelectric conversion semiconductor layer 30.

As the surface treatment liquid, for example, an ammonia-containing aqueous solution, a compound-containing aqueous solution having a cyano group or an amino group can be used.

As the compound having a cyano group contained in the surface treatment liquid, potassium cyanide (KCN) is preferable. On the other hand, since KCN is a lethal compound and has a safety problem, it is more preferable to use a compound having an amino group.

The compound having an amino group contained in the surface treatment liquid is preferably a compound having at least two amino groups in one molecule (hereinafter also simply referred to as an amino group-containing compound). Specifically, ethylenediamine (EDA ), Diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), or pentaethylenehexamine (PEHA), and these may be used alone, Two or more types may be appropriately mixed and used.

These amino group-containing compounds are contained in the surface treatment solution in an amount of 1 to 30% by mass, preferably 5 to 25% by mass, and more preferably 10 to 20% by mass.
Hydrogen peroxide is preferably contained in the surface treatment solution in an amount of 0.01% by mass to 10% by mass, preferably 0.05% by mass to 8% by mass, and more preferably 0.1% by mass to 5% by mass.
The surface treatment liquid can be prepared by dissolving the amino group-containing compound and hydrogen peroxide in water.

The time for bringing the photoelectric conversion semiconductor layer into contact with the surface treatment liquid depends on the concentration of the surface treatment liquid, but is preferably about several seconds to several tens of minutes.

There is a high possibility that impurities such as copper selenide and copper sulfide remain on the surface of the photoelectric conversion semiconductor layer 30 after film formation in the case of a CI (G) S-based photoelectric conversion semiconductor layer. However, by performing the surface treatment (impurity removal) of the photoelectric conversion semiconductor layer 30 as described above, the in-plane variation of the photoelectric conversion efficiency of the photoelectric conversion element can be reduced and the conversion efficiency can be increased.

In addition, it is preferable to form the buffer layer within 60 minutes after this surface treatment, and it is more preferable to form the buffer layer within 10 minutes. Here, “within 60 minutes after the surface treatment” means a time immediately after the completion of the surface treatment, and it is preferable to start the CBD step within 60 minutes including the water washing step and the drying step after the surface treatment.

(Water washing process after surface treatment)
After the surface treatment process, the substrate A is washed with water. The temperature of water is preferably 20 ° C. or higher. Here, the water washing method may be a method of immersing in a water tank and washing with water or shower washing. As washing water, pure water, ion exchange water, industrial water, or the like can be used.

(Water removal process after surface treatment)
After rinsing with water, if the substrate is immersed in the reaction solution of the CBD process while water is attached to the substrate, the concentration of the reaction solution decreases. Therefore, the water is removed to the extent that the concentration of the reaction solution does not decrease before the CBD process. Specifically, the water adhering to the substrate A is removed by blowing dry air or nitrogen on the front and back surfaces of the substrate. At this time, warm air may be blown.

In the CBD process, which is the next process, the film forming temperature (deposition temperature) of the constituent material of the buffer layer described later is preferably 70 ° C. or higher. For this reason, in the CBD process, when the substrate is immersed in the CBD reaction liquid that has been temperature-controlled in advance, the substrate A is immersed before the substrate A is immersed in the reaction tank 5 filled with the CBD reaction liquid 4. It is preferable to warm A to a temperature equal to or higher than the film formation temperature. By preheating (preheating) the substrate, when immersed in the CBD reaction solution, it is possible to suppress the temperature drop of the reaction solution adjusted to the film formation temperature of the buffer layer, and time loss in the manufacturing process Can be reduced.

The preheating of the substrate may be further provided with a preheating step in addition to the above steps and heated by a heater or the like. For example, the surface treatment step, the post-surface treatment water washing step, and the post-surface treatment water are performed as follows. It is preferable to carry out simultaneously in the removal step or the like.

In the surface treatment step, the ammonia-containing aqueous solution or the amine compound-containing aqueous solution used as the surface treatment liquid is heated, and the substrate is preheated simultaneously with the surface treatment by immersing the substrate in the heated aqueous solution.
In the water washing step after the surface treatment, the substrate can be preheated simultaneously with the water washing by heating the water and immersing the substrate in the heated water.
In the post-surface treatment water removal step, preheating with a heater may be performed.

In the surface treatment process, the water washing process, and the water removal process, the temperature may be set gradually higher so that the temperature is equal to or higher than the film formation temperature immediately before the CBD process. It may be made to become. Moreover, you may perform a heating only after a water washing process, or in a water removal process. In any case, in the CBD process, the substrate temperature is preferably equal to or higher than the film formation temperature immediately before being immersed in the CBD reaction solution.

(CBD process)
After the surface treatment of the photoelectric conversion semiconductor layer, a buffer layer is formed on the photoelectric conversion semiconductor layer of the substrate that has been washed and removed with water. Here, the buffer layer 40 is formed on the photoelectric conversion semiconductor layer 30 in the reaction vessel 5 of the CBD film forming apparatus 1.

The operation of the CBD film forming apparatus 1 will be described with reference to FIGS. When the substrate A is closely supported by the drum 3, the protective member 6 wound in a roll shape is simultaneously fed from the unwinding roll 15, and the short-side end of the substrate A that is closely supported by the drum 3, and the drum 3 are overlapped so that the protective member 6 can prevent the CBD reaction liquid 4 from contacting the back surface and the end surface of the substrate A. A part of the drum 3, for example, the center of the drum 3 is immersed in the CBD reaction solution 4 in the reaction tank 5. At this time, the liquid level of the CBD reaction liquid 4 in the reaction tank 5 is at a position lower than the position where the substrate A and the protective member 6 that overlaps the substrate A start to contact.

Here, the driving unit of the CBD device 1 is driven, and the substrate A and the protective member 6 that are in close contact with the drum 3 in synchronism with the peripheral speed of the drum 3 are caused to co-run in the CBD reaction solution 4, so A buffer layer is formed on one surface that is not in close contact, that is, on the surface of the photoelectric conversion semiconductor layer. Since the reaction solution contacts only the photoelectric conversion semiconductor layer surface of the substrate A on which the buffer layer is deposited, even if the substrate contains a component that dissolves in the CBD reaction solution, such a component is eluted from the substrate. It is possible to form the buffer layer without causing it. Further, since the CBD reaction solution 4 does not enter the back surface of the substrate A (the side in close contact with the drum 3), it is possible to suppress the formation of a buffer layer on the back surface of the substrate A.

Next, details of the CBD method will be described. The CBD method uses a general formula [M (L) _i ] ^{m +} ⇔M ^{n +} + iL (where M is a metal element such as Cd, Zn, In, Sn, L is a ligand, m, n, i: positive number By using as a reaction solution a metal ion solution having a concentration and a pH that are in a supersaturated condition due to an equilibrium as represented by the following formula, a complex of metal ions M is formed at an appropriate rate in a stable environment. In this method, a metal compound thin film is deposited on a substrate.

Examples of the CBD reaction liquid include those containing a metal (M) source such as Cd or Zn and a sulfur source. Thereby, a buffer layer of CdS, ZnS, Zn (S, O), Zn (S, O, OH) can be formed. As the sulfur source, a compound containing sulfur, for example, thiourea (CS (NH ₂ ) ₂ ), thioacetamide (C ₂ H ₅ NS), thiosemicarbazide, thiourethane, diethylamine, triethanolamine, etc. may be used. it can.

In the case of the CdS buffer layer, the sulfur source, a Cd compound (for example, cadmium sulfate, cadmium acetate, cadmium nitrate, cadmium chloride, and a hydrate thereof), ammonia water or ammonium salt (for example, CH ₃ COONH ₄ , A mixed solution of NH ₄ Cl, NH ₄ I and (NH ₄ ) ₂ SO ₄ or the like) can be used as a reaction solution.

In such a method, the reaction temperature is preferably 70 to 95 ° C. The reaction time may be about 5 to 60 minutes. CdS is a suitable material for the buffer layer, but Cd is highly toxic and is not preferable in terms of environmental load. Accordingly, the buffer layer 40 is more preferably a Cd-free metal compound, for example, a Zn compound layer mainly composed of Zn (S, O) and / or Zn (S, O, OH).

When the buffer layer 40 is a Zn compound layer mainly composed of Zn (S, O) and / or Zn (S, O, OH), at least one component (Z) as a zinc source, at least one A component (S) that is a sulfur source of the component, a component (C) that is at least one citric acid compound, a component (N) that is at least one selected from the group consisting of ammonia and an ammonium salt, and water. And the concentration of the component (C) is 0.001 to 0.25M, the concentration of the component (N) is 0.001 to 0.40M, and the pH before starting the reaction is 9.0 to 12.0M. It is preferable to use a reaction solution that is

The component (Z) is not particularly limited, and preferably contains at least one selected from the group consisting of zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, zinc carbonate, and hydrates thereof.
The concentration of component (Z) is not particularly limited and is preferably 0.001 to 0.5M.

The component (S) is not particularly limited, and preferably contains thiourea.
The concentration of component (S) is not particularly limited and is preferably 0.01 to 1.0M.

Component (C) is a component that functions as a complex-forming agent and the like, and a complex is easily formed by optimizing the type and concentration of component (C).
By using component (C), which is at least one kind of citric acid compound, a complex is more easily formed than in a reaction solution that does not use a citric acid compound, crystal growth by the CBD reaction is well controlled, and the base is covered well. Thus, a stable film can be formed.

Component (C) is not particularly limited, and preferably contains sodium citrate and / or a hydrate thereof. The concentration of component (C) is 0.001 to 0.25M. If the concentration of the component (C) is within this range, the complex is formed satisfactorily, and a film that satisfactorily covers the base can be stably formed. When the concentration of component (C) exceeds 0.25M, a stable aqueous solution in which the complex is well formed is obtained, but on the other hand, the progress of the precipitation reaction on the substrate is slow or the reaction does not proceed at all. There is. The concentration of component (C) is preferably 0.001 to 0.1M.

Component (N) is a component that functions as a pH adjuster or the like, but is also a component that functions as a complexing agent or the like. The ammonium salt suitable for use as the component (N) is not particularly limited, and examples thereof include NH ₄ OH.
The concentration of component (N) is 0.001 to 0.40M. The solubility and supersaturation degree of metal ions can be adjusted by adjusting the pH with the component (N). If the concentration of component (N) is within the range of 0.001 to 0.40M, the reaction rate is fast, and film formation is carried out at a practical production rate without providing a fine particle layer formation step before the film formation step. can do. When the concentration of the component (N) exceeds 0.40 M, the reaction rate becomes slow, and it is necessary to devise such as adding a fine particle layer before the film forming step. The concentration of component (N) is preferably 0.01 to 0.30M.

The pH of the reaction solution before starting the reaction is 9.0 to 12.0.
When the pH of the reaction solution before the start of reaction is less than 9.0, the decomposition reaction of the component (S) such as thiourea does not proceed, or even if it proceeds, the precipitation reaction does not proceed. The decomposition reaction of thiourea is as follows. The decomposition reaction of thiourea is described in J. Electrochem. Soc., Vol. 141, No. 1, January 1994, and Journal of Crystal Growth 299 (2007) 136-141.
SC (NH ₂ ) ₂
+ OH ⁻ ⇔ SH ⁻ + CH ₂ N ₂ + H ₂ O,
SH ^-
+ OH ⁻ ⇔S ² + + H ₂ O.
When the pH of the reaction solution before the start of the reaction exceeds 12.0, the effect that the component (N) that also functions as a complexing agent or the like makes a stable solution increases, and the precipitation reaction does not proceed or proceeds. It will be very slow. The pH of the reaction solution before starting the reaction is preferably 9.5 to 11.5.

If the concentration of the component (N) is 0.001 to 0.40 M, the pH of the reaction solution before starting the reaction usually does not require special pH adjustment such as using a pH adjuster other than the component (N). Is in the range of 9.0 to 12.0.

The pH after completion of the reaction of the reaction solution is not particularly limited. The pH of the reaction solution after completion of the reaction is preferably 7.5 to 11.0. When the pH of the reaction solution after completion of the reaction is less than 7.5, it means that the reaction does not proceed, and it is meaningless when considering efficient production. In addition, if there is such a pH drop in a system containing ammonia that has a buffering effect, it is highly possible that ammonia has volatilized excessively in the heating process, and it is considered that manufacturing improvements are necessary. It is done. When the pH of the reaction solution after completion of the reaction is more than 11.0, the decomposition of thiourea is promoted, but since most of the zinc ions are stabilized as ammonium complexes, the progress of the precipitation reaction may be remarkably slowed. The pH of the reaction solution after completion of the reaction is more preferably 9.5 to 10.5.
In the above reaction solution, the pH of the reaction solution after the start of the reaction is usually in the range of 7.5 to 11.0 without special pH adjustment such as using a pH adjusting agent other than the component (N). .

The reaction temperature is 70 to 95 ° C. If the reaction temperature is less than 70 ° C., the reaction rate becomes slow, and the thin film does not grow, or even if the thin film is grown, it is difficult to obtain a desired thickness (for example, 50 nm or more) at a practical reaction rate. When the reaction temperature exceeds 95 ° C., generation of bubbles and the like increases in the reaction solution, which adheres to the film surface and makes it difficult to grow a flat and uniform film. Furthermore, when the reaction is carried out in an open system, a concentration change due to evaporation of the solvent or the like occurs, making it difficult to maintain stable thin film deposition conditions. The reaction temperature is preferably 80 to 90 ° C.

The reaction time is not particularly limited. Although the reaction time depends on the reaction temperature, for example, the base can be satisfactorily covered in 10 to 60 minutes, and a layer having a sufficient thickness as a buffer layer can be formed.

Moreover, the reaction solution is aqueous. The pH of the reaction solution is not a strong acid condition. The pH of the reaction solution may be 11.0 to 12.0, but the reaction can be carried out under mild pH conditions of less than 11.0. The reaction temperature is not so high. Therefore, the environmental load is small and the damage to the substrate can be kept small.

(Cleaning process after CBD)
When the buffer layer 40 is formed, colloidal solid matter may adhere to the surface of the buffer layer 40. If this colloidal solid is left as it is, it may not be possible to maintain high resistance at the buffer layer coating and improve the conversion efficiency of the solar cell. In addition, when this colloidal solid is a protrusion, if a light-transmitting conductive layer is formed thereon, it may be peeled off along with the protrusion during the film forming process or after film formation. . Therefore, after the buffer layer is formed by the CBD process, the surface of the buffer layer is cleaned.
As the cleaning liquid, it is preferable to use pure water, ion exchange water, industrial water, or a solution obtained by adding an additive having a colloid removing effect to water. The temperature of the cleaning liquid is preferably 20 ° C. to 40 ° C. The cleaning method may be performed by immersing in a water tank or shower cleaning.

(After CBD cleaning liquid removal step)
Thereafter, the cleaning liquid adhering to the cleaned substrate is removed by spraying dry air or nitrogen on the front and back surfaces of the substrate.

When the buffer layer is made of ZnS, Zn (S, O), Zn (S, O, OH), after the post CBD cleaning liquid removing step, the temperature is 150 ° C. to 250 ° C., preferably 170 ° C. It is preferable to provide a heat treatment process (annealing process) in which heating is performed at 210 ° C. for 5 minutes to 60 minutes. The heating atmosphere is not particularly limited in air or vacuum. The heating means is not particularly limited, but heating using a commercially available oven, electric furnace, vacuum oven or the like is preferable.

After forming the buffer layer 40, a window layer (protective layer) 50 is formed as necessary. The window layer 50 is an intermediate layer that captures light. The window layer 50 is not particularly limited as long as it has a light-transmitting property for taking in light, but i-ZnO or the like is preferable as the composition in consideration of the band gap. The thickness of the window layer 50 is not particularly limited, and is preferably 10 nm to 2 μm, and more preferably 15 to 200 nm. The method for forming the window layer 50 is not particularly limited, but a sputtering method or an MOCVD method is suitable. On the other hand, since the buffer layer 40 is manufactured by the liquid phase method, it is also preferable to use the liquid phase method in order to simplify the manufacturing process. The window layer 50 is not essential, and there is a photoelectric conversion element without the window layer 50.

After the window layer 50 is formed, the translucent conductive layer 60 is provided on the window layer 50. The translucent conductive layer 60 is a layer that captures light and functions as an electrode that is paired with the lower electrode 20 and through which charges generated in the photoelectric conversion semiconductor layer 30 flow. The composition of the translucent conductive layer 60 is not particularly limited, and n-ZnO such as ZnO: Al, ZnO: Ga, and ZnO: B is preferable. The film thickness of the translucent conductive layer 60 is not particularly limited and is preferably 50 nm to 2 μm.
The film forming method of the translucent conductive layer 60 is not particularly limited, but the sputtering method and the MOCVD method are suitable as with the window layer. On the other hand, in order to simplify the manufacturing process, it is also preferable to use a liquid phase method.

After forming the translucent conductive layer 60, the upper electrode 70 is provided on the translucent conductive layer 60. The main component of the upper electrode 70 is not particularly limited, and examples thereof include Al. The thickness of the upper electrode 70 is not particularly limited and is preferably 0.1 to 3 μm.

In an integrated solar cell in which a large number of photoelectric conversion elements (cells) are integrated, the upper electrode is provided in a cell serving as a power extraction end among cells connected in series.

Of course, the manufacturing process of the photoelectric conversion element described above may include other processes than the processes described above. For example, a patterning process for integration such as a scribing process of the lower electrode, a scribing process after forming the photoelectric conversion layer, a scribing process after forming the buffer layer and the transparent conductive layer, and one module when using a long substrate An integrated photoelectric conversion device (integrated solar cell) can be manufactured by adding a cutting process step or the like. Moreover, you may attach a cover glass, a protective film, etc. as needed.

According to the production method of the present invention, even when a substrate including a portion that dissolves in the CBD reaction solution (for example, when a soluble component such as a substrate end surface or a substrate back surface is exposed) is used. Since the back surface of the substrate is brought into close contact with the drum 3 and the end surface of the substrate is further protected by the protective member 6 and the CBD method is continuously performed, the buffer layer can be formed without dissolving the substrate components.

In addition, in the method for manufacturing a photoelectric conversion element using a flexible substrate, the manufacturing process before and after the buffer layer forming step for manufacturing a highly efficient photoelectric conversion element has been clarified. It becomes possible to manufacture with high productivity.

The method for producing a photoelectric conversion element of the present invention continuously rolls from the surface treatment process of the photoelectric conversion semiconductor layer 30 to the post-CBD cleaning liquid removal process when a long flexible substrate is used as the substrate 10.・ It can be done by the to-roll method.

In the roll-to-roll method, a flexible substrate wound in a roll shape is drawn out, and intermittently or continuously conveyed, and a process until winding up by a winding roll is performed. Since it is possible to batch-process long substrates of the order, it is preferable because it can be easily mass-produced. Comparing the roll-to-roll method with the single-wafer method that transports individually separated substrates for each process, the single-wafer method requires the provision of a substrate loading and unloading unit for each process. Yes, the scale of the equipment for each process tends to be large, but in the roll-to-roll method, the base material flows intermittently or continuously between the processes, so the processes can be connected to each other, and the work involved in transporting the base material Reduction and downsizing of the device are possible.

An example of a manufacturing apparatus for carrying out the manufacturing method of the present invention by a roll-to-roll method will be described. FIG. 11 shows a schematic configuration of the manufacturing apparatus 100. The manufacturing apparatus 100 includes a surface treatment process and a surface treatment between the unwinding roll 11 and the CBD reaction tank 5 of the CBD apparatus 1 shown in FIG. Zones a to c for performing a post-water washing process and a post-surface treatment water removal process are provided, and further, a post-CBD cleaning is performed between the CBD reaction tank 5 and the take-up roll 12, which is the zone d for performing the CBD process. Zones e and f for performing each step of the process and the post-CBD cleaning liquid removal process are provided.

In the manufacturing apparatus 100, the substrate A after the photoelectric conversion semiconductor layer is formed (the component shown by A in FIG. 1 is elongated) is wound around the unwinding roll 11 in a roll shape, After the surface treatment of A, water washing and water removal (drying) are performed, and then a buffer layer is formed, and further washing and cleaning liquid removal (drying) are performed, and the film is taken up by the take-up roll 12.

In the manufacturing apparatus 100, the substrate A unwound from the unwinding roll 11 is guided by a guide roll (feeding-out roll) 35 and transported to the zone of each process. The plurality of guide rolls 35 are appropriately disposed at locations where adjustment of the transport direction of the substrate A is necessary. Of the guide rolls 35, 13, and 14, the ones arranged on the film formation surface side of the substrate are rolls that can support the substrate only by the edge portion of the substrate so as not to damage the film formation surface. is there.

The surface treatment process zone a is provided with a drum 23 similar to the drum 3 of the CBD device, and a liquid tank 25 filled with a surface treatment liquid 24 in which the drum is immersed, and the substrate A is a photoelectric conversion semiconductor. It is immersed in the surface treatment liquid 24 in a state of being in close contact with the drum 23 so that the layer 30 becomes the surface.

In the post-surface treatment rinsing process zone b, a first water tank 27 filled with pure water 26 is provided. The substrate A is washed with water by being conveyed in the pure water 26 of the first water tank 27 along the guide roll 35.

The post-surface treatment water removal step zone c is provided with a blower 31 that blows dry air onto the front and back surfaces of the substrate A. In the post-surface treatment water removal step zone c, dry air is blown onto the substrate, and the substrate is washed with water. Water adhering to the front and back is removed.

In the CBD process zone d, the CBD device 1 is provided, and the buffer layer 40 is formed on the photoelectric conversion semiconductor layer 30 in the reaction tank 5 of the CBD device 1.

In the post-CBD cleaning process zone e, a second water tank 29 filled with the cleaning liquid 28 is provided. The substrate A is cleaned by being conveyed in the cleaning liquid 28 of the second water tank 29 along the guide roll 35.

The post-CBD cleaning liquid removal process zone f is provided with a blower 32 that blows dry air onto the front and back surfaces of the substrate A. In the post-CBD cleaning liquid removal process zone f, dry air is sprayed onto the substrate, and the substrate and buffer are cleaned after cleaning. The cleaning liquid adhering to the layer surface is removed.

The manufacturing apparatus 100 shown in FIG. 11 does not have a zone for performing the annealing process of the buffer layer 40 after the CBD process, but the annealing process is performed after the cleaning liquid removing process zone f and before the winding roll 12. A process zone may be provided.

According to the above-described manufacturing apparatus, the manufacturing method of the present invention can be continuously performed in a roll-to-roll manner, and the production efficiency can be improved.

Examples and comparative examples according to the present invention will be described.
Photoelectric conversion elements were produced as Examples 1 to 4 and Comparative Examples 1 to 3 by combining the following substrates and processes. Table 1 shows the presence / absence of each step, the combination of conditions, and the evaluation results in each example.

(substrate)
A substrate having the following structure was used in common with all the examples and comparative examples.
As a flexible substrate, an anodized substrate in which an aluminum anodic oxide film (AAO) is formed on an Al surface on a stainless steel (SUS) -Al composite base material is used, and a soda lime glass layer (SLG layer) is further formed on the AAO surface. ) And a substrate on which a Mo electrode layer was formed as a lower electrode and a Cu (In _0.7 Ga _0.3 ) Se ₂ layer (CIGS layer) was formed as a photoelectric conversion semiconductor layer. The film thickness of each layer was SUS (over 100 μm), Al (30 μm), AAO (20 μm), SLG (0.2 μm), Mo (0.8 μm), CIGS (1.8 μm). The SLG layer and the Mo electrode layer were formed by sputtering, and the CIGS layer was formed by a three-stage method which is a kind of multi-source deposition method.
(Board protection)
For Examples 1 to 4 and Comparative Examples 1 and 2, the subsequent steps were performed in a state where the back surface and the edge of the substrate were protected by a protective member for protecting the reaction solution.

(Surface treatment process)
For the surface treatment of the CIGS layer, a 10% aqueous solution of potassium cyanide (KCN) was used as the surface treatment solution. A reaction vessel containing a surface treatment solution was prepared, and the surface of the CIGS layer was immersed in a KCN aqueous solution at room temperature for 3 minutes to remove impurities from the CIGS layer surface.

(Water washing process after surface treatment)
After the surface treatment step, sufficient washing with pure water was performed.

(Water removal process after surface treatment)
After washing with water, water was removed by blowing dry air.

(Pre-heating the substrate)
The substrate was fixed to the contact drum and heated until the substrate temperature reached 95 ° C. by heater heating from the back side of the substrate.

(CBD process)
<Preparation of CBD reaction solution>
Zinc sulfate aqueous solution (0.18 [M]) as aqueous solution (I) of component (Z), thiourea aqueous solution (thiourea 0.30 [M]) as aqueous solution (II) of component (S), component (C) Aqueous solution of trisodium citrate (0.18 [M]) was prepared as an aqueous solution (III), and aqueous ammonia (0.30 [M]) was prepared as an aqueous solution (IV) of component (N). Next, among these aqueous solutions, I, II, and III are mixed in the same volume, zinc sulfate 0.06 [M], thiourea 0.10 [M], trisodium citrate 0.06 [M]. The mixed solution was completed, and this mixed solution and 0.30 [M] aqueous ammonia were mixed in equal volumes to obtain a CBD reaction solution. When mixing the aqueous solutions (I) to (IV), the aqueous solution (IV) was added last. In order to obtain a transparent reaction solution, it is important to add the aqueous solution (IV) last. The pH of the obtained CBD reaction solution was 10.3.

<CBD condition 1>
The substrate was immersed in a CBD reaction solution whose temperature was adjusted to 90 ° C., and deposition was performed for 30 minutes.

<CBD condition 2>
The substrate was immersed in a CBD reaction solution at room temperature, and the CBD reaction solution in which the substrate was immersed was heated to 90 ° C. during 30 minutes, and then maintained at 90 ° C. for 30 minutes for precipitation.

(Cleaning process after CBD)
After the buffer layer was deposited by the CBD process, it was sufficiently cleaned using pure water as a cleaning liquid.

(After CBD cleaning liquid removal step)
After cleaning, the cleaning liquid was removed by blowing dry air.

(Annealing treatment)
Annealing treatment was performed in air at 200 ° C. for 1 hour.

(Element formation of examples and comparative examples)
After forming an Al-doped conductive zinc oxide thin film on the buffer layer by sputtering, an Al electrode is formed as an upper electrode by vapor deposition, and then a scribe process is performed on a 30 mm × 30 mm substrate cut out. Eight converter elements (single cell solar cell, light receiving area 0.516 cm ² ) were produced.
Eight cells were produced for each example and comparative example shown in Table 1.

(Evaluation methods)
About each Example and the comparative example, the amount of Al dissolution to a CBD reaction liquid, the buffer layer film thickness, and the photoelectric conversion efficiency were measured and evaluated.

<Measurement of Al dissolution amount in CBD reaction solution>
In each example and comparative example, 2.5 mL of CBD reaction solution after buffer layer deposition was diluted with a 25 mL volumetric flask (10-fold dilution), and SPS3000.
The Al concentration was measured using an ICP emission spectroscopic analyzer (lower limit of quantification: Al (<1 ppm)). In addition, the measurement result was measured twice for each sample, and the average value of the obtained values was calculated.

<Measurement of buffer layer thickness>
For the samples prepared by the methods of Examples 1 to 4 and Comparative Examples 1 to 3, the thickness of the buffer layer is evaluated at the stage where the buffer layer is formed on the CIGS layer or when the photoelectric conversion element is manufactured. For this purpose, after forming a protective film on the sample surface, focused ion beam (FIB) processing was performed to extract the cross section of the buffer layer, and SEM observation was performed on the cross section. The film thickness was measured at a total of 35 locations from this cross-sectional SEM image. Table 1 shows the average value of the film thickness measurement values.

<Measurement of photoelectric conversion efficiency>
The photoelectric conversion efficiency was measured for each of eight cells for each example and comparative example. Table 1 shows average values of photoelectric conversion efficiencies for eight cells obtained for each of the examples and comparative examples.
About each produced cell, using a solar simulator, Air
The energy conversion efficiency was measured under conditions of pseudo sunlight of Mass (AM) = 1.5 and 100 mW / cm ² . In addition, this measurement was implemented after performing light irradiation for 30 minutes. In Comparative Example 3, the photoelectric conversion efficiency was not measured because the dissolution of the substrate was large, the product was incomplete, and the conversion efficiency was expected to be low.

As can be seen from Table 1, the examples and comparative examples prepared by bringing the substrate into close contact with the drum and overlapping the ends with a protective material as in the present invention are buffer layers without eluting the Al contained in the substrate. Could be formed. On the other hand, elution of Al was confirmed in Comparative Example 3 in which the end face of the substrate was in contact with the reaction solution. Therefore, according to the production method of the present invention, even if the substrate contains a component that dissolves in the CBD reaction solution, it is possible to form a film without eluting such a component from the substrate.

In Comparative Example 2 in which the buffer layer was not formed, the conversion efficiency was very low, and in Comparative Example 1 in which the CIGS layer was not surface-treated, it was clear that the conversion efficiency was lower than that in the case of surface treatment. is there.

In addition, in Examples 1 and 2 in which the substrate was heated before the CBD process, the buffer layer had a larger deposition thickness compared to Example 3 in which the CBD process was performed under the same conditions without performing the substrate heating. It was confirmed that the time required to obtain the film thickness can be shortened by heating the substrate before the CBD process. Furthermore, it was also confirmed that the conversion efficiency is greatly improved by performing the annealing treatment after the CBD process.

Claims (10)

In the method for producing a photoelectric conversion element having a laminated structure of a buffer layer and a light-transmitting conductive layer on the photoelectric conversion semiconductor layer of a flexible substrate comprising a lower electrode and a photoelectric conversion semiconductor layer,
A surface treatment step of immersing the photoelectric conversion semiconductor layer surface in a surface treatment liquid;
A post-surface treatment water washing step of washing the substrate that has been surface-treated in the surface treatment liquid with water;
A post-surface treatment water removal step for removing water adhering to the substrate in the post-surface treatment water washing step;
Of the drum that closely supports the substrate, a reaction tank filled with a CBD reaction solution that immerses a part of the drum that closely supports the substrate, the end of the substrate that is closely supported by the drum, and the drum Using a CBD film forming apparatus having a protective member that protects the CBD reaction liquid by overlapping a portion where the substrate does not adhere, and a portion of the end of the substrate and the drum that does not adhere to the drum by the protective member A part of the drum that tightly supports the substrate on which the substrate is overlapped is immersed in the CBD reaction solution in the reaction tank, so that a part of the substrate is immersed in the CBD reaction solution, and a predetermined film formation is performed. A CBD step of forming a buffer layer on the photoelectric conversion semiconductor layer in the CBD reaction solution adjusted to a temperature;
A post-CBD cleaning step of immersing and cleaning the substrate after the buffer layer is formed; and
A post-CBD cleaning liquid removing step of removing the cleaning liquid adhering to the substrate in the post-CBD cleaning step;
A method for manufacturing a photoelectric conversion element, wherein the above steps are performed in this order. The method for manufacturing a photoelectric conversion element according to claim 1, wherein after the post-CBD cleaning liquid removing step, heat treatment is performed by heat-treating the substrate at 150 ° C to 250 ° C. 3. The method for manufacturing a photoelectric conversion element according to claim 1, wherein the substrate is heated to a temperature equal to or higher than the predetermined film formation temperature in the CBD step before the CBD step. The method of heating the substrate is such that the substrate is directly heated by a heater, or the surface treatment liquid used in the surface treatment step, the water used in the post-surface treatment water washing step is heated, and the substrate is placed in the heated liquid. The method for producing a photoelectric conversion element according to claim 3, wherein the photoelectric conversion element is by indirect heating by dipping. As the substrate, an anodized substrate in which an anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface side of an Al base material mainly composed of Al, and at least an Fe material mainly composed of Fe An anodized substrate having an anodized film mainly composed of Al ₂ O ₃ formed on at least one surface side of a composite base material in which an Al material composed mainly of Al is compounded on one surface side, and Fe An anodic oxide film mainly composed of Al ₂ O ₃ is formed on at least one surface side of the base material on which an Al film composed mainly of Al is formed on at least one surface side of the Fe material having the main component. 5. The method for manufacturing a photoelectric conversion element according to claim 1, wherein a substrate provided with any one of the anodized substrates is used. The CBD reaction solution is
In a mixed solution at room temperature in which water is mixed with component (Z) that is at least one zinc source, component (S) that is at least one sulfur source, component (C) that is at least one citric acid compound In addition, at least one component (N) selected from the group consisting of ammonia and ammonium salts is mixed at room temperature,
The concentration of the component (C) is 0.001 to 0.25M;
The concentration of the component (N) is 0.001 to 0.40 M;
6. The method for producing a photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a CBD reaction solution having a pH of 9.0 to 12.0 before the start of the reaction. In the CBD step, after the substrate is immersed in the CBD reaction solution adjusted to the film formation temperature of 70 to 95 ° C., Zn (S, O) and / or Zn (S, O) is formed at the film formation temperature. , OH) as a main component, forming a Zn compound layer as the buffer layer is a process for producing a photoelectric conversion element according to any one of claims 1 to 6. The method for producing a photoelectric conversion element according to any one of claims 1 to 7, wherein the surface treatment liquid is an aqueous solution containing a compound having a cyano group or an amino group. The method for producing a photoelectric conversion element according to claim 8, wherein the compound having a cyano group is potassium cyanide. The method for producing a photoelectric conversion element according to claim 8, wherein the compound having an amino group is at least one selected from ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. .

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