JP2008163396A - Electrolytic deposition apparatus, electrolytic deposition method and photoelectric transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric transducer capable of obtaing an excellent photoelectric transformation efficiency, and to provide an electrolytic deposition apparatus and an electrolytic deposition method by which the photoelectric transducer can be manufactured. <P>SOLUTION: The electrolytic deposition apparatus 1 is provided with a gas storage part 10, an electrolytic bath 11, a microbubble generating part 13, a pump 14, a gas supply line 15 and electrolyte circulation line 16. A first substrate 20 and a second substrate 21 are oppositely arranged in the electrolytic bath 11 and are impregnated with the electrolyte 12. After microbubbles are generated in the electrolyte 12 by the microbubble generating part 13, voltage is applied between the first substrate 20 and the second substrate 21 to carry out the electrolytic deposition. By controlling floating speed of the microbubbles to 8 cm/sec particularly, the gas floating on the electrolyte and discharged to air is remarkably reduced to effectively increase the gas concentration dissolved in the electrolyte. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolytic deposition apparatus and an electrolytic deposition method for electrochemically depositing a substance, and a photoelectric conversion element produced using these.

  Conventionally, in a photoelectric conversion element such as a solar cell, a porous thin film such as an oxide semiconductor film is provided to support a dye having a photosensitizing action between a pair of electrodes. In such a thin film formation process of a photoelectric conversion element, a sintering method or the like in which an oxide semiconductor is baked on an electrode to form a film has been used. However, in recent years, electrolytic deposition (electrodeposition, electrolytic plating, Electroplating, electrolytic plating, electroplating, electroplating, and electroplating methods are attracting attention. This electrolytic deposition method is a method of forming a film by depositing a substance by applying a voltage between a pair of electrodes impregnated in an electrolytic solution.

  In general, in the electrolytic deposition method as described above, for the purpose of promoting the electrolytic deposition reaction, there are many bubbling techniques in which a certain gas is convected as bubbles in the electrolytic solution and the electrolytic solution is stirred. It's being used.

On the other hand, such bubbling in electrolytic deposition can also be used for the purpose of supplying gas as a material for electrolytic deposition reaction. For example, a technique for forming a zinc oxide (ZnO) film by bubbling oxygen (O ₂ ) as an electrolytic deposition material in an electrolytic solution containing a zinc salt and performing electrolytic deposition is disclosed. (For example, Non-Patent Document 1).

Here, FIG. 8 shows a schematic diagram of a conventional electrolytic deposition apparatus that performs electrolytic deposition by supplying a gaseous material by bubbling. This apparatus includes a gas storage unit 100 and a gas supply line 104 that supply gas to the electrolytic bath 101, a pump 103 and an electrolytic solution circulation line 105 for circulating the electrolytic solution 102, and a pair of impregnated electrolytic solutions 102. The first substrate 200 and the second substrate 201 serving as the electrodes, and a chamber 300 which is provided on the bottom surface of the electrolytic bath 101 and introduces the gas supplied from the gas supply line 104 into the electrolytic solution 102. The chamber 300 is provided with an orifice hole 300 a, whereby the gas becomes bubbles and is bubbled into the electrolytic solution 102. With such a configuration, the bubbled bubbles react with ions in the electrolytic solution 102 to form electrolytic deposits on the first substrate 200.
Sophie Peulon and Daniel Lincot, Adv. Mat., 8, 166-170 (1996)

  However, in the bubbling using the orifice structure as described above, many of the supplied bubbles float on the electrolytic bath before being dissolved in the electrolytic solution and used for the electrolytic deposition reaction. The concentration of the gas dissolved in the electrolytic solution is lowered. Therefore, when a thin film of a photoelectric conversion element is formed by such electrolytic deposition, the dissolved oxygen concentration at the time of electrolytic deposition is low and the concentration distribution varies, so the crystallinity of the deposited film is non-uniform. Thus, there is a problem that the photoelectric conversion efficiency is lowered.

  The present invention has been made in view of such problems, and the object thereof is a photoelectric conversion element capable of realizing good photoelectric conversion efficiency, and an electrolytic deposition apparatus capable of producing such a photoelectric conversion element and It is to provide an electrolytic deposition method.

  The electrolytic deposition apparatus according to the present invention is an electrolytic bath containing an electrolytic solution, means for applying a voltage to a pair of conductive substrates immersed in the electrolytic solution, and a material for electrolytic deposition in the electrolytic solution. And a microbubble generating means for generating microbubbles containing gas.

  The electrolytic deposition method according to the present invention includes a step of applying a voltage between a pair of conductive substrates immersed in an electrolytic solution having microbubbles containing a gas as a material for electrolytic deposition.

  The electrolytic deposition solution according to the present invention contains oxygen as microbubbles.

  The photoelectric conversion element according to the present invention includes a first electrode having an oxide semiconductor film carrying a dye on its surface, a second electrode provided to face the first electrode, and a first electrode and a second electrode. The oxide semiconductor film is formed using the above electrolytic deposition apparatus.

  In the electrolytic deposition apparatus and the electrolytic deposition method according to the present invention, when a predetermined voltage is applied between a pair of conductive substrates after bubbling microbubbles into the electrolytic solution by the microbubble generating means, A substance is deposited on the conductive substrate by the electrolytic deposition reaction between the materials containing the ions and the gas supplied as microbubbles. By supplying the gas as the material for electrolytic deposition as microbubbles, the gas stays in the electrolytic solution for a long time. This reduces the amount of gas that floats on the electrolytic bath and is released into the atmosphere, and increases the concentration of gas dissolved in the electrolytic solution.

  Further, in the electrolytic deposition apparatus according to the present invention, if the ascending speed of the microbubbles is 8 cm / second under the conditions of atmospheric pressure and 20 ° C., the amount of gas released into the atmosphere is greatly reduced, The dissolved gas concentration in the electrolytic solution is effectively increased.

Furthermore, in the electrolytic deposition apparatus according to the present invention, as long as the microbubbles contain oxygen (O ₂ ) and the electrolyte contains zinc ions (Zn ²⁺ ), zinc oxide (ZnO) having uniform crystallinity. ) A film is deposited.

  The electrolytic deposition apparatus according to the present invention further comprises a gas supply means for supplying a gas to the microbubble generating means, and an electrolyte supply means for supplying an electrolyte to the microbubble generating means, the microbubble generating means being If the gas supplied by the gas supply means and the electrolyte supplied by the electrolyte supply means are swirled at a high speed to generate microbubbles together with the jet, the jet makes it possible to stir the electrolyte. Increases and promotes the electrolytic deposition reaction.

  In the electrolytic deposition solution according to the present invention, since oxygen is contained as microbubbles, oxygen stays in the solution for a long time, and the oxygen concentration increases.

  In the photoelectric conversion element according to the present invention, the oxide semiconductor film provided between the electrodes is formed by the electrolytic deposition apparatus according to the present invention, so that the dissolved oxygen concentration in the electrolytic solution is effective at the time of electrolytic deposition. To increase. Accordingly, the crystallinity of the oxide semiconductor film is made uniform.

  According to the electrolytic deposition apparatus and the electrolytic deposition method according to the present invention, an electrolytic bath containing an electrolytic solution, a means for applying a voltage to a pair of conductive substrates immersed in the electrolytic solution, and a microbubble generating microbubbles Since the bubble generating means is provided, the amount of gas that floats on the electrolytic bath and is released into the atmosphere is reduced, and the concentration of gas dissolved in the electrolyte is increased. Can be improved. Therefore, a photoelectric conversion element having good photoelectric conversion efficiency can be manufactured.

  In addition, if the ascending speed of the microbubbles generated from the microbubble generating means is 8 cm / second or less under the conditions of atmospheric pressure and 20 ° C., the amount of gas released into the atmosphere is greatly reduced. Since the dissolved gas concentration in the electrolytic solution is effectively increased, the gas utilization efficiency and the film forming speed can be effectively improved.

  According to the electrolytic deposition solution of the present invention, since oxygen is contained as microbubbles, the concentration of oxygen contained in the electrolytic bath is increased, and the electrolytic deposition with improved oxygen utilization efficiency and film forming speed is achieved. It can be performed.

  According to the photoelectric conversion element of the present invention, the first electrode having an oxide semiconductor film carrying a dye on its surface, the second electrode provided to face the first electrode, the first electrode and the second electrode And an electrolyte layer provided via an oxide semiconductor film, and the oxide semiconductor film is formed using the electrolytic deposition apparatus according to the present invention. Can be improved. Therefore, good photoelectric conversion efficiency can be maintained.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a schematic configuration of an electrolytic deposition apparatus 1 according to an embodiment of the present invention. The electrolytic deposition apparatus 1 is an apparatus for forming a film of a substance using an electrolytic deposition reaction, and particularly has a mechanism for supplying (bubbling) a gas as a raw material for the electrolytic deposition reaction. As the material to be electrolytically deposited, an oxide semiconductor such as zinc oxide (ZnO) or titanium oxide (TiO ₂ ) is preferable. This electrolytic deposition apparatus 1 is preferably used in an oxide film forming process of a photoelectric conversion element such as a dye-sensitized solar cell. The electrolytic deposition in the present invention is a concept that widely includes a method of depositing a substance by utilizing an electrochemical reaction, such as electrolytic plating and electroplating.

  The electrolytic deposition apparatus 1 includes a gas storage unit 10, an electrolytic bath 11, a microbubble generation unit 13, a pump 14, a gas supply line 15, and an electrolytic solution circulation line 16. In the electrolytic bath 11, the first substrate 20 and the second substrate 21 are arranged to face each other, and these are impregnated with the electrolytic solution 12. In such an electrolytic deposition apparatus 1, electrolytic deposition generates microbubbles in the electrolytic bath 11 from the microbubble generating unit 13, and then applies a voltage between the first substrate 20 and the second substrate 21. Is done.

The gas storage unit 10 is connected to a gas supply line 15, and the gas supply line 15 is connected to a microbubble generating unit 13 described later. The gas storage unit 10 has, for example, a high-pressure gas container such as a cylinder, a regulator for controlling the gas pressure, and the like, and stores a gas that is a raw material for electrolytic deposition, such as oxygen (O ₂ ). It is what is done. The gas supply line 15 is means for pressure-feeding the gas stored in the gas storage unit 10 to the microbubble generation unit 13.

  The electrolytic bath 11 is a bathtub for electrolytic deposition, and is divided into three tanks: an upstream buffer tank 11a, a reaction tank 11b, and a downstream buffer tank 11c. The reaction tank 11b is a tank that causes an electrolytic deposition reaction. In the reaction tank 11b, the first substrate 20 and the second substrate 21 are impregnated with the electrolytic solution 12. The upstream buffer tank 11a and the downstream buffer tank 11c are provided to adjust the convection speed of the electrolytic solution 12 in the reaction tank 11b. In such a configuration, the electrolyte 12 flows by overflowing from the upstream buffer tank 11a to the reaction tank 11b and from the reaction tank 11b to the downstream buffer tank 11c, and convects in the electrolytic bath 11.

The electrolytic solution 12 is a medium that conducts ions during the electrolytic deposition reaction, and is composed of a solution in which an electrolyte is dissolved in a solvent. For example, when electrolytically depositing zinc oxide, an aqueous solution in which a zinc salt is dissolved in water is used as the electrolytic solution 12. Zinc salts include zinc halides such as zinc chloride (ZnCl ₂ ), zinc bromide (ZnBr ₂ ), and zinc iodide (ZnI ₂ ), zinc nitrate (Zn (NO ₃ ) ₂ ), and zinc perchlorate ( Zn (ClO ₄ ) ₂ ) or the like can be used. Further, the electrolytic solution 12, nitrate ions to promote ionization _- can also be configured to include a (NO ^3). In addition, in order to optimize electrolytic deposition reaction conditions, potassium hydroxide (KOH) for pH control, a pH buffer solution for maintaining pH, and the like may be included.

  The first substrate 20 functions as a cathode in the electrolytic deposition reaction, and is connected to a precision voltage / current source (not shown). The first substrate 20 is a conductive substrate, for example, stainless steel, iron (Fe), tin (Sn), copper (Cu), silver (Ag), gold (Au), platinum (Pt), or other metals such as PEDOT. It is composed of a conductive polymer such as (3,4-ethylenedioxythiophene) or a transparent conductive film such as ITO (indium tin oxide). For example, the first substrate 20 serves as a working electrode when electrolytically depositing zinc oxide, and a zinc oxide film is generated on the conductive surface of the first substrate 20.

  The second substrate 21 functions as an anode in the electrolytic deposition reaction, and is connected to a precision voltage / current source (not shown). The second substrate 21 is made of a conductive substrate, such as platinum or a zinc plate. The second substrate 21 is, for example, a counter electrode when electrolytically depositing a zinc oxide film. Note that the second substrate 21 may be appropriately moved in the electrolytic bath 11 during electrolytic deposition. As the movement means, for example, a rotating disk electrode type electrolyzer, a rotating cylinder electrode type electrolyzer, a vibrating electrode type electrolyzer, a swing electrode type electrolyzer, a constant speed electrode feed type electrolyzer can be used.

  The pump 14 and the electrolytic solution circulation line 16 are means for pushing up the electrolytic solution 12 stored in the downstream buffer tank 11c in the electrolytic bath 11 and returning it to the upstream buffer tank 11a side again. The electrolyte circulation line 16 is connected to a microbubble generator 13 described later.

  Next, the microbubble generator 13 will be described. The microbubble generator 13 is provided, for example, at the bottom of the upstream buffer tank 11 a of the electrolytic bath 11. The microbubble generator 13 has a mechanism for generating microbubbles by, for example, rotating the gas sent through the gas supply line 15 and the electrolyte circulation line 16 to be connected and the electrolyte at high speed. is doing. Thereby, the gas used as the material of an electrolytic deposition reaction is supplied in the electrolytic bath 11 as a microbubble. In the microbubble generator 13, since the electrolyte solution 12 rotates at a high speed, it is preferable that a material that is less reactive with the electrolyte solution 12 is selected as a member constituting the microbubble generator 13. Alternatively, the microbubble generator 13 may be driven intermittently to generate the microbubble intermittently.

Here, FIG. 2 shows a principle diagram of the microbubble generation mechanism in the microbubble generator 13. In the microbubble generator 13, the electrolyte (liquid) and the gas are swirled at a high speed, whereby a gas composed of a swirl liquid portion 130 having the same circular core direction and a swirl gas cavity 131 formed on the inside thereof. It becomes a liquid two-phase structure. At this time, a speed difference is generated in the microbubble generator 13 because the turning speed in the internal region is faster than the turning speed in the vicinity of the bubble outlet 13a. As a result, the swirling gas cavity 131 is cut (microbubble generation point P _B ) and is broken by the swirling liquid flow to generate the microbubble B. For example, a water flow pump such as an aspirator can be used as the microbubble generator 13 having such a mechanism. The aspirator is usually used for the purpose of extracting air from the container, but can generate bubbles on the principle similar to the above.

  Subsequently, the microbubbles B will be described. The microbubbles B are microbubbles, generally called microbubbles (particle diameters of several tens of μm or less), micro-nano bubbles (particle diameters of 10 μm or less), nanobubbles (particle diameters of several hundreds of nm or less), etc. Although it is included, it is preferable to refer to a bubble having a flying speed of 8 cm / second or less in a liquid under conditions of atmospheric pressure and 20 ° C. Note that other conditions such as the viscosity of the liquid are not particularly limited as long as these conditions are satisfied.

  However, the “floating speed” of the bubbles refers to the speed at which the bubbles rise in the liquid at a constant speed. Further, when measuring the ascent rate, bubbles are generated in the bathtub under conditions of atmospheric pressure and 20 ° C., and the bubbles are irradiated with powerful light to scatter the light to rise in the bathtub. The ascent rate of the bubble group at the forefront of the bubble (terminal ascent rate) is measured.

  Next, the operation and effect of the electrolytic deposition apparatus 1 having the above configuration will be described.

  In the electrolytic deposition apparatus 1 according to the present embodiment, when the electrolytic solution 12 fed by the electrolytic solution circulation line 16 and the gas fed by the gas supply line 15 are fed into the microbubble generator 13, the electrolytic solution Due to the high-speed swirling of the gas 12 and the gas, a jet containing the fine bubbles B at a high density is generated. This jet flows from the upstream buffer tank 11a to the reaction tank 11b, stays in the reaction tank 11b, and then flows to the downstream buffer tank 11c. The electrolytic solution 12 stored in the downstream buffer tank 11c is pushed up by the pump 14, and is again pumped to the upstream buffer tank 11a side by the electrolytic solution circulation line 16. As described above, when a predetermined voltage is applied between the first substrate 20 and the second substrate 21 in the reaction tank 11b in a state where the electrolytic solution 12 is circulated and the microbubbles B are generated, Electrodeposition reaction like this occurs.

For example, when zinc salt is present in the electrolyte solution 12 and oxygen is supplied as a gas, first, a reduction reaction represented by the following (1) occurs in the electrolyte solution 12, and oxygen is reduced respectively. Te, OH ^- generates ions. Due to the OH ⁻ ions, the pH in the vicinity of the surface of the first substrate 20 increases. As a result, as shown in (2), zinc hydroxide (Zn (OH) ₂ ) is generated by zinc ions and OH ⁻ ions in the vicinity of the first substrate 20. Thereafter, as shown in (3), zinc oxide (ZnO) is deposited on the surface of the first substrate 20.
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (1)
Zn ²⁺ + 2OH ⁻ → Zn (OH) ₂ (2)
Zn (OH) ₂ → ZnO + H ₂ O (3)

  At this time, the microbubbles B staying in the electrolytic solution 12 in the reaction tank 11b can stay in the electrolytic solution 12 for a longer time because the flying speed is 8 cm / second. . Thereby, gas becomes easy to melt | dissolve in the electrolyte solution 12, and the utilization efficiency of gas improves. Further, since the residence time of the microbubbles B is long, the microbubbles B can be intermittently generated by intermittently operating the microbubble generator 13 instead of always operating. Thereby, since the consumption loss of the gas to supply can be reduced, even if it is a case where the same amount of gas as the past is supplied, the oxygen concentration in the electrolyte solution 12 becomes high. Therefore, the film forming speed is improved as compared with the conventional case.

  In particular, the gas stays in the electrolyte as microbubbles for a long time, and the dissolved oxygen concentration increases, so that the nucleation of the deposited substance is promoted and the crystal grows finely. Thereby, the uniformity of the crystal | crystallization of the film | membrane to precipitate can be ensured. Therefore, by electrolytic deposition using such microbubbles B, for example, an oxide semiconductor film such as zinc oxide is formed, and this is used for a photoelectric conversion element such as a dye-sensitized solar cell. Efficiency can be improved.

  Further, a gas supply line 15 for supplying gas and an electrolyte circulation line 16 for supplying the electrolyte 12 are provided to the microbubble generator 13, and the microbubble generator 13 is supplied by the gas supply line 15. The gas 12 and the electrolyte solution 12 supplied from the electrolyte circulation line 16 are swirled at a high speed, thereby having a mechanism for generating the microbubbles B together with the jet flow, so that the agitation of the electrolyte solution 12 is enhanced. The electrolytic deposition reaction is accelerated.

  At this time, by providing the upstream buffer tank 11a, the convection velocity of the electrolyte solution 12 can be adjusted by appropriately suppressing the momentum of the jet including the microbubbles B generated from the microbubble generator 13. Thereby, in the reaction tank 11b, the residence time of the microbubbles B can be secured while maintaining the stirring property of the electrolyte solution 12, which is advantageous in improving the gas utilization efficiency and the film forming speed.

  Here, FIG. 3 shows the bubble radius (mm) and the ascent rate (m / sec) in water (A in the figure) and in the ethyl alcohol cottonseed oil mixture (B in the figure) under an atmospheric pressure of 20 ° C. The characteristic figure about the relationship is shown. As described above, it is known that there is a correlation as shown in FIG. 4 between the bubble particle size and the flying speed in a stationary liquid (Non-Patent Document 2). In general, the rising speed of bubbles in a liquid is proportional to the square of the bubble radius and inversely proportional to the viscosity of the liquid, so the relationship between the bubble diameter and the rising speed is not uniquely determined. Is 1 mm or less, the rising speed tends to increase as the bubble diameter increases regardless of the viscosity of the liquid. That is, the smaller the ascent rate, the smaller the bubble diameter. Therefore, the electrolyte solution 12 that is normally used is an aqueous solution, and its viscosity can be approximated to the viscosity of water. Therefore, when the ascent rate is 8 cm / second or less, the particle size of the microbubbles B is 0.7 mm or less. . As a result, the specific surface area of the microbubbles B with respect to the electrolytic solution 12 is increased, and the material is effectively transported between the electrolytic solution 12 and the gas, which is advantageous in improving the film forming speed.

  Next, a modification of the electrolytic deposition apparatus 1 according to the present embodiment will be described. In addition, about the structure similar to the electrolytic deposition apparatus 1, the same code | symbol is attached | subjected and description about the effect | action and effect is abbreviate | omitted.

(Modifications 1 and 2)
FIG. 4 is a schematic diagram illustrating a schematic configuration of the electrolytic deposition apparatus 2 according to the first modification. This electrolytic deposition apparatus 2 is the above electrolytic deposition apparatus except that no barrier is provided in the electrolytic bath 31 and it is not divided into three tanks of an upstream buffer tank 11a, a reaction tank 11b, and a downstream buffer tank 11c. 1 has the same configuration.

  In the electrolytic deposition apparatus 2, the microbubble generator 13, the first substrate 20, and the second substrate 21 are disposed in the same bath in the electrolytic bath 31, and the electrolytic solution 12 that has convected the electrolytic bath 11 is The pump 14 is directly pushed up. With such a configuration, the jet of the electrolyte solution 12 containing the microbubbles B generated from the microbubble generator 13 convects in the electrolytic bath 11 as it is, and then is sucked into the pump 14 side. Thereby, in the electrolytic bath 11, the stirring property is increased, and the substance transport is effectively performed, thereby promoting the electrolytic deposition reaction.

  FIG. 5 is a schematic diagram illustrating a schematic configuration of the electrolytic deposition apparatus 3 according to the second modification. This electrolytic deposition apparatus 3 has the same configuration as the electrolytic deposition apparatus 1 except that the microbubble generating unit 33 is provided in the upper part of the upstream buffer tank 11a.

  Thus, the microbubble generation part 33 is not restricted to the bottom part of the upstream buffer tank 11a like the electrolytic deposition apparatus 1, and may be arrange | positioned at the upper part. The arrangement of the microbubble generator is appropriately set depending on the balance between the required residence time and the stirring ability. Similarly, the height and arrangement of the barrier forming the upstream buffer tank 11a are not particularly limited.

  Hereinafter, examples of the electrolytic deposition apparatus 1 according to the present embodiment will be described.

(Example 1)
As Example 1, a zinc oxide film was formed using the electrolytic deposition apparatus 1 shown in FIG. At that time, the gas supplied as microbubbles was oxygen, and the ascending speed (atmospheric pressure, 20 ° C.) was set to 6 cm / second. The first substrate 20 is a TCO substrate (A110U80 (trade name) manufactured by Asahi Glass Fabrictech Co., Ltd.), the second substrate 21 is a zinc plate, the electrolyte solution 12 is a 0.1 mol / l potassium chloride aqueous solution and 0 A 0.005 mol / l aqueous zinc chloride solution was used. The voltage was applied from a precision voltage current source at −1.0 V (vs SCE), and the electrolytic deposition time was 20 minutes.

  In the electrolytic deposition under such conditions, when intense light is irradiated from behind the electrolytic bath 11, the inside of the bath becomes cloudy due to the light scattering phenomenon caused by the microbubbles, the electrolyte solution 12 circulates, and the microbubbles stay. It was confirmed. Moreover, the surface state of the formed zinc oxide film was evaluated with an optical microscope (2500 times). The results are shown in FIG. Furthermore, the amount of charge (C) flowing into the system during electrolytic deposition and the film thickness (μm) of the zinc oxide film were also measured. The results are shown in Table 1.

  Further, as Comparative Example 1 with respect to Example 1, the conventional electrolytic deposition apparatus shown in FIG. 8 was used, except that the rising speed of the supplied bubbles (atmospheric pressure, 20 ° C.) was 20 cm / second. Electrodeposition was performed under the same conditions as in Example 1 to form a zinc oxide film. The surface condition of the zinc oxide film according to Comparative Example 1 formed in this way was also evaluated in the same manner as in Example 1 above, and the charge amount (C) and the film thickness (μm) of the zinc oxide film were measured. . The results are shown in FIG.

  As shown in Table 1, the zinc oxide film of Example 1 has a film thickness of 3.0 μm and a charge amount of 0.62 C, and the zinc oxide film of Comparative Example 1 has a film thickness of 1.2 μm and a charge amount. Was 0.23C. From these results, even when the electrolytic deposition time, the applied voltage, and the oxygen consumption amount are the same, the amount of charge flowing in the system is increased in Example 1 as compared with Comparative Example 1, and the formed film It can be seen that the thickness also increases. Therefore, it was shown that the gas utilization efficiency and the film forming speed are improved as compared with the conventional electrolytic deposition.

  Further, as shown in FIG. 6B, it can be seen that the surface state of the zinc oxide film of Comparative Example 1 has non-uniform crystallinity. This is considered to be because, in the conventional apparatus, the distribution of oxygen concentration dissolved in the electrolytic bath is low and non-uniform, so that nucleation occurs only in a specific region, followed by crystal growth. In contrast, as shown in FIG. 6A, the surface state of the zinc oxide film of Example 1 is found to have uniform crystallinity. This is considered to be because the distribution of oxygen concentration dissolved in the electrolytic bath is high and uniform, so that nucleation is promoted and crystal growth occurs finely.

(Example 2)
As Example 2, a zinc oxide film was formed using the electrolytic deposition apparatus 1 shown in FIG. 1, and a dye-sensitized photoelectric conversion element was manufactured using this zinc oxide film. In the electrolytic deposition of the zinc oxide film, the gas supplied as microbubbles is oxygen, and the first substrate 20 includes a TCO substrate (A110U80 (trade name) manufactured by Asahi Glass Fabrictech Co., Ltd.) and the second substrate 21 includes As the zinc plate and the electrolyte solution 12, a 0.1 mol / l potassium chloride aqueous solution and a 0.005 mol / l zinc chloride aqueous solution were used. Under such conditions, the rising speed of microbubbles (atmospheric pressure, 20 ° C.) is 1.6, 5.0, 7.6, 8.5, 13.9 (cm / sec). Electrodeposition was performed for each. The voltage was applied at −1.0 V (vs SCE) from a precision voltage current source, and the electrolytic deposition time was 20 minutes.

  Subsequently, after each formed zinc oxide film was dyed with a dye having photosensitization property, a minicell was produced by sandwiching an electrolyte between the zinc oxide film and an electrode obtained by sputtering platinum on a TCO substrate. The electrolyte used was a solution of tetrapropylammonium iodide in an acetonitrile solvent, and eosin Y was used as the dye. The photoelectric conversion efficiency (%) of the minicell thus produced was measured. The results are shown in FIG.

  As shown in FIG. 7 and Table 2, the photoelectric conversion efficiency decreases as the flying speed of the microbubbles increases. In particular, when the flying speed exceeds 8 cm / second, the photoelectric conversion efficiency rapidly decreases (1% It can be seen that On the other hand, when the flying speed is 8 cm / second or less, the photoelectric conversion efficiency can be maintained at about 3% or more, and the characteristics of the photoelectric conversion element are greatly improved. This is considered to be because when the ascending speed is 8 cm / sec or less, the time for staying in the electrolytic solution becomes longer, so that the dissolved oxygen concentration becomes higher and the crystallinity of the electrolytically deposited film becomes uniform. . Therefore, it was shown that the photoelectric conversion efficiency is improved when the ascending speed of the microbubbles is 8 cm / second or less under the conditions of atmospheric pressure and 20 ° C.

Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to these embodiments and the like, and various modifications are possible. For example, in the above-described embodiment and the like, the case where zinc oxide is electrolytically deposited by supplying (bubbling) oxygen to an electrolytic solution containing a zinc salt has been described. However, the present invention is not limited thereto, and gas is used as a raw material. For the purpose of supply, other substances such as titanium oxide (TiO ₂ ) may be deposited. Similarly, for the purpose of supplying gas as a raw material, it can be applied to electrolytic plating (electroplating), electroplating (electroplating), and the like. The arrangement of the microbubble generator 13 in the electrolytic bath 11 may be any configuration that can generate microbubbles in the electrolytic solution 12 and is not limited to the above-described form.

It is a schematic diagram showing schematic structure of the electrolytic deposition apparatus which concerns on one embodiment of this invention. It is a principle figure of the microbubble generating part concerning one embodiment of the present invention. It is a characteristic view showing the relationship of the ascent rate to the bubble radius. It is a schematic diagram showing schematic structure of the electrolytic deposition apparatus which concerns on the 1st modification of this invention. It is a schematic diagram showing schematic structure of the electrolytic deposition apparatus which concerns on the 2nd modification of this invention. It is the photograph which image | photographed the surface state of the zinc oxide film | membrane which concerns on the Example of this invention with the optical microscope. It is a characteristic view showing the relationship of the photoelectric conversion efficiency with respect to the bubble floating speed of the photoelectric conversion element which concerns on the Example of this invention. It is a schematic diagram showing schematic structure of the conventional electrolytic deposition apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Electrolytic deposition apparatus, 10 ... Gas storage part, 11, 31 ... Electrolytic bath, 11a ... Upstream buffer tank, 11b ... Reaction tank, 11c ... Downstream buffer tank, 12 ... Electrolyte, 13 ... Microbubble Generating part, 14 ... pump, 15 ... gas supply line, 16 ... electrolyte supply line, 20 ... first substrate, 21 ... second substrate.

Claims (11)

An electrolytic bath containing an electrolytic solution;
Means for applying a voltage to a pair of conductive substrates immersed in the electrolytic bath;
An electrolytic deposition apparatus comprising: microbubble generating means for generating microbubbles containing a gas as a material for electrolytic deposition in the electrolytic solution. 2. The electrolytic deposition apparatus according to claim 1, wherein a particle size of the microbubbles is such that a flying speed is 8 cm / second or less under conditions of atmospheric pressure and 20 ° C. 3. The electrolytic deposition apparatus according to claim 1, wherein the gas contains oxygen (O ₂ ). 4. The electrolytic deposition apparatus according to claim 1, wherein a metal oxide is deposited on the conductive substrate. 5. 5. The electrolytic deposition apparatus according to claim 1, wherein the electrolytic solution contains zinc ions (Zn ²⁺ ). Gas supply means for supplying gas to the microbubble generating means;
An electrolyte supply means for supplying the electrolyte solution to the microbubble generating means,
The microbubble generating means generates microbubbles together with a jet by rotating the gas supplied by the gas supply means and the electrolyte supplied by the electrolyte supply means at high speed. Item 6. The electrolytic deposition apparatus according to any one of Items 1 to 5. A method of electrolytic deposition, comprising applying a voltage to a pair of conductive substrates immersed in an electrolytic solution having microbubbles containing a gas that is a material for electrolytic deposition. An electrolytic deposition solution comprising oxygen as microbubbles. The raw material which can become an oxide is contained. The solution for electrolytic deposition of Claim 8 characterized by the above-mentioned. The solution for electrolytic deposition according to claim 9, wherein the raw material is zinc ion (Zn ²⁺ ). A first electrode having an oxide semiconductor film carrying a dye on its surface;
A second electrode provided facing the first electrode;
An electrolyte layer provided between the first electrode and the second electrode;
The photoelectric conversion element, wherein the oxide semiconductor film is formed using the electrolytic deposition apparatus according to any one of claims 1 to 7.

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