JP2009033206A - Multi-layer photovoltaic element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multi-layer photovoltaic element capable of efficiently collecting energy over all wavelength ranges of incident light and having a high conversion efficiency, excellent in an open circuit voltage (hereinafter Voc), curve factor (hereinafter FF), and the like. <P>SOLUTION: Provided is a method of manufacturing a multi-layer photovolatic element having an interlayer between photovoltaic elements including a p-n junction or p-i-n junction. After a first layer whose main component is composed of indium oxide is laminated on at least one photovoltaic element interface, the interlayer is formed by laminating a second layer whose main component is composed of zinc oxide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stacked photovoltaic device having at least two power generation function units, and a method for manufacturing the same.

  Photovoltaic elements are devices that convert incident light energy into electrical energy, among which solar cells convert white light, sunlight, into electrical energy, and efficiently convert light in a wide wavelength range. The photovoltaic element. Therefore, in order to achieve high conversion efficiency, it is necessary to absorb light without waste over the entire wide wavelength region.

  As one of the means for solving the problem, a stacked photovoltaic element in which photovoltaic elements including photoactive layers having different band gaps are stacked is known. This stacked photovoltaic element has a short wavelength by arranging a photovoltaic element using a photoactive layer having a relatively large band gap on the light incident side or a photovoltaic element having a relatively thin film thickness. Long-wavelength light that has passed through the upper element by disposing a photovoltaic element using a semiconductor with a relatively small band gap or a photovoltaic element having a thick film thickness. By absorbing the light, the light is efficiently absorbed and utilized in a wide wavelength range.

  The important point here is that it is necessary to introduce into each element light in a wavelength region suitable for a photovoltaic element having photoactive layers with different band gaps. This is because the usable wavelength range of incident light differs depending on the band gap of the semiconductor used in the photoactive layer of each photovoltaic device. That is, photons having energy lower than the band gap are not absorbed by the semiconductor and cannot be used. Photons with energy larger than the band gap are absorbed, but the potential energy of electrons that can be given when electrons are excited is limited by the size of the band gap. The difference in photon energy cannot be used. Therefore, in the stacked photovoltaic element, it is important that only light in the short wavelength region is incident on the light incident side element, and only light in the long wavelength region is incident on the underlying element.

As one solution, a method is known in which an intermediate layer is provided between the upper and lower photovoltaic elements and used as a reflective layer. For example, Patent Document 1 or Non-Patent Document 1 discloses a method in which a conductive layer that reflects light having a short wavelength and transmits light having a long wavelength is provided between elements. In Patent Document 2, the thickness of the selective reflection layer is adjusted, and the peak of the reflectance is adjusted to the maximum wavelength of the spectral sensitivity of the light incident side photovoltaic element to adjust the current of the light incident side photovoltaic element. A method of increasing the value is disclosed. Furthermore, in Patent Document 3, the selective reflection layer has a laminated structure, and the characteristics of the short wavelength region that the upper photoelectric conversion layer easily absorbs have high reflectance, and the lower photoelectric conversion layer easily absorbs the long wavelength region. Discloses a method of improving the efficiency of the stacked photovoltaic element by lowering the reflectance and transmitting it. All of them use a dielectric layer such as SnO ₂ , ZnO, ITO, etc. as a selective reflection layer, and light of a short wavelength that is originally intended to be absorbed by the photovoltaic element on the incident light side is absorbed by the lower photovoltaic element. The purpose is to increase the conversion efficiency of the photovoltaic element on the incident light side.

JP-A 63-77167 JP-A-2-237172 JP 2001-308354 A Kenji Yamamoto, “Thin Film Polycrystalline Silicon Solar Cell”, Applied Physics, Applied Physics Society, May 2002, Vol. 71, No. 5, p. 524-527

  As described above, as a result of various studies on the intermediate layer, an intermediate layer that is good to some extent is obtained. However, there are still problems to be solved in order to realize further improvement in optical characteristics and electrical characteristics, or improvement in consistency with a semiconductor layer, and improvement in deposition rate.

  For example, when the reflective layer that is a conductor is provided as an intermediate layer, the following problems occur.

  First, when fabricating a photovoltaic device having a large area, for example, in an element in which unit elements as shown in FIG. Defects are formed. Here, in FIG. 1, 100 is a stacked photovoltaic element, 101 is a substrate, 102 is a second photovoltaic element, 103 is a zinc oxide layer, 104 is a first photovoltaic element, and 105 is a transparent electrode. The conductive layer 106 is a short circuit in the second photovoltaic element, and 107 is a short circuit in the first photovoltaic element. Defect formation that is unavoidable because of its large area results in a decrease in characteristics due to a decrease in shunt resistance and a decrease in fill factor (FF). As an effective means for this, there is usually a method (passivation) in which a photovoltaic element is immersed in an electrolytic solution and a part of the conductive layer outside the electrical defect portion is selectively removed by passing a current. . However, in the case of the type of photovoltaic element laminated with the lower photovoltaic layer, the intermediate layer, the upper photovoltaic layer, and the conductive layer on the substrate, the conductive layer 105 corresponding to the defect portion 107 of the upper layer can be removed. However, the intermediate layer 103 corresponding to the defect portion 106 in the lower layer cannot be removed. For this reason, a short-circuit current flows through a defect in the lower layer, which causes a decrease in the electromotive force of the lower photovoltaic element. In particular, the intermediate layer must maintain a certain layer thickness as a reflective layer, the consistency with the semiconductor layer in contact with both sides and the series resistance must also be taken into account, so the adjustment of the resistivity of the material does not remain, For this reason, the short circuit current cannot be prevented from spreading in the intermediate layer. In addition, since a junction with an intermediate layer made of a different material is generated between a plurality of photovoltaic elements, characteristic deterioration accompanying FF reduction cannot be avoided. Furthermore, when a plurality of layers are inserted for the purpose of preventing a decrease in shunt resistance, the junction is further increased, so that the interface problem is further increased.

  As described above, conventionally, even if an intermediate layer is introduced as a selective reflection layer in order to increase the photocurrent, there is a problem that a photovoltaic element having a low electromotive force is obtained as a result.

  Further, in the configuration disclosed in Patent Document 3, although the light reflection and transmission characteristics can be satisfied, it has a good connection with the photovoltaic element and has an adverse effect on the photovoltaic element when forming the intermediate layer. It was found to be insufficient to prevent In order to obtain sufficient characteristics, it is necessary to solve the following technical items.

  For the connection between the intermediate layer and the underlying semiconductor layer, it is necessary to have good ohmic contact with the underlying semiconductor layer. In addition, regarding the damage to the underlying semiconductor layer during the formation of the intermediate layer, it is necessary that there is little physical modification such as chemical modification such as oxidation of the underlying semiconductor layer and ion damage. Furthermore, it is necessary to devise that the shunt current flows in the lateral direction through the intermediate layer so that it has an appropriate resistivity and film thickness, or hardly flows in the lateral direction.

  In view of the above problems, an object of the present invention is to provide a stacked photovoltaic element having high conversion efficiency by obtaining a large photocurrent without causing a decrease in electromotive force.

  In addition, the present invention can efficiently collect energy over the entire wavelength range of incident light, and has a high conversion efficiency such as an open circuit voltage (hereinafter referred to as Voc) and a fill factor (hereinafter referred to as FF). An object of the present invention is to provide an electromotive force element and a manufacturing method thereof.

  The present invention has been made through extensive studies to solve the above-described problems, and has the configuration described below.

That is, the first aspect of the present invention is a photovoltaic element formed by laminating unit photovoltaic elements each composed of a plurality of pn junctions or pin junctions in at least one place between the unit photovoltaic elements. A zinc oxide layer is disposed, and the resistivity of the zinc oxide layer is different in the layer thickness direction.
Furthermore, in the zinc oxide layer, the resistivity of zinc oxide on the side in contact with the p layer is larger than the resistivity of zinc oxide on the side in contact with the n layer.
Furthermore, in the zinc oxide layer, the resistivity of zinc oxide continuously decreases from the side in contact with the p layer toward the side in contact with the n layer.
In the zinc oxide layer, the resistivity of zinc oxide is preferably 2 × 10 ⁰ Ωcm or more and 5 × 10 ³ Ωcm or less.
Moreover, in the zinc oxide layer, a high portion of resistivity zinc oxide is desirably 5 × 10 ² Ωcm or more 5 × 10 ³ Ωcm or less.
Among the plurality of unit photovoltaic elements of the present invention, at least one unit photovoltaic element has a pin-type junction, and amorphous Si: H is suitably used for the i-type layer.
Moreover, at least one unit photovoltaic element among the plurality of unit photovoltaic elements of the present invention has a pin-type junction, and microcrystalline Si is suitably used for the i-type layer.
Furthermore, at least one unit photovoltaic element among the plurality of unit photovoltaic elements of the present invention has a pin-type junction, and monocrystalline or polycrystalline Si is suitably used for the i-type layer.

According to a second aspect of the present invention, there is provided a method of manufacturing a stacked photovoltaic element having an intermediate layer between photovoltaic elements including a PN junction or a PIN junction, and is mainly provided at an interface of at least one photovoltaic element. The intermediate layer is formed by laminating a first layer composed of indium oxide and then laminating a second layer composed mainly of zinc oxide.
Further, the second layer is formed so that the film thickness of the second layer is larger than the film thickness of the first layer.
The first layer is formed to have a thickness of 1 nm to 50 nm.
Further, the second layer is formed so that the formation speed of the second layer is higher than the formation speed of the first layer.
In addition, the second layer is formed so that the formation temperature of the second layer is lower than the formation temperature of the first layer.

According to a third aspect of the present invention, there is provided a stacked photovoltaic element having an intermediate layer between photovoltaic elements including a pn junction or a pin junction, wherein the intermediate layer is provided at an interface of at least one photovoltaic element. It is characterized in that a second layer whose main component is made of zinc oxide is stacked on a first layer whose main component is made of indium oxide.
In addition, the thickness of the second layer is larger than the thickness of the first layer.
The thickness of the first layer is 1 nm to 50 nm.
Furthermore, the transmittance of the second layer at a wavelength of 800 nm is higher than the transmittance of the first layer at a wavelength of 800 nm.

  According to the first aspect of the present invention, since light absorption is performed without waste over the entire wavelength range of incident light, high conversion efficiency is obtained, and the short-circuit current flowing through the electrical defect portion is kept low. It is possible to provide a stacked photovoltaic device that realizes high conversion efficiency by improving the bonding from the zinc oxide layer to the semiconductor layer.

  Further, according to the second and third aspects of the present invention, energy can be efficiently collected over the entire wavelength region of incident light, and the open circuit voltage (hereinafter referred to as Voc), the fill factor (hereinafter referred to as FF), etc. An excellent effect that a stacked photovoltaic element having a high conversion efficiency and a method for manufacturing the same can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments.

  In the following description, a solar cell in which two photovoltaic elements are stacked will be described as an example of the stacked photovoltaic element according to the present invention. However, the present invention is not limited to this, and the photovoltaic cell is not limited thereto. The present invention can also be applied when three or more elements are stacked.

  FIG. 3 is a schematic view showing a cross-sectional structure of a two-layered photovoltaic element 300 according to one embodiment of the first invention. A second photovoltaic element 302, a second zinc oxide layer 303, a first zinc oxide layer 304, a first photovoltaic element 305, and a transparent electrode 306 are formed on a substrate 301 made of metal or the like on which a reflective layer is stacked. They are stacked in order. The semiconductor constituting the photoactive portion of the first photovoltaic element 305 and the second photovoltaic element 302 is a semiconductor in which the first photovoltaic element 305 has a larger band gap than the second photovoltaic element 302. The first photovoltaic element 305 is designed to absorb light in the short wavelength region, and the second photovoltaic element 302 is designed to absorb light in the long wavelength region. The first zinc oxide layer 304 and the first photovoltaic element 305 have different refractive indexes, causing multiple reflection by adjusting the layer thickness, and effectively increasing the reflectance in the short wavelength region. This is possible and has the effect of increasing the light absorption amount of the first photovoltaic element 305. The second zinc oxide layer 303 is designed to have a higher resistivity than the first zinc oxide layer 304.

  FIG. 4 schematically shows the power generation operation of the stacked photovoltaic element according to the first aspect of the present invention. The electrical defects present in the first photovoltaic element act as a short circuit path for the current. Among these, the electrical defects 402 in the first photovoltaic element 305 and the electrical defects in the second photovoltaic element 302 are among others. When the mechanical defect 403 is located at a close distance, the transparent electrode 306 is removed by the shunt passivation process performed after the stacked photovoltaic element is manufactured, so that the characteristics of the photovoltaic element are not deteriorated. On the other hand, when the electrical defect 402 and the electrical defect 401 are at a distance from each other, the shunt passivation process is not sufficiently performed, which may cause deterioration of characteristics. However, although the first zinc oxide layer 304 having a low resistivity is formed on the substrate-side surface of the first photovoltaic element 305, the spread of the short-circuit current in the lateral direction is not possible due to the thin layer thickness. There is little, and it does not lead to characteristic deterioration.

  Next, since the zinc oxide layer, which is a conductive layer, is present around the electrical defect present in the second photovoltaic element 302, the electrical defect is a short circuit of the photovoltaic element during power generation. work. However, since the second zinc oxide layer 303 having a high resistivity is formed on the surface (upper layer surface) of the second photovoltaic element 302, the spread of the short-circuit current in the lateral direction is small and the resistance is further increased. It spreads through the first zinc oxide layer 304 having a low rate. On the other hand, since the layer thickness of the first zinc oxide layer 304 and the second zinc oxide layer 303 overlapped with each other is almost limited from the function as the selective reflection layer, a combination of high resistivity and low resistivity is also obtained here. Thus, the spread of the short circuit current can be effectively prevented.

  In addition, the electrical polarity of each joint surface of the second photovoltaic element, the second and first zinc oxide layers, and the first photovoltaic element that are sequentially stacked is, for example, as shown in FIG. (N−) second zinc oxide layer 202 having the lowest carrier concentration, (n +) first zinc oxide layer 203 having the highest carrier concentration, and n-type semiconductor layer of the first photovoltaic device having the highest carrier concentration (n ++). The structure is n− / n + / n ++ / stacked in the order of 204. Here, in FIG. 2, 201 is a substrate, 202 is a second zinc oxide layer exhibiting n-type electrical characteristics, 203 is a first zinc oxide layer exhibiting n + -type electrical characteristics, and 204 is n ++-type electrical characteristics. The n-type semiconductor layer of the first photovoltaic element exhibiting characteristics, 205 is a transparent electrode, 206 is a second photovoltaic element, 207 is a laminated zinc oxide layer, and 208 is a first photovoltaic element. An element is shown.

  The n-type zinc oxide layer can increase or decrease the carrier concentration in the bulk depending on the manufacturing conditions. Furthermore, although the reason is not clearly clarified, the carrier concentration of the n-type zinc oxide layer is changed from the p-type semiconductor layer side of the second photovoltaic element to the n-type semiconductor of the first photovoltaic element. The tendency to increase or decrease stepwise or continuously toward the layer side is that the increase / decrease tendency of the carrier concentration of the same polarity is determined in one direction including the n-type semiconductor layer of the first photovoltaic element. It seems that the connection at the junction is good, and it is possible to efficiently recover the photogenerated carrier.

The zinc oxide layer, which is an intermediate layer used here, has a higher resistivity than the zinc oxide layer, which has made remarkable progress in reducing resistance in recent years. Both the first zinc oxide layer and the second zinc oxide layer are used. It is preferably in the range of 2 × 10 ⁰ Ωcm to 5 × 10 ³ Ωcm. If it exists in this range, it will be thought that carrier concentration becomes smaller than the n-type semiconductor layer of a 1st photovoltaic element, and a junction part is improved as a result. On the other hand, the portion having a high resistivity zinc oxide, 5 × 10 ² Ωcm or more 5 × 10 ³ Ωcm will diffuse a short-circuit current at unless within the layer the following ranges, believed to cause resulting properties decrease It is done.

  The zinc oxide layer preferably transmits 50% or more of light of 800 nm. When considering the spectrum of sunlight, the wavelength range that can be used effectively is approximately 300 nm to 1200 nm, short wave light is absorbed by the cells above the zinc oxide layer, and long wave light is effective as the zinc oxide layer. It is preferable that the transmittance at 800 nm, which is a guide for long wavelengths, is 50% or more.

  Next, the stacked photovoltaic elements according to the second and third aspects of the present invention will be described.

  First, the intermediate layer which is a characteristic part of the second and third aspects of the present invention will be described. The stacked photovoltaic elements according to the second and third aspects of the present invention are formed by stacking a plurality of photovoltaic elements including pn junctions or pin junctions, and the main component is oxidized at at least one photovoltaic element interface. After laminating the first layer made of indium, the second layer whose main component is made of zinc oxide is laminated to form an intermediate layer, which has the following effects. The configuration and each component of the stacked photovoltaic elements according to the second and third aspects of the present invention will be described later.

  By forming the intermediate layer having the above-described configuration, it is possible to prevent a decrease in Voc and FF and to have excellent characteristics even under long-term use. First, in the case of an intermediate layer in which only zinc oxide was formed on the photovoltaic device interface, there was a tendency for Voc and FF to decrease, depending on the zinc oxide formation conditions, resistivity, thickness, and the like. The above phenomenon is not noticeable when a photovoltaic element is formed on zinc oxide. For example, in the case where a photovoltaic element is formed on a reflective layer with a substrate type photovoltaic element, it is conceivable to use zinc oxide as the reflective layer. In such a case, Voc, FF, etc. Since there is no particular deterioration in the characteristics, it is considered that the characteristics are deteriorated by the process of forming zinc oxide on the photovoltaic element interface. This is formed in a reducing atmosphere when a semiconductor is formed on zinc oxide, whereas it is formed in an oxidizing atmosphere when zinc oxide is formed on the photovoltaic device interface. Is considered to be related. That is, when zinc oxide is formed on the photovoltaic device interface, oxygen in the zinc oxide is deprived by atoms on the photovoltaic device interface and the semiconductor is oxidized, so that the photovoltaic device and the zinc oxide This is thought to be caused by creating a mutation layer at the interface.

  This tendency was further observed when oxygen or moisture was introduced during the formation of zinc oxide. Further, when oxygen ions are generated such as when a film is formed by sputtering or the like, ion damage is given to the interface of the photovoltaic element, which further causes deterioration of characteristics. This phenomenon was particularly prominent when deposited on a p-layer sensitive to Voc characteristics.

  On the other hand, in the case of an intermediate layer in which a layer mainly composed of indium oxide is formed on the photovoltaic device interface, the shunt resistance is reduced, although it depends on the formation conditions, the doping amount of tin, resistivity, thickness, etc. And the tendency for Voc and FF to fall was recognized. This is probably because indium oxide has a generally lower resistivity than zinc oxide, so that a leakage current flowing in the lateral direction in the intermediate layer is generated and the shunt resistance is lowered. Indium oxide is weaker in a reducing atmosphere than zinc oxide, and when a photovoltaic device is formed on indium oxide, it is considered that indium is precipitated, resulting in deterioration of characteristics and long-term reliability. .

  Therefore, when the second layer whose main component is zinc oxide is formed after the first layer whose main component is made of indium oxide is formed on the photovoltaic device interface, the decrease of Voc and FF is particularly reduced. I couldn't see it. Although the detailed reason is unknown, it is thought that this is because the interface between the first layer and the photovoltaic element is well formed. Further, if the resistance and film thickness of the first layer are appropriate, it is difficult for a lateral leakage current to flow, and if the second layer is appropriately thick, an increase in photocurrent can be expected.

  The first layer preferably has a high resistance so that a lateral leakage current does not easily flow, and preferably has a moderately thin film thickness. In addition, the photovoltaic element is often attached at a high temperature. If the high temperature continues, diffusion of indium occurs, leading to deterioration of characteristics or deterioration of long-term reliability. Therefore, the first layer should be appropriately thin. good. From the above viewpoint, the thickness of the first layer whose main component is indium oxide is preferably 1 nm to 50 nm, more preferably 3 nm to 40 nm, and most preferably 5 nm to 30 nm. It is as follows.

  On the other hand, as the intermediate layer, the larger the film thickness, the greater the effect of reflecting light to the upper photovoltaic element, so that the second layer has a larger film thickness than the first layer. It is preferable to form.

  The resistivity of the first layer is preferably smaller than the resistivity of the second layer. In any layer, the average transmittance of visible light is preferably 80% or more, and in particular, the transmittance at 800 nm on the long wave side is preferably 80% or more. In addition, the transmittance of the second layer at a wavelength of 800 nm is preferably higher than that of the first layer.

  As described above, the second and third aspects of the present invention have one major feature in that at least two layers of oxide films having different characteristics are functionally separated and optimally designed according to their characteristics. It is.

  In addition, since the intermediate layer needs to have a certain thickness, the faster the formation speed, the shorter the tact time, which is advantageous in terms of cost, but the characteristics are likely to deteriorate. When the first layer is formed at a low speed, the damage is less and good interface characteristics can be obtained. Even if the second layer is formed at a high speed after the first layer is formed at a low speed, the characteristics are not deteriorated, so that the formation speed of the second layer is higher than the formation speed of the first layer. It is preferable to form.

  In addition, since indium easily diffuses, the temperature after the first layer is preferably as low as possible. Further, since indium oxide has a low transmittance when deposited at a low temperature, it needs to be deposited at a certain high temperature. On the other hand, since zinc oxide has a higher transmittance when deposited at a low temperature, it leads to an improvement in Jsc. Further, when the zinc oxide layer is formed at a high temperature, stress is likely to be generated, and it is likely to cause peeling at the intermediate layer. Therefore, it is preferable to form the second layer so that the formation temperature is lower than the formation temperature of the first layer. The formation temperature of the first layer is preferably 150 ° C. or more and 300 ° C. or less, and the formation temperature of the second layer is preferably 50 ° C. or more and 250 ° C. or less. Further, the formation temperature of the second layer is preferably lower than the formation temperature of the first layer, more preferably 40 ° C. or more.

  Next, the configuration of the stacked photovoltaic element according to the second and third aspects of the present invention will be described.

  FIG. 8 is a schematic view schematically showing a cross-sectional structure of an embodiment of the stacked photovoltaic element according to the second and third aspects of the present invention. As shown in the figure, a light reflecting layer 802, a second photovoltaic element 803, an intermediate layer 806 (a first layer 804 whose main component is indium oxide, and a main component are formed on a conductive substrate 801 such as metal. A second layer 805 made of zinc oxide), a first photovoltaic element 807, and a transparent electrode 808 are sequentially laminated. The semiconductor constituting the photoactive portion of the first photovoltaic element 807 and the second photovoltaic element 803 has a band gap that is greater in the first photovoltaic element 807 than in the semiconductor of the second photovoltaic element 803. By constituting the semiconductor with a large semiconductor or making the photoactive portion thin, the first photovoltaic element 807 absorbs light in the short wavelength region and the second photovoltaic element 803 absorbs light in the long wavelength region. Designed to. The intermediate layer 806 has an effect of reflecting a part of light and increasing the light absorption amount of the first photovoltaic element 807. The intermediate layer 806 may be formed uneven.

  FIG. 7 is a schematic view schematically showing a method for manufacturing a stacked photovoltaic element according to the second aspect of the present invention, and shows a case where the stacked photovoltaic element shown in FIG. 8 is formed.

  In FIG. 7, as shown in FIG. 7A, a layer 703 whose main component is indium oxide is first deposited on the substrate 700, the reflective layer 701, and the second photovoltaic element 702 formed. Next, as shown in (b), a layer 704 whose main component is made of zinc oxide is deposited. Then, as shown in (c), a first photovoltaic element 706 is deposited. Thereafter, as shown in (d), a transparent electrode is deposited. In the manufacturing order as described above, a stacked photovoltaic device having an intermediate layer 705 (a layer 703 whose main component is made of indium oxide and a layer 704 whose main component is made of zinc oxide) at the interface of the photovoltaic element. The power element layers are deposited.

  FIG. 9 is a schematic view schematically showing a cross-sectional structure of a stacked photovoltaic element in another embodiment. As shown in the figure, a transparent electrode 908, a first photovoltaic element 907, an intermediate layer 906 (a first layer 904 whose main component is indium oxide, and a main layer are formed on a substrate 901 made of a transparent insulating plate such as glass. The component is composed of a second layer 905 made of zinc oxide.), A second photovoltaic element 903, and a conductive light reflecting layer 902 are sequentially laminated. In this case, light incidence is performed from the substrate 901 side which is a light-transmitting insulating substrate. The intermediate layer 906 may be formed uneven.

  Next, each component of the stacked photovoltaic element according to the present invention will be described.

[substrate]
The material constituting the substrate used for the stacked photovoltaic element of the present invention may be either a conductive material or an insulating material, regardless of the type. Examples of the conductive material include plated steel plates, NiCr, stainless steel, Al, Cr, Mo, Au, Nb, Ta, V, metals such as Ti, Pt, Pb, and Sn, or alloys thereof. Examples of the insulating material include synthetic resins such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, and polyamide, or glass, ceramics, and paper. In particular, stainless steel is suitably used as the metal substrate, and glass, ceramics, and polyimide are suitably used as the insulating substrate. Further, when light is incident from the substrate side, a translucent insulating substrate is used, and glass is particularly preferably used.

  The surface shape of the substrate may be a smooth surface or a textured shape having an uneven surface with a peak height of 0.1 to 1.0 μm at the maximum. For example, one method for texturing the surface of a substrate with stainless steel is to etch the surface using an acidic solution.

  The thickness of the substrate is appropriately determined so that each layer can be laminated in a predetermined manner so that a photovoltaic element can be formed in a predetermined manner. However, when flexibility as a photovoltaic element is required, It is only necessary to make it as thin as possible within the range where the above functions are sufficiently exhibited. However, the thickness is usually 10 μm or more from the viewpoint of manufacturing and handling the substrate and from the viewpoint of mechanical strength.

[Reflective layer]
For the reflective layer used in the stacked photovoltaic element of the present invention, a metal having high reflectivity from visible light to near infrared, for example, a metal such as Ag, Al, Cu, or a deposited film of these alloys is used. It is preferable to form by a method such as a vacuum deposition method, a sputtering method, or an electrolytic deposition method from an aqueous solution. A suitable thickness of the reflective layer is 10 nm to 5000 nm. Further, it is preferable that the surface is uneven in order to cause irregular reflection. In addition, it is desirable to provide the reflection layer with a reflection increasing layer in order to increase the amount of light reflected.

Examples of the constituent material of the reflection increasing layer include ZnO, SnO ₂ , In ₂ O ₃ , ITO, TiO ₂ , CdO, Cd ₂ SnO ₄ , Bi ₂ O ₃ , MoO ₃ , and Na _x WO ₃ . The reflection enhancement layer is preferably formed by using these materials by a method such as a vacuum deposition method, a sputtering method, an electrolytic deposition method, a CVD method, a spray method, a spin-on method, or a dipping method. The optimum thickness of the reflection increasing layer varies depending on the refractive index inherent to the material used, but 50 nm to 10 μm is preferable as the range of the layer thickness. Moreover, it is preferable that the surface of the reflection increasing layer is uneven in order to scatter light. For example, in the sputtering method, irregularities based on crystal grain boundaries are generated depending on the manufacturing conditions.

[Photovoltaic layer (photovoltaic element)]
The semiconductor used in the stacked photovoltaic device of the present invention includes group IV, group III-V, group II-VI, group I-III-VI ₂ single crystal, polycrystal, microcrystal, and amorphous. Used. Group IV is C, Si, Ge, and alloys thereof, Group III-V is AlAs, AlSb, GaN, GaP, GaAs, GaSb, InP, InAs, Group II-VI is ZnSe, ZnS, ZnTe, CdS. , CdSe, CdTe, Cu ₂ S, I-III-VI ₂ group includes CuInSe _{2 and the} like. In particular, a silicon-based semiconductor is preferably used. The form is preferably single crystal, polycrystal, microcrystal, or amorphous.

  The photovoltaic layer used in the stacked photovoltaic element of the present invention includes a pn junction and a pin junction.

  The stacked photovoltaic element of the present invention is configured by stacking at least two photovoltaic layers. Each photovoltaic layer can be composed of semiconductors of different materials or the same material, but the shorter the wavelength, the easier it is to absorb light. A configuration in which a photovoltaic layer using a material that easily absorbs light is disposed, and then a photovoltaic layer that uses a material that easily absorbs long wavelengths is preferably used.

[Zinc oxide layer]
An intermediate layer made of a zinc oxide layer is provided at least at one position between the photovoltaic layers (unit photovoltaic elements) of the stacked photovoltaic element of the first aspect of the present invention.

  Examples of the method for forming the zinc oxide layer of the present invention include a vacuum deposition method, a DC magnetron sputtering method, an RF magnetron sputtering method, an electrolytic deposition method, an electroless plating method, a CVD method, an MOCVD method, a spray method, a spin-on method, It is preferable to form by a method such as a dipping method or a sol-gel method. At that time, Al, B, Ga, In, and the like are generally known as dopants as substances that change the resistivity. In addition, tetravalent metals such as Si, Ge, Ti, and Zr are also known. In the case of a general vacuum deposition method or sputtering method, these dopants may be sintered together with zinc oxide (a target or the like) in a desired amount in advance.

  The zinc oxide layer has high reflection in the short wavelength region with reference to the wavelength λm at which the spectral characteristic of the second photovoltaic element is maximized in order to perform energy conversion without waste over the entire wavelength region of incident light, And it changes so that it may become low in the long wavelength region. Further, the transmittance of the film is desirably 80% or more so as not to lose incident light.

In addition, the zinc oxide layer of the present invention has its resistivity changed in the layer thickness direction in order to prevent deterioration of device characteristics due to the shunt, which is a conventional problem, while maintaining the function as a selective reflection film. Moreover, the preferable range of the resistivity is 5 × 10 ³ Ωcm to 2 × 10 ⁰ Ωcm, and the high resistance portion is desirably 5 × 10 ² Ωcm or more and 5 × 10 ³ Ωcm or less. The layer thickness is preferably in the range of 0.2 μm to 2 μm in consideration of the reflectivity, series resistance, and uneven shape.

[Middle layer]
The intermediate layer used in the stacked photovoltaic elements of the second and third aspects of the invention includes a layer whose main component is made of indium oxide and a layer whose main component is made of zinc oxide. The layer whose main component is indium oxide may contain a trace amount of other components, for example, may contain Mg, Zn, Sn, Sb and the like.

  The layer whose main component is made of zinc oxide may contain a trace amount of other components, for example, Al, Sn, In, Fe, Ga, Co, Si, Ti, Ge, Sb, etc. .

Further, the intermediate layer may further include a layer made of SnO ₂ , TiO ₂ , CdO, Cd ₂ SnO ₄ , Bi ₂ O ₃ , MoO ₃ , Na _x WO ₃ or the like.

  As a method for forming the intermediate layer, methods such as a vacuum deposition method, a sputtering method, an electrolytic deposition method, a CVD method, a spray method, a spin-on method, and a dipping method are suitable.

  Thereafter, irregularities can be provided by wet etching, dry etching, or the like. At this time, an intermediate layer is formed by forming a layer whose main component is zinc oxide after forming a layer whose main component is composed of indium oxide at the semiconductor interface.

[Transparent electrode]
Examples of the transparent electrode used in the stacked photovoltaic element of the present invention include indium oxide, tin oxide, indium tin oxide, and zinc oxide. Sputtering method, vacuum deposition method, chemical vapor deposition method, ion plating method , Ion beam sputtering, ion beam sputtering, and the like. Further, it can also be produced by an electrodeposition method or an immersion method from an aqueous solution composed of a metal ion with a nitrate group, an acetate group, an ammonia group, or the like. The thickness of the transparent electrode is preferably deposited to a film thickness that satisfies the condition as an antireflection film.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, the stacked photovoltaic element of the present invention has two photovoltaic layers (unit photovoltaic elements), a reflective layer from the substrate side, a photovoltaic element made of microcrystalline silicon, An embodiment of a solar cell in which a photovoltaic element made of an intermediate layer and amorphous silicon is sequentially formed will be described. However, the present invention is not limited to these, and the photovoltaic element is laminated as necessary. It is also possible to increase the number of.

[Example 1]
In this example, the second photovoltaic element 302 is a pin type photovoltaic element in which the i layer is intrinsic microcrystalline Si, and the first photovoltaic element 305 is the pin in which the i layer is intrinsic amorphous Si: H. It is the example which produced the lamination type photovoltaic element (refer FIG. 3) based on 1st this invention using a type photovoltaic device and a zinc oxide as an intermediate | middle layer.

The substrate 301 is made of flat stainless steel (SUS430), generally called BA finish, in a shape of 45 mm x 45 mm in length and width of 0.15 mm, and installed in a commercially available DC magnetron sputtering apparatus (not shown). The gas was exhausted until the pressure was 10 ⁻³ Pa or less.

Thereafter, argon gas was supplied at 30 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. The substrate was not heated, and a DC power of 120 W was applied to a 6 inch φ aluminum target to form a 70 nm aluminum thin film in 90 seconds. Subsequently, the substrate temperature was heated to 200 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 500 W DC power was applied for 30 minutes, and a zinc oxide reflective layer of about 500 nm was deposited.

  FIG. 5 is a schematic view showing an embodiment of an apparatus suitable for producing a semiconductor layer of a stacked photovoltaic element according to the present invention. In FIG. 5, the deposited film forming apparatus 500 includes a load chamber 501, an n-type layer RF chamber 502, a microcrystalline silicon i-type layer chamber 503, an amorphous silicon i-type layer RF chamber 504, a p-type layer RF chamber 505, and an unload. The chamber 506 is mainly configured. The chambers are separated by gate valves 507, 508, 509, 510, and 511 so that the source gas is not mixed.

  The microcrystalline silicon i-type layer chamber 503 includes a substrate heating heater 512 and a plasma CVD chamber 513. The RF chamber 502 includes an n-type layer deposition heater 514 and an n-type layer deposition chamber 515, the RF chamber 504 includes an i-type layer deposition heater 516 and an i-type layer deposition chamber 517, and the RF chamber 505. Has a p-type layer deposition heater 518 and a p-type layer deposition chamber 519. The substrate is attached to the substrate holder 521 and moves on the rail 520 by a roller driven from the outside. In the plasma CVD chamber 513, microcrystals are deposited. For the microcrystal, a microwave plasma CVD method or a VHF plasma CVD method is used.

  Using such a deposited film forming apparatus, the second photovoltaic element 302 has a layer of intrinsic microcrystalline Si or less of the pin type photovoltaic element under the predetermined film forming conditions shown in Table 1. In this way, a film was formed.

  First, the substrate 301 having a reflective layer is set on the substrate holder 521 and set on the rail 520 of the load chamber 501. Then, the inside of the load chamber 501 is evacuated to a degree of vacuum of several hundred mPa or less.

  Next, the gate valve 507 is opened, and the substrate holder 521 is moved to the n-type layer deposition chamber 515 of the chamber 502. With the gate valves 507, 508, 509, 510, and 511 closed, an n-type layer is deposited to a predetermined layer thickness with a predetermined source gas. After exhausting sufficiently, the gate valve 508 is opened, the substrate holder 521 is moved to the deposition chamber 503, and the gate valve 508 is closed.

  A substrate is heated to a predetermined substrate temperature by a heater 512, a predetermined amount of a predetermined source gas is introduced, a predetermined degree of vacuum is set, a predetermined microwave energy or VHF energy is introduced into the deposition chamber 513, and plasma is generated. Then, a microcrystalline silicon i-type layer is deposited on the substrate to a predetermined layer thickness. The chamber 503 is sufficiently evacuated, the gate valves 509 and 510 are opened, and the substrate holder 521 is moved from the chamber 503 to the chamber 505.

  After the substrate holder 521 is moved to the p-type layer deposition chamber 519 of the chamber 505, the substrate is heated to a desired temperature by the heater 518. A source gas for p-type layer deposition is supplied to the deposition chamber 519 at a predetermined flow rate, RF energy is introduced into the deposition chamber 519 while maintaining a predetermined degree of vacuum, and the p-type layer is deposited to a desired layer thickness.

  After exhausting the deposition chamber 519 sufficiently as described above, the gate valve 511 is opened and the substrate holder 521 is moved to the unload chamber 506. All the gate valves are closed and nitrogen gas is sealed in the unload chamber 506 to cool the substrate temperature. Thereafter, the takeout valve of the unload chamber 506 is opened, and the substrate holder 521 is taken out.

Next, the substrate produced from the substrate holder 521 to the second photovoltaic element 302 is removed and placed on the substrate holder 601 of the DC magnetron sputtering apparatus 600 shown in FIG. 6 to form a zinc oxide layer. It exhausted until it became 10 < ^-3 > Pa or less.

The substrate holder 601 is electrically insulated, and the photovoltaic element as a sample can be brought into a floating state. Thereafter, the pressure was maintained at 2 × 10 ⁻² Pa while supplying argon gas at 50 sccm, oxygen gas, and vaporized H ₂ O gas from the gas introduction pipe 602 at 0.1 to 5 sccm according to Table 2. Subsequently, the substrate holder 601 is heated by the heater 603 so that the substrate temperature becomes 150 ° C., and 500 W DC power is applied to the Al-doped 6 inch φ zinc oxide (ZnO) target 604 from the DC power source 605 for 10 minutes. A second zinc oxide layer 303 having a layer thickness of about 0.5 μm was deposited. An enclosure is installed around the target 604 as an earth shield 606, which prevents plasma diffusion and contributes to stable discharge. At the same time, a quartz substrate of 45 mm × 45 mm was placed on the substrate holder, the same zinc oxide layer was deposited, and the electrical characteristics were measured.

  Next, the first zinc oxide layer 304 is again laminated under the conditions of A to J in Table 2 on each substrate on which the second zinc oxide layer 303 having the A to J recipe in Table 2 is deposited, so that a total of 100 is obtained. Individual samples were made. At the same time, a quartz substrate of 45 mm × 45 mm was placed on the substrate holder, the same zinc oxide layer was deposited, and the electrical characteristics were measured.

  Next, using the deposited film forming apparatus 500 again, the first photovoltaic element 305 is formed on the substrate on which the intermediate layer (zinc oxide layer) is formed under the predetermined film forming conditions shown in Table 3. A pin type photovoltaic device having an i-layer of intrinsic amorphous Si: H was fabricated as described below.

  First, in the same manner as described above, an n-type layer is deposited to a predetermined thickness under predetermined conditions. After exhausting sufficiently, the gate valves 508 and 509 were opened, the substrate holder 521 was moved to the deposition chamber 504, and the gate valves 508 and 509 were closed.

  Next, the substrate is heated to a predetermined substrate temperature by a heater 516, a predetermined amount of a predetermined source gas is introduced, a predetermined degree of vacuum is set, a predetermined RF energy is introduced into the deposition chamber 517, and plasma is generated. An amorphous Si: Hi type layer is deposited on the substrate to a predetermined layer thickness by adjusting the film formation time. The chamber 504 was sufficiently evacuated, the gate valve 510 was opened, and the substrate holder 521 was moved from the chamber 504 to the chamber 505.

  In the same manner as described above, a p-type layer was deposited in a predetermined layer thickness under predetermined conditions.

  After sufficiently exhausting the deposition chamber 519 in the same manner as described above, the gate valve 511 was opened, and the substrate holder 521 on which the substrate formed up to the first photovoltaic element 305 was set was moved to the unload chamber 506.

  The substrate holder 521 was taken out from the unload chamber 506 in the same manner as described above.

  Next, the substrate formed up to the first photovoltaic element 305 is attached to the surface of the anode of the DC magnetron sputtering apparatus, the periphery of the sample is shielded with a stainless steel mask, and the substrate is 10 mm × 40 mm in an area of 40 mm × 40 mm. Indium tin oxide was sputtered as a transparent electrode using a target composed of 90% by weight of tin oxide and 90% by weight of indium oxide.

Deposition conditions are about 100 seconds at a substrate temperature of 170 ° C., an argon flow rate of 30 sccm as an inert gas, an oxygen gas of 0.5 sccm, a pressure in the deposition chamber of 300 mPa, and an input power amount of 0.2 W / cm ² per unit area of the target. Deposited to a thickness of 70 nm. The thickness of the film was set to a predetermined thickness by performing the deposition by calibrating the relationship with the deposition time under the same conditions in advance. The photovoltaic device thus fabricated was designated as “Example 1”.

[Comparative Example 1]
A photovoltaic element was produced in the same procedure as in Example 1 except that the zinc oxide layer was not inserted between the first photovoltaic element and the second photovoltaic element.

(Measurement)
First, the electrical characteristics of the zinc oxide layer deposited on the quartz substrate in Example 1 were measured. Since the range of resistivity of zinc oxide is wide (10 digits), it must be evaluated by a measurement system suitable for the resistance value. In general, the two-terminal method used for insulators is affected by contact resistance, so the four-terminal method is used. Here, using a MCP-T600 type resistivity meter made by Diane Instruments, a constant current was applied by a series four-terminal four-probe method, and the potential difference was measured by measuring the potential difference therebetween. The measurement results are shown in Table 4. A zinc oxide layer with a large amount of dopant contained in the target and a small amount of O ₂ and H ₂ O introduced exhibits a lower resistivity.

Next, YSS-150 made by Yamashita Denso Co., Ltd. was used for a total of 101 photovoltaic elements produced in Examples and Comparative Examples, and the current was irradiated in the state of AM1.5 spectrum and intensity of 100 mW / cm ^2. Voltage characteristics were measured. Short-circuit current density [Jsc (mA / cm ² )], open-circuit voltage [Voc (V)], and curvature factor [FF] were determined from the measured current-voltage characteristics, and conversion efficiency [η (%)] was determined.

  Further, the slope near V = 0 was obtained from the current voltage measurement in the dark state to obtain the shunt resistance (Rsh), and the series resistance (Rs) was obtained from the slope of the current rise.

The results are shown in Table 5, Table 6, Table 7, and Table 8.
When the zinc oxide layer has a high resistivity on the second photovoltaic element side and a low resistivity on the first photovoltaic element side, the FF is improved by increasing the reflection, decreasing the short circuit current, and improving the bonding surface. Although the photocurrent increases and the conversion efficiency improves, if the combination of the resistivity is reversed, the conversion efficiency decreases as Jsc decreases. Also, 5 if the × 10 ³ [Omega] cm in the range of 2 × 10 ⁰ [Omega] cm, exhibits excellent characteristics of the above combinations of resistivity, 2 × 10 ⁰ Ωcm or less, or a high resistivity portion, 5 × In the case of 10 ² Ωcm or less, the shunt resistance value decreases and the FF decreases due to the short-circuit current, resulting in a decrease in Jsc and a decrease in conversion efficiency. On the other hand, when the resistivity is 5 × 10 ³ Ωcm or more, the conversion efficiency slightly decreases as the series resistance increases.

* The above series resistance relative value indicates a higher series resistance value. A high series resistance value leads to characteristic degradation.

[Example 2]
As in Example 1, the second photovoltaic element 302 is a pin type photovoltaic element in which the i layer is intrinsic microcrystalline Si, and the first photovoltaic element 305 is an intrinsic amorphous Si: H And a stacked photovoltaic element using zinc oxide as an intermediate layer (see FIG. 3).

The sample of the zinc oxide layer was prepared separately from the photovoltaic device, and the conductivity as shown in Table 9 was adjusted while adjusting the introduction amount of oxygen gas and vaporized H ₂ O gas while leaving the Al-containing target as it was. A zinc oxide layer showing the rate was produced on a quartz plate. Based on this result, the inventors have found out conditions for producing a zinc oxide layer having a so-called graded resistivity in which the resistivity gradually changes in the thickness direction of the zinc oxide layer.

  Further, similarly to Example 1, a stacked photovoltaic element using a zinc oxide layer as an intermediate layer was produced under the conditions of the zinc oxide layer shown in Table 10. Each condition of the zinc oxide layer at this time is adjusted so that the resistivity increases from the first photovoltaic element side toward the second photovoltaic element.

  Evaluation was performed in the same manner as in Example 1 on the photovoltaic elements (2-1 to 5) thus manufactured. The results are also shown in Table 10.

  Even when the resistivity of the zinc oxide layer changes to graded, if the resistivity is high on the second photovoltaic element side and low on the first photovoltaic element side, the reflection increases. By reducing the short-circuit current and improving the bonding surface, the FF is improved, the photocurrent is increased and the conversion efficiency is improved.

Further, it was found that the effective range is a range of resistivity from 5 × 10 ³ Ωcm to 2 × 10 ⁰ Ωcm, and the high resistivity portion is in the range of 5 × 10 ² Ωcm or more.

[Example 3]
Example 3 is a pin type photovoltaic element in which the i layer is an intrinsic amorphous Si: H as the first photovoltaic element, and the pin type light in which the i layer is an intrinsic microcrystalline Si as the second photovoltaic element. A photovoltaic element and indium tin oxide and zinc oxide as an intermediate layer were laminated to produce a laminated photovoltaic element according to the third aspect of the present invention as shown in FIG.

A flat stainless steel (SUS430) generally called BA finish is used for the substrate 801 in FIG. 8 in the form of 45 mm × 45 mm in length and width and 0.15 mm in thickness, and a commercially available DC magnetron sputtering apparatus (not shown). It was evacuated until the pressure became 10 ⁻³ Pa or less.

Thereafter, argon gas was supplied at 30 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. The substrate was not heated, and a DC power of 120 W was applied to a 6 inch φ aluminum target to form a 70 nm aluminum thin film in 90 seconds. Subsequently, the substrate temperature was heated to 200 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 500 W DC power was applied for 30 minutes, and a substrate 801 on which a zinc oxide reflection increasing film of about 3000 nm was deposited was produced. .

  Next, using the deposited film forming apparatus 500 shown in FIG. 5, a photovoltaic element was formed under predetermined film forming conditions in each layer as shown in Table 11.

  According to Table 11, the 2nd photovoltaic element was first formed on the board | substrate 801 with the following procedures. The substrate 801 is set on the substrate holder 521 and set on the rail 520 of the load chamber 501. Then, the inside of the load chamber 501 is evacuated to a degree of vacuum of several hundred mPa or less.

  Next, the gate valve 507 is opened, and the substrate holder 521 is moved to the n-type layer deposition chamber 515 of the chamber 502. With the gate valves 507, 508, 509, 510, and 511 closed, an n-type layer is deposited to a predetermined layer thickness with a predetermined source gas. After the chamber 502 is sufficiently evacuated, the gate valve 508 is opened, the substrate holder 521 is moved to the deposition chamber 503, and the gate valve 508 is closed.

  A substrate is heated to a predetermined substrate temperature by a heater 512, a predetermined amount of a predetermined source gas is introduced, a predetermined degree of vacuum is set, a predetermined microwave energy or VHF energy is introduced into the deposition chamber 513, and plasma is generated. Then, a microcrystalline silicon i-type layer is deposited on the substrate to a predetermined layer thickness. After the chamber 503 is sufficiently evacuated, the gate valves 509 and 510 are opened to move the substrate holder 521 from the chamber 503 to the chamber 505.

  After the substrate holder 521 is moved to the p-type layer deposition chamber 519 of the chamber 505, the substrate is heated to a desired temperature by the heater 518. A source gas for p-type layer deposition is supplied to the deposition chamber 519 at a predetermined flow rate, RF energy is introduced into the deposition chamber 519 while maintaining a predetermined degree of vacuum, and the p-type layer is deposited to a desired layer thickness.

  After exhausting the deposition chamber 519 sufficiently in the same manner as described above, the gate valve 511 is opened, and the substrate holder 521 on which the substrate 201 on which the photovoltaic elements are deposited is moved to the unload chamber 506.

  All the gate valves are closed and nitrogen gas is sealed in the unload chamber 506 to cool the substrate temperature. Thereafter, the takeout valve of the unload chamber 506 is opened, and the substrate holder 521 is taken out.

Next, the substrate 801 manufactured from the substrate holder 521 to the second photovoltaic element is removed and placed in a commercially available DC magnetron sputtering apparatus (not shown) to form an intermediate layer, and the pressure is 10 ⁻³ Pa or less. It exhausted until it became.

  Indium tin oxide was sputtered using a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions are as follows: the substrate temperature is 170 ° C., the flow rate of argon as an inert gas is 50 cm ³ / min (normal), the oxygen gas is 0.2 cm ³ / min (normal), the pressure in the deposition chamber is 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched to 10 W, DC power of 10 W was applied for about 100 seconds, and the film was deposited to a thickness of about 10 nm. The thickness of the film was set to a predetermined thickness by performing the deposition by calibrating the relationship with the deposition time under the same conditions in advance.

  Then, it replaced with the target which consists of zinc oxide with the same apparatus, and sputtered zinc oxide.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, and 100 W DC power was applied for 5 minutes to deposit about 100 nm of zinc oxide.

  Next, using the deposited film forming apparatus 500 of FIG. 5 again, a pin type amorphous Si: H photovoltaic element is used as the first photovoltaic element on the substrate 801 on which the intermediate layer is formed. Prepared as described.

  In the same manner as described above, an n-type layer is deposited in a predetermined thickness in the chamber 502 under predetermined conditions. After the chamber 502 was sufficiently evacuated, the gate valves 508 and 509 were opened, the substrate holder 521 was moved to the chamber 504, and the gate valves 508 and 509 were closed.

  The substrate is heated to a predetermined substrate temperature by a heater 516, a predetermined amount of a predetermined source gas is introduced, a predetermined degree of vacuum is set, a predetermined RF energy is introduced into the deposition chamber 517, and plasma is generated on the substrate. An i-type layer of amorphous Si: H is deposited to a predetermined layer thickness. The chamber 504 was sufficiently evacuated, the gate valve 510 was opened, and the substrate holder 521 was moved from the chamber 504 to the chamber 505.

  In the same manner as described above, a p-type layer was deposited in a predetermined thickness in the chamber 505 under predetermined conditions.

  In the same manner as described above, after the deposition chamber 519 was sufficiently evacuated, the gate valve 511 was opened, and the substrate holder 521 on which the substrate 801 on which the photovoltaic elements were deposited was moved to the unload chamber 506.

  Further, the substrate holder 521 was taken out from the unload chamber 506 in the same manner as described above.

  Next, the substrate is attached to the surface of the anode of a DC magnetron sputtering apparatus, the periphery of the sample is shielded with a stainless steel mask, and 10% by weight of tin oxide and 90% by weight of indium oxide are formed in a central area of 40 mm × 40 mm. Indium tin oxide was sputtered as a transparent electrode using a target composed of

Deposition conditions are as follows: substrate temperature 170 ° C., flow rate of argon as inert gas 50 cm ³ / min (normal), oxygen gas 0.5 cm ³ / min (normal), pressure in the deposition chamber 300 mPa, input power per unit area of target The film was deposited in an amount of 0.2 W / cm ² to a thickness of 70 nm in about 100 seconds. The thickness of the film was set to a predetermined thickness by performing the deposition by calibrating the relationship with the deposition time under the same conditions in advance. The sample thus produced was designated “Act 3”.

[Comparative Example 2]
As shown in FIG. 12, a laminated photovoltaic element 1200 having the same configuration as that of the laminated photovoltaic element 800 of the present invention (see FIG. 8) except that an intermediate layer 1206 consisting of one layer is provided. To do. In FIG. 12, a light reflecting layer 1202, a second photovoltaic element 1203, an intermediate layer 1206, a first photovoltaic element 1207, and a transparent electrode 1208 are sequentially laminated on a conductive substrate 1201 such as metal. .

  In the production of the intermediate layer 1206, zinc oxide was sputtered using a target made of zinc oxide.

The production conditions were such that argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 100 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, and 100 W DC power was applied for 5 minutes for 30 seconds to deposit about 110 nm of zinc oxide. A photovoltaic element was produced in the same procedure as in Example 3 except that the intermediate layer 1206 consisting of one layer was produced in this manner. The sample thus produced was designated “Ratio 2-1”.

  Further, in the production of the intermediate layer 1206, indium tin oxide was sputtered using a target composed of 3% by weight tin oxide and 97% by weight indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched, and 10 W DC power was applied for about 18 minutes and 20 seconds, and the film was deposited to a thickness of about 110 nm. A photovoltaic device was produced in the same manner as in Example 3 except that the intermediate layer 1206 was produced in this manner. The sample thus produced was designated “Ratio 2-2”.

  Further, in the production of the intermediate layer 806 of the stacked photovoltaic element 800 having the configuration shown in FIG. 8, first, zinc oxide was sputtered using a target made of zinc oxide.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 100 W DC power was applied for 30 seconds, and about 10 nm of zinc oxide was deposited.

  Thereafter, in the same apparatus, indium tin oxide was sputtered by exchanging with a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched and DC power of 10 W was applied for about 16 minutes and 40 seconds, and deposition was performed to a thickness of about 100 nm. A photovoltaic element was produced in the same procedure as in Example 3 except that the intermediate layer was produced in this manner. The sample thus produced was designated “Ratio 2-3”.

Thus, about the sample produced in Example 3 and Comparative Example 2, YSS-150 made from Yamashita Denso Co., Ltd. was used, and the current-voltage characteristic was measured in the state irradiated with light of AM1.5 spectrum and intensity of 100 mW / cm ² . The short-circuit current density [Jsc (mA / cm ² )], open-circuit voltage [Voc (V)], curvature factor [FF], and photoelectric conversion efficiency [η (%)] were determined from the measured current-voltage characteristics.

The voltage-current characteristics of the sample in the dark state were measured, and the shunt resistance [Rsh (kΩcm ² )] was obtained from the inclination near the origin.

  Table 12 shows a summary of the ratios of the characteristic values to the comparative example (actual 3 / ratio 2-1, actual 3 / ratio 2-2, actual 3 / ratio 2-3).

  Actual 3 improved both FF and Voc compared with the ratio 2-1, and showed high photoelectric conversion efficiency. FIG. 10 shows the respective JV curves. The difference between the actual 3 and the ratio 2-1 is mainly due to the shift of Voc, and the ratio 2-1 is due to the poor bonding between the semiconductor interface and the interface of the intermediate layer. it is conceivable that.

  In addition, Actual 3 improved all FF, Voc, and Rsh compared to the ratio 2-2, and showed high photoelectric conversion efficiency. FIG. 11 shows the respective JV curves. It is considered that the ratio 2-2 is mainly due to the decrease in FF due to the decrease in shunt resistance.

  In addition, the actual 3 improved all of the FF, Voc, and Rsh compared with the ratio 2-3, and showed high photoelectric conversion efficiency. The ratio 2-3 is a configuration in which indium tin oxide is deposited after depositing zinc oxide on the contrary to the configuration of actual 3, but in this case, Voc and FF are reduced due to the effect of interface bonding and the decrease in shunt resistance. It is thought that it is decreasing.

  Further, the reliability test was performed as follows. The sample was put into a high-temperature and high-humidity tank and kept at 85 ° C. and a relative humidity of 85%. During this test, a reverse bias of −0.85 V was continuously applied to the sample for 20 hours. Then, after taking out and naturally drying and cooling sufficiently, the voltage-current characteristic was measured. Each characteristic is a relative value with respect to the initial value, and is shown in Table 13.

  As for the actual 3 and the ratio 2-1, a decrease in the shunt resistance was hardly observed by the reliability test. On the other hand, in the ratio 2-2 and the ratio 2-3, the shunt resistance decreased from the initial stage, Voc and FF mainly decreased, and the photoelectric conversion efficiency was decreased.

  From the above, it was found that according to the second and third aspects of the present invention, the initial photoelectric conversion efficiency is good and the reliability is high.

[Example 4]
Example 4 is a pin type photovoltaic element in which the i layer is an intrinsic amorphous Si: H as the first photovoltaic element, and an i layer is an intrinsic microcrystalline Si as the second photovoltaic element. The photovoltaic element, the laminated photovoltaic element according to the third aspect of the present invention as shown in FIG. 8 in which indium tin oxide and zinc oxide are laminated as an intermediate layer, the thickness ratio of indium tin oxide and zinc oxide Three samples were prepared by changing.

  In preparation of the intermediate layer, indium tin oxide was sputtered using a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched and 10 W DC power was applied for a predetermined time to deposit the film to a predetermined thickness.

  Thereafter, using the same apparatus, the target was made of zinc oxide, and zinc oxide was sputtered.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, and 100 W DC power was applied for a predetermined time to deposit zinc oxide having a predetermined film thickness. The total film thickness as the intermediate layer was adjusted to about 110 nm.

  A photovoltaic device was produced in the same manner as in Example 3 except that an intermediate layer in which the ratio of the zinc oxide layer and the indium tin oxide layer was changed was produced. The samples thus prepared were designated as “Act 4A”, “Act 4B”, “Act 4C”, and “Act 4D”. Table 14 shows the production conditions of each sample.

  Next, the current-voltage characteristics of the produced photoelectric conversion element were measured in the same manner as in Example 3. The results are shown in Table 15 and are shown as relative values to the comparative example “ratio 2-2”.

  Actual 4A, 4B, 4C, and 4D all improved from the ratio 2-2, but the conversion efficiency is higher when the indium tin oxide layer is thinner than the zinc oxide layer. Further, the reliability test was performed in the same manner as in Example 3. Each characteristic is shown in Table 16 as a relative value with respect to the initial value.

  As a result of the reliability test, the actual 4A, 4B, 4C, and 4D were all improved from the ratio 2-2, but the decrease was less when the indium tin oxide layer was thinner than the zinc oxide layer.

  From the above results, in Examples 4A and 4B, conversion efficiency is higher than that of 4C and 4D, the reliability test is good, and it is more preferable that the indium tin oxide layer is thinner than the zinc oxide layer.

[Example 5]
Example 5 is a pin type photovoltaic element in which the i layer is intrinsic amorphous Si: H as the first photovoltaic element, and the pin type light in which the i layer is intrinsic microcrystalline Si as the second photovoltaic element. Four samples were produced by changing the film thickness of indium tin oxide from the photovoltaic element according to the third aspect of the present invention in which indium tin oxide and zinc oxide were laminated as an intermediate layer as shown in FIG. did.

  In preparation of the intermediate layer, indium tin oxide was sputtered using a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched and 10 W DC power was applied for a predetermined time to deposit the film to a predetermined thickness.

  Thereafter, using the same apparatus, the target was made of zinc oxide, and zinc oxide was sputtered.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 100 W DC power was applied for 5 minutes, and 100 nm zinc oxide was deposited. A photovoltaic element was produced in the same manner as in Example 3 except that the intermediate layer with the indium tin oxide layer having a different thickness was produced in this manner. The samples thus prepared were designated as “Actual 5A”, “Actual 5B”, “Actual 5C”, and “Actual 5D”. Table 17 shows the production conditions of each sample.

  Next, the current-voltage characteristics of the produced photoelectric conversion element were measured in the same manner as in Example 3. The results are shown in Table 18 and are shown as relative values to the comparative example “ratio 2-2”.

  Actual 5A, 5B, 5C, and 5D all improved from the ratio 2-2, but the conversion efficiency is higher in the range of 1 nm to 50 nm for the indium tin oxide layer. Further, the reliability test was performed in the same manner as in Example 3. Each characteristic is shown in Table 19 as a relative value with respect to an initial value.

  As a result of the reliability test, the actual 5A, 5B, 5C, and 5D did not significantly decrease, but the thinner the indium tin oxide layer, the smaller the decrease, and the indium tin oxide layer is preferably 50 nm or less.

  From the above results, the indium tin oxide layer had higher conversion efficiency in the range of 1 nm to 50 nm, and the reliability test was also good.

[Example 6]
Example 6 is a pin type photovoltaic element in which the i layer is an intrinsic amorphous Si: H as the first photovoltaic element, and the pin type light in which the i layer is an intrinsic microcrystalline Si as the second photovoltaic element. Two samples were produced by changing the production conditions of the photovoltaic device according to the third aspect of the present invention as shown in FIG. 8 in which indium tin oxide and zinc oxide were laminated as an intermediate layer.

  In preparation of the intermediate layer, indium tin oxide was sputtered using a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched and 10 W DC power was applied for 8 minutes and 20 seconds to deposit the film to a thickness of 50 nm.

  Thereafter, using the same apparatus, the target was made of zinc oxide, and zinc oxide was sputtered.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 100 W DC power was applied for 5 minutes, and 100 nm zinc oxide was deposited. A photovoltaic element was produced in the same manner as in Example 3 except that the intermediate layer with the indium tin oxide layer having a different thickness was produced in this manner. The sample thus produced was designated “Act 6A”.

  Similarly, the electrical connection was switched to an indium tin oxide target, and 35 W DC power was applied for 2 minutes and 30 seconds, and the film was deposited to a thickness of 50 nm. Similarly, the electrical connection was switched to the zinc oxide target, and 30 W DC power was applied for 16 minutes and 40 seconds to deposit 100 nm of zinc oxide. The sample thus fabricated was designated “Real 6B”. Next, the current-voltage characteristics of the produced photoelectric conversion element were measured in the same manner as in Example 3. The results are shown in Table 20 and are shown as relative values to the comparative example “ratio 2-2”.

  Actual 6A had better characteristics than actual 6B. Further, the reliability test was performed in the same manner as in Example 3. Each characteristic is a relative value with respect to the initial value, and is shown in Table 21.

  As a result of the reliability test, all were good.

  From the above results, the conversion efficiency was higher and the reliability test was better when the deposition rate of the indium tin oxide layer was slower than the deposition rate of the zinc oxide layer.

[Example 7]
Example 7 is a pin type photovoltaic element in which the i layer is an intrinsic amorphous Si: H as the first photovoltaic element, and the pin type light in which the i layer is an intrinsic microcrystalline Si as the second photovoltaic element. Three samples were produced by changing the production conditions of the photovoltaic element according to the third aspect of the present invention as shown in FIG. 8 in which indium tin oxide and zinc oxide were laminated as an intermediate layer.

  In preparation of the intermediate layer, indium tin oxide was sputtered using a target composed of 3 wt% tin oxide and 97 wt% indium oxide.

The deposition conditions were as follows: a substrate temperature of 170 ° C., an argon gas flow rate of 50 cm ³ / min (normal), an oxygen gas of 0.2 cm ³ / min (normal), a pressure in the deposition chamber of 200 mPa, and 6 inch φ indium tin oxide target. The electrical connection was switched and 10 W DC power was applied for 100 seconds to deposit the film to a thickness of 10 nm.

  Thereafter, using the same apparatus, the target was made of zinc oxide, and zinc oxide was sputtered.

As deposition conditions, argon gas was supplied at 30 cm ³ / min (normal) and oxygen gas was supplied at 2 cm ³ / min (normal), and the pressure was maintained at 2 × 10 ⁻¹ Pa. Subsequently, the substrate temperature was heated to 120 ° C., the electrical connection was switched to a 6 inch φ zinc oxide target, 100 W DC power was applied for 5 minutes, and 100 nm zinc oxide was deposited. A photovoltaic element was produced in the same manner as in Example 3 except that the intermediate layer with the indium tin oxide layer having a different thickness was produced in this manner. The sample thus produced was designated “Act 7A”.

  Similarly, the substrate temperature was set to 120 ° C., the electrical connection was switched to the target of indium tin oxide, 10 W DC power was applied for 100 seconds, and the film was deposited to a thickness of 10 nm. Thereafter, similarly, the substrate temperature was set to 170 ° C., the electrical connection was switched to the zinc oxide target, 100 W direct current power was applied for 5 minutes, and 100 nm zinc oxide was deposited. The sample thus prepared was designated “Real 7B”.

  Similarly, the substrate temperature was set to 170 ° C., the electrical connection was switched to the target of indium tin oxide, 10 W DC power was applied for 100 seconds, and the film was deposited to a thickness of 10 nm. Thereafter, similarly, the substrate temperature was set to 250 ° C., the electrical connection was switched to the zinc oxide target, and 100 W DC power was applied for 5 minutes to deposit 100 nm of zinc oxide. The sample thus produced was designated “Real 7C”.

  When the surface was visually observed after the intermediate layer was deposited, minute film peeling was observed in the actual 7C. When confirmed with a microscope, it was found that the intermediate layer was peeled off.

  Next, the current-voltage characteristics of the produced photoelectric conversion element were measured in the same manner as in Example 3. The results are shown in Table 22 and are shown as relative values to the comparative example “ratio 2-2”.

  Actual 7A, 7B, and 7C all had better characteristics than “ratio 2-2”, but actual 7A was better. Further, the reliability test was performed in the same manner as in Example 3. Each characteristic is shown in Table 23 as a relative value to the initial value.

  As a result of the reliability test, all of the actual materials 7A to 7C had better characteristics than “Ratio 2-2”.

  In the case of the actual 7C, although the intermediate layer was finely peeled off, it was found that the reliability test did not deteriorate much. Actual 7A was found to be less degraded than the others.

  From the above results, the conversion efficiency was higher when the formation temperature of the zinc oxide layer was lower than the formation temperature of the indium oxide layer, and the reliability test was also good.

It is the schematic which shows typically the cross-section of the photovoltaic element provided with the conventional zinc oxide layer. It is the schematic which shows the one part electric polarity of one Embodiment of the laminated photovoltaic element of this invention. It is the schematic which shows typically the cross-section of one Embodiment of the laminated photovoltaic element of this invention. It is a figure which shows typically the electric power generation operation | movement of the laminated photovoltaic element of this invention. It is a schematic diagram which shows one form of an apparatus suitable in order to produce the semiconductor layer of the laminated photovoltaic element of this invention. It is a schematic diagram which shows one form of an apparatus suitable in order to produce the zinc oxide layer of the laminated photovoltaic element of this invention. It is the schematic which shows typically the manufacturing method of the laminated photovoltaic element which concerns on this invention. It is the schematic which shows typically the cross-section of one Embodiment of the laminated photovoltaic element which concerns on this invention. It is the schematic which shows typically the cross-section of the laminated photovoltaic element in other embodiment. It is explanatory drawing which shows the JV curve of the actual 3 and ratio 2-1. It is explanatory drawing which shows the JV curve of the actual 3 and ratio 2-2. It is the schematic which shows the cross-section of the laminated photovoltaic element provided with the intermediate | middle layer which consists of one layer of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Laminated photovoltaic element 101 Substrate 102 2nd photovoltaic element 103 Zinc oxide layer 104 1st photovoltaic element 105 Transparent electrode 106 Short circuit in 2nd photovoltaic element 107 1st photovoltaic Short circuit in power element 200 Stacked photovoltaic element of the present invention 201 Substrate 202 Second zinc oxide layer showing n-type electrical characteristics 203 First zinc oxide layer showing n + -type electrical characteristics 204 n ++ type The n-type semiconductor layer of the first photovoltaic element that exhibits the electrical characteristics of the layer 205 Transparent electrode 206 The second photovoltaic element 207 The zinc oxide layer 208 The first photovoltaic element 300 The stacked photovoltaic element of the present invention 301 Substrate 302 Second photovoltaic element 303 Second zinc oxide layer 304 First zinc oxide layer 305 First photovoltaic element 306 Transparent electrode 401, 403 Second photovoltaic element Short circuit in 402 Short circuit in first photovoltaic element 500 Semiconductor deposition film forming apparatus 501 Load chamber 502 N layer chamber 503 Microcrystalline i layer chamber 504 Amorphous i layer chamber 505 P layer chamber 506 Unload chamber 507, 508, 509, 510, 511 Gate valve 512 Heater for heating microcrystalline i layer substrate 513 Microcrystalline i layer plasma CVD chamber 514 Heating heater for n layer substrate 515 N layer plasma CVD chamber 516 Heating amorphous i layer substrate Heater 517 i layer plasma CVD chamber 518 p layer substrate heater 519 p layer plasma CVD chamber 520 holder transport rail 600 sputter chamber 601 substrate holder 602 gas introduction pipe 603 heater 604 zinc oxide target 605 DC power source 606 a SShield 700 Substrate 701 Reflective layer 702 Second photovoltaic element 703 Layer made of indium oxide 704 Layer made of zinc oxide 705 Intermediate layer 706 First photovoltaic element 800 Stacked photovoltaic element 801 Substrate 802 Light reflecting layer 803 Second photovoltaic element 804 First layer made of indium oxide 805 Second layer made of zinc oxide 806 Intermediate layer 807 First photovoltaic element 808 Transparent electrode 900 Multilayer photovoltaic element 901 Substrate 902 Light reflecting layer 903 Second photovoltaic element 904 First layer made of indium oxide 905 Second layer made of zinc oxide 906 Intermediate layer 907 First photovoltaic element 908 Transparent electrode 1200 Multilayer photovoltaic element 1201 Substrate 1202 Light reflecting layer 1203 Second photovoltaic element 1206 Intermediate layer 1207 1 of the photovoltaic element 1208 transparent electrode

Claims (9)

A method of manufacturing a stacked photovoltaic element having an intermediate layer between photovoltaic elements including a pn junction or a pin junction,
The intermediate layer is formed by laminating a first layer whose main component is indium oxide at the interface of at least one photovoltaic device and then laminating a second layer whose main component is zinc oxide. A method for producing a stacked photovoltaic element.   2. The method for manufacturing a stacked photovoltaic element according to claim 1, wherein the film thickness of the second layer is larger than the film thickness of the first layer.   3. The method for manufacturing a stacked photovoltaic element according to claim 1, wherein the film thickness of the first layer is 1 nm or more and 50 nm or less.   4. The stacked photovoltaic device according to claim 1, wherein the second layer is formed so that a formation speed of the second layer is higher than a formation speed of the first layer. 5. Method.   5. The stacked photovoltaic device according to claim 1, wherein the second layer is formed so that a formation temperature of the second layer is lower than a formation temperature of the first layer. Method. A stacked photovoltaic element having an intermediate layer between photovoltaic elements including a pn junction or a pin junction,
The intermediate layer is formed by laminating a second layer whose main component is made of zinc oxide on a first layer whose main component is made of indium oxide and stacked at the interface of at least one photovoltaic device. A laminated photovoltaic device characterized by the above.   The stacked photovoltaic element according to claim 6, wherein the film thickness of the second layer is thicker than the film thickness of the first layer.   The stacked photovoltaic element according to claim 6 or 7, wherein the film thickness of the first layer is 1 nm or more and 50 nm or less.   9. The stacked photovoltaic element according to claim 6, wherein the transmittance of the second layer at a wavelength of 800 nm is higher than the transmittance of the first layer at a wavelength of 800 nm.

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