JP2015126163A - Cigs solar cell and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CIGS solar cell in which the surface state on the back (base material side) of a cell after manufacturing is excellent, and electrical interconnection of the cells using the back can be maintained stably over a long term, and to provide a manufacturing method therefor.SOLUTION: On one side of a long base material 1 having conductivity, a back electrode layer 2 and a surface electrode consisting of a CIGS photoelectric conversion layer 3, a buffer layer 4, and a transparent conductive layer 5 are laminated sequentially by using a roll-to-roll process. In such a CIGS solar cell, a protective layer P having a thickness of 10 nm or more composed of at least one kind of metal selected from a group of molybdenum, tungsten, niobium, tantalum and titanium or an alloy thereof is formed on the other side of the long base material 1.

Description

  The present invention relates to a CIGS solar cell including a compound semiconductor layer made of Cu, In, Ga, and Se as a photoelectric conversion layer and a method for manufacturing the CIGS solar cell.

  Thin film solar cells represented by amorphous silicon solar cells and compound thin film solar cells can significantly reduce material costs and manufacturing costs as compared to conventional crystalline silicon solar cells. For this reason, in recent years, these research and development have been promoted rapidly, and among them, elements of Group 11 (Group I), Group 13 (Group III), and Group 16 (Group VI) on the periodic table as constituent substances. The CIGS solar cell in which the light absorption layer (photoelectric conversion layer) is made of a copper (Cu), indium (In), gallium (Ga), or selenium (Se) alloy is an excellent solar light. Since it has conversion efficiency, it attracts particular attention among thin film solar cells.

  With regard to the CIGS solar cell, the present applicants have adopted a roll-to-roll process (Roll to Roll Process) using a long substrate wound in a roll shape for the production of solar cells. The method which can manufacture a quality photovoltaic cell (CIGS photoelectric conversion layer) efficiently is proposed (refer patent documents 1 and 2).

  FIG. 6 is a schematic configuration diagram of a CIGS solar cell according to the above proposal, and FIG. 4 is a schematic configuration diagram of a manufacturing process (apparatus) by a roll-to-roll process of this CIGS solar cell.

  As shown in FIG. 6, the CIGS solar cell includes a support (long substrate 1), a back electrode layer 2, a compound semiconductor film (CIGS photoelectric conversion layer 3), a buffer layer 4, and a transparent conductive material. The layer 5 is composed of an extraction electrode (not shown) and the like. The CIGS photoelectric conversion layer 3 is formed by sequentially depositing (stacking) Cu, In, Ga, and Se as described later. In addition, this figure shows a part of a long (ribbon-shaped or strip-shaped) CIGS solar cell, and this long-shaped cell is cut at a fixed length after the manufacture is completed, and the electrodes are connected (coupled). ) To form a solar cell module.

  As shown in FIG. 4, the process of manufacturing the long CIGS solar cell is performed by connecting a plurality of processing decompression chambers (11, 12, 13, 14) in a line so that continuous processing can be performed. The base material supply side decompression chamber X provided with the unwinding machine A that supplies the base material for processing (ribbon-like long base material 1) is formed on both ends thereof, and the long base after processing. A base material recovery side decompression chamber Y including a winder B that recovers and winds the material 1 is disposed. In addition, the white arrow in a figure shows the flow direction of the elongate base material 1. FIG. Reference numeral 21 denotes a sputtering apparatus for forming the back electrode layer, reference numeral 26 denotes a sputtering apparatus for forming the buffer layer, and reference numeral 27 denotes a sputtering apparatus for forming the transparent conductive layer.

And each said decompression chamber for processing is the decompression chamber 11 for back electrode formation, the decompression chamber 12 for compound semiconductor layer formation from the unwinding machine A side [upstream side of a base material flow direction (white arrow)], The decompression chamber 13 for forming the buffer layer and the decompression chamber 14 for forming the transparent conductive layer are arranged in this order, and the decompression chambers 11 to 14 are maintained at a required pressure between the respective decompression chambers 11 to 14 for processing. Differential exhaust devices Z ₁ , Z ₂ , Z ₃ (arrows indicate exhaust) are provided, and the long base 1 is interrupted between processes (steps) that require different environmental pressures (atmospheres). Instead, it is moved by the winding force of the winder B, and the processing and film formation (lamination) can be performed continuously.

Further, in the step of forming the compound semiconductor layer (in this example, the CIGS photoelectric conversion layer) (the decompression chamber 12), as shown in an enlarged schematic view of FIG. 5, a plurality of CIGS photoelectric conversion layer forming plurals are formed. The vapor deposition sources 22, 23, 24, and 25 are arranged side by side along the flow direction of the long base material 1. And the long base material 1 introduced into the decompression chamber 12 from the decompression chamber 11 (back electrode forming step) via the differential exhaust device Z ₃ is processed surface (in the figure, the back electrode is formed). With the lower surface side facing the nozzles of the respective vapor deposition sources 22 to 25, the vapor deposition materials set in the respective vapor deposition sources 22 to 25 (in this example, in this example) are run on these at a predetermined speed. , Cu, In, Ga, Se) are sequentially laminated in layers on the long base material 1.

  As described above, when the CIGS photoelectric conversion layer 3 is formed by vacuum vapor deposition, the temperature of the vapor deposition material in each vapor deposition source 22, 23, 24, 25 (transpiration temperature) is, for example, about 1150 ° C. for Cu. , In is set to about 950 ° C., Ga is set to about 1000 ° C., and Se is set to about 200 ° C. These temperature settings are adjusted in consideration of the melting point and vapor pressure of each vapor deposition material (that is, the vapor deposition amount or vapor deposition rate per hour).

JP 2012-195461 A JP 2013-115119 A

  By the way, in the manufacture of CIGS solar cells using the roll-to-roll process as described above, from the viewpoint of heat resistance, CTE (thermal expansion coefficient, linear expansion coefficient) matching with the CIGS film, and cost, a supporting substrate (long As the scale substrate 1), a ferritic stainless steel (SUS) substrate or alloy foil is preferably used.

  However, in the manufacture of CIGS solar cells by the roll-to-roll process using the SUS substrate and the like, one side of the long substrate (SUS substrate) on which the photoelectric conversion layer and the like are stacked after the manufacture of the cell is completed ( The surface state (appearance) of the other surface (non-processed surface, upper surface in FIGS. 4 and 5) opposite to the surface to be processed (lower surface in FIGS. 4 and 5) is rough, and the cells are connected (electrically connected). At this time, the adhesion (compatibility or wetting) of solder or metal paste to this surface is poor, and stable electrical connection may not be maintained.

  Then, when the present inventors pursued the cause of these malfunctions, the cause was "the brittle layer formed unintentionally on the back surface (non-processed surface) of the long base material of the completed CIGS solar cell. "(Corrosion layer). In addition, the inventors have determined from the analysis of the “brittle layer” that the corrosive layer is a selenium compound produced by exposure to high-temperature selenium (Se) gas.

  The present invention has been made in view of such circumstances, and the surface state of the back surface (base material side) of the manufactured cell is good, and electrical connection between the cells using this back surface has been made for a long time. It is an object of the present invention to provide a CIGS solar cell that can be stably maintained and a method for producing the same.

  In order to achieve the above object, the present invention provides a surface electrode composed of a back electrode layer, a CIGS photoelectric conversion layer, a buffer layer, and a transparent conductive layer on one surface of a long substrate having conductivity. It is a CIGS solar cell that is sequentially laminated using a roll-to-roll process, and the other surface of the long base material has molybdenum, tungsten, niobium, tantalum, among the elements of groups 4 to 6 of the periodic table. A CIGS solar cell in which a protective layer made of at least one metal selected from the group consisting of titanium or an alloy thereof having a thickness of 10 nm or more is formed.

  In order to achieve the same object, the present invention forms a back electrode layer on the surface of a long conductive substrate, and forms a CIGS photoelectric conversion layer on the exposed surface of the back electrode layer. A step, a step of forming a buffer layer on the exposed surface of the CIGS photoelectric conversion layer, and a step of forming a surface electrode made of a transparent conductive layer on the exposed surface of the buffer layer. It is a manufacturing method of a CIGS solar cell in which each of the above layers is sequentially laminated on one surface side of the long base material, and prior to the step of forming the CIGS photoelectric conversion layer, on the other surface side of the long base material, Among the elements of groups 4 to 6 of the periodic table, a thick layer that forms a protective layer having a thickness of 10 nm or more made of at least one metal selected from the group consisting of molybdenum, tungsten, niobium, tantalum, and titanium, or an alloy thereof. The process of the battery cells to the second aspect.

  That is, as described above, the present inventors conduct research while paying attention to the state of the back surface (the other surface on which the photoelectric conversion layer is not stacked) of the CIGS solar battery cell. As a result, a “brittle layer” (corrosion layer of SUS substrate) that causes surface roughness of the back surface and poor electrical connection is generated during the deposition of Se in the compound semiconductor layer (CIGS photoelectric conversion layer) formation step. I found out. The Se layer on the back side is generated because Se has a lower melting point than other deposition materials and Se vapor pressure (vapor partial pressure) in the decompression chamber is high. It is thought that the reason is that it reaches the back side of the surface to be processed (vapor deposition) (so-called “backside”).

  Therefore, as a result of repeated trial production, the present inventors are less susceptible to the influence of the Se vapor on the back surface side of the long base material in advance (not easily eroded) before the production (evaporation) of the CIGS photoelectric conversion layer. ) It has been found that by forming a protective film made of a substance, the occurrence of the “brittle layer” (corrosion layer) can be suppressed, and the present invention has been achieved.

  According to the CIGS solar cell of the present invention and the manufacturing method thereof, molybdenum, tungsten, niobium, and tantalum, the other surface (back surface) opposite to the surface to be processed of the long base material hardly reacts with Se vapor. Since it is covered with a protective layer made of at least one metal selected from the group consisting of titanium or an alloy thereof having a thickness of 10 nm or more, even if it passes through a vacuum processing chamber having a high Se vapor concentration, The back surface of the scale substrate is not corroded by the Se vapor. As a result, the CIGS solar battery cell is not disturbed on its back surface even after the compound semiconductor layer (CIGS photoelectric conversion layer) formation step, and electrical connection between cells using solder, metal paste, or the like is long-lasting. It is maintained stably across. Therefore, the CIGS solar cell obtained by the CIGS solar cell of the present invention and the production method thereof can be a long-life solar cell excellent in appearance.

  In the present invention, a lower limit of 10 nm or more is provided in order to ensure the protective effect of the protective layer. In the protective layer having a thickness of less than 10 nm, the Se vapor penetrates through this layer, and the protective effect is not sufficient. In addition, the upper limit of the thickness of the protective layer is not particularly provided, but if it becomes too thick, the flexibility (flexibility) of the completed solar cell is impaired, and the layer thickness is thick (the amount of metal) In view of the point (cost) that the material cost increases as the amount increases, a thickness of about 50 nm to 10 μm is preferable.

It is typical sectional drawing explaining the structure of the CIGS photovoltaic cell of this invention. It is a schematic block diagram explaining the manufacturing process of the CIGS photovoltaic cell in 1st Embodiment of this invention. It is a schematic block diagram explaining the process of forming a metal protective layer in the back surface of a long base material in 2nd Embodiment of this invention. It is a schematic block diagram explaining the manufacturing process of a CIGS photovoltaic cell. It is a figure explaining the compound semiconductor layer formation (vapor deposition) process in the manufacturing process of a CIGS solar cell. It is typical sectional drawing of the conventional CIGS solar cell.

Next, an embodiment for carrying out the present invention will be described.
In each cross-sectional view to be referred to, each portion (layer) is schematically shown and is different from an actual thickness, size, and the like.

  As shown in FIG. 1, the CIGS solar cell according to the first embodiment of the present invention has a conductive long base (support) 1, back electrode layer 2, compound semiconductor film (in order from the lower side in the figure). The CIGS photoelectric conversion layer 3), the buffer layer 4 and the transparent conductive layer (surface electrode) 5 are formed by sequentially laminating in this order, and the basic configuration is the same as that of a conventional general solar battery cell. It is. The structural feature of the CIGS solar cell of this embodiment is that a protective layer P having a thickness of 10 nm or more, which is not in the conventional example, is formed on the back surface side (the lower side in the drawing) of the long base material 1. It is. The protective layer P was selected from the group consisting of molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta), and titanium (Ti) among the elements of groups 4 to 6 of the periodic table. It is composed of at least one metal or an alloy thereof, and prevents selenium (Se) vapor described later from penetrating into the long base material 1 and causing corrosion.

  As an example of the manufacturing method, as shown in the process diagram of FIG. 2, a decompression chamber 10 for forming the protective layer P is newly provided before (upstream side) the decompression chamber 12 of the previous proposal (FIG. 4). The protective layer P is formed on the other surface (non-processed surface) of the long base material 1 by sputtering or the like.

  Next, the configuration of the solar battery cell will be described in detail for each layer in the production order (stacking order). First, the long base material 1 serving as a production base is made of glass, polyimide, or the like as the material (material). Among these translucent base materials, ceramics such as silica alumina, and non-translucent metal base materials such as stainless steel (SUS) and titanium (Ti), a thin one (foil-like one) can be used. The long base material 1 can be made of any material or thickness as long as it can support the back electrode layer 2, the CIGS photoelectric conversion layer 3, the buffer layer 4, the transparent conductive layer 5 and the like described later in terms of structure and strength. Is not particularly limited. Moreover, the surface of those materials may be coated with a metal film, a transparent conductive film, an insulating film, or the like.

  A preferable thickness (total thickness) of the long base material 1 is 30 μm or more and 5 mm or less, and the SUS is suitably used in the present embodiment as a substrate material satisfying these required physical properties. Since this SUS is easy to be formed into a foil shape, it is suitable for forming a flexible photoelectric conversion device, and also has an appropriate strength even after forming a back electrode layer 2 and the like described later. It is more preferable because it is less warped, has excellent heat resistance, and is inexpensive. In the present embodiment, a long SUS substrate (foil) having a thickness of 50 μm is used.

  The protective layer P formed on the back surface side of the long base material 1 is formed over the entire surface on a different surface side from the formation surface (processing target surface) of the CIGS photoelectric conversion layer 3 and the like in the long base material 1. Yes. The protective layer P is usually formed by sputtering, but can be formed by other methods such as vacuum deposition, plating, aerosol deposition, and the like. Moreover, it can form by heat-rolling metal foil and joining or bonding. As described above, it is formed in a single layer or multiple layers made of at least one metal selected from the group consisting of Mo, W, Nb, Ta, and Ti or an alloy thereof.

  In addition, the protective layer P is different from the above steps in addition to the method of forming the protective layer P online in a vacuum consistently during the formation of each layer (but before vapor deposition of the photoelectric conversion layer) as in the first embodiment. You may employ | adopt the method (refer 2nd Embodiment mentioned later) etc. which are previously processed in the back surface of the elongate base material 1 at a process. Further, when the protective layer P is formed of a plurality of layers, the first layer formed so as to be in contact with the long base material 1 functions as an adhesive layer, so that the long base material 1 and the protective layer P are more It can be firmly adhered, which is preferable. Moreover, it is preferable from the point of adhesiveness to form the said protective layer P in the surface whose surface roughness is rough among the front and back both surfaces of the elongate base material 1. FIG.

  In consideration of the resistance to Se vapor, among the elements of Groups 4 to 6 in the periodic table, when the protective layer P is formed as a single layer, molybdenum (Mo) and titanium (Ti) are formed in a multilayer. When forming, lamination | stacking of Mo layer (outer surface layer) / Cr layer (underlayer which touches a base material) is selected suitably.

  And the said protective layer P is formed in thickness of 10 nm or more using said each method, Preferably it is formed in thickness of 10 nm-500 micrometers, More preferably, it is 10 nm-100 micrometers. The thickness of the protective layer P is determined in consideration of the resistance to Se vapor described later. When the thickness of the protective layer P is less than 10 nm, the penetration of Se vapor into the long substrate 1 is performed. There is a tendency that cannot be sufficiently prevented. On the other hand, when the thickness of the protective layer P exceeds 500 μm, the penetration preventing power against Se vapor is sufficient, but the flexibility (flexibility) of the CIGS solar cell after the completion of manufacture (lamination) is sufficient. In addition, handling during the cell production by the roll-to-roll process and the subsequent production of the solar cell module may be lowered, and the performance may be adversely affected.

Next, the back electrode layer 2 formed on the upper side of the long base 1 is made of a conductive material, such as Ti, Ni, Cr, Ag, Al, Cu, Au, Mo, or ITO. , ZnO, SnO _2, or the like can be used as a single layer or a plurality of laminated layers. Since the back electrode layer 2 plays a role as an electrode, it is preferable that the back electrode layer 2 has high electrical conductivity, and it is also possible to use a layer whose electrical conductivity is improved by adding a small amount of impurities. Among the back electrode materials, Mo (molybdenum) is preferably used because it has excellent adhesion to the CIGS photoelectric conversion layer 3 described later. As a method for forming the back electrode layer 2, methods such as CVD, vapor deposition, sol-gel method, spray method, electrodeposition method, and chemical deposition method are used in addition to the sputtering described above.

  Moreover, it is preferable that the back surface electrode layer 2 has an uneven shape on the surface (upper surface on the CIGS photoelectric conversion layer 3 side). By forming the concavo-convex shape on the surface of the back electrode layer 2, an improvement in the characteristics of the CIGS photoelectric conversion layer 3 due to a light scattering effect and an effect of preventing the CIGS photoelectric conversion layer 3 from peeling off can be expected. The thickness of the back electrode layer 2 is not particularly limited, but the total thickness is preferably 50 nm or more and 3 μm or less. In this embodiment, Cr and Mo are laminated in this order, and each film thickness is 400 nm (total thickness is 800 nm).

  The CIGS photoelectric conversion layer 3 laminated on the back electrode layer 2 contains at least Cu, In, Ga, and Se. As a method for forming the CIGS photoelectric conversion layer 3, in addition to the vapor deposition method described above, a sputtering method, a CVD method, a sol-gel method, a spray method, an electrodeposition method, and a chemical deposition method may be used alone or in combination. Can be used. Further, these forming methods and heat treatment can be used in combination.

  The CIGS photoelectric conversion layer 3 exhibits p-type conductivity, whereby a pn semiconductor junction can be formed between the CIGS photoelectric conversion layer 3 and a buffer layer 4 described later using an n-type semiconductor. Thereby, CIGS photoelectric conversion layer 3 expresses a photoelectric conversion function. The CIGS photoelectric conversion layer 3 may have a thickness that can sufficiently absorb light incident on the photoelectric conversion layer 3 and does not cause peeling, and is preferably 500 nm to 10 μm. is there. In the embodiment of the present invention, the thickness of the CIGS photoelectric conversion layer 3 is 3 μm.

  Next, the buffer layer 4 laminated on the CIGS photoelectric conversion layer 3 is composed of two layers of a layer made of CdS having a thickness of 50 nm and a layer made of ZnO having a thickness of 50 nm in the present embodiment. A high-resistance n-type semiconductor is preferably used so that a pn junction can be formed with the photoelectric conversion layer 3. As such a high-resistance n-type semiconductor, ZnMgO, Zn (O, S), ZnO, or the like can be used in addition to the above CdS and ZnO.

  Moreover, it is preferable that the thickness of the buffer layer 4 is 5-200 nm, and even if it is a case where the buffer layer 4 consists of a multilayer, it is preferable that each thickness is 5-200 nm. In addition, it is preferable to use a stack of a plurality of layers as the buffer layer 4 because the CIGS photoelectric conversion layer 3 and the pn junction can be improved. However, when the pn junction is sufficiently good, it is not always necessary to provide multiple layers.

  As the method for forming the buffer layer 4, in addition to the sputtering described above, for example, in vacuum, a molecular beam epitaxy method, an electron beam evaporation method, a resistance heating evaporation method, a plasma CVD method, an organometallic evaporation method, or the like is used. be able to. Further, atmospheric pressure plasma method or the like can be used in the atmosphere, and CBD method, electrolytic plating method or the like can be used in the aqueous solution.

Since the transparent conductive layer (surface electrode) 5 formed on the buffer layer 4 is located on the light incident side of the solar cell, a material having as high a light transmittance as possible is used. For example, ITO, tin oxide and oxide A single layer of a transparent conductive film such as zinc or a laminate of a plurality of layers is used. In addition, for the purpose of improving conductivity or adjusting the band alignment, those containing a small amount of a doping material in these materials are also preferably used. For example, Al: ZnO (AZO), B: ZnO (BZO), Ga: ZnO (GZO), Sn: In ₂ O ₃ (ITO), F: SnO ₂ (FTO), Zn: In ₂ O ₃ , Ti: In ₂ Oe, Zr: In ₂ O ₃ , W: In ₂ O _{3 and the} like are used.

  Moreover, since the transparent conductive layer 5 also plays a role of a conductive path for taking out carriers generated in the CIGS photoelectric conversion layer 3, it is preferable that the transparent conductive layer 5 has high electrical conductivity. From these viewpoints, ITO is particularly preferably used because it has both the property of easily crystallizing at room temperature formation and high electrical conductivity and good light transmission. From the viewpoint of light transmittance and electrical conductivity, the thickness of the transparent electrode is preferably 50 to 2000 nm. In the embodiment of the present invention, the thickness of the transparent conductive layer 5 is 200 nm.

  Although not shown, an extraction electrode is formed above the transparent conductive layer 5 using the same material and formation method as the back electrode layer 2. However, if the CIGS photoelectric conversion layer 3 (and the layers 4 and 5) are uniformly covered, light does not enter the photoelectric conversion layer 3 and the photoelectric conversion function does not appear. A grid shape (pattern shape) that does not cover the surface uniformly, such as a lattice shape, is preferable.

  Below, the method to manufacture the CIGS photovoltaic cell of the said structure by a roll to roll process is demonstrated. FIG. 2 is a schematic configuration diagram illustrating a manufacturing process (manufacturing apparatus) of the CIGS solar battery cell in the present embodiment.

  In this embodiment, as in the conventional example, the process of manufacturing the long CIGS solar cells is also arranged in a row so that the plurality of processing decompression chambers (11, 12, 13, 14) can be continuously processed. The substrate supply side decompression chamber X provided with an unwinding machine A for supplying a processing base material (ribbon-like long base material 1) to both ends thereof, and a post-processing A base material recovery side decompression chamber Y including a winder B that recovers and winds the long base material 1 is disposed. And in the manufacturing method of this embodiment, the decompression chamber 10 is newly provided before the decompression chamber 11 (line upstream side), and the protective layer P is formed in the back surface side of the elongate base material 1 there. This is a major feature.

The process (apparatus) for producing the long CIGS solar battery cell will be described in detail. Between the processing decompression chambers 10-14, the decompression chambers 10-14 are required between the processing decompression chambers 10-14. Differential exhaust devices Z ₁ , Z ₂ , Z ₃ , and Z ₄ for maintaining the pressure are respectively provided, and the long base material 1 is placed between processes (steps) that require different environmental pressures (atmospheres). It can be moved without interruption, and the processing and film formation (stacking) can be performed continuously.

  And each said decompression chamber for processing is the decompression chamber 11 for back electrode formation, the decompression chamber 12 for compound semiconductor layer formation from the unwinding machine A side [upstream side of a base material flow direction (white arrow)], The decompression chamber 13 for forming the buffer layer and the decompression chamber 14 for forming the transparent conductive layer are arranged in this order, and in this embodiment, the upstream side of the decompression chamber 11 for forming the back electrode (with the base material supply side decompression chamber X). In the middle), a decompression chamber 10 for forming a protective layer, which is not in the conventional example, is disposed. This is a feature of the CIGS solar cell manufacturing apparatus of the present embodiment. Below, each process is demonstrated in order of formation (lamination | stacking).

(A) Substrate supply step As shown in FIG. 2, the substrate supply step is wound around a reel or a roll using an unwinder A accommodated in the substrate supply side decompression chamber X. The ribbon-like long base material 1 is fed out to a predetermined position in each decompression chamber according to a guide roller or the like. The decompression chamber X communicates with a decompression chamber 10 for forming a protective layer, which will be described later, via a communication pipe or the like. In addition, a vacuum source (not shown) such as a vacuum pump installed separately is connected to the decompression chamber X so that the interior of the decompression chamber X is maintained at a predetermined pressure like the other decompression chambers. It has become.

  As the long base material 1 supplied from the base material supply step, a highly conductive metal base material such as stainless steel (SUS) or titanium (Ti) is used. The long base material 1 is in the form of a ribbon having a width of 5 to 30 mm and a length of 1 to 100 m (thickness of about 30 to 100 μm), and is wound around a reel or a roll that can be set on the unwinding machine A to prepare Is done. The long base material 1 has physical properties suitable for this manufacturing method (roll-to-roll process), such as flexibility and Young's modulus, which can withstand pulling in a high-temperature environment in the (d) compound semiconductor layer forming step described later. , Toughness, tensile strength, etc. are required.

(B) Protective layer formation process Next, the elongate base material 1 supplied from the unwinding machine A is introduced into the decompression chamber 10, and the other surface opposite to the surface to be processed (on the upper surface in FIG. 2). A protective layer (P) is formed by sputtering on the inner surface of the roll. In the decompression chamber 10, a first sputtering apparatus 20 (depot down type) that holds a material for forming a protective layer (target), and a guide roller for keeping the distance of the long base 1 to the target constant. In the state where the long substrate 1 is kept at a predetermined distance from the target holder (indicated by a dotted line in the figure) of the first sputtering apparatus 20. You can run.

  As the target material for forming the protective layer, as described above, at least one metal material selected from the group consisting of Mo, W, Nb, Ta, and Ti or an alloy material thereof is used. In a state where the pressure in the chamber 10 is reduced to 0.1 to 1.0 Pa, the long base 1 fed from the unwinding machine A is run under the first sputtering apparatus 20 and this long length is obtained by a DC sputtering method. A layer (thickness of about 100 to 1000 nm) made of the target material for forming the protective layer is continuously formed on the back surface (rolled inner surface of the roll) of the substrate 1.

  In the above example, the protective layer is formed as a single layer (single layer). However, if a plurality of sputtering devices are arranged in series along the flow of the base material in the decompression chamber 10, two or more layers are formed. It is also possible to produce a multilayer protective layer.

(C) Back surface electrode layer formation process The elongate base material 1 in which the protective layer was formed in the said back surface side then forms a photovoltaic cell in the process target surface at the surface (front) surface side. First, in the back electrode layer forming step, a back electrode (layer) is formed by sputtering on one surface of the long base material 1 (the lower surface in FIG. 2 is a wound outer surface of a roll) in the decompression chamber 11. In the decompression chamber 11, a base material such as a second sputtering device 21 that holds a material for forming the back electrode layer (target) and a guide roller for maintaining the distance of the long base material 1 to the target constant. Position stabilizing means (not shown) is arranged.

  As the target material for forming the back electrode layer, a metal material such as Mo, W, Cr, Ti or the like is used, and in the state where the inside of the decompression chamber 11 is decompressed to 0.6 to 1.0 Pa, a long base material is used. 1 is run on the second sputtering apparatus 21, and a layer (thickness of about 100 to 1000 nm) made of the target material for forming the back electrode layer is continuously formed on the surface of the long base 1 by DC sputtering. Form.

(D) Compound semiconductor layer forming step The compound semiconductor layer forming step is also described in the conventional method. In the decompression chamber 12, a plurality of materials (material layers) are sequentially deposited on the back electrode layer by vacuum deposition. It is a process of laminating and forming a compound semiconductor layer (CIGS photoelectric conversion layer).

In the decompression chamber 12, nozzles of a plurality of deposition sources for forming the compound semiconductor layer (four in this embodiment, 22 to 25. Note that the deposition apparatus main body may be installed outside the decompression chamber. And a substrate position stabilizing means (not shown) such as a guide roller for guiding the traveling position of the long substrate 1 is arranged, and as shown in FIG. 5 (conventional example), differential exhaust The elongate base material 1 introduced into the decompression chamber 12 via the apparatus Z ₃ is in a state (downward) in which the deposition target surface faces each nozzle of the deposition sources 22 to 25. It is comprised so that it can drive | work the position away from predetermined distance 25.

  In addition, the nozzle of each vapor deposition source 22-25 is provided with the height adjustment means which can control the distance with the elongate base material 1, respectively. The vapor deposition source is provided with a vapor deposition material, which will be described later, and a heater (not shown) for heating and evaporating the vapor deposition material. A shutter or the like is provided in each upper opening of the nozzle. Evaporation amount control means (not shown) is attached.

The vapor deposition method of the CIGS photoelectric conversion layer 3 in the decompression chamber 12 will be described in detail by taking a case of forming a thin film made of Cu (In, Ga) Se ₂ (CIGS compound) as an example. In the respective vapor deposition sources (22 to 25), Cu, In, Ga, and Se vapor deposition materials are sequentially set in accordance with the vapor deposition order (setting of other decompression chambers is also performed). When the deposition material setting is completed, the long base material 1 is inserted from the unwinder A to the winder B through the entire film forming apparatus through each decompression chamber, and all the working openings of the film forming apparatus are opened. A vacuum source (not shown) such as a vacuum pump that is closed and installed separately is operated to decompress the processing decompression chambers 10 to 14 and the decompression chambers X and Y for base material operation. Since the differential exhaust devices Z ₁ to Z ₄ described above are interposed between the decompression chambers, the pressure is individually controlled to a pressure of 1 Pa or less suitable for each processing.

  After the decompression of each decompression chamber is completed, when the long base material 1 is heated to 300 to 600 ° C. (550 ° C. or more in this example) in the decompression chamber X and the winder B is operated, the decompression chamber 10 (Protective layer forming step), 11 (Back electrode layer forming step) After the protective layer (P) is formed on the upper surface side and the back electrode layer (2) is formed on the lower surface side (after film formation) ) Is supplied to the decompression chamber 12, and is guided by a base position stabilizing means such as a guide roller, and travels an upper position that is a predetermined distance away from the nozzles of the respective vapor deposition sources 22 to 25. (See FIGS. 2 and 5).

  Further, in the decompression chamber 12, each vapor deposition material set in the vapor deposition sources 22 to 25 is heated to a temperature suitable for transpiration of the material by a heating means (not shown) provided in the vapor deposition source [for example, the first The deposition source (Cu) 1150 ° C., the second deposition source (In) 950 ° C., the third deposition source (Ga) 1000 ° C., the fourth deposition source (Se) 200 ° C.] The vapor sources 22 to 25 are filled with the vapor. And in the state which made the said long base material 1 with a back surface electrode layer run on the nozzle row | line | column of vapor deposition sources 22-25 along a guide roller etc., the shutter of each said vapor deposition source 22-25 is open | released. As a result, vapor particles (atoms, molecules) of the evaporation material heated and evaporated from the nozzles of the respective vapor deposition sources 22 to 25 are sequentially attached and deposited on the surface of the long base 1 that travels. A thin film (CIGS photoelectric conversion layer 3) made of a chalcopyrite compound is continuously formed on the lower surface (the surface of the back electrode layer).

The film thickness of the obtained CIGS photoelectric conversion layer (3) is preferably in the range of 1.5 to 3.0 μm from the viewpoint of the element characteristics of the solar battery cell. The elongate base material 1 after CIGS photoelectric conversion layer is formed on the back electrode layer, through the differential exhaust system Z _2, which are disposed between the vacuum chamber 12 vacuum chamber 13, It is transferred to a decompression chamber 13 (buffer layer forming step described later) that is controlled to an atmosphere (pressure) different from that of the decompression chamber 12.

  Here, in the conventional method (see FIG. 4), since the protective layer (P) is not formed on the back surface side of the long base material 1, the SUS base material (as the long base material 1) is used as in the present embodiment. When the foil is used, the Se gas present in the decompression chamber 12 corrodes the back surface of the long base material 1 (generates a selenium compound), and the back surface surface of the base material 1 as described above. The occurrence of a “brittle layer” that caused roughness and poor electrical connection was observed.

  On the other hand, in the manufacture of CIGS solar cells in the present embodiment, the back surface of the long base 1 is at least one metal selected from the group consisting of Mo, W, Nb, Ta, Ti, or Since it is covered with a protective layer (P, single layer or multiple layers) made of the alloy, the back surface of the substrate 1 does not directly contact the Se gas existing in the decompression chamber 12, and thus corrodes (selenium). Compound formation) is prevented. Therefore, the CIGS solar cells in this embodiment are less rough on the surface side (appearance) on the back surface side, and good adhesion of solder, metal paste, etc. to the back surface can be achieved. ), The electrical connection between the cells is stably maintained for a long time. Thereby, it can be set as a long-life solar cell (solar cell module).

  In the above example, one vapor deposition source is provided for one vapor deposition material. However, if a vapor deposition unit in which a plurality of vapor deposition sources is combined with one vapor deposition material, the three-stage method is used. A method that can form a higher quality compound semiconductor layer (CIGS photoelectric conversion layer) such as a bilayer method can also be employed.

(E) Buffer layer forming step In the subsequent buffer layer forming step, in the decompression chamber 13 on the one surface (lower surface) of the long substrate 1 via the decompression chamber 12 (compound semiconductor layer formation step), the above (c) A buffer layer (4) is formed by sputtering similar to the back electrode layer forming step. In the decompression chamber 13, a third sputtering apparatus 26 that holds a buffer layer forming material (target), and a substrate position such as a guide roller for maintaining the distance of the long substrate 1 to the target constant. Stabilizing means (not shown) is arranged so that the long base material 1 can run while maintaining a predetermined distance with respect to the target holder (indicated by a dotted line in the figure) of the third sputtering apparatus 26. It has become.

  As the target material for forming the buffer layer, a compound having n-type semiconductor characteristics is used. Specific examples thereof include zinc oxide compounds such as ZnO, (Zn, Mg) O, and Zn (O, S). Can be given. The buffer layer is formed by running the long base material 1 with the CIGS photoelectric conversion layer on the third sputtering device 26 in a state where the pressure in the decompression chamber 13 is reduced to 0.1 to 0.5 Pa, and by DC sputtering. A layer (thickness of about 5 to 200 nm) made of the target material for forming the buffer layer is continuously formed on the surface of the long base 1.

(F) Transparent conductive layer (surface electrode) forming step The next transparent conductive layer forming step is performed in the decompression chamber 14 on one surface (lower surface) of the long base material 1 via the decompression chamber 13 (buffer layer forming step). Thus, the transparent conductive layer (surface electrode) 5 made of a conductive oxide is formed by sputtering similar to the step (e) of forming the buffer layer. In the decompression chamber 14, a fourth sputtering device 27 that holds a material (target) for forming a transparent conductive layer, and a substrate such as a guide roller for maintaining the distance of the long substrate 1 to the target constant. Position stabilizing means (not shown) is arranged so that the long base material 1 can travel while maintaining a predetermined distance with respect to the target holder (indicated by a dotted line in the figure) of the fourth sputtering device 27. It has become.

  As the target material for forming the transparent conductive layer, a metal oxide having a light transmittance exceeding 80%, such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc aluminum oxide (Al: ZnO), or the like is used. In the state where the inside of the decompression chamber 14 is reduced to 0.1 to 0.5 Pa, the long base material 1 with the buffer layer is run on the fourth sputtering device 27, and this long base material 1 is obtained by the DC sputtering method. A transparent electrode layer (having a film thickness of about 50 to 200 nm) made of the target material for forming the transparent conductive layer is continuously formed on the surface.

(G) Base material recovery step The base material recovery step is a winder in which the long base material 1 (ribbon-like solar cells) after the formation of the transparent conductive layer is accommodated in the base material recovery side decompression chamber Y. Using B, it is wound around a reel or a roll and collected. Inside the decompression chamber Y, a winder B that can wind the long base material 1 at a predetermined speed (line speed), a guide roller that guides the traveling position of the long base material 1, and the like Is arranged. Since the decompression chamber Y communicates with the decompression chamber 14 for forming the transparent conductive layer through the connecting pipe, the internal pressure is the same as the decompression chamber 14 (0.1 to 0.5 Pa). ing.

  By passing through the above steps, a solar cell having a long shape (ribbon shape or strip shape) having a width of 5 to 30 mm (base material width) and a length of 1 to 100 m is obtained. In addition, the strip-shaped photovoltaic cell for solar cell module manufacture can be produced by cut | disconnecting this elongate photovoltaic cell to predetermined length (1 cm-10 m) in a base-material longitudinal direction.

  In addition, according to the above-described CIGS solar cell manufacturing method (apparatus), the base material and the base material after film formation are taken out from the apparatus (under reduced pressure) between the different formation processes such as the formation material and film formation conditions. There is no need, and there is no work of repeating the decompression-pressurization (opening to atmospheric pressure) of each decompression chamber 10 to 14, and there is no waiting time (loss time) between processes. Furthermore, there is no possibility that each thin film in the course of production will be oxidized by contact with the atmosphere (outside air) or impurities will adhere to the surface of the film. Thereby, the manufacturing method (apparatus) of the said CIGS photovoltaic cell can produce a high quality elongate photovoltaic cell efficiently.

  Next, a method in which the protective layer P on the back side of the long base material 1 is formed in a separate step in advance before another CIGS photoelectric conversion layer forming step will be described.

  FIG. 3 is a schematic configuration diagram illustrating a process of forming a metal protective layer on the back surface of the long base material in the second embodiment, and FIG. 4 is a CIGS photoelectric conversion layer forming process (described above) in the second embodiment. It is a figure explaining the method of a prior art example. In addition, the same code | symbol is attached | subjected to the structural member which has a function similar to a prior art example and 1st Embodiment, and the detailed description is abbreviate | omitted.

  The manufacturing method of the CIGS solar cell in the second embodiment of the present invention is different from the manufacturing method of the first embodiment in that the back surface side of the long base material 1 [formation surface of CIGS photoelectric conversion layer 3 and the like (surface to be processed) ) On the opposite surface side, and in the figure, on the inner (inner periphery) surface side of the base roll] the step of forming the metal protective layer P (FIG. 3) is another CIGS photoelectric conversion. Protection provided separately from the layer forming step (the decompression chamber 11 for forming the back electrode, the decompression chamber 12 for forming the compound semiconductor layer, the decompression chamber 13 for forming the buffer layer, and the decompression chamber 14 for forming the transparent conductive layer) The point is that it is performed by sputtering (depot up method) in the decompression chamber 10 'for layer formation.

  The decompression chamber 10 ′ for forming the protective layer has an equal pressure with the decompression chambers X ′ and Y ′ between the base material supply step (the decompression chamber X ′) and the base material recovery step (the decompression chamber Y ′). Each decompression chamber 10 ′, X ′, Y ′ is maintained at a predetermined pressure by a vacuum source (not shown) such as a separately installed vacuum pump. In FIG. 3, symbol A ′ denotes an unwinder for suspending a ribbon-like long base material 1 wound around a reel or a roll, and symbol B ′ denotes a long length after processing (protection layer P formation). The winding machine which winds and collect | recovers the base material 1 (with the protective layer P on the winding inner surface) on a reel or a roll etc. is shown.

  Further, in the decompression chamber 10 ′, a sputtering apparatus 20 ′ (depot up type) for holding a protective layer forming material (target) and a guide for keeping the distance of the long substrate 1 to the target constant. A base material position stabilizing means (not shown) such as a roller is disposed, and the long base material 1 is kept at a predetermined distance from the target holder (indicated by a dotted line in the figure) of the sputtering apparatus 20 ′. It can be run by.

  As the target material for forming the protective layer, as in the first embodiment, at least one metal material selected from the group consisting of Mo, W, Nb, Ta, and Ti or an alloy material thereof is used. In a state where the inside of the decompression chamber 10 ′ is depressurized to 0.1 to 1.0 Pa, the long base material 1 fed from the unwinding machine A ′ is run on the sputtering apparatus 20 ′, and by DC sputtering method, On the lower surface of the long substrate 1 (winding inner surface of the roll), a layer (thickness of about 100 to 1000 nm) made of the target material for forming the protective layer is continuously formed. Wind again in a roll.

  In addition, as the long base material 1, as in the first embodiment, the long base material 1 (width 5 to 30 mm, length 1 to 100 m, thickness used in the CIGS photoelectric conversion layer forming step (FIG. 4) described later. A ribbon-like SUS substrate having a thickness of about 30 to 100 μm is preferably used. Moreover, although the example which forms the single layer (one layer) of the protective layer P was shown in the said example, if a several sputtering apparatus is arrange | positioned in series along the flow of a base material in the decompression chamber 10, it will be two or more layers. It is also possible to produce a multilayer protective layer.

  Next, using the long base material 1 on which the protective layer P is formed on the back surface (rolled inner surface of the roll), CIGS photoelectric conversion layer formation similar to that of the first embodiment is formed as shown in the configuration diagram of FIG. By passing through the steps [(c) back electrode layer forming step, (d) compound semiconductor layer forming step, (e) buffer layer forming step, (f) transparent conductive layer (surface electrode) forming step], the width is 5 to 30 mm. (Substrate width) A long (ribbon or strip) solar cell having a length of 1 to 100 m can be obtained.

  Also in the manufacturing method of the CIGS solar battery cell of the second embodiment, the back surface of the long base material 1 (the surface opposite to the formation surface (processing target surface) of the CIGS photoelectric conversion layer 3 and the like) is the Mo, W , Nb, Ta, Ti are covered with a protective layer (P, single layer or multiple layers) made of at least one kind of metal selected from the group consisting of Nb, Ta, Ti, or an alloy thereof. Corrosion (generation of selenium compound) is prevented without directly touching Se gas present in the compound semiconductor layer forming step (decompression chamber 12). Therefore, the CIGS solar cell in this embodiment also has a rough surface state (appearance) on the back side of the base material, and adhesion of solder, metal paste, etc. to the back side is good. Even when modularized, electrical connection between cells is stably maintained for a long time. Thereby, it can be set as a long-life solar cell (solar cell module).

  Next, examples will be described together with comparative examples. However, the present invention is not limited to this.

  An example product and a comparative product prepared a long SUS base material (SUS430: manufactured by JFE Steel Co., Ltd.) having a width of 15 mm and a thickness of 50 μm, and using the manufacturing apparatus described in the above embodiment (FIG. 2), A roll-to-roll process produced a CIGS solar cell (test sample) that was consistent in vacuum and never taken out of the apparatus during the process (formation process). These series of steps were performed at a processing speed (line speed) of 1 m / min (common to each example and each comparative example).

  In addition, the obtained long CIGS solar cell has a long shape while observing the surface state of the back surface (substrate side) of the test product by visual observation and performing sensory evaluation on its “appearance (roughness)”. A plurality of strip-shaped solar cells obtained by cutting the cells at a certain length are connected side by side and connected (electrically connected), and then both sides are sandwiched between EVA and glass and laminated to form a set of solar cells. A module was produced. And "series resistance component Rs" was calculated | required from the voltage-current characteristic under sunlight (pseudo-light) of this solar cell module by calculation.

  Next, the solar cell module after the above measurement was subjected to 10 cycles of a thermal cycle test (endurance test) in which the module was repeatedly exposed to an environment of -45 ° C. and + 80 ° C. (1 cycle). The same “series resistance component Rs” was measured again, and the rate of change (function reduction rate) with respect to that before the durability test (initial value) was obtained by calculation and evaluated. Furthermore, the module after the thermal cycle test (endurance test) was disassembled, and it was evaluated by visual inspection and palpation whether there was any abnormality in the electrical connection part (solder part) between the cells in each test sample.

[Example 1]
By the manufacturing method described in the second embodiment, in the decompression chamber 10 ′, the back surface of the long SUS substrate (FIG. 3, the lower surface in the apparatus, the wound inner surface of the roll) is thickened as a protective layer by sputtering. A 50 nm thick Mo (molybdenum) layer was formed. Subsequently, the long SUS base material is set in a processing apparatus (see FIG. 4), and is passed through the decompression chambers 11, 12, 13, and 14 in this order. ) A back electrode layer, a CIGS photoelectric conversion layer, a buffer layer, and a surface electrode layer are successively formed (laminated) in this order on the surface (rolling outer surface of the roll) side, and a completed long CIGS solar cell is obtained. It was wound up on a roll. The processing conditions for each step are as follows.

-Back electrode layer In the decompression chamber 11 decompressed to 0.8 Pa, first, a Cr layer having a thickness of 300 nm is first formed by sputtering, and then a Mo layer having a thickness of 300 nm is continuously formed. A back electrode layer was formed.

CIGS photoelectric conversion layer In the decompression chamber 12 set to a pressure of 1 × 10 ⁻³ Pa and an indoor temperature of 550 ° C., the molar composition ratio of Cu, In, Ga, and Se using Cu, In, Ga, and Se as an evaporation source However, a CIGS photoelectric conversion layer having a thickness of 2.2 μm was formed so that Cu / (Ga + In) ≈0.85, Ga / (Ga + In) ≈0.3.

Buffer layer A buffer layer having a thickness of 100 nm was formed by sputtering using Zn (O, S) (ZnO 80 wt%, ZnS 20 wt%) as a material in the decompression chamber 13 decompressed to 0.2 Pa.

・ Transparent conductive layer (surface electrode)
In the decompression chamber 14 decompressed to 0.4 Pa, a transparent conductive layer having a thickness of 200 nm was formed by sputtering using ITO as a material.

[Example 2]
A W (tungsten) layer having a thickness of 50 nm was formed as a protective layer by sputtering on the back surface (rolled inner surface of the roll) of the long SUS substrate in the decompression chamber 10 ′ using the above manufacturing apparatus. Except for the above, a long CIGS solar cell of Example 2 was produced in the same manner as in Example 1 above.

Example 3
Other than forming a 50 nm thick Nb (niobium) layer as a protective layer by sputtering on the back surface (rolling inner surface of the roll) side of the long SUS substrate in the decompression chamber 10 ′ using the above manufacturing apparatus. In the same manner as in Example 1, the long CIGS solar battery cell of Example 3 was produced.

Example 4
Using the above manufacturing apparatus, a Ta (tantalum) layer having a thickness of 50 nm was formed as a protective layer on the back surface (rolling inner surface of the roll) side of the long SUS substrate by sputtering in the decompression chamber 10 ′. Except for the above, a long CIGS solar cell of Example 4 was produced in the same manner as in Example 1 above.

Example 5
Using the above manufacturing apparatus, a 50 nm thick Ti (titanium) layer was formed as a protective layer on the back surface (rolled inner surface of the roll) side of the long SUS substrate by sputtering in the decompression chamber 10 ′. Except for the above, a long CIGS solar cell of Example 5 was produced in the same manner as in Example 1 above.

Example 6
Using the above manufacturing apparatus, a Cr (chromium) layer having a thickness of 50 nm is formed as a protective layer on the back surface (rolled inner surface of the roll) side of the long SUS substrate by the two sputtering devices in the decompression chamber 10 ′. The same as in Example 1 except that a multi-layer protective layer composed of a (underlying layer in contact with the substrate) and a 50 nm thick Mo (molybdenum) layer (outer surface layer) laminated thereon was formed. Thus, a long CIGS solar battery cell of Example 6 was produced.

[Comparative Example 1]
Using the conventional manufacturing apparatus shown in FIG. 4, except that no processing was performed on the back surface (rolled inner surface of the roll) of the long SUS substrate (the protective layer was not formed), In the same manner as in Example 1, a long CIGS solar battery cell of Comparative Example 1 was produced.

[Comparative Example 2]
Using the manufacturing apparatus described in the above embodiment (FIG. 2), a 5 nm thick protective layer is formed by sputtering on the back surface (rolling inner surface of the roll) of the long SUS substrate in the decompression chamber 10 ′. A long CIGS solar cell of Comparative Example 2 was produced in the same manner as in Example 1 except that the Mo (molybdenum) layer was formed.

[Comparative Example 3]
Using the manufacturing apparatus described in the embodiment (FIG. 2), a 50 nm thick protective layer is formed by sputtering on the back surface (rolling inner surface of the roll) of the long SUS substrate in the decompression chamber 10 ′. A long CIGS solar cell of Comparative Example 3 was produced in the same manner as in Example 1 except that a Cu (copper) layer was formed.

[Manufacture of solar cell modules]
After confirming the surface state of the back surface (substrate side) of each obtained long CIGS solar cell, this was cut at a fixed length (in this example, length 100 mm, width 15 mm), and the obtained strip-shaped sun Seven battery cells were connected to each other to produce a 100 mm square solar battery module. In addition, the electrical connection between the cells is first performed in advance on both end edges along the longitudinal direction of the cell of the transparent conductive layer (surface electrode) by a vacuum deposition method [multilayer [Cu layer (upper surface side) / Cr layer (surface Electrode), each having a width of 1 mm and a thickness of 100 nm], and then a protective layer formed on the back side of the substrate 1 (including the case of no protective layer and protective layer in the comparative example) Connection portions by solder were formed at both edge portions along the cell longitudinal direction. And the overlap width of the take-out electrode (Cu layer part) on the surface of one strip-shaped solar battery cell and the connection part (solder part) of another strip-shaped solar battery cell arranged adjacent (arranged) The long sides of each strip solar cell are aligned so that the thickness is 1 mm, and in this state, the connecting portion is heated at 230 ° C. for 30 seconds, and the above-described solder solar cells are melted and fixed. The cells were electrically connected (the same applies when soldering directly to the back surface of the SUS substrate without the protective layer).

<Measurement of series resistance component Rs>
Twenty solar cell modules were prepared for each of the examples and comparative examples, and using a solar simulator (Cell Tester, Yamashita Denso Co., Ltd., YSS-150), simulated sunlight (AM1.5) was 100 mm. Irradiation was performed so that the irradiation area was equal to or greater than the corner (module size), and the series resistance component Rs was obtained by calculation from the voltage-current characteristics (graph) of the module obtained during irradiation. Measurement is performed once before and after the thermal cycle test (endurance test) in which the module is alternately exposed to the environment of -45 ° C. and + 80 ° C. 10 times, and the rate of change (function deterioration rate) is calculated. Comparing. In addition, those having an increase rate of 10% or less were evaluated as “good”, and those having an increase rate exceeding 10% were evaluated as “bad”.

  In addition, in “Table 1” showing the experimental results, the “photoelectric conversion efficiency η” of the module obtained during the measurement of the “series resistance component Rs” [during irradiation with pseudo sunlight (AM1.5)], and this The change rate before and after the thermal cycle test (endurance test) of the photoelectric conversion efficiency η is described as a reference value.

<Evaluation of the appearance of the back of the substrate>
After the production of the long CIGS solar cells (before the module production), the surface state of the back surface (substrate side) of the specimen was observed, and the “appearance (surface roughness)” was evaluated. In the evaluation, the case where the state of the back surface was flat and not disturbed was judged as “good”, and the case where the surface was rough such as swelling or peeling was judged as “bad”.

<Evaluation of electrical connection part (solder part) between cells>
After the above thermal cycle test (endurance test), disassemble the solar cell module, apply force by hand to the electrical connection (solder part) between the strip-shaped solar cells, and check if there is no separation between the connections It was confirmed. In the evaluation, “good” indicates that peeling does not occur between the connection portions (solder portions) even when a force is applied (solder portion), and “bad” indicates that peeling easily occurs when a force is applied.

  The results of the above evaluations are summarized in “Table 1” below.

  From the above results, the solar cell module using the CIGS solar cells of Examples 1 to 6 using the long base material (SUS) in which the protective layer is formed in advance has the series resistance component Rs before and after the thermal cycle test. The rate of change and the rate of change of the reference value “photoelectric conversion rate η” were each 10% or less, and it was proved that the solar cell module was excellent in durability (weather resistance). On the other hand, in the solar cell module using the CIGS solar cells of Comparative Examples 1 to 3, the change rate of the series resistance component Rs (and the reference value “photoelectric conversion rate η”) is more than 10%. In addition to the above, it was found that an appearance abnormality that can be visually confirmed occurred on the back surface of the base material and the connection portion.

  The CIGS solar cell of the present invention has a long life and can be used in various environments.

DESCRIPTION OF SYMBOLS 1 Long base material 2 Back surface electrode layer 3 CIGS photoelectric conversion layer 4 Buffer layer 5 Transparent conductive layer P Protective layer

Claims (2)

  A back electrode layer, a CIGS photoelectric conversion layer, a buffer layer, and a surface electrode composed of a transparent conductive layer are sequentially laminated on one surface of a long conductive substrate using a roll-to-roll process. CIGS solar battery cell, wherein at least one selected from the group consisting of molybdenum, tungsten, niobium, tantalum, and titanium among elements of groups 4 to 6 of the periodic table is formed on the other surface of the long base material. A CIGS solar cell, wherein a protective layer made of a metal or an alloy thereof and having a thickness of 10 nm or more is formed. A step of forming a back electrode layer on the surface of the conductive long base material, a step of forming a CIGS photoelectric conversion layer on the exposed surface of the back electrode layer, and a buffer on the exposed surface of the CIGS photoelectric conversion layer A step of forming a layer and a step of forming a surface electrode made of a transparent conductive layer on the exposed surface of the buffer layer, and each layer is sequentially applied to one surface side of the long substrate by a roll-to-roll process. It is a manufacturing method of the CIGS solar cell to laminate,
Prior to the step of forming the CIGS photoelectric conversion layer, the other surface of the long substrate is selected from the group consisting of molybdenum, tungsten, niobium, tantalum, and titanium among the elements of groups 4 to 6 of the periodic table. A method for producing a CIGS solar cell, comprising forming a protective layer made of at least one metal or an alloy thereof having a thickness of 10 nm or more.