JP2013138138A - Method for manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve photoelectric conversion efficiency.SOLUTION: A method for manufacturing a photoelectric conversion element including a transparent conductive film and a photoelectric conversion layer comprises the steps of: subjecting the transparent conductive film to plasma treatment using a gas containing carbon dioxide; and forming the photoelectric conversion layer on the transparent conductive film. The gas containing carbon dioxide may be a mixture of carbon dioxide and hydrogen or a mixture of carbon dioxide and an inert gas.

Description

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

  A photoelectric conversion element made of amorphous silicon (hereinafter sometimes referred to as “a-Si photoelectric conversion element”) can be thinned, can be manufactured by a low-temperature process, or has a large area glass substrate or Due to the fact that it can be easily formed on a stainless steel substrate, development is underway as a favorite of low-cost solar cells.

  Such an a-Si photoelectric conversion element is generally configured by laminating a transparent conductive film, a photoelectric conversion unit having one or more pin junctions, and a back electrode layer on the upper surface of a transparent insulating substrate. Yes. Here, the photoelectric conversion unit is generally formed by stacking a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer in this order or vice versa. An i-type semiconductor layer that occupies the main part of the photoelectric conversion unit is called an amorphous photoelectric conversion unit, and an i-type semiconductor layer is called a crystalline photoelectric conversion unit.

  Most of the thickness of the photoelectric conversion unit in the a-Si photoelectric conversion element is occupied by the i-type semiconductor layer which is a substantially intrinsic semiconductor layer. The photoelectric conversion action mainly occurs in this i-type semiconductor layer. Therefore, it is preferable that the i-type semiconductor layer, which is a photoelectric conversion layer, is thicker for light absorption. However, when the film thickness becomes larger than necessary, it takes time to deposit the i-type semiconductor layer. In addition, when the i-type semiconductor layer is amorphous, photodegradation (Staebler-Wronsky effect) becomes prominent, and the characteristics of the photoelectric conversion element tend to deteriorate.

  As described above, the a-Si photoelectric conversion element has the above-described advantages, but since the conversion efficiency of the a-Si photoelectric conversion element is lower than that of the crystalline silicon solar cell, further improvement in conversion efficiency is an urgent need. It has become. As one of the attempts, improvement of characteristics of the transparent conductive film and improvement of the conversion efficiency of the solar cell by producing a thin film of about several nm on the transparent conductive film are known.

  Specifically, Patent Document 1 describes that a transparent conductive film made of zinc oxide is subjected to hydrogen plasma treatment, and this hydrogen plasma treatment reduces the low efficiency of the transparent conductive film, and this hydrogen plasma. It is described that the conversion efficiency of the photoelectric conversion device is improved because the film quality of the transparent conductive film is improved by the treatment.

JP 2008-283075 A

Further improvement in photoelectric conversion efficiency is desired for the photoelectric conversion element.
This invention is made | formed in view of this point, The objective is to provide the manufacturing method of the photoelectric conversion element excellent in photoelectric conversion efficiency.

  The manufacturing method of the photoelectric conversion element which concerns on this invention comprises the process of plasma-processing a transparent conductive film using the gas containing a carbon dioxide, and the process of forming a photoelectric converting layer on a transparent conductive film.

  In the method for producing a photoelectric conversion element according to the present invention, a photoelectric conversion element excellent in photoelectric conversion efficiency can be obtained.

It is a schematic sectional drawing of the photoelectric conversion element which concerns on one Embodiment of this invention. It is a flowchart which shows the principal part of the manufacturing method of the photoelectric conversion element which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the photoelectric conversion element which concerns on another embodiment of this invention. It is a flowchart which shows the principal part of the manufacturing method of the photoelectric conversion element which concerns on another embodiment of this invention.

  Hereinafter, the manufacturing method of the photoelectric conversion element concerning this invention is demonstrated using drawing. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<First Embodiment>
<Method for producing photoelectric conversion element>
FIG. 1 is a cross-sectional view of the photoelectric conversion element according to the first embodiment. FIG. 2 is a flowchart showing the main part of the method for manufacturing a photoelectric conversion element according to this embodiment. The method for manufacturing a photoelectric conversion element according to this embodiment is a method for manufacturing a photoelectric conversion element in which a photoelectric conversion layer is formed on a transparent conductive film 2 as shown in FIG. The process S12 which plasma-processes, and the process S13 which forms a photoelectric converting layer on the transparent conductive film 2 are provided. The method for manufacturing a photoelectric conversion element according to this embodiment preferably further includes a preparation step S11 of the transparent conductive film 2, and a formation step (not shown) of the first conductive film 6 and the second conductive film 7. Is preferably further provided. Note that the photoelectric conversion layer in the present embodiment is configured such that the p-type semiconductor layer 3, the i-type semiconductor layer 4, and the n-type semiconductor layer 5 are sequentially stacked on the first surface 2a of the transparent conductive film 2. Unit A.

<Preparation of transparent conductive film>
The preparation process S11 for the transparent conductive film 2 is not particularly limited. For example, the transparent conductive film 2 may be formed on the upper surface of the translucent substrate 1 by CVD, sputtering, vapor deposition, or the like, or the transparent conductive film 2 is previously formed on the upper surface of the translucent substrate 1. A substrate may be prepared.

  Here, the translucent board | substrate 1 means the board | substrate which can permeate | transmit sunlight, for example, is a glass plate. Therefore, sunlight passes through the translucent substrate 1 and enters the photoelectric conversion unit A, and the manufactured photoelectric conversion element is arranged so that the translucent substrate 1 faces outward (incident side). . Therefore, a photoelectric conversion element excellent in weather resistance can be obtained.

  Although the thickness of the translucent board | substrate 1 is not specifically limited, It is preferable that they are 0.7 mm or more and 6 mm or less. Thereby, the light which permeate | transmitted the translucent board | substrate 1 injects into the photoelectric conversion unit A, causing almost no fall of intensity | strength.

The transparent conductive film 2 is preferably made of a material capable of transmitting incident light (sunlight) of 80% or more, preferably 90% or more, and includes a conductive metal oxide such as tin oxide (SnO ₂ ) or ZnO. It is preferable that it is made of a conductive metal oxide such as tin oxide (SnO ₂ ) or ZnO. The surface of the transparent conductive film 2 may be a smooth surface, but preferably has irregularities. Thereby, the effect of increasing the scattering of incident light is obtained. The film thickness of the transparent conductive film 2 is not particularly limited, but is preferably 500 nm or more and 2500 nm or less.

<Plasma treatment for transparent conductive film>
The transparent conductive film 2 is plasma-treated using a gas containing carbon dioxide. Here, the plasma treatment of the transparent conductive film 2 using a gas containing carbon dioxide is generated by using collision ionization between an electron accelerated by an electric field by a high-frequency voltage or a microwave and a gas containing carbon dioxide. It means that the first surface 2a of the transparent conductive film 2 is irradiated with plasma. Moreover, the 1st surface 2a of the transparent conductive film 2 is the surface of the transparent conductive film 2 which will be located in the opposite side to the light-incidence side among the surfaces of the transparent conductive film 2, and the following <formation of a photoelectric conversion unit > Is the surface of the transparent conductive film 2 on which the photoelectric conversion unit A is formed.

  As a result of intensive studies, the present inventors have found that if the transparent conductive film 2 is plasma-treated using a gas containing carbon dioxide, the photoelectric conversion efficiency is improved.

The reason why the photoelectric conversion efficiency is improved by plasma treatment of the transparent conductive film 2 using a gas containing carbon dioxide is considered to be, for example, the following two reasons. First reason: a gas containing carbon dioxide This is because the carbon-based thin film (this thin film generally has a low refractive index) is formed on the first surface of the transparent conductive film, so that the light transmittance is improved. Second reason: This is because, since the surface is dry-etched, unevenness is formed on the first surface of the transparent conductive film, or the uneven structure on the first surface of the transparent conductive film is changed, thereby increasing the scattering of incident light.

  The present inventors perform plasma treatment using a gas containing carbon dioxide, and then use a time-of-flight secondary ion mass spectrometer (TOF-SIMS) to conduct transparent conduction. When chemical information of atoms or molecules in the vicinity of about 10 nm in the depth direction from the surface of the film 2 was measured, no deposit (formation of a thin film) on the surface of the transparent conductive film 2 was confirmed. From this, the reason why the photoelectric conversion efficiency is improved by plasma-treating the transparent conductive film 2 using a gas containing carbon dioxide is not the reason for the change in the chemical composition of the transparent conductive film 2 but the transparent conductive film 2. The reason that the shape of the transparent conductive film 2 changes, such as unevenness being formed on the surface, is conceivable.

The gas containing carbon dioxide may consist of carbon dioxide alone or a mixed gas of carbon dioxide and a gas other than carbon dioxide. In other words, it is preferable to satisfy the following formula 1 or the following formula 2. 0.74 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of hydrogen) ≦ 1.0: formula 1
0.05 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of inert gas) ≦ 1.0: Formula 2.

  In Equation 1, if 0.74> {volume of carbon dioxide / (volume of carbon dioxide + volume of hydrogen)}, the reduction of the transparent conductive film with hydrogen becomes excessive, and thus the transmittance of the transparent conductive film layer and Causes a decrease in conductivity. Therefore, the conversion efficiency may be reduced. Preferably, 0.85 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of hydrogen) ≦ 1.0.

  In Formula 2, if 0.05> {volume of carbon dioxide / (volume of carbon dioxide + volume of inert gas)}, the surface treatment effect by plasma may not be sufficiently obtained. Here, the inert gas means a gas that does not cause a chemical reaction with both the transparent conductive film and carbon dioxide, and examples thereof include rare gases such as argon gas, helium, neon, krypton, and xenon. Preferably, 0.3 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of inert gas) ≦ 1.0.

The plasma treatment conditions for the transparent conductive film are not particularly limited, but the following conditions are preferable. Flow rate of gas containing carbon dioxide: 40 sccm (Standard Cubic Centimeter per Minutes) or more and 1000 sccm or less Flow rate of carbon dioxide among the above gases : 30 sccm or more and 300 sccm or less Temperature of translucent substrate 1: 50 ° C or more and 400 ° C or less Pressure in CVD apparatus: 7 Pa or more and 800 Pa or less Shape of high frequency electrode: Flat plate electrode arranged parallel to each other Frequency of high frequency power source: 10 MHz or more and 150 MHz Or less, or 0.2 GHz to 1000 GHz (microwave level frequency)
Power density of the high frequency power source: 0.01 W / cm ² or more and 0.5 W / cm ² or less.

  Although the timing which complete | finishes the plasma processing with respect to the transparent conductive film 2 is not specifically limited, For example, it is preferable to stop the plasma processing with respect to the transparent conductive film 2 30 seconds after plasma emission is confirmed.

Since carbon dioxide is used in this plasma treatment, it is preferable to select a material that does not easily react with carbon dioxide as the material of the transparent conductive film 2. If a conductive metal oxide such as SnO ₂ or ZnO is selected as the material of the transparent conductive film 2, the reaction between the transparent conductive film 2 and carbon dioxide can be suppressed.

<Formation of photoelectric conversion unit>
Subsequently, the photoelectric conversion unit A is formed on the transparent conductive film 2. Specifically, the p-type semiconductor layer 3, the i-type semiconductor layer 4, and the n-type semiconductor layer 5 are sequentially stacked on the first surface 2 a of the transparent conductive film 2.

-Formation of p-type semiconductor layer-
A p-type semiconductor layer 3 is formed on the first surface 2 a of the transparent conductive film 2. The method for forming the p-type semiconductor layer 3 is not particularly limited, and a CVD method or a plasma CVD method is preferable.

  The material of the p-type semiconductor layer 3 is not particularly limited. The p-type semiconductor layer 3 serves to generate a diffusion potential in the photoelectric conversion unit A, and the value of the open end voltage Voc, which is one of important characteristics of the thin photoelectric conversion device, is influenced by the magnitude of the diffusion potential. The Therefore, it is preferable to set the material of the p-type semiconductor layer 3 so that the photoelectric conversion unit A has a built-in potential. It is preferable to appropriately set the material of the source gas used to manufacture the p-type semiconductor layer 3 according to the material of the p-type semiconductor layer 3.

  For example, when the p-type semiconductor layer 3 made of amorphous silicon or microcrystalline silicon is formed, a chain or cyclic silane compound and a compound that becomes a p-type impurity material are used as the source gas. Is preferred. When the p-type semiconductor layer 3 made of an amorphous silicon alloy or a microcrystalline silicon alloy is formed, the source gas includes a chain or cyclic silane compound, a compound serving as a p-type impurity material, It is preferable to use a compound containing carbon, oxygen, nitrogen, or germanium.

  Here, the microcrystalline silicon is composed of fine crystalline silicon having a crystal having a size of the nm level, and may mean that part of which includes amorphous silicon. Μc-Si May be written. An amorphous silicon alloy means amorphous silicon containing elements such as carbon, oxygen, nitrogen, and germanium, and the content of elements such as carbon, oxygen, nitrogen, and germanium with respect to amorphous silicon is For example, it is preferably 5% by mass or more and 30% by mass or less. The microcrystalline silicon alloy means microcrystalline silicon containing elements such as carbon, oxygen, nitrogen, and germanium. The content of elements such as carbon, oxygen, nitrogen, and germanium in the microcrystalline silicon is 2% by mass. It is preferable that it is 20 mass% or less.

  The supply amount of the chain or cyclic silane compound is preferably set as appropriate according to the film thickness of the p-type semiconductor layer 3 to be formed. Here, the film thickness of the p-type semiconductor layer 3 is not particularly limited. However, the p-type semiconductor layer 3 is an inactive layer that hardly contributes to photoelectric conversion, and light absorbed by impurities doped in the p-type semiconductor layer 3 hardly contributes to power generation and is lost. For these reasons, the thickness of the p-type semiconductor layer 3 is preferably as thin as possible within a range in which a sufficient diffusion potential is generated, and is preferably 6 nm or more and 50 nm or less, for example. Therefore, the supply amount of the chain or cyclic silane compound is preferably, for example, 2 sccm or more and 300 sccm or less.

Examples of the chain or cyclic silane compound include SiH ₄ , Si ₂ H ₆ , SiF ₄ , SiFH ₃ , SiF ₂ H ₂ , SiF ₃ H, Si ₃ H ₈ , SiD ₄ , SiHD ₃ , SiH ₂ D ₂ , SiH ₃ D, SiFD ₃ , SiF ₂ D ₂ , Si ₂ D ₃ H ₃ , (SiF ₂ ) ₅ , (SiF ₂ ) ₆ , (SiF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , Si ₂ H ₂ F ₄ , Si ₂ H ₃ F ₃ , SiCl ₄ , (SiCl ₂ ) ₅ , SiBr ₄ , (SiBr ₂ ) ₅ , Si ₂ Cl ₆ , SiHCl ₃ , SiH ₂ Br ₂ , SiH ₂ Cl ₂ , and Si ₂ At least one such as Cl ₃ F ₃ can be used.

When boron is selected as the p-type impurity, the compounds used as the material for the p-type impurity include B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H ₁₁ , B ₆ H ₁₀ , B _6. Boron hydrides such as H ₁₂ and B ₆ H ₁₄ may be used, and boron halides such as BF ₃ and BCl ₃ may be used. Among these, B ₂ H ₆ or BF ₃ is preferable. The p-type impurity is not limited to boron, and may be Mg. The addition amount of the compound serving as the material of the p-type impurity is appropriately set so that the p-type impurity concentration in the p-type semiconductor layer 3 is, for example, 1 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. Is preferred.

Examples of the compound containing carbon include CH ₄ , CD ₄ , C _n H _{2n + 2} (n is an integer), C _n H _2n (n is an integer), C ₂ H ₂ , C ₆ H ₆ , CO ₂ , CO, At least one of Si (CH ₃ ) H ₃ , Si (CH ₃ ) ₂ H ₂ , and Si (CH ₃ ) ₃ H can be used. Thereby, an amorphous silicon layer containing carbon or a microcrystalline silicon layer containing carbon is formed. It is preferable to appropriately set the addition amount of the compound containing carbon so that the carbon concentration in the p-type semiconductor layer 3 becomes a predetermined value. This can be said also about each addition amount of the compound containing oxygen, the compound containing nitrogen, and the compound containing germanium.

As the compound containing oxygen, at least one of O ₂ , CO, CO ₂ , NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH, and H ₂ O can be used. Thus, an amorphous silicon layer containing oxygen or a microcrystalline silicon layer containing oxygen is formed.

As the compound containing nitrogen, at least one of N ₂ , NH ₃ , ND ₃ , NO, NO ₂ , and N ₂ O can be used. Thus, an amorphous silicon layer containing nitrogen or a microcrystalline silicon layer containing nitrogen is formed.

The compounds containing germanium include GeH ₄ , GeD ₄ , GeF ₄ , GeFH ₃ , GeF ₂ H ₂ , GeF ₃ H, GeHD ₃ , GeH ₂ D ₂ , GeH ₃ D, Ge ₂ H ₆ , and Ge ₂ D _6. At least one of the above can be used. Thereby, an amorphous silicon layer containing germanium or a microcrystalline silicon layer containing germanium is formed.

When the p-type semiconductor layer 3 is formed by the plasma CVD method, the generation conditions of the high-frequency plasma are not particularly limited, but the following conditions are preferable. Temperature of the light-transmitting substrate 1: 100 ° C. or more and 300 ° C. or less CVD apparatus Pressure in the inside: 30 Pa or more and 1500 Pa or less Shape of the high frequency electrode: Flat plate electrode arranged in parallel to each other Frequency of the high frequency power source: 10 MHz or more and 100 MHz or less Power density of the high frequency power source: 0.01 W / cm ² or more and 0.5 W / cm ² or less .

In addition to the source gas, a gas such as H ₂ , He, Ne, Ar, Xe, or Kr may be supplied as a carrier gas into the chamber of the CVD apparatus. This can also be said when the i-type semiconductor layer 4 is formed and when the n-type semiconductor layer 5 is formed.

In addition, the volume ratio of SiH ₄ gas to H ₂ gas is 1 volume% to 40 volume%, the pressure in the CVD apparatus is 30 Pa to 800 Pa, and the power density of the high-frequency power source is 0.02 W / cm ^{2 to} 0.3 W / If the cm ² or less and the temperature of the light-transmitting substrate 1 are 100 ° C. or more and 250 ° C. or less, the amorphous p-type semiconductor layer 3 is formed. On the other hand, the volume ratio of SiH ₄ gas to H ₂ gas is 30 volume% to 400 volume%, the pressure in the CVD apparatus is 30 Pa to 1300 Pa, and the power density of the high-frequency power source is 0.02 W / cm ^{2 to} 0.3 W / If the temperature of cm ² or less and the temperature of the translucent substrate 1 are 100 ° C. or more and 250 ° C. or less, the microcrystalline p-type semiconductor layer 3 is formed.

-Formation of i-type semiconductor layer-
An i-type semiconductor layer 4 is formed on the p-type semiconductor layer 3. The method for forming i-type semiconductor layer 4 is not particularly limited, and a CVD method or a plasma CVD method is preferable.

The material of the i-type semiconductor layer 4 is not particularly limited. The i-type semiconductor layer 4 may be an amorphous semiconductor layer or a crystalline semiconductor layer. As the amorphous semiconductor layer, an amorphous silicon layer or an amorphous silicon alloy layer can be used, but a hydrogenated amorphous silicon layer containing 5 to 20 atomic% of hydrogen in the amorphous semiconductor layer or It is preferable to use a hydrogenated amorphous silicon alloy layer. In an amorphous silicon layer or an amorphous silicon alloy layer that does not contain hydrogen, the defect density derived from dangling bonds (dangling bonds) is as high as 10 ¹⁹ to 10 ²⁰ cm ^−3. It is difficult to use a porous silicon layer or an amorphous silicon alloy layer for a semiconductor device such as a photoelectric conversion element. On the other hand, in the hydrogenated amorphous silicon layer and the hydrogenated amorphous silicon alloy layer, since hydrogen terminates dangling bonds, the defect density is reduced to 10 ¹⁵ to 10 ¹⁷ cm ⁻³ . Therefore, the hydrogenated amorphous silicon layer and the hydrogenated amorphous silicon alloy layer can be used for a semiconductor device such as a photoelectric conversion element. Here, the hydrogenated amorphous silicon alloy layer means a hydrogenated amorphous silicon layer containing elements such as carbon, oxygen, nitrogen, and germanium.

  As the crystalline semiconductor layer, a microcrystalline silicon layer, a microcrystalline silicon alloy layer, or the like can be used, but a hydrogenated microcrystalline silicon layer or a hydrogenated microcrystalline silicon alloy layer is preferably used for the above reasons. The hydrogenated microcrystalline silicon alloy layer means a hydrogenated microcrystalline silicon layer containing elements such as carbon, oxygen, nitrogen, and germanium. Hydrogenation means containing 5 to 20 atomic% of hydrogen in the layer as described above.

The i-type semiconductor layer 4 is a semiconductor layer that contributes to photoelectric conversion, and ideally is an intrinsic semiconductor layer that does not contain impurities that determine the conductivity type. However, even if the semiconductor layer contains a small amount of the impurity, if the Fermi level of the semiconductor layer is approximately at the center of the forbidden band, the semiconductor layer functions as a pin junction i-type semiconductor layer. Therefore, the i-type semiconductor layer 4 in this specification includes not only an intrinsic semiconductor layer that does not include an impurity that determines a conductivity type but also a Fermi level that has a forbidden band although it includes a small amount of impurity. A semiconductor layer in the center is also included. Here, containing a trace amount of impurities means containing impurities of, for example, 1 × 10 ¹⁴ cm ⁻³ or more and 1 × 10 ¹⁸ cm ⁻³ or less. When the i-type semiconductor layer 4 containing a small amount of impurities is formed by the CVD method, the i-type semiconductor layer 4 may be formed without adding a dopant gas serving as an impurity for determining the conductivity type to the source gas. The i-type semiconductor layer 4 may be formed by adding the above impurities within an allowable range that functions as an i-type semiconductor layer, or in order to remove the influence of impurities caused by the atmosphere or the underlayer on the Fermi level. The i-type semiconductor layer 4 may be formed by intentionally adding the dopant gas.

  In consideration of the above, it is preferable to set the material of the i-type semiconductor layer 4 and appropriately determine the source gas according to the set material of the i-type semiconductor layer 4. For example, when an i-type semiconductor layer made of hydrogenated amorphous silicon or hydrogenated microcrystalline silicon is formed, it is preferable to use a chain or cyclic silane compound and hydrogen gas as the source gas. When forming the i-type semiconductor layer 4 made of a hydrogenated amorphous silicon alloy or a hydrogenated microcrystalline silicon alloy, the raw material gas includes a chain or cyclic silane compound, hydrogen gas, carbon, oxygen, It is preferable to use a compound containing either nitrogen or germanium.

  The supply amount of the chain or cyclic silane compound is preferably set as appropriate according to the film thickness of the i-type semiconductor layer 4 to be formed, and is preferably 2 sccm or more and 200 sccm or less, for example. The amount of hydrogen gas added to the chain or cyclic silane compound is preferably set as appropriate so that the hydrogen content in the i-type semiconductor layer 4 is 5 to 20 atomic%. The addition amount of the compound containing carbon or the like to the chain or cyclic silane compound is also preferably set as appropriate.

  As the chain or cyclic silane compound, the compound containing carbon, the compound containing oxygen, the compound containing nitrogen, and the compound containing germanium, it is preferable to use the compounds listed in the above-mentioned “p-type semiconductor layer formation”.

  When the i-type semiconductor layer 4 is formed by the plasma CVD method, the generation conditions of the high-frequency plasma are not particularly limited, but the conditions listed in the above-mentioned -p-type semiconductor layer formation- are preferable.

  The conditions for separately forming the amorphous i-type semiconductor layer 4 and the microcrystalline i-type semiconductor layer 4 are as described in the above-formation of the p-type semiconductor layer.

-Formation of n-type semiconductor layer-
An n-type semiconductor layer 5 is formed on the i-type semiconductor layer 4. The method for forming the n-type semiconductor layer 5 is not particularly limited, and a CVD method or a plasma CVD method is preferable.

  The material of the n-type semiconductor layer 5 is not particularly limited. The n-type semiconductor layer 5 plays the role of generating a diffusion potential in the photoelectric conversion unit A, like the p-type semiconductor layer 3, and the open end, which is one of the important characteristics of the thin photoelectric conversion device, depending on the magnitude of the diffusion potential. The value of the voltage Voc is influenced. Therefore, it is preferable to set the material of the n-type semiconductor layer 5 so that the photoelectric conversion unit A has a built-in potential. For example, when p-type semiconductor layer 3 is made of amorphous silicon carbide, n-type semiconductor layer 5 is preferably made of microcrystalline silicon. It is preferable to appropriately determine the source gas according to the material of the n-type semiconductor layer 5.

  For example, when the n-type semiconductor layer 5 made of amorphous silicon or microcrystalline silicon is formed, a chain or cyclic silane compound and a compound serving as an n-type impurity material are used as the source gas. Is preferred. Further, when forming the n-type semiconductor layer 5 made of an amorphous silicon alloy or a microcrystalline silicon alloy, the raw material gas includes a chain or cyclic silane compound, a compound that becomes a material of an n-type impurity, It is preferable to use a compound containing carbon, oxygen, nitrogen, or germanium.

  The supply amount of the chain or cyclic silane compound is preferably set as appropriate according to the film thickness of the n-type semiconductor layer 5 to be formed. Here, the thickness of the n-type semiconductor layer 5 is not particularly limited. However, the n-type semiconductor layer 5 is an inactive layer that hardly contributes to photoelectric conversion, and light absorbed by impurities doped in the n-type semiconductor layer 5 hardly contributes to power generation and is lost. For these reasons, the film thickness of the n-type semiconductor layer 5 is preferably as thin as possible within a range in which a sufficient diffusion potential is generated. Therefore, the supply amount of the chain or cyclic silane compound is preferably, for example, 2 sccm or more and 300 sccm or less. The addition amount of the compound containing carbon or the like to the chain or cyclic silane compound is also preferably set as appropriate.

  As the chain or cyclic silane compound, the compound containing carbon, the compound containing oxygen, the compound containing nitrogen, and the compound containing germanium, it is preferable to use the compounds listed in the above-mentioned “p-type semiconductor layer formation”.

When phosphorus is selected as the n-type impurity, phosphorus ₃ hydride such as PH ₃ or P ₂ H ₄ may be used as the n-type impurity material, or PH ₄ I, PF ₃ , Phosphorus halides such as PF ₅ , PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , or PI ₃ may be used. Among these, PH ₃ or PF ₃ is preferable. The n-type impurity is not limited to P, and may be Si, As, or Sb. The addition amount of the compound serving as the material of the n-type impurity is appropriately set so that the n-type impurity concentration in the n-type semiconductor layer 5 is, for example, 1 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. Is preferred.

  In the case where the n-type semiconductor layer 5 is formed by the plasma CVD method, the generation conditions of the high-frequency plasma are not particularly limited, but the conditions listed in the above-mentioned “formation of the p-type semiconductor layer” are preferable.

  The conditions for making the amorphous n-type semiconductor layer 5 and the microcrystalline n-type semiconductor layer 5 as described above are as described in the above-formation of p-type semiconductor layer.

<Formation of first conductive film and second conductive film>
For example, the first conductive film 6 and the second conductive film 7 are preferably formed on the n-type semiconductor layer 5 by sputtering or vapor deposition.

The first conductive film 6 is preferably made of a material that can transmit sunlight, and is preferably made of a conductive oxide such as ITO (Indium Tin Oxide), SnO _2, or ZnO. The film thickness of the 1st electrically conductive film 6 is not specifically limited, It is preferable that they are 20 nm or more and 150 nm or less.

  The second conductive film 7 is preferably made of a conductive material, and is preferably made of at least one material of Al, Ag, Au, Cu, Pt, Cr, Ti, Zn, and Mo. The film thickness of the 2nd electrically conductive film 7 is not specifically limited, It is preferable that it is 50 nm or more.

  As shown in FIG. 1, the photoelectric conversion element thus obtained has a transparent conductive film 2, a photoelectric conversion unit A, a first conductive film 6, and a second conductive film on a translucent substrate 1. 7 are laminated in order. The photoelectric conversion unit A is provided on the first surface 2a of the transparent conductive film 2, and the p-type semiconductor layer 3, the i-type semiconductor layer 4, and the n-type semiconductor layer 5 are sequentially stacked on the first surface 2a. Configured.

<Second Embodiment>
In the method for manufacturing a photoelectric conversion element according to the second embodiment, a photoelectric conversion element including two photoelectric conversion units is manufactured. Hereinafter, points different from the first embodiment will be mainly described.

  FIG. 3 is a schematic cross-sectional view of the photoelectric conversion element according to this embodiment. FIG. 4 is a flowchart showing the main part of the method for manufacturing a photoelectric conversion element according to this embodiment. The method for manufacturing a photoelectric conversion element according to this embodiment manufactures a photoelectric conversion element configured by sequentially forming a photoelectric conversion unit A and a second photoelectric conversion unit B on a transparent conductive film 2 as shown in FIG. A step S12 of plasma-treating the transparent conductive film 2, a step S13 of forming a photoelectric conversion layer on the transparent conductive film 2, and a step S24 of forming a second photoelectric conversion layer on the photoelectric conversion layer. And. The method for manufacturing a photoelectric conversion element according to this embodiment preferably further includes a preparation step S11 of the transparent conductive film 2, and a formation step (not shown) of the first conductive film 6 and the second conductive film 7. Is preferably further provided. The photoelectric conversion layer in this embodiment is the photoelectric conversion unit A in the first embodiment, and the second photoelectric conversion layer in this embodiment is the p-type semiconductor layer 9 and the i-type semiconductor on the photoelectric conversion unit A. This is a photoelectric conversion unit B configured by sequentially laminating the layer 10 and the n-type semiconductor layer 11. Hereinafter, the photoelectric conversion unit A may be referred to as “front side photoelectric conversion unit A”, and the photoelectric conversion unit B may be referred to as “rear side photoelectric conversion unit B”.

  In the method for manufacturing a photoelectric conversion element according to this embodiment, as shown in the first embodiment, the transparent conductive film 2 preparation step S11, the transparent conductive film 2 is subjected to plasma treatment S12, and the photoelectric conversion unit A. After performing the formation process S13, the formation process S24 of the second photoelectric conversion unit B is performed, and then the formation process of the first conductive film 6 and the second conductive film 7 is performed. Thus, also in the manufacturing method of the photoelectric conversion element which concerns on this embodiment, since process S12 which plasma-processes the transparent conductive film 2 is implemented, the photoelectric conversion element excellent in the photoelectric conversion efficiency can be provided.

<Formation of Second Photoelectric Conversion Unit>
In the second photoelectric conversion unit formation step S <b> 24, it is preferable to implement <photoelectric conversion unit formation> in the first embodiment.

  Here, the p-type semiconductor layer 9 may be made of substantially the same material as the p-type semiconductor layer 3 or may be made of a material different from that of the p-type semiconductor layer 3. For example, the p-type semiconductor layer 9 is preferably a p-type microcrystalline silicon layer doped with 0.01 atom% or more of a p-type impurity such as boron.

  The i-type semiconductor layer 10 may be made of substantially the same material as the i-type semiconductor layer 4 or may be made of a material different from that of the i-type semiconductor layer 4. However, it is preferable to determine the compositions of the i-type semiconductor layer 4 and the i-type semiconductor layer 10 so that the optical forbidden band width of the i-type semiconductor layer 4 is larger than the optical forbidden band width of the i-type semiconductor layer 10. . Thereby, in the front side photoelectric conversion unit A, the optical forbidden band width of the photoelectric conversion layer is larger than that in the rear side photoelectric conversion unit B, so that photoelectric conversion is possible over a wide wavelength range of incident light. Therefore, since incident light can be used effectively, the conversion efficiency of the photoelectric conversion element is improved as compared with the first embodiment. Specifically, when the i-type semiconductor layer 4 is made of amorphous silicon, the i-type semiconductor layer 10 is preferably made of microcrystalline silicon.

  Further, each of the i-type semiconductor layer 4 and the i-type semiconductor layer 10 has a wavelength range of light that can be photoelectrically converted in the i-type semiconductor layer 4 wider than a wavelength range of light that can be photoelectrically converted in the i-type semiconductor layer 10. It is preferable to determine the composition. Thereby, in the front side photoelectric conversion unit A, compared with the back side photoelectric conversion unit B, photoelectric conversion is possible over a wide wavelength range. Therefore, since incident light can be used effectively, the conversion efficiency of the photoelectric conversion element is improved as compared with the first embodiment. Specifically, when the i-type semiconductor layer 4 is made of microcrystalline silicon, the i-type semiconductor layer 10 is preferably composed of amorphous silicon.

  The n-type semiconductor layer 11 may be made of substantially the same material as the n-type semiconductor layer 5, or may be made of a material different from that of the n-type semiconductor layer 5. For example, the n-type semiconductor layer 11 is preferably an n-type microcrystalline silicon layer doped with 0.01 atomic% or more of an n-type impurity such as phosphorus.

  As shown in FIG. 3, the photoelectric conversion element thus obtained has a transparent conductive film 2, a photoelectric conversion unit A, a second photoelectric conversion unit B, and a first conductive film on a translucent substrate 1. 6 and the second conductive film 7 are sequentially stacked. The photoelectric conversion unit A is configured by sequentially stacking a p-type semiconductor layer 3, an i-type semiconductor layer 4, and an n-type semiconductor layer 5 on the first surface 2 a of the transparent conductive film 2. The second photoelectric conversion unit B is configured by stacking a p-type semiconductor layer 9, an i-type semiconductor layer 10, and an n-type semiconductor layer 11 in this order on the photoelectric conversion unit A.

  In the present embodiment, the second photoelectric conversion unit B may be provided on the photoelectric conversion unit A via the second transparent conductive film.

<Other embodiments>
As an example of the photoelectric conversion layer, the photoelectric conversion unit A is taken as an example in the first embodiment, and the photoelectric conversion unit A and the photoelectric conversion unit B are taken as examples in the second embodiment. Is not limited to the photoelectric conversion unit A and the photoelectric conversion unit B. For example, instead of the photoelectric conversion unit A, a photoelectric conversion unit in which an n-type semiconductor layer 5, an i-type semiconductor layer 4, and a p-type semiconductor layer 3 are sequentially formed on the transparent conductive film 2 may be used. good. Further, instead of the photoelectric conversion unit B, a photoelectric conversion unit in which the n-type semiconductor layer 11, the i-type semiconductor layer 10, and the p-type semiconductor layer 9 are sequentially formed on the photoelectric conversion unit A may be used. good.

  The photoelectric conversion element may include three or more photoelectric conversion units. In this case, the wavelength range of light that can be photoelectrically converted is gradually increased from the rear side (back side with respect to the incident light, the same applies hereinafter) to the front side (front side with respect to the incident light, the same applies hereinafter). If the composition of the i-type semiconductor layer of each photoelectric conversion unit is adjusted, the conversion efficiency of the photoelectric conversion element is further improved. Moreover, if the composition of the i-type semiconductor layer of each photoelectric conversion unit is adjusted so that the optical forbidden band width gradually increases from the rear side toward the front side, the conversion efficiency of the photoelectric conversion element is further improved.

  A non-translucent substrate may be used in place of the translucent substrate 1 (substrate type photoelectric conversion element). As a method of manufacturing a photoelectric conversion element using a non-translucent substrate, a method of sequentially forming a transparent conductive film and a photoelectric conversion unit on a non-transparent substrate may be used. A method of preparing the formed non-translucent substrate and forming a photoelectric conversion unit on the transparent conductive film may be used. When a non-translucent substrate is used, light is incident from the side opposite to the non-translucent substrate, and thus the non-transparent substrate faces inward (the side opposite to the incident side). Therefore, a transparent barrier film or cover glass is required on the incident side. However, it is advantageous in that it is rich in substrate material selectivity and substrate flexibility. In addition, since a non-translucent substrate can be made conductive, a transparent conductive film is not necessary. Here, the non-translucent substrate is a substrate that is difficult to transmit sunlight, for example, a metal plate.

  A reflective layer having a refractive index smaller than that of the i-type semiconductor layer is preferably provided behind the photoelectric conversion unit as viewed from the light incident side. Thereby, since the light of a specific wavelength is reflected effectively by the reflective layer, the light confinement effect can be improved. Therefore, the conversion efficiency of the photoelectric conversion element can be further improved. Furthermore, since the thickness of the photoelectric conversion unit A can be reduced as much as possible by providing the reflective layer, the productivity of the photoelectric conversion element, that is, the cost reduction of the photoelectric conversion element can be achieved. Here, the reflective layer is provided behind the photoelectric conversion unit as viewed from the light incident side, not only when the reflective layer is in contact with the photoelectric conversion unit, but also when the reflective layer passes through another layer of the photoelectric conversion unit. Including the case where it is arranged on the rear side.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to a following example, unless the meaning is exceeded.

  In the following Examples 1-4 and Comparative Examples 1-3, the photoelectric conversion element containing one photoelectric conversion unit was produced, and the output characteristic was measured.

<Example 1>
In Example 1, the photoelectric conversion element shown in FIG. 1 was produced. First, an Asahi-U substrate manufactured by Asahi Glass Co., Ltd., which is a translucent substrate 1 with a transparent conductive film 2, was prepared. Next, using a plasma CVD apparatus having three film forming chambers, a gas treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. : CO ₂
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

  On the 1st surface 2a of the transparent conductive film 2, the amorphous photoelectric conversion unit A was produced on the conditions shown in Table 1 using the said plasma CVD apparatus. The film forming chamber of the CVD apparatus includes a chamber (P1 chamber) for forming a p-type semiconductor layer, a chamber (I1 chamber) for forming an i-type semiconductor layer, and a chamber chamber (N1 chamber) for forming an n-type semiconductor layer. It has. First, the p-type semiconductor layer 3 is formed in the P1 chamber under the conditions in Table 1, the i-type semiconductor layer 4 is formed in the I1 chamber under the conditions in Table 1, and then the n-type semiconductor layer 5 is formed in the N1 chamber. It formed on the conditions of Table 1. Thereafter, a first conductive film 6 made of a ZnO film having a thickness of 60 nm was formed by sputtering, and then a second conductive film 7 made of an Ag film having a thickness of 120 nm was formed by sputtering. Thereby, the photoelectric conversion element in Example 1 was obtained.

The obtained photoelectric conversion element was irradiated with AM1.5 light with a light amount of 100 mW / cm ² , and its output characteristics were measured at room temperature.

  In Table 1, power is the power of the high-frequency power source, the substrate temperature is the temperature of the translucent substrate 1, and the pressure is the pressure in the CVD apparatus. The same applies to Table 3 below.

<Example 2>
In Example 2, photoelectric conversion was performed by the method described in Example 1 except that the plasma treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. The element was manufactured and the obtained photoelectric conversion element was evaluated. Gas type: CO ₂ and Ar
Flow rate ratio: CO ₂ / (CO ₂ + Ar) = 0.27
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

<Example 3>
In Example 3, photoelectric conversion was performed by the method described in Example 1 except that plasma treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. The element was manufactured and the obtained photoelectric conversion element was evaluated. Gas type: CO ₂ and Ar
Flow ratio: CO ₂ / (CO ₂ + Ar) = 0.05
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

<Example 4>
In Example 4, photoelectric conversion was performed by the method described in Example 1 except that plasma treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. The element was manufactured and the obtained photoelectric conversion element was evaluated. Gas type: CO ₂ and H ₂
Flow rate ratio: CO ₂ / (CO ₂ + H ₂ ) = 0.76
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

<Comparative Example 1>
In Comparative Example 1, the photoelectric conversion of Comparative Example 1 was performed in the same manner as in Example 1 except that the photoelectric conversion element was produced without performing plasma treatment on the first surface 2a of the transparent conductive film 2. A conversion element was produced.

  Specifically, an amorphous photoelectric conversion unit A is produced on an Asahi-U substrate manufactured by Asahi Glass Co., Ltd., which is a translucent substrate 1 with a transparent conductive film 2, using a plasma CVD apparatus having three film forming chambers. did. In Comparative Example 1, a general-purpose continuous separation formation type CVD apparatus can be used as the plasma CVD apparatus. The film forming chamber includes a chamber (P1 chamber) for forming a p-type semiconductor layer and an i-type semiconductor. A chamber (I1 room) for forming a layer and a chamber room (N1 room) for forming an n-type semiconductor layer are formed. The p-type semiconductor layer 3 was formed in the P1 chamber, the i-type semiconductor layer 4 was formed in the I1 chamber, and the n-type semiconductor layer 5 was formed in the N1 chamber. Table 1 shows the respective film forming conditions. Thereafter, a first conductive film 6 made of a ZnO film having a thickness of 60 nm was formed by sputtering, and then a second conductive film 7 made of an Ag film having a thickness of 120 nm was formed by sputtering. Thus, the photoelectric conversion element in Comparative Example 1 was obtained. And according to the method similar to the said Example 1, the output characteristic of the obtained photoelectric conversion element was measured.

<Comparative example 2>
In Comparative Example 2, photoelectric conversion was performed by the method described in Example 1 except that the plasma treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. The element was manufactured and the obtained photoelectric conversion element was evaluated. Gas type: CO ₂ and H ₂
Flow rate ratio: CO ₂ / (CO ₂ + H ₂ ) = 0.5
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

<Comparative Example 3>
In Comparative Example 3, photoelectric conversion was performed by the method described in Example 1 except that the plasma treatment was performed on the first surface 2a of the transparent conductive film 2 on the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. under the following conditions. The element was manufactured and the obtained photoelectric conversion element was evaluated. Gas type: CO ₂ and H ₂
Flow rate ratio: CO ₂ / (CO ₂ + H ₂ ) = 0.25
Pressure in the chamber: 212Pa
Plasma power: 150 mW / cm ² .

<Results and discussion>
The results are shown in Table 2.

When the output characteristics of the photoelectric conversion element of Example 1 were measured, the open circuit voltage (Voc) was 0.85 V, the short circuit current density (Jsc) was 13.75 mA / cm ² , and the fill factor (FF) was It was 0.727, and the conversion efficiency (Eff) was 8.50%.

When the output characteristics of the photoelectric conversion element of Example 2 were measured, the open circuit voltage (Voc) was 0.85 V, the short circuit current density (Jsc) was 13.97 mA / cm ² , and the fill factor (FF) was It was 0.702, and the conversion efficiency (Eff) was 8.34%.

When the output characteristics of the photoelectric conversion element of Example 3 were measured, the open circuit voltage (Voc) was 0.85 V, the short-circuit current density (Jsc) was 13.90 mA / cm ² , and the fill factor (FF) was It was 0.697, and the conversion efficiency (Eff) was 8.24%.

When the output characteristics of the photoelectric conversion element of Example 4 were measured, the open-circuit voltage (Voc) was 0.84 V, the short-circuit current density (Jsc) was 13.77 mA / cm ² , and the fill factor (FF) was It was 0.698, and the conversion efficiency (Eff) was 8.09%.

When the output characteristics of the photoelectric conversion device of Comparative Example 1 were measured, the open circuit voltage (Voc) was 0.84 V, the short circuit current density (Jsc) was 13.72 mA / cm ² , and the fill factor (FF) was It was 0.701, and the conversion efficiency (Eff) was 8.08%.

When the output characteristics of the photoelectric conversion element of Comparative Example 2 were measured, the open circuit voltage (Voc) was 0.84 V, the short circuit current density (Jsc) was 13.46 mA / cm ² , and the fill factor (FF) was It was 0.688, and the conversion efficiency (Eff) was 7.78%.

When the output characteristics of the photoelectric conversion element of Comparative Example 3 were measured, the open circuit voltage (Voc) was 0.80 V, the short circuit current density (Jsc) was 13.72 mA / cm ² , and the fill factor (FF) was It was 0.669, and the conversion efficiency (Eff) was 7.34%.

  In each of Examples 1 to 4, compared to Comparative Example 1, at least one of the short circuit current density (Jsc) and the fill factor (FF) was improved, and as a result, the conversion efficiency (Eff) was improved. The reason is as described in the first embodiment. That is, the reason why the photoelectric conversion efficiency is improved by performing plasma treatment on the transparent conductive film 2 is not speculative, but the transparent conductive film such as a change in the texture structure (uneven structure) on the surface of the transparent conductive film It is thought that changes in the shape of the surface have an effect.

  On the other hand, in Comparative Examples 2 to 3, the overall characteristics were reduced as compared with Comparative Example 1, and as a result, the conversion efficiency (Eff) was reduced. The reason for this is considered to be that reduction of the transparent conductive film occurs due to excessive hydrogen atoms, thereby causing a decrease in light transmittance and a decrease in conductivity.

  In the following Examples 5-8 and Comparative Examples 4-6, the photoelectric conversion element containing an amorphous photoelectric conversion unit and a microcrystalline photoelectric conversion unit was produced, and the output characteristic was measured.

<Example 5>
In Example 5, the photoelectric conversion element shown in FIG. 3 was produced. After producing the amorphous photoelectric conversion unit A in Example 1, the microcrystalline p-type semiconductor (μc-p) layer 9 is formed in the P1 chamber, and the microcrystalline i-type semiconductor (μc-i) layer 10 is formed as I1. The photoelectric conversion unit B was manufactured by forming the microcrystalline n-type semiconductor (μc-n) layer 11 in the N1 chamber. Table 3 shows the respective film forming conditions. Thereafter, a first conductive film 6 made of a ZnO film having a thickness of 60 nm was formed by sputtering, and then a second conductive film 7 made of an Ag film having a thickness of 120 nm was formed by sputtering. Thus, the photoelectric conversion element in Example 5 was obtained. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Example 6>
In Example 6, after producing an amorphous photoelectric conversion unit according to the method described in Example 2 above, a microcrystalline photoelectric conversion unit was prepared according to the method described in Example 5 above. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Example 7>
In Example 7, after producing an amorphous photoelectric conversion unit according to the method described in Example 3, a microcrystalline photoelectric conversion unit was prepared according to the method described in Example 5. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Example 8>
In Example 8, after producing an amorphous photoelectric conversion unit according to the method described in Example 4 above, a microcrystalline photoelectric conversion unit was prepared according to the method described in Example 5 above. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Comparative example 4>
In Comparative Example 4, after producing the amorphous photoelectric conversion unit in Comparative Example 1, the microcrystalline p-type semiconductor layer 9 is formed in the P1 chamber, and the microcrystalline i-type semiconductor layer 10 is formed in the I1 chamber. A microcrystalline n-type semiconductor layer 11 was formed in the N1 chamber, and a photoelectric conversion unit B was manufactured. Table 3 shows the respective film forming conditions. Thereafter, a first conductive film 6 made of a ZnO film having a thickness of 60 nm was formed by sputtering, and then a second conductive film 7 made of an Ag film having a thickness of 120 nm was formed by sputtering. Thus, the photoelectric conversion element in Comparative Example 4 was obtained. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Comparative Example 5>
In Comparative Example 5, an amorphous photoelectric conversion unit was produced according to the method described in Comparative Example 2, and then a microcrystalline photoelectric conversion unit was produced according to the method described in Example 5. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Comparative Example 6>
In Comparative Example 6, an amorphous photoelectric conversion unit was manufactured according to the method described in Comparative Example 3, and then a microcrystalline photoelectric conversion unit was manufactured according to the method described in Example 5. According to the method described in Example 1 above, the obtained photoelectric conversion element was evaluated.

<Results and discussion>
The results are shown in Table 4.

When the output characteristics of the photoelectric conversion element of Example 5 were measured, the open-circuit voltage (Voc) was 1.35 V, the short-circuit current density (Jsc) was 11.62 mA / cm ² , and the fill factor (FF) was It was 0.752, and the conversion efficiency (Eff) was 11.80%.

When the output characteristics of the photoelectric conversion element of Example 6 were measured, the open-circuit voltage (Voc) was 1.37 V, the short-circuit current density (Jsc) was 11.55 mA / cm ² , and the fill factor (FF) was It was 0.740, and the conversion efficiency (Eff) was 11.71%.

When the output characteristics of the photoelectric conversion element of Example 7 were measured, the open-circuit voltage (Voc) was 1.35 V, the short-circuit current density (Jsc) was 11.50 mA / cm ² , and the fill factor (FF) was It was 0.740, and the conversion efficiency (Eff) was 11.49%.

When the output characteristics of the photoelectric conversion element of Example 8 were measured, the open circuit voltage (Voc) was 1.36 V, the short circuit current density (Jsc) was 11.44 mA / cm ² , and the fill factor (FF) was The conversion efficiency (Eff) was 11.40%.

When the output characteristics of the photoelectric conversion device of Comparative Example 4 were measured, the open circuit voltage (Voc) was 1.35 V, the short circuit current density (Jsc) was 11.50 mA / cm ² , and the fill factor (FF) was It was 0.735, and the conversion efficiency (Eff) was 11.41%.

When the output characteristics of the photoelectric conversion element of Comparative Example 5 were measured, the open circuit voltage (Voc) was 1.35 V, the short circuit current density (Jsc) was 11.10 mA / cm ² , and the fill factor (FF) was The conversion efficiency (Eff) was 10.49%.

When the output characteristics of the photoelectric conversion element of Comparative Example 6 were measured, the open circuit voltage (Voc) was 1.31 V, the short circuit current density (Jsc) was 11.05 mA / cm ² , and the fill factor (FF) was It was 0.685, and the conversion efficiency (Eff) was 9.92%.

  Comparing Comparative Example 4 and Examples 5 to 8, similarly to the amorphous silicon single cell (Example 1 above), in Examples 5 to 8, the short-circuit current density (Jsc) and the fill factor ( FF) improved. Therefore, it is conceivable that the same phenomenon as in the amorphous silicon single cell (Examples 1 to 4) occurs in the tandem cell (Examples 5 to 8). Therefore, it is considered that the plasma treatment to the transparent conductive film layer can be a practical means for improving the conversion efficiency. Note that the present inventors believe that the same effect can be expected even when a non-translucent substrate is used instead of the Asahi-U substrate manufactured by Asahi Glass Co., Ltd. (substrate type photoelectric conversion element).

  On the other hand, in Comparative Examples 5 to 6, compared with Comparative Example 4, an overall characteristic deterioration was observed, and as a result, the conversion efficiency (Eff) decreased. The reason for this is considered to be that reduction of the transparent conductive film occurs due to excessive hydrogen atoms, thereby causing a decrease in light transmittance and a decrease in conductivity.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Translucent substrate, 2 Transparent electrically conductive film, 3 p-type semiconductor layer, 4 i-type semiconductor layer, 5 n-type semiconductor layer, 6 1st electrically conductive film, 7 2nd electrically conductive film, 9 p-type semiconductor layer, 10 i-type semiconductor layer, 11 n-type semiconductor layer, A photoelectric conversion unit, B photoelectric conversion unit.

Claims (9)

A method for producing a photoelectric conversion element comprising a transparent conductive film and a photoelectric conversion layer,
Plasma-treating the transparent conductive film using a gas containing carbon dioxide;
And a step of forming the photoelectric conversion layer on the transparent conductive film. The method for producing a photoelectric conversion element according to claim 1, wherein the step of plasma-treating the transparent conductive film is performed using a gas satisfying the following formula 1 or the following formula 2.
Formula 1: 0.74 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of hydrogen) ≦ 1.0
Formula 2: 0.05 ≦ volume of carbon dioxide / (volume of carbon dioxide + volume of inert gas) ≦ 1.0   The said transparent conductive film is a manufacturing method of the photoelectric conversion element of Claim 1 or 2 containing a tin oxide.   The method for producing a photoelectric conversion element according to any one of claims 1 to 3, wherein the step of forming the photoelectric conversion layer comprises forming the photoelectric conversion layer on the plasma-treated surface of the transparent conductive film. .   The photoelectric conversion element according to claim 1, wherein the step of forming the photoelectric conversion layer forms a photoelectric conversion unit including a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer. Manufacturing method.   The manufacturing method of the photoelectric conversion element in any one of Claims 1-5 provided with the process of forming a 2nd photoelectric conversion layer on the said photoelectric conversion layer.   The manufacturing method of the photoelectric conversion element in any one of Claims 1-5 further provided with the process of forming a 2nd photoelectric converting layer through the 2nd transparent conductive film on the said photoelectric converting layer.   The said transparent conductive film is a film | membrane provided on the translucent board | substrate, The manufacturing method of the photoelectric conversion element in any one of Claims 1-7.   The method for manufacturing a photoelectric conversion element according to claim 1, wherein the transparent conductive film is a film provided on a non-translucent substrate.

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