JP2006269607A - Method of manufacturing photovoltaic power element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a photovoltaic power element having excellent characteristics by preventing the characteristics from being deteriorated due to the mixing of doping gases or the like into a substantially intrinsic i-type semiconductor layer, even if a transparent conductive layer wherein a high texture degree is included but adsorptive sites increase is used, when manufacturing the photovoltaic power element including a pin junction. <P>SOLUTION: This method includes at least, in the order of descriptions, steps of forming a transparent conductive layer on a substrate; forming a semiconductor layer with a first conductive type; separating at least a part of elements adsorbed in the transparent conductive layer or the semiconductor layer, and determining the first conductive type by heat treatment and/or plasma treatment at a substrate temperature of 100 to 400°C; forming a substantially intrinsic second semiconductor layer on the semiconductor layer with the first conductive type; and forming a third semiconductor layer with a conductive type opposite to the first conductive type. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a photovoltaic device. More specifically, the present invention relates to a method for manufacturing a photovoltaic device, particularly a thin film solar cell, which is designed so that photocurrent is increased by effectively using incident light by using a transparent conductive layer having an uneven surface.

  In recent years, various research and development have been conducted for practical application of solar power generation using solar cells. In order to establish a solar cell to cover power demand, it is required that the solar cell used has sufficiently high photoelectric conversion efficiency, excellent reliability, and capable of mass production at low cost. Is done.

  Thin-film solar cells using silicon-based non-single-crystal semiconductors are compared with solar cells using single-crystal and polycrystalline semiconductors by readily performing glow discharge decomposition of readily available source gases such as silanes, metal sheets and resins. Since a deposited film such as a semiconductor film can be formed in a large area on a relatively inexpensive belt-like substrate such as a sheet, it has been attracting attention as a solar cell capable of reducing the cost.

  On the other hand, thin film solar cells have not been used in earnest until now because their photoelectric conversion efficiency is lower than that of crystalline silicon solar cells. Therefore, various means have been taken to improve the performance of the thin film solar cell.

  One way to increase the photoelectric conversion efficiency of a thin film solar cell is to absorb incident light without waste over a wide wavelength region. As one of the means for solving this problem, a stacked solar cell in which elements having semiconductor layers having different band gaps as photoactive layers are stacked is well known. In this stacked solar cell, an element using a semiconductor having a relatively wide band gap such as amorphous silicon is disposed on the light incident side to absorb light having a short wavelength with a large energy, and a band of microcrystalline silicon or the like is disposed below the element. An element using a semiconductor with a relatively narrow gap is arranged to absorb light having a long wavelength with low energy transmitted through the upper element, thereby efficiently absorbing and utilizing light over a wide wavelength region. For example, in Patent Document 1, amorphous silicon is used as the i-type layer of the semiconductor layer having the first pin junction from the light incident side, and microcrystals are used as the i-type layers of the semiconductor layer having the second and third pin junctions. A triple stacked solar cell using silicon is disclosed.

  In addition, as another means for increasing the photoelectric conversion efficiency of the thin film solar cell, a back reflection layer is provided for effectively returning incident sunlight by returning sunlight that has not been absorbed by the semiconductor layer back to the semiconductor layer. Is well known. When sunlight is incident from the surface of the semiconductor layer, a highly reflective silver, aluminum, or the like is provided as a metal layer on a conductive substrate such as stainless steel by sputtering or the like, and optically in a predetermined wavelength range on the metal layer. By providing a transparent conductive layer such as zinc oxide that is transparent and has an uneven shape (texture), the reflected light can be used effectively to increase the short-circuit current density.

  Further, in Patent Document 2, a step of forming a first zinc oxide thin film by sputtering on a substrate, and immersing the substrate in an aqueous solution containing at least nitrate ions, zinc ions, and carbohydrates, A step of forming a second zinc oxide thin film on the first zinc oxide thin film by an electrolytic deposition method by energizing between the counter electrode and the immersed counter electrode. A manufacturing method is disclosed, and it can be carried out at low cost, and it is possible to form zinc oxide having excellent optical transparency and high texture.

  Moreover, in patent document 3, in the zinc oxide layer produced by the electrolytic deposition method, the electric resistance value shows a high value by the adsorbed moisture, and the resistance of the zinc oxide layer can be reduced by heating and drying the zinc oxide layer. It is disclosed.

  Patent Document 4 discloses a method of reducing surface contamination of a semiconductor substrate by desorbing chemical species in a chamber adsorbed on the semiconductor substrate by subjecting the semiconductor substrate to heat treatment.

  Moreover, in patent document 5, the process of processing the surface of transparent conductive films, such as a zinc oxide, by a noble gas plasma, and a one conductivity type amorphous | non-crystalline substance on the surface area | region of the said transparent conductive film processed by this noble gas plasma And a process for depositing a thin film semiconductor layer. A method for manufacturing a photovoltaic device is disclosed, and a region having low crystallinity is formed on the surface of a transparent conductive film by such a rare gas plasma treatment. In addition, it is said that the ohmic characteristics at the interface with the semiconductor layer can be improved.

JP-A-11-243218 Japanese Patent Laid-Open No. 10-140373 JP 2001-152390 A US Pat. No. 6,528,427 JP 2001-339079 A

  As described above, by forming a zinc oxide layer (hereinafter referred to as a ZnO layer) by an electrolytic deposition method, it has become possible to obtain a transparent conductive layer having further excellent optical transparency and high texture.

  However, the present inventors have produced a photovoltaic element using a transparent conductive layer having excellent optical transparency and a high texture level, but on the contrary, a sudden decrease in output current occurs, It has been found that the characteristics may drop rapidly.

The present inventors have investigated the cause of this, and when a transparent conductive layer having a higher degree of texture, particularly a ZnO layer having an inclined c axis formed by electrolytic deposition, is used, the surface becomes more active. When a semiconductor layer having the first conductivity type (for example, n-type) is formed by a plasma CVD method or the like in a gas atmosphere containing a dopant gas (for example, PH ₃ ), the dopant gas or the like is mainly adsorbed on the surface of the transparent conductive layer. In addition, when pores and cracks exist in the ZnO layer, it has been found that dopant gas and the like are easily occluded in the portion. In addition, when a substantially intrinsic second semiconductor layer is formed by a plasma CVD method or the like in a state where a large number of dopant gases or the like are adsorbed and occluded, the dopant gas or the like adsorbed and occluded by plasma during the formation is excited and desorbed. The dopant gas is incorporated as an impurity into the intrinsic second semiconductor layer, and for example, when the dopant gas is PH ₃ , the intrinsic second semiconductor layer is likely to be weakly n-type. I found.

  In view of the above-described problems, the present invention provides a dopant gas or the like even when a transparent conductive layer having a high degree of texture produced by an electrolytic deposition method or the like is used as a back surface reflective layer of a photovoltaic device having a pin junction. It is an object of the present invention to provide a method for producing a photovoltaic device, particularly a thin-film solar cell, having good characteristics without causing deterioration of characteristics due to the adsorption sites.

  Therefore, the present invention includes a step of forming a transparent conductive layer on a substrate, a step of forming a semiconductor layer having a first conductivity type, and the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer. A step of detaching at least a part of the element to be determined by heat treatment and / or plasma treatment at a substrate temperature of 100 to 400 ° C., and a second semiconductor substantially intrinsic on the semiconductor layer having the first conductivity type There is provided a method for manufacturing a photovoltaic device, comprising: a step of forming a layer; and a step of forming a third semiconductor layer having a conductivity type opposite to the first conductivity type in this order. .

In the present invention, the plasma treatment is preferably a rare gas plasma treatment using at least one of He, Ne, Ar, Kr, and Xe.
Further, in the present invention, when the element that determines the first conductivity type is P, a higher effect is exhibited.
In the present invention, the transparent conductive layer is composed of a ZnO layer having an inclined c axis, and the (100) plane and / or (101) plane of the ZnO layer has a (002) plane diffraction intensity. A higher effect is exhibited when it is 0.5% or more.
In the present invention, a higher effect is exhibited when the irregular reflectance of the transparent conductive layer is 60% or more at a wavelength of 800 nm.
In the present invention, a higher effect is exhibited when the transparent conductive layer is composed of two layers of a ZnO layer produced by electrolytic deposition on a ZnO layer produced by sputtering.
In the present invention, the substantially intrinsic second semiconductor layer is made of microcrystalline silicon and exhibits a higher effect when the film thickness is in the range of 0.5 μm to 6 μm.

According to the method for manufacturing a photovoltaic device of the present invention, the transparent conductive layer is formed on the substrate, the semiconductor layer having the first conductivity type is subsequently formed, and then the transparent conductive layer or the semiconductor layer adsorbed on the semiconductor layer is formed. In the substantially intrinsic second semiconductor layer formed on the semiconductor layer having the first conductivity type, by providing a step of detaching at least a part of the element that determines the one conductivity type. It is possible to suppress the contamination of the impurity element.
As a result, it is possible to avoid deterioration of the characteristics of the photovoltaic element due to the mixing of the impurity element into the substantially intrinsic second semiconductor layer. Furthermore, when the texture level of the transparent conductive layer is increased, the surface becomes more active and the number of adsorption sites for impurities and the like increases. However, by providing the desorption step of the present invention, the transparent conductive layer having a higher texture level is provided. It becomes possible to make full use of the layer, and it is possible to provide a photovoltaic element, in particular, a thin film solar cell, having high characteristics and high photocurrent density.

  In the present invention, after forming the transparent conductive layer on the substrate and subsequently forming the semiconductor layer having the first conductivity type, at least the first conductive type adsorbed on the transparent conductive layer or the semiconductor layer is determined. By providing a part of the semiconductor layer having the first conductivity type, the incorporation of the impurity element into the substantially intrinsic second semiconductor layer formed on the semiconductor layer having the first conductivity type is suppressed. . As a result, it is possible to avoid degradation of the characteristics of the photovoltaic element due to the mixing of the impurity element into the substantially intrinsic second semiconductor layer, which has been a problem. Furthermore, when the texture level of the transparent conductive layer is increased, the surface becomes more active and adsorption sites for impurities and the like increase. However, by providing the desorption step, a transparent conductive layer having a higher texture level can be obtained. A photovoltaic device having high characteristics with high photocurrent density can be obtained.

Hereinafter, the background to the present invention will be described in detail.
First, the inventors experimentally investigated the relationship between the orientation and texture of the transparent conductive layer formed on the substrate and the amount of adsorbed impurity elements after actually producing a photovoltaic device.

FIG. 1 is a schematic cross-sectional view of a single type photovoltaic element showing an example of the photovoltaic element in the present invention. In FIG. 1, 101 is a substrate, 102 is a metal layer, 103 is a transparent conductive layer prepared by sputtering, 104 is a transparent conductive layer prepared by electrolytic deposition, 105 is an n-type first semiconductor layer, and 106 is A process for desorbing at least part of an element that determines n-type adsorbed on the transparent conductive layer 104 or the semiconductor layer 105, 107 is a substantially intrinsic i-type second semiconductor layer, and 108 is a p-type first semiconductor layer. Three semiconductor layers, 109 is a transparent electrode layer, 110 is a collector electrode, and the incident light 111 is irradiated from the transparent electrode layer 109 side.
The above components will be described below.

(substrate)
As a material constituting the substrate of the photovoltaic device according to the present invention, there is little deformation or distortion with respect to the temperature required when the metal layer, the transparent conductive layer, the semiconductor layer and the transparent electrode layer are produced, and the desired strength, What has electroconductivity is preferable, Specifically, resin, such as polyimide, polyamide, polyethylene terephthalate, glass, etc. which coated metal thin plates, such as stainless steel, aluminum, and its alloy, and an electroconductive material, etc. are used. Here, a stainless steel substrate is used as the substrate 101.

(Metal layer)
In the photovoltaic device according to the present invention, it is preferable to provide a metal layer on the substrate for efficiently reflecting incident light that could not be absorbed by the semiconductor layer. As a specific material, simple metals and alloys such as Ag, Al, Pt, Au, Ni, Ti, Cr, and Cu are used. Here, Ag having high reflectivity is used as the metal layer 102. In addition, examples of the manufacturing method include a vacuum evaporation method, an electron beam evaporation method, a sputtering method, and the like.

(Transparent conductive layer)
In the photovoltaic device according to the present invention, a transparent conductive oxide layer such as ZnO, SnO ₂ , In ₂ O ₃ or ITO having a texture structure is suitably used as the transparent conductive layer. The transparent conductive layer is combined with the metal layer as a back reflecting layer, and has an effect of confining light in the semiconductor layer by multiply reflecting incident light. In addition, there is an effect of preventing the metal element constituting the metal layer from diffusing into the semiconductor layer. As a manufacturing method, any method such as resistance heating or vacuum deposition using an electron beam, a sputtering method, an ion plating method, a CVD method, or an electrolytic deposition method may be used. In order to improve the adhesion to the formed metal layer, ZnO produced by a sputtering method was used as the transparent conductive layer 103, and ZnO produced by an electrolytic deposition method that easily forms a texture structure was used as the transparent conductive layer 104. .
Here, the ZnO film produced by the electrolytic deposition method will be described in detail.

  The transparent conductive layer 104 can be formed using, for example, the apparatus shown in FIG. In FIG. 2, 201 is a corrosion resistant container, 202 is an electrolytic deposition aqueous solution, 203 is a substrate, 204 is a counter electrode, 205 is a DC power supply, 206 is a load resistance, 207 is a substrate support shaft, 208 is an electrode support shaft, and 209 is A substrate branch, 210 is an electrode branch, 211 is a stirrer, and 212 is a thermostatic plate.

  As the electrolytic precipitation aqueous solution 202, an aqueous solution containing at least nitrate ions and zinc ions is used, and the concentration is preferably 0.002 mol / l to 3.0 mol / l, more preferably 0.01 mol / l. ~ 1.5 mol / l, optimally 0.05 mol / l to 0.7 mol / l. The aqueous solution 202 may contain saccharose or dextrin. The sucrose concentration is preferably 1 g / l to 500 g / l, more preferably 3 g / l to 100 g / l, and the dextrin concentration is preferably Is 0.01 g / l to 10 g / l, more preferably 0.025 g / l to 1 g / l. Furthermore, a ZnO film having a developed texture structure can be formed by adding a polyvalent carboxylic acid having a carboxyl group bonded to each of carbons having sp2 hybrid orbitals in the aqueous solution 202. Examples of the polyvalent carboxylic acid include phthalic acid, isophthalic acid, adipic acid, malic acid, malonic acid, maleic acid, formic acid, oxalic acid, benzoic acid, succinic acid, tartaric acid, and the concentration is 0.01 μmol / l to 10 mol / 1, more preferably 0.1 μmol / l to 1 mol / l, and most preferably 0.5 μmol / l to 500 μmol / l.

The value of the current flowing between the substrate 203 and the counter electrode 204, preferably ^{0.1mA / cm 2 ~100mA / cm 2} , more preferably ^{1mA / cm 2 ~30mA / cm 2} , and most 4mA / cm ² ~20mA / Cm ² . In addition, when the pH in the aqueous solution 202 is 3 or more, the electric conductivity is 10 mS / cm or more, and the solution temperature is 60 ° C. or more, a uniform ZnO film with less abnormal growth can be efficiently formed.

  It is known that the ZnO film having c-axis orientation has a dominant X-ray diffraction intensity peak on the ZnO (002) plane. However, when the texture of the ZnO film produced by the above-described electrolytic deposition method is increased by changing the production conditions, the (100) plane other than the (002) plane, (101) plane, (102) plane, etc. As a result, the X-ray diffraction intensity peak gradually increased.

  3a to 3f, on the stainless steel substrate 101, first, 800 nm of Ag is formed as the metal layer 102 by the sputtering method, and 200 nm of ZnO is formed as the transparent conductive layer 103 by the sputtering method. The layer 104 was produced by changing the production conditions so that the degree of texture was different by 2300 nm electrolytic deposition, and produced 6 types (Samples 1 to 6). The total reflectance, irregular reflectance and X of the back surface reflection layer at a wavelength of 800 nm were produced. The result of having measured the line diffraction intensity peak is shown.

  Table 1 also shows the X-ray diffraction intensity peak ratios of other ZnO azimuth planes with respect to the ZnO (002) plane of each sample. (The numerical values in the table represent the percentage of other ZnO orientation planes when the X-ray diffraction intensity peak of the ZnO (002) plane is taken as 100%.)

  Further, FIGS. 4A and 4B show irregular reflectances with respect to respective X-ray diffraction intensity peak ratios of the ZnO (100) plane and the ZnO (101) plane with respect to the ZnO (002) plane.

  From the results shown in FIGS. 3a to 3f, FIG. 4 and Table 1, as the diffuse reflectance (texture degree) of the back reflecting layer is improved, the X-ray diffraction intensity of the (002) plane of ZnO is weakened, while other orientation planes In particular, it can be seen that the X-ray diffraction intensities of the (100) plane and (101) plane are significantly increased.

(Semiconductor layer)
Examples of the semiconductor material constituting the substantially intrinsic i-type semiconductor layer that is preferably used in the photovoltaic element according to the present invention include a-Si: H, a-SiC: H, and a-SiGe: H. , Silicon-based non-single-crystal semiconductor materials such as microcrystalline Si: H. Here, microcrystalline Si: H is used as the substantially intrinsic i-type semiconductor layer 107. The film thickness was 2500 nm.

  The n-type or p-type semiconductor layer preferably used in the present invention can be obtained by doping the semiconductor material constituting the i-type semiconductor layer with an impurity that controls valence electrons. In addition, it is preferable to include a microcrystalline layer in the semiconductor material constituting the n-type or p-type semiconductor layer because the utilization factor of light and the carrier density can be increased.

  The semiconductor layer used in the photovoltaic device of the present invention may be any silicon-based non-single-crystal semiconductor layer. However, a microcrystalline silicon layer that is sensitive to impurities, particularly that tends to be weakly n-type against impurities such as P, is used. A greater effect is exhibited when used in an i-type semiconductor layer.

  Examples of means for forming a semiconductor layer used in the photovoltaic device of the present invention include RF plasma CVD, VHF plasma CVD, microwave plasma CVD, photo CVD, thermal CVD, and MOCVD. These are appropriately selected and used.

(Transparent electrode layer)
In the photovoltaic device according to the present invention, since the sheet resistance of the semiconductor layer itself is high, a transparent upper electrode over the entire surface of the semiconductor layer is required, and the transparent electrode layer is excellent in transparency to visible light and electrical conductivity. Examples thereof include SnO ₂ , In ₂ O ₃ and ITO (In ₂ O ₃ + SnO ₂ ) having the above characteristics. Here, ITO was used as the transparent electrode layer 109.
As these manufacturing methods, a sputtering method, a resistance heating vapor deposition method, an electron beam vapor deposition method, a spray method, or the like can be used, and is appropriately selected according to demand.

(Collector electrode)
In the photovoltaic device according to the present invention, the current collecting electrode is provided to improve the current collecting efficiency. As a method for forming the current collecting electrode, a method of forming a metal of the current collecting pattern by an electron beam evaporation method, a sputtering method, or the like, And a method of forming a current collection pattern by printing a conductive paste by a screen printing method or the like, and a method of fixing an electrode in which a metal wire is coated with a carbon paste or the like with a thermocompression bonding device or the like. Here, a silver paste was screen printed as the collecting electrode 110 to form a collecting electrode having a width of 0.15 mm and a pitch of 3 mm.

As described above, with respect to the photovoltaic elements respectively produced on the back surface reflection layers (Samples 1 to 6 in Table 1) produced by changing the texture degree and orientation of the transparent conductive layer 104 described above, AM1.5 sun Solar cell characteristics were measured using a pseudo solar light source with a light intensity of 100 mW / cm ^{2 in} the optical spectrum.

  5A and 5B, X-ray diffraction of the ZnO (100) plane and the ZnO (101) plane with respect to the ZnO (002) plane when the ZnO films having different orientations are measured by the X-ray diffraction method. A graph is shown in which the intensity peak ratio is taken on the horizontal axis and the short-circuit photocurrent density (Jsc) obtained from the current-voltage characteristics of the photovoltaic device is taken on the vertical axis. From FIG. 5, for example, when the diffraction intensity ratio of the (100) plane to the diffraction intensity of the ZnO (002) plane is less than 0.5%, Jsc tends to increase as the intensity ratio increases. This corresponds to an increase in the texture level of the back reflective layer as the diffraction intensity ratio shown in FIG. 4 increases, and it is considered that the photocurrent density was improved by improving the texture level as originally intended. However, when the diffraction intensity ratio was increased to 0.5% or more, a sharp decrease in Jsc was observed even though the degree of texture was improved. Therefore, in order to investigate this cause, two types of ZnO films having a diffraction intensity ratio of the ZnO (100) plane to the diffraction intensity of the ZnO (002) plane of 0.2% (Sample 2) and 4.2% (Sample 6) are used. Secondary ion mass spectrometry (SIMS analysis) was performed on the photovoltaic element fabricated in (1), and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer was quantified.

As a result, it was found that a large amount of impurity elements were present in the i-type semiconductor layer when the diffraction intensity ratio was 4.2% as compared to 0.2%. Therefore, it is considered that when the diffraction intensity of other azimuth planes increases with respect to the diffraction intensity of the ZnO (002) plane, the number of sites where the impurity elements are adsorbed increases. When a source gas containing a high concentration of a doping gas such as PH ₃ is supplied to form, for example, an n-type semiconductor layer as a semiconductor layer having the first conductivity type thereon, a main layer is formed on the surface of the ZnO film. If a dopant gas or the like is adsorbed on the surface of the ZnO layer and there are pores or cracks in the ZnO layer, the dopant gas or the like is easily occluded in the portion, and a substantial amount of the dopant gas or the like is absorbed and occluded by a plasma CVD method or the like. When the intrinsic second semiconductor layer is formed, the dopant gas adsorbed and occluded by the plasma during the formation is excited and desorbed, and the dopant gas is taken into the substantially intrinsic second semiconductor layer as an impurity. The substantially intrinsic second semiconductor layer is made weak n-type, the substantial depletion layer is narrowed, and the generation of photocarriers is reduced, which causes a decrease in Jsc. Eteiru.

  Therefore, the present inventors form a semiconductor layer having the first conductivity type on the transparent conductive layer, and then desorb the element that determines the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer. By trying to solve the above-mentioned problems, the inclusion of the element determining the first conductivity type in the substantially intrinsic second semiconductor layer is prevented.

  Hereinafter, the “method for desorbing the element that determines the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer” according to the present invention will be described.

  Examples of the method for desorbing the element determining the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer of the present invention include heat treatment and plasma treatment, but they may be used in combination.

(Heat treatment)
The desorption of the adsorbed gas by the heat treatment makes it easy to move the surface as a two-dimensional gas by giving thermal energy to the adsorbed atoms adsorbed on the transparent conductive layer or semiconductor layer, and it is possible to collide with adjacent atoms and combine them. Use desorption back to the molecule.

  The heat treatment in the present invention must be performed so as not to affect the semiconductor layer having the first conductivity type, and vacuum heating is preferable. In addition, as described above, it is indispensable that the heating temperature does not affect the semiconductor layer having the first conductivity type, and is preferably in the vicinity of the deposition temperature of the semiconductor layer having the first conductivity type. As temperature, 100-400 degreeC is preferable and 200-300 degreeC is the most preferable. Further, it is necessary to immediately exhaust the adsorbed adsorbed gas. The heat treatment time depends on the material and texture of the transparent conductive layer and the film formation conditions (especially the type, concentration and amount of doping gas, film formation pressure and time) of the semiconductor layer having the first conductivity type. The amount of adsorbed gas adsorbed on the transparent conductive layer or the semiconductor layer is difficult to determine unambiguously, but it is preferable to select appropriately in the minimum time during which the adsorbed gas can be desorbed.

(Plasma treatment)
Adsorption gas desorption by plasma treatment utilizes ion impact desorption, and is desorbed by ejecting the adsorption gas by the momentum of ions. Further, it is considered that the adsorbed gas can be mainly desorbed by direct ejection by incident ions and ejection by ions reflected from the substrate.

  The plasma treatment in the present invention must be performed so as not to affect the semiconductor layer having the first conductivity type, as in the heat treatment described above, and a new impurity is added to the transparent conductive layer or the semiconductor having the first conductivity type. Do not adsorb to the layer. Therefore, as a gas species used for the plasma treatment, an inert gas that does not cause chemical adsorption is most preferable, and a rare gas such as He, Ne, Ar, Kr, or Xe is preferably used.

  Further, the temperature during the plasma treatment does not affect the semiconductor layer having the first conductivity type, and the semiconductor having the first conductivity type is the same as the heat treatment for reducing the physical adsorption of the rare gas. The vicinity of the film forming temperature of the layer is preferable, and the substrate temperature is preferably 100 to 400 ° C, and most preferably 200 to 300 ° C. Further, it is necessary to immediately exhaust the adsorbed adsorbed gas. It is preferable that the plasma treatment time is appropriately selected as the minimum time during which the adsorbed gas can be desorbed.

  Although the formation method of the photovoltaic element of this invention is demonstrated below, this invention is not limited by these Examples.

Example 1
In this example, a single solar cell having a nip structure similar to the configuration shown in FIG. 1 was manufactured.
Below, it demonstrates according to the procedure of formation.

Process (1)
A metal layer 102 and a transparent conductive layer 103 were formed on a 50 mm × 50 mm square stainless steel substrate 101 that had been sufficiently degreased and cleaned by using a batch type sputtering apparatus (not shown). As the material of the metal layer 102, a simple metal such as Ag, Al, Pt, Au, Ni, Ti, Cr, or Cu and an alloy thereof are used. Here, Ag having high reflectivity is used. As a material for the transparent conductive layer 103, ZnO, SnO ₂ , In ₂ O ₃ , ITO, or the like is used, but here ZnO was used. In addition, these surfaces have an uneven (texture) structure in order to cause irregular reflection of light. The film thickness was 800 nm and 200 nm, respectively.

Step (2)
Next, a ZnO film was formed as the transparent conductive layer 104 on the transparent conductive layer 103 produced by the sputtering method using the batch electrolytic deposition apparatus shown in FIG.
As the electrolytic precipitation aqueous solution 202, an aqueous solution of zinc nitrate at 80 ° C. and 0.2 mol / l to which 0.1 g / l of dextrin and 75 μmol / l of hydrogen hydrogen phthalate were added was used. Then, a current value of 7.5 mA / cm ² was applied for 10 minutes between the cathode-side substrate 203 (corresponding to the substrate 101 on which the metal layer 102 and the transparent conductive layer 103 were formed) and the anode-side counter electrode 204. Then, electrolytic deposition was performed. The film thickness was 2300 nm.

  When X-ray measurement was performed on the back reflective layer deposited up to the transparent conductive layer 104, the X-ray diffraction intensity peak ratio of the ZnO (100) plane to the ZnO (002) plane was 4.5%, ZnO (002). The ratio of the peak of the X-ray diffraction intensity of the ZnO (101) plane relative to the () plane was 10.5%. When the total reflectance and irregular reflectance at a wavelength of 800 nm were measured, the total reflectance was 92.0% and the irregular reflectance was 90.4%. The back reflective layer produced in Example 1 was ZnO (002). It was confirmed that the orientation planes other than the plane were sufficiently developed and had a high degree of texture, and were almost equivalent to the transparent conductive layer of Sample 6 in Table 1.

  Next, by using an example of a batch type semiconductor layer forming apparatus in which the plasma CVD apparatus and the desorption processing apparatus shown in FIG. 6 are combined, the semiconductor layers 105 to 108 of the single type solar cell having the nip structure of FIG. Formation was performed.

In FIG. 6, a semiconductor layer forming apparatus includes a load lock chamber 601, an n-type semiconductor layer forming chamber 602, a heat treatment chamber 603, a rare gas plasma processing chamber 604, an i-type semiconductor layer forming chamber 605, and a p-type semiconductor layer forming chamber 606. , And an unload lock chamber 607.
The chambers are separated by gate valves 608 to 613 so that the source gases are not mixed.
Each chamber includes heaters 614 to 618, gas introduction pipes 628 to 632, pressure regulating valves 633 to 637, and exhaust pumps 638 to 642 for heating the substrate from the back surface.
Further, the semiconductor layer forming chambers 602, 605, and 606 and the rare gas plasma processing chamber 604 have discharge electrodes 620 to 623 and high frequency power sources 624 to 627 for generating plasma, respectively.
On the other hand, the heat treatment chamber 603 includes a heater 619 for heating the substrate from the surface.
The substrate is attached to the substrate holder 643 so that the processing surface is downward, and can be moved on the substrate transport rail 644 by external driving.

Process (3)
The substrate formed up to the transparent conductive layer 104 is put into the n-type semiconductor layer forming chamber 602 of FIG. 6, and an n-type made of amorphous silicon (hereinafter referred to as a-Si: H) is used as the semiconductor layer having the first conductivity type. The semiconductor layer 105 was formed under the conditions shown in Table 2. An RF plasma CVD method (RFPCVD method) was used as a method for forming the semiconductor layer. The film thickness was 20 nm.

Process (4)
Next, the substrate deposited up to the n-type semiconductor layer 105 is immediately moved to the heat treatment chamber 603 in FIG. 6 and the n-type adsorbed on the transparent conductive layer 104 or the n-type semiconductor layer 105 under the conditions shown in Table 2. The process 106 for desorbing at least a part of P, which is an element that determines the above, was performed (note that Table 2 also shows the rare gas plasma processing conditions in the desorption process 106 of Example 2 described later). ). The heat treatment is performed simultaneously from both the back side and the front side of the substrate by the substrate heaters 615 and 619, and the heat treatment temperature is set to + 50 ° C. (that is, 300 ° C.) with respect to the film formation temperature of the n-type semiconductor layer 105. Until the substrate back surface temperature reached 300 ° C., the temperature was kept constant for 20 minutes.

Process (5)
Next, the desorbed substrate is moved to the i-type semiconductor layer forming chamber 605 and an i-type semiconductor layer 107 made of microcrystalline silicon (hereinafter referred to as μc-Si: H) is formed under the conditions shown in Table 2. did. Note that a VHF plasma CVD method (VHFPCVD method) was used as a film formation method of the i-type semiconductor layer, and the film thickness was 2500 nm.

Step (6)
Thereafter, the substrate formed up to the i-type semiconductor layer 107 was moved to the p-type semiconductor layer forming chamber 606, and a p-type semiconductor layer 108 made of μc-Si: H was formed under the conditions shown in Table 2. Note that an RFPCVD method was used as a method for forming the p-type semiconductor layer, and the film thickness was 15 nm. This completes the formation of the semiconductor layer.

Step (7)
Next, the substrate formed up to the p-type semiconductor layer 108 is taken out from the unload lock chamber 607 and put into a batch type sputtering apparatus (not shown) to form ITO (In) as the transparent electrode layer 109 on the p-type semiconductor layer 108. ₂ O ₃ + SnO ₂ ) was deposited to 65 nm. Thereafter, a silver paste was screen-printed as a collecting electrode 110 on the transparent electrode layer 109 to form a thin line comb-shaped electrode.

  This completes the formation of the single type solar cell having the nip structure.

Thereafter, the solar cell characteristics were measured using a pseudo solar light source with a light quantity of 100 mW / cm ^{2 in} the AM1.5 solar spectrum for the single type solar cell, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics. Asked.

  The single-type solar cell manufactured in this example was subjected to secondary ion mass spectrometry (SIMS analysis) to determine the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer. .

(Comparative Example 1)
In this example, in order to confirm the desorption effect by the heat treatment of the present invention in Example 1, P of the element that determines the n-type adsorbed on the transparent conductive layer 104 or the n-type semiconductor layer 105 in FIG. A single solar cell having a nip structure was manufactured in the same manner as in Example 1 except that the treatment 106 for removing at least a part was not performed.

  Thereafter, the solar cell characteristics were measured in the same manner as in Example 1, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics.

  Further, the SIMS analysis was performed on the single type solar cell manufactured in this comparative example, and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer was quantified.

(Comparative Example 2)
In this example, after forming the n-type semiconductor layer 105 in Example 1 at 250 ° C. as in Example 1, the substrate deposited up to the n-type semiconductor layer 105 was once cooled to 25 ° C. The substrate was moved to the heat treatment chamber 603, the heat treatment temperature was set to 50 ° C., the temperature was raised to 50 ° C. with a temperature rise curve of 10 ° C./min, and the substrate back surface temperature reached 50 ° C. and kept constant for 2 minutes. All other steps were carried out in the same manner as in Example 1 to produce a single solar cell having a nip structure.

  Thereafter, the solar cell characteristics were measured in the same manner as in Example 1, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics.

  Further, the SIMS analysis was performed on the single type solar cell manufactured in this comparative example, and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer was quantified.

(Comparative Example 3)
In this example, the heat treatment temperature in the heat treatment in Example 1 was 500 ° C., the temperature was raised to 500 ° C. with a temperature rise curve of 10 ° C./min, and the substrate was held at a constant temperature for 20 minutes after the substrate back surface temperature reached 500 ° C. All other steps were carried out in the same manner as in Example 1 to produce a single solar cell having a nip structure.

  Thereafter, the solar cell characteristics were measured in the same manner as in Example 1, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics.

  Further, the SIMS analysis was performed on the single type solar cell manufactured in this comparative example, and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer was quantified.

  Table 3 shows the measurement results of the short-circuit photocurrent density (Jsc) of the single-type solar cells fabricated in Example 1 and Comparative Examples 1 to 3 and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer. Shown in Note that the amount of impurity elements indicates a relative value when the P concentration in the substantially intrinsic i-type semiconductor layer in Example 1 is 1.

  From the results in Table 3, first, from the comparison between Example 1 and Comparative Example 1, when a back surface reflecting layer having a sufficiently developed orientation plane other than the ZnO (002) plane and having a high degree of texture is used, the transparency of FIG. By performing treatment 106 for detaching at least part of P, which is an element that determines the n-type, adsorbed on the conductive layer 104 or the n-type semiconductor layer 105, the P concentration in the i-type semiconductor layer 107 is reduced to 1. / 3 or less, and as a result, a substantially intrinsic i-type semiconductor layer can be prevented from being weakly n-typed by the influence of P, and a transparent conductive layer having a high degree of texture can be used. It was confirmed that it was possible to obtain a photovoltaic device with increased photocurrent density.

  Next, in Comparative Example 2, although the desorption treatment by heat treatment was performed, the short-circuit photocurrent density was lower than that in Example 1, and Example 1 in the i-type semiconductor layer was similar to that in Comparative Example 1. About three times as much P element was present. This is because the P adsorbed on the transparent conductive layer 104 or the n-type semiconductor layer 105 in FIG. 1 hardly desorbed because the heat treatment temperature was 50 ° C., which was lower than the optimum temperature range of the heat treatment temperature of the present invention. is there.

  Next, in Comparative Example 3, the short-circuit photocurrent density was lower than that in Example 1 although the desorption treatment by heat treatment was performed. However, the P concentration in the i-type semiconductor layer was low as in Example 1. This is because the heat treatment temperature is 500 ° C., which is higher than the optimum temperature range of the heat treatment temperature of the present invention, so that the oxygen of ZnO as the transparent conductive layer 104 is desorbed and becomes Zn rich, and the reflectivity of the back reflective layer is increased. This is thought to be due to a decline.

  From the above results, after forming the semiconductor layer having the first conductivity type on the transparent conductive layer of the present invention, at least one of the elements determining the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer. By providing a heat treatment step for detaching the portion, it is possible to prevent contamination of the element that determines the first conductivity type into the substantially intrinsic i-type semiconductor layer, thereby enabling transparent conductivity with a high degree of texture. It has been found that a good photovoltaic device with an increased photocurrent density can be obtained by making full use of the layer.

(Example 2)
In this example, a single type solar cell having a nip structure was manufactured in the same manner as in Example 1 except that the desorption process in step (4) in Example 1 was a rare gas plasma process.
The rare gas plasma processing will be described below.

  The substrate deposited up to the n-type semiconductor layer 105 in FIG. 1 is immediately moved to the rare gas plasma processing chamber 604 in FIG. 6 and adsorbed to the transparent conductive layer 104 or the n-type semiconductor layer 105 under the conditions shown in Table 2. A treatment 106 for detaching at least a part of P, which is an element that determines n-type, was performed.

Specifically, the substrate deposited up to the n-type semiconductor layer 105 was moved to the rare gas plasma treatment chamber 604 and then evacuated by the exhaust pump 640 to a pressure of 100 Pa or lower. After evacuation, helium gas is introduced as a rare gas from a gas introduction pipe 630 while being controlled by a mass flow controller (not shown) at 200 sccm, and the pressure in the rare gas plasma processing chamber 604 is controlled to 266 Pa by a pressure adjustment valve 635. While exhausting. Thereafter, high-frequency power having a frequency of 13.56 MHz and a power density of 0.5 W / cm ² was applied to the discharge electrode 621 from a high-frequency power source 625 through a matching device (not shown), and plasma treatment was performed for 5 minutes. Note that the substrate temperature during the plasma treatment was maintained at 250 ° C., which is the same temperature as the deposition temperature of the n-type semiconductor layer 105.

  For the single solar cell produced in this example, the solar cell characteristics were measured in the same manner as in Example 1, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics.

  The single-type solar cell manufactured in this example was also subjected to SIMS analysis to determine the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer.

As a result, the short-circuit photocurrent density was 30.0 mA / cm ² , and the P concentration in the i-type semiconductor layer was almost the same as in Example 1.

  From the above results, after forming the semiconductor layer having the first conductivity type on the transparent conductive layer of the present invention, at least one of the elements determining the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer. By providing a rare gas plasma treatment step that desorbs the portion, it is possible to prevent the inclusion of the element that determines the first conductivity type into the substantially intrinsic i-type semiconductor layer. It was found that a high transparent conductive layer can be used well, and a good photovoltaic device with an increased photocurrent density can be obtained.

(Example 3)
In this example, in order to verify whether or not the present invention is effective even when a photovoltaic device is formed by forming each layer continuously on a large area substrate, on a conductive band substrate having a large area. Further, a single type solar cell having the same configuration as that shown in FIG. 1 was manufactured using a roll-to-roll type film forming apparatus.
Below, it demonstrates according to the procedure of formation.

Process (1)
A stainless steel strip substrate (width 356.0 mm, length 50 m, thickness 0.15 mm) 101 sufficiently degreased and cleaned with oakite and pure water is placed in a roll-to-roll type DC magnetron sputtering apparatus (not shown) and Ag is deposited to 800 nm. Thereafter, 200 nm of ZnO was deposited to form the metal layer 102 and the transparent conductive layer 103. In addition, these surfaces have an uneven (texture) structure in order to cause irregular reflection of light.

Step (2)
Next, the substrate was taken out, and ZnO was deposited as the transparent conductive layer 104 using the roll-to-roll type electrolytic deposition apparatus shown in FIG.

  In FIG. 7, 701 is a belt-like substrate, 702 is a feed roller, 703 is a take-up roller, 704 is a transport roller, 705 is an electrolytic deposition tank, 706 is an electrolytic deposition aqueous solution, 707 is a counter electrode, 708 is a DC power source, 709. Is a pure water washing tank, 710 is pure water, 711 is a pure water shower, 712 is a drying furnace, and 713 is an infrared heater.

As the electrolytic precipitation aqueous solution 706, a zinc nitrate aqueous solution at 80 ° C. and 0.2 mol / l to which 0.1 g / l of dextrin and 75 μmol / l of hydrogen hydrogen phthalate were added was used. The electrolytic precipitation aqueous solution 706 is always sufficiently stirred by a circulation pump (not shown). Further, a zinc plate whose surface was blasted was used as the counter electrode 707, and electrolytic deposition was performed between the cathode-side substrate 701 and the anode-side counter electrode 707 at a current value of 7.5 mA / cm ² . The substrate transfer speed was 1000 mm / min, and ZnO was deposited at 2300 nm.

  Thereafter, a part of the back reflective layer deposited up to the transparent conductive layer 104 was cut out, and X-ray measurement was performed on the central portion of the back reflective layer. As a result, the ratio of the X-ray diffraction intensity peak of the ZnO (100) plane to the ZnO (002) plane was measured. Was 4.3%, and the X-ray diffraction intensity peak ratio of the ZnO (101) plane to the ZnO (002) plane was 10.1%. When the total reflectance and irregular reflectance at a wavelength of 800 nm were measured, the total reflectance was 92.1% and the irregular reflectance was 90.0%. The roll-to-roll was formed on the large area substrate of Example 3. The back reflective layer produced using a mold deposition apparatus has a sufficiently developed orientation plane other than the ZnO (002) plane and has a high degree of texture, and is almost equivalent to the transparent conductive layer of Sample 6 in Table 1. It was confirmed.

Process (3)
Next, the substrate is taken out, and a single solar cell having the nip structure of FIG. 1 is used by using a roll-to-roll type semiconductor layer forming apparatus in which the plasma CVD apparatus and the desorption processing apparatus shown in FIG. The semiconductor layers 105 to 108 were formed.

In FIG. 8, the semiconductor layer forming apparatus includes a substrate delivery chamber 801, an n-type semiconductor layer deposition chamber 802, a heat treatment chamber 803, a rare gas plasma treatment chamber 804, an i-type semiconductor layer deposition chamber 805, and a p-type semiconductor layer. The film forming chamber 806 and the substrate winding chamber 807 are mainly configured. Further, the film forming chambers are separated by a gas gate 808 so that the source gases are not mixed.
Each film formation chamber has heaters 811 to 815 for heating the substrate from the back surface, gas introduction pipes 825 to 829, pressure adjusting valves 831 to 835, and exhaust pumps 838 to 842, respectively.
Further, the semiconductor layer deposition chambers 802, 805, 806 and the rare gas plasma processing chamber 804 have discharge electrodes 817 to 820 and high frequency power sources 821 to 824 for generating plasma, respectively.
On the other hand, the heat treatment chamber 803 includes a heater 816 for heating the substrate from the surface.

  First, the belt-like substrate deposited up to the transparent conductive layer 104 is set on a bobbin disposed in the substrate delivery chamber 801, and the substrate is passed through the film formation chambers 802 to 806 through the gas gates 808 to enter the substrate take-up chamber 807. The bobbin was placed and tension was applied to the extent that it did not loosen. Note that a bobbin around which a sufficiently dried aramid protective film (width 356.0 mm, length 60 m, thickness 0.05 mm) 910 is set in the substrate winding chamber 807 and a semiconductor layer is formed in a belt shape. The protective film was wound together with the substrate.

  Next, each of the film formation chambers 802 to 806, the substrate delivery chamber 801, and the substrate take-up chamber 807 is evacuated to 100 Pa or less by the respective exhaust pumps. After introducing 100 sccm of gas and adjusting the pressure to 300 Pa by using each pressure adjusting valve, it was baked at 300 ° C. for 2 hours with each heater.

  After the heat baking, each film formation chamber 802 to 806, substrate delivery chamber 801 and substrate take-up chamber 807 is once evacuated to 100 Pa or less, and then each gas gate is supplied with 1000 sccm of hydrogen. The raw material gas shown in Table 4 was introduced from the introduction pipe at a predetermined flow rate, and the pressure was adjusted to 600 Pa by each pressure regulating valve.

  When the pressure in each film forming chamber is stabilized, the belt-like substrate is transferred at a transfer speed of 500 mm / min, and the substrate back surface temperature in the film forming space in each film forming chamber is not shown in FIG. The temperature was controlled by a heater connected to the temperature controller.

  In this embodiment, the heat treatment chamber 803 and the rare gas plasma treatment chamber 804 are used in combination in order to enhance the desorption effect on the substrate being transferred, and the desorption treatment by the heat treatment and the rare gas plasma are continuously performed. Desorption treatment was performed.

  When the temperature of the belt-shaped substrate is stabilized, high frequency power of 13.56 MHz is supplied to the discharge electrodes 817, 818, and 820 provided in the film formation chambers 802, 804, and 806, and high frequency power of 60 MHz is applied to the discharge electrode 819 provided in the film formation chamber 805. Electric power is introduced at a power density shown in Table 4 from each high-frequency power source through a matching device (not shown) to generate plasma, thereby forming an n-type semiconductor layer 105 made of a-Si: H, and a rare gas plasma treatment 106. Then, the i-type semiconductor layer 107 made of μc-Si: H and the p-type semiconductor layer 108 made of μc-Si: H were formed.

Process (4)
Next, the substrate was taken out and placed in a roll-to-roll DC magnetron sputtering apparatus (not shown), and an ITO film was deposited to 65 nm on the p-type semiconductor layer 108 to form a transparent electrode layer 109.

Process (5)
Next, the solar cell formed up to the transparent electrode layer 109 is cut into 356.0 mm × 120.0 mm (the width 356.0 mm is left as it is in the substrate transport direction 120.0 mm), and the short-circuited portion is subjected to electrolytic treatment and then transparent electrode Silver paste was screen-printed as a collecting electrode 110 on the layer 109 to form a thin line-like comb electrode.

  This completes the formation of the single type solar cell having the nip structure.

Thereafter, the solar cell characteristics were measured using a pseudo solar light source with a light quantity of 100 mW / cm ^{2 in} the AM1.5 solar spectrum for the single type solar cell, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics. Asked.

  The single-type solar cell manufactured in this example was subjected to secondary ion mass spectrometry (SIMS analysis) to determine the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer. .

(Comparative Example 4)
In this example, in order to confirm whether or not the desorption treatment of the present invention is effective even when forming a photovoltaic device by forming each layer continuously on the large area substrate in Example 3, In the same manner as in Example 3, except that the process 106 for desorbing at least a part of P, which is an element that determines the n-type adsorbed on the transparent conductive layer 104 or the n-type semiconductor layer 105 in FIG. 1, is not performed. A single type solar cell having a structure was manufactured.

  Specifically, in step (3) of the third embodiment, the heaters 812, 813, and 816 installed in the heat treatment chamber 803 and the rare gas plasma treatment chamber 804 in FIG. 8 are turned off, and the rare gas plasma treatment is performed. In the chamber, no discharge was caused.

  Thereafter, the solar cell characteristics were measured in the same manner as in Example 3, and the short-circuit photocurrent density (Jsc) was determined from the current-voltage characteristics.

  Further, the SIMS analysis was performed on the single type solar cell manufactured in this comparative example, and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer was quantified.

  Table 5 shows measurement results of the short-circuit photocurrent density (Jsc) of the single-type solar cells fabricated in Example 3 and Comparative Example 4 and the amount of impurity elements present in the substantially intrinsic i-type semiconductor layer. . Note that the impurity element amount represents a relative value when the P concentration in the substantially intrinsic i-type semiconductor layer in Example 3 is 1.

  From the results of Table 5, even when each layer is continuously formed on a large-area substrate to form a photovoltaic device, the orientation plane other than the ZnO (002) plane is sufficiently developed in the back surface reflection layer and the degree of texture. Even when a material having a high thickness is used, a process 106 for desorbing at least a part of P, which is an element that determines the n-type adsorbed on the transparent conductive layer 104 or the n-type semiconductor layer 105 in FIG. By doing so, the P concentration in the i-type semiconductor layer 107 can be suppressed to 1/3 or less, and as a result, the substantially intrinsic i-type semiconductor layer becomes weak n-type under the influence of P. It has been confirmed that a transparent conductive layer having a high degree of texture can be used and a photovoltaic device having an increased photocurrent density can be obtained.

It is typical sectional drawing which shows an example of the single type photovoltaic element of this invention. It is the schematic which shows an example of a batch type electrolytic deposition apparatus. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the reflectance in wavelength 800nm of a back surface reflection layer, and an X-ray diffraction intensity peak. It is a figure showing an example of the relationship between the X-ray diffraction intensity peak ratio of the ZnO film in a back surface reflection layer, and the irregular reflectance of a back surface reflection layer. It is a figure showing an example of the relationship between the X-ray diffraction intensity peak ratio of a ZnO film | membrane, and the short circuit photocurrent density of a photovoltaic device. It is the schematic which shows an example of the batch type semiconductor layer forming apparatus with which the plasma CVD apparatus and the desorption processing apparatus for forming the photovoltaic element of this invention became one. It is the schematic which shows an example of a roll-to-roll type electrolytic deposition apparatus. It is the schematic which shows an example of the roll-to-roll type | mold semiconductor layer forming apparatus with which the plasma CVD apparatus and the desorption processing apparatus for forming the photovoltaic element of this invention became one.

Explanation of symbols

101 Substrate 102 Metal layer 103 Transparent conductive layer 104 produced by sputtering method Transparent conductive layer 105 produced by electrolytic deposition method n-type first semiconductor layer 106 transparent conductive layer 104 or n-type first semiconductor layer 105 Treatment for desorbing at least a part of the element that determines the adsorbed n-type 107 i-type second semiconductor layer 108 p-type third semiconductor layer 109 Transparent electrode layer 110 Current collecting electrode 111 Incident light 201 Corrosion-resistant container 202 Electrodeposition aqueous solution 203 Substrate 204 Counter electrode 205 DC power supply 206 Load resistance 207 Substrate support shaft 208 Electrode support shaft 209 Substrate branch 210 Electrode branch 211 Stirrer 212 Constant temperature plate 601 Load lock chamber 602 n-type semiconductor layer formation chamber 603 Heat treatment chamber 604 Noble gas plasma treatment chamber 605 i-type half Conductor layer forming chamber 606 p-type semiconductor layer forming chamber 607 Unload lock chamber 608 to 613 Gate valve 614 to 619 Heating heater 620 to 623 Discharge electrode 624 to 627 High frequency power source 628 to 632 Gas introducing pipe 633 to 637 Pressure adjusting valve 638 to 642 Exhaust pump 643 Substrate holder 644 Substrate transport rail 701 Strip substrate 702 Delivery roller 703 Take-up roller 704 Transport roller 705 Electrodeposition tank 706 Electrodeposition aqueous solution 707 Counter electrode 708 DC power source 709 Pure water cleaning tank 710 Pure water 711 Pure water Shower 712 Drying furnace 713 Infrared heater 801 Substrate delivery chamber 802 n-type semiconductor layer deposition chamber 803 Heat treatment chamber 804 Rare gas plasma treatment chamber 805 i-type semiconductor layer deposition chamber 806 p-type semiconductor layer deposition chamber 80 Substrate winding chamber 808 a gas gate 809 belt-like substrate 810 protective films 811-816 heaters 817-820 discharge electrodes 821 to 824 high-frequency power source 825 to 829 gas introduction pipe 830 to 836 pressure regulating valve 837 to 843 exhaust pump 910 protective film

Claims (7)

  A step of forming a transparent conductive layer on the substrate; a step of forming a semiconductor layer having a first conductivity type; and at least one element for determining the first conductivity type adsorbed on the transparent conductive layer or the semiconductor layer. A step of detaching the portion by a heat treatment and / or a plasma treatment at a substrate temperature of 100 to 400 ° C., and a step of forming a substantially intrinsic second semiconductor layer on the semiconductor layer having the first conductivity type, A method for producing a photovoltaic device, comprising: a step of forming a third semiconductor layer having a conductivity type opposite to the first conductivity type in this order.   2. The method of manufacturing a photovoltaic element according to claim 1, wherein the plasma treatment is a rare gas plasma treatment using at least one of He, Ne, Ar, Kr, and Xe.   2. The method of manufacturing a photovoltaic element according to claim 1, wherein the element that determines the first conductivity type is P.   The transparent conductive layer is composed of a ZnO layer having an inclined c axis, and the X-ray diffraction intensity of the (100) plane and / or (101) plane of the ZnO layer is 0.5% or more of the diffraction intensity of the (002) plane. The method for producing a photovoltaic device according to claim 1, wherein:   2. The method for producing a photovoltaic element according to claim 1, wherein the irregular reflectance of the transparent conductive layer is 60% or more at a wavelength of 800 nm.   2. The method of manufacturing a photovoltaic element according to claim 1, wherein the transparent conductive layer is composed of two layers of a ZnO layer produced by electrolytic deposition on a ZnO layer produced by sputtering.   2. The method of manufacturing a photovoltaic element according to claim 1, wherein the substantially intrinsic second semiconductor layer is made of microcrystalline silicon and has a thickness in the range of 0.5 to 6 [mu] m.

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