JP2009010108A - Method for manufacturing photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a photoelectric conversion device whose performance is improved, using a transparent electrode which is superior in light confinement effect, and which can be formed on a substrate by a low-cost method. <P>SOLUTION: The method for manufacturing the photoelectric conversion device includes a process for forming the transparent electrode containing zinc oxide on a transparent insulating substrate and for forming a hydrogenated carbon film on the transparent electrode, and a process for laminating sequentially, at least one photoelectric conversion device and a back electrode on the hydrogenation carbon film, wherein the method is characterized in that the hydrogenation carbon film is formed by decomposing by a high-frequency wave hydrocarbon system material which is gas diluted by hydrogen gas within a range of 5-200 times. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to a method for manufacturing a photoelectric conversion device.

  In recent years, in order to achieve both cost reduction and high efficiency in a solar cell that is one of photoelectric conversion devices, a thin-film solar cell that requires less raw materials has attracted attention and has been developed vigorously. In particular, a method of forming a high-quality semiconductor layer on a low-priced substrate such as glass by using a low-temperature process of, for example, 300 ° C. or less is expected as a method capable of realizing low cost.

  A thin-film solar cell generally includes a transparent electrode, one or more semiconductor thin-film photoelectric conversion units, and a back electrode that are sequentially stacked on a light-transmitting substrate. One photoelectric conversion unit includes an i-type layer (also referred to as a photoelectric conversion layer) sandwiched between a p-type layer which is a conductive type layer and an n-type layer.

  Such a thin film solar cell can make the photoelectric conversion layer thinner than a conventional solar cell using bulk single crystal or polycrystalline silicon, but the light absorption of the entire thin film depends on the film thickness. There is a problem of being restricted. Therefore, in order to use light incident on the photoelectric conversion unit including the photoelectric conversion layer more effectively, the surface of the transparent conductive film or metal layer in contact with the photoelectric conversion unit is made uneven (textured), and light is transmitted at the interface. After scattering, the optical path length is extended by making it enter into a photoelectric conversion unit, and the device which makes the light absorption amount in a photoelectric converting layer increase is made | formed. This technology is called “optical confinement” and is an important elemental technology for practical use of a thin film solar cell having high photoelectric conversion efficiency.

Conventionally, a transparent conductive film such as tin oxide (SnO ₂ ) or indium tin oxide (ITO) has been used as a material for transparent electrodes in photoelectric conversion devices such as thin film solar cells. Recently, however, low-cost zinc oxide (ZnO) has been used to further reduce the manufacturing cost of thin-film solar cells.
(Prior Example 1)
For example, a substrate for a thin-film solar cell with a ZnO film disclosed in Patent Document 1 forms a base layer having fine surface irregularities on a light-transmitting insulating substrate such as glass, and 150 ° C. or higher and 200 ° C. or lower thereon. It is disclosed that a substrate for a thin film solar cell having irregularities suitable for a thin film solar cell can be provided by forming a ZnO film by a low pressure CVD method (also referred to as MOCVD method) under low temperature conditions. Since this low-pressure CVD method is a low-temperature process of 200 ° C. or lower compared with the high-pressure thermal CVD method, cost can be reduced. In addition, an inexpensive base such as glass or plastic film can be used. Further, since tempered glass can be used, the glass substrate of the large area solar cell can be made thin by about 2/3 and light. In addition, the low pressure CVD method is preferable for a thin film solar cell in terms of manufacturing cost because it can be formed at a film forming speed one digit or more faster than the sputtering method and the utilization efficiency of raw materials is high.

Further, as an advantage of using ZnO as a transparent electrode material, it can be cited that plasma resistance is higher than SnO ₂ and ITO. This is because the photoelectric conversion layer uses crystalline silicon such as thin-film polycrystalline silicon or microcrystalline silicon that uses a larger amount of hydrogen than the deposition conditions used when forming amorphous silicon and requires a large plasma density. It is effective for the crystalline silicon thin film solar cell used in the above.
(Prior Example 2)
For example, in the method for manufacturing a solar cell device disclosed in Patent Document 2, an example in which SnO ₂ is used as a transparent oxide electrode is given as a conventional method, and a high concentration of hydrogen is deposited when a semiconductor layer is deposited thereon. Although it is exposed to plasma, since it is a chemically extremely active substance, a reduction reaction occurs, which causes a problem of causing a decrease in open circuit voltage and a short circuit current in the solar cell device. Therefore, the surface stabilization of the transparent oxide electrode is important for improving the solar cell characteristics. As a solution, a diamond-like carbon layer is formed as a surface stabilization layer on the transparent oxide electrode, and microcrystals are formed thereon. It discloses that a p-type or n-type semiconductor layer, an amorphous intrinsic semiconductor layer, an amorphous n-type or p-type semiconductor layer, and a metal electrode are sequentially formed.

In the specification of the present application, the terms “crystalline” and “microcrystal” include those partially including amorphous.
JP-A-2005-311292 JP 2001-127315 A

  The object of the present invention is to make the surface unevenness of a transparent electrode used in a photoelectric conversion device such as a thin-film solar cell effective for light confinement, and to produce a transparent electrode that improves the performance of the photoelectric conversion device with an inexpensive manufacturing method. It is to provide and further improve the performance of the photoelectric conversion device using the same.

  First, since the method described in the example of Patent Document 1 uses a low-pressure CVD method, the surface unevenness of the transparent electrode for a thin-film solar cell effective for the light confinement effect is relatively easily obtained. However, in order to achieve higher efficiency of the thin film solar cell, in the case of trying to obtain a transparent electrode for a thin film solar cell having higher transmittance in light having a wavelength up to about 1200 nm used for photoelectric conversion Therefore, it is necessary to reduce the doping element addition amount of the ZnO film from the current level. As a result, it was necessary to increase the thickness of the ZnO film, which is a transparent electrode, in order to achieve both electrical resistance affecting thin film solar cell characteristics. Therefore, it has been found that the transmittance of the entire thin film solar cell substrate cannot be significantly improved. This is thought to be due to the fact that the ZnO film has a small particle size and a low mobility as a transparent conductive film because it is mainly formed at a low temperature. It becomes a problem.

On the other hand, Patent Document 2 discloses only SnO ₂ as a specific transparent oxide electrode. As described above, since the surface of SnO ₂ is easily affected by high concentration hydrogen plasma, the formation conditions of the diamond-like carbon layer formed by the plasma CVD method to stabilize the surface of SnO ₂ , for example, the raw material gas flow rate ratio And the amount of high frequency power input, temperature, etc. are also restricted. The formation conditions of the diamond-like carbon layer described in Example 1 of Patent Document 2 by the plasma CVD method are such that methane (CH ₄ ) and hydrogen (H ₂ ) are flowed as a raw material gas at a flow rate ratio of 1: 1, 13 It is disclosed that 100 W of high frequency power of .56 MHz is applied and the film is formed with a film thickness of about 2 nm. However, when ZnO is used as the transparent electrode, the plasma resistance is higher than that of SnO ₂ , but the ohmic characteristics of the semiconductor layer formed thereon, particularly the amorphous semiconductor layer, are generally not excellent. Therefore, it was found that the characteristics were not improved in the example of Patent Document 2.

  In view of the above problems, as a result of intensive studies on a method of obtaining a photoelectric conversion device having higher output characteristics, a transparent electrode is used, and a ZnO film having surface irregularities effective for light confinement is used for the transparent electrode, and hydrogen is formed thereon The present inventors have found that a photoelectric conversion device that makes use of the characteristics of a transparent electrode mainly composed of a ZnO film can be formed by forming the carbonized carbon film under appropriate conditions, and devise the present invention. It came to.

  In order to solve the above problems, the present invention provides a step of forming a transparent electrode containing zinc oxide on a light-transmitting insulating substrate, and forming a hydrogenated carbon film on the transparent electrode, and the hydrogenated carbon film. A method for manufacturing a photoelectric conversion device comprising a step of sequentially laminating at least one photoelectric conversion unit and a back electrode, wherein the hydrogenated carbon film is a hydrocarbon diluted with hydrogen gas in a range of 5 to 200 times It is characterized in that the system raw material gas is decomposed and formed at a high frequency.

  Furthermore, the transparent electrode of the photoelectric conversion device of the present invention can be formed by a low pressure CVD method. In addition, the hydrogenated carbon film of the photoelectric conversion device of the present invention can be formed by a plasma CVD method.

  ADVANTAGE OF THE INVENTION According to this invention, the performance of a photoelectric conversion apparatus can be improved using the transparent electrode excellent in the light confinement effect which can be formed with a cheap manufacturing method on a board | substrate.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a thin film photoelectric conversion device 6 manufactured by using one embodiment of the present invention. A photoelectric conversion device 6 in FIG. 1 includes a transparent electrode 2, a hydrogenated carbon film 3, a one-conductivity-type layer 41 that constitutes a photoelectric conversion unit 4, an intrinsic photoelectric conversion layer 42, and reverse conductivity on a translucent insulating substrate 1. The mold layer 43 and the back electrode 5 are sequentially deposited. Sunlight (hν) to be subjected to photoelectric conversion is incident on the photoelectric conversion device 6 from the translucent insulating substrate 1 side.

  In addition, since the translucent insulating substrate 1 is located on the light incident side when the photoelectric conversion device is configured, it is preferable that the translucent insulating substrate 1 is as transparent as possible so that more sunlight is transmitted and absorbed by the photoelectric conversion unit. As the material, a glass plate, a translucent plastic film or the like is used. For the same purpose, it is desirable to apply a non-reflective coating to the light incident surface of the translucent insulating substrate 1 so as to reduce the light reflection loss on the light incident surface of sunlight.

  The transparent electrode 2 side of the transparent insulating substrate 1 may be provided with fine surface irregularities on the surface of the transparent insulating substrate 1 in order to improve the adhesion of the transparent electrode 2.

The transparent electrode 2 is preferably mainly composed of ZnO. This is because ZnO has higher plasma resistance than SnO ₂ and ITO, and the ZnO film is difficult to be reduced even in a deposition environment of the photoelectric conversion layer with a large plasma density using hydrogen. Therefore, since it is difficult for absorption of incident light at the blackened portion of the reduced film and the amount of transmitted light to the photoelectric conversion layer is low, it is suitable as a transparent electrode material for a thin film photoelectric conversion device. Moreover, since the transparent electrode 2 plays the role which acquires the light confinement effect suitable for a thin film photoelectric conversion apparatus, it needs to have a surface asperity. In the present invention, the haze ratio is mainly used as an evaluation index of the unevenness of the transparent electrode. The haze ratio is expressed by (diffuse transmittance / total light transmittance) × 100 [%] (JIS K7136). As a simple evaluation method of the haze ratio, measurement with a haze meter using a D65 light source or a C light source is generally used.

The surface unevenness of the transparent electrode layer 2 has a haze ratio of about 10 to 40% in a state where the transparent electrode layer 2 is formed on the translucent insulating substrate 1 in order to obtain a light confinement effect suitable for the photoelectric conversion device. It is preferable to have. The average height difference of the surface irregularities of the transparent electrode having such a haze ratio is about 10 to 300 nm. When the surface unevenness of the transparent conductive film 2 is too small, a sufficient light confinement effect cannot be obtained, and when it is too large, an electrical and mechanical short circuit is caused in the photoelectric conversion device. Causes deterioration of characteristics. Such a transparent electrode 2 can be formed by a vapor deposition method, a low pressure CVD method or the like which is simpler than the high pressure thermal CVD method which requires a large facility, but is preferably formed by a low pressure CVD method. This is because ZnO can form a texture having a light confinement effect even at a low temperature of 200 ° C. or lower. The low-pressure CVD method is preferable in terms of manufacturing cost because it can form a film at a deposition rate one digit or more faster than the sputtering method and has high utilization efficiency of raw materials. For example, the transparent electrode layer 2 of the present invention is formed of a substrate temperature of 150 ° C. or higher, a pressure of 5 to 1000 Pa, and a source gas of diethyl zinc (DEZ), water, a doping gas, and a dilution gas. In addition to this, dimethyl zinc can also be used as the zinc source gas. Examples of oxygen source gases include oxygen, carbon dioxide, carbon monoxide, dinitrogen oxide, nitrogen dioxide, sulfur dioxide, dinitrogen pentoxide, alcohols (R (OH)), and ketones (R (CO) R ′). , Ethers (ROR ′), aldehydes (R (COH)), amides ((RCO) _x (NH _3−x ), x = 1,2,3), sulfoxides (R (SO) R ′) (However, R and R ′ are alkyl groups). As the dilution gas, a rare gas (He, Ar, Xe, Kr, Rn), nitrogen, hydrogen, or the like can be used. As the doping gas, diborane (B ₂ H ₆ ), alkylaluminum, alkylgallium, or the like can be used. The ratio of DEZ to water is preferably 1: 1 to 1: 5, and the ratio of B ₂ H _{6 to} DEZ is preferably 0.05% or more. Since DEZ and water are liquids at normal temperature and normal pressure, they are vaporized by methods such as heat evaporation, bubbling, and spraying before being supplied. When the film thickness of ZnO is 500 to 3000 nm, a thin film having surface irregularities having a particle size of approximately 50 to 500 nm and an average height difference of irregularities of approximately 10 to 300 nm is obtained, and the light confinement effect of the photoelectric conversion device is obtained. This is preferable. The substrate temperature here means the temperature of the surface where the substrate is in contact with the heating unit of the film forming apparatus.

  The average film thickness of the transparent electrode 2 of the present invention is preferably 500 to 2000 nm, and more preferably 800 to 1800 nm. This is because if the ZnO film is too thin, it will be difficult to sufficiently provide unevenness that effectively contributes to the light confinement effect, and it will be difficult to obtain the necessary conductivity as a transparent electrode. This is because the amount of light that passes through ZnO and reaches the photoelectric conversion unit is reduced, so that the efficiency is lowered. Furthermore, when it is too thick, the film forming cost increases due to an increase in the film forming time. In the case of the average film thickness of the transparent electrode 2, the average height difference of the surface irregularities is approximately 10 to 100 nm.

The hydrogenated carbon film 3 formed on the transparent electrode 2 is preferably formed by a plasma CVD method. This is because the hydrogenated carbon film 3 is located closer to the light incident side than the photoelectric conversion unit 4, and therefore it is necessary to form the hydrogenated carbon film 3 that may cause light absorption loss with the minimum necessary film thickness. This is because the plasma CVD method can form a thin film with good control. In addition, the photoelectric conversion unit 4 to be subsequently formed is also preferable in that it can be formed using the same method. For example, the hydrogenated carbon film 3 of the present invention is formed of a substrate temperature of 100 to 300 ° C., a pressure of 30 to 2000 Pa, and a source gas mainly composed of methane (CH ₄ ) and hydrogen. In addition, a doping gas such as B ₂ H ₆ used for the p-type layer of the next photoelectric conversion unit may be included. As the raw material gas for the hydrogenated carbon film 3, a hydrocarbon gas such as ethane, propane, butane, ethylene, acetylene or the like can be used. The hydrocarbon-based source gas is preferably diluted with hydrogen gas in a range of 5 to 200 times, and more preferably in a range of 5 to 100 times. This is because, under the conditions for forming the hydrogenated carbon film 3 of the present invention, not only the hydrogenated carbon film 3 is formed but also the purpose of supplying hydrogen atoms decomposed by plasma to the transparent electrode 2 serving as an underlayer. Because. However, if the dilution ratio is too large, the deposition rate of the hydrogenated carbon film 3 is decreased, and a film deposited with hydrogen atoms may be etched in parallel with the deposition of the film, which is not preferable. When the plasma CVD method is used, the high frequency power is preferably applied at 100 to 800 mW / cm ² , and more preferably 200 to 500 mW / cm ² . This is because if the amount of high-frequency power applied is too small, the decomposition rate of the raw material gas is lowered, so that the deposition rate of the hydrogenated carbon film 3 is slowed and the manufacturing cost may increase. On the other hand, if the amount of high-frequency power applied is too large, the deposition rate of the hydrogenated carbon film 3 becomes too fast, making it difficult to control the thin film thickness. Further, the hydrogenated carbon film 3 of the present invention is characterized in that it is formed with a large high-frequency power as compared with Patent Document 2. By using this method, the transparent electrode 2 mainly composed of ZnO is exposed to hydrogen decomposed by a large amount of plasma, thereby making it possible to reduce resistance and to achieve both high transmittance and low resistance. High efficiency of the conversion device can be realized.

  Since the hydrogenated carbon film 3 may hinder light absorption into the photoelectric conversion unit 4, it is necessary to form the film thickness as thin as possible. The average film thickness of the hydrogenated carbon film 3 is 1 to 20 nm. Preferably there is. Conversely, if it is too thin, the effect of the present invention is not exhibited, and therefore there is a suitable range for the average film thickness of the hydrogenated carbon film 3. Further, by forming the hydrogenated carbon film 3, it becomes possible to prevent post-oxidation of crystal grain boundaries and other chemical changes related to the surface irregularities of the transparent electrode 2 formed by using the low pressure CVD method.

  The photoelectric conversion unit 4 formed on the hydrogenated carbon film 3 may be a single photoelectric conversion unit as illustrated, but a plurality of photoelectric conversion units may be stacked. As the photoelectric conversion unit 4, one having absorption in the main wavelength range (400 to 1200 nm) of sunlight is preferable. For example, a crystalline silicon-based photoelectric conversion unit in which a crystalline silicon-based thin film is an intrinsic photoelectric conversion layer 42 is exemplified. . In addition to silicon, “silicon-based” materials include silicon alloy semiconductor materials containing silicon such as silicon carbide and silicon germanium.

  The crystalline silicon-based photoelectric conversion unit is formed by stacking semiconductor layers by plasma CVD, for example, in the order of pin type. Specifically, for example, a p-type microcrystalline silicon-based layer doped with 0.01 atomic% or more of boron, which is a conductivity type determining impurity atom, an intrinsic crystalline silicon layer serving as a photoelectric conversion layer, and a conductivity type determining impurity atom An n-type microcrystalline silicon-based layer doped with 0.01 atomic% or more of certain phosphorus may be deposited in this order. However, these layers are not limited to the above. For example, an amorphous silicon film may be used as the p-type layer. Further, an alloy material such as amorphous or microcrystalline silicon carbide or silicon germanium may be used for the p-type layer. Note that the film thickness of the conductive (p-type, n-type) microcrystalline silicon-based layer is preferably 3 nm to 100 nm, and more preferably 5 nm to 50 nm.

The intrinsic crystalline silicon layer that is the intrinsic photoelectric conversion layer 42 is preferably formed by a plasma CVD method at a substrate temperature of 300 ° C. or lower. By forming at a low temperature, it is preferable to include many hydrogen atoms that terminate and inactivate defects in the grain boundaries and grains. Specifically, the hydrogen content of the photoelectric conversion layer is preferably in the range of 1 to 30 atomic%. This layer is preferably formed as a thin film which is a substantially intrinsic semiconductor having a conductivity type determining impurity atom density of 1 × 10 ¹⁸ cm ⁻³ or less. Further, most of the crystal grains contained in the intrinsic crystalline silicon layer are grown in a columnar shape from the transparent electrode 2 side, and preferably have a (110) preferential orientation plane with respect to the film surface. The film thickness of the intrinsic crystalline silicon layer is preferably 1 μm or more from the viewpoint of light absorption, and preferably 10 μm or less from the viewpoint of suppressing peeling due to internal stress of the crystalline thin film. However, since the thin film crystalline photoelectric conversion unit preferably has absorption in the main wavelength region of sunlight (400 to 1200 nm), instead of the intrinsic crystalline silicon layer, a crystalline silicon carbide layer (alloy material) ( For example, a crystalline silicon carbide layer made of crystalline silicon containing 10 atomic% or less of carbon or a crystalline silicon germanium layer (for example, a crystalline silicon germanium layer made of crystalline silicon containing 30 atomic% or less of germanium) It may be formed.

A back electrode 5 is formed on the photoelectric conversion unit 4. As the back electrode, it is preferable to form at least one metal layer 52 made of at least one material selected from Al, Ag, Au, Cu, Pt and Cr by sputtering or vapor deposition. Further, it is preferable to form a conductive oxide layer 51 such as ITO, SnO ₂ , or ZnO between the photoelectric conversion unit 4 and the metal layer 52. The conductive oxide layer 51 enhances the adhesion between the photoelectric conversion unit 4 and the metal layer 52, increases the light reflectance of the back electrode 5, and further prevents chemical changes in the photoelectric conversion unit layer 4. It has a function.

  Although not shown, as one embodiment of the present invention, there is a tandem photoelectric conversion device in which an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit are sequentially stacked on a hydrogenated carbon film 3. The amorphous photoelectric conversion unit includes a one conductivity type layer, an intrinsic amorphous photoelectric conversion layer, and a reverse conductivity type layer. If an amorphous silicon-based material is selected as the amorphous photoelectric conversion unit, it has sensitivity to light of about 360 to 800 nm, and if a crystalline silicon-based material is selected for the crystalline photoelectric conversion unit, it is longer than about 1200 nm. Sensitivity to light up to. Therefore, the solar cell arranged in the order of the amorphous silicon-based photoelectric conversion unit and the crystalline silicon-based photoelectric conversion unit from the light incident side becomes a photoelectric conversion device that can effectively use incident light in a wider range. The crystalline photoelectric conversion unit is formed in the same manner as in the above embodiment.

The amorphous photoelectric conversion unit is formed by stacking each semiconductor layer by a plasma CVD method in the order of, for example, a pin type. Specifically, for example, a p-type amorphous silicon-based layer doped with 0.01 atomic% or more of boron, which is a conductivity-determining impurity atom, an intrinsic amorphous silicon-based layer that becomes a photoelectric conversion layer, and a conductivity-type determination An n-type amorphous silicon-based layer doped with 0.01 atomic% or more of phosphorus, which is an impurity atom, may be deposited in this order. However, these layers are not limited to the above. For example, a microcrystalline silicon film may be used as the p-type layer. Further, an alloy material such as amorphous or microcrystalline silicon carbide, silicon nitride, silicon oxide, silicon germanium, or the like may be used for the p-type layer. In terms of ohmic characteristics between the hydrogenated carbon film 3 and the p-type layer, it is preferable to use a microcrystalline film. However, a thin microcrystalline film and a conventional amorphous film are used in order to achieve both a short-circuit current and an open-circuit voltage. A structure in which these films are laminated may also be used. As the intrinsic amorphous semiconductor layer, an alloy material such as silicon carbide or silicon germanium may be used. The intrinsic amorphous silicon-based layer preferably contains 2 to 15% of hydrogen in the film in order to reduce the defect density in the film and reduce the recombination current loss of the thin film photoelectric conversion device. In addition, the intrinsic amorphous silicon-based layer desirably has a thickness of 50 nm to 500 nm in order to reduce deterioration due to light irradiation. A microcrystalline silicon film may be used as the n-type layer. Note that the film thickness of the conductive type (p-type, n-type) microcrystalline silicon-based layer or amorphous silicon-based layer is preferably 3 nm to 100 nm, and more preferably 5 nm to 50 nm.
Finally, when the photoelectric conversion device is a thin film solar cell or the like, the back surface side is protected by attaching a sealing resin (not shown).

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the following description examples, unless the meaning is exceeded.

Example 1
As Example 1, a photoelectric conversion device 6 shown in FIG.

  A glass substrate having a thickness of 0.7 mm and a 125 mm square was used as the translucent insulating substrate 1, and B-doped ZnO was formed thereon with a thickness of 1.5 μm as the transparent electrode 2 by low-pressure CVD. The transparent electrode 2 is formed by a CVD method under a reduced pressure condition with a substrate temperature of 160 ° C., diethyl zinc (DEZ) and water as source gases, and diborane gas as a dopant gas. The obtained substrate with a transparent electrode had a sheet resistance of about 15Ω / □ and a haze ratio of 30%. The total light transmittance of the obtained substrate with a transparent electrode was measured with a spectrophotometer by entering light from the glass side. A transmittance of approximately 80% or more was exhibited in the wavelength range of 400 to 1200 nm.

Subsequently, a hydrogenated carbon film 3 having a thickness of 2 nm was formed on the transparent electrode 2 by a plasma CVD method. When forming a hydrogenated carbon film 3, a substrate temperature of 180 ° C., as a material gas, using CH ₄ and hydrogen. The dilution ratio of CH ₄ with hydrogen was 10 times, and 300 mW / cm ² was applied as RF power using RF. The obtained substrate with a transparent electrode after forming the hydrogenated carbon film 3 had a sheet resistance of about 10Ω / □ and a haze ratio of 28%. This decrease in sheet resistance is presumed to be due to plasma-decomposed hydrogen atoms included in the conditions for forming the hydrogenated carbon film 3. In addition, since the light transmittance in the wavelength range of 400 to 1200 nm was hardly changed before and after the formation of the hydrogenated carbon film 3, the transparent electrode was not reduced under the conditions for forming the hydrogenated carbon film 3. It can be seen that almost no light absorption occurs in the hydrogenated carbon film 3 portion.

  Subsequently, a p-type microcrystalline silicon layer 41 having a thickness of 15 nm, an intrinsic crystalline silicon photoelectric conversion layer 42 having a thickness of 1.5 μm, and an n-type microcrystalline silicon layer having a thickness of 15 nm are formed on the hydrogenated carbon film 3. A crystalline silicon photoelectric conversion unit 4 composed of 43 was sequentially formed by a plasma CVD method. Thereafter, Al-doped ZnO 51 having a thickness of 90 nm and Ag 52 having a thickness of 200 nm were sequentially formed as the back electrode 5 by sputtering.

When the photoelectric conversion device 6 obtained as described above was irradiated with AM 1.5 light at 100 mW / cm ² and measured for output characteristics, the open circuit voltage (Voc) was 0.548 V and the short-circuit current density (Jsc). ) Was 25.0 mA / cm ² , the fill factor (FF) was 0.727, and the conversion efficiency was 10.0%.

(Example 2)
Also in Example 2, the photoelectric conversion device 6 was produced in the same manner as in Example 1. However, the difference from Example 1 is that the thickness of the hydrogenated carbon film 3 is set to 4 nm. The substrate with a transparent electrode after forming the hydrogenated carbon film 3 obtained under these conditions had a sheet resistance of about 10Ω / □ and a haze ratio of 27%. Further, when the light of AM1.5 photoelectric conversion device 6 obtained was measured output characteristic by irradiating with 100 mW / cm ² light intensity, Voc is 0.545V, Jsc is 24.8mA / ^cm 2, F. F. Was 0.728, and the conversion efficiency was 9.8%.
(Example 3)
Also in Example 3, the photoelectric conversion device 6 was produced in the same manner as in Example 1. However, the difference from Example 1 is that the thickness of the hydrogenated carbon film 3 is 9 nm. When the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM 1.5 light at a light quantity of 100 mW / cm ² , Voc was 0.544 V, Jsc was 24.5 mA / cm ² , F.I. F. Was 0.730 and the conversion efficiency was 9.7%.
Example 4
Also in Example 4, the photoelectric conversion device 6 was produced in the same manner as in Example 1. However, the difference from Example 1 is that the dilution ratio of CH ₄ with hydrogen when forming the hydrogenated carbon film 3 is set to 20 times. When the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM 1.5 light at a light amount of 100 mW / cm ² , Voc was 0.546 V, Jsc was 24.9 mA / cm ² , F.I. F. Was 0.730 and the conversion efficiency was 9.9%.
(Example 5)
Also in Example 5, the photoelectric conversion device 6 was produced in the same manner as in Example 1. However, the difference from Example 1 is that high frequency power for forming the hydrogenated carbon film 3 was applied at 500 mW / cm ² . When the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM 1.5 light at a light quantity of 100 mW / cm ² , Voc was 0.546 V, Jsc was 24.8 mA / cm ² , F.I. F. Was 0.735, and the conversion efficiency was 10.0%.
(Comparative Example 1)
In Comparative Example 1, a photoelectric conversion device 6 was produced in substantially the same manner as in Example 1. However, the difference from Example 1 is that the hydrogenated carbon film 3 was not formed.

When the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM 1.5 light at a light quantity of 100 mW / cm ² , Voc was 0.502 V, Jsc was 25.1 mA / cm ² , F.R. F. Was 0.681, and the conversion efficiency was 8.6%. When this result is compared with the result of Example 1, Voc and F.R. F. There is a decrease in the value of. This is considered to be due to the influence of the sheet resistance of the transparent electrode portion in contact with the photoelectric conversion unit, and it can be inferred that the difference in the series resistance of the photoelectric conversion device is caused by the difference in this value.
(Comparative Example 2)
In Comparative Example 2, a photoelectric conversion device 6 was produced in substantially the same manner as in Example 1. However, the difference from Example 1 is that, among the conditions for depositing the hydrogenated carbon film 3, CH ₄ was not added. Therefore, this condition is that the transparent electrode 2 is exposed to hydrogen atoms decomposed by plasma, and the substrate with the transparent electrode obtained after the hydrogen plasma treatment obtained under this condition has a sheet resistance of about 11Ω / □ and a haze ratio. Was 29%. Furthermore, the light transmittance in the wavelength range of 400 to 1200 nm gradually decreased in almost all wavelength regions after exposure to hydrogen atoms decomposed by plasma. Therefore, in this condition without the addition of CH _4, also a transparent electrode composed of ZnO that is highly plasma resistance, notice that the surface depending on the conditions is reduced, contrary to the conditions of Example 1 is CH ₄ It was found that the conditions can prevent the reduction by adding.

Further, when the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM 1.5 light at a light quantity of 100 mW / cm ² , Voc was 0.533 V, Jsc was 23.6 mA / cm ² , F.D. F. Was 0.724, and the conversion efficiency was 9.1%. When this result is compared with the result of Example 1, the value of Jsc is significantly reduced. This is considered to be due to light absorption due to reduction of the transparent electrode portion.
(Comparative Example 3)
In Comparative Example 3, a diamond-like carbon film was formed on the transparent electrode 2 mainly made of ZnO by using a method substantially similar to Example 1 described in Patent Document 2. However, Patent Document 2 is different in that SnO ₂ is used for the transparent electrode, and the details of the substrate material, the substrate temperature, and the numerical value per unit area when applying high-frequency power are unclear. The conditions that could be compared were selected and implemented. As the translucent insulating substrate 1, a glass substrate having a thickness of 0.7 mm and a 125 mm square was used as in Example 1 of the present invention, and the transparent electrode 2 was formed under the same conditions as in Example 1. Subsequently, when the diamond-like carbon film is formed, the substrate temperature is set to 180 ° C., CH ₄ and hydrogen are used at a flow rate ratio of 1: 1, and 100 mW / cm ² is applied to the high-frequency power using RF. About 2 nm. Incidentally, when a diamond-like carbon film was formed on a transparent electrode made of SnO _{2 under these} conditions, the transmittance was slightly reduced due to the reduction of the transparent electrode. It is guessed. The obtained substrate with a transparent electrode after the formation of the hydrogenated carbon film 3 had a sheet resistance of about 16Ω / □ and a haze ratio of 29%. The value of the sheet resistance is the same as that before the hydrogenated carbon film 3 is formed or slightly increased. The conditions for forming the hydrogenated carbon film 3 in Comparative Example 3 are the transparent electrode made of ZnO of the present invention. It was found that there was no effect to lower the sheet resistance. Moreover, although the total light transmittance of the obtained substrate with a transparent electrode showed 80% or more in a wavelength range of 400 to 1200 nm, compared with Example 1 of the present invention, the transmittance was lower in all wavelength regions. Thus, it is estimated that the permeability of the hydrogenated carbon film of Comparative Example 3 is lower than that of Example 1.

Subsequently, a photoelectric conversion device 6 was produced on the transparent electrode by the same method as described in Example 1 of the present invention. When the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM1.5 light at a light amount of 100 mW / cm ² , Voc was 0.505 V, Jsc was 24.4 mA / cm ² , F.D. F. Was 0.676, and the conversion efficiency was 8.3%. When this result is compared with the result of Example 1, Voc and F.R. F. There is a significant decrease in the value of. This is thought to be due to the fact that the sheet resistance of the transparent electrode portion is high and the ohmic characteristics of the hydrogenated carbon film and the photoelectric conversion unit are worse than those of Example 1.
(Comparative Example 4)
In Comparative Example 4, a photoelectric conversion device 6 was produced in substantially the same manner as in Example 1 of the present invention. However, the difference from Example 1 is that SnO ₂ was used for the transparent electrode. Incidentally, SnO ₂ transparent electrode was used as the fluorine-doped conventionally used in thin film solar cells. When the hydrogenated carbon film 3 was produced on the transparent electrode 2 mainly made of SnO ₂ using the same method as in Example 1, the obtained substrate with a transparent electrode had a sheet resistance of about 8Ω / □, haze. The rate was 15%. However, since the SnO ₂ film surface of the obtained substrate with a transparent electrode was brown, it is assumed that the transparent electrode was reduced. Therefore, it can be said that the conditions used for forming the hydrogenated carbon film are unsuitable for the transparent electrode 2 made of SnO _{2 having} low plasma resistance because the transmittance is reduced by the reduction of the transparent electrode.

Further, when the output characteristics were measured by irradiating the obtained photoelectric conversion device 6 with AM1.5 light at a light amount of 100 mW / cm ² , Voc was 0.500 V, Jsc was 18.3 mA / cm ² , F.D. F. Was 0.603, and the conversion efficiency was 5.5%. When this result is compared with the result of Example 1, there is a decrease in all parameters. In particular, the significant decrease in Jsc is considered to be due to the fact that the transparent electrode portion was reduced under a high plasma density condition containing a lot of hydrogen, resulting in a decrease in transmittance in all wavelength regions.

  Table 1 summarizes the main configuration and characteristics of the transparent electrode 2 according to the above-described Examples 1 to 5 and Comparative Examples 1 to 4, and the measurement results of the output characteristics of the crystalline photoelectric conversion device produced using each transparent electrode. Is.

表１の結果から分かるように、実施例１〜５のいずれにおいても、比較例１〜４を上回る変換効率の光電変換装置を得た。

As can be seen from the results in Table 1, in any of Examples 1 to 5, a photoelectric conversion device having a conversion efficiency exceeding Comparative Examples 1 to 4 was obtained.

As described above in detail, according to the present invention, it is possible to provide a method for manufacturing a photoelectric conversion device with improved performance by using a transparent electrode excellent in light confinement effect that can be formed by an inexpensive method. .

Sectional drawing of the photoelectric conversion apparatus which is one Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent insulated substrate 2 Transparent electrode 3 Hydrogenated carbon film | membrane 4 Photoelectric conversion unit 41 One conductivity type layer 42 Intrinsic photoelectric conversion layer 43 Reverse conductivity type layer 5 Back surface electrode 51 Conductive oxide layer 52 Metal layer 6 Photoelectric conversion apparatus

Claims (3)

  Forming a transparent electrode containing zinc oxide on a light-transmitting insulating substrate and forming a hydrogenated carbon film on the transparent electrode; at least one photoelectric conversion unit on the hydrogenated carbon film; and a back electrode In the step of forming the hydrogenated carbon film, in the step of forming the hydrogenated carbon film, the hydrocarbon-based source gas diluted with hydrogen gas in a range of 5 to 200 times is produced at a high frequency. A method for producing a photoelectric conversion device, comprising decomposing to form the hydrogenated carbon film.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein the transparent electrode is formed by a low-pressure CVD method.   The method of manufacturing a photoelectric conversion device according to claim 1, wherein the hydrogenated carbon film is formed by a plasma CVD method.

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