JPH01132004A - Light transmitting conductive substrate and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a light transmitting conductive substrate having a haze factor effective for its use as an amorphous silicon solar battery by forming a transparent conductive film on a thin film of SiO2 having unevenness like craters. CONSTITUTION:The title device comprises a light transmitting heat resistant substrate 1 laminated with a thin film 2 of SiO2 and a transparent conductive film 3. The light transmitting heat resistant substrate 1 has a large light transmission factor in the visible light range, and it is a substrate with flat surfaces the conditions of which will not change in the temperatures up to 550 deg.C, while the thin film 2 of SiO2 is a film having unevenness like craters of an average diameter of 0.05-5mum and an average depth of 0.03-0.5mum to be an undercoat of the transparent conductive film 3. Light is therefore refracted and reflected largely and randomly when it passes the undercoat layer of the thin film 2 of SiO2 having the crater-like unevenness. A light transmitting conductive substrate with a large haze factor which is suitable for an amorphous silicon solar battery can thus be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a light-transmitting conductive substrate, and more specifically, the present invention relates to a light-transmitting heat-resistant substrate, on which a 5iO1 thin film and a transparent conductive film are formed. The present invention relates to a transparent conductive substrate and a method for manufacturing the same.

The light-transmitting conductive substrate of the present invention is a conductive substrate having excellent light-transmitting properties and scattering properties of transmitted light, and is suitable as an electrode substrate for an amorphous silicon solar cell.

[Conventional technology]

With the aim of improving the light conversion rate of amorphous silicon solar cells, various attempts have been made to extend the path of light in the amorphous silicon layer.

For example, by orienting the crystals of the conductive film on a transparent conductive substrate,
A method of forming an uneven texture on the surface of a conductive film is described in Japanese Patent Application Laid-Open No. 60-240166, and a method of forming an uneven texture on a transparent substrate by polishing or etching, and forming a conductive film on this substrate. However, JP-A-60-049
It is disclosed in Publication No. 679 and 1985 Sunshine Project Research and Development Overview (Japan Industrial Technology Promotion Foundation, April 1986).

On the other hand, for undercoating a transparent conductive substrate for an amorphous silicon solar cell, a solution containing an alkoxysilane compound, water and alcohol is coated on a glass substrate.
JP-A-62-3046 discloses a 5iOt film having an uneven surface treated under specific conditions.

[Problem that the invention seeks to solve]

In order to improve the light conversion rate of an amorphous silicon solar cell, one key point is how long the path of light passing through the thin amorphous silicon semiconductor layer is made. As a means of extending the path of light in the all thin amorphous silicon semiconductor layer, as cited above, unevenness is provided on the surface of the light-transmitting conductive film, the light-transmitting substrate, or the surface of the undercoat layer of the conductive film, and the light-receiving surface is A method was proposed to scatter incident light from

However, in the method of forming a texture on the surface of the transparent conductive film, the optimal texture structure differs depending on the formation conditions of the amorphous silicon semiconductor layer.
It is necessary to control the texture on the submicron order, and it is extremely difficult to optimize the conditions for forming a conductive film that satisfies the desired resistance value, film thickness, optical properties, etc.

On the other hand, with the method of forming irregularities on the surface of a transparent substrate by polishing, it is not possible to form uniform irregularities, and with the method of forming irregularities with chemical etching, it is possible to form irregularities of 1 μm or less. However, neither of these methods can be said to be effective because smooth unevenness is formed that is unsuitable for texture.

In addition, in the method of forming irregularities on the SiJ film of the undercoat layer of the conductive film, the hydrolysis rate of the alkoxysilane compound may be changed depending on the holding conditions after coating the glass substrate with the 5IOt film forming solution, such as the relative humidity of the atmosphere. However, these conditions have little flexibility, making control extremely difficult and difficult to employ as an industrial method.

An object of the present invention is to provide a transparent conductive substrate that has a high light scattering rate (haze rate) and is suitable for use in amorphous silicon solar cells, and a method for manufacturing the same.

[Means for solving problems]

As a result of intensive research to achieve the above object, the present inventors have discovered that a 5i02 undercoat film having crater-like irregularities formed by a dipping method using a 5iOt thin film-formed product containing an alkoxysilane compound as a main component. The haze rate of the transparent conductive substrate on which the transparent conductive film was formed was 5.
The present invention was completed based on the discovery that the haze rate can reach as much as 0% and that the haze rate can be arbitrarily controlled within the range of 1 to 50% by changing the composition ratio of the SiO□ thin film forming composition.

The present invention provides a light-transmitting heat-resistant substrate (1), a light-transmitting heat-resistant substrate [1]
) with an average diameter of 0.05 to 5 μm in close contact with both sides or one side.
, a transparent conductive film (3) in close contact with a SiO□1 film (2) having crater-like irregularities with an average depth of 0.03 to 0.5 μm and a SiJ thin film (2). It is a conductive substrate.

The present invention will be explained with reference to FIG. 1, which shows one embodiment of the present invention.

The light-transmitting heat-resistant substrate (1) has a high light transmittance in the visible light range and has a smooth surface that does not change state at temperatures up to 550°C. For example, transparent substrates commonly used for electronic devices such as soda lime glass substrates, borosilicate glass substrates, and silicate glass substrates can be used.
Soda lime glass substrates are preferably used because they are available in large quantities and are inexpensive.

The 5in2 thin film (2) has an average diameter of 0.05 to 5p on the surface.
It is an undercoat film of a transparent conductive film (3) having crater-like irregularities with an average depth of 0.03 to 0.5 μm, and in FIG. Although they are provided in close contact with each other, they may be provided on both sides.

The average diameter, average depth, and average pitch of the crater-like unevenness are not particularly limited and can be arbitrarily selected.

The 5i02Fit film (2) is attached to the light-transmitting heat-resistant substrate (1).
is immersed in the following StO□ thin film forming composition, pulled up at a constant speed, dried, and then heat-treated at 250 to 500°C to form it in close contact with both or one side of the translucent heat-resistant substrate (1). can do.

The composition for forming a 5tO1 thin film contains a component (al alkoxysilane and/or a hydrolyzed condensate thereof) with 5iO1
In an organic solvent solution containing 1 to 20% by weight in terms of t,
Component (bl organic solvent soluble polymer f1 to 10 weight percent and component (C) organic compound O, OS which is incompatible with the component (al) and soluble in the organic solvent of 81 This is a solution in which additives such as % crab and a glass forming agent added as desired are added and dissolved.

Component 1a+ is represented by the general formula: Si(OR)n, in which R is a monovalent hydrocarbon group, preferably an alkyl group having 1 to 8 carbon atoms, such as a methyl group or an ethyl group.

Alkoxysilane containing at least one type of isopropyl group, normal butyl group, normal hexyl group, 2-ethylhexyl group, etc., more preferably tetramethoxysilane, tetraethoxysilane.

Tetraisopropoxysilane, tetrabutoxysilane, etc., and/or one type thereof or a hydrolyzed condensation product of two or more types thereof.

The organic solvent is one that can dissolve the component (al),
For example, comparison of lower alcohols such as methanol, ethanol, isopropanol, and n-butanol, acetate esters such as methyl acetate, ethyl acetate, and propyl acetate, ketones such as acetone, methyl ethyl ketone, and acetylacetone, and β-diketones. From the viewpoint of drying properties, it is preferable to use one kind of organic solvent having a low boiling point or a mixture of two or more kinds of organic solvents.

The component (bl) is a viscosity modifier for the SiJ thin film forming composition, and may be any polymeric substance that can dissolve in the organic solvent and increase the solution viscosity, such as hydroxypropyl cellulose (RPC), Hydroquinepropyl methylcellulose (HPMC), methylcellulose (
MC), cellulose derivatives such as ethyl cellulose, and polymeric substances known as thickeners such as polyacrylic acid are used. These can be used alone or in combination of two or more,
In particular, RPC is preferably used.

Component (C1 is an organic compound that is incompatible with the component (al) and soluble in the organic solvent. For example, phthalate esters such as methyl phthalate, ethyl phthalate, butyl phthalate, and octyl phthalate) esters, dibasic acid esters such as butyl adipate, octyl adipate, and octyl sebacate, oxyacid esters, fatty acid esters, etc., and these esters may be used alone or in combination of two or more.

The composition for forming s + Oz 'il B is basically an organic solvent solution of the components (at, mountain) and (C1), but various additives can be added as desired, and usually, To form a dense SiO□ thin film, glass forming agents such as inorganic or organic phosphorus compounds, boron compounds, tin compounds, antimony compounds, bisma H3 are used.
Add PO4.

S formed on both sides or one side of the light-transmitting heat-resistant substrate (1)
The average diameter, average depth, and average pinch of the crater-like irregularities of the iO This allows for arbitrary control.

The transparent conductive film (3) has a film thickness of 1 μm or less, has translucency and conductivity, and preferably has a sheet resistance value of 10Ω/
The film is less than sq. Examples include a tin-containing indium oxide film (ITO film), a fluorine-containing tin oxide film (FTO film), an antimony-containing tin oxide film (ATO film), and an aluminum-containing zinc oxide film. Excellent translucency,
ITO film with a low resistance value even with a relatively thin film thickness and FTO that allows texture to be easily formed by selecting film formation conditions.
ITO can be preferably used, has a low sheet resistance value, and can prevent property deterioration due to diffusion of conductive film components into the semiconductor layer, which is likely to occur when forming an amorphous silicon semiconductor layer.
A composite membrane in which an FTO membrane is laminated on a membrane is more preferably employed.

The transparent conductive film (3) is a light-transmitting heat-resistant substrate (1) on which a 5i02 film (2) having crater-like unevenness is formed by the method described above.
is heated and held at 400 to 550° C. and brought into contact with a carrier gas containing atomized fine particles of a precursor solution for forming a transparent conductive film, thereby forming it in close contact with the SiJ film (2) having crater-like irregularities. be able to. Is the precursor solution for forming a transparent conductive film a solvent-soluble metal compound whose metal species are the metal components in the transparent conductive film, or a solvent-soluble reaction product between metal compounds? 18? It is a. As a solvent,
Water, lower alcohols, lower alkyl esters, ketones, keto acids, β-diketones, and mixed solvents of two or more thereof can be used, and acetylacetone is particularly preferably used. There are no particular limitations on the method of atomizing the precursor solution for forming a transparent conductive film, but an ultrasonic atomization method is preferably employed because it can easily produce atomized fine particles with a uniform particle size. Air is normally used as the carrier gas for transporting the atomized fine particles of the precursor solution for transparent conductive film formation onto a substrate that has been heated and held in advance, but depending on the conditions, air may be used, or oxygen may be added by mixing nitrogen gas or oxygen gas. Use air, oxygen gas, etc. with controlled concentration. There are no particular restrictions on the method of contacting the carrier gas containing atomized fine particles of the precursor solution for forming a transparent conductive film with the substrate, but in order to form a transparent conductive film with uniform film quality and thickness, It is preferable to utilize diffusion contact of the forming components, and a method of controlling and contacting the substrate surface so that the streamlines of the carrier gas are parallel to each other is preferably employed. These film forming methods are known as pyrosol processes (PP methods) and are suitable as methods for forming the transparent IT film (3).

Also, vacuum evaporation method, sputtering method, spray method, C
The VD method is also transparent conductive! It can be adopted as the formation method of (3).

The optical properties of the light-transmitting conductive substrate of the present invention measured using a spectrophotometer are that the total visible light transmittance (scattered and transmitted multiton linear transmittance) is 80% in the visible light region of 400 to 800 nm.
With this, the haze rate reaches 50%. Further, the haze rate can be controlled within the range of 1 to 50% by selecting the composition of the 530g thin film. Further, the sheet resistance can be arbitrarily controlled by selecting the thickness of the transparent conductive film and the film forming conditions.

0 Effect] The light-transmitting conductive substrate of the present invention has a 530 g thin film (2) having crater-like unevenness as an undercoat layer and a transparent conductive film (3) laminated on a light-transmitting heat-resistant substrate (1). It is characterized by:

Further, the manufacturing method is characterized in that the 5t(ha film (2)) is formed by a dipping method using the composition for forming SiO□fit Ha.

In the light-transmitting conductive substrate of the present invention, when passing through the SiO□ thin film (2) having crater-like unevenness of the undercoat layer, light is largely and randomly refracted and reflected, resulting in excellent light scattering. Sexuality is expressed.

Furthermore, when the top layer of the transparent conductive film (31) is an FTO film, a texture can be formed, and the transmitted light is refracted and reflected in a more complex manner, resulting in a high haze ratio.

In forming the StOtm film (2), in the solution of the component ial alkoxysilane and/or its hydrolyzed condensate,
By using the StO□ thin film-forming composition in which an organic compound incompatible with component (BL) and (C1) were added to the above component (al), during drying after immersion and pulling up,
With the volatilization of the solvent, the organic compound of component (C1) separates from the coating film into fine particles on the surface of the coating film, and after the fine particles of the organic compound are removed by baking, they are formed as crater-like unevenness. The polymeric substance prevents agglomeration of organic compound fine particles, and also prevents the aggregation of organic compound particles.

Fj [The viscosity of the film-forming composition is adjusted to control the film thickness of the SiO□ thin film (2) formed in one diffusing operation. The size (average diameter and depth) and density (average pinch) of the crater-like unevenness can be controlled by the type and composition ratio of each component, especially the type and composition ratio of the organic compound of component Cl, and the volatilization rate of the solvent. As a result, a transparent conductive substrate with a controlled haze rate can be obtained.

〔Example〕

The present invention will be explained in more detail with reference to Examples and Comparative Examples.

However, the scope of the present invention is not limited in any way by the following examples.

(1) SiOxm film with crater-like unevenness (2
) Formation of fal S i Oz Preparation of composition for thin film formation 219 g of tetraethoxysilane, 643 g of ethanol
g, 206 g of acetic acid, and 0.3 g of 35% hydrochloric acid were mixed, stirred and held under reflux conditions for 10 hours, and the hydrolyzed wire metal of tetraethoxysilane with a concentration of 5.9% by weight converted to SiO2 was mixed with unreacted tetraethoxysilane. A solution containing ethoxysilane was prepared.

To 863 g of the solution prepared above, 41.98 g of a 5% ethanol solution of hydroxypropyl cellulose (trade name: RPC-H, manufactured by Nippon Soda ■) was added and mixed, and then H3
66.8 g of a 5.38 wt% ethanol solution of PO4 (P
□7.5% by weight in terms of OS) was added and mixed uniformly.

Then, dioctyl adipate (DOA) was added to this solution.
The content of is 0.25% by weight, 0.5% by weight, 1% by weight
Add and mix to make 4 levels of 3% by weight.
Compositions for forming IO1 thin film; A-1 to A-4 were prepared.

In addition, as a comparative SiO□ thin film forming composition: C-1, a commercially available SiJ containing tetraethoxysilane as a main component
A composition for forming a thin film (trade name: N5i-500, manufactured by Nippon Soda ■) was prepared.

(bl Formation of SiO□ thin film (2) The composition for forming Sing thin film prepared above: A-1 to A-
4 and the comparative Sing thin film forming composition: C-1, each was thoroughly cleaned as a light-transmitting heat-resistant substrate (1), and one side was coated with t! A soda lime glass substrate (50 mm x 100 mm x 1°1 mm) to which fI separation tape was attached was immersed, pulled up at a constant speed of 20 cm/min, and left in the air to dry. After peeling off the release tape, the temperature was preheated by holding it at 170°C for 10 minutes in an electric furnace, and the temperature was further raised to 500°C for 30 minutes to bake it, and then it was coated on one side of the transparent heat-resistant substrate (1). A 540 g thin film (2) was formed.

+21 Formation of transparent conductive film (3) (al Precursor solution for forming transparent conductive film Dibutyltin diacetate was dissolved in an acetylacetone solution of an organic indium compound, Sn/In (atomic ratio) was 0.05, [
An ITO film forming precursor solution having a concentration of 2.78% by weight in terms of nz02 was prepared.

In addition, ammonium fluoride was dissolved in a methanol solution of tin tetrachloride, F/Sn (atomic ratio) was 0.05, and Sn
An FTO film-forming precursor solution having a concentration calculated as O of 6% by weight was prepared.

t) Formation of transparent conductive film (3) Using a PP method thin film forming apparatus having a carrier gas inlet in the center of the conveyor furnace, charge the transparent R conductive film forming precursor solution prepared above into an ultrasonic atomizer. ,0.87JI
Ultrasonic vibrations of Hz were generated to atomize the particles into fine particles, which were dispersed in a carrier gas and introduced into a PP method thin film forming apparatus. On the other hand, the light-transmitting heat-resistant substrate (1) on which the 5iO1 thin film (2) was formed in the above item (2) is placed on a conveyor and sent into the furnace, heated to 400 to 550°C, and introduced into the furnace. The transparent conductive film forming precursor solution was brought into contact with a carrier gas containing atomized fine particles, and S i Ot * W
i (2+) A transparent conductive substrate having an ITO film or an FTO film on it was prepared.

In addition, FT
O film is formed, and ITO film/F is formed on s+ozFJ film (2).
A light-transmitting conductive substrate having a two-layer TO film was manufactured.

(4) Haze rate Using a self-recording spectrophotometer, measure the optical i3 pass rate of the transparent conductive substrate prepared in the previous section, and calculate the haze rate: H (%) using the following formula.
) was calculated.

y T1: Total spectral transmittance T: Spectroscopic direct vAi3 pass rate The calculated haze rates are shown in Table 1.

In addition, 30 of the transparent conductive substrate produced in Example No. 10
The spectral transmission curve and haze rate in the 0 to so on'm region are shown in FIG.

〔Effect of the invention〕

As shown in Table 1 of the results of the above examples, commercially available 5iO
In the light-transmitting conductive substrate of the comparative example in which the SiJ thin film (2) was formed using the composition for forming a thin film, and the transparent conductive film (3) was formed thereon, the transparent conductive films (3) were formed. FTO with texture formed by strictly controlling film conditions
Even if it is a membrane? The haze rate is extremely low at 2%, and an effective haze rate cannot be obtained as a transparent conductive substrate for an amorphous silicon solar cell.

In contrast, the transparent conductive substrate of the present invention has a transparent conductive film (3) on a 5iOz thin film (2) having crater-like unevenness.
Therefore, it has an extremely high haze rate and is suitable for electrodes of amorphous silicon solar cells. Also,
The average diameter, average depth, and average density of the crater-like irregularities of the SiO2 thin film (2) can be controlled by simply changing the amount of the organic compound (C1) of the SiO2 thin film forming composition, resulting in transparent A light-transmitting conductive substrate having an arbitrary haze ratio can be manufactured without severely controlling the conditions for forming the conductive film.

Although the electrical properties of this transparent conductive substrate were not shown in the examples, they can be arbitrarily adjusted by selecting the transparent conductive film (3) or controlling the film properties.

The present invention provides a transparent conductive substrate having a haze rate suitable for use in electrodes of amorphous silicon solar cells, and a method for manufacturing the same, and has extremely great industrial significance.

[Brief explanation of the drawing]

Fig. 1 Schematic cross-sectional view of the transparent conductive substrate of the present invention [Usage code] (1) Transparent heat-resistant substrate (2) StO□ film with crater-like unevenness [3]
Transparent Todoroelectric film (3a) T To film layer (3b> FTO film layer ('b) Spectral linear transmittance (C1 haze rate patent applicant (430) Representative of Nippon Soda Co., Ltd.
Person (7125) Yoshi Yokoyama Miyoshi Z-plane purification Figure 1 Figure 2 Light wavelength (λ) nm Procedural amendment 1986/Month 72

Claims (1)

[Scope of Claims] 1. A light-transmitting heat-resistant substrate (1), an average diameter of 0.05 to 5 μm and an average depth of 0.03 to 0.5 μm, closely attached to both sides or one side of the light-transmitting heat-resistant substrate (1). Transparent conductive substrate 2 characterized by comprising a SiO_2 thin film (2) having crater-like irregularities and a transparent conductive film (3) in close contact with the SiO_2 thin film (2). Indium film (
Transparent conductive substrate 3 according to claim 1, which is made of a fluorine-containing tin oxide film (FT film).
Transparent conductive substrate 4 according to claim 1 consisting of an ITO film (3a) in which the transparent conductive film (3) is in close contact with the SiO_2 thin film (2) and an ITO film (3a) in close contact with the ITO film (3a). Transparent conductive substrate 5 according to claim 1, comprising an FTO film (3b) Component (a) an organic alkoxysilane and/or a hydrolyzed condensate thereof having a concentration of 1 to 20% by weight calculated as SiO_2 In a solvent solution, component (b) 1 to 10% by weight of an organic solvent-soluble polymeric substance and component (c) 0.05 to 10% by weight are added.
5% by weight of the component (a) and is incompatible with the component (a).
) to a solution in which a soluble organic compound is added and dissolved in the solvent,
The light-transmitting heat-resistant substrate (1) is immersed and pulled up at a constant speed,
After drying, the SiO_2 thin film (2) having crater-like irregularities is formed on both sides or one side of the light-transmitting heat-resistant substrate (1) by heating and baking at a temperature of 250 to 500°C.
Transparent heat-resistant substrate (1) with O_2 thin film (2)
Method 6 for producing a translucent conductive substrate, which comprises heating and holding at 0 to 550°C and contacting with a carrier gas containing atomized fine particles of a precursor solution for forming a transparent conductive film (3) Component (b) Method 7 for producing a transparent conductive substrate according to claim 5, wherein the polymeric substance is hydroxypropyl cellulose (HPC) Atomization of the precursor solution for forming the transparent conductive film (3) is carried out by ultrasonic A method for manufacturing a transparent conductive substrate according to claim 5, which is carried out by an atomization method.