JP2012150904A - Transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for depositing a transparent conductive film, depositing a transparent conductive film having low resistance and a predetermined surface shape using a simple film deposition device and a simple process.SOLUTION: A method for depositing a transparent conductive film of the present invention includes the steps of: forming droplets from a film deposition solution containing a film deposition material; and spraying the droplets on an object to be film-deposited, thereby depositing a transparent conductive film while a surface temperature of the object to be film-deposited is changed from a first temperature region to a second temperature region. The first temperature region is higher than the second temperature region by 20°C or more. The temperature change from the first temperature region to the second temperature region is preferably continuous.

Description

  The present invention relates to a method for forming a transparent conductive film formed by droplet spraying, and more particularly to a method for forming a transparent conductive film used in a thin film solar cell.

  A thin film solar cell uses a transparent substrate on the light receiving surface side in order to efficiently take in external light, and a transparent conductive film is formed as an electrode on the surface. Since such a transparent conductive film has electrical conductivity (low resistance) and transparency, a metal oxide such as tin, zinc, indium, and titanium is used as a main component.

  The transparent conductive film is required to have a sheet resistance of about 20Ω / □ or less. In order to achieve this, a dopant material is added to the metal oxide to increase the carrier concentration, or the crystallinity is increased to increase the carrier mobility.

  In addition, such a transparent conductive film needs to be provided with a performance (light confinement performance) for confining external light in the film. In order to achieve this, a fine texture shape is formed on the surface of the transparent conductive film so that external light is repeatedly reflected and scattered. Such scattering of external light is expressed by a haze ratio defined by diffuse transmittance / total transmittance × 100, and in order to obtain a sufficient light confinement effect, the haze ratio may be about 5% or more. is necessary.

  As a method for forming the transparent conductive film, there is a process such as vacuum thermal CVD or plasma CVD, or a non-vacuum droplet spraying method. Among them, the non-vacuum type droplet spraying method is to form a transparent conductive film by spraying a gas containing droplets having a diameter of several μm onto a substrate, and the configuration of the film forming apparatus is simple. In addition, since it is a simple process, it is a film forming method that has been attracting attention in recent years.

  In the non-vacuum droplet spraying method, when a transparent conductive film is formed at a high temperature, crystal growth is promoted, and a texture shape can be formed on the surface of the transparent conductive film. However, on the other hand, since the dopant component volatilizes without being taken into the transparent conductive film, the transparent conductive film has a high resistance.

  On the other hand, when a transparent conductive film is formed at a low temperature, the dopant component is easily taken into the transparent conductive film, so that the resistance of the transparent conductive film can be reduced. Becomes smaller. Therefore, in the non-vacuum droplet spraying method, temperature control of the substrate surface during film formation is extremely important.

  However, when the transparent conductive film is formed by the non-vacuum type droplet spraying method, there is a rapid temperature drop of the substrate during the film formation. That is, when a transparent conductive film is formed by spraying droplets on the substrate, the heat of the substrate is taken away by the evaporation heat of the droplets, and the surface temperature of the substrate is lowered. For this reason, it was not possible to efficiently form a transparent conductive film having desired electrical conductivity and texture shape.

  As an attempt to solve such a problem, for example, in Patent Document 1, after heating a substrate to a first temperature and forming a first layer at the first temperature, the substrate is brought to a second temperature. A method of heating and forming the second layer at a second temperature has been proposed. Patent Document 2 proposes a technique for heating droplets in advance so that the surface temperature of the substrate does not decrease when a gas containing droplets is sprayed onto the substrate.

Japanese Patent Laid-Open No. 02-258691 JP 2004-241270 A

  In the film forming method of Patent Document 1, it is necessary to prepare at least two film forming chambers heated to different temperatures or to change the heating temperature of the substrate during film forming. However, if the substrate heating temperature is suddenly changed, the substrate is warped or cracked, so the temperature must be gradually changed, resulting in a large apparatus configuration and a long process time.

  Further, in the film forming method disclosed in Patent Document 2, when the gas containing the droplets is heated to the boiling point of the solvent or higher, the droplets are excessively heated. The reaction proceeds, and the film-forming materials in the droplets gather before reaching the substrate. For this reason, many aggregates of film-forming materials are mixed in the inside and the surface of the transparent conductive film. On the other hand, when the gas containing the droplets is formed at a temperature lower than the boiling point of the solvent, the difference between the solvent temperature and the substrate temperature is still large, and thus it cannot be avoided that the temperature of the substrate is lowered by the droplets.

  As described above, the conventional film forming method by droplet spraying is a transparent conductive film having both low resistance and predetermined surface shape on a substrate in a single film forming chamber having a simple apparatus configuration. Could not be formed.

  The present invention has been made in view of the current situation as described above, and an object of the present invention is to provide a simple film forming apparatus and a simple process with low resistance and having a predetermined surface shape. The object is to provide a method of forming a conductive film.

  The method for forming a transparent conductive film according to the present invention includes a step of forming droplets from a film-forming solution containing a film-forming material, and spraying the droplets onto the film-forming material to thereby form a surface temperature of the film-forming material. Forming a transparent conductive film while changing the temperature from the first temperature region to the second temperature region, wherein the first temperature region is 20 ° C. or more higher than the temperature of the second temperature region. . It is preferable that the temperature change from the first temperature range to the second temperature range is continuous.

  A transparent conductive film formed by the method for forming a transparent conductive film, wherein the transparent conductive film has unevenness of a height difference of 50 nm or more and 500 nm or less on the surface, and is covered between the front and back surfaces of the transparent conductive film. The conductivity of the surface opposite to the side in contact with the film-formed product is higher than the conductivity of the surface of the transparent conductive film on the side in contact with the film-formed product. The transparent conductive film preferably has a haze ratio of 5% or more.

  According to the present invention, a transparent conductive film having a low resistance and a predetermined surface shape can be formed with a simple film forming apparatus and a simple process by having the above-described configuration.

It is typical sectional drawing of the film-forming apparatus using the film-forming method of the transparent conductive film of this invention. In the film-forming method of this invention, it is a graph which shows an example of the temperature change of the surface of the to-be-deposited object from the film-forming start of film-forming of a transparent conductive film. It is typical sectional drawing of the transparent conductive film formed into a film by the film-forming method of this invention. In the film-forming method of this invention, it is a graph which shows an example of the temperature change of the surface of the to-be-deposited object from the film-forming start of film-forming of a transparent conductive film. In the conventional film-forming method, it is a graph which shows an example of the temperature change of the surface of the to-be-deposited object from the film-forming start of film-forming of a transparent conductive film. It is a graph which shows the relationship between the temperature when forming a transparent conductive film, and the specific resistance of the transparent conductive film obtained by it. It is a graph which shows the relationship between the temperature when forming a transparent conductive film, and the haze of the transparent conductive film obtained by it.

  Hereinafter, the film-forming method of the transparent conductive film of this invention is demonstrated using drawing. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Method for forming transparent conductive film>
FIG. 1 is a schematic cross-sectional view showing a film forming apparatus using the method for forming a transparent conductive film of the present invention. The transparent conductive film forming method of the present invention is typically formed using the film forming apparatus shown in FIG. Hereinafter, the film forming method of the transparent conductive film of the present invention will be described with reference to the film forming apparatus of FIG. 1 includes a film forming solution 1 containing a film forming material, a transport unit 2 that transports the film forming solution 1, a droplet generating unit 6 that replaces the film forming solution 1 with droplets 5, A film formation object 7 for forming a transparent conductive film and a film formation object heating unit 8 for heating the film formation object 7 are provided. The droplet generation unit 6 includes a nozzle head 3 and a carrier gas introduction unit 4, and droplets 5 are sprayed onto the film formation object 7 by the carrier gas.

  As shown in FIG. 1, the method for forming a transparent conductive film of the present invention includes forming a droplet 5 from a film forming solution 1 containing a film forming material, and applying the droplet 5 to a film formation object 7. Forming a transparent conductive film while changing the surface temperature of the deposition object 7 from the first temperature region to the second temperature region by spraying, the first temperature region including the second temperature region It is characterized by being 20 ° C. higher than the temperature in the temperature region.

  Here, the first temperature region is a condition of the surface temperature of the film formation target 7 for forming the transparent conductive film having a predetermined surface shape, and the low temperature transparent conductive film is formed in the second temperature region. This is the condition of the surface temperature of the film formation object 7 to be formed. The first temperature region is characterized by being 20 ° C. or more higher than the temperature in the second temperature region.

  By combining the first temperature region and the second temperature region that satisfy such temperature conditions, a transparent conductive film having a predetermined surface shape and having a low resistance can be formed. The surface temperature of the film-forming object 7 is adjusted by spraying droplets containing the film-forming solution and absorbing the heat of the surface of the film-forming object. The “predetermined surface shape” means a pyramid-like undulating surface having irregularities with a length from the top of the convex part of the concave and convex part to the bottom part of the concave part of 50 nm or more and 500 nm or less.

  When forming a transparent conductive film using the film forming apparatus in FIG. 1, the transparent conductive film is formed by scanning one or both of the film formation object 7 and the droplet generation unit 6. The film is formed on the entire surface of the object 7. As shown in FIG. 1, such a transparent conductive film may be formed by one droplet generator 6 or may be formed by two or more droplet generators 6. When a transparent conductive film is formed by two or more droplet generation units 6, neither the film formation target 7 nor the droplet generation unit 6 may be scanned.

<Step of forming droplets>
The method for forming a transparent conductive film of the present invention includes a step of forming droplets 5 from a film forming solution 1 containing a film forming material. Here, as a method of forming the droplet 5 from the film forming solution 1, any method can be used as long as the film forming solution 1 is changed to a droplet 5 having an average particle diameter of 0.1 μm to several tens μm. For example, a spray method, an ultrasonic method, or the like can be used.

(Film forming solution)
The film-forming solution 1 used in the present invention is obtained by dissolving a film-forming material made of an inorganic metal such as zinc, tin, indium, cadmium, or strontium in an organic solvent or a metal halide compound in a solvent. It is. Such a film forming solution generally dissolves the organometallic or metal halide compound at a concentration of 0.1 to 3 mol / L, but is not limited to this concentration.

  In addition, water, an organic solvent, or a mixture thereof can be used as a solvent used for the film forming solution. Examples of the organic solvent here include methanol, ethanol, acetone, isopropyl alcohol, and the like, but are not limited thereto.

  Furthermore, the film-forming solution may further contain an additive in addition to the solvent and the film-forming material. Examples of such additives include a dopant agent, a surfactant, a pH adjuster, and the like, but it is preferable to use a mixture of two or more of these additives.

  Here, examples of the dopant agent include materials containing Mg, Ga, Al, Te, Ag, Ge, Cu, Sr, B, Sb, F, As, and the like, and examples of the surfactant include lower organic compounds. Etc. Examples of the pH adjuster include nitric acid, acetic acid, sulfuric acid, hydrofluoric acid, hydrogen peroxide, butyric acid, hydrochloric acid, and ammonia.

<Step of depositing transparent conductive film>
Next, the transparent conductive film is formed while the surface temperature of the film formation object 7 is changed from the first temperature area to the second temperature area by spraying the droplets 5 produced above onto the film formation object 7. Film. Hereinafter, the temperature change of the surface of the film formation target 7 during film formation will be specifically described with reference to FIG.

  FIG. 2 is a graph showing an example of the temperature change of the surface of the film formation object from the start of film formation to the end of film formation in the film formation method of the present invention. As shown in FIG. 2, since the surface temperature of the film formation object is lowered by spraying droplets onto the film formation object, it is continuous between the start of film formation and the end of film formation. Therefore, the surface temperature of the film formation object is lowered. In particular, at the initial stage of spraying, droplets having a temperature sufficiently lower than the surface temperature of the film formation target are sprayed, so that the temperature of the surface of the film formation decreases rapidly. A temperature region in which the surface temperature of the film-forming object at the initial stage of film formation rapidly decreases is defined as a first temperature region (A region surrounded by an elliptic dotted line in FIG. 2).

  Thereafter, from the middle to the end of film formation, the evaporation energy of the droplets reaching the surface of the film formation only takes the thermal energy of the film formation and lowers the temperature. Since there is no temperature decrease caused by the temperature difference from the temperature of the temperature, the gradient of the temperature decrease becomes gentle. A temperature region in which the surface temperature of the deposition object gradually decreases from the middle to the end of the film formation is defined as a second temperature region (region B surrounded by an elliptical dotted line in FIG. 2).

As described above, the surface temperature of the deposition object changes from the first temperature region in which the temperature rapidly decreases to the second temperature region in which the temperature gradually decreases. By producing a transparent conductive film at such a surface temperature of the deposition object, it is possible to form a transparent conductive film having a low resistance and a predetermined surface shape. In particular, the present invention is characterized in that the temperature difference between the first temperature region A and the second temperature region B is 20 ° C. or more. Such a temperature difference is preferably 20 ° C. or more. Such a temperature difference between the first temperature region and the second temperature region can be adjusted by the heating temperature of the film formation object, the type of the solvent, the material of the film formation object, the supply speed of the droplets, and the like. The supply rate of such droplets is preferably 0.5 μL / cm ² / s or more. When the temperature difference is less than 20 ° C., a transparent conductive film having a predetermined surface shape but having low conductivity or a conductive film having high conductivity but not having a predetermined surface shape is formed. A transparent conductive film having both surface shape and conductivity cannot be formed.

  In the film forming method of the present invention, it is preferable to form the film while the surface temperature of the film to be formed is continuously lowered as shown in FIG. In this way, by forming the transparent conductive film while continuously changing the surface temperature of the deposition object, the film forming apparatus is simplified and the film forming process is simplified, and the transparent conductive film is efficiently processed. A film can be formed. That is, it is not necessary to change the heating temperature of the film formation during film formation, and there is an advantage that a process for transporting the film formation using two or more film formation chambers becomes unnecessary.

  As a method for spraying the droplets 5, a spray method or an ultrasonic method can be used. As the spray method, it is preferable to use a two-fluid spray method in which two fluids of a liquid and a carrier gas are mixed and a droplet is ejected from the tip of the spray nozzle. In such a two-fluid spray system, the spread of the ejected droplets can be set by appropriately setting the shape of the tip of the spray nozzle. That is, for example, if the structure of the tip of the spray nozzle is hemispherical and the slit shape is concentric, the droplet spreads out in a perfect circle, and if the slit shape is rectangular, the droplet spreads out in an elliptical shape Is ejected.

In the spray method, since the film formation solution becomes droplets through the droplet generation unit immediately before the film formation target, the film formation solution is conveyed as it is to the tip of the spray nozzle. At this time, since the droplets are formed by the high-pressure carrier gas, the droplets and the carrier gas are sprayed on the film formation target. Further, a carrier gas may be used in order to provide directivity in the droplet transport direction. As such a carrier gas, compressed air, N ₂ , H ₂ , water vapor, O ₂ , or a mixture of one or more of these can be used.

  As the spray nozzle, any material can be used as long as it can withstand the kind of film forming solution, the carrier gas, and the pressure applied when the film forming solution is ejected. For example, the spray nozzle is made of a metal and a resin material. be able to.

  In the ultrasonic method, droplets are generated from a film-forming object by applying ultrasonic waves to the film-forming solution 1 from a droplet generator attached to a solution bottle. Since there is no energy, the droplets are conveyed by the carrier gas. As such a carrier gas, the same one as that used in the spray method can be used.

  When generating droplets using ultrasonic atomization, it is preferable to generate droplets using an ultrasonic transducer. Since the ultrasonic vibrator can spray mist having a relatively uniform average particle diameter, there is an advantage that the mists are less likely to aggregate. The ultrasonic vibrator is preferably sprayed with the film-forming solution 1 by ultrasonic waves having a frequency of 1 kHz or more and 3 kHz or less. Thereby, fine droplets having an average particle size of 1 μm or more and 10 μm or less can be obtained.

<Transparent conductive film>
FIG. 3 is a schematic cross-sectional view of a transparent conductive film formed by the film forming method of the present invention. As shown in FIG. 3, the transparent conductive film produced by the film forming method of the present invention is roughly divided into a portion 12 formed in the first temperature region and a portion 11 formed in the second temperature region. Is done. Note that the transparent conductive film in FIG. 3 has a two-layered transparent conductive film due to restrictions on the representation means of the drawing, but in reality, it is a gradient-like film from the film-forming side to the surface side of the transparent conductive film. It is preferable that the conductivity is improved.

  In the transparent conductive film formed by the film forming method of the present invention, the portion 12 formed in the first temperature region has a concavo-convex surface having a height difference of 50 to 500 nm, but has low electrical conductivity. Tend. On the other hand, the portion 11 formed in the second temperature region does not form unevenness, but has high electrical conductivity. However, the entire surface of the transparent conductive film reflects the surface unevenness of the portion formed in the first temperature region, and has an uneven shape with a height difference of 50 to 500 nm.

  Therefore, a portion having a desired surface shape is produced by film formation in the first temperature region, and a conductive portion is produced by film formation in the second temperature region. By forming a transparent conductive film under conditions including these two temperature ranges, a transparent conductive film having a desired surface shape and high conductivity can be manufactured.

  As described above, the transparent conductive film formed under the condition that the film forming temperature is gradually lowered has the conductivity of the surface opposite to the side in contact with the film formation side of the transparent conductive film. It is characterized by being higher than the conductivity of the surface on the side in contact with the deposition object. By having such characteristics, it is possible to produce a film having a low specific resistance on the side in contact with the photoelectric conversion layer on the front and back of the transparent conductive film, thereby facilitating extraction of carriers generated in the photoelectric conversion layer. it can.

  The transparent conductive film formed by the film forming method of the present invention preferably has a thickness of 500 nm to 1.5 μm, and the portion 12 formed in the first temperature region is a layer of 100 nm to 400 nm. The portion 11 formed in the second temperature region preferably has a thickness of 100 nm or more and 900 nm or less.

  In order to judge that the transparent conductive film formed by the film forming method of the present invention has a predetermined surface shape, a haze ratio defined by diffuse transmittance / total transmittance × 100 is used. That is, it is considered that the transparent conductive film has a predetermined surface shape when the haze ratio is 5% or more. By making the surface shape satisfying such a haze ratio, light can be sufficiently confined in the photoelectric conversion layer laminated on the film surface side of the transparent conductive film on the film formation object, and the conversion efficiency of the thin film solar cell Can be improved. If the haze ratio is less than 5%, the light confinement effect of the transparent conductive film cannot be sufficiently obtained.

(Film formation)
Any material can be used as the film formation material used in the film formation method of the present invention as long as the material is transparent in the absorption region of the photoelectric conversion layer. For example, a glass substrate, a resin material substrate, or the like is used. Can do.

(Film to be deposited heating section)
In the present invention, the deposition object heating unit is provided to heat the deposition object to a temperature of 350 to 600 ° C. There is no particular limitation on the film-forming object heating unit as long as it can heat the film-forming object to a predetermined temperature, and any object can be used. Such a film-forming object heating unit 8 is a method of heating by direct conduction heat transfer using a hot plate, a method of heating by convection heat transfer using a furnace in which the inside is heated, or a radiant heat transfer irradiating an infrared lamp or the like. Any of the heating methods can be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
In this example, first, as the film forming solution 1, an aqueous solution in which 0.5 mol / L SnCl ₄ and 0.5 mol / L NH ₄ F were mixed was prepared. On the other hand, a glass substrate was used as the film formation object 7, and the glass substrate was heated to 500 ° C. by a hot plate.

  The film-forming solution 1 was sent to the nozzle head 3 by a liquid feed pump, and droplets were generated by a spray method in which the film-forming solution 1 was compressed with high-pressure gas into droplets. And in order to make a droplet arrive at a glass substrate from the nozzle head 3, the compressed air of the flow volume of 100 L / min was flowed in the spraying direction as a carrier gas. Thereafter, droplets of the film forming solution were ejected from the nozzle head 3 toward the film formation object 7 at a flow rate of 12 mL / min.

A transparent conductive film made of SnO ₂ was formed on the glass substrate by spraying droplets on the glass substrate for about 60 seconds while the glass substrate and the nozzle head 3 were fixed. The temperature change of the surface of the glass substrate during the film formation is shown in FIG. Note that the surface temperature of the film formation was measured with a thermocouple (product name: K thermocouple (manufactured by ASONE Corporation)).

  FIG. 2 is a graph showing changes in the surface temperature of the glass substrate from the start of film formation to the end of film formation of the transparent conductive film. As shown in FIG. 2, immediately after the droplets were ejected, the surface temperature of the film formation decreased rapidly from the first temperature region where the surface temperature was about 500 ° C., and became the second temperature region around 425 ° C. . That is, there was a temperature drop of about 80 ° C. from the first temperature range to the second temperature range.

  For the glass substrate with a transparent conductive film produced as described above, a plasma CVD method is used on the transparent conductive film to form a p-layer having a thickness of 10 nm, an n-layer having a thickness of 400 nm, and an i-layer having a thickness of 50 nm. A layer of amorphous Si layer was laminated. And the solar cell was produced by forming the back surface electrode which consists of 1-micrometer-thick Al on a i layer by a sputtering method.

(Example 2)
In contrast to Example 1, except that the flow rate of the carrier gas was 50 L / min and the droplets of the film formation solution were ejected from the nozzle head 3 toward the film formation object 7 at a flow rate of 9 mL / min, A transparent conductive film was formed by the same method as in Example 1. The temperature change of the surface of the glass substrate during the film formation is shown in FIG.

  FIG. 4 is a graph showing changes in the surface temperature of the glass substrate from the start of film formation to the end of film formation of the transparent conductive film. As shown in FIG. 4, immediately after the droplets were ejected, the temperature suddenly dropped from the first temperature region where the surface temperature of the substrate was about 500 ° C., and became the second temperature region around 476 ° C. That is, there was a temperature drop of about 24 ° C. from the first temperature range to the second temperature range. And the photovoltaic cell was produced using the method similar to Example 1 with respect to the glass substrate with a transparent conductive film produced as mentioned above.

(Comparative Example 1)
A transparent conductive film was formed by the same method as in Example 1 except that the film formation time of the transparent conductive film was changed to 20 seconds compared to Example 1. That is, the transparent conductive film was formed only in the first temperature region shown in FIG. 2, and was not formed in the second temperature region. And the photovoltaic cell was produced using the method similar to Example 1 with respect to the glass substrate with a transparent conductive film produced as mentioned above.

(Comparative Examples 2-6)
Compared to Example 1, the flow rate of the carrier gas was set to 50 L / min, and droplets of the film forming solution were ejected from the nozzle head 3 toward the film formation target 7 at a flow rate of 5 mL / min, and the temperature of the glass substrate was adjusted. A transparent conductive film was formed by the same method as in Example 1 except that the transparent conductive film was changed to 400 ° C., 420 ° C., 440 ° C., 460 ° C., and 475 ° C. The temperature change of the surface of the glass substrate during the film formation is shown in FIG.

  In Comparative Examples 2 to 6, the temperature drop from the first temperature region to the second temperature region is suppressed to about 15 ° C. or less by reducing the ejection amount of the film forming solution and the flow rate of the carrier gas. Thus, a transparent conductive film was produced.

<Evaluation results>
When the film thickness of the transparent conductive film produced in Examples 1 and 2 and Comparative Example 1 was measured with a stylus type surface shape measuring device (product name: DEKTAK (manufactured by Veeco)), the results shown in Table 1 below were obtained. became. Further, the sheet resistance (Ω / □) of the transparent conductive film was measured with a low resistivity meter (product name: Lorester GP (manufactured by Mitsubishi Chemical Analytech Co., Ltd.)), and the specific resistance (Ω · cm) was measured with respect to the film thickness and the sheet. Calculated from resistance. Furthermore, the haze rate (%) and the transmittance (%) of the transparent conductive film produced in each example and each comparative example were measured with a spectral haze meter (product name: TC-1800H (manufactured by Tokyo Denshoku Co., Ltd.)). . The measurement results are shown in Table 1 below.

  Moreover, when the cell characteristic was evaluated using the solar simulator with respect to the photovoltaic cell using the transparent conductive film produced in Examples 1-2 and Comparative Example 1, the result shown in the following Table 1 was obtained.

  From the results shown in Table 1, it was clarified that the solar battery cell produced using the transparent conductive film produced in Examples 1 and 2 showed good characteristics as an amorphous Si single cell. On the other hand, the solar battery cell produced using the transparent conductive film of Comparative Example 1 has significantly lower characteristics than those of Examples 1 and 2, and has a sufficient function as the transparent conductive film of the thin film solar battery. It became clear that it was not.

(Consideration of Comparative Examples 2 to 6)
The relationship between the surface temperature of the glass substrate and the specific resistance of the transparent conductive film was examined by measuring the specific resistance of the transparent conductive film prepared in Comparative Examples 2 to 6. FIG. 6 is a graph showing the relationship between the temperature at which a transparent conductive film is formed and the specific resistance of the transparent conductive film obtained thereby. From the results of the graph of FIG. 6, it was found that when the transparent conductive film was formed with the glass substrate having a high surface temperature, the specific resistance tended to increase.

  Moreover, the relationship between the surface temperature of a glass substrate and the haze rate of a transparent conductive film was investigated by measuring the haze rate of the transparent conductive film produced in Comparative Examples 2-6. FIG. 7 is a graph showing the relationship between the temperature at which a transparent conductive film is formed and the haze ratio of the transparent conductive film obtained thereby. From the result of the graph of FIG. 7, it was found that when the transparent conductive film was formed at a low temperature of 440 ° C. or less, the haze ratio tends to be 5% or less.

  From the results of the specific resistance shown in FIG. 6 and the haze ratio shown in FIG. 7, when the temperature difference between the first temperature range and the second temperature range is less than 20 ° C., the transparent conductive material having a low specific resistance and a high haze ratio. It became clear that the film could not be formed.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Since the transparent conductive film formed by the film forming method of the present invention has conductivity, it can be used for a thin film solar cell. Moreover, since it is a transparent conductive film having a predetermined surface shape, it has an antireflection property and can be used as a functional transparent conductive film such as a heat ray absorbent used in displays and touch panels such as liquid crystal and EL. .

  DESCRIPTION OF SYMBOLS 1 Film-forming solution, 2 conveyance part, 3 nozzle head, 4 carrier gas introduction | transduction part, 5 droplet, 6 droplet generation | occurrence | production part, 7 Film-forming object, 8 Film-forming object heating part, 11 Formation in 2nd temperature range Filmed portion, 12 A portion formed in the first temperature region.

Claims (4)

Forming droplets from a deposition solution containing a deposition material;
Forming a transparent conductive film while changing the surface temperature of the film formation object from the first temperature region to the second temperature region by spraying the droplet onto the film formation object,
The method for forming a transparent conductive film, wherein the first temperature region is 20 ° C. or more higher than the temperature of the second temperature region.   The method for forming a transparent conductive film according to claim 1, wherein the temperature change from the first temperature region to the second temperature region is continuous. A transparent conductive film formed by the method for forming a transparent conductive film according to claim 1 or 2,
The transparent conductive film has irregularities having a height difference of 50 nm to 500 nm on the surface,
The conductivity of the surface of the transparent conductive film opposite to the side in contact with the film-forming object is higher than the conductivity of the surface of the transparent conductive film on the side in contact with the film-forming object. film.   The transparent conductive film according to claim 3, wherein the transparent conductive film has a haze ratio of 5% or more.

Images