JPH10140373A - Production of zinc oxide thin film, semiconductor device substrate using the same and photovolatic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a uniform zinc oxide thin film excellent in adhesion by forming a primary zinc oxide thin film on a substrate by a supporting method and electrolytically precipitating a secondary zinc oxide thin film thereon by using a suitable electrolyte. SOLUTION: Primary zink oxide thin film is formed on a substrate 103 by a supporting method. As this substrate, a stainless steel, glass coated with aluminum or the like can be used. The substrate 103 is immersed in an aq. soln. stored in a corrosion resistance vessel 101 and is used as a cathode, and energizing is executed to the space between it and a counter electrode 104 as an anode. Thid aq. soln 102 contains nitric acid ions and zinc ions respectively by about 0.001 to 1.0mol/l and contains carbohydrates such as monosaccharides by 0.001 to 1.0mol/l, and its temp. is regulated to >=50 deg.C. Furthermore, the current density of the electric current is preferably regulated to 10mA to 10A/dm<2> . Moreover, as the counter electrode 104, a zinc electrode is preferably used. In this way, the secondary zinc oxide thin film is formed on the primary zinc oxide thin film with tight adhesion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a zinc oxide thin film and a photovoltaic element using the same.

[0002]

2. Description of the Related Art It has been known that a photovoltaic element is provided with a reflective layer on the back surface of a semiconductor layer in order to improve the collection efficiency at a long wavelength. Further, by providing a transparent conductive layer having irregularities between the metal layer and the semiconductor layer,
It is known that there is an optical confinement effect of extending the optical path length of the reflected light and an effect of suppressing the flow of an excessive current during shunting. For the transparent conductive layer, ZnO formed by a sputtering method is widely used.

[0003] For example, "aS on a 29p-MF-22 stainless steel substrate"
Light confinement effect in iGe solar cells ”(Fall 1990) 5
Proceedings of the 1st JSAP Academic Lecture Meeting p747, or "
P-IA-15a-SiC / a-Si / a-SiGe Multi-Bandgap Stacked So
lar Cells With Bandgap Profiling, "Sannomiya et a
l., Technical Digest of the International PVSEC-5, K
Yoto, Japan, p381, 1990 states that a combination of a reflective layer and a zinc oxide layer achieved an increase in short-circuit current due to the optical confinement effect.

On the other hand, "Electrolyte Optimization for Ca"
thodic Growth of Zinc Oxide Films "M. IZAKI and
T. Omi J. Electrochem. Soc., Vol.143, March 1996, L5
3 and JP-A-8-217443 report a method of forming a zinc oxide thin film by electrolysis from an aqueous solution containing zinc ions and nitrate ions.

[0005]

However, as described above, the optical confinement layer already disclosed is generally formed by a vacuum deposition method using a resistance heating or an electron beam, a sputtering method, an ion plating method, a CVD method, or the like. Have been. For this reason, there are problems such as a high labor cost for producing a target material and the like, a necessity of a vacuum process, a large depreciation cost of a vacuum device, and a low efficiency of material use. Therefore, the cost of a photovoltaic element using these technologies is extremely high, and this is a great barrier for industrial application of a solar cell.

A zinc oxide thin film formed by electrolysis from an aqueous solution containing zinc ions and acetate ions can be formed at low cost, but has the following problems.

(1) In particular, when the current density is increased or the concentration of the solution is increased, abnormal growth in the form of needles, spheres, resins or the like exceeding micron order is generated on the deposition. When the zinc oxide thin film is used as a part of a photovoltaic element, it is considered that such abnormal growth causes a shunt path of the photovoltaic element.

(2) The size of zinc oxide crystal grains tends to vary, and there is a problem in uniformity when the area is increased.

(3) Adhesion to the substrate is inferior to those formed by vacuum evaporation, sputtering, ion plating, CVD, etc. by resistance heating or electron beam.

(4) Only a thin film having a smooth film thickness is formed, and there is no particular mention of a deposited film having an uneven shape having an optical confinement effect.

(5) The method of forming a zinc oxide thin film by electrodeposition cannot be applied on aluminum which is suitably used as a reflection layer of a photovoltaic element.

The present invention provides a manufacturing method which stabilizes the formation of a zinc oxide thin film by electrodeposition and has excellent substrate adhesion. In particular, it is a zinc oxide thin film suitable for application to a light confinement layer of a photovoltaic element.

[0013]

Means for solving the above problems are to form a first zinc oxide thin film on a substrate by a sputtering method, and to include at least nitrate ions, zinc ions, and carbohydrates. Forming a second zinc oxide thin film on the first zinc oxide thin film by immersing the substrate in an aqueous solution, and applying a current between the electrode and the electrode immersed in the solution. This is a characteristic method for producing a zinc oxide thin film.

The concentrations of nitrate ion and zinc ion are respectively
Desirably in the range of 0.001 mol / l to 1.0 mol / l,
More preferably, it is in the range of 0.01 mol / l to 0.5 mol / l, and most preferably, it is in the range of 0.1 mol / l to 0.25 mol / l.

The amount of carbohydrate in the aqueous solution is from 0.001 g / l
It is desirably in the range of 300 g / l, more desirably 0.
It is preferably in the range from 005 g / l to 100 g / l, and most preferably in the range from 0.01 g / l to 60 g / l.

The detailed reason why a zinc oxide thin film having excellent uniformity can be formed is unknown, but the formation of crystal nuclei by the interaction between a carbohydrate in an aqueous solution and a zinc-containing ion such as Zn (OH) +. It is thought that this may be caused by the uniform occurrence.

Although the detailed reason why a zinc oxide thin film free from abnormal growth can be formed is unknown, it is considered that carbohydrate molecules are adsorbed on the substrate and an inhibitory action that prevents the development of abnormal growth acts. .

The detailed reason why a zinc oxide thin film having excellent adhesion can be formed is unknown, but zinc-containing ions adsorbed on the substrate diffuse on the surface of the zinc oxide thin film and crystallize at an appropriate position. It is considered that a dense film is formed in the process of being incorporated into the lattice, and as a result, a zinc oxide thin film having excellent adhesion to the substrate can be produced.

Further, the conductive substrate before being put into the aqueous solution is
By heating using a heating means, the effect of the above-mentioned carbohydrate at the time of initial film formation, which is important for forming a crystalline thin film, becomes more effective, and a high-quality zinc oxide thin film can be formed. Become like In this case, as a means for heating the conductive substrate, heating by a lamp heater, a hot water tank provided separately, or the like can be used.

The carbohydrate is glucose (glucose);
When monosaccharides such as fructose (fructose) are used, a zinc oxide thin film can be produced which is particularly excellent in the effect of improving the uniformity among the effects of the above carbohydrates. Further, the carbohydrate is maltose (maltose), saccharose
In the case of a disaccharide such as (sucrose), a zinc oxide thin film having particularly excellent effects of eliminating abnormal growth among the above carbohydrate effects can be produced. In addition, when the carbohydrate is a polysaccharide such as dextrin or starch, a zinc oxide thin film having an excellent effect of improving the adhesiveness among the effects of the carbohydrate can be produced. In addition, by combining these carbohydrates to take advantage of the above advantages, a high-quality zinc oxide thin film can be produced.

By making the electrode immersed in the aqueous solution a zinc electrode, the composition conditions such as the concentration of zinc ions in the aqueous solution and PH are kept constant. As a result, it is possible to form a thin film under the same conditions over a long period of time without having to separately supply zinc ions in order to keep the composition of the electrolyte constant, and a zinc oxide thin film with excellent uniformity Can be formed.

When the temperature of the aqueous solution is 50 ° C. or higher, and / or when the current density applied to the electrode is 10 mA / dm ² to 10 A / dm
^In the case of the range of ² , it becomes possible to efficiently produce a highly pure zinc oxide thin film.

The reaction when ZnO is deposited on the substrate surface is as follows:
It is considered that intermediates such as nitrate ion NO ³⁻ , nitrite ion No ²⁻ , ammonium ion NH ⁴⁺ , hydroxide ion OH ⁻ , and zinc hydrate ion are involved. The temperature of the aqueous solution is 50
If the temperature is lower than ℃ or the current density applied to the electrode is out of the above range, the reaction mediated by these intermediates will not proceed sufficiently and substances other than zinc oxide such as metallic zinc will precipitate. It is thought that it becomes difficult to form a zinc oxide thin film with high purity. Further, when the current density is smaller than 10 mA / dm ^2, there is a problem that a sufficient reaction speed cannot be obtained.

Further, by providing a metal layer of a metal having a high reflectance on the support, the reflectance as a base can be increased, and a photovoltaic element having a higher light conversion efficiency can be manufactured.

Further, by changing the temperature, concentration and current density of the aqueous solution, the particle size and orientation of the zinc oxide thin film can be changed, and the zinc oxide thin film is formed into a plurality of layers having a plurality of characteristics. With this configuration, it is possible to provide various variations in the uneven shape of the surface of the zinc oxide thin film, and to create a film having better adhesion.

In particular, ion concentration and current density are parameters closely related to the crystal growth of a zinc oxide thin film. When the current density is small instead of the metal ion concentration, the crystal grains become large because the generation of nuclei is small, and the crystal grains become small as the current density increases. If the concentration of metal ions is low and the current density is higher than a certain level, concentration polarization occurs due to precipitation, and concentration polarization promotes nucleation and inhibits growth, so that crystal grains become fine. As described above, the crystal state of the zinc oxide thin film can be changed by the parameters of these aqueous solutions.

In application to a photovoltaic element, a first crystal having a fine crystal and a smooth surface and having excellent adhesion to an underlayer is used.
And a second zinc oxide layer having a large and uneven surface with large crystal grains and a large light confinement effect. Such a zinc oxide layer can achieve both adhesion to the substrate and effective light confinement.

Preferably, the particle size of the first zinc oxide layer is 1/10 or less of the particle size of the second zinc oxide layer.
Preferably, the orientation of the first zinc oxide layer is the c-axis, and the orientation of the second zinc oxide layer is mainly the <101> axis.

The crystal orientation can be controlled by the zinc nitrate concentration. When the zinc nitrate concentration is 0.1 mol / l, the c-axis is inclined and the hexagonal pieces are oriented in a rising shape,
When the content is 0.025 mol / l or less, the film is formed with the c-axis perpendicular to the substrate.

Before the formation of the zinc oxide thin film by electrodeposition, the thickness of the zinc oxide thin film formed by the sputtering method is desirably as thin as possible to the extent that electrodeposition is possible.
This makes it possible to make use of the economic effect of film formation by electrodeposition.

[0031]

DETAILED DESCRIPTION OF THE INVENTION] An example of a zinc oxide thin film forming apparatus of the present invention to the manufacturing method Figure 1 zinc oxide thin film.

Reference numeral 101 denotes a corrosion-resistant container, which holds an aqueous solution 102 containing nitrate ions, zinc ions, and carbohydrates. In order to obtain a desired zinc oxide film, the concentration of nitrate ion and zinc ion are each 0.001 mol / l to 1.0 mol.
/ l, more preferably 0.01mo
It is desirably in the range of l / l to 0.5 mol / l, and optimally in the range of 0.1 mol / l to 0.25 mol / l.

The source of supply of nitrate ions and zinc ions is not particularly limited, and zinc nitrate, which is a supply source of both ions, or a water-soluble nitrate such as ammonium nitrate, which is a supply source of nitrate ions, may be used. And a mixture of zinc salts such as zinc sulfate, which is a source of zinc ions.

The type of carbohydrate is not particularly limited, but includes glucose (glucose), fructose
Monosaccharides such as (fructose), disaccharides such as maltose (maltose) and saccharose (sucrose), polysaccharides such as dextrin and starch, and mixtures thereof can be used.

The amount of carbohydrate in the aqueous solution is preferably in the range of 0.001 g / l to 300 g / l in order to obtain a zinc oxide thin film having no abnormal growth and excellent uniformity and adhesion. It is desirably in the range of 0.005 g / l to 100 g / l, and optimally in the range of 0.01 g / l to 60 g / l.

Reference numeral 103 denotes a conductive base, which is a cathode. Reference numeral 104 denotes a counter electrode, which can be made of zinc, which is a metal to be deposited in a liquid phase, platinum, carbon, or the like. The counter electrode 104 is an anode. The base 103 serving as a cathode and the counter electrode 104 serving as an anode are connected to a power supply 105 via a load resistor 106 so that a substantially constant current flows. In order to obtain a desired zinc oxide film, the current density is desirably in the range of 10 mA / dm to 10 A / dm.

Further, in order to reduce the layer formation unevenness by stirring the solution and increase the layer formation speed for efficiency, the suction bar 108 having a plurality of solution suction ports, and similarly, the injection bar 108 having a plurality of solution injection ports. Bar 107, solution circulation pump 111, solution suction bar
Inhalation solution pipe 10 connecting 108 and solution circulation pump 111
9. A solution circulation system including a solution ejection bar 107 and an injection solution pipe 110 connecting the solution circulation pump 111 is used.
In a small-scale apparatus, a magnetic stirrer can be used instead of such a solution circulation system.

Further, using a heater 112 and a thermocouple 113,
The temperature of the aqueous solution is controlled while monitoring the temperature. In order to obtain a desired zinc oxide film, the temperature of the aqueous solution is desirably 50 ° C. or higher.

After the deposition of the first zinc oxide film, the conditions may be changed and a second zinc oxide film may be subsequently deposited.

Before forming the zinc oxide thin film, the substrate may be immersed in a hot water tank 114 in order to heat the substrate 103. The hot water tank 114 contains hot water whose temperature has been adjusted using a heater 115 and a thermocouple 116 so that the base 103 can be heated.

Continuous Forming Apparatus The apparatus shown in FIG. 2 is an apparatus capable of continuously forming a zinc oxide layer from the aqueous solution on the surface of a long sheet-shaped conductive substrate 201 having flexibility (flexibility). is there.

On the back surface of the conductive substrate 201, an insulating tape (not shown) for preventing deposition of a zinc oxide film is stuck. 20
2 is a delivery roll that winds the conductive substrate 201 in a roll shape, 203 is a winding roll that winds the conductive substrate,
The conductive substrate is wound up by a take-up roll 203 via many transport rolls 204. The diameter of each roll must be determined according to the material of the conductive substrate in order to prevent plastic deformation of the substrate.

Reference numeral 205 denotes a hot water tank for heating the conductive substrate, which is connected to a circulation system 206 having a filter for removing dust therein, and a heater 207 inside the hot water tank.

Reference numeral 208 denotes a liquid phase deposition tank for forming a zinc oxide layer, which is also a circulation system having a built-in filter for removing dust.
209 is connected, a zinc electrode 210 and a heater 211 are provided inside the liquid deposition tank, and a constant current power supply 212 is connected outside. The circulation device 209 has a system for monitoring the solution concentration and adding a solution as needed.

A washing tank 213 is connected to a circulation system 214 having a filter for removing dust. 215 is a drying chamber for performing hot air drying.

According to this apparatus, a zinc oxide thin film can be formed at low cost.

(Substrate) The substrate used in the present invention has a base of a magnetic or non-magnetic metal support. Among them, stainless steel plates, steel plates, copper plates, brass plates, aluminum plates, and the like are preferable because they are relatively inexpensive.

These metal plates may be cut into a predetermined shape, or may be used in a long sheet-like shape depending on the plate thickness. In this case, since it can be wound in a coil shape, it is suitable for continuous production, and storage and transportation become easy. Further, depending on the use, a crystal substrate such as silicon, a glass or ceramic plate can be used. The surface of the support may be polished, but may be used as it is when the finish is good such as a stainless steel plate subjected to a bright annealing treatment.

[0049] The cross section view of a photovoltaic element to which the zinc oxide thin film formed by the method of application the present invention to a photovoltaic element shown in FIG. In the figure, 301-1 is a support, 301-2 is a metal layer, 301-3 is a transparent conductive layer, 302 is a zinc oxide layer formed by the method of the present invention, 303 is a semiconductor layer, 304 is a transparent conductive layer, 305 Is a collecting electrode. The above support 301-
1. The metal layer 301-2 and the transparent conductive film layer 301-3 form the conductive substrate 301 according to the present invention.

The zinc oxide layer 302 may be formed by laminating a plurality of layers having different grain sizes and different orientations of crystal axes.

The sunlight enters from the photovoltaic element 304 side. Short-wavelength light shorter than 500 nm is transmitted to the next semiconductor layer 303.
It is almost absorbed by. On the other hand, light having a wavelength longer than about 700 nm, which is a wavelength longer than the band absorption edge, partially passes through the semiconductor layer 303, and the zinc oxide film 3 serving as a transmission layer
02, the light is reflected by the metal layer 301-2 or the support 301-1, again passes through the zinc oxide film 302, which is a transmission layer, and is partially or largely absorbed by the semiconductor layer 303.

At this time, the support 301-1 and / or the metal layer
301-2 and / or the zinc oxide layer 302 which is a transparent layer and / or the semiconductor layer 303 is formed with irregularities and is sufficient to bend the path of light, and the semiconductor layer 303 is transmitted by tilting the optical path. It is expected that the optical path length will increase and the absorption will increase. The increase in absorption due to the extension of the optical path length is so small that it hardly causes a problem in a layer almost transparent to light, but the region where absorption is present to some extent, that is, the wavelength of light is a wavelength near the absorption edge of the substance. Becomes exponential. Since the zinc oxide layer 302, which is a transparent layer, is transparent to visible light to near-infrared light, light of 600 nm to 1200 nm is absorbed in the semiconductor layer 303.

Although the metal layer 301-2 is not essential, it may be used for a substrate having low reflectivity as it is, such as stainless steel or steel plate, or a support made of a material having low conductivity, such as glass or ceramics. It is preferable to provide a metal layer 301-2 having high reflectivity such as silver, copper, gold, or aluminum thereon. Also, the metal layer 301
When aluminum is used for -2, an extremely thin transparent conductive film layer 301-3 is used on the metal layer 301-2 in order to prevent aluminum from dissolving in the above aqueous solution.

(Semiconductor layer) The material of the semiconductor layer is p
Examples include an n-junction, a pin junction, a Schottky junction, and a heterojunction. As the semiconductor material, hydrogenated amorphous silicon, hydrogenated amorphous silicon germanium, hydrogenated amorphous silicon carbide, microcrystalline silicon, or polycrystalline silicon is used. Crystalline silicon or the like can be used.

In particular, amorphous or microcrystalline Si, C, Ge, and Si are suitable for continuous formation on a long substrate.
Or these alloys. At the same time, hydrogen and / or halogen atoms are contained. Its preferred content is 0.1.
About 40 atomic%. Further, it may contain oxygen, nitrogen and the like. The concentration of these impurities is preferably 5 × 10 ¹⁹ cm ⁻³ or less. To further form a p-type semiconductor, a group III element, n
To form a type semiconductor, a V element is contained.

In the case of a stacked cell, the pin near the light incident side
The junction i-type semiconductor layer has a wide band gap and
It is preferable that the band gap becomes narrower as the bonding is performed. Further, it is preferable that the band gap has a minimum value closer to the p layer than the center of the film thickness in the i layer.

As the doped layer on the light incident side, a crystalline semiconductor with little light absorption or a semiconductor with a wide band gap is suitable.

(Method of Manufacturing Semiconductor Layer) In order to form the above-described semiconductor layer, a microwave (MW) plasma CVD method or a radio frequency (RF) plasma CVD method is suitable. It is formed by the following procedure. [Here, if necessary, refer to the drawing of the film forming apparatus. The drawing is not particularly required if it is a known device. ]

(1) The inside of the deposition chamber (vacuum chamber) which can be reduced in pressure is reduced to a predetermined initial pressure. (2) A material gas such as a source gas or a dilution gas is introduced into the deposition chamber, and the deposition chamber is set to a predetermined deposition pressure while being evacuated by a vacuum pump. (3) The substrate is set to a predetermined temperature by a heater. (4) In MW-CVD, a microwave oscillated by a microwave power supply is guided by a waveguide and introduced into the deposition chamber via a dielectric window (alumina ceramics or the like). However, when the frequency of the microwave is as low as 100 MHz to 1 GHz, it can be applied from a metal electrode. In RF-CVD,
A high frequency from a high frequency power supply is introduced into the deposition chamber via a discharge electrode. (5) The plasma of the source gas is generated and decomposed to form a deposited film on the substrate placed in the deposition chamber.

In the case of the MW-CVD method, the substrate temperature in the deposition chamber is 10
0 ~ 450 ℃, internal pressure 0.5 ~ 30mTorr, microwave power
0.01-1W / cm3, microwave frequency is 0.1-10GH
z, the deposition rate is preferably in the range of 0.05 to 20 nm / sec.

In the case of the RF-CVD method, the frequency of the RF high frequency is 0.
1 to 100 MHz, substrate temperature in the deposition chamber is 100 to 350 ° C., internal pressure is 0.1 to 10 Torr, RF power is 0.001 to 0.5 W / c.
m ³ and the deposition rate are preferably 0.01 to ³ nm / sec.

Group IV and IV suitable for the photovoltaic device of the present invention
The source gas suitable for depositing the group III alloy amorphous semiconductor layer is Si.
A gasizable compound containing a silicon atom such as H4, Si2H6 or the like, or a gasizable compound containing a germanium atom such as GeH4 is mainly used.

Further, a gasizable compound containing carbon, nitrogen, oxygen and the like may be used in combination.

B2H6, BF3 or the like is used as a dopant gas for forming a p-type layer.

As a dopant gas for forming an n-type layer, PH3, PF3 or the like is used.

In particular, a microcrystalline or polycrystalline semiconductor or SiC
In the case of depositing a layer having a small light absorption or a wide band gap, it is preferable to increase the dilution ratio of the raw material gas with the hydrogen gas and to introduce a relatively high microwave power or RF power.

(Transparent Electrode) The transparent electrode 107 can also function as an anti-reflection film by appropriately setting its film thickness.

The transparent electrode 107 is formed of a material such as ITO, ZnO, and InO ₃ by using a method such as vapor deposition, CVD, spray, spin-on, and immersion. These compounds may contain a substance that changes electric conductivity.

(Current Collecting Electrode) The current collecting electrode 108 is provided to improve current collecting efficiency. Examples of the manufacturing method include a method of forming a metal of an electrode pattern by sputtering using a mask, a method of printing a conductive paste or a solder paste, and a method of fixing a metal wire with a conductive paste.

Incidentally, protective layers may be formed on both surfaces of the photovoltaic element 100 as required. At the same time, a reinforcing material such as a steel plate may be used in combination.

[0071]

EXAMPLE An example of preparation of a zinc oxide film The apparatus shown in FIG. 1 omitting the solution circulation system was used. The negative electrode 103 is a stainless steel 430BA having a thickness of 0.12 mm, which is formed by sputtering 2,000 ° of copper, and the back surface is covered with a tape. The positive electrode 104 is a 1-mm-thick 4-N zinc. It was used.

The solution was an aqueous solution of zinc nitrate, 100 ml
Was added with sucrose at a rate of 2 g. The zinc nitrate concentration was changed from 0.1 M / l to 0.0025 M / l. The liquid temperature was changed from room temperature to 85 ° C., and the applied current was 0.3 to 1
It was changed in the range of 00 mA / cm2 (0.03 to 10 A / dm2). Instead of omitting the solution circulation system, the solution was constantly stirred with a magnetic stirrer.

(Example 1-1) The applied current density was about 1 mA.
/ Cm2 and the concentration of zinc nitrate in the solution was 0.1 M /
1, 0.025 M / l, 0.01 M / l, 0.0025
The film was formed by changing the liquid temperature from room temperature to about 85 ° C. with respect to M / l. The deposited film has a liquid temperature of 60 ° C.
In the above case, the powder was identified to be hexagonal zinc oxide by an X-ray diffractometer, and its crystal grain size was observed by SEM. The results were as shown in FIG. When the liquid temperature was lower than 60 ° C., deposition of metallic zinc also occurred, and zinc oxide of a certain size was not observed. Furthermore, when the liquid temperature is 60 ° C
In the above case, when the orientation of the crystal grains is evaluated from X-ray diffraction, when the zinc nitrate concentration is 0.1 M / l, the c-axis is tilted and the hexagonal pieces are oriented in the form of rising, and 0.025 M / l l
In the following cases, it was found that the film was formed with the c-axis perpendicular to the substrate.

Example 1-2 Next, the temperature was kept constant at 65 ° C., and the concentration of zinc nitrate in the solution was adjusted to 0.1 M / l, 0.02
Film formation was performed by changing the applied current density from about 0.5 mA / cm2 to about 100 mA / cm2 with respect to 5 M / l and 0.01 M / l. FIG. 5 plots the deposition rate as a function of the applied current density. At any concentration,
Up to an applied current density of about 5 mA / cm 2, the deposition rate increases almost linearly. 5 mA / c applied current density
If it exceeds m2, the deposition rate decreases, and abnormal growth is observed according to SEM image observation. Precipitation of metal zinc instead of zinc oxide was observed, but this can be prevented by stirring. At least 1 to 100 mA / cm by stirring
In the range of 2, good deposition was possible. That is, it is understood that the supply of the growth agent from the solution system controls the reaction. Also here, regardless of the film forming rate, when the zinc nitrate concentration of the solution is 0.1 M / l, the c-axis is inclined and oriented.
At 025 M / l and 0.01 M / l, it was found that the crystal grains grew with c-axis orientation.

FIG. 6 shows an X-ray diffraction pattern from a sample in which the c-axis is inclined and oriented at 0.1 M / l.
FIG. 7 shows an X-ray diffraction pattern from a sample in which crystal grains are grown with a c-axis orientation at 25 M / l. The effect of the underlying substrate has been corrected. The difference between the SEM images is also clear. The sample showing the X-ray diffraction pattern in FIG. 6 shows the morphology in which all hexagonal crystal fragments have risen, while the sample showing the X-ray diffraction pattern in FIG. Only the upper surface of the hexagonal crystal piece is observed in the plane. The change in temperature only changes the particle size, and does not make a difference in the appearance of the SEM image.

In order to determine whether monovalent ions or divalent ions are present in the deposition reaction, FIG. The broken line in the middle is enough within the range of the error,
It was found that monovalent ions were involved, ie, monovalent collection. Thus, perhaps the key factor in growing zinc oxide from aqueous solution is Zn (NO3)
+ Is estimated.

That is, from the above-described embodiment, zinc oxide is deposited favorably at a temperature higher than about 50 ° C., the crystal grain size depends on the solution concentration and the liquid temperature, and the deposition rate depends on the applied current density. Dependence, the orientation depends on the solution concentration, and the factor controlling them is Zn (NO3).
It seems that it seems to be +. This means that by appropriately selecting the solution concentration and the solution temperature, a zinc oxide film having predetermined crystal grains is formed from an aqueous solution containing zinc nitrate and saccharose with a desired orientation (whether the c-axis is inclined or vertical). Indicates that you can do it.

(Example 2-1) On a 5 × 5 cm stainless (430BA) substrate, 300 zinc oxide was added from an aqueous solution.
0 Å was deposited. That is, a 99.99% zinc plate was used as a positive electrode, and the stainless steel substrate was used as a negative electrode.
0.1M with sucrose 20g / l added
Then, a current of 20 mA was passed between the electrodes having a gap of 3.5 cm using a galvanostat while the aqueous solution was immersed in an aqueous zinc nitrate solution. After 10 minutes, a milky white zinc oxide film was deposited by scattering. At this time, the hydrogen ion concentration (pH) of the aqueous solution was 5.4. This is drained with compressed air to obtain a film a.

(Example 2-2) The same procedure as in Example 1-1 was repeated except that the aqueous solution of Example 1-1 was diluted 40 times with pure water and the temperature was maintained at 85 ° C. A zinc oxide layer was obtained. The pH was 6.4, and a film having a transparent interference color was deposited. This is referred to as a film b.

REFERENCE EXAMPLE 2-3 Zinc oxide was deposited on the same stainless steel substrate as in Example 1-1 by DC magnetron sputtering to have the same thickness. That is, using a zinc oxide target, sputtering was performed for 5 minutes at a power of 100 W at 10 mTorr while flowing Ar at 2 sccm to obtain a 3000 Å zinc oxide layer. Example 1
A transparent film exhibiting an interference color like -2. This is referred to as a film c.

REFERENCE EXAMPLE 2-4 Zinc oxide was deposited on the same stainless steel substrate in the same manner as in Reference Example 2-3 to a thickness of 5 times by DC magnetron sputtering. In order to increase the thickness, the deposition time was increased five times. The resulting film was 1.5 microns. The appearance of the film was a transparent film exhibiting interference colors. This is referred to as a film d.

(Example 2-5) A zinc oxide layer having a transparent interference color and having a thickness of about 1000 angstroms was deposited in the same manner as in Example 1-2 except that the deposition time was changed to 3 minutes. Thereafter, a stainless steel substrate on which a zinc oxide layer of about 1000 Å was deposited was used as an electrode, and the deposition time was about 7 minutes, except that the deposition time was about 7 minutes.
A 0 Å layer of zinc oxide was deposited. This composite film is referred to as a film e.

The spectral total reflectance of the film a showed that the interference pattern was blurred in the near-infrared region even though the film thickness was thin, indicating that the scattering characteristics were extremely good.

When the films a to e were observed by SEM,
The film a and the film e have a flat polycrystalline structure with a diameter of about 1.2 μm, the film b has a scale-like polycrystalline structure with a diameter of about 0.1 μm, and the films c and d are Although the resolution was insufficient and the shape was not enough to evaluate the orientation, it was confirmed that it was a granular aggregate structure with a particle size of several hundred angstroms.

When the films a to c were evaluated by X-ray diffraction, the results of the film a were as shown in FIG. 6, and those whose c-axis was tilted from vertical in the hexagonal diffraction of zinc oxide were mainly used. It turns out that it occupies a part. At this time, X-ray diffraction <00
The intensity of 2> was 30% of the intensity of <101>. Membrane b
And c mainly have a diffraction peak of <002>, and it was found that the example of the diffraction pattern of the film b is oriented along the c-axis as shown in FIG.

Further, a-Si (n), a-SiGe (i) and mc-Si are sequentially formed on the films a, b, c, d and e.
(P) is deposited by microwave CVD and then ITO is
Evaporation was performed to 0 angstrom, and a grit was formed with silver to obtain an upper extraction electrode. When the solar cell fabricated in this way was evaluated under a solar simulator,
The short-circuit current density Jsc of the film a is 10.2 mA, the short-circuit current density Jsc of the film b is 9.5 mA, and the short-circuit current density Js of the film c is
c is 8.6 mA, and the short-circuit current density Jsc of the film d is 9.3 m.
A and the short-circuit current density Jsc of the film e were 10.0 mA, which was a great difference.

Further, the films a, b, c, d and e were bent together with the substrate, and the peelability was examined. The film a started peeling at the bent portion and almost peeled off at the time of bending back. On the other hand, when the films b, c, d, and e were bent at an angle of 180 degrees, no peeling was observed, and it was confirmed that the adhesiveness was high.

Example of Application to Photovoltaic Element (Example 3) A solar cell having three pin junctions in a semiconductor layer was prepared. Specifically, the support (SUS430 15 × 15cm2 thickness 0.
2mm) / Metal layer Ag / Transparent conductive layer ZnO / Semiconductor layer / Transparent conductive layer ITO
/ A solar cell composed of the current collecting electrode Cr was created.

First, a metal layer Ag was formed on a support by a normal sputtering method to form a conductive substrate. Next, an aqueous solution containing nitrate ions and zinc ions containing glucose as shown in the conditions of Table 1 was placed on a conductive substrate pre-heated by immersing in hot water at 85 ° C. in a hot water bath using the apparatus of FIG. A transparent conductive layer ZnO was formed with a thickness of 2.0 μm using the above.

The semiconductor layer is a first n-type doped layer a-Si: H: P /
1 i-layer a-SiGe: H / first p-type doped layer μc-Si: H: B / second n-type doped layer a-Si: H: P / second i-layer a-Si
Ge: H / second p-type doped layer μc-Si: H: B / third n-type doped layer a-Si: H: P / third i-layer aS
A structure such as i: H / third p-type doped layer μc-Si: H: B was formed by a plasma CVD method. The transparent conductive layer ITO is formed by a normal sputtering method,
Was prepared by a normal vacuum deposition method. A total of 100 transparent conductive layer ITOs were formed in a circular shape having an area of 1 cm2 on the semiconductor layer by masking to form subcells, and current collecting electrodes were formed on each subcell.

Comparative Example 1 A solar cell of FIG. 3 having three pin junctions in the semiconductor layer was produced in the same manner as in Example 3, except that the transparent conductive layer ZnO was produced under the conditions shown in Table 2. As in Example 3, the transparent conductive layer ITO was formed into a circular shape having an area of 1 cm2 on the semiconductor layer by masking as shown in FIG.
Zero cells were formed as subcells, and a current collecting electrode was formed on each subcell.

The solar cell characteristics of the solar cell of Example 3 and the solar cell of Comparative Example 1 were measured using a solar simulator (AM 1.5, 100 mW /
cm2, surface temperature 25 ° C). At the same time, the shunt resistance (Rsh) was measured to evaluate the degree of leakage current. With respect to the shunt resistance, a criterion for withstanding practical use was established, and a value exceeding the criterion was regarded as a non-defective product.
In addition, the solar cell characteristics of the sub-cells that were determined to be non-defective were examined, the degree of variation was examined from the standard deviation of light conversion efficiency, and the zinc oxide thin film was evaluated as uniform. The adhesion of the solar cells subjected to the HH test (high-temperature high-humidity test) was evaluated by using a grid tape method. The HH test was performed by placing each solar cell in an environmental test box and maintaining the temperature at 85 ° C. and a humidity of 85% for 100 hours. The cross-cut tape method uses a cutter knife to cut the solar cell taken out of the environmental test box with a cutter knife at intervals of 1 mm in a cross-cut pattern, attaches an adhesive tape on the cross-cut, and removes it. It was performed by a method of visually observing the adhered state of the film.

As a result, the solar cell of Example 3 was superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of the non-defective subcells, and the adhesion test by the cross-cut tape method. The standard deviation of the light conversion efficiency of the non-defective subcell was as small as 1/5 of Comparative Example 1.

(Example 4) A solar cell was produced in the same manner as in Example 3 except that glucose in Example 3 was changed to saccharose. Table 3 shows the conditions.

As a result, the solar cell of Example 4 was superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of non-defective subcells, and the adhesion test by the cross-cut tape method. The non-defective rate was 100%.

(Example 5) A solar cell was produced in the same manner as in Example 3 except that glucose in Example 3 was changed to dextrin. Table 4 shows the conditions.

As a result, the solar cell of Example 5 was superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of non-defective subcells, and the adhesion test by the cross-cut tape method. The adhesion test by the cross-cut tape method was excellent.

(Example 6) A solar cell was produced in the same manner as in Example 3, except that glucose in Example 3 was changed to a mixture of glucose, saccharose, and dextrin. Table 5 shows the conditions.

As a result, the solar cell of Example 6 was superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of non-defective subcells, and the adhesion test by the grid tape method.

Example 7 A photovoltaic device was prepared in the same manner as in Example 6, except that the nitrate ion concentration in Example 6 was doubled. Table 6 shows the conditions.

As a result, the solar cell of Example 7 was superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of non-defective subcells, and the adhesion test by the grid tape method.

Example 8 Using the apparatus shown in FIG. 1, a sample was prepared by depositing ZnO to a thickness of 2.0 μm on NESA glass under the conditions shown in Table 7. Samples are 6 for each temperature shown in Table 7.
Type created. When the transmittance of the sample was measured with a spectrometer and the values of the transmittance at 800 nm were compared, five samples with an aqueous solution temperature of 50 ° C or higher showed almost the same transmittance, but the sample with an aqueous solution temperature of 40 ° C did not. It showed a 10% lower transmittance for samples above 50 ° C.

Subsequently, a photovoltaic element was produced in the same manner as in Example 3.

The solar cell characteristics of the solar cell of Example 8 were measured using a solar simulator (AM 1.5, 100 mW / cm 2, surface temperature 25 ° C.).
It measured using. As a result, the temperature of the aqueous solution
Five solar cells showed almost the same light conversion efficiency,
A solar cell with an aqueous solution temperature of 40 ° C showed 10% lower light conversion efficiency than a solar cell with a temperature of 50 ° C or higher.

From the above, it has been found that an excellent photovoltaic element can be obtained when the temperature of the aqueous solution containing nitrate ions, zinc ions and carbohydrates is 50 ° C. or higher.

Example 9 Using the apparatus shown in FIG. 1, a sample was prepared by depositing ZnO to a thickness of 2 μm on NESA glass under the conditions shown in Table 8. Six types of samples were prepared for each current density shown in Table 8. When the transmittance of the sample was measured with a spectrometer and the values of the transmittance at 800 nm were compared,
The four samples with current densities of 10 mA / dm2 to 10 A / dm2 showed almost the same transmittance, but the current densities were 5 mA / dm2 and 20 A / dm2.
The sample No. 4 showed 5% lower transmittance than the four samples from 10 mA / dm2 to 10 A / dm2.

Subsequently, a photovoltaic element was produced in the same manner as in Example 3.

The solar cell characteristics of the solar cell of Example 9 were measured using a solar simulator (AM 1.5, 100 mW / cm 2, surface temperature 25 ° C.).
It measured using. As a result, the current density increases from 10 mA / dm2
The four solar cells with 10A / dm2 showed almost the same light conversion efficiency, but the solar cells with current densities of 5mA / dm2 and 20A / dm2 changed from 10mA / dm2 to 10A / dm2. 5% lower light conversion efficiency.

As described above, the applied current density is 10 mA.
It has been found that an excellent photovoltaic element can be formed in the range from / dm2 to 10A / dm2.

Example 10 A first zinc oxide layer was formed in which the zinc ion concentration in Example 6 was halved and the applied current density was doubled (Table 9). Subsequently, the zinc nitrate concentration was halved. ,
A second zinc oxide layer was formed with an applied current density of 1/10
(Table 10). Thereafter, a photovoltaic device was produced in the same manner as in Example 3.

As a result, the solar cell of Example 10 was compared with Comparative Example 1
Compared with the solar cell of No. 1, the non-defective product ratio, the standard deviation of the light conversion efficiency of the non-defective sub cell, and the adhesion test by the grid tape method were also excellent.

Example 11 As an example of another embodiment, a solar cell having the structure shown in FIG. 3 was prepared using a long sheet. A semiconductor layer having three pin junctions as in Example 3 was used. The film was formed by a roll-to-roll system with high productivity.

First, a metal layer made of aluminum 0.1 μm and a transparent conductive layer made of zinc oxide 0.1 μm were formed on a support made of SUS430BA (thickness 0.15 mm) by a sputtering method using a roll-to-roll method. Then, a conductive substrate 401 was formed, and then a zinc oxide layer was formed electrochemically by the apparatus shown in FIG. Table 11 shows the conditions.

Thereafter, the third embodiment is performed by a roll-to-roll apparatus.
A solar cell similar to the above was created.

As a result, all of the solar cells of Example 9 were superior to the solar cell of Comparative Example 1 in terms of the yield rate, the standard deviation of the light conversion efficiency of non-defective subcells, and the adhesion test by the grid tape method. In particular, the adhesion test by the cross-cut tape method was excellent.

(Example 12-1) About 5 cm square and 0.1 mm thick.
A first zinc oxide layer was formed under the conditions shown in Table 12, and a second zinc oxide layer was formed under the conditions shown in Table 13, using 12 mm stainless steel 430BA as a base. In the SEM image, the first zinc oxide layer was composed of crystal grains of about 0.05 μm, and was c-axis oriented by X-ray diffraction. In the second zinc oxide layer, crystal grains of about 0.3 μm were oriented in the <101> axis.

Thereafter, a semiconductor layer is formed by CVD.
N-type amorphous silicon (a-Si)
を, 2000 of non-doped amorphous silicon (a-Si)
Å, p-type microcrystalline silicon (mc-Si) was stacked in the order of 140 積 層. Further, ITO was deposited at 650 ° by heating in an oxygen atmosphere to form a transparent conductive film as an upper electrode having an antireflection effect. A silver grid was deposited thereon by heating evaporation to form an upper extraction electrode.

The device was measured under simulated sunlight, and the short-circuit current density Jsc was 11.0 mA.

Example 12-2 A photovoltaic device was manufactured in the same manner as in Example 12-1, except that the conditions for forming the first and second zinc oxide layers were as shown in Tables 14 and 15, respectively. It was created.

The SEM image of the first zinc oxide layer is approximately 0.
SEM image of a second zinc oxide layer composed of a hexagonal polycrystal having a second grain size and a second grain size in which crystal grains of 05 microns are oriented along the c-axis by X-ray diffraction. In this case, crystal grains of about 1.3 μm were oriented with the c-axis tilted.

When the device was measured under simulated sunlight, the short-circuit current density Jsc was 11.5 mA.

(Comparative Example 2) A photovoltaic element was produced under the same conditions as in Example 1 except that no zinc oxide layer was formed. When this device was measured under simulated sunlight, the short-circuit current density Jsc was 7.3 mA. Therefore, it was found that the device of the present invention had excellent characteristics.

(Example 13) Approximately 5 cm square with a thickness of 0.12
Millimeter stainless steel 430BA was used as a substrate, this was washed with an alkali, and a surface was sputtered with copper as a metal layer having near-infrared and good reflection characteristics at 2000 °, and then a zinc oxide layer was formed under the same conditions as in Example 12-2. Then, a photovoltaic element was created.

When this device was measured under simulated sunlight, the short-circuit current density Jsc was 13.9 mA, showing excellent characteristics.

(Comparative Example 3) A photovoltaic element was formed under the same conditions as in Example 14 except that no zinc oxide layer was formed. When this device was measured under simulated sunlight, the short-circuit current density Jsc was 8.3 mA.

Therefore, it was found that the device of the present invention had excellent characteristics.

Example 14 Two zinc oxide layers of the present invention were formed using the continuous forming apparatus shown in FIG.

First, a support roll 80 rust-proofed with oil
In No. 3, oil is degreased in a degreasing bath 806. The degreasing bath 805 contains 60 ml of sulfuric acid and 37 ml of hydrochloric acid (37
% Aqueous hydrogen chloride (the same applies hereinafter). The temperature is room temperature.

Thereafter, the sheet is conveyed to a washing tank 810 via a conveying roller 807. Wash shower 808 and 811
Washing is performed sufficiently. Preferably, the amount of water is at least 2 liters per minute.

Next, the support roll is transported by the transport roller 812.
Is transferred to the acidic etching bath 815. Here, the support 803 is etched with hydrofluoric acid and nitric acid.
The acidic etching bath 814 used is a hydrofluoric acid (4
6% hydrofluoric acid, the same applies hereinafter) 3, and acetic acid 1. The temperature is room temperature. This etching has an effect that a metal layer to be formed later adheres to the support.
In addition, the unevenness due to the etching plays an effective role in forming the unevenness of the zinc oxide thin film formed later. Thereby, a photovoltaic element having a more effective light confinement effect can be obtained.

Further, it is transported to a washing bath 819 similar to the washing bath after the degreasing bath. Since the metal layer forming bath in the next step is alkaline, it is possible to use a weak alkaline shower.

The support roll 803 is
After the steps 1 and 822, a metal layer is formed in a metal layer forming bath 826. The metal forming bath 825 is composed of 80 g of copper pyrophosphate, 300 g of potassium pyrophosphate, 6 ml of aqueous ammonia (specific gravity 0.88), and 10 g of potassium nitrate in one liter of water. The liquid temperature is controlled at 50C to 60C. pH is 8.
It should be in the range of 2-8.8. A copper plate is used for the anode 824. In this apparatus, since the support roll 803 is set to the ground potential, the layer formation is controlled by reading the current in the anode copper plate. In this example, the current density was set to 3 A / dm2.
The layer forming speed was 60 ° / s, and the thickness of the metal layer 802 formed in the metal forming bath was 4000 °.

Thereafter, after being washed in a washing tank 833,
The support roll 803 is transported to the first zinc oxide layer forming bath 840 via the transport rollers 835 and 836, and the first zinc oxide layer 103 is formed. The transparent conductive layer forming bath 839 contains 1 g of zinc nitrate hexahydrate and 20 g of saccharose in 1 liter of water, and is maintained at a temperature of 85 ° C. The pH is kept between 5.9 and 6.4. Counter electrode 8
38 is made of zinc whose surface is buffed. The current density applied to the zinc counter electrode was 2 A / dm2. Also,
The layer formation rate was 100 ° / s, and the first zinc oxide layer 1
03 had a thickness of 1 μm.

Then, after being washed with water in a washing tank 847,
The support roll 803 is transported to the second zinc oxide layer forming bath 854 via the transport rollers 849 and 850, and the second zinc oxide layer 104 is formed. The second zinc oxide layer forming bath 839 contains zinc nitrate hexahydrate 30 in 1 liter of water.
g, 20 g of saccharose and maintained at a temperature of 75 ° C. The pH is kept between 5.2 and 5.8. For the counter electrode 852, zinc whose surface is puffed is used. The current density applied to the zinc counter electrode was 2 A / dm2. The layer formation rate was 100 ° / s, and the layer thickness of the second zinc oxide layer 104 formed in the second zinc oxide layer forming bath was 1 μm.

Further, the support roll 803 is attached to the washing tank 86.
It is sent to 1 and washed with water.

After that, the support roll 803 is sent to the drying furnace 864 via the transport roller 863. Drying furnace 86
Reference numeral 4 denotes a hot air nozzle 865 and an infrared heater 866, and the hot air simultaneously repels water. The hot air from the hot air nozzle 865 was controlled at 150 ° C, and the infrared heater 866 was controlled at 200 ° C. Finally, it is taken up by a take-up roller 802.

The process speed of the support roll is 20 c
m / min. The tension related to the support roll was 10 kg. The tension is controlled by a tension adjustment clutch (not shown) incorporated in the winding roller 802.

The metal layer forming bath 826 was agitated with air, and the first zinc oxide layer forming bath 840 and the second zinc oxide layer forming bath 854 were mechanically stirred. In each case, the pH of the bath was constantly monitored by a pH meter with a built-in temperature correction using a glass electrode, ammonia was added in the metal layer forming bath 826, and the first zinc oxide layer forming bath 840 and the second In the zinc oxide layer forming bath 854, the pH of the bath was controlled by appropriately adding zinc nitrate.

After that, a photovoltaic element was prepared by a roll-to-roll apparatus.

In this embodiment, 80 g of copper pyrophosphate, 300 g of potassium pyrophosphate, and 6 m of aqueous ammonia (specific gravity 0.88) were used as the metal forming bath 625 in one liter of water.
1, an aqueous solution consisting of 10 g of potassium nitrate was selected, but copper pyrophosphate was 60 to 110 g, and potassium pyrophosphate was 100 g.
500 g, ammonia water 1-10 ml, and potassium nitrate 5-20 g. Potassium pyrophosphate contributes to the unevenness of the copper to be formed, and when added in a large amount, the unevenness is suppressed. Excess potassium pyrophosphate causes orthophosphoric acid to be generated, resulting in a decrease in current density. When the amount of potassium nitrate and the amount of ammonia water are both small, the unevenness contributes to the increase. From the point of adhesion, a certain amount is preferable.

In this embodiment, the first zinc oxide layer formation 839 is composed of 1 g of zinc nitrate hexahydrate in 1 liter of water,
An aqueous solution containing 20 g of saccharose was selected, but 0.1 g to 80 g of zinc nitrate hexahydrate and 3 g of sucrose were used.
g to 100 g, and 50 ml of nitric acid as an upper limit, or 3 to 20 ml of acetic acid for the purpose of facilitating pH control.

In the present embodiment, the second zinc oxide layer forming bath 853 contains zinc nitrate hexahydrate 30 liters in one liter of water.
g, an aqueous solution containing 20 g of saccharose was selected, but zinc nitrate hexahydrate can be added up to 1 g to 80 g, saccharose to 3 g to 100 g, and nitric acid up to 50 ml, and the pH can be easily controlled. Acetic acid may be added in an amount of 3 to 20 ml for the purpose.

Comparative Example 4 A photovoltaic element was prepared under the same conditions as in Example 14 except that copper and zinc oxide were deposited on stainless steel by a sputtering apparatus. The device of Example 14 exhibited 1.13 times the photoelectric conversion efficiency as compared with the device of Comparative Example 4, indicating that the photovoltaic device according to the present invention was excellent. This is mainly due to the improvement of the short-circuit current, and indicates that the orientation shape in which the c-axis of the zinc oxide polycrystalline film according to the present invention is inclined works extremely effectively in confining the light of the photovoltaic device. .

Next, this device was placed in an environmental test box at 85 ° C. and 85% RH, and a 1 V reverse bias was applied thereto, and the characteristics were monitored over time. While the device of Comparative Example 4 approached the unusable shunt level in 10 minutes and became unusable in 1 hour, the device of Example 14 stayed in the usable range for 16 hours. Therefore, it was found that the device of the present invention had excellent characteristics.

(Example 15) An example in which the temperature of the solution was washed and the temperature of the solution was set to approximately 75 ° C throughout the entire process was as follows. FIG.
Was used, and the temperature of all baths was set to 75 ° C., and the temperature of all baths was set to 75 ° C. However, the etching bath was a mixture of nitric acid 3, hydrofluoric acid 2, and acetic acid 3. The metal layer forming bath was the same as in Example 14, and the first zinc oxide layer forming bath 839 was in 1 liter of water. 3 g of zinc nitrate hexahydrate,
The second zinc oxide layer forming bath 853 contains 2 ml of nitric acid, 1 ml of acetic acid and 90 g of saccharose, and 30 g of zinc nitrate hexahydrate, 2 ml of nitric acid, 1 ml of acetic acid and 90 g of saccharose in 1 liter of water. Was used. The current density was 2 A / dm2 in the metal layer forming bath,
0.4 A / dm2 was set in the first zinc oxide layer forming bath 839 and 0.6 A / dm2 in the second zinc oxide layer forming bath 853.

At this time, the formation speed of the metal layer 202 is 30 °.
/ S, a layer thickness of 2000 ° and a first zinc oxide layer 103
Layer formation speed 10 ° / s, layer thickness 2000 °, layer formation speed of the second zinc oxide layer 104 10 ° / s, layer thickness 12000
Was Å.

Thereafter, a photovoltaic element was produced in the same manner as in Example 14.

(Comparative Example 5) A photovoltaic element was prepared under the same conditions as in Example 14 except that copper and zinc oxide were deposited on stainless steel by a sputtering apparatus. The device of Example 15 is a comparative example
The photoelectric conversion efficiency was 1.17 times that of the device of No. 5.

Further, the photovoltaic device formed in this example was put into an environmental test box at 85 ° C. and 85% RH, and a reverse eye was applied to the photovoltaic device at 1 V, and the characteristics were monitored over time. It stayed in the usable range and showed excellent stability. Therefore, it was found that the device of the present invention had excellent characteristics.

In the method of this embodiment, since the temperature is constant throughout the process, each time the support roller enters each bath, it is possible to avoid the inconvenience that the condition is largely changed from the set value, and the length of the entire apparatus is reduced. Can be minimized, and the cost of the device can be reduced, and the cost of the photovoltaic element can be reduced.

[0151]

According to the method for producing a zinc oxide thin film of the present invention, since a vacuum process is not required, the production cost is greatly reduced. In addition, it is possible to produce a zinc oxide thin film having a high yield and excellent uniformity and adhesion.

Further, the photovoltaic device having the zinc oxide thin film formed by the method of the present invention can greatly reduce the production cost, increase the yield, and improve the uniformity and environmental resistance. .

[Brief description of the drawings]

FIG. 1 is an apparatus for producing zinc oxide according to the present invention.

FIG. 2 is an apparatus for continuously producing zinc oxide according to the present invention.

FIG. 3 shows an example in which the zinc oxide of the present invention is applied to a photovoltaic device.

FIG. 4 shows the temperature dependence of the particle size of zinc oxide of the present invention.

FIG. 5 shows current density dependence of deposition rate of zinc oxide of the present invention.

FIG. 6 shows the X-ray diffraction intensity of a zinc oxide layer prepared at a zinc nitrate concentration of 0.1 mol / l.

FIG. 7 shows the X-ray diffraction intensity of a zinc oxide layer prepared at a zinc nitrate concentration of 0.025 mol / l.

FIG. 8 is an apparatus for continuously producing zinc oxide of the present invention.

[Explanation of symbols]

101 Corrosion-resistant container 102 Aqueous solution 103 Conductive substrate 104 Counter electrode 105 Power supply 106 Load resistance 107 Injection bar 108 Suction bar 109 Suction solution pipe 110 Injection solution pipe 111 Solution circulation pump 112 Heater 113 Thermocouple 114 Hot water tank 115 Heater 116 Thermocouple 201 conductive substrate 201 delivery roll 203 take-up roll 204 transport roll 205 hot water tank 206 circulation system 207 heater 208 liquid phase deposition tank 209 circulation system 210 zinc electrode 211 heater 211 constant current power supply 213 cleaning tank 214 circulation system 215 drying chamber 301 conductive Base 301-1 support 301-2 metal layer 301-3 transparent conductive layer 302 zinc oxide layer 303 semiconductor layer 304 transparent conductive layer 305 current collecting electrode 801 feed roller 802 feed Take the roller 803 support roll 804,807,809,812,813,816,8
18, 821, 822, 823, 829, 830, 83
2,835,836,837,843,844,84
6, 849, 850, 851, 857, 858, 86
0, 863 Conveying roller 805 Degreasing bath 806 Degreasing bath 808, 811, 817, 820, 831, 834, 8
45,848,859,862 Rinse shower 810,819,833,847,861 Rinse tank 814 Acid etch bath 815 Acid etch bath 824 Anode 825 Metal forming bath 826 Metal forming bath 827,841,855 Electric wire 828,842,856 Power supply 838, 852 Counter electrode 839 First zinc oxide layer forming bath 840 First zinc oxide layer forming bath 853 Second zinc oxide layer forming bath 854 Second zinc oxide layer forming bath 864 Drying furnace 865 Hot air nozzle 866 Infrared ray heater

Continued on the front page (72) Inventor Ryuji Kondo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (43)

[Claims] 1. A step of forming a first zinc oxide thin film on a substrate by a sputtering method, and immersing the substrate in an aqueous solution containing at least nitrate ions, zinc ions, and carbohydrates, and immersing the substrate in the solution. Forming a second zinc oxide thin film on the first zinc oxide thin film by applying a current between the first zinc oxide thin film and the first electrode. 2. The method for producing a zinc oxide thin film according to claim 1, wherein the carbohydrate is a monosaccharide, a disaccharide, or a polysaccharide. 3. The method according to claim 1, wherein the carbohydrate is a mixture of two or more carbohydrates. 4. The concentration of the carbohydrate in an aqueous solution is 0.001 m.
2. The method for producing a zinc oxide thin film according to claim 1, wherein the concentration is from ol / l to 1.0 mol / l. 5. The method according to claim 1, wherein the conductive substrate is a stainless steel plate, a steel plate,
2. The method for producing a zinc oxide thin film according to claim 1, wherein the method is one selected from a copper plate, a brass plate, and an aluminum plate. 6. The method according to claim 1, wherein the electrode is a zinc electrode. 7. The method for producing a zinc oxide thin film according to claim 1, wherein the temperature of the aqueous solution is 50 ° C. or higher. 8. The current density of the current is from 10 mA / dm 2 to 10 A /
2. The method for producing a zinc oxide thin film according to claim 1, wherein the thickness is dm2. 9. The method according to claim 1, wherein the base is formed by forming a metal layer on a support. 10. The method according to claim 9, wherein the metal layer is aluminum. 11. The method according to claim 9, further comprising the step of etching the support. 12. The support is made of glass, ceramics,
10. The method for producing a zinc oxide thin film according to claim 9, wherein the zinc oxide thin film is a resin. 13. The method according to claim 1, wherein the conductive substrate is a long substrate. 14. The method for producing a zinc oxide thin film according to claim 1, wherein the aqueous solution further contains an acid. 15. A step of forming a first zinc oxide thin film on a substrate by a sputtering method, immersing the substrate in an aqueous solution containing at least nitrate ions, zinc ions, and carbohydrates, and immersing the substrate in the solution. A step of forming a second zinc oxide thin film on the first zinc oxide thin film by applying a current to the first electrode and a step of forming a semiconductor layer. Manufacturing method. 16. The method for producing a photovoltaic device according to claim 15, wherein the carbohydrate is a monosaccharide, a disaccharide, or a polysaccharide. 17. The method according to claim 15, wherein the carbohydrate is a mixture of two or more carbohydrates. 18. The concentration of the carbohydrate in an aqueous solution is 0.00
16. The method for manufacturing a photovoltaic device according to claim 15, wherein the concentration is 1 mol / l to 1.0 mol / l. 19. The method according to claim 15, wherein the conductive substrate is one selected from a stainless steel plate, a steel plate, a copper plate, a brass plate, and an aluminum plate. 20. The method according to claim 15, wherein the electrode is a zinc electrode. 21. The method according to claim 15, wherein the temperature of the aqueous solution is 50 ° C. or higher. 22. The current density of the current is 10 mA / dm 2 to 10
16. The method for producing a photovoltaic device according to claim 15, wherein the ratio is A / dm2. 23. The method according to claim 15, wherein the base is formed by forming a metal layer on a support. 24. The method according to claim 23, wherein the metal layer is made of aluminum. 25. The method according to claim 23, further comprising the step of etching the support. 26. The support, wherein the support is made of glass, ceramics,
24. The method for producing a photovoltaic element according to claim 23, wherein the method is a resin. 27. The method according to claim 15, wherein the conductive substrate is a long substrate. 28. The method according to claim 15, wherein the aqueous solution further contains an acid. 29. The method according to claim 15, wherein the semiconductor layer is a non-single-crystal semiconductor. 30. A step of forming a first zinc oxide thin film on a substrate by a sputtering method, and immersing the substrate in an aqueous solution containing at least nitrate ions, zinc ions, and carbohydrates, and immersing the substrate in the solution. Forming a second zinc oxide thin film on the first zinc oxide thin film by applying a current between the first zinc oxide thin film and the first electrode. 31. The method according to claim 30, wherein the carbohydrate is a monosaccharide, a disaccharide, or a polysaccharide. 32. The method according to claim 30, wherein the carbohydrate is a mixture of two or more carbohydrates. 33. The concentration of the carbohydrate in an aqueous solution is 0.00
31. The method for manufacturing a semiconductor device substrate according to claim 30, wherein the concentration is 1 mol / l to 1.0 mol / l. 34. The method according to claim 30, wherein the conductive substrate is one selected from a stainless steel plate, a steel plate, a copper plate, a brass plate, and an aluminum plate. 35. The method according to claim 30, wherein the electrode is a zinc electrode. 36. The method according to claim 30, wherein the temperature of the aqueous solution is 50 ° C. or higher. 37. The current density of the current is 10 mA / dm 2 to 10
31. The method for manufacturing a semiconductor device substrate according to claim 30, wherein the ratio is A / dm2. 38. The method according to claim 30, wherein the base is formed by forming a metal layer on a support. 39. The method according to claim 38, wherein the metal layer is aluminum. 40. The method according to claim 38, further comprising etching the support. 41. The support comprises glass, ceramics,
39. The method for manufacturing a semiconductor element substrate according to claim 38, wherein the method is a resin. 42. The method according to claim 30, wherein the conductive substrate is a long substrate. 43. The method according to claim 30, wherein the aqueous solution further contains an acid.