JP2011129288A - Substrate with transparent conductive film and thin film photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate with a transparent conductive film wherein a base layer and a transparent conductive film are formed on the substrate in this order, and a photoelectric conversion device having high conversion efficiency. <P>SOLUTION: In the substrate with a transparent conductive film, the transparent conductive film is constituted with a plurality of transparent electrode layers formed by a chemical vapor deposition method. When forming the plurality of transparent electrode layers, a next layer is formed after stopping film deposition by vacuum-exhausting a film deposition chamber after making film deposition of each layer when continuously forming under a pressure-reduced atmosphere. Or, after once stopping the film deposition by taking out the substrate under atmospheric pressure, the next layer is film-deposited under the pressure-reduced atmosphere by again supplying to the film-deposition chamber. A new crystal nucleus is generated on a texture formed by once stopping crystal growth, and the most suitable surface unevenness shape for a thin-film photoelectric conversion device can be formed by forming a new texture from the new crystal nucleus on the basis of these methods. Consequently, the thin-film photoelectric conversion device which can restrain reduction of voltage and a curvilinear factor while retaining short-circuit current density and has high power generation efficiency can be attained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides means capable of improving the conversion efficiency of a thin film photoelectric conversion device, and particularly relates to improvement of a transparent conductive film in a thin film photoelectric conversion device.

  In recent years, in order to achieve both cost reduction and high efficiency of a photoelectric conversion device, a thin film photoelectric conversion device having almost no problem in terms of resources has been attracting attention and has been vigorously developed. A thin film silicon solar cell, which is one of the thin film photoelectric conversion devices, can be formed on a glass substrate or a stainless steel substrate having a large area at a low temperature. In order to improve the conversion efficiency of this thin-film silicon solar cell, conventionally, as a method for increasing the amount of absorption of sunlight, contrivance has been made to increase the optical path length of light incident on the photoelectric conversion layer.

For example, in the case of a thin-film silicon solar cell using a glass substrate, a tin oxide (SnO ₂ ) film, which is a transparent electrode, is formed by a thermal CVD method to form various textures, and the surface of the transparent electrode is etched. Thus, a method of forming a concavo-convex structure or a method of increasing the scattering of incident light by forming a layer having a concavo-convex structure between a transparent electrode and a glass substrate is performed. On the other hand, if the concavo-convex structure of the transparent electrode is steep in shape or has protrusions on the surface, defects will occur in the subsequent power generation layer, or leakage current will occur due to short circuit with the electrode layer, resulting in the output of the solar cell Decreases. Therefore, it is important to form a surface shape in which the voltage and fill factor do not decrease while maintaining the scattering characteristics. For example, in Patent Document 1, a silicon layer is formed after the transparent electrode layer is formed, and defects are generated in the power generation layer by smoothing the surface by etching the protrusion protruding on the surface of the silicon layer. Short circuit with the electrode layer is suppressed. However, in this method, etching is performed after forming the p layer and the n layer, which are part of the active layer of the solar cell, which causes defects such as scratches and contamination on the surface of the silicon layer. The film quality of the power generation layer is reduced. In addition, not only the protrusions but also the height and steepness of the concavo-convex structure cannot be changed by this method, so it cannot be said to be an effective method. Further, in Patent Document 2, the transparent electrode layer is formed into a multilayer, thereby suppressing the overall variation in film thickness and surface unevenness. However, since the formation of each layer is continuous, a partially steep uneven portion is formed. It cannot be said that it is a particularly effective method for improving the above.

JP 2001-352081 A JP 2004-323321 A

The present invention solves the above-described problems of the prior art, increases the optical path length of light incident on the photoelectric conversion layer, increases the current, and does not decrease the voltage and fill factor, with a transparent conductive film A substrate and a thin film photoelectric conversion device are obtained.

The present invention relates to the following.
(1) In a substrate with a transparent conductive film in which a base layer and a transparent conductive film are formed in this order on a substrate, the transparent conductive film is composed of a plurality of transparent electrode layers formed by a CVD method under a reduced pressure atmosphere. The manufacturing method of the board | substrate with a transparent conductive film characterized by these.
(2) The plurality of transparent electrode layers are continuously formed in a reduced-pressure atmosphere, and after the formation of each transparent electrode layer, the film formation is stopped by vacuum evacuation to form the next layer. The manufacturing method of the board | substrate with a transparent conductive film as described in (1) characterized by the above-mentioned.
(3) When the film formation is stopped, the degree of vacuum is 3 × 10 ⁻³ Pa or less, and the substrate temperature is 100 ° C. or less. With the transparent conductive film according to (2) A method for manufacturing a substrate.
(4) The plurality of transparent electrode layers are taken out under atmospheric pressure after forming each transparent electrode layer, and the next layer is formed again under a reduced pressure atmosphere. A method for producing a substrate with a transparent conductive film.
(5) In the plurality of transparent electrode layers, the SDR (surface area ratio) after forming each layer is smaller in the (n + 1) th layer than in the nth layer (1) to (1) The manufacturing method of the board | substrate with a transparent conductive film in any one of 4).
(6) The method for producing a substrate with a transparent conductive film according to any one of (1) to (5), wherein at least one of the plurality of transparent electrode layers contains zinc oxide.
(7) The base layer is formed by transferring a concavo-convex structure of a matrix formed by etching a single crystal silicon substrate to the base layer by a nanoimprint technique (1) to ( The manufacturing method of the board | substrate with a transparent conductive film in any one of 6).
(8) The method for manufacturing a substrate with a transparent conductive film according to any one of (1) to (7), wherein the base layer is formed of silicon oxide.
(9) A substrate with a transparent conductive film, which is formed by the production method according to any one of (1) to (8).
(10) On the substrate with a transparent conductive film according to any one of (1) to (9), at least one amorphous silicon photoelectric conversion unit, crystalline silicon photoelectric conversion unit, and back electrode layer from the light incident side. A thin film photoelectric conversion device, which is sequentially stacked.

  In the present invention, in a substrate with a transparent conductive film in which an underlayer and a transparent conductive film are formed in this order on a substrate, the transparent conductive film is composed of a plurality of transparent electrode layers formed by a CVD method under a reduced pressure atmosphere. In the case of forming the plurality of transparent electrode layers described above, in the case of continuously forming in a reduced pressure atmosphere, after the deposition of each layer, the deposition chamber is evacuated to completely stop the deposition, and then the next layer Form. Alternatively, after film formation of each layer, the substrate is once taken out under atmospheric pressure, and again put into the film formation chamber, and film formation is performed under a reduced pressure atmosphere. When the film formation is stopped by these methods, the crystal growth is temporarily stopped. Therefore, a new crystal nucleus is generated on the texture formed on the surface of the transparent electrode layer, and a new texture is grown therefrom to form a thin film. An uneven surface shape optimal for the photoelectric conversion device is formed. Therefore, a decrease in voltage and fill factor can be suppressed while maintaining light scattering characteristics such as short-circuit current density, and as a result, a thin film photoelectric conversion device having high power generation efficiency can be obtained.

It is sectional drawing of the board | substrate with a transparent conductive film of 1 aspect of this invention. It is sectional drawing of the board | substrate with a transparent conductive film of 1 aspect of this invention. It is explanatory drawing of SDR of this invention. 1 is a schematic cross-sectional view of a two-junction thin film silicon solar cell (thin film photoelectric conversion device) according to one embodiment of the present invention. It is an AFM image of the board | substrate with an uneven structure which concerns on Example 1 of this invention. It is an AFM image of the board | substrate with an uneven structure which concerns on Example 3 of this invention. It is TEM sectional drawing of the thin film photoelectric conversion apparatus which concerns on Example 1 of this invention.

  The present invention relates to "a substrate with a transparent conductive film in which a base layer and a transparent conductive film are formed in this order on a substrate, wherein the transparent conductive film is composed of a plurality of transparent electrode layers formed by a CVD method under a reduced pressure atmosphere. The manufacturing method of the board | substrate with a transparent conductive film characterized by being ".

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views of a substrate with a transparent conductive film according to the present invention. As shown in FIG. 1, the substrate 4 with a transparent conductive film in the present invention is such that a base layer 2 and a transparent conductive film 3 are formed in this order on a substrate 1.

  As the substrate 1, a translucent insulating substrate can be preferably used, and among them, a plate-like member or a sheet-like member made of glass or transparent resin is preferably used.

For the underlayer 2, for example, when transferring the concavo-convex shape of the mold (mold) by the nanoimprint method, an inorganic sol-gel material or an organic-inorganic hybrid material to which a metal oxide such as titanium or an alkoxide is added is used. Although inorganic sol-gel materials can be used, a sol-gel material made of SiO ₂ is particularly preferable because it has a high transmittance and a small light absorption loss, similar to glass.

As the sol-gel material made of SiO _2, specifically, a spin-on glass (SOG) material or the like can be used. Among them, it is preferable to use a material mainly composed of tetraalkoxysilane or alkylalkoxylane.

  When a glass substrate is used as the substrate 1, for example, a dipping method, a spin coat method, a bar coat method, a spray method, a die coat method, a roll coat method, a flow coat is used as a method for forming the base layer on the glass substrate. In order to form easily and uniformly, a roll coating method or a spin coating method is particularly preferably used.

  As a mold, a single crystal silicon substrate (hereinafter referred to as “matrix”) in which a pyramid or inverted pyramid microstructure (hereinafter referred to as “texture”) is formed by etching a single crystal silicon substrate with acid or alkali is used. Can be used.

  Nanoimprint technology or the like can be used as a method for transferring the matrix texture to the underlying layer. By forming a texture similar to that of the matrix on the base layer between the substrate and the transparent conductive film, it is considered that interface reflection is reduced and light scattering is increased. In this case, the texture size (that is, the height between peaks and valleys) on the surface of the underlayer is preferably 300 to 1200 nm. This is because a scattering characteristic that matches the light absorption characteristic of the silicon solar cell can be obtained. Further, the texture structure is not limited to the pyramid type, and it is considered that the same effect can be obtained even when a honeycomb structure, a porous structure, or the like is formed.

As the underlayer 2, as shown in FIG. 2, a layer containing fine particles of silicon oxide (SiO ₂ ) can be used. This is because SiO ₂ has a refractive index lower than that of the transparent conductive film and has a value close to that of a light-transmitting insulating substrate such as glass, so that interface reflection of light can be prevented. Further, for the purpose of adjusting the refractive index of the base layer 2, in addition to SiO _2, titanium oxide (TiO _2), aluminum oxide (Al ₂ O _3), indium tin oxide (ITO), zirconium oxide (ZrO _2), or Fine particles such as magnesium fluoride (MgF ₂ ) may be included. Various methods are used as a method for forming the underlayer containing these fine particles, and a roll coating method in which a binder forming material containing fine particles and a solvent is applied together is preferably used. This is because a fine underlayer can be uniformly formed with fine particles. The size of these fine particles is 50 nm to 800 nm, preferably 90 nm to 600 nm. This is because when the size of the fine particles is within these ranges, for example, in the case of a thin-film silicon type solar cell, light is effectively scattered by this texture size for an absorption wavelength of 300 to 1200 nm, and interface reflection is reduced. The effect becomes greater.

  The transparent conductive film 3 is formed of a plurality of transparent electrode layers. In this case, a metal oxide such as tin oxide, zinc oxide, ITO, or indium-titanium composite oxide is preferably used as the transparent electrode layer. . Among these, it is more preferable that at least one of the plurality of transparent electrode layers contains zinc oxide.

  The transparent conductive film 3 in the present invention can be formed by a CVD method. Unlike the physical vapor deposition method (PVD) such as sputtering, the CVD method can easily form a surface uneven structure even in a thin film thickness. That is, since the texture structure can be changed according to the film forming conditions, the light confinement effect due to light scattering can be controlled.

Examples of the CVD method include a thermal CVD method and an LP-CVD (low pressure CVD) method. For example, when zinc oxide is used as the transparent conductive film, it can be formed by an LP-CVD (low pressure CVD) method or the like. The film-forming conditions of the transparent conductive film by the LP-CVD method are not particularly limited. For example, the substrate temperature is 150 ° C., the pressure is 5 to 1000 Pa, and the source gas is organic zinc, oxidizing agent, doping gas, and dilution gas. It is preferable to form. As the organic zinc, diethyl zinc (DEZ), dimethyl zinc or the like can be used, but DEZ is preferable because of its good reactivity with an oxidizing agent and easy procurement of raw materials. As oxidizing agents, water, oxygen, carbon dioxide, carbon monoxide, dinitrogen oxide, nitrogen dioxide, sulfur dioxide, dinitrogen pentoxide, alcohols (R (OH)), ketones (R (CO) R ′) , Ethers (ROR ′), aldehydes (R (COH)), amides ((RCO) _x (NH _3−x ), x = 1,2,3), sulfoxides (R (SO) R ′) (However, R and R ′ are alkyl groups) and the like can be used, but it is preferable to use water because it has good reactivity with organic zinc and is easy to handle. As the diluent gas, a rare gas (He, Ar, Xe, Kr, Rn), nitrogen, hydrogen, or the like can be used, but it is preferable to use hydrogen that has high thermal conductivity and excellent thermal uniformity in the substrate. As the doping gas, diborane (B ₂ H ₆ ), alkylaluminum, alkylgallium, or the like can be used, but it is desirable to use diborane excellent in decomposition efficiency. In the case where water is used as the oxidant, water is a liquid at normal temperature and pressure, so that it is preferably supplied after being vaporized by a method such as heat evaporation, bubbling, or spraying.

The transparent conductive film 3 in the present invention is composed of a plurality of transparent electrode layers formed by a CVD method under a reduced pressure atmosphere. In this case, “under reduced pressure atmosphere” means a pressure lower than atmospheric pressure. The CVD apparatus for depositing the plurality of transparent conductive films has a preparation chamber and a deposition chamber. The role of the preparation chamber is to desorb and depressurize the substrate to be formed, and return the substrate formed in the film formation chamber to the preparation chamber again and leave it in a reduced pressure atmosphere. That is, the pressure in the charging chamber can be changed from atmospheric pressure to several Pa. The film forming chamber is maintained in a reduced-pressure atmosphere. The substrate is loaded from the preparation chamber, and a gas as a raw material is supplied to form a film, and after forming the film, the gas is exhausted to make a vacuum (hereinafter referred to as “vacuum”). In the case of “exhaust”, the indoor pressure (hereinafter referred to as “vacuum degree”) can be 3 × 10 ⁻³ Pa or less. The “under reduced pressure atmosphere” in the present invention is preferably in a state close to a vacuum except when a reaction gas is supplied during film formation.

  When forming each transparent electrode layer, it is preferable to stop the film formation and start the film formation again. As described above, once the crystal growth is stopped, new crystal nuclei are generated in the valleys and side surfaces of the formed texture, and the new texture grows from there. The surface coverage of the power generation layer that is relaxed and grows later is improved. Thereby, the optimal texture shape which suppresses the electrical defect accompanying generation | occurrence | production of line defects, such as a crack in a power generation layer, with a light-scattering characteristic maintained is formed. The advantage of forming by the CVD method is that, unlike a physical vapor deposition method such as a sputtering method, an uneven shape is easily formed even with a thin film thickness.

Below, the method to stop film forming is demonstrated. Examples of the method for stopping film formation include a method under a reduced pressure atmosphere and a method under atmospheric pressure. The “method in a reduced-pressure atmosphere” is a method that is continuously formed in a reduced-pressure atmosphere, and after forming each transparent electrode layer in the film-forming chamber, evacuation is performed to stop the film formation. Here, “to form continuously in a reduced-pressure atmosphere” means to form each layer while maintaining a reduced-pressure state without taking it out under atmospheric pressure. Moreover, in the said method, in order to stop film forming, the method of carrying out a board | substrate from a film forming chamber to a preparation chamber etc. and leaving still can also be used preferably. In order to stop the film formation, the degree of vacuum in the film formation chamber is preferably set to 3 × 10 ⁻³ Pa or less. In this case, the substrate temperature is more preferably 100 ° C. or lower. Film formation can be stopped by setting the degree of vacuum within this range, and film formation can be more completely stopped by setting the substrate temperature within the above range. The "method under atmospheric pressure" refers to a method in which after the film is formed in the film forming chamber, the substrate is taken out under atmospheric pressure, and then placed in the film forming chamber again to form the next layer in a reduced pressure atmosphere. Say. Thus, once taking out under atmospheric pressure, film formation can be stopped. At this time, it is preferable to take it out from the film forming chamber through the preparation chamber to atmospheric pressure.

  Among the above methods, the “method under a reduced pressure atmosphere” can stop film formation only by supplying / exhausting gas or adjusting the room temperature without removing the substrate from the apparatus. In addition, since each transparent electrode layer can be formed only by the CVD method, it is particularly preferably used from the viewpoint of cost, productivity, etc., compared to the case where different film forming methods such as the CVD method and the sputtering method are used in combination. Can do.

  In the “plurality of transparent electrode layers” forming the transparent conductive film 3, the SDR (surface area ratio) after film formation of each layer is preferably smaller in the (n + 1) th layer than in the nth layer. Here, n represents an integer of 1 or more, and the transparent electrode layers are formed on the base layer 2 in the order of the first layer, the second layer,. That is, in the case of FIG. 1, it is preferable that SDR is smaller in 3b than in 3a. Here, SDR is the ratio of the surface area of the uneven surface to the flat surface, as defined by the diagram and the mathematical formula of FIG. 3, and the larger this value, the larger the surface area of the texture (that is, the steep convex portion). The smaller the value, the larger the surface area of the texture (that is, the texture having a gentle convex portion is formed). When the transparent conductive film 3 is formed in this way, the surface has a gentle concavo-convex structure, so that it is possible to suppress the generation of defects in the power generation layer and the like formed thereon, resulting in a solar cell such as voltage and fill factor. It becomes possible to suppress the deterioration of characteristics.

  In addition, in the “plurality of transparent electrode layers” forming the transparent conductive film 3, it is preferable that the SDS (summit density) after forming each layer is larger in the (n + 1) th layer than in the nth layer. . That is, in the case of FIG. 1, it is preferable that SDS is larger in 3b than in 3a. Here, SDS indicates “the number of maximum values per unit area”. For example, in the case of texture, the number indicates the number of vertices. Therefore, it is preferable that the number of vertices on the surface is larger in the (n + 1) th layer than in the nth layer. In this case, it is considered that the effect of maintaining the light scattering characteristics such as the short circuit current density can be expected.

  As described above, the (n + 1) -th layer has a smaller SDR and a larger SDS than the n-th layer, that is, by making the surface a gentle uneven structure while maintaining the number of textures, the short-circuit current density, etc. It is considered that the solar cell characteristics such as voltage and fill factor can be improved while maintaining the light scattering characteristics.

  Regarding the film thickness of each transparent electrode layer, for example, when zinc oxide is used as the transparent electrode layer, the film thickness of the (n + 1) th zinc oxide layer may not exceed the film thickness of the nth zinc oxide layer. preferable. For example, the thickness of the first zinc oxide layer 3a is preferably 1 to 2 μm, and the thickness of the second zinc oxide layer 3b is preferably 0.1 to 0.4 μm. By setting the film thickness within this range, a concavo-convex structure that contributes effectively to the light confinement effect can be sufficiently imparted. In addition, it is easy to obtain the necessary conductivity for the transparent electrode layer, and light absorption by zinc oxide itself is less likely to occur, so it is possible to suppress a decrease in the amount of light reaching the photoelectric conversion unit, thereby increasing the conversion efficiency. The film forming conditions for each transparent electrode layer may be the same or may be changed, but it is desirable to form the film by fixing the film forming conditions to obtain the highest quality film.

  For the transparent conductive film 3 formed of the plurality of transparent electrode layers, the film thickness is an ellipsometer, the haze ratio is a haze meter, Sa (average roughness), SDS (summit density), and SDR (surface area ratio) are AFM. Each was measured by (atomic microscope). Ellipsometry measurement was performed using a spectroscopic ellipsometer VASE (manufactured by JA Woollam). The haze ratio is a value represented by (diffuse light transmittance) / (total light transmittance) × 100, and was measured by a method based on JIS K7136. The measurement was performed using NDH 5000W manufactured by Nippon Denshoku Industries Co., Ltd. The sheet resistance was measured based on JISK-7194 using a resistivity meter Loresta GP MCT-610 (manufactured by Mitsubishi Chemical Corporation). Note that Sa, SDS, and SDR in the present invention are obtained from an atomic force microscope (AFM) image obtained by observing a square region having a side of 5 μm (ISO 4287/1). The non-contact mode of Nano-R system (manufactured by Pacific Nanotechnology) was used for this AFM measurement.

  The haze ratio of the transparent conductive film 3 is preferably about 5 to 80%, more preferably about 35 to 80%, and the sheet resistance is preferably set to about 5 to 20Ω / □.

  Thus, the substrate 4 with a transparent conductive film can be formed.

  Next, a typical cross-sectional view of the thin film photoelectric conversion device of the present invention is shown in FIG. In FIG. 4, the amorphous silicon photoelectric conversion unit 5, the crystalline silicon photoelectric conversion unit 6, and the back electrode layer 7 are arranged in this order on the substrate 4 with a transparent conductive film.

  First, the amorphous silicon photoelectric conversion unit 5 can be formed on the substrate 4 with a transparent conductive film by a plasma CVD method or the like. The amorphous silicon photoelectric conversion unit 5 is preferably sensitive to light of about 360 to 800 nm. As the amorphous silicon photoelectric conversion unit 5, a structure composed of a p-type amorphous silicon carbide layer 51, an i-type amorphous silicon layer 52, and an n-type microcrystalline silicon layer 53 can be used.

  The amorphous silicon carbide layer 51 can be formed by introducing silane, diborane, hydrogen, methane, or the like into the chamber. At this time, the film thickness of the amorphous silicon carbide layer 51 is preferably set to 5 nm or more and 50 nm or less. Next, it is preferable that the i-type amorphous silicon layer 52 is formed to a thickness of 100 nm to 500 nm by introducing silane and hydrogen as a film forming gas. Furthermore, it is preferable to form the n-type microcrystalline silicon layer 53 with a film thickness of 5 nm to 50 nm by introducing silane, phosphine, and hydrogen into the chamber as a film forming gas. The film thicknesses of 51, 52, and 53 are not limited to the above ranges, and can be changed as appropriate.

  Next, the crystalline silicon photoelectric conversion unit 6 is formed on the amorphous silicon photoelectric conversion unit 5. As a method of forming the crystalline silicon photoelectric conversion unit 6, first, the p-type microcrystalline silicon layer 61 is formed by introducing silane, diborane, and hydrogen into the chamber. At this time, the film thickness is preferably 5 nm or more and 50 nm or less. Next, it is preferable that the i-type crystalline silicon layer 62 is formed with a film thickness of 0.5 μm to 3.5 μm by introducing silane and hydrogen as a film forming gas. Furthermore, it is preferable to form the n-type microcrystalline silicon layer 63 with a thickness of 5 nm to 50 nm by introducing silane, phosphine, and hydrogen into the chamber as a film forming gas. The film thicknesses of 61, 62, and 63 are not limited to the above range and can be changed as appropriate.

  Next, the back electrode layer 7 is formed. The back electrode layer 7 preferably has a two-layer structure including a zinc oxide layer 71 and an Ag layer 72. The zinc oxide layer 71 is formed by a sputtering method, a CVD method, or the like, but is preferably formed by a CVD method because electrical damage to the silicon layer can be reduced. The Ag layer 72 can be formed by sputtering or vapor deposition. The back electrode layer 7 is not limited to the above, and other materials can also be used.

As specific examples of the embodiment described above, some examples will be described below together with comparative examples.
Example 1
As Example 1, a thin film photoelectric conversion device as shown in FIG.
First, an SiO ₂ layer was formed as a foundation layer 2 on a glass substrate 1 having a thickness of 0.7 mm and a 125 mm square by a sol-gel method. As a coating solution, a SiO ₂ sol-gel solution (trade name: 512B manufactured by Honeywell) used as an SOG material was used, and a base layer 2 having a film thickness of 1000 nm was formed using a spin coating method as a coating method.

  Subsequently, the entire substrate on which the underlayer 2 was formed was pre-baked on a hot plate at 60 ° C. for 20 minutes to semi-cure the underlayer. Subsequently, the substrate is carried into the imprint apparatus, and the base layer is pressed against the substrate on which the base layer is formed by the nanoimprint method using a matrix having a textured structure having a texture size of 600 nm formed on the surface. A texture structure was formed. The mother mold is made by degreasing and cleaning with ultrasonic irradiation with acetone and ethanol, followed by immersion in a potassium hydroxide / isopropyl alcohol mixed aqueous solution and etching for a predetermined time to form a textured structure. Yes.

Next, the substrate on which the uneven structure was formed was baked at 400 ° C. for 1 hour in an air atmosphere. The transmittance of this substrate was measured by entering light from the side where the uneven structure was not formed with a spectrophotometer. The transmittance was 85% or more in the wavelength range of 400 to 1200 nm, and the haze ratio was 52%. , Sa was 81.1 nm, SDS was 7.52 1 / μm ² , and SDR was 23.9%. FIG. 5 shows an AFM image of the surface of the substrate with the concavo-convex structure.

Next, the substrate on which the concavo-convex structure was formed was carried into the preparation chamber of the CVD apparatus and depressurized, and then carried into the film forming chamber under a reduced pressure atmosphere. Thereafter, zinc oxide doped with B (boron) was formed as a transparent electrode layer 3a with a film thickness of 1.2 μm on the side where the uneven structure of the substrate was formed. In this case, as a condition for forming the transparent electrode layer 3a, the substrate was first carried into the film forming chamber and the substrate temperature was adjusted to 150 ° C. Thereafter, 1000 sccm of hydrogen, 500 sccm of diborane diluted to 5000 ppm with hydrogen, 100 sccm of water, and 50 sccm of diethylzinc were introduced. The pressure in the film forming chamber at this time was 10 Pa. After film formation, the substrate was evacuated until the pressure in the film formation chamber (that is, the degree of vacuum) was 3 × 10 ⁻³ Pa, the substrate was carried into the preparation chamber, and left until the substrate temperature reached 80 ° C. The pressure in the charging chamber at this time was 5 Pa. Subsequently, the substrate was again carried into the film forming chamber, and the transparent electrode layer 3b was formed to a thickness of 0.4 μm under the same conditions as the transparent electrode layer 3a.

In this case, the characteristics of the substrate 4 with a transparent conductive film after forming 3b are as follows: total light transmittance is 83.6%, sheet resistance is 22Ω / □, haze ratio is 72%, Sa is 78.4 nm, and SDS is 60 .9 1 / μm ² and the SDR was 55.7%.

  Subsequently, in order to form the amorphous silicon photoelectric conversion unit 5, the substrate 4 with a transparent conductive film is introduced into a plasma CVD apparatus, and a boron-doped p-type amorphous silicon carbide (SiC) layer 51 is formed thereon. A 10 nm, non-doped i-type amorphous silicon conversion layer 52 was formed to a thickness of 300 nm, and a phosphorus-doped n-type microcrystalline silicon layer 53 was formed to a thickness of 20 nm.

  Subsequently, a boron-doped p-type microcrystalline silicon layer 61 having a thickness of 15 nm, a non-doped i-type crystalline silicon conversion layer 62 having a thickness of 0.7 μm, and a phosphorus-doped n-type microcrystalline silicon layer 63 having a thickness of 20 nm are formed by plasma CVD. Filmed. Thereby, the crystalline silicon photoelectric conversion unit 6 was formed. Further, a zinc oxide layer having a thickness of 71 nm and an Ag layer 72 having a thickness of 300 nm were formed as the back electrode layer 7 by sputtering.

A photoelectric conversion unit having a 1 cm square light receiving area was separated from the thin film photoelectric conversion device obtained as described above, and the photoelectric conversion characteristics were measured. That is, using a solar simulator having a spectral distribution of AM1.5, the pseudo-sunlight was irradiated with an energy density of 100 mW / cm ² at 25 ° C., and the output characteristics were measured. The short-circuit current density was 10.6 mA / cm ² , the fill factor was 69.5%, and the conversion efficiency was 10.2%. The results are shown in Table 1. A cross-sectional TEM photograph of the above thin film photoelectric conversion device is shown in FIG.

(Example 2)
Next, as Example 2, a thin film photoelectric conversion device was formed in the same manner as in Example 1. However, the difference was only in the method for forming the transparent electrode layer in Example 1. That is, after the transparent electrode layer 3a is formed, the substrate is taken out from the preparation chamber under atmospheric pressure (exposure to the atmosphere), and then transferred again into the preparation chamber and depressurized, and subsequently transferred into the film forming chamber under a reduced-pressure atmosphere to be transparent. Electrode layer 3b was formed. As a result, when the characteristics of the substrate were evaluated at the stage of forming 3a, the total light transmittance was 87.6%, the sheet resistance was 40.2Ω / □, the haze ratio was 65.7%, Sa was 103 nm, and SDS was It was 50.0 1 / μm ² and the SDR was 76.5%. Further, the total light transmittance of the substrate 4 with a transparent conductive film after the formation of the transparent electrode layer 3b is 83.6%, the haze ratio is 70%, the sheet resistance is 22.7Ω / □, Sa is 78.4 nm, and SDS is 60.0. 1 / μm ² and SDR were 55.7%, and the same characteristics as in Example 1 were obtained. In addition, when comparing the substrate characteristics after the formation of 3a and after the formation of 3b, since the SDS increases and the SDR decreases due to the laminated structure (that is, the 3b layer is formed after the 3a layer is formed), the texture is decreased. It can be said that a smooth surface irregularity shape was formed as the number of Similarly, when a thin film photoelectric conversion device was formed and the photoelectric conversion characteristics were measured, the open-circuit voltage was 1.37 V, the short-circuit current density was 10.5 mA / cm ² , the fill factor was 70.0%, and the conversion efficiency was 10 The same characteristics as those of Example 1 were obtained.

  From the above, even if the film is continuously formed in a reduced pressure atmosphere (even if the film formation is stopped in a reduced pressure atmosphere), or even if the film is formed out of the film forming apparatus and then formed again (at atmospheric pressure) The same effect was obtained even when film formation was stopped at

(Comparative Example 1)
Next, as Comparative Example 1, a thin film photoelectric conversion device was formed in the same manner as in Examples 1 and 2. However, only the transparent electrode layer 3a corresponding to Examples 1 and 2 was configured, and the difference was only in that 3b was not present and the film thickness of the transparent electrode layer 3a was 1.6 μm. That is, the base layer 2 was formed in the same manner as in Examples 1 and 2, and the transparent electrode layer 3a was formed. In this case, haze was 71%, Sa was 85.8 nm, SDS was 37.9 1 / μm ² , and SDR was 74.6%. Subsequently, the amorphous photoelectric conversion unit 6, the crystalline silicon photoelectric conversion unit 7, and the back electrode layer 8 were formed by the same method to form a two-junction thin film silicon solar cell. A photoelectric conversion unit having a 1 cm square light receiving area was separated from the thin film photoelectric conversion device obtained as described above, and the photoelectric conversion characteristics were measured. As a result of the solar simulator test, the open-circuit voltage was 1.34 V, the short-circuit current density was 10.5 mA / cm ² , the fill factor was 68.0%, and the conversion efficiency was 9.57%.

  From the above results, even with the same film thickness, by forming a fine fine uneven structure on the outermost surface, the scattering characteristics and the surface shape are improved, and the characteristics are greatly improved. The results are shown in Table 1.

(Example 3)
Next, as Example 3, a thin film photoelectric conversion device was formed in the same manner as in Example 1. However, the difference was only in the formation method of the underlayer 2 in Examples 1 and 2. That is, first, an underlayer 2 containing SiO ₂ fine particles was formed on a glass substrate 1 having a thickness of 0.7 mm and a square of 125 mm. The coating solution used to form the underlayer 2 is a mixture of a spherical silica dispersion having a particle size of 90 nm, water, and ethyl cellosolve, and tetraethoxysilane is added to the mixture to further hydrolyze the tetraethoxysilane. Used. After apply | coating a coating liquid on glass with a printing machine, after drying for 30 minutes at 90 degreeC, it confirmed that the fine unevenness | corrugation was formed on the surface by heating for 5 minutes at 350 degreeC after that. When the surface of this substrate was observed with an atomic force microscope (AFM), the shape of the fine particles was reflected, and the projections and depressions were confirmed to be curved, with a haze ratio of 1%, Sa of 21 nm, and SDS of 48.6. The 1 / μm ² and the SDR were 34.6%. FIG. 6 shows an AFM image of the surface of the substrate with the concavo-convex structure.

Next, transparent electrode layers 3a and 3b were formed in the same manner as in Example 1. In this case, after forming the transparent electrode layer 3b, the total light transmittance is 85%, the haze ratio is 15.0%, the sheet resistance is 18Ω / □, Sa is 30.0 nm, and SDS is 52.0 1 / μm. ² and SDR was 45.7%. Subsequently, the amorphous photoelectric conversion unit 6, the crystalline silicon photoelectric conversion unit 7, and the back electrode layer 8 were formed by the same method to form a thin film photoelectric conversion device.

A photoelectric conversion unit having a 1 cm square light receiving area was separated from the thin film photoelectric conversion device obtained as described above, and the photoelectric conversion characteristics were measured. That is, using a solar simulator having a spectral distribution of AM1.5, the pseudo-sunlight was irradiated with an energy density of 100 mW / cm ² at 25 ° C., and the output characteristics were measured. The short circuit current density was 10.2 mA / cm ² , the fill factor was 70.1%, and the conversion efficiency was 9.80%. The results are shown in Table 1.

Example 4
Next, as Example 4, a thin film photoelectric conversion device was formed in the same manner as in Example 3. However, the difference was only in the method for forming the transparent electrode layer in Example 3. That is, after the transparent electrode layer 3a is formed in the film forming chamber, the substrate is taken out to atmospheric pressure through the preparation chamber and exposed to the atmosphere, and then the substrate is again transferred from the preparation chamber to the film forming chamber. 3b was formed. As a result, the characteristics after the transparent electrode layer 3a was formed (after exposure to the atmosphere after the formation of 3a, that is, the characteristics before the formation of 3b) were 84.2% in total light transmittance, 11% in haze ratio, and 34Ω / □ in sheet resistance. , Sa was 31.4 nm, SDS was 45.0 1 / μm ² , and SDR was 51.9%. Further, after the formation of 3b, the total light transmittance was 83.7%, the haze ratio was 15%, the sheet resistance was 19Ω / □, Sa was 29 nm, SDS was 52.0 1 / μm ² , and SDR was 46. The same characteristics as in Example 3 were obtained. Similarly, when a thin film photoelectric conversion device was formed and the photoelectric conversion characteristics were measured, the open-circuit voltage was 1.37 V, the short-circuit current density was 10.1 mA / cm ² , the fill factor was 70.5%, and the conversion efficiency was 9 It was 0.76%, and the same characteristics as in Example 3 were obtained.

  From the above, even if the film is continuously formed in a reduced pressure atmosphere (even if the film formation is stopped in a reduced pressure atmosphere), or even if the film is formed out of the film forming apparatus and then formed again (at atmospheric pressure) The same effect was obtained even when film formation was stopped at Therefore, it is considered that an optimal method should be selected in accordance with the operation status and production status of the apparatus.

(Comparative Example 2)
Next, as Comparative Example 2, a thin film photoelectric conversion device was formed in the same manner as in Examples 3 and 4. However, only the transparent electrode layer 3a corresponding to Examples 3 and 4 was configured, and the difference was only in that 3b was not present and the film thickness of the transparent electrode layer 3a was 1.6 μm. That is, when the base layer 2 was formed in the same manner as in Examples 3 and 4 and the transparent electrode layer 3a was formed, the transmittance was 82%, the haze ratio was 14%, the sheet resistance was 20Ω / □, Sa was 30.0 nm, and SDS was 37. 0.0 1 / μm ² and the SDR was 50.0%. Subsequently, the amorphous photoelectric conversion unit 6, the crystalline silicon photoelectric conversion unit 7, and the back electrode layer 8 were formed by the same method to form a thin film photoelectric conversion device. A photoelectric conversion unit having a 1 cm square light receiving area was separated from the thin film photoelectric conversion device obtained as described above, and the photoelectric conversion characteristics were measured. As a result of the solar simulator test, the open circuit voltage was 1.33 V, the short circuit current density was 10.2 mA / cm ² , the fill factor was 67.5%, and the conversion efficiency was 9.16%. From these results, even when the film thickness was the same, the scattering characteristics and the surface shape were improved by increasing the number of textures to form a gentle shape, and the characteristics were greatly improved. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Underlayer 3 Transparent conductive film 3a Transparent electrode layer 3b Transparent electrode layer 4 Substrate with transparent conductive film 5 Amorphous silicon photoelectric conversion unit 51 p-type amorphous silicon carbide layer 52 i-type amorphous silicon layer 53 n 6 microcrystalline silicon layer 6 crystalline silicon photoelectric conversion unit 61 p type microcrystalline silicon layer 62 i type crystalline silicon layer 63 n type microcrystalline silicon layer 7 back electrode layer 71 zinc oxide layer 72 Ag layer

Claims (10)

A substrate with a transparent conductive film in which a base layer and a transparent conductive film are formed in this order on a substrate, wherein the transparent conductive film is composed of a plurality of transparent electrode layers formed by a CVD method under a reduced pressure atmosphere. A method for manufacturing a substrate with a transparent conductive film. The plurality of transparent electrode layers are continuously formed in a reduced-pressure atmosphere, and after forming each transparent electrode layer, the film formation is stopped by vacuum evacuation to form the next layer. The manufacturing method of the board | substrate with a transparent conductive film of Claim 1. 3. The production of a substrate with a transparent conductive film according to claim 2, wherein when the film formation is stopped, the degree of vacuum is 3 × 10 ⁻³ Pa or less and the substrate temperature is 100 ° C. or less. Method. 2. The transparent conductive film according to claim 1, wherein the plurality of transparent electrode layers are taken out under atmospheric pressure after the formation of each transparent electrode layer, and the next layer is formed again under a reduced pressure atmosphere. A method for manufacturing a substrate with a substrate. 5. The SDR (surface area ratio) after film formation of each layer in the plurality of transparent electrode layers is characterized in that the (n + 1) th layer is smaller than the nth layer. The manufacturing method of the board | substrate with a transparent conductive film of description. The method for producing a substrate with a transparent conductive film according to claim 1, wherein at least one of the plurality of transparent electrode layers contains zinc oxide. The base layer is formed by transferring a concavo-convex structure of a matrix formed by etching a single crystal silicon substrate to the base layer by a nanoimprint technique. The manufacturing method of the board | substrate with a transparent conductive film of description. The method for manufacturing a substrate with a transparent conductive film according to claim 1, wherein the underlayer is formed of silicon oxide. It forms with the manufacturing method in any one of Claims 1-8, The board | substrate with a transparent conductive film characterized by the above-mentioned. On the substrate with a transparent conductive film according to claim 1, at least one amorphous silicon photoelectric conversion unit, a crystalline silicon photoelectric conversion unit, and a back electrode layer were laminated in this order from the light incident side. A thin film photoelectric conversion device.