JPWO2012015026A1 - Solar cell substrate and manufacturing method thereof - Google Patents

Abstract

An object of this invention is to provide the solar cell substrate which can manufacture the solar cell which has flexibility at low cost, and its manufacturing method. The solar cell substrate of the present invention is a film-like solar cell substrate having a fine concavo-convex structure on the surface thereof, and is formed of a synthetic resin. .3 to 3 μm.

Description

  The present invention generally relates to a substrate for a solar cell and a method for manufacturing the same, and more particularly, to a solar cell having a fine concavo-convex structure, flexibility and structure controllability, and capable of being manufactured at low cost. The present invention relates to a substrate and a manufacturing method thereof.

In recent years, solar power generation using solar cells has attracted attention as a power generation system with a low environmental load. Currently, a solar cell panel using a glass substrate is common as a solar cell.
However, glass is fragile and dangerous. Further, since the glass itself is heavy, for example, when a solar cell panel using a glass substrate is attached to the roof, it is necessary to reinforce the roof. Furthermore, it was difficult to reduce the cost of the glass substrate.

  Therefore, recently, a movement to replace the glass substrate of the solar cell panel with a substrate made of a film-like base material is active.

The substrate of a film-like base material is hard to break and safe, and can be reduced in weight by being greatly reduced in thickness. Further, the cost can be reduced by increasing the area and processing by roll-to-roll.
Furthermore, since a solar cell using a film-like substrate is flexible, it can be attached to a curved surface.

  In general, in a solar cell, on a substrate, a transparent electrode made of a metal oxide such as zinc oxide, tin oxide, and indium tin oxide, and a photoelectric conversion layer selected from amorphous silicon, crystalline silicon, metal oxide, and the like, It is formed with a back surface reflective electrode selected from gold, silver, copper, palladium, aluminum, titanium and the like, and in this order (referred to as a super straight type) or reverse order (referred to as a substrate type).

  In particular, solar cells using amorphous silicon for the photoelectric conversion layer are attracting attention because they can be reduced in thickness and cost. A dry process is generally used as a manufacturing process of a solar cell using amorphous silicon. In this dry process, a transparent electrode is formed on a substrate by sputtering to produce a substrate with a transparent electrode, an amorphous silicon photoelectric conversion layer is then formed by CVD (chemical vapor deposition), and the back surface The reflective electrode is formed by sputtering.

  Here, in the solar cell, the shape of the interface between the photoelectric conversion layer and the transparent electrode is related to the photoelectric conversion efficiency. That is, when the shape of the interface between the photoelectric conversion layer and the transparent electrode is a shape that easily scatters light, the received light can be efficiently photoelectrically converted by the photoelectric conversion layer. Therefore, it is desirable that the interface between the photoelectric conversion layer and the transparent electrode has an appropriate surface roughness. According to such a structure, scattering occurs when light enters the photoelectric conversion layer from the transparent electrode, the optical path length in the photoelectric conversion layer is increased, and the photoelectric conversion efficiency in the photoelectric conversion layer is increased.

  As a method of making the interface between the photoelectric conversion layer and the transparent electrode easy to scatter light, an active energy ray-curable resin composition is placed on a glass plate-like support having a fine uneven structure on the surface. Furthermore, a film-like base material is laminated on the active energy ray-curable resin composition, and the active energy ray-curable resin composition is irradiated with active energy rays through the film-like base material or the plate-like support to activate the active energy. A method for forming a transparent electrode on a film-like substrate and a texture layer by curing a linear curable resin composition to form a texture layer and then peeling the plate-like support from the texture layer has been proposed. (For example, Patent Document 1).

JP 2008-177549 A

  However, since the substrate for solar cells disclosed in Patent Document 1 uses a plate-like support when forming a fine concavo-convex structure, it can cope with processing by roll-to-roll. Therefore, it was difficult to manufacture at a low cost.

  This invention is made | formed in such a condition, and it aims at providing the board | substrate for solar cells which can manufacture a flexible solar cell at low cost, and its manufacturing method.

According to the present invention,
A film-like solar cell substrate having a fine relief structure on the surface,
The fine concavo-convex structure formed of a synthetic resin has a local peak sum average interval S of a roughness curve of 0.3 to 3 μm.
A substrate for solar cells is provided.

  By using such a solar cell substrate, a flexible solar cell can be manufactured at low cost.

  According to another preferred aspect of the present invention, the fine concavo-convex structure has a root mean square slope RΔq of a roughness curve of 14 to 30 degrees.

  According to another preferable aspect of the present invention, the fine concavo-convex structure has a load length ratio Rmr (50%) of a roughness curve at a cutting level of 50% of 0.2 to 0.5.

  According to another preferred embodiment of the present invention, the fine concavo-convex structure is an irregular fine concavo-convex structure having an acute angle.

  The solar cell is a thin film silicon solar cell having a substrate type structure.

According to another aspect of the invention,
A method for manufacturing a solar cell substrate, comprising:
A mold having an uncured active energy ray-curable resin composition formed on a surface thereof by blasting and having a fine concavo-convex structure with a local peak-top average spacing S of 0.3 to 3 μm, and a film-like transparent substrate A step sandwiched between and
The active energy ray-curable resin composition is irradiated with active energy rays through the film-like transparent substrate to cure the active energy ray-curable composition and complement the fine uneven structure on the surface of the mold. Forming a typical microstructure in the film-like translucent substrate;
Peeling the film-like translucent substrate from the mold, and
A method for manufacturing a solar cell substrate is provided.

According to another preferred embodiment of the invention,
The mold is a roll mold.

According to another aspect of the invention,
A step of forming a fine concavo-convex structure having a local peak-top average interval S of a roughness curve of 0.3 to 3 μm by performing a blast treatment on the film-shaped substrate;
A method for manufacturing a solar cell substrate is provided.

According to another preferred embodiment of the invention,
Blast particles used for the blasting process are polygonal.
According to another preferred embodiment of the present invention, the blast particles have a particle size of 5 to 35 μm at a cumulative height of 50% in the particle size distribution.
According to another preferred embodiment of the invention,
The blast particles have a maximum particle size in the particle size distribution of 80 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate for solar cells which can manufacture the solar cell which has flexibility at low cost, and its manufacturing method are provided.

It is a typical fragmentary sectional view which shows the structure of the board | substrate 1 for 1st solar cells of this invention. It is a typical perspective view for demonstrating the manufacturing method of the roll metal mold | die used when manufacturing the board | substrate 1 for solar cells of FIG. It is drawing which shows typically the board | substrate manufacturing apparatus which manufactures the board | substrate for solar cells of FIG. 1 using the roll-shaped metal mold | die shown in FIG. It is a fragmentary sectional view showing typically the composition of the substrate for solar cells of a 2nd embodiment of the present invention. It is a model figure of the solar cell substrate of 1st Embodiment of this invention used in a two-dimensional RCWA simulation.

  Next, a solar cell substrate according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional view showing the configuration of the first solar cell substrate 1 of the present invention.

  The solar cell substrate 1 of this embodiment is a solar cell substrate suitable for a thin film silicon solar cell having a substrate type structure. In addition, when using the solar cell substrate 1 of this embodiment for a thin film silicon solar cell having a super straight type structure, light passes through the solar cell substrate 1 and enters the photoelectric conversion layer. It is preferable that the fine unevenness | corrugation shape mentioned later is provided in both surfaces.

  As shown in FIG. 1, the solar cell substrate 1 includes a film-like translucent substrate 2 and a texture layer 4 laminated on the film-like translucent substrate 2 and having a fine uneven structure. ing. FIG. 1 shows a back reflective electrode film 6 made of a metal layer covering the texture layer 4. In the present embodiment, the fine concavo-convex structure of the texture layer is formed by transferring a fine concavo-convex structure formed by blasting to the mold surface, as will be described later.

  When a substrate type thin film solar cell is formed using the solar cell substrate 1 of the present embodiment, a photoelectric conversion layer is formed on the back surface reflective electrode film 6, and a transparent electrode film is further formed thereon. Good. The solar cell substrate 1 of the present embodiment has a texture layer 4 having a fine relief structure on the surface. Therefore, when the back surface reflective electrode film 6, the photoelectric conversion layer, and the transparent electrode film are formed on the texture layer 4, these components are formed in a shape that follows the fine concavo-convex structure of the texture layer 4.

  In the case of forming a super straight type thin film solar cell using the solar cell substrate 1 of this embodiment, a transparent electrode film may be formed on the texture layer 4 and a photoelectric conversion layer and a back surface reflective electrode film may be sequentially laminated. . In the case of a super straight type thin film solar cell, since sunlight enters from the solar cell substrate 1, the surface on which the texture layer 4 is provided in order to suppress reflection when sunlight enters the substrate 1; It is preferable that an antireflection mechanism such as a fine concavo-convex structure is provided on the opposite surface.

  In addition, when using for a super straight type thin film solar cell, since the substrate 1 for solar cells is directly exposed to sunlight, it is necessary to use a resin composition having weather resistance for the substrate 1 for solar cells. Various restrictions will arise in manufacture of the board | substrate 1 for solar cells. Therefore, the solar cell substrate 1 of the present embodiment is preferably used for a substrate type thin film solar cell.

  The film-like translucent substrate 2 constituting the solar cell substrate 1 of the present embodiment is a synthetic resin film-like substrate excellent in heat resistance and ultraviolet transmissivity. By using a film-like translucent substrate having excellent heat resistance, it is possible to form a film at a high temperature when forming a metal or metal oxide as an electrode material. Moreover, by using a film-like base material excellent in ultraviolet transmittance, the texture layer 4 using the active energy ray-curable composition can be formed as described later.

Examples of the material of the film-like translucent substrate 2 used for the solar cell substrate 1 of the present embodiment include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polymethyl methacrylate (PMMA). Acrylic resins such as diacetyl cellulose and triacetyl cellulose, styrene resins such as polystyrene (PSt) and acrylonitrile / styrene copolymer (AS), polyethylene (PE), polypropylene (PP), cyclic Or polyolefin resin having norbornene structure and olefin resin such as ethylene / propylene copolymer (EP), polyamide resin such as nylon and aromatic polyamide (PA), polycarbonate (PC) resin, vinyl chloride resin (PVC) , Polymethacrylimide (PMI) resin And the like.
Among these, polyethylene naphthalate, polyolefin, and polymethyl methacrylate are preferable from the viewpoint of heat resistance.

The thickness of the film-like translucent substrate 2 is preferably 10 to 300 μm, more preferably 20 to 200 μm, and particularly preferably 30 to 100 μm from the viewpoints of strength and workability.
In order to improve the adhesion with the texture layer 4 made of the active energy ray-curable composition, it is preferable to subject the surface of the film-like translucent substrate 2 to an adhesion improving treatment such as an anchor coat treatment.

  Moreover, it is preferable that the thermal deformation temperature of the film-form translucent base material 2 is 150 degreeC or more, It is preferable that it is 180 degreeC or more especially 200 degreeC or more. If the heat distortion temperature is too low, when the metal oxide film is formed at a high temperature in the subsequent process, the substrate swells, the metal oxide cracks, and the sheet resistance may increase remarkably. The upper limit of the heat distortion temperature is usually 500 ° C.

  The texture layer 4 having a fine concavo-convex structure of the present embodiment preferably has a thickness of 0.1 to 100 μm, particularly 0.2 to 50 μm, and more preferably 0.3 to 30 μm in terms of photoelectric conversion efficiency. It is preferable that

  If the thickness of the texture layer 4 is too thin, the uneven structure of the texture layer 4 may not be sufficiently transferred to the boundary between the photoelectric conversion layer and the transparent electrode, which may make it difficult to improve the photoelectric conversion efficiency. When the solar cell substrate is bent, the texture layer 4 is cracked, which may deteriorate the photoelectric conversion efficiency.

  Moreover, it is preferable that the local peak top average space | interval S (JIS B0601 (94)) of the roughness curve in the fine concavo-convex structure of the solar cell substrate 1 of this embodiment is 0.3 to 3 μm, particularly 0.6 to 2. 0.5 μm, more preferably 1 to 2 μm is preferable.

  When S is outside the above range, light scattering is not sufficiently generated at the boundary between the photoelectric conversion layer and the transparent electrode of the solar cell in which the solar cell substrate 1 is used, and the photoelectric conversion efficiency can be increased. I can't.

  Further, the root mean square slope RΔq (JIS B0601 (01)) of the roughness curve in the fine concavo-convex structure of the solar cell substrate 1 of the present embodiment is preferably 14 to 30 degrees, more preferably 15 to 30 degrees, and 16 to 16 degrees. 30 degrees is more preferable.

  If RΔq is too small, light scattering cannot be caused sufficiently and the photoelectric conversion efficiency cannot be increased. On the other hand, if RΔq is too large, crystal grain boundaries are generated when the photoelectric conversion layer is formed, and the photoelectric conversion efficiency cannot be increased.

  Furthermore, in the fine uneven structure of the solar cell substrate 1 of the present embodiment, the load length ratio Rmr (50%) (JIS B0601 (01)) of the roughness curve at a cutting level of 50% is 0.2 to 0.5. It is preferable that it is preferably 0.25 to 0.45, more preferably 0.3 to 0.4. If Rmr (50%) is too small or too large, the light scattering effect cannot be sufficiently exhibited.

  In the solar cell substrate 1 of this embodiment, a back reflective electrode film 6 made of metal is formed on a texture layer 4 having a fine concavo-convex structure of a film-like translucent substrate 2.

  The metal used for the back surface reflective electrode film 6 is preferably one having high reflectivity in the visible to infrared region and high conductivity, including one metal selected from Ag, Au, Al, Cu and Pt, or these It is preferable to form with an alloy. A dry process is used as a method of forming the back reflective electrode film 6.

  In order to further improve the reflectivity, it is desirable to form a transparent electrode film on the back reflective electrode film 6 by a dry process.

  When the solar cell substrate 1 is used for a super straight type solar cell, a transparent electrode film made of a metal oxide is formed on the texture layer 4 having a fine concavo-convex structure of the film-like translucent substrate 2. .

  Metal oxides used for transparent electrode films are single metal oxides such as zinc oxide, tin oxide, indium oxide and titanium oxide, and various metal oxides such as indium tin oxide, indium zinc oxide, indium titanium oxide and tin cadmium oxide. And doping metal oxides such as gallium-doped zinc oxide, aluminum-doped zinc oxide, boron-doped zinc oxide, titanium-doped zinc oxide, titanium-doped indium oxide, zirconium-doped indium oxide, and fluorine-doped tin oxide.

  Among these, gallium-doped zinc oxide, aluminum-doped zinc oxide, or boron-doped zinc oxide is preferable from the viewpoint of low resistivity.

Next, a method for manufacturing the solar cell substrate 1 of the present embodiment will be described.
First, the roll metal mold | die used with the manufacturing method of this embodiment is demonstrated. The roll mold is a cylindrical roll mold. The roll mold is manufactured by processing a roll-shaped metal member whose outer peripheral portion is made of a metal such as chromium, nickel, stainless steel (SUS), copper, aluminum, brass, or steel.

FIG. 2 is a schematic perspective view for explaining a method for manufacturing a roll mold.
The roll mold is manufactured by processing a roll-shaped metal member having at least an outer peripheral portion made of a metal such as chromium, nickel, stainless steel (SUS), copper, aluminum, brass, or steel.

  Specifically, as shown in FIG. 2, the roll-shaped metal member 10 is supported such that the rotation axis (rotation center) thereof is horizontal, and the rotation of the roll-shaped metal member 10 is provided above the roll-shaped metal member 10. A nozzle (blast nozzle) 12 of the blasting device is arranged so as to be reciprocally movable in parallel with the axis. The blast nozzle 12 is disposed toward the rotation axis A of the roll-shaped metal member 10.

  While the roll metal member 10 is continuously rotated around the rotation axis, the blast nozzle 12 is slowly moved along the rotation axis A of the roll metal member 10 while the roll metal member 10 is moved from the blast nozzle 12. The blast particles 14 are sprayed toward the outer peripheral surface of the.

By moving the blast nozzle 5 from one end to the other end in the axial direction of the roll-shaped metal member 10, the entire outer peripheral surface of the roll-shaped metal member 10 was subjected to blasting, and a fine uneven structure was formed on the outer peripheral surface. A roll mold 14 is obtained.
This fine concavo-convex structure is such that the texture layer 4 of the solar cell substrate 1 has a dimension and shape complementary to the fine concavo-convex structure.

  The blast particles used in this blasting process are abrasive fine particles having a particle size at a 50% cumulative height of 5 to 35 μm, preferably 7 to 20 μm, more preferably 10 to 15 μm.

If the particle size of the abrasive fine particles is too small, the blasting energy is weak and the surface of the metal member is difficult to process, and it becomes impossible to obtain a fine concavo-convex structure for expressing uniform and sufficient light scattering.
On the other hand, if the particle size of the abrasive fine particles is too large, the pitch of the formed irregularities becomes large and light scattering cannot be expressed.

  For the same reason, the abrasive fine particles have a maximum particle size in the particle size distribution of 80 μm or less, preferably 60 μm or less, more preferably 40 μm or less. When compared between abrasive particles having the same particle diameter, a non-spherical shape can form a fine uneven structure having a shorter uneven pitch and a deeper depth than a spherical shape.

  For the reasons described above, the particle size of the abrasive fine particles cannot be reduced to a predetermined value or more, and therefore it is preferable to use non-spherical abrasive fine particles in order to reduce the pitch of the concavo-convex structure.

For the same reason, the abrasive fine particles are more preferably irregular particles having an acute angle such as an angular shape such as a polyhedral shape. The material of the abrasive fine particles is not particularly limited, but for example, Al ² O ³ , SiC, ZrO ² , SiO ² or the like is preferably used.

  Next, a method for manufacturing the solar cell substrate 1 using the roll mold 14 will be described. FIG. 3 is a drawing schematically showing a substrate manufacturing apparatus 20 that manufactures the solar cell substrate 1 using the roll-shaped mold 14.

  As shown in FIG. 3, in the substrate manufacturing apparatus 20, the long film-like translucent substrate 2 is wound around the outer peripheral surface of a roll-shaped mold 14 that is driven to rotate in the direction of arrow B. However, it is configured to be conveyed in the direction of arrow C. As described above, a fine concavo-convex structure is formed on the outer peripheral surface of the roll-shaped mold 14 by blasting.

  The roll-shaped mold 14 is supplied with the film-shaped translucent base material 2 along the outer peripheral surface thereof, that is, the surface having a fine uneven structure, and the roll-shaped mold 14 and the film-shaped translucent base are supplied. Between the material 2, the active energy ray-curable composition 22 that forms the texture layer 4 is continuously supplied from the resin tank 24 via the nozzle 26.

The active energy ray curable resin is not particularly limited as long as it is cured with active energy rays such as ultraviolet rays and electron beams.
Examples thereof include polyesters, epoxy resins, polyester (meth) acrylates, epoxy (meth) acrylates, (meth) acrylate resins such as urethane (meth) acrylates, and the like. A (meth) acrylate resin is particularly preferable from the viewpoint of its optical characteristics and the like.

  The active energy ray-curable composition 22 used for such a cured resin is also described as a polyfunctional acrylate and / or a polyfunctional methacrylate (hereinafter referred to as a polyfunctional (meth) acrylate) in terms of handleability and curability. ), Monofunctional acrylates and / or methacrylates (hereinafter also referred to as mono (meth) acrylates), and photopolymerization initiators based on active energy rays are preferred.

  Typical polyfunctional (meth) acrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These are used alone or as a mixture of two or more. Moreover, as mono (meth) acrylate, (meth) acrylic acid ester of monoalcohol, (meth) acrylic acid ester of polyol, etc. are mentioned. In particular, the texture layer 4 is preferably made of a synthetic resin containing polyfunctional acrylate as a main component.

The photopolymerization initiator is not particularly limited as long as it can generate radicals by irradiation with active energy rays, and various photopolymerization initiators can be used.
For example, benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,6-dimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide and the like can be mentioned.

  In particular, when polyethylene naphthalate is used as the film-like translucent substrate 2, 2,4,6-trimethylbenzoyldiphenylphosphine is selected among them because of the balance between the wavelength that can be transmitted through the substrate and the absorption spectrum of the photopolymerization initiator. It is particularly preferred that it contains an oxide. These photopolymerization initiators may be used alone or in combination of two or more.

These photopolymerization initiators are (meth) acrylate compounds (when a monofunctional (meth) acrylate compound is contained, the sum of polyfunctional (meth) acrylate compounds and monofunctional (meth) acrylate compounds) 100 weights It is preferably used at a ratio of 0.1 to 10 parts by weight with respect to parts, more preferably 0.2 to 5 parts by weight, and particularly preferably 0.2 to 3 parts by weight.
If the amount used is too small, the polymerization rate will decrease and the polymerization will not proceed sufficiently. If it is too large, the light transmittance of the resulting texture layer 4 will tend to decrease (yellowing), and the mechanical strength will be low. There is a tendency to decrease.

Moreover, you may use a thermal polymerization initiator together with a photoinitiator.
Known compounds can be used as the thermal polymerization initiator.
For example, hydroperoxide such as hydroperoxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide Dialkyl peroxides such as t-butyl peroxybenzoate, peroxyesters such as t-butylperoxy (2-ethylhexanoate), diacyl peroxides such as benzoyl peroxide, and peroxycarbonates such as diisopropyl peroxycarbonate And peroxides such as peroxyketal and ketone peroxide.

  A nip roll 28 is disposed in the vicinity of the supply position of the active energy ray-curable composition 22 of the roll-shaped mold 14. The nip roll 28 is operated by the pressure mechanism 30 to press the film-like translucent substrate 2 and the active energy ray-curable composition 22 against the outer peripheral surface of the roll-shaped mold 14.

  By the pressing by the nip roll 28, the supplied active energy ray-curable composition 22 spreads with a uniform thickness between the film-shaped translucent substrate 2 and the outer peripheral surface of the roll-shaped mold 14. As the nip roll 28, a metal roll, a rubber roll, or the like is used.

  Moreover, in order to make the thickness of the active energy ray-curable composition 22 uniform, those processed with high accuracy with respect to the roundness, surface roughness, etc. of the nip roll 28 are preferable. A rubber having a high hardness of 60 degrees or more is preferable.

  As the pressure mechanism 30, a hydraulic cylinder, a pneumatic cylinder, various screw mechanisms, and the like can be used, but a pneumatic cylinder is preferable from the viewpoint of simplicity of the mechanism. The air pressure is controlled by a pressure regulating valve or the like.

  The active energy ray-curable composition 22 supplied between the roll-shaped mold 14 and the film-like translucent substrate 2 is kept at a constant viscosity in order to make the thickness of the texture layer 4 obtained constant. It is preferred that In general, the viscosity range is preferably in the range of 20 to 3000 mPa · S, and more preferably in the range of 100 to 1000 mPa · S.

  By setting the viscosity of the active energy ray-curable composition 22 to 20 mPa · S or more, it is necessary to set the nip pressure extremely low or to extremely increase the molding speed in order to make the thickness of the texture layer 4 constant. Disappears.

  When the nip pressure is extremely low, the pressure mechanism cannot be stably operated, and the thickness of the light-transmitting thin film is not constant. In addition, when the molding speed is extremely increased, the irradiation amount of the active energy ray is insufficient, and the active energy ray curable composition 22 is not sufficiently cured.

On the other hand, by setting the viscosity of the active energy ray-curable composition 22 to 3000 mPa · S or less, the curable composition can be sufficiently distributed to the details of the shape transfer surface structure of the roll-shaped mold 14, and the uneven structure. This makes it difficult to accurately transfer the film, to easily generate defects due to mixing of bubbles, or to deteriorate productivity due to an extremely low molding speed.
For this reason, in order to keep the viscosity of the active energy ray-curable composition 22 constant, a sheathed heater, hot water is provided outside or inside the resin tank 24 so that the temperature of the active energy ray-curable composition 22 can be controlled. It is preferable to install a heat source facility such as a jacket.

  An active energy ray irradiation device 32 is provided downstream of the nip roller 28 in the conveyance direction. In the present embodiment, the active energy ray irradiating device 32 is curable with the active energy ray that is disposed between the film-like translucent substrate 2 and the roll-shaped mold 14 via the film-like translucent substrate 2. It arrange | positions so that the composition 22 may be irradiated from the radial direction outer position of the outer peripheral surface of the roll-shaped metal mold 14 through the film-form translucent base material 2. FIG.

As the active energy ray irradiation device 32, a chemical reaction chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a visible light halogen lamp, or the like is used. For the active energy ray, for example, the integrated energy in the wavelength range of 200 to 600 nm, preferably 320 to 390 nm is, for example, 0.1 to 10 J / cm ² , preferably 0.5 to 8 J / cm ^2. It is appropriate to irradiate. Moreover, as irradiation atmosphere of an active energy ray, inert gas, such as air or nitrogen, argon, is mentioned.

With such a configuration, after the active energy ray-curable composition 22 is supplied between the outer peripheral surface of the roll-shaped mold 14 and the film-like film-like translucent substrate 2, the active energy ray-curable composition 22 is supplied. Is irradiated between the roll-shaped mold 14 and the film-shaped translucent substrate 2 by irradiating active energy rays from the active energy beam irradiation device 12 through the film-shaped translucent substrate 2, The energy ray-curable composition 22 is polymerized and cured, and the fine concavo-convex structure formed on the outer peripheral surface of the roll mold 14 is transferred.
Next, by releasing the solar cell substrate 1 having a fine concavo-convex structure composed of the film-like translucent substrate 2 and the texture layer 4 formed of the active energy ray-curable resin 22 from the roll-shaped mold 14, The solar cell substrate 1 having the texture layer 4 having a fine concavo-convex structure having an acute angle such as an angular shape can be obtained. The solar cell substrate 1 released from the roll mold 14 is conveyed in the downstream direction.

  On the solar cell substrate 1 formed in this way, the back reflective electrode film 6 or the transparent electrode is formed.

  The back surface reflective electrode film 6 is generally formed by laminating a reflective electrode film made of Ag or the like and a transparent electrode film. As a method for forming the reflective electrode film and the transparent electrode film on the solar cell substrate 1, a conventionally known dry process may be used. The thickness of each of the reflective electrode film and the transparent electrode film is preferably in the range of 5 nm to 5000 nm. When the thickness of the reflective electrode film is less than 5 nm, it is difficult to form a reflective electrode film having a uniform thickness following the fine uneven shape of the solar cell substrate 1. Moreover, when thickness exceeds 5000 nm, it will become difficult to form the reflective electrode film which followed the fine uneven | corrugated shape of the board | substrate 1 for solar cells.

  In addition, as a dry process said here, a sputtering method, CVD method, a vapor deposition method, etc. are mentioned. In forming the metal or metal oxide, it is preferable to use a sputtering method from the viewpoint of adhesion to the texture layer 2. More preferably, the electrode film is formed on the solar cell substrate 1 at a low temperature such as low-temperature sputtering.

  According to such a method for manufacturing a solar cell substrate 1 having a fine concavo-convex structure, the solar cell substrate 1 having a fine concavo-convex structure can be continuously formed using the roll-shaped mold 14, and Since the durability is high, product yield and productivity are improved, and manufacturing costs can be reduced.

  Further, in this method, since the shape transfer surface of the roll-shaped mold 14 is formed by blasting, an optimal fine concavo-convex structure for expressing light scattering can be formed on the solar cell substrate 1 at low cost and accurately. Can be formed continuously.

  Next, the solar cell substrate 40 of the second embodiment of the present embodiment will be described.

  FIG. 4 is a partial cross-sectional view schematically showing the configuration of the solar cell substrate 40 of the second embodiment of the present invention. As shown in FIG. 4, the solar cell substrate 40 includes a film-like base material 42 having a fine concavo-convex structure formed on the surface, and an electrode layer 44 made of a metal or metal oxide.

  In this embodiment, since the film-like base material 42 does not require ultraviolet light transmission, polyimide or the like can be used in addition to the base material that can be used in the first embodiment. Polyimide is particularly suitable because of its excellent heat resistance.

In the solar cell substrate 40 of the present embodiment, the fine concavo-convex structure is formed by blasting the film-like base material 42.
The dimensional shape of the fine concavo-convex structure on the surface of the solar cell substrate 40 of the second embodiment is substantially the same as the dimensional shape of the fine concavo-convex structure of the texture layer 4 of the solar cell substrate 1 of the first embodiment.

Next, the process of forming a fine concavo-convex structure on the film substrate 42 will be described.
First, the raw film-like base material 42 is fixed to the surface of the metal plate with a double-sided tape or the like. Examples of the metal plate used at this time include plates of chromium, nickel, stainless steel (SUS), copper, aluminum, brass, steel, and the like.

Next, the nozzle (blast nozzle) of the blasting device is disposed so as to be capable of reciprocating in parallel with the surface of the film-like substrate 42. The blast nozzle is oriented perpendicular to the surface of 44 on the film substrate.
Next, while moving the blast nozzle relative to the film-like substrate 42, blast particles are sprayed toward the surface of the film-like substrate 42 to form a fine uneven structure on the surface of the film-like substrate 42.
The blast particles are the same as those used in the first embodiment.

  An electrode layer 46 made of metal or metal oxide is formed on the surface of the solar cell substrate 40 thus manufactured by the same method as in the first embodiment.

  In this specification, “(meth) acrylate” is a general term for acrylate and methacrylate, and “(meth) acryl” is a general term for acrylic and methacrylic.

  The present invention is not limited to the above-described embodiment, and various changes or modifications can be made within the scope of the matters described in the claims.

  Examples of the present invention will be described below.

  A roll-shaped metal member obtained by applying a copper plating of a thickness of 300 μm to the outer peripheral surface of a roll-shaped iron member having a diameter of 200 mm and a length of 580 mm and further applying a nickel plating of a thickness of 0.5 μm to prevent copper oxidation. Rotate continuously around the rotation axis at a rotation speed of 40 times per minute.

  While rotating the roll-shaped metal member, blasting treatment was performed by discharging blast particles from a blast nozzle as shown in FIG. In this blasting process, a blast nozzle having a discharge port diameter of 7 mmφ is disposed at a position 200 mm away from the surface of the roll-shaped metal member, and the blast nozzle is moved at a speed of 0.2 mm / second in the rotation axis direction of the roll-shaped metal member. Polygonal alumina particles having a particle size distribution at a 50% cumulative height of 13 to 15 μm and a maximum particle size of 38 μm or less toward the rotation center of the roll-shaped metal member (made by Showa Denko KK, trade name Morundum A # 800).

  The discharge pressure of blast particles was 0.5 MPa. The blast particles discharged from the blast nozzle 5 reach the surface of the roll-shaped metal member with a certain spread, but the spread of the blast particles when reaching the surface is about 54 mm. This obtained the roll-shaped metal mold | die which has a fine uneven structure in an outer peripheral surface.

Next, as shown in FIG. 3, a roll mold and a rubber nip roll are arranged adjacent to each other in parallel, and a PEN film having a thickness of 100 μm (trade name: Teonex Q65FA, manufactured by Teijin DuPont Films Ltd.) is formed between them. A translucent substrate was supplied along the roll mold.
The translucent substrate was nipped between the rubber nip roll and the roll mold by a pneumatic cylinder connected to the rubber nip roll. When the spectral transmittance of the PEN film used here was measured using a spectrophotometer (trade name Hitachi spectrophotometer U-4100, manufactured by Hitachi High-Technologies Corporation), the transmittance of light having a wavelength of 400 nm was 80.0%. there were.

  On the other hand, the following ultraviolet curable composition 8 phenoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name biscoat # 192): 50 parts by weight bisphenol A-diepoxy-acrylate (manufactured by Kyoeisha Yushi Chemical Co., Ltd., trade name epoxy ester 3000A) ): 50 parts by weight Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (trade name Irgacure 819, manufactured by BASF): Viscosity of 300 mPa · S by adjusting the temperature to 25 ° C. It was adjusted.

  This ultraviolet curable composition was supplied to one surface of the translucent base material nipped by the rubber nip roll to the roll-shaped metal mold | die. While rotating the roll-shaped mold, the ultraviolet curable composition is sandwiched between the roll-shaped mold and the translucent substrate and irradiated with ultraviolet light from an ultraviolet irradiation device, and the ultraviolet curable composition is The fine concavo-convex structure on the shape transfer surface of the roll mold was transferred by polymerization and curing. Thereafter, the mold was released from the roll mold to obtain a solar cell substrate having a fine concavo-convex structure.

  When measured using an atomic force microscope (manufactured by Keyence Corporation, trade name Nanoscale Hybrid Microscope VN-8010), the local peak-top average interval S of the roughness curve in the fine uneven structure of the solar cell substrate 7 is 1.1 μm, The root mean square slope RΔq was 17.2 degrees, and the load length ratio Rmr (50%) of the roughness curve at a cutting level of 50% was 0.43. The cut-off wavelength used for analysis of these roughness parameters is 25 μm.

The film-like translucent substrate having a fine concavo-convex structure was cut into 5 cm square, and then mounted on a sputtering apparatus, and the inside of the sputtering machine was evacuated to 10 ⁻⁴ Pa. Next, Ar was introduced as a sputtering gas from the gas inlet, and the pressure was maintained at 1 Pa.

  Next, a direct current power source was applied to the Ag target, and an Ag layer was laminated to 200 nm on the film-like translucent substrate 7 having a fine concavo-convex structure. Furthermore, using an Al-containing ZnO target, 40 nm of Al-containing ZnO was laminated in the same manner.

  The substrate was further laminated with a Si layer of 2 μm and an ITO layer of 70 nm to form a substrate-type thin film silicon solar cell, and the photoelectric conversion efficiency was estimated by two-dimensional RCWA simulation when both surfaces were sealed with EVA. . As a simulation software, DiffractMOD Ver. 3.2 (R-Soft Design Group) was used.

As shown in FIG. 5, the shape of the solar cell substrate is assumed to be a prism shape having a node at a prism height of 50%, and the value of the local summit average interval S is used as the pitch P. The inclination angle θ _{1 is} such that the prism width D at the node is the product of S and the load length ratio Rmr (50%) of the roughness curve at the cutting level of 50%, and the root mean square inclination RΔq is the same as the actually measured value. And θ ₂ , tan θ ₁ = tan (RΔq) × √ (Rmr (50%) / (1-Rmr (50%))) tan θ ₂ = tan (RΔq) × √ ((1-Rmr (50% )) / Rmr (50%)).

  It was assumed that Ag (200 nm), ZnO (40 nm), Si (2 μm), and ITO (70 nm) were laminated in this order with respect to the substrate shape, and each thin film grew in a vertical direction from the prism side and concentrically from the apex. In addition, the space further outside the ITO layer was filled with EVA.

  In such a system, using the aforementioned local peak average interval S1.1 μm, root mean square slope RΔq17.2 degrees, load length ratio Rmr (50%) 0.43 of the roughness curve at cutting level 50%, respectively. A two-dimensional RCWA simulation was performed, and the absorptance at each wavelength when light having a wavelength of 360 to 1100 nm was vertically incident was calculated. Multiplying this with the “photon number spectrum” obtained by multiplying the AM1.5G spectrum by each wavelength and the conversion rate of the absorbed photons to electrons in the substrate type thin film silicon solar cell and integrating them, the photoelectric conversion efficiency is increased. I was able to estimate.

  When compared with the same simulation performed when the tilt angle is 0 degree (when there is no unevenness and is flat), the photoelectric conversion efficiency was estimated to be 1.35 times.

(Examples 2 to 5)
Except that the type of blast particles and the discharge pressure were changed, a fine uneven structure was formed on the outer peripheral surface of the roll mold in the same manner as in Example 1, and a solar cell substrate was prepared using an ultraviolet curable composition. Measurement and estimation of photoelectric conversion efficiency were performed.
The results are shown in Table 1. The blast particles in Example 2 were polygonal alumina particles (manufactured by Showa Denko KK, trade name Morundum A # 1200). In Example 3, polygonal alumina particles (manufactured by Showa Denko KK, trade name Morundum A # 1500) were used. In Examples 4, 5, and 6, polygonal alumina particles (manufactured by Showa Denko KK, trade name Morundum A # 400) were used. In Example 7, spherical ceramic particles (manufactured by Saint-Gobain, trade name Zilblast B-505) were used.

(Example 8)
A polyimide film (product name: Kapton H type, manufactured by Toray DuPont Co., Ltd.) with the same shape and thickness is fixed to a SUS plate with a square thickness of 3 mm on a side of 200 mm with double-sided tape. Blasting was performed by discharging. In this blasting process, a blast nozzle having a discharge port diameter of 7 mmφ is arranged at a position 220 mm away from the surface of the polyimide film, and the same amorphous alumina particles as in Example 1 (Showa Denko) are scanned toward the polyimide film while scanning the entire surface of the polyimide film. Product name Morundum A # 800).

  The blast nozzle scan was based on a reciprocating motion, and was scanned with an interval of 0.6 mm between the return and return. Subsequently, the next scanning line was further scanned with an interval of 0.6 mm, and the return scanning was similarly performed with an interval of 0.6 mm. The entire surface of the polyimide film was scanned with this repetition. Thereby, the base material for solar cells which has a fine uneven structure was obtained.

  When measured in the same manner as in Example 1, the local peak-top average interval S of the roughness curve in the fine uneven structure of the solar cell substrate was 1.5 μm, the root mean square slope RΔq was 14.5 degrees, and the cutting level was 50%. The load length ratio Rmr (50%) of the roughness curve was 0.59. The cut-off wavelength used for analysis of these roughness parameters is 25 μm.

  Next, using an Ag target and an Al-containing ZnO target, an Ag layer having a thickness of 200 nm and an Al-containing ZnO layer having a thickness of 40 nm were sequentially stacked in the same manner as in Example 1. When the photoelectric conversion efficiency was estimated by the same two-dimensional RCWA simulation as in Example 1, it was 1.23 times that when there was no unevenness.

1: Solar cell substrate 2: Film-like translucent base material 4: Texture layer 6: Back surface reflective electrode film 10: Metal member 12: Blast nozzle 14: Roll mold

Claims (11)

A film-like solar cell substrate having a fine relief structure on the surface,
The fine concavo-convex structure formed of a synthetic resin has a local peak sum average interval S of a roughness curve of 0.3 to 3 μm.
A solar cell substrate characterized by that. The fine concavo-convex structure has a root mean square slope RΔq of a roughness curve of 14 to 30 degrees.
The solar cell substrate according to claim 1. The fine uneven structure has a load length ratio Rmr (50%) of a roughness curve at a cutting level of 50% of 0.2 to 0.5.
The solar cell substrate according to claim 1 or 2.   4. The solar cell substrate according to claim 1, wherein the fine concavo-convex structure is an irregular fine concavo-convex structure having an acute angle. 5. The solar cell is a thin film silicon solar cell having a substrate structure.
The solar cell substrate according to any one of claims 1 to 4. A method for manufacturing a solar cell substrate, comprising:
A mold having an uncured active energy ray-curable resin composition formed on a surface thereof by blasting and having a fine concavo-convex structure with a local peak-top average spacing S of 0.3 to 3 μm, and a film-like transparent substrate A step sandwiched between and
The active energy ray-curable resin composition is irradiated with active energy rays through the film-like transparent substrate to cure the active energy ray-curable composition and complement the fine uneven structure on the surface of the mold. Forming a typical microstructure in the film-like translucent substrate;
Peeling the film-like translucent substrate from the mold, and
The manufacturing method of the solar cell substrate characterized by the above-mentioned. The mold is a roll mold,
The manufacturing method of the board | substrate for solar cells of Claim 6. A step of forming a fine concavo-convex structure having a local peak-top average interval S of a roughness curve of 0.3 to 3 μm by performing a blast treatment on the film-shaped substrate;
The manufacturing method of the solar cell substrate characterized by the above-mentioned. The blast particles used for the blasting process are polygonal,
The manufacturing method of the board | substrate for solar cells of any one of Claim 6 thru | or 8. The blast particles have a particle size of 5 to 35 μm at a cumulative height of 50% in the particle size distribution.
The manufacturing method of the board | substrate for solar cells of Claim 9. The blast particles have a maximum particle size in a particle size distribution of 80 μm or less.
The manufacturing method of the board | substrate for solar cells of any one of Claims 8 thru | or 10.