JP2009267222A - Manufacturing method of substrate with transparent conductive film for thin-film photoelectric converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of manufacturing a transparent electrode for photoelectric converter with less fluctuations in the electrical characteristics on a substrate and superior light confinement effect, and capable of improving the performance of a thin-film photoelectric converter by using the method. <P>SOLUTION: The method for manufacturing a substrate with transparent conductive film for photoelectric converter includes: a process, wherein a first transparent electrode layer having surface roughness where zinc oxide is doped with impurities at a certain concentration is formed, in the order starting from the substrate side, by using a low pressure CVD method; and a process, wherein a second transparent electrode layer is formed by increasing the amount of raw material gas of zinc in a range that is 1.2-3 times higher, as compared with that in the first transparent electrode layer. The time for forming the second transparent electrode layer is in a range of 1/25 to 1/5 of the time for the formation of the first transparent electrode layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a transparent conductive film for a thin film photoelectric conversion device and improvement of a thin film photoelectric conversion device using the same.

  Photoelectric conversion devices are used in various fields such as light receiving sensors and solar cells. In particular, in a solar cell, in order to achieve both low cost and high efficiency, a thin film solar cell with a small amount of raw material used has attracted attention and its development has been energetically performed. Among these, a method of forming a high-quality semiconductor layer on a low-priced substrate such as glass using a low-temperature process of 400 ° C. or lower 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.

Conventionally, a transparent conductive film such as tin oxide (SnO ₂ ) or indium tin oxide (ITO) has been used as a transparent electrode material in the thin film solar cell having such a configuration. Recently, however, low-cost zinc oxide (ZnO) has been used to further reduce the manufacturing cost of thin-film solar cells.

  In addition, thin-film solar cells can make the photoelectric conversion layer thinner than solar cells using conventional bulk single crystals or polycrystalline silicon. However, the light absorption of the entire thin film is limited by the film thickness. There is a problem of being done. 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.

  (Prior Example 1) For example, the transparent conductive film for photoelectric conversion device disclosed in Patent Document 1 is a film that forms a ZnO film by using a low-pressure CVD method, and does not perform wet etching of the transparent conductive film. Since the surface irregularities can be effectively increased without increasing the film thickness, it is disclosed that if this transparent conductive film is applied to a thin film photoelectric conversion device, a thin film photoelectric conversion device with improved photoelectric conversion characteristics can be provided. Yes. 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, 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.

On the other hand, the ZnO film has a problem that its electrical characteristics are likely to be deteriorated by exposure to moisture as compared with a SnO ₂ film or an ITO film used as a material for a transparent electrode. Furthermore, in Non-Patent Document 1, a ZnO film for an amorphous thin-film solar cell is formed on a glass substrate by a photo-MOCVD method under a low temperature condition of 130 ° C. However, as it is, unreacted H ₂ O is formed. It is disclosed that it remains in the ZnO film. Therefore, it is shown that by annealing in an Ar atmosphere at 300 ° C., the remaining H ₂ O can be removed from the ZnO film, and the characteristics of the amorphous thin film solar cell can be improved.
JP 2007-288043 A WW Wenas et al., Technical Digest of the International PVSEC-7, AI-4, 1993

  The object of the present invention is to make the surface unevenness of a transparent electrode for a photoelectric conversion device used for a thin film solar cell effective for light confinement, and to manufacture a transparent electrode for a photoelectric conversion device that improves the performance of the photoelectric conversion device at low cost. It is to provide a method, and further to improve the performance of the photoelectric conversion device using the method.

  When a ZnO film having surface irregularities using a low-temperature process of 200 ° C. or lower was examined using a low-pressure CVD method, the obtained transparent conductive film is one of electrical characteristics when left for several months. The subject that sheet resistance rose and the characteristic as a transparent electrode deteriorated became clear.

  This problem is improved by the method of annealing in an Ar atmosphere at 300 ° C. described in Non-Patent Document 1, but the equipment cost increases because of the 300 ° C. treatment, and the transparent electrode itself is manufactured at a low temperature process of 200 ° C. Since the advantages that can be made cannot be utilized, there is a problem in realizing cost reduction with the ZnO film.

  In view of the above problems, in a method for forming a transparent conductive film itself using a low-pressure CVD method, a method for obtaining a transparent electrode with little variation in electrical characteristics and sufficient for a thin film photoelectric conversion device has been intensively studied. In the layer on the surface side, that is, on the photoelectric conversion unit side, by forming the zinc raw material and the dopant amount on the condition that the amount of the dopant is increased from that on the substrate side, there may be a case where a transparent electrode with little fluctuation in electrical characteristics and high light confinement effect can be formed. The present inventors have found that there is, and have come up with the present invention.

  In order to solve the above problems, a first aspect of the present invention is a method for manufacturing a substrate with a transparent conductive film for a photoelectric conversion device, which is converted to zinc oxide at a constant concentration in order from the substrate side using a low-pressure CVD method. A step of forming a first transparent electrode layer having surface irregularities doped with impurities, and a second transparent electrode layer by increasing the amount of zinc source gas in a range of 1.2 to 3 times that of the first transparent electrode layer The time for forming the second transparent electrode layer is in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer. It is a manufacturing method of a board | substrate with a transparent conductive film.

  The present invention is also a method for producing a substrate with a transparent conductive film for a photoelectric conversion device, wherein the low-pressure CVD method has surface irregularities in which zinc oxide is doped with impurities at a constant concentration in order from the substrate side. A step of forming one transparent electrode layer, and the amount of source gas of zinc is increased to a range of 1.2 to 3 times that of the first transparent electrode layer, and the impurity doping amount is set to a range of 1.2 to 3 times And forming a second transparent electrode layer, and the time for forming the second transparent electrode layer is in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer. It is a manufacturing method of the board | substrate with a transparent conductive film for photoelectric conversion apparatuses characterized by these.

  In the present specification, the term “low pressure CVD method” means a thermochemical vapor deposition method using a gas having a pressure lower than atmospheric pressure. In other words, the low pressure CVD method is also called a low pressure CVD method or a low pressure CVD method (Low Pressure CVD method: abbreviated as LP-CVD method), and a thermochemical vapor deposition method using a gas having a pressure lower than the atmospheric pressure. Is defined. Normally, the term “CVD” means “thermal CVD” except when the energy source is clearly indicated, such as “plasma CVD”, “photo CVD”, etc. It is synonymous with “thermal CVD method”. The low-pressure thermal CVD method also includes a metal organic CVD method under reduced pressure (abbreviation, MOCVD method).

  Further, in the present specification, the terms “crystalline” and “microcrystalline” also mean those partially including an amorphous state as commonly used in the art. ing.

  ADVANTAGE OF THE INVENTION According to this invention, the transparent electrode suitable for the thin film photoelectric conversion apparatus with a large light confinement effect with an inexpensive manufacturing method can be provided, and the performance of a photoelectric conversion apparatus can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings of the present specification, dimensional relationships such as thickness and length are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a thin film photoelectric conversion device 5 using a transparent conductive film for a photoelectric conversion device manufactured using one embodiment of the present invention. The photoelectric conversion device 5 in FIG. 1 has a first transparent electrode layer 21 and a second transparent electrode layer 22 that constitute the transparent electrode 2 on the translucent insulating substrate 1, and one conductivity that constitutes the crystalline photoelectric conversion unit 3. The mold layer 31, the crystalline intrinsic photoelectric conversion layer 32, the reverse conductivity type layer 33, and the back electrode 4 are sequentially deposited. Sunlight (hν) to be subjected to photoelectric conversion is incident on the photoelectric conversion device 5 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 (not shown) 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 translucent insulating substrate 1 may be provided with fine surface irregularities (not shown) on the surface of the translucent insulating substrate 1 in order to improve the adhesion of the transparent electrode 2.

The transparent electrode 2 has a two-layer structure in which transparent electrode layers are continuously deposited under the first and second film forming conditions, and it is preferable that both are 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, absorption of incident light due to blackening of the film due to reduction is unlikely to occur, and the possibility that the amount of light transmitted to the photoelectric conversion layer is reduced is low. Therefore, it is suitable as a transparent electrode material for a thin film photoelectric conversion device. In addition, the transparent electrode 2 has, in order from the translucent insulating substrate 1 side, a first transparent electrode layer 21 having surface irregularities in which zinc oxide is doped with an impurity at a certain concentration, and zinc is more than the first transparent electrode layer 21. The second transparent electrode layer 22 formed by increasing the amount of the source gas in a range of 1.2 to 3 times is laminated. The first transparent electrode layer 21 mainly plays a role of obtaining a light confinement effect suitable for a thin film photoelectric conversion device, and the second transparent electrode layer has electrical characteristics generated when the formed transparent conductive film is later exposed to moisture. Mainly plays a role in suppressing the deterioration of By providing the second transparent electrode layer 22, it is possible to design an electrode capable of improving the characteristics of the thin film photoelectric conversion device with almost no decrease in light transmittance than when the first transparent electrode layer 21 is used alone. It becomes. 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 2 has a haze ratio of about 10 to 40% in a state where the transparent electrode 2 is formed on the translucent insulating substrate 1 in order to obtain a light confinement effect suitable for the thin film photoelectric conversion device. It is preferable. 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 electrode 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 a drop. 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 first transparent electrode layer 21 which is the transparent electrode 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 raw material gas of diethyl zinc (DEZ), water, a doping gas, and a dilution gas. The In addition to this, dimethylzinc 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 second transparent electrode layer 22 to be subsequently formed is preferably formed by the same method as that for the first transparent electrode layer 21, that is, the low pressure CVD method. This is because the same apparatus can be used and the characteristics of the transparent conductive film can be improved only by the film forming conditions. The second transparent electrode layer 22 preferably increases the amount of the raw material gas of zinc in a range of 1.2 to 3 times the formation condition of the first transparent electrode layer 21. If the amount of the raw material gas is too small, the sufficient effect of the present invention cannot be obtained, and if it is too large, the total light transmittance of the transparent electrode 2 is reduced. Moreover, when forming the 2nd transparent electrode layer 22, it is preferable to increase the impurity doping amount to the range of 1.2 to 3 times simultaneously. This is because if the impurity doping amount is increased within this range, the carrier concentration in the transparent conductive film does not decrease too much, and the electrical connection with the photoelectric conversion unit to be formed next becomes good. Conversely, a transparent conductive film doped with impurities at a high concentration has a high carrier concentration and a low resistance, but the light transmittance of the film is low, which may hinder light absorption into the photoelectric conversion device. The time for forming the second transparent electrode layer 22 is preferably in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer 21. This is because if the formation time is too short, sufficient effects of the present invention cannot be obtained, and if it is too long, the total light transmittance of the transparent electrode 2 is reduced. If it is the 2nd transparent electrode layer 22 of this range, the preferable haze rate of the transparent electrode 2 is substantially maintained in the state which formed the 2nd transparent electrode layer 22 on the translucent insulated substrate 1, Since it has a haze ratio of about 40%, an optical confinement effect suitable for a thin film photoelectric conversion device can be obtained. Also, by forming the second transparent electrode layer 22, it is possible to prevent post-oxidation of crystal grain boundaries and other chemical changes related to the surface irregularities of the first transparent electrode layer 21 formed by using the low pressure CVD method. There is an effect that can be done.

  The average film thickness of the transparent electrode 2 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 photoelectric conversion unit 3 formed on the transparent electrode 2 may be a single photoelectric conversion unit as illustrated, but a plurality of photoelectric conversion units may be stacked. As the crystalline photoelectric conversion unit 3, one having absorption in the main wavelength range (400 to 1200 nm) of sunlight is preferable. For example, crystalline silicon photoelectric conversion using a crystalline silicon thin film as an intrinsic crystalline photoelectric conversion layer 32 is preferable. A unit. 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 crystalline photoelectric conversion layer 32 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 4 is formed on the photoelectric conversion unit 3. As the back electrode, it is preferable to form at least one metal layer 42 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 41 such as ITO, SnO ₂ , or ZnO between the photoelectric conversion unit 3 and the metal layer 42. The conductive oxide layer 41 increases the adhesion between the photoelectric conversion unit 3 and the metal layer 42, increases the light reflectance of the back electrode 4, and further prevents chemical changes in the photoelectric conversion unit layer 3. 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 transparent electrode 2. 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. 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 thin film 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).

  Needless to say, the essence of the present invention is applicable to other types of thin-film solar cells using a transparent electrode on a translucent insulating substrate. Other types of thin film photoelectric conversion devices (in one aspect, thin film solar cells) are, for example, CdTe solar cells that are II-VI group compound semiconductors, CIS solar cells that are chalcopyrite thin films, and organic semiconductors. Organic solar cells and dye-sensitized solar cells.

  That is, what is essential to the present invention can also be used in the following technical fields.

The present invention also provides
A method for manufacturing a substrate with a transparent conductive film for a photoelectric conversion device, wherein a first transparent electrode layer having surface irregularities in which zinc oxide is doped with impurities at a constant concentration is formed in order from the substrate side using a low-pressure CVD method And forming a second transparent electrode layer by increasing the amount of zinc source gas in the range of 1.2 to 3 times that of the first transparent electrode layer to form a second transparent electrode layer. The method for producing a substrate with a transparent conductive film for a photoelectric conversion device, characterized in that the time to be is in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer,
It is.

The present invention also provides
A method for manufacturing a substrate with a transparent conductive film for a photoelectric conversion device, wherein a first transparent electrode layer having surface irregularities in which zinc oxide is doped with impurities at a constant concentration is formed in order from the substrate side using a low-pressure CVD method And increasing the amount of zinc source gas to a range of 1.2 to 3 times that of the first transparent electrode layer and increasing the impurity doping amount to a range of 1.2 to 3 times the second transparent electrode layer. And a step of forming the second transparent electrode layer, wherein the time for forming the second transparent electrode layer is in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer. Manufacturing method of substrate with transparent conductive film for apparatus,
It is.

  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 transparent electrode 2 for a photoelectric conversion device 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 about 1.7 μm as the transparent electrode 2 by low-pressure CVD. The first transparent electrode layer 21 is formed by CVD using a substrate temperature of 160 ° C., supplying diethyl zinc (DEZ) and water as source gases, and diborane (B ₂ H ₆ ) gas as a dopant gas. is doing. The pressure was 20 Pa, DEZ flow rate 400 sccm, water flow rate 1000 sccm, B ₂ H ₆ flow rate ₂ sccm, argon flow rate 500 sccm, hydrogen flow rate 500 sccm. The B ₂ H ₆ flow rate was 0.5% with respect to the DEZ flow rate. The first transparent electrode layer 21 is deposited for 850 seconds, and the second transparent electrode layer is continuously formed for 50 seconds. The second transparent electrode layer 22 is different from the second transparent electrode layer 22 only in that the DEZ flow rate in the formation condition of the first transparent electrode layer 21 is doubled.

The obtained substrate with the transparent electrode 2 had a sheet resistance of about 10Ω / □ and a haze ratio of 25%. 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 80% or more was exhibited in the wavelength range of 500 to 1200 nm. When the substrate with the transparent electrode 2 formed by the above-described method was separately exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 92Ω / □ after the moisture resistance test. At this time, the B dope concentration with respect to zinc oxide in the transparent electrode layer is approximately proportional to the relationship of the flow rate ratio of B ₂ H _{6 to} DEZ during film formation. Therefore, when the flow rate ratio is changed after a certain film formation time, the B dope concentration in the transparent electrode layer also changes in proportion to the flow rate ratio.

  Note that sccm in this example is standard cc / min, which is ccm normalized at 1 atm and 0 ° C.

(Example 2)
Also in Example 2, a substrate with a transparent electrode 2 was produced in the same manner as in Example 1. However, the difference from Example 1 is that the deposition time of the second transparent electrode layer 22 is set to 100 seconds. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 9.5Ω / □ and a haze ratio of 28%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 80Ω / □ after the moisture resistance test. When the variation rate of the sheet resistance was compared with the substrate of Example 1, the improvement was observed by increasing the formation time of the second transparent electrode layer 22.

(Example 3)
Also in Example 3, a substrate with a transparent electrode 2 was produced in the same manner as in Example 2. However, the difference from Example 2 is that when the second transparent electrode layer 22 was formed, the B ₂ H ₆ flow rate was changed to double at the same time as the DEZ flow rate. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 9.3Ω / □ and a haze ratio of 23%. Further, when the obtained substrate with transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 45Ω / □ after the moisture resistance test. When the variation rate of the sheet resistance and the substrate of Example 2 was compared, further improvement was seen by increasing the B ₂ H ₆ flow rate during the formation of the second transparent electrode layer 22.

Example 4
Also in Example 4, a substrate with a transparent electrode 2 was produced in the same manner as in Example 2. However, the difference from Example 2 is that the temperature at the time of forming the second transparent electrode layer 22 was changed to 165 ° C. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 10.5Ω / □ and a haze ratio of 28%. Further, when the obtained substrate with transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 45Ω / □ after the moisture resistance test. When the variation rate of the sheet resistance and the substrate of Example 2 were compared, improvement was seen by increasing the formation temperature of the second transparent electrode layer 22.

(Example 5)
Also in Example 5, a substrate with a transparent electrode 2 was produced in the same manner as in Example 2. However, the difference from Example 2 is that the temperature at the time of forming the second transparent electrode layer 22 was changed to 170 ° C., and the formation time of the first transparent electrode layer 21 was changed to 750 seconds. Since the film formation speed of the transparent electrode 2 depends on the substrate temperature, the film formation time was adjusted simultaneously with the change of the film formation temperature. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 10Ω / □ and a haze ratio of 25%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 33Ω / □ after the moisture resistance test. When the variation rate of the sheet resistance was compared with the substrates of Example 2 and Example 4, the improvement was observed by increasing the formation temperature of the second transparent electrode layer 22.

(Example 6)
In Example 6, a substrate with a transparent electrode 2 was produced in the same manner as in Example 5. However, the difference from Example 5 is that when the second transparent electrode layer 22 was formed, the B ₂ H ₆ flow rate was changed to double simultaneously with the DEZ flow rate. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 9.5Ω / □ and a haze ratio of 21%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 21Ω / □ after the moisture resistance test. When the variation rate of the sheet resistance and the substrate of Example 5 was compared, further improvement was seen by increasing the B ₂ H ₆ flow rate during the formation of the second transparent electrode layer 22.

(Comparative Example 1)
In Comparative Example 1, a substrate with a transparent electrode 2 was produced in substantially the same manner as in Example 1. However, the difference from Example 1 is that the second transparent electrode layer 22 is not formed, and the formation time of the first transparent electrode layer 21 is the same as the formation of the first transparent electrode layer 21 and the second transparent electrode layer 22 in Example 1. The point equal to the total time. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 12Ω / □ and a haze ratio of 28%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in an atmosphere of 85 ° C. and 85% humidity, the sheet resistance increased to 180Ω / □ after the moisture resistance test.

(Comparative Example 2)
In Comparative Example 2, a substrate with a transparent electrode 2 was produced by simulating Example 1 of Patent Document 1. The difference from the comparative example 1 is that the substrate temperature at the initial film formation of the first transparent electrode layer 21 is set to 170 ° C., about 200 nm is formed, and the substrate temperature is set to 160 ° C. Similar to Comparative Example 1, the second transparent electrode layer 22 is not formed. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 13Ω / □ and a haze ratio of 27%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 120Ω / □ after the moisture resistance test.

(Comparative Example 3)
In Comparative Example 3, a substrate with a transparent electrode 2 was produced in substantially the same manner as Comparative Example 1. However, the difference from Comparative Example 1 is that the formation time of the first and second transparent electrode layers was set to 170 ° C., and the formation time was adjusted so that the film thickness was about 1.7 μm. The substrate with the transparent electrode 2 obtained under these conditions had a sheet resistance of about 14Ω / □ and a haze ratio of 28%. Further, when the obtained substrate with the transparent electrode 2 was exposed for 24 hours in a humidity atmosphere of 85 ° C. and 85%, the sheet resistance increased to 82Ω / □ after the moisture resistance test.

  Table 1 summarizes the main formation conditions of the transparent electrode 2 according to the above-described Examples 1 to 6 and Comparative Examples 1 to 3, and the results of sheet resistance fluctuation before and after the moisture resistance test of each transparent electrode 2.

As can be seen from the results in Table 1, in any of Examples 1 to 6, it was found from the comparison with Comparative Example 1 that the variation in sheet resistance can be suppressed. It can also be seen that increasing the B ₂ H ₆ flow rate simultaneously with the DEZ flow rate is more effective in suppressing resistance fluctuations than increasing only the DEZ flow rate. It can also be seen that the method is more effective in suppressing resistance fluctuations when compared at the same formation temperature.

  Then, the characteristic evaluation of the thin film photoelectric conversion apparatus 5 was performed using the some board | substrate with the transparent electrode 2 obtained by the said Example and comparative example.

(Example 7)
In Example 7, the following thin film photoelectric conversion device 5 was formed using the substrate with the transparent electrode 2 obtained in Example 2 above.

  On the second transparent electrode layer 22, a p-type microcrystalline silicon layer 31 with a thickness of 15 nm, an intrinsic crystalline silicon photoelectric conversion layer 32 with a thickness of 1.5 μm, and an n-type microcrystalline silicon layer 33 with a thickness of 15 nm. The resulting crystalline silicon photoelectric conversion units 3 were sequentially formed by the plasma CVD method. Thereafter, Al-doped ZnO 41 having a thickness of 90 nm and Ag 42 having a thickness of 200 nm were sequentially formed as the back electrode 4 by sputtering.

When the photoelectric conversion device 5 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 0.550 V and the short-circuit current density (Jsc). ) Was 25.0 mA / cm ² , the fill factor (FF) was 0.730, and the conversion efficiency was 10.0%.

(Example 8)
In Example 8, the thin film photoelectric conversion device 5 was formed in the same manner as in Example 7 using the substrate with the transparent electrode 2 obtained in Example 5 above.

When the output characteristics were measured by irradiating the obtained photoelectric conversion device 5 with AM1.5 light at 100 mW / cm ² light amount, the open circuit voltage (Voc) was 0.548 V, and the short-circuit current density (Jsc) was 25.2 mA. / Cm ² , fill factor (FF) was 0.723, and conversion efficiency was 10.0%.

(Comparative Example 4)
In Comparative Example 4, the thin film photoelectric conversion device 5 was formed in the same manner as in Example 7 using the substrate with the transparent electrode 2 obtained in Comparative Example 1 above.

When the output characteristics were measured by irradiating the obtained photoelectric conversion device 5 with AM 1.5 light at 100 mW / cm ² light amount, the open circuit voltage (Voc) was 0.521 V, and the short-circuit current density (Jsc) was 24.6 mA. / Cm ² , fill factor (FF) was 0.701, and conversion efficiency was 9.0%.

(Comparative Example 5)
In Comparative Example 5, the thin film photoelectric conversion device 5 was formed in the same manner as in Example 7 using the substrate with the transparent electrode 2 obtained in Comparative Example 3.

When the output characteristics were measured by irradiating the obtained photoelectric conversion device 5 with AM 1.5 light at 100 mW / cm ² light amount, the open circuit voltage (Voc) was 0.496 V, and the short circuit current density (Jsc) was 23.2 mA. / Cm ² , fill factor (FF) was 0.680, and conversion efficiency was 7.8%.

  Table 2 summarizes the measurement results of the thin film photoelectric conversion devices 5 of Examples 7 to 8 and Comparative Examples 4 to 5 described above.

  As can be seen from the results in Table 2, in any of the examples, a photoelectric conversion device having a conversion efficiency exceeding the comparative example was obtained. From the results of Example 7 and Comparative Example 4, by forming the second transparent electrode layer 22, Voc and F.R. F. It can be seen that the bonding state between the transparent electrode and the conductive type layer is improved. Further, from the results of Example 8 and Comparative Example 5, in addition to the large influence of the formation temperature of the transparent electrode on the transparent conductive film characteristics, the influence on the photoelectric conversion characteristics is also large. By using this production method, It turns out that the board | substrate with the transparent electrode 2 suitable for a thin film photoelectric conversion apparatus can be provided stably.

  As described above in detail, according to the present invention, it is possible to provide a transparent conductive film for a photoelectric conversion device having an effective surface concavity and convexity and an excellent light confinement effect by an inexpensive manufacturing method. it can.

Sectional drawing of the thin film photoelectric conversion apparatus using the transparent conductive film for photoelectric conversion apparatuses which is one Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent insulated substrate 2 Transparent electrode 21 1st transparent electrode layer 22 2nd transparent electrode layer 3 Photoelectric conversion unit 31 One conductivity type layer 32 Intrinsic photoelectric conversion layer 33 Reverse conductivity type layer 4 Back surface electrode 41 Conductive oxide layer 42 Metal layer 5 Photoelectric conversion device

Claims (2)

  A method for manufacturing a substrate with a transparent conductive film for a photoelectric conversion device, wherein a first transparent electrode layer having surface irregularities in which zinc oxide is doped with impurities at a constant concentration is formed in order from the substrate side using a low-pressure CVD method And forming a second transparent electrode layer by increasing the amount of zinc source gas in the range of 1.2 to 3 times that of the first transparent electrode layer to form a second transparent electrode layer. The manufacturing time of the board | substrate with a transparent conductive film for photoelectric conversion apparatuses characterized by the time to perform being the range of 1 / 25-1 / 5 of the time which forms this 1st transparent electrode layer.   A method for manufacturing a substrate with a transparent conductive film for a photoelectric conversion device, wherein a first transparent electrode layer having surface irregularities in which zinc oxide is doped with impurities at a constant concentration is formed in order from the substrate side using a low-pressure CVD method And increasing the amount of zinc source gas to a range of 1.2 to 3 times that of the first transparent electrode layer and increasing the impurity doping amount to a range of 1.2 to 3 times the second transparent electrode layer. And a step of forming the second transparent electrode layer, wherein the time for forming the second transparent electrode layer is in the range of 1/25 to 1/5 of the time for forming the first transparent electrode layer. The manufacturing method of the board | substrate with a transparent conductive film for apparatuses.

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