TWI684297B - Method for producing semiconductor film, and dye-sensitized solar cell - Google Patents

Abstract

[1] A method for producing a semiconductor film, including: dispersing semiconductor particles having an average particle diameter of 1 nm to less than 100 nm in an alcohol, thereby obtaining a dispersion; evaporating the alcohol from the dispersion to dry the semiconductor particles, thereby obtaining agglomerated particles formed by agglomeration of the semiconductor particles; and spraying the agglomerated particles onto a substrate, thereby forming a semiconductor film on the substrate. [2] The aforementioned method in which the semiconductor particles are dried by evaporating the alcohol with the semiconductor particles being present as sediment in the alcohol. [3] The aforementioned method in which the alcohol is evaporated at a temperature of lower than 50 ℃. [4] A dye-sensitized solar cell including a photoelectrode which includes: the semiconductor film produced by the aforementioned method; and a sensitizing dye adsorbed on the semiconductor film.

Description

Method for manufacturing semiconductor film, and dye-sensitized solar cell

The invention relates to a method for manufacturing a semiconductor film and a dye-sensitized solar cell.

This application claims priority based on Japanese Patent Application No. 2015-037233 filed in Japan on February 26, 2015, and the contents are incorporated herein.

The photoelectrode of the dye-sensitized solar cell uses a porous film composed of a semiconductor adsorbed with a photosensitizing dye. Regarding the production of such porous membranes, various membrane production methods using powder blowing methods are being studied. Examples include the aerosol deposition method (AD method), spray method, cold spray method, electrostatic spray method, and melt spray method. These methods are methods in which the powder of fine particles, which are the raw materials of the thin film produced, is sprayed onto the substrate to be processed by the conveying gas, and the collision energy is used to form a film. Among them, there is the background that the microparticles are brittlely deformed and densely packed during film formation, and as a result, a dense film is easily formed, and it is relatively difficult to make a porous film.

Generally, in order to increase the specific surface area of the formed porous membrane, it is required to reduce the particle size of the particles to be blown, and the particles should be carried out locally without brittle deformation of the particles. Join. However, since the smaller particles have a lower collision energy during blowing, they are more difficult to join with each other, and are easily pressed powders peeled from the substrate.

In order to solve the above-mentioned problems, Patent Document 1 discloses a porous membrane in which small-diameter particles that are not brittlely deformed are joined together by mixing and forming a membrane of two or more particles of different sizes in the AD method. Film making method. According to this film-forming method, a powder with large-diameter particles having a relatively large particle mass added to small-diameter particles is blown to the substrate, and collision energy is generated by the impact of the large-diameter particles, thereby forming small-diameter particles to be joined to each other. The resulting porous membrane.

Patent Document 2 discloses a method of obtaining small-diameter particles by calcining a compact mixture of small-diameter particles and a binder, and physically crushing the obtained sintered body using a mortar or the like. The porous large-diameter particles obtained by sintering are blown to the base material to produce a porous membrane.

[Prior Technical Literature]

[Patent Literature]

[Patent Literature 1] International Publication No. 2012/161161

[Patent Document 2] Japanese Patent Laid-Open No. 2004-33818

Since a part of the large-diameter particles is introduced into the porous film obtained by the film production method of Patent Document 1 (FIG. 7 and FIG. 8), there are unevenly distributed or reduced areas of porosity in the porous film. The light incident on the porous film is partially scattered due to the mixed large-diameter particles, so that the light transmittance of the porous film may decrease.

The film forming method of Patent Document 2 has a problem that the labor and time for calcining and pulverizing to prepare porous large-diameter particles for blowing are complicated and time-consuming.

In addition, there is a problem that the large-diameter particles obtained by pulverization have a wide particle size distribution (Figure 9), and large-diameter particles with a particle diameter of more than 400 μm are mixed, so a blowout effect occurs, and the film-forming body is destroyed or the film-forming body One part is cut, which leads to the problem of reduced film production speed. Therefore, there is a problem that before blowing, it takes a lot of labor and time to classify and remove huge large-diameter particles, resulting in a large decrease in the yield (raw material usage rate) of the large-diameter particles that can be blown.

Furthermore, on the produced porous membrane, the relatively tight porosity inside the large-diameter particles and the relatively loose porosity between the pores between the large-diameter particles coexist, so there is a lack of uniformity in the membrane structure, resulting in a specific surface area or membrane The problem of reduced strength.

The present invention has been completed in view of the above circumstances, and its object is to provide a method for manufacturing a semiconductor film that is relatively easy to prepare powder for blowing, and is easy to obtain a porous film in which semiconductor particles are bonded to each other, and to provide The semiconductor film produced by this method is used as a photoelectrode dye-sensitized solar cell.

[1] A method for manufacturing a semiconductor film, which obtains a dispersion liquid obtained by dispersing semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm in an alcohol, and evaporating the alcohol from the dispersion liquid to The semiconductor particles are dried to obtain aggregated particles obtained by aggregating the semiconductor particles, and the semiconductor film is formed on the substrate by blowing the aggregated particles to the substrate.

[2] The method for manufacturing a semiconductor film as described in [1] above, wherein the semiconductor particles are deposited in the alcohol, and the alcohol is evaporated to dry the semiconductor particles.

[3] The method for producing a semiconductor film as described in [1] or [2] above, wherein the alcohol is evaporated at a temperature not exceeding 50°C.

[4] The method for manufacturing a semiconductor film according to any one of the above [1] to [3], wherein the semiconductor particles are particles of a metal oxide semiconductor.

[5] The method for manufacturing a semiconductor film according to any one of the above [1] to [4], wherein the semiconductor film is a porous film.

[6] A dye-sensitized solar cell, comprising: adsorbing a sensitizing dye on the semiconductor film obtained by the method for manufacturing a semiconductor film according to any one of the above [1] to [5] electrode.

According to the method of manufacturing a semiconductor film of the present invention, it is not necessary to calcinate or pulverize raw material particles in order to prepare aggregated particles for blowing, which is convenient. In addition, because the size and strength of the aggregated particles are moderate, by blowing onto the substrate in the same manner as the conventional AD method, a large specific surface area can be easily obtained, the overall porosity and light transmittance of the entire membrane are uniform, and the structural strength is also Excellent porous semiconductor film.

Since the dye-sensitized solar cell of the present invention includes the photoelectrode in which the sensitizing dye is adsorbed on the porous structure of the semiconductor film having excellent characteristics described above, the photoelectric conversion efficiency and I-V characteristics are excellent.

51‧‧‧ Film making room

52‧‧‧Nozzle

53‧‧‧ Base material

54‧‧‧Semiconductor particles

55‧‧‧Gas storage tank

56‧‧‧Transport tube

57‧‧‧mass flow controller

58‧‧‧Aerosol generator

59‧‧‧Crusher

60‧‧‧Film making device

61‧‧‧Classifier

62‧‧‧Vacuum pump

63‧‧‧Abutment

71‧‧‧Film making surface

72‧‧‧Abutment mounting surface (upper surface)

73‧‧‧The surface opposite to the film-making surface

FIG. 1 is a schematic configuration diagram of a film forming apparatus that can be applied to the method for manufacturing a semiconductor film of the present invention.

FIG. 2 is the particle size distribution of the aggregated particles prepared in Example 1. FIG.

FIG. 3 is an SEM image obtained by observing the aggregated particles prepared in Example 1 using an electron microscope.

4 is an SEM image obtained by observing the cross-section of the porous membrane produced in Example 1 using an electron microscope.

5 is an SEM image obtained by observing the raw material particles prepared in Comparative Example 1 using an electron microscope.

6 is a graph showing the V-I characteristics of the simple unit produced in Example 1 and Comparative Example 1. FIG.

FIG. 7 shows a case where the raw material powder obtained by mixing large-diameter particles and small-diameter particles by the method of Patent Document 1 is blown by the AD method, and the large-diameter particles are mixed into the produced porous membrane. Schematic diagram of the situation.

FIG. 8 is an SEM image obtained by observing the cross section of the porous film produced by the method of Patent Document 1 using an electron microscope. Large-diameter particles are unevenly dispersed in the porous membrane composed of small-diameter particles.

9 is a powder of porous large-diameter particles obtained by mixing small-diameter particles and a binder prepared according to the method of Patent Document 2 and crushing the sintered and solidified sintered body in a compacted state using a mortar. The particle size distribution of the body.

10 is an SEM photograph obtained by observing a mixed powder obtained by mixing and drying small-diameter particles (average particle diameter 20 nm) and large-diameter particles (average particle diameter 200 nm) with an electron microscope.

FIG. 11 is a process of mixing and dispersing small-diameter particles (average particle diameter 20 nm) and large-diameter particles (average particle diameter 200 nm) in ethanol using an electron microscope, and then dispersing them SEM photograph obtained by observation of the powder obtained by drying.

Hereinafter, the present invention will be described with reference to the drawings based on a preferred embodiment, but the present invention is not limited to this embodiment.

"Manufacturing Method of Semiconductor Film"

The method for manufacturing a semiconductor film according to the first embodiment of the present invention is a method of obtaining the dispersion liquid obtained by dispersing semiconductor particles having an average particle diameter of 1 nm or more and not within a range of 100 nm into an alcohol, and then The dispersion liquid is evaporated to dry the semiconductor particles, thereby obtaining aggregated particles obtained by aggregating the semiconductor particles, and blowing the aggregated particles to a substrate to form a semiconductor film on the substrate.

The type of the above-mentioned semiconductor particles is not particularly limited, and known semiconductor particles constituting a photoelectrode of a dye-sensitized solar cell can be used.

The type of semiconductor constituting the above-mentioned semiconductor particles is preferably a semiconductor that generates a transition between energy gaps, for example: TiO ₂ , TiSrO ₃ , BaTiO ₃ , Nb ₂ O ₅ , MgO, ZnO, WO ₃ , Bi ₂ O ₃ , CdS , CdSe, CdTe, In ₂ O ₃ , SnO ₂ etc. Such semiconductors are preferred because the pigments adsorb well and function well as photoelectrodes that carry sensitizing dyes. From the viewpoint of improving the photoelectric conversion efficiency and the viewpoint that the aggregated particles described below can be easily formed, metal oxide semiconductors such as titanium oxide, zinc oxide, strontium titanate, and tin dioxide are suitable. As a suitable mechanism for particles composed of these metal oxide semiconductors, it is presumed that the secondary bonding force of the hydroxyl group, polar group or polar part on the surface of the particle contributes to proper agglomeration.

One type of the semiconductor particles may be used alone, or two or more types may be used in combination.

In this embodiment, as the semiconductor particles, semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm are used.

By using the semiconductor particles in the above range, aggregated particles having a size and strength suitable for making a porous film are obtained.

The average particle diameter of the semiconductor particles is preferably 5 nm or more and less than 70 nm, more preferably 10 nm or more and less than 50 nm, and still more preferably 15 nm or more and less than 30 nm.

By using the semiconductor particles in the above-mentioned suitable range, it is easier to obtain aggregated particles having a size and strength suitable for making a porous membrane.

Here, the strength of the aggregated particles suitable for making a porous membrane means that before the semiconductor particles of the aggregated particles that collide against the base material in the aggregated state undergo brittle deformation, the aggregation of the semiconductor particles is partially released from each other. And the strength of the degree to which a new surface is formed at the position where the semiconductor particles are in contact with each other to be joined. It is considered that in such aggregated particles of moderate strength that are neither hard nor soft, the gap between the semiconductor particles exerts a moderate buffering effect when colliding with the substrate.

On the other hand, in the large-diameter particles in which the semiconductor particles described in Patent Document 2 are pre-bonded by firing, the bonding of the semiconductor particles is too strong, so it is difficult to release when colliding with the substrate, and the semiconductor particles The gap between them is difficult to exert the buffering function as described above.

<Preparation of agglomerated particles>

The method of preparing aggregated particles for blowing in this embodiment includes: a first stage, which obtains a dispersion liquid obtained by dispersing semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm in an alcohol; and a second At the stage, by evaporating the alcohol from the dispersion, the The conductive particles are dried to obtain aggregated particles in which the semiconductor particles are aggregated.

[The first stage]

The semiconductor material of the semiconductor particles used in the first stage may be one kind or plural kinds, preferably 1 to 3 kinds, more preferably 1 or 2 kinds, and still more preferably 1 kind. The reason for this is that since it is easy to control the dispersion and aggregation of the semiconductor particles, it is possible to easily obtain aggregated particles having an appropriate size and strength.

The average particle diameter of the semiconductor particles used in the first stage is 1 nm or more and less than 100 nm. Within this range, the average particle diameter of the semiconductor particles may be 4 or more, preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. For example, in the first stage, the semiconductor particles with an average particle diameter of 20 nm, the semiconductor particles with an average particle diameter of 50 nm, and the semiconductor particles with an average particle diameter of 80 nm are mixed and used at an arbitrary ratio. The size of semiconductor particles. The fewer the types of semiconductor particles used in the first stage, the easier it is to control the dispersion and aggregation of the semiconductor particles, and the easier it is to obtain aggregated particles with appropriate size and strength.

The semiconductor particles used in the first stage preferably do not mix semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm. That is, it is preferable to prepare a dispersion liquid obtained by dispersing only semiconductor particles containing an average particle diameter within a range of 1 nm or more and less than 100 nm into alcohol. The reason is that, for example, when semiconductor particles (small-diameter particles) with an average particle diameter of 20 nm and semiconductor particles (large-diameter particles) with an average particle diameter of 200 nm are mixed and used, in the second-stage aggregation process, Small-diameter particles and large-diameter particles will agglomerate unevenly. That is, the reason is that there are at least three kinds of agglomeration states of aggregation of small-diameter particles, aggregation of small-diameter particles and large-diameter particles, and aggregation of large-diameter particles, and further, the mixing ratio of each particle Or the difference in the types of semiconductor materials, it is difficult to control the agglomeration process, and it is difficult to obtain target agglomerated particles with appropriate size and strength.

As an example of the state of agglomeration that cannot be controlled, an electron microscope is used to mix and dry the above-mentioned small-diameter particles (average particle diameter 20 nm) and the above-mentioned large-diameter particles (average particle diameter 200 nm) without using a dispersion medium. The SEM photograph obtained by observing the body is shown in FIG. 10. It has been observed that the non-uniform block formed by agglomeration of small-diameter particles is biased against multiple parts of the aggregate of large-diameter particles.

In order to eliminate the uneven aggregation state as described above, a process of mixing and dispersing the above-mentioned small-diameter particles and large-diameter particles in ethanol, followed by drying, and observing the obtained powder with an electron microscope, will The obtained SEM photograph is shown in Fig. 11. It was observed that the non-uniform aggregation of the small-diameter particles was eliminated, and the small-diameter particles were relatively uniformly adsorbed on the surface of the large-diameter particles. It is considered that the mixed powder prepared in this way can be subjected to film formation as described in Patent Document 1 by blowing. However, the target aggregated particles of this embodiment were not obtained.

In the first stage, for example, in the case of using powders of semiconductor particles having two types of average particle diameters included in the above-mentioned range, the nominal value of the average particle diameter is usually given as long as it is a commercially available powder. Two kinds of powders with different nominal values are mixed and used. Furthermore, the particle size distribution of the mixed powder in the dispersed state (horizontal axis: particle size, vertical axis: number of particles (frequency)) was measured, and if two peaks were observed in the above range, it can be seen that the Two types of semiconductor particles with an average particle diameter corresponding to the peak. Therefore, when using the powder of semiconductor particles with one kind of average particle size, when measuring the particle size distribution of the powder, one peak (unimodality), the modal particles of the particle size distribution can usually be observed The modal diameter corresponds to the average particle size.

To determine the particle size distribution of the semiconductor particles dispersed in the first stage In this case, the number of peaks observed is preferably 1 to 3, more preferably 1 or 2, and further preferably 1. The reason is that it is easy to control the degree of aggregation of the semiconductor particles, and it is easy to obtain aggregated particles having an appropriate size and strength.

The method of dispersing the semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm into the alcohol is not particularly limited, and it is preferable to slowly pour the powder of the semiconductor particles into the container in which the alcohol is added in advance while stirring the alcohol Method. Conversely, if it is a method of injecting alcohol onto the powder of semiconductor particles, the powder may be spherical and difficult to be dispersed.

The number and number of alcohols used for dispersion are not particularly limited, and can be any of the first, second, and third stages, or any number of multiples of one, two, or more than three yuan .

The monohydric alcohol molecule used in the first stage has one hydroxyl group and a hydrocarbon group. The above-mentioned hydrocarbon group may be linear, branched, or cyclic, and may also be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. The carbon number of the above-mentioned hydrocarbon group is not particularly limited. For example, the carbon number is preferably 1 to 10, more preferably the carbon number is 1 to 5, and further preferably the carbon number is 2 or 3.

Examples of suitable alcohols used in the first stage include methanol, ethanol, n-propanol, isopropanol, 1-butanol, 2-butanol, third butanol, 1-pentanol, and cyclohexanol. Wait. Among these, from the viewpoint of excellent dispersibility of semiconductor particles, easy drying, and easy to obtain aggregated particles of appropriate size and strength after drying, methanol, ethanol, 1-pentanol, n-propanol, and isopropyl alcohol are preferred. Propanol, more preferably ethanol.

The temperature of the alcohol that disperses the semiconductor particles in the first stage is not particularly limited, and for example, it can be performed in the range of 4 to 55°C. Preferably, at any temperature, the alcohol charged with the semiconductor particles is sufficiently stirred to disperse the individual semiconductor particles.

If the temperature is 55°C or lower, the agglomeration of the particles will not become too high, and the agglomerated particle size will easily become Evenly. It is preferably 40°C or lower. If it is 4°C or higher, the dispersibility of the particles is not increased, and the aggregated particle diameter may become extremely large. It is preferably 20°C or higher.

In order to improve the bonding of the following semiconductor particles, it is preferable not to contain substances that may remain except for the above-mentioned volatile solvent. Therefore, it is preferable to prepare a dispersion liquid obtained by dispersing only semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm in alcohol.

[second stage]

The method of evaporating the alcohol after the semiconductor particles are dispersed is not particularly limited, and for example, known methods such as heat treatment and reduced pressure treatment can be applied. The alcohol dispersion may be evaporated while stirring, but vigorous stirring may break the target aggregated particles or broaden the particle size distribution. Therefore, it is preferable to let it evaporate and dry while standing still or stirring gently. For example, it is preferable to allow the obtained dispersion liquid to stand for 30 minutes to 48 hours after preparing the dispersion liquid, thereby evaporating the alcohol and causing the semiconductor particles in a state where most of the semiconductor particles are precipitated in the alcohol dry. By drying gently in this way, it is possible to easily obtain agglomerated particles having an appropriate size and strength formed by aggregation of the semiconductor particles.

The temperature at which the semiconductor particles are dried by evaporating the alcohol is not particularly limited. For example, by evaporating and drying at less than 50° C., aggregated particles having an appropriate size and strength can be easily obtained. It is preferably less than 30°C. If it is heated at a high temperature and dried rapidly, there is a risk that the aggregation will be mixed and the unevenness of the particle size of each aggregated particle will increase. In addition, the time for the evaporation and drying treatment is preferably 1 to 72 hours, more preferably 2 to 48 hours, and still more preferably 5 to 48 hours.

The shape of the aggregated particles obtained in the second stage is not particularly limited, and it is preferably a shape suitable for blowing. By gently stirring during the above evaporation and drying processes Mixing, or gently stirring the powder of the aggregated particles after the alcohol has been removed, so that the aggregated particles rub against each other and the protruding parts are reduced, thereby making it possible to form a block suitable for blowing.

The average particle diameter of the aggregated particles obtained in the second stage is not particularly limited as long as it can be blown onto the substrate and the film can be formed. In the case of film formation by the well-known AD method, the average particle diameter of the aggregated particles is preferably, for example, 0.2 μm or more and less than 100 μm, more preferably 0.5 μm or more and less than 50 μm, and further preferably 0.8 μm or more And less than 10 μm, particularly preferably 1.0 μm or more and less than 5.0 μm.

If the average particle diameter is in the above-mentioned suitable range, a porous film excellent in strength, conductivity, light transmittance, and sensitizing dye adsorption can be easily produced at a desired thickness by the AD method.

In the case of measuring the particle size distribution of the powder of aggregated particles obtained in the second stage (horizontal axis: particle size, vertical axis: frequency), it is preferable that the number of observed peaks is 1 or 2 , Preferably one.

The modal particle diameter in the particle size distribution is not particularly limited, for example, it is preferably 0.2 μm or more and less than 100 μm, more preferably 0.5 μm or more and less than 50 μm, and still more preferably 0.8 μm or more and less than 10 μm, especially It is preferably 1.0 μm or more and less than 5.0 μm. Here, the modal particle size of the particle size distribution is the particle size corresponding to the maximum value of the frequency distribution.

With the above-mentioned preferred range, the AD method can be used to easily produce a porous film excellent in strength, conductivity, light transmittance, and sensitizing dye adsorption at a desired thickness.

The 10% particle size (d10) in the particle size distribution is not particularly limited, for example, it is preferably 0.1 μm or more and less than 5.0 μm, more preferably 0.2 μm or more and less than 3.0 μm, and still more preferably 0.3 μm or more and Less than 1.0μm. Here, the 10% particle size (d10) of the particle size distribution is the particle size at the point where the cumulative value of the cumulative distribution curve 10% crosses the horizontal axis.

With the above-mentioned preferred range, the AD method can be used to easily produce a porous film excellent in strength, conductivity, light transmittance, and sensitizing dye adsorption at a desired thickness.

The 50% particle size (d50) in the particle size distribution is not particularly limited, for example, it is preferably 0.1 μm or more and less than 10 μm, more preferably 0.5 μm or more and less than 5.0 μm, and still more preferably 1.0 μm or more and not Up to 3.0μm. Here, the 50% particle size (d50) of the particle size distribution is the particle size at the point where the cumulative value of the cumulative distribution curve 50% crosses the horizontal axis, which is the so-called median particle size.

With the above-mentioned preferred range, the AD method can be used to easily produce a porous film excellent in strength, conductivity, light transmittance, and sensitizing dye adsorption at a desired thickness.

The 90% particle size (d90) in the above particle size distribution is not particularly limited, for example, preferably 1.0 μm or more and less than 100 μm, more preferably 2.0 μm or more and less than 20 μm, and further preferably 3.0 μm or more and less than 10μm. Here, the 90% particle size (d90) of the particle size distribution is the particle size at the point where the cumulative value of the cumulative distribution curve 90% crosses the horizontal axis.

With the above-mentioned preferred range, the AD method can be used to easily produce a porous film excellent in strength, conductivity, light transmittance, and sensitizing dye adsorption at a desired thickness.

By going through the first and second stages described above, it is possible to obtain aggregated particles in which semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm are aggregated with each other.

The aggregated particles of the present embodiment can obtain sufficient acceleration and collision energy with the base material by blowing by the conventional AD method, so that either a porous film or a dense film can be formed on the base material. The agglomerated particles of this embodiment are composed only of semiconductor particles having a relatively small average particle diameter in the above-mentioned range, so inside the manufactured semiconductor film, large-diameter particles larger than the above-mentioned range are not mixed. Therefore, the formed film has a uniform film structure.

<Measurement of average particle size>

As a method for determining the average particle diameter of the semiconductor particles and the aggregated particles, a method determined in the form of a wave peak value of the distribution of the volume average diameter measured by a laser diffraction particle size distribution measuring device can be used.

The average particle diameter of the semiconductor particles (primary particles) is measured by a laser diffraction particle size distribution measuring device "wet type".

The average particle diameter of the agglomerated particles is measured "by dry type" using a laser diffraction particle size distribution measuring device.

<Film production steps>

The film forming step in this embodiment is a step of forming a semiconductor film on the substrate by blowing the aggregated particles onto the substrate.

Examples of a method for blowing the aggregated particles onto the substrate include an aerosol deposition method (AD method) in which an aerosol obtained by mixing a carrier gas and the aggregated particles is blown, and the acceleration of the aggregated particles by electrostatic attraction Electrostatic particle coating method, cold spray method, etc. Among these blowing methods, the AD method that can easily produce a porous film suitable for a photoelectrode is also preferable. As a film forming method using the AD method, for example, the method disclosed in International Publication No. WO2012/161161A1 can be applied. Hereinafter, the application of the AD method will be specifically described.

<Film production by AD method>

Hereinafter, an example of a film forming method will be described with reference to FIG. 1. In addition, the drawings used in the description are schematic diagrams, and the ratios of length, width, and thickness are not necessarily the same as actual ones, and can be appropriately changed. The film forming apparatus used in the film forming method of this embodiment is not particularly limited, and for example, the film forming apparatus 60 shown in FIG. 1 may be mentioned.

<Film making device>

The film forming apparatus 60 includes a gas storage tank 55, a transfer tube 56, a nozzle 52, a base 63, and a film forming chamber 51. The gas storage tank 55 is filled with gas (conveyed gas) that accelerates the aggregated particles 54 to be blown to the base 53. One end of the transfer pipe 56 is connected to the gas storage tank 55. The transport gas supplied from the gas storage tank 55 is supplied to the transport pipe 56.

A mass flow controller 57, an aerosol generator 58, a crusher 59 and a classifier 61 that can appropriately adjust the dispersion of the aggregated particles 54 in the transport gas are arranged in order from the front stage side of the transport tube 56. The crusher 59 can release the state where the aggregated particles 54 adhere to each other due to moisture or the like. Even if the aggregated particles passing through the crusher 59 exist in a state of being attached to each other, such excessively large particles can be removed by the classifier 61. Furthermore, when there is a concern that the aggregated particles 54 are crushed by the crusher 59 into individual semiconductor particles, the crusher 59 may not be used.

The mass flow controller 57 can adjust the flow rate of the conveying gas supplied from the gas storage tank 55 to the conveying pipe 56. The aerosol generator 58 is filled with aggregated particles 54. The aggregated particles 54 are dispersed in the transport gas supplied from the mass flow controller 57 and transported to the crusher 59 and classifier 61.

The nozzle 52 is arranged so that the opening portion omitted in the illustration faces the base material 53 on the base 63. The other end of the conveying pipe 56 is connected to the nozzle 52. The transport gas containing the aggregated particles 54 is sprayed from the opening of the nozzle 52 to the base 53.

The base material 53 is placed so that one surface 73 of the base material 53 abuts on the upper surface 72 of the base 63. In addition, the other surface 71 (film forming surface) of the base material 53 faces the opening of the nozzle 52. The aggregated particles 54 ejected together with the transport gas collide with the film-forming surface from the nozzle 52 to produce a porous film composed of semiconductor particles constituting the aggregated particles 54.

The base material 53 is preferably made of a material that can be joined without blowing the aggregated particles 54 through the film-forming surface 71. Examples of such base materials include glass substrates, resin substrates, resin films, resin sheets, and metal substrates. Among the substrates listed here, it is preferable to form a transparent conductive film such as ITO in advance on the surface of the non-conductive substrate. Since the porous film produced on the substrate has sufficient structural strength and conductivity suitable for the use of the photoelectrode, no additional calcination treatment is required. Therefore, a resin-made substrate having low heat resistance can be used. The thickness of the above-mentioned substrate is not particularly limited, and it is preferably a thickness that does not penetrate the aggregated particles to be blown. More specifically, the selection of the base material 53 is appropriately performed according to the film-forming conditions such as the material of the aggregated particles 54 and the blowing speed, and the use of the film to be produced.

The film-forming chamber 51 is provided for film-forming in a reduced-pressure environment. A vacuum pump 62 is connected to the film forming chamber 51, and the pressure inside the film forming chamber 51 is reduced as necessary.

<blowing method>

Hereinafter, an example of the blowing method of the aggregated particles 54 will be described.

First, the vacuum pump 62 is operated to decompress the inside of the film forming chamber 51. The pressure in the film-forming chamber 51 is not particularly limited, but is preferably set to 5 to 1000 Pa. By reducing the pressure to this level, the convection in the film forming chamber 51 can be easily suppressed, and the aggregated particles 54 can be blown to a specific position on the film forming surface 71.

Next, the conveyed gas is supplied from the gas tank 55 to the conveying pipe 56, and the flow rate and flow rate of the conveyed gas are adjusted by the mass flow controller 57. As the transport gas, for example, O ₂ , N ₂ , Ar, He, air, or the like can be used. The flow rate and flow rate of the conveyed gas can be appropriately set according to the material, average particle diameter, flow rate and flow rate of the aggregated particles 54 blown from the nozzle 52.

The agglomerated particles 54 are loaded into the aerosol generator 58 to disperse the agglomerated particles 54 into the conveying gas flowing in the conveying pipe 56 and accelerate. Agglomerated particles 54 from the nozzle The opening of 52 is sprayed at a speed from subsonic to supersonic speed so that it is deposited on the film-forming surface 71 of the base 53. At this time, the blowing speed of the aggregated particles 54 to the film-forming surface 71 can be set to, for example, 10 to 1000 m/s. The blowing speed is not particularly limited, and can be appropriately set according to the material of the base material 53, the type or size of the aggregated particles 54, and the like.

By adjusting the flow velocity and flow rate of the transported gas, the structure of the semiconductor film composed of the semiconductor particles constituting the aggregated particles 54 can be made into a dense film or a porous film. Furthermore, the porosity of the porous membrane can be controlled. In general, the faster the blowing speed of the aggregated particles 54 is, the easier the structure of the produced film becomes denser (the more easily the porosity becomes smaller). In addition, in the case of forming a film at an extremely slow blowing speed, there may be a case where a semiconductor film having sufficient strength cannot be obtained and it becomes a compact. In order to produce a porous film having sufficient structural strength, it is preferable to form the film at a blowing speed intermediate to the speed at which the dense film can be obtained and the speed at which the powder compact can be obtained.

By continuously blowing the agglomerated particles 54, the agglomerated particles 54 continuously collide with the semiconductor particles bonded to the film-forming surface 71 of the substrate 53, and the semiconductor particles constituting the agglomerated particles 54 collide with each other to form a new surface on the surface of each semiconductor particle, The semiconductor particles are bonded to this new surface. At this time, before each semiconductor particle constituting the aggregated particle 54 undergoes brittle deformation, the aggregation of each semiconductor particle is partially released, and a new surface is formed at the portion where the semiconductor particles are in contact with each other to join.

When the porous film made of semiconductor particles has a specific thickness (for example, 1 μm to 100 μm), the blowing of aggregated particles 54 is stopped.

Through the above steps, a porous film of a specific thickness made of semiconductor particles constituting aggregated particles 54 can be formed on the film-forming surface 71 of the base 53.

"Semiconductor Film"

The film structure of the semiconductor film formed on the substrate by the method of manufacturing the semiconductor film of the first embodiment may be a dense film (non-porous film) or a porous film. The film thickness is not particularly limited, and examples thereof include a thickness of about 1 μm to 500 μm.

According to the film formation method of the first embodiment, since aggregated particles composed only of semiconductor particles having a relatively small average particle diameter can be used, and the film formation is performed by the conventional blowing method, the inside of the semiconductor film is not A large number of large-diameter particles that are much larger than the average particle size are mixed. Therefore, the semiconductor film has a uniform film structure, and thus a semiconductor film excellent in strength, conductivity, and light transmittance can be obtained. In the case where the semiconductor film is a porous film, the film strength is also sufficient and uniform, and is sufficiently adhered to a flexible substrate such as a film, so that peeling or breakage is unlikely to occur. Such a characteristic is preferable as a porous film used for the photoelectrode of a flexible dye-sensitized solar cell.

The application of the above-mentioned semiconductor film is not limited to the photoelectrode, and it can be widely used in applications where the physical or chemical properties of the above-mentioned semiconductor film can be used.

《Photoelectrode》

By adsorbing the sensitizing dye to the semiconductor film formed on the substrate by the manufacturing method of the semiconductor film of the first embodiment, it can be used as a photoelectrode. The semiconductor film may be a dense film, but from the viewpoint of adsorbing more sensitizing dyes, a porous film is preferred.

The type of sensitizing dye is not particularly limited, and known sensitizing dyes can be used. In the application of the photoelectrode, it is preferable to form the above-mentioned semiconductor film on a substrate on which a known transparent conductive film is formed. The method of adsorbing the sensitizing dye to the above-mentioned semiconductor film is not particularly limited, and examples thereof include a method of immersing the semiconductor film in the dye solution.

The above-mentioned photoelectrode can be manufactured by a conventional method except that the semiconductor film obtained by the film forming method of the first embodiment is used. For example, a photoelectrode formed by forming the above-mentioned porous film on the conductive surface of an ITO glass substrate and adsorbing the sensitizing dye to the porous film, and then connecting a lead to the above-mentioned conductive near the porous film if necessary Surface to produce a photoelectrode substrate.

When the semiconductor film is a porous film, the porosity (sometimes referred to as porosity, fine porosity, or porosity) is preferably 50% or more, more preferably 50 to 85%, and further preferably 50~75%, especially 50~65%.

If it is above the lower limit of the above range, more sensitizing dyes can be carried. If it is below the upper limit of the above range, the strength of the porous membrane can be made stronger.

Here, the porosity means "the percentage of the volume of voids per unit volume of the porous membrane produced". This porosity can be calculated from porosity=volume specific gravity/true specific gravity×100(%). The volume specific gravity is obtained by dividing the mass per unit volume of the porous membrane by the mass (theoretical value) of particles of the inorganic substance per unit volume, and the true specific gravity means the specific gravity of the semiconductor particles (theoretical value).

The porosity can be measured by a known gas adsorption test or mercury penetration test.

When the semiconductor film is a porous film, the thickness of the porous film is preferably 1 μm to 200 μm, more preferably 2 μm to 100 μm, and still more preferably 5 μm to 50 μm.

If it is more than the lower limit of the above range, the probability of the sensitizing dye supported on the porous membrane absorbing light energy can be further increased, and the photoelectric conversion efficiency of the dye-sensitized solar cell can be further improved. Moreover, if it is below the upper limit of the above range, the electrolyte of the main body (electrolyte in the solar cell) and the electrolyte in the porous membrane can be exchanged more efficiently by diffusion, And further improve the photoelectric conversion efficiency.

"Dye Sensitized Solar Cell"

The dye-sensitized solar cell of the second embodiment of the present invention includes: a photoelectrode, a counter electrode, and electrolysis in which a sensitizing dye is adsorbed to the semiconductor film obtained by the method for manufacturing a semiconductor film of the first embodiment Liquid or electrolyte layer. Preferably, the electrolyte is sealed between the photoelectrode and the counter electrode by the sealing material.

As the base material on which the semiconductor film constituting the photoelectrode is formed, a resin film or resin sheet having a transparent conductive film formed on the surface can be used.

As the above resin, those having visible light permeability are preferred, and examples thereof include polyacrylic acid, polycarbonate, polyester, polyimide, polystyrene, polyvinyl chloride, and polyamide. Among these, polyester, especially polyethylene terephthalate, is preferred as the transparent heat-resistant film, and can be used to manufacture thin and light flexible dye-sensitized solar cells.

The electrolyte is not particularly limited, and for example, a well-known dye-sensitized solar cell electrolyte can be used. Redox couples (electrolytes) are dissolved in the electrolyte, and other additives such as fillers or thickeners may also be included. Also, a well-known solid electrolyte can be used instead of the electrolyte.

The solid electrolyte is in a gel or solid state. By using a gel-like or solid electrolyte layer, there is no longer any risk of electrolyte leakage from the dye-sensitized solar cell.

The type of the sealing material is not particularly limited, and a known sealing resin for dye-sensitized solar cells can be used. For example, ultraviolet curable resin, thermosetting resin, thermoplastic resin, etc. are mentioned. The thickness of the above-mentioned sealing material is not particularly limited, and the photoelectrode and the counter electrode film are spaced at a specific interval so that the electrolyte or the electrolyte layer is adjusted to a specific thickness.

The dye-sensitized solar cell of the second embodiment can be manufactured by a conventional method except for using the above-mentioned photoelectrode. For example, it can be produced by arranging and sealing the electrolyte or electrolyte between the photoelectrode and the counter electrode, and electrically connecting a lead to the photoelectrode and/or counter electrode as necessary.

[Example]

Next, the present invention will be described in more detail with examples, but the present invention is not limited to these examples.

[Example 1]

As the base material, an ITO-PEN substrate formed by previously filming ITO (tin-doped indium oxide) on a PEN (polyethylene naphthalate) substrate was used.

<Preparation of agglomerated particles>

As the inorganic oxide semiconductor particles, anatase TiO ₂ particles having an average particle diameter of about 21 nm are used. The titanium dioxide particles were dispersed in ethanol at 30 wt%, the dispersion liquid obtained by sufficiently dispersing was allowed to stand, and the titanium dioxide particles were precipitated to the bottom of the container. Keeping this static state, ethanol was evaporated under a reduced pressure of less than 30°C, and the titanium dioxide particles were dried.

The particle size distribution of the aggregated particles obtained by drying was measured with a laser diffraction particle size distribution meter, and as shown in FIG. 2, it was confirmed that the aggregated particles with a particle size distribution of 0.1 μm to 10 μm and having a unimodal peak . According to the particle size distribution diagram of FIG. 2, the prepared agglomerated particles have parameters of d10=about 0.4 μm, d50=about 1.5 μm, modal particle size=about 1.8 μm, and d90=about 4.0 μm.

Furthermore, the aggregated particles were observed with an electron microscope to obtain the SEM image shown in FIG. 3. From this SEM image, it is confirmed that the aggregated particles are easily approximated to the shape of a sphere, and The semiconductor particles constituting the aggregated particles are closely aggregated with each other. It was confirmed that because of such a tightly aggregated state, when the aggregated particles are blown, the aggregated particles are not crushed before reaching the substrate, but can collide with the substrate in the form of aggregated particles.

<film making>

Using the film forming apparatus 60 shown in FIG. 1, the agglomerated particles are blown onto the ITO-PEN substrate from the nozzle 52 having a rectangular opening of 10 mm×0.5 mm in the film forming chamber 51. At this time, N ₂ as the transport gas is supplied from the gas tank 55 to the transport pipe 56, and its flow rate is adjusted by the mass flow controller 57. The agglomerated particles for blowing are loaded into the aerosol generator 58 to be dispersed into the conveying gas, conveyed to the crusher 59 and the classifier 61, and sprayed from the nozzle 52 to the substrate 53. A vacuum pump 62 is connected to the film forming chamber 51, and the film forming chamber is set to a negative pressure. The conveying speed in the nozzle 52 is set to 5 mm/sec.

By blowing the agglomerated particles onto the base material, a porous membrane in which titanium dioxide particles constituting the agglomerated particles are bonded to each other is successfully produced. The SEM image obtained by observing the cross section of the porous membrane with an electron microscope is shown in FIG. 4. From this SEM image, it was confirmed that a uniform film structure in which titanium dioxide particles were sufficiently bonded was formed.

[Comparative Example 1]

<Preparation of raw material particles>

The titanium dioxide particles used in Example 1 were used as raw material particles without being dispersed in ethanol and dried.

The raw material particles were observed with an electron microscope to obtain the SEM image shown in FIG. 5. According to this SEM image, agglomerates of a plurality of aggregates were observed in the raw material particles. However, compared with the aggregated particles of Example 1, the aggregated particles are not uniform in particle size and are small particles. Also, due to A large amount of shadows were observed on the surface of the agglomerates, so it was confirmed that the degree of agglomeration was weak and the state was relatively loose. It is believed that because of this loose agglomerated state, when the raw material particles are blown, the agglomerated particles are crushed before reaching the substrate, and it is relatively difficult to collide the substrate in the form of agglomerates, even if they collide in the form of agglomerates It is easy to be crushed on the surface of the substrate, and it is difficult to obtain the energy required for film formation (bonding of particles to each other).

<film making>

Using the above-mentioned raw material particles, blowing was performed in the same manner as in Example 1 to produce a porous membrane.

As a result, a porous film with a specific thickness was barely obtained, but compared with Example 1, the blowing time required for film formation was longer, and the amount of particles to be blown was larger.

"Manufacture of Dye-Sensitized Solar Cells and Their Performance Evaluation"

Each substrate provided with the porous membrane of Example 1 and Comparative Example 1 was immersed in an alcohol solution of 0.3 mM Ru complex pigment (N719, manufactured by Solaronix) at room temperature for 18 hours to adsorb the pigment to the porous On the plasma membrane, thereby obtaining a photoelectrode substrate.

A photoelectrode substrate and a counter electrode substrate made of a platinum-coated glass substrate are arranged to face each other, and a resin film (Himilan, manufactured by Du Pont Mitsui Polychemicals) with a thickness of 30 μm is sandwiched therebetween as a spacer, using a double jig Fix it and perform crimping. Furthermore, after injecting an electrolyte (Iodolyte 50, manufactured by Solaronix Co., Ltd.) between the two substrates through an injection hole pre-opened in the counter electrode substrate, the injection hole is plugged with a glass plate, thereby making it easy to manufacture a dye-sensitized solar cell unit. The effective area of receiving light is 0.16cm ² .

The solar simulator (AM1.5, 100 mW/cm ² ) was used to evaluate the photoelectric conversion efficiency and other properties of the simple unit obtained in each test example. The results are shown in Table 1. In addition, the results obtained by comparing the VI characteristics of each simple unit are shown in FIG. 6.

The substrates on which the porous films of Example 1 and Comparative Example 1 were formed were bent so as to adhere to a cylinder with a radius of curvature R=3 cm. The porous membrane of Example 1 did not peel off during the deformation of the substrate, and the titanium dioxide particles constituting the porous membrane did not fall off. From this result, it was confirmed that the bonding between the particles and the bonding between the particles and the substrate were excellent.

The porous membrane of Comparative Example 1 immediately peeled off during the deformation of the substrate. It is considered that the porous membrane of Comparative Example 1 is in a state close to a compacted powder (only a powder block is placed on a substrate). The fact that the amount of pigment adsorption is small and the power generation characteristics are poor also supports this conclusion.

From the above results, it is clear that the simple unit of Example 1 has a photoelectric conversion efficiency (Eff.) greater than that of Comparative Example 1, and is more excellent as a solar cell. This result is considered to be reflected in the porous film constituting the photoelectrode, the semiconductor particles are excellent in bonding, and the electron conductivity and light transmittance are improved.

[Example 2]

Except that methanol was used instead of ethanol, aggregated particles were prepared in the same manner as in Example 1 to produce a porous membrane composed of titanium dioxide particles. When the SEM image of the obtained porous film was observed, it was confirmed that it had a uniform film structure in which titanium dioxide particles were sufficiently bonded. A simple unit equipped with the porous membrane was produced in the same manner as in Example 1, and good results were obtained Power generation characteristics.

[Example 3]

Except that 1-pentanol was used instead of ethanol, aggregated particles were prepared in the same manner as in Example 1 to produce a porous film composed of titanium dioxide particles. When the SEM image of the obtained porous film was observed, it was confirmed that it had a uniform film structure in which titanium dioxide particles were sufficiently bonded. A simple unit equipped with the porous membrane was produced in the same manner as in Example 1, and good power generation characteristics were obtained.

[Example 4]

Instead of ethanol, isopropyl alcohol, which is a secondary alcohol, was used to prepare aggregated particles in the same manner as in Example 1 to produce a porous film composed of titanium dioxide particles. When the SEM image of the obtained porous film was observed, it was confirmed that it had a uniform film structure in which titanium dioxide particles were sufficiently bonded. A simple unit equipped with the porous membrane was produced in the same manner as in Example 1, and good power generation characteristics were obtained.

[Example 5]

Except for using ethanol as the tertiary alcohol instead of ethanol, aggregated particles were prepared in the same manner as in Example 1 to produce a porous membrane composed of titanium dioxide particles. When the SEM image of the obtained porous film was observed, it was confirmed that it had a uniform film structure in which titanium dioxide particles were sufficiently bonded. A simple unit equipped with the porous membrane was produced in the same manner as in Example 1, and good power generation characteristics were obtained.

The configurations and combinations of the embodiments described above are examples, and additions, omissions, substitutions, and other changes to the configurations can be made without departing from the scope of the invention. Moreover, the present invention is not limited by each embodiment, but only by the scope of patent application (claim).

[Industry availability]

The method for manufacturing a semiconductor film of the present invention can be widely used in the field of solar cells.

Claims (6)

A method for manufacturing a semiconductor film, which obtains a dispersion liquid obtained by dispersing semiconductor particles having an average particle diameter of 1 nm or more and less than 100 nm in an alcohol of 4° C. or more and 55° C. or less, at a temperature of less than 50° C. The temperature evaporates the alcohol from the dispersion to dry the semiconductor particles, thereby obtaining aggregated particles obtained by aggregating the semiconductor particles, and the semiconductor is produced on the substrate by blowing the aggregated particles to the substrate membrane. A method of manufacturing a semiconductor film according to claim 1, wherein the semiconductor particles are deposited in the alcohol, and the alcohol is evaporated to dry the semiconductor particles. The method for manufacturing a semiconductor film according to item 1 or 2 of the patent application, wherein the semiconductor particles are particles of a metal oxide semiconductor. For example, in the method of manufacturing a semiconductor film according to item 1 or 2, the above-mentioned semiconductor film is a porous film. A method for manufacturing a semiconductor film according to item 3 of the patent application, wherein the semiconductor film is a porous film. A dye-sensitized solar cell, comprising: a photoelectrode in which a sensitizing dye is adsorbed to a semiconductor film obtained by the method for manufacturing a semiconductor film according to any one of claims 1 to 5.

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