JP2014221882A - Method for treating resin substrate and method for producing solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a resin substrate capable of improving power generation properties by adding a 1A group metal to a CIS based or CZTS based light absorption layer laminated on a resin substrate, and a method for producing a solar battery having excellent power generation properties.SOLUTION: A resin substrate is contacted with a water solution including a 1A group metal hydroxide to introduce the 1A group metal at least into the surface of the resin substrate, next, the water solution is removed from the resin substrate, and then, heating treatment is performed while applying tension to the resin substrate. In the resin substrate treated in this way, a back face electrode layer, a CIS based or CZTS based light absorption layer, a buffer layer and a transparent electrode layer are formed on the side into which the 1A group metal has been introduced to produce a solar battery.

Description

  The present invention relates to a method for treating a resin substrate that can be used as a substrate such as a solar cell having a CIS-based or CZTS-based light absorption layer, and a method for producing a solar cell having a CIS-based or CZTS-based light absorption layer.

  In an electronic device, a dopant is added to a semiconductor to improve the characteristics.

  For example, a solar cell provided with a CIS light absorption layer (hereinafter also referred to as “CIS solar cell”) or a solar cell provided with a CZTS light absorption layer (hereinafter also referred to as “CZTS solar cell”). As described in Non-Patent Document 1, it is known that when a 1A group metal such as Na is added to the light absorption layer, the power generation efficiency is improved. Therefore, improvement of power generation efficiency is performed by adding a Group 1A metal such as Na to the light absorption layer.

  As a method for adding Na, there is a method in which soda lime glass is used as a substrate, and Na in the substrate is diffused into the light absorption layer in the process of film formation. However, in this method, since the substrate is limited to soda lime glass, the freedom of substrate selection is lost.

  As another method, there is a method of simultaneously depositing a Na compound such as NaF and adding Na to the light absorption layer when a CIS or CZTS light absorption layer is formed by a multi-source deposition method. However, since it is necessary to form a film by controlling a plurality of elements with high accuracy in the light absorption layer of CIS or CZTS, there is a problem that the control of the amount of each element added during film formation becomes more complicated. .

  As another method, there is a method in which a soda lime glass thin film is formed on a substrate or a back electrode, and Na in the soda lime glass thin film is diffused into the light absorption layer in the process of forming the light absorption layer. However, the soda lime glass thin film has a slow film forming speed and further requires a separate process for forming the soda lime glass thin film, which increases the number of processes and reduces the productivity of the solar cell. In addition, when the soda lime glass thin film is interposed between the layers, the adhesion between the back electrode and the substrate or the light absorption layer is easily lowered.

  As another method, there is a method of diffusing Na in the Na-containing thin film into the light absorption layer by forming a Na-containing thin film such as NaF on the back electrode or the light absorption layer. However, many Na-containing thin films such as NaF often have hygroscopicity, deliquescence and the like. For this reason, the Na-containing thin film may be altered to adversely affect the light absorption layer, the transparent electrode, and the like. Moreover, since the process for forming the Na-containing thin film is required separately, the number of processes is increased and the productivity of the solar cell is lowered. Moreover, there exists a possibility that the adhesiveness of a back surface electrode or a transparent electrode, and a light absorption layer may fall by interposing a Na containing thin film between layers.

  Further, Patent Document 1 discloses that an alkali metal containing an alkali metal with respect to an anodic oxide substrate that is not doped with an alkali metal in which an anodized film is formed on at least one surface side of a metal base material mainly composed of Al. It is disclosed that an alkali metal is diffused in a light absorption layer using a substrate in which an aqueous solution is brought into contact with an anodized film doped with an alkali metal.

JP 2010-232427 A

Tokio Nakata, CIGS solar cell basic technology, Nikkan Kogyo Shimbun, September 30, 2010, pages 71-76

  However, in Patent Document 1, since the anodic oxide film formed on the surface of the metal substrate is treated with an alkaline aqueous solution containing an alkali metal, the anodic oxide film may be corroded by the alkaline aqueous solution to cause pinholes or the like. was there. For this reason, the insulating property is lowered, and a short circuit or the like may occur between the metal substrate and the electrode or light absorption layer formed thereon, which may reduce the power generation efficiency of the solar cell.

  Accordingly, an object of the present invention is to treat a resin substrate that can improve power generation characteristics by adding a Group 1A metal to a CIS-based or CZTS-based light absorption layer laminated on the resin substrate. The object is to provide a method and a method for producing a solar cell excellent in power generation characteristics.

  In order to achieve the above object, the method for treating a resin substrate of the present invention is to bring a group 1A metal into at least the surface of the resin substrate by bringing the resin substrate into contact with an aqueous solution containing a group 1A metal hydroxide, Next, the aqueous solution is removed from the resin substrate, and then heat treatment is performed while applying tension to the resin substrate.

  In the method for producing a solar cell of the present invention, a resin substrate is brought into contact with an aqueous solution containing a group 1A metal hydroxide to introduce a group 1A metal into at least the surface of the resin substrate, and then the resin substrate The aqueous solution is removed from the resin substrate, and then heat-treated while applying tension to the resin substrate. Then, a back electrode layer and a CIS or CZTS-based material are formed on the resin substrate on the side where the group 1A metal is introduced. A light absorption layer, a buffer layer, and a transparent electrode layer are formed.

  According to the present invention, since the aqueous solution containing the group 1A metal hydroxide is brought into contact with the resin substrate, the group 1A metal can be introduced into at least the surface of the resin substrate. For this reason, the power generation characteristics of the solar cell can be improved by adding a Group 1A metal to the CIS-based or CZTS-based light absorption layer. In addition, since dirt and the like on the resin substrate are washed away by the aqueous solution, the adhesion of the thin film laminated on the resin substrate can be improved. In addition, after removing the aqueous solution from the resin substrate, heat treatment is performed while applying tension to the resin substrate, so that the residual stress of the resin substrate can be alleviated while drying the resin substrate. And since the residual stress of the resin substrate is relieved, the dimensional change of the resin substrate can be made small, and the thin film laminated on the resin substrate can be accurately scribed.

  In the present invention, the Group 1A metal hydroxide is preferably at least one selected from NaOH, KOH, and LiOH. According to this aspect, the power generation characteristics of the light absorption layer can be further improved.

  In this invention, it is preferable that the said resin substrate is 1 type chosen from the polyimide film, the polyethylene terephthalate film, and the polyethylene naphthalate film. The resin substrate is preferably selected in consideration of the maximum film formation temperature and film formation time of the solar cell.

  In the present invention, it is preferable to use a solution containing 0.1 to 5 mol / l of Group 1A metal hydroxide as the aqueous solution. Moreover, it is preferable to contact the said aqueous solution of 30-90 degreeC with the said resin substrate for 1 to 60 minutes. According to this aspect, dirt or the like on the resin substrate can be efficiently washed and removed while suppressing the denaturation of the resin substrate. Furthermore, a Group 1A metal can be efficiently introduced into at least the surface of the resin substrate.

  According to the present invention, since the aqueous solution containing the group 1A metal hydroxide is brought into contact with the resin substrate, the group 1A metal can be introduced into at least the surface of the resin substrate. For this reason, the power generation characteristics of the solar cell can be improved by adding a Group 1A metal to the CIS-based or CZTS-based light absorption layer. In addition, since dirt and the like on the resin substrate are washed away by the aqueous solution, the adhesion of the thin film laminated on the resin substrate can be improved. In addition, after removing the aqueous solution from the resin substrate, heat treatment is performed while applying tension to the resin substrate, so that the residual stress of the resin substrate can be alleviated while drying the resin substrate.

It is the schematic which shows one Embodiment of a solar cell. It is the schematic of the heating apparatus used with the processing method of the resin substrate of this invention. It is a figure which shows the conversion efficiency ((eta)) of the sample of Examples 1-4. It is a figure which shows the open circuit voltage (Voc) of the sample of Examples 1-4. It is a figure which shows the fill factor (FF) of the sample of Examples 1-4. It is a figure which shows the short circuit current (Jsc) of the sample of Examples 1-4. It is a figure which shows the dimensional variation rate of the sample of Examples 1 and 4. It is a figure which shows the output variation of the sample of Examples 1 and 4.

  First, an embodiment of a solar cell manufactured according to the present invention will be described with reference to FIG.

  A solar cell 10 shown in FIG. 1 is a solar cell having a substrate structure, and a back electrode layer 2, a light absorption layer 3, a buffer layer 4, and a transparent electrode layer 5 are laminated on a resin substrate 1.

  The material of the resin substrate 1 is not particularly limited, and those having heat resistance and flexibility are preferably used. For example, a polyimide film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyether sulfone film, an acrylic film, an aramid film, and the like can be given.

The resin substrate 1 may be formed with a barrier layer, an adhesion layer, and the like. The barrier layer is not particularly _{limited, Si 3 N 4, TiN,} CrN, Al 2 O 3, SiO 2 and the like. Although there is no limitation in particular as an adhesion layer, Ti, Cr, W, etc. are mentioned.

  In the present invention, the surface of the resin substrate 1 on the side where the back electrode layer 2 is formed is subjected to the treatment described later, and a 1A group metal is introduced. Examples of Group 1A metals include Na, K, and Li. Among these, Na is particularly preferable because the power generation characteristics of the CIS light absorption layer and the CZTS light absorption layer can be further improved.

  In the back electrode layer 2, it is preferable that at least the layer located on the light absorption layer 3 side contains Mo. According to this, corrosion resistance to Se or the like can be obtained, and corrosion degradation of the back electrode layer 2 can be prevented when the light absorption layer 3 is formed.

  The back electrode layer 2 containing Mo (hereinafter referred to as Mo layer) preferably has a film thickness of 100 to 1000 nm, more preferably 400 to 600 nm. If the Mo layer is thin, the corrosion resistance to Se or the like may be insufficient. If the film thickness of the Mo layer is large, productivity will be deteriorated, for example, it takes time to form. Furthermore, peeling tends to occur easily depending on the stress difference with the substrate.

  The back electrode layer 2 may be a single layer of Mo, or a laminated body of a metal layer (hereinafter also referred to as a low resistance metal layer) containing a conductive material having an electric resistivity lower than that of Mo and a Mo layer. It may be configured.

As the conductive material having an electrical resistivity smaller than that of Mo, a conductive material having an electrical resistivity at 20 ° C. of less than 5.3 × 10 ⁻⁸ Ω · m is preferable. By carrying out like this, the electrical resistivity of the back surface electrode layer 2 can be effectively made smaller than the case where it comprises Mo alone. Specific examples of the conductive material having an electric resistivity lower than that of Mo include Ag, Cu, Au, Al, Mg, W, and alloys thereof, and one or more of these can be preferably used.

The light absorption layer 3 is a CIS-based or CZTS-based light absorption layer. In the present invention, the CIS-based light absorption layer is a light formed of a CIS-based semiconductor compound such as CuInSe ₂ , CuGaSe ₂ , Cu (In, Ga) Se ₂ , Cu (In, Ga) (S, Se) ₂ or the like. Means absorption layer. The CZTS light absorption layer means a light absorption layer formed of a CZTS semiconductor compound such as Cu ₂ ZnSnSe ₄ or Cu ₂ ZnSn (S, Se) ₄ .

  Although the film thickness of the light absorption layer 3 changes with kinds, about 1.5-2.5 micrometers is preferable.

The buffer layer 4 is composed of an n-type transparent conductive film having a wide forbidden band. Preferably, it is a compound containing at least one element selected from Cd, Zn, and In. Specific _{compounds, CdS, ZnO, ZnS, Zn} (OH) 2, ZnInSe 2, ZnMgO, In 2 O 3, In 2 S 3 , and the like.

The transparent electrode layer 5 is made of a transparent conductive material such as ZnO, SnO ₂ , In ₂ O ₃ , or ITO.

  Moreover, you may provide high resistance buffer layers, such as ZnO, between the buffer layer 4 and the transparent electrode layer 5 as needed. Providing a high resistance buffer layer is effective in reducing leakage current and improving output.

  Next, taking the method for producing a solar cell shown in FIG. 1 as an example, a method for producing a solar cell including the method for treating a resin substrate of the present invention will be described.

  First, the processing method of the resin substrate of this invention is demonstrated.

  In the present invention, an aqueous solution containing a group 1A metal hydroxide is brought into contact with the resin substrate.

  By bringing the aqueous solution into contact with the resin substrate, the resin substrate reacts with the group 1A metal hydroxide, and the group 1A metal is introduced into at least the surface of the resin substrate. And since the stain | pollution | contamination etc. on the resin substrate are washed away by the said aqueous solution, the adhesiveness of the thin film laminated | stacked on a resin substrate can be improved. Whether or not the group 1A metal is introduced on the surface of the resin substrate can be easily confirmed by a flame reaction method or the like.

  The mechanism by which the Group 1A metal is introduced into the resin substrate will be described by taking as an example the case where a polyimide film is used as the resin substrate and NaOH is used as the Group 1A metal hydroxide.

  As a model for Na addition on the polyimide film, the following hydrolysis-Na salt formation model can be considered. When NaOH is brought into contact with the polyimide film, the polyimide ring is hydrolyzed and opened (see reaction formula (1)). Then, the ring-opened polyimide and NaOH react to produce a sodium salt (see reaction formula (2)). In this way, it is presumed that the Group 1A metal is introduced into at least the surface of the resin substrate.

  In the present invention, the group 1A metal hydroxide is preferably at least one selected from NaOH, KOH and LiOH, and NaOH is particularly preferable. The power generation characteristics can be improved by adding Na, K, Li, or the like to the CIS light absorption layer or the CZTS light absorption layer. In particular, power generation characteristics can be further improved by adding Na. For this reason, by using at least one selected from NaOH, KOH, and LiOH as the group 1A metal hydroxide, an element that easily improves the power generation characteristics of the CIS-based light absorption layer and the CZTS-based light absorption layer Can be introduced into at least the surface of the resin substrate.

  In the present invention, the method for contacting the aqueous solution with the resin substrate is not particularly limited. Examples thereof include a method of spraying the aqueous solution on a resin substrate, a method of immersing the resin substrate in a bathtub filled with the aqueous solution, and the like.

  In the present invention, the concentration of the group 1A metal hydroxide in the aqueous solution brought into contact with the resin substrate is preferably 0.1 to 5 mol / l, particularly preferably 1 to 3 mol / l. When the concentration of the group 1A metal hydroxide is less than 0.1 mol / l, dirt or the like on the surface of the resin substrate may not be sufficiently removed. Furthermore, the Group 1A metal may not be sufficiently introduced into the resin substrate. Moreover, when the concentration of the group 1A metal hydroxide exceeds 5 mol / l, the handleability of the aqueous solution tends to deteriorate. In addition, there is a tendency for the cleaning process to be time consuming and cleaning waste liquid to increase. Furthermore, the reaction between the resin substrate and the aqueous solution proceeds excessively, and the characteristics such as heat resistance of the resin substrate tend to deteriorate.

  In the present invention, the contact time between the resin substrate and the aqueous solution is preferably 1 to 60 minutes, and more preferably 2 to 10 minutes. If the contact time is less than 1 minute, dirt or the like on the surface of the resin substrate may not be sufficiently removed. Furthermore, the Group 1A metal may not be sufficiently introduced into the resin substrate. On the other hand, when the contact time exceeds 60 minutes, the reaction between the resin substrate and the aqueous solution proceeds excessively, and characteristics such as heat resistance of the resin substrate tend to be deteriorated. In addition, since processing time is required, productivity decreases. In addition, when spraying aqueous solution and making aqueous solution contact a resin substrate, the spraying time of aqueous solution corresponds to contact time. Moreover, when a resin substrate is immersed in an aqueous solution and the aqueous solution is brought into contact with the resin substrate, the immersion time corresponds to the contact time.

  In this invention, 30-90 degreeC is preferable and, as for the temperature of the aqueous solution made to contact a resin substrate, 50-90 degreeC is more preferable. If the temperature of the aqueous solution is lower than 30 ° C., dirt on the surface of the resin substrate may not be sufficiently removed. Furthermore, the Group 1A metal may not be sufficiently introduced into the resin substrate. When the temperature of the aqueous solution exceeds 90 ° C., the handleability of the aqueous solution tends to deteriorate. Furthermore, the reaction between the resin substrate and the aqueous solution proceeds excessively, and the characteristics such as heat resistance of the resin substrate tend to deteriorate.

  In the present invention, when the aqueous solution is brought into contact with the resin substrate, only the surface on the side on which the back electrode layer is formed is brought into contact with the aqueous solution, and the surface opposite to the surface on which the back electrode layer is formed (hereinafter referred to as “substrate back side”). ) Is preferably prevented from coming into contact with an aqueous solution. Since it is not necessary to treat the back side of the substrate with the above aqueous solution, if the aqueous solution is also brought into contact with the back side of the substrate, it tends to require time and effort for cleaning and drying. Examples of the method of bringing the aqueous solution into contact with only the surface of the resin substrate on the side where the back electrode layer is formed include, for example, attaching a protective sheet to the back side of the substrate, or adsorbing the back side of the substrate with a vacuum chuck, etc. There is a method to prevent sneaking around.

  Next, the resin substrate is cleaned with a cleaning liquid such as pure water to remove the aqueous solution from the resin substrate.

  Before performing the cleaning process, the droplets adhering to the resin substrate may be removed by air blow or the like. According to this, the usage amount of the cleaning liquid and the discharge amount of the cleaning waste liquid can be reduced.

  Further, the droplets adhering to the resin substrate after the cleaning treatment may be removed by air blow or the like. This is effective for shortening the processing time of the subsequent process. At that time, it is desirable to perform a charge removal process in order to prevent adhesion of dust.

  Next, the resin substrate is heat-treated while applying tension. Thereby, the residual stress of the resin substrate can be relaxed while drying the resin substrate.

  In the present invention, the heat treatment is preferably performed in a reduced pressure atmosphere, more preferably 0.5 atm or less, and particularly preferably 0.1 atm or less. By performing the heat treatment in a reduced pressure atmosphere, moisture can be efficiently removed from the resin substrate.

  In the present invention, the heat treatment temperature is preferably 100 ° C. or higher and lower than the melting point or thermal decomposition temperature of the resin substrate. 100-400 degreeC is preferable and, as for the heat processing temperature in case a resin substrate is a polyimide film, 150-250 degreeC is more preferable. If the heat treatment temperature is less than 100 ° C., the resin substrate may not be sufficiently dried.

  In the present invention, the heat treatment time is preferably 30 seconds to 60 minutes, and more preferably 1 to 5 minutes. If the heat treatment time is less than 30 seconds, drying may be insufficient. Even if it exceeds 60 minutes, there is not much change, leading to a decrease in productivity.

  In the present invention, the tension applied to the resin substrate is preferably 30 to 200 N / m, and more preferably 50 to 80 N / m. If it is less than 30 N / m, the residual stress of the resin substrate may not be sufficiently relaxed. When it exceeds 200 N / m, the resin substrate is deformed and defective products are likely to be generated, and the yield tends to decrease.

  The direction of tension applied to the resin substrate is not particularly limited. For example, when heat treatment is performed while transporting a long resin substrate, it is preferable to apply tension in the transport direction of the resin substrate, that is, the longitudinal direction of the resin substrate. Further, tension may be applied in a direction orthogonal to the direction of transport of the resin substrate, that is, the short direction of the resin substrate.

  The heat treatment can be performed using, for example, the apparatus shown in FIG.

  A heat treatment apparatus 30 shown in FIG. 2 includes a substrate roll 32 around which a resin substrate is wound, a resin substrate winding core 33, a heater 34, and rolls 35 to 38 in a vacuum chamber 31. Yes. The resin substrate 1 unwound from the substrate roll 32 is wound around the winding core 33 via the rolls 35 to 38. Then, the roll 35 is pushed out to the winding side (in the direction of arrow A), and the roll 38 is pushed out to the unwinding side (in the direction of arrow B). The resin substrate can be heat-treated while applying tension in the longitudinal direction. Moreover, in FIG. 2, since the heater 34 is arrange | positioned at the both surfaces side of the resin substrate which moves the inside of a vacuum chamber, a resin substrate can be heated from both surfaces, and it can improve drying efficiency.

  Next, a back electrode layer is formed on the surface of the resin substrate thus treated. A back surface electrode layer can be formed by methods, such as a sputtering method and a vapor deposition method, using the electrode material containing Mo, for example. In addition, a low-resistance metal layer is formed using an electrode material containing a conductive material selected from Ag, Cu, Au, Al, Mg, W and alloys thereof, and then Mo is contained on the low-resistance metal layer. By forming the Mo layer using the electrode material, a back electrode layer in which the Mo layer is laminated on the low resistance metal layer can be formed.

  Next, a light absorption layer is formed on the back electrode layer. The method for forming the light absorption layer is not particularly limited, and can be formed by a conventionally known method such as a selenization method or a multi-source co-evaporation method.

  When forming a light absorption layer using a selenization method, a metal precursor film is formed on a resin substrate.

  The method for forming the metal precursor film is not particularly limited. Examples include sputtering, vapor deposition, plating, and nanoparticle printing. Among these, the sputtering method is preferable because a metal film having a small in-plane distribution can be efficiently formed.

  The material of the metal precursor film varies depending on the type of the light absorption layer. In the case of forming a CIS-based light absorption layer, a metal film containing at least Cu and In and / or Ga is formed as a metal precursor film. When a CZTS-based light absorption layer is formed, a metal film including at least Cu, Zn, and Sn is formed as the metal precursor film.

  Next, the resin substrate on which the metal precursor film is formed is introduced into a heat treatment apparatus, and heat treatment is performed in an atmosphere having at least a selenium source.

Further, after heat treatment in an atmosphere having at least a selenium source, the internal selenium atmosphere is once exhausted by a vacuum pump or the like, and then a sulfur-containing gas such as H ₂ S diluted with an inert gas such as nitrogen gas is heat treated. It may be introduced into the apparatus and further heat-treated in an atmosphere having at least a sulfur source. After performing heat treatment in an atmosphere having a selenium source, further heat treatment is performed in an atmosphere having a sulfur source, whereby a CIS-based or CZTS-based light absorption layer having excellent power generation efficiency can be formed.

  The heat treatment conditions in the atmosphere containing the selenium source and the heat treatment conditions in the atmosphere containing the sulfur source differ depending on the type of the metal precursor film and the type of the light absorption layer to be formed.

  As a specific example of the heat treatment conditions in an atmosphere having a selenium source, for example, the substrate temperature is gradually raised from 100 to 200 ° C. to 350 to 550 ° C., and in that state, preferably 10 to 240 minutes. More preferably, a method of holding for 20 to 120 minutes may be mentioned. Moreover, 1-20 mol% is preferable and, as for the molar concentration of selenium of a selenium containing gas, 2-10 mol% is more preferable.

  As a specific example of the heat treatment conditions in an atmosphere having a sulfur source, for example, the substrate temperature is raised to 500 to 650 ° C., preferably 5 to 120 minutes, more preferably 20 to 120 minutes. preferable. Moreover, 1-30 mol% is preferable and, as for the molar concentration of sulfur of sulfur containing gas, 2-20 mol% is more preferable.

  By performing the heat treatment in this manner, the metal precursor film reacts to form a CIS-based or CZTS-based light absorption layer. Note that the upper limit of the substrate temperature during the heat treatment varies depending on the substrate used.

  Moreover, when forming a light absorption layer by the multi-component simultaneous vapor deposition method, it can form by co-evaporating the raw material containing the structural element of a light absorption layer on a back surface electrode layer. For example, in the case of forming a CIS-based light absorption layer, a material containing Cu, In, Ga, Se, or the like can be formed on the back electrode layer by simultaneous vapor deposition. In the case of forming a CZTS-based light absorption layer, it can be formed by co-evaporating raw materials containing Cu, Zn, Sn, Se and the like.

  Next, a buffer layer is formed on the light absorption layer. The method for forming the buffer layer is not particularly limited, and a conventionally known method can be used. For example, solution growth (CBD), vapor deposition, sputtering, atomic deposition (ALD), ionic layer gas reaction (MOCVD), metal organic chemical vapor deposition (MOCVD) : Metal Organic Chemical Vapor Deposition), sputtering method and the like. Of these, the solution growth method is preferable. In the solution growth method, for example, by immersing the substrate on which the light absorption layer is formed in a solution containing at least one element selected from Cd, Zn, and In, the material is selected from Cd, Zn, and In on the light absorption layer. A buffer layer containing at least one element can be formed. As described above, the solution growth method has a simple apparatus configuration, can be formed at a low cost, has a high adhesion, and has a surface coating property on the light absorption layer.

  Next, a transparent electrode layer is formed on the buffer layer by a method such as sputtering or vapor deposition. Moreover, you may provide high resistance buffer layers, such as ZnO, between a buffer layer and a transparent electrode layer as needed. Providing a high-resistance buffer layer is effective in reducing leakage current and improving output.

  Then, the element formed in this manner is scribe-processed by a mechanical scribe method, a laser scribe method, or the like and separated into cells. The scribing process may be performed in a state where the resin substrate is stretched under tension. The direction of tension is preferably the same as the direction in which tension is applied to the resin substrate during the heat treatment of the resin substrate.

  And a substrate type solar cell can be manufactured by connecting each cell in series and / or in parallel, and attaching an extraction electrode etc.

  According to the present invention, since the aqueous solution containing the group 1A metal hydroxide is brought into contact with the resin substrate, the group 1A metal can be introduced into at least the surface of the resin substrate. For this reason, the group 1A metal introduced into the resin substrate can be added to the light absorption layer in the process of forming the light absorption layer, and the power generation characteristics of the solar cell can be improved. Moreover, since the stain | pollution | contamination etc. on the resin substrate 1 are washed away by the said aqueous solution, a back surface electrode layer can be formed into a film with sufficient adhesiveness on the resin substrate.

  In addition, since the residual stress of the resin substrate is relaxed, the dimensional change of the resin substrate before and after releasing the tension can be suppressed even if the scribe processing is performed with the resin substrate stretched with tension, and the scribe of the device is suppressed. Processing can be performed with high accuracy.

  The method for manufacturing the solar cell according to the present invention has been described above by taking the substrate type solar cell as an example. However, the method for manufacturing the solar cell according to the present invention can be applied to a super straight type solar cell or a double-sided light receiving solar cell. It can also be applied to solar cells other than the substrate type such as a battery.

(Example 1)
The polyimide film is drawn out from the substrate roll on which the polyimide film is wound, and immersed in a bath filled with an aqueous NaOH solution having a NaOH concentration of 1 mol / l and a temperature of 80 ° C. on the transport path, and then the polyimide film is removed from the bath. The liquid droplets attached to the polyimide film were removed by air blowing.
Next, after immersing the polyimide film in a bathtub filled with pure water for 5 minutes, the polyimide film was taken out of the bathtub and the droplets adhering to the polyimide film were removed by air blowing.
Next, the polyimide film from which the droplets were removed was subjected to heat treatment at 200 ° C. for 2 minutes under a reduced pressure of 0.1 atm while applying a tension of 60 N / m in the polyimide film conveyance direction.
Thus, the polyimide film was processed. When a flame reaction test was performed on the treated polyimide film, yellow color was exhibited. It was confirmed that Na was introduced into the polyimide film. Moreover, when the surface state of the polyimide film after a process was observed, the contaminants etc. were removed, resin modification | denaturation etc. were not seen but it had a clean surface state.

Next, a Mo film was formed to a thickness of 500 nm on the polyimide film subjected to the above treatment by a sputtering method to form a back electrode layer.
Next, 2.2 μm of a light absorption layer made of a semiconductor compound made of Cu (In, Ga) Se ₂ was formed on the back electrode layer by multi-source deposition.
Next, the polyimide film on which the light absorption layer is formed is immersed in an aqueous solution containing a metal salt (CdSO ₄ ), a sulfide (thiourea) and a complexing agent (ammonia) at 60 to 70 ° C. for 10 to 15 minutes, About 50 nm of a buffer layer made of CdS was formed by a solution growth method.
Next, by sputtering, 100 nm of ZnO was formed as the high resistance buffer layer and 300 nm of ZnO: Al was formed as the transparent conductive film, thereby forming an element.
Next, the polyimide film on which the element was formed was divided into 5 cells at intervals of 2 cm.
Thus, the small area sample for the evaluation test of a CIS type solar cell was manufactured.

(Example 2)
A polyimide film was treated in the same manner as in Example 1 except that an aqueous NaOH solution having a NaOH concentration of 2 mol / l was used. When a flame reaction test was performed on the treated polyimide film, yellow color was exhibited. It was confirmed that Na was introduced into the polyimide film. Moreover, when the surface state of the polyimide film after a process was observed, the contaminants etc. were removed, resin modification | denaturation etc. were not seen but it had a clean surface state.
Each layer was formed on the polyimide film thus treated in the same manner as in Example 1 to produce a small area sample for an evaluation test of a CIS solar cell.

(Example 3)
A polyimide film was treated in the same manner as in Example 1 except that an aqueous NaOH solution having a NaOH concentration of 5 mol / l was used. When a flame reaction test was performed on the treated polyimide film, yellow color was exhibited. It was confirmed that Na was introduced into the polyimide film. Moreover, when the surface state of the polyimide film after a process was observed, the contaminants etc. were removed, resin modification | denaturation etc. were not seen but it had a clean surface state.
Each layer was formed on the polyimide film thus treated in the same manner as in Example 1 to produce a small area sample for an evaluation test of a CIS solar cell.

(Example 4)
The polyimide film is pulled out from the substrate roll on which the polyimide film is wound, and is immersed in a bathtub filled with pure water on the transport path for 5 minutes, and then the polyimide film is taken out from the bathtub and adhered to the polyimide film. The droplet was removed by air blow. And the polyimide film from which the droplet was removed was heat-treated at 200 ° C. for 2 minutes under a reduced pressure of 0.1 atm.

  Each layer was formed on the polyimide film thus treated in the same manner as in Example 1 to produce a small area sample for an evaluation test of a CIS solar cell.

The small area samples for evaluation tests of Examples 1 to 4 are irradiated with light of AM 1.5 and 100 mW / cm ² by a solar simulator to obtain a current-voltage curve, and the conversion efficiency (η) is obtained from the current-voltage curve. , Open circuit voltage (Voc), fill factor (FF), and short circuit current (Jsc) were determined (n = 6). The results are shown in FIGS.

  Moreover, about the small area sample for an evaluation test of Example 1 and Example 4, the space | interval between cells was measured and the dimensional variation rate was calculated | required (n = 5). In addition, the dimensional variation rate was calculated | required from the following formula | equation. The results are shown in FIG.

  Dimensional variation rate (%) = (((| 2 (cm) −actual value of distance between cells (cm) |) / 2 (cm)) × 100

  Moreover, about the small area sample for an evaluation test of Example 1 and Example 4, the output of 18 cells was calculated | required and the output variation was evaluated. The variation in output was expressed as a ratio with respect to the median, with the average value being the median. The results are shown in FIG.

  From the result of FIGS. 3-6, it turns out that the conversion efficiency ((eta)) of a CIS type solar cell, an open circuit voltage (Voc), and a fill factor improve by processing a polyimide film with NaOH aqueous solution. Moreover, the variation of the short circuit current (Jsc) could be suppressed.

  In addition, from the results of FIGS. 7 and 8, the polyimide film heat treatment is performed while tension is applied, so that the dimensional stability of the polyimide film is improved, the accuracy of the scribe process is improved, and the output variation of each cell is varied. It can be seen that it can be suppressed.

1: Resin substrate 2: Back electrode layer 3: Light absorption layer 4: Buffer layer 5: Transparent electrode layer 10: Solar cell 30: Heat treatment device 31: Vacuum chamber 32: Substrate roll 33: Winding core 34: Heater 35- 38: Roll

Claims (10)

  An aqueous solution containing a group 1A metal hydroxide is brought into contact with the resin substrate to introduce a group 1A metal into at least the surface of the resin substrate, and then the aqueous solution is removed from the resin substrate, and then the resin substrate A method for treating a resin substrate, comprising performing a heat treatment while applying tension to the substrate.   The method for treating a resin substrate according to claim 1, wherein the Group 1A metal hydroxide is at least one selected from NaOH, KOH, and LiOH.   The method for treating a resin substrate according to claim 1, wherein the resin substrate is a kind selected from a polyimide film, a polyethylene terephthalate film, and polyethylene naphthalate.   The processing method of the resin substrate of any one of Claims 1-3 using what contains 0.1-5 mol / l of 1A group metal hydroxide as said aqueous solution.   The method for treating a resin substrate according to claim 1, wherein the aqueous solution at 30 to 90 ° C. is brought into contact with the resin substrate for 1 to 60 minutes.   An aqueous solution containing a group 1A metal hydroxide is brought into contact with the resin substrate to introduce a group 1A metal into at least the surface of the resin substrate, and then the aqueous solution is removed from the resin substrate, and then the resin substrate After applying heat treatment to the resin substrate, a back electrode layer, a CIS-based or CZTS-based light absorption layer, a buffer layer, and a transparent electrode layer are formed on the side of the resin substrate on which the group 1A metal is introduced. And forming a solar cell.   The method for producing a solar cell according to claim 6, wherein the Group 1A metal hydroxide is at least one selected from NaOH, KOH and LiOH.   The method for producing a solar cell according to claim 6 or 7, wherein the resin substrate is one selected from a polyimide film, a polyethylene terephthalate film, and a polyethylene naphthalate film.   The manufacturing method of the solar cell of any one of Claims 6-8 which uses what contains 0.1-5 mol / l of 1A group metal hydroxides as said aqueous solution.   The method for producing a solar cell according to any one of claims 6 to 9, wherein the aqueous solution at 30 to 90 ° C is brought into contact with the resin substrate for 1 to 60 minutes.