JP2937815B2 - Photovoltaic element and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having high photoelectric conversion efficiency and a method for manufacturing the same.

[0002]

2. Description of the Related Art Photovoltaic elements, which are photoelectric conversion elements for converting sunlight into electric energy, have been widely applied as small power sources for consumer use such as calculators and wristwatches. Has attracted attention as a technology that can be put to practical use as a so-called fossil fuel alternative electric power. A photovoltaic element is a technology that uses the photovoltaic power of a pn junction of a semiconductor. A semiconductor such as silicon absorbs sunlight to generate photocarriers of electrons and holes, and the photocarriers are generated inside the pn junction. It drifts due to the electric field and is taken out.

[0003] Such a method of producing a photovoltaic element is generally performed by using a semiconductor process.
Specifically, a single crystal of valence-controlled silicon is formed into p-type or n-type silicon by a crystal growth method such as a CZ method.
The single crystal is sliced to produce a silicon wafer having a thickness of about 300 μm. Further, a pn junction is formed by forming a layer of a different conductivity type by an appropriate means such as diffusion of a valence electron controlling agent so as to have a conductivity type opposite to the conductivity type of the wafer.

Meanwhile, from the viewpoints of reliability and conversion efficiency, single-crystal silicon is used as a photovoltaic element that has been mainly put into practical use at present. Has a high production cost because it uses a semiconductor process.

Another disadvantage of single-crystal silicon photovoltaic devices is that single-crystal silicon has an indirect transition and therefore has a low light absorption coefficient, and single-crystal photovoltaic devices have at least 50 μm to absorb incident sunlight. The thickness must be increased, and the band gap is about 1.1 eV, which is smaller than 1.5 eV, which is suitable for a photovoltaic device. Therefore, a long wavelength component cannot be used effectively. Even if the production cost is reduced by using polycrystalline silicon, the problem of indirect transition remains, and the thickness of the photovoltaic element cannot be reduced. Polycrystalline silicon also has grain boundaries and other problems.

Further, a large-area wafer cannot be manufactured due to its crystalline nature, and it is difficult to increase the area. If large power is to be taken out, wiring for serializing or parallelizing the unit elements is performed. What you have to do,
When used outdoors, the production cost per unit power generation is lower than that of existing power generation methods because expensive mounting is required to protect the photovoltaic element from mechanical damage caused by various weather conditions. There is a problem that it becomes expensive. Under such circumstances, in promoting the practical use of the photovoltaic element for electric power, cost reduction and enlargement of the area are important technical issues, and various studies have been made.

[0007] Materials such as low-cost materials and materials with high conversion efficiencies have been sought. As materials for such photovoltaic elements, amorphous silicon, amorphous silicon germanium, amorphous Tetrahedral amorphous semiconductor such as porous silicon carbide and II-V such as CdS and Cu ₂ S
Examples thereof include group I and III-V group compound semiconductors such as GaAs and GaAlAs. In particular, a thin-film photovoltaic element using an amorphous semiconductor for the photovoltaic generation layer can produce a film having a larger area than a single-crystal photovoltaic element,
It has advantages such as a thin film thickness and the ability to be deposited on an arbitrary substrate material, and is considered promising.

However, in order to put a photovoltaic element using the above amorphous semiconductor into practical use as a power element,
Improvements in photoelectric conversion efficiency and reliability are issues to be studied.

There are various methods for improving the photoelectric conversion efficiency of a photovoltaic device using an amorphous semiconductor. For example, in the case of a photovoltaic device using a pin-type semiconductor junction, the photoelectric conversion efficiency is increased. In order to improve the efficiency, it is necessary to improve the characteristics of each of the p-type semiconductor layer, the i-type semiconductor layer, the n-type semiconductor layer, the transparent electrode, and the back electrode constituting the photovoltaic element.

As another method for improving the conversion efficiency of a photovoltaic element, the use of a so-called stack cell in which a plurality of photovoltaic elements having a unit element structure are stacked is disclosed in US Pat. No. 2,949,498. Have been. Although a pn junction crystal semiconductor was used in this stack cell, the idea is common to both amorphous and crystalline semiconductors, and the solar spectrum is efficiently absorbed by photovoltaic elements having different band gaps. By increasing the open circuit voltage (V _OC ), the power generation efficiency is improved.

The stack cell is a device in which devices having different band gaps are stacked and the conversion efficiency is improved by efficiently absorbing each part of the spectrum of the sunlight. A so-called top layer located on the light incident side of the stacked devices. The band gap of the so-called bottom layer located below the top layer is designed to be narrower than the band gap of the above.
In response, Hamakawa et al. (Y. Hamakawa, H. Okamoto, and YN
Itta "Applied Physics Letters" 35 (1979), p. 187) multiply stacks amorphous silicon of the same band gap without an insulating layer between photovoltaic elements, and the open voltage (V _OC ) of the entire element Report a so-called cascade battery that increases In this method, unit elements made of an amorphous silicon material having the same band gap are stacked.

As described above, in the case of a stacked cell, as in the case of a single-layer cell (single cell), in order to improve the photoelectric conversion efficiency, a p-type semiconductor layer and an i-type It is necessary to improve the characteristics of each of the semiconductor layer, the n-type semiconductor layer, the transparent electrode, and the back electrode.

For example, in the case of an i-type semiconductor layer, it is necessary to have a desired band gap depending on the use of a single cell or a stack cell. The level in the gap (local level) is reduced as much as possible, It is important to improve running performance.

[0014] Improvements in the characteristics of the photovoltaic element have been studied by methods other than the method of essentially improving the film quality of the i-type semiconductor layer. For example, a p-type semiconductor and / or n
U.S. Pat. No. 4,254,429 and U.S. Pat. No. 4,37,043, disclose a method of using a so-called buffer layer for giving a gradient of the bandwidth at the junction interface between the type semiconductor and the i-type semiconductor layer.
7,723. The purpose of the buffer layer is to provide a large number of levels at the junction interface between a p-type semiconductor made of amorphous silicon or an n-type semiconductor and an i-type semiconductor made of amorphous silicon germanium due to a difference in lattice constant. The purpose of the present invention is to improve the open-circuit voltage (V _OC ) by using amorphous silicon at the junction interface to eliminate the level and improve the junction and not to impair the carrier traveling property.

Further, as another method, for example, amorphous silicon germanium is used as the i-type semiconductor layer, and the composition ratio is provided in the intrinsic layer by changing the composition ratio of silicon and germanium to improve the characteristics. There is disclosed a method of providing a so-called gradient layer for improvement. For example, according to U.S. Pat. No. 4,816,082, the band gap of the i-layer in contact with the first valence-controlled semiconductor layer on the light incident side is widened, and the band gap gradually increases toward the center. Are disclosed, and the band gap is gradually increased toward the second valence electron controlled semiconductor layer. According to this method, carriers generated by light can be efficiently separated by the action of an internal electric field, and the photoelectric conversion efficiency is improved.

Further, when amorphous silicon or amorphous silicon germanium is used as the i-type semiconductor layer, the i-type semiconductor layer is often slightly n-type.
It has also been studied to improve the hole traveling property by mixing a valence electron controlling agent of the type.

Incidentally, a p-type semiconductor layer or an n-type semiconductor layer
For any so-called doping layer, first activate
High acceptor or donor density
Low energy is required. Thereby, p
Diffusion potential when in-junction is formed (built-in potential
Char) increases and the open-circuit voltage of the photovoltaic element increases
(V _OC) Is increased, and the photoelectric conversion efficiency is improved.

Next, since the doping layer basically does not contribute to the generation of a photocurrent, it is required that the incidence of light on the i-type semiconductor layer that generates the photocurrent is not hindered as much as possible. Therefore,
It is important to widen the optical band gap and to reduce the thickness of the doping layer.

Further, it is required that a homo or hetero pin junction is formed between the doping layer and the i-type semiconductor layer, and that the interface level at the junction interface is small.

As described above, the materials of the doping layer having characteristics and the method of forming the same have been generally studied.

As the material of the doping layer, Si, Si
C, SiN, SiO and the like are listed, and amorphous or microcrystalline forms have been studied. As a formation method,
RF plasma CVD, ECR plasma CVD, optical CVD
And other methods have been studied.

Among the materials of the above-mentioned doping layers, amorphous silicon (a-S) is used as the doping layer on the back side of the i-type semiconductor layer with respect to the light incident direction because of its easy formation.
i) is widely used, and since the doping layer on the light incident side of the i-type semiconductor layer has a small absorption coefficient, amorphous silicon carbide (a-SiC) has a small absorption coefficient and a small activation energy. , Microcrystalline silicon (μc-Si) has been used.

A comparison between an amorphous doping layer and a microcrystalline doping layer shows that the microcrystal generally has a smaller absorption coefficient, a larger optical band gap, and a smaller activation energy. It is considered desirable as a layer.

However, it is not easy to form a microcrystalline material having a high activated acceptor or donor density and a low activation energy.
The material other than, announcement example of open circuit voltage (V _OC) is large photoelectric conversion efficient photovoltaic element is small, prospect of practical use do not stand. Further, on the amorphous i-type semiconductor layer,
When depositing a microcrystalline or polycrystalline doping layer,
In particular, when the i-type semiconductor layer and the doping layer form a heterojunction, there is a concern that an increase in interface states may adversely affect the pin junction.

It has also been studied to reduce the absorption coefficient of the doping layer by the quantum well effect by combining the above materials to form a multilayer structure.
It is considered that it is not suitable for practical use because it is difficult to control the multilayer film structure of the doping layer whose total film thickness is to be reduced and the cost of the apparatus for forming the layer is high.

As described above, the development of the doping layer of the amorphous photovoltaic device has not been sufficiently developed. In an amorphous photovoltaic element, in order to improve photoelectric conversion efficiency, i.
While the development of the type semiconductor layer is important, the development of an ideal doping layer is also important.

On the other hand, an amorphous photovoltaic element has a poor film quality as compared with a crystalline silicon photovoltaic element, and therefore has insufficient conversion efficiency.
It is higher than thermal power, hydroelectric power, etc. In order for amorphous silicon-based photovoltaic elements to be used for power applications in line with existing power generation methods, it is required to further improve the conversion efficiency.

[0028]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention introduces a new doping layer structure and forming method, thereby realizing low cost, high reliability suitable for practical use, It is another object of the present invention to provide a photovoltaic element having high photoelectric conversion efficiency and a method for manufacturing the same.

[0029]

As a result of intensive studies on the structure and method of forming a doping layer, the present inventor has found that in a photovoltaic device having a doping layer having the following structure and a method of manufacturing the same, a large open voltage ( (V _OC ) and high photoelectric conversion efficiency.

[0030] That is, the manufacturing method of the photovoltaic device of the present invention, the semiconductor junction of the pin-type p-type semiconductor layer and the n-type semiconductor layer two doped layers made of is laminated via the i-type semiconductor layer A method for manufacturing a photovoltaic device, wherein the crystal form of the doping layer D located at least below the i-type semiconductor layer is non-single-crystal. When α is set, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D is exposed to the plasma containing the α.

In the first photovoltaic device according to the present invention, two doping layers consisting of a p-type semiconductor layer and an n-type semiconductor layer have an i-type.
Type semiconductor layer of the semiconductor junction of stacked pin type having <br/> through, and light crystalline form of the doping layer D located below at least the i-type semiconductor layer is non-monocrystalline The photovoltaic device is characterized in that the doping layer D is formed by the method for manufacturing a photovoltaic device according to claim 1.

According to the second photovoltaic device of the present invention, two doping layers comprising a p-type semiconductor layer and an n-type semiconductor layer have i
In a stack cell type photovoltaic element having a structure in which a pin-type semiconductor junction laminated via a type semiconductor layer is laminated two or more times, at least one layer of the doping layer D is according to claim 1. The photovoltaic element is formed by the above-described method.

The above-described doping layer D contains
The composition ratio of α varies in the film thickness direction. Further, the above-mentioned doping layer D is characterized in that a part thereof is microcrystallized or polycrystallized in the film thickness direction.

[0034]

According to the first aspect of the present invention, a two-layered doping layer composed of a p-type semiconductor layer and an n-type semiconductor layer is provided with a pin-type semiconductor contact layer laminated via an i-type semiconductor layer. Have a union , and
In the method for manufacturing a photovoltaic device in which the crystal form of the doping layer D located at least below the i-type semiconductor layer is non-single-crystal, when an element that expands the band gap of the doping layer D is α, After forming the doping layer D and before forming the i-type semiconductor layer, the optical band gap of the doping layer D is increased by exposing the surface of the doping layer D to the plasma containing α. I was able to.

As a result, it was possible to form a doping layer in which the density of the activated acceptor or donor was high and the activation energy was low, and the optical band gap was large and the absorption coefficient was low.

(Claim 2) According to the invention of claim 2, two doping layers consisting of a p-type semiconductor layer and an n-type semiconductor layer are connected to each other with a pin-type semiconductor contact layer laminated via an i-type semiconductor layer. Have a union , and
A photovoltaic device in which the crystal form of the doping layer D located at least below the i-type semiconductor layer is non-single-crystal, wherein the doping layer D is formed by the method of manufacturing a photovoltaic device according to claim 1. Due to the formation, the absorption of light by the doping layer is reduced, the built-in potential of the photovoltaic device is increased, and the open-circuit voltage (V _OC ) and short-circuit current (J _SC ) of the photovoltaic device are increased. The photoelectric conversion efficiency has been improved.

(Claim 3) According to the invention of claim 3, a pin-type semiconductor junction in which two doping layers consisting of a p-type semiconductor layer and an n-type semiconductor layer are stacked via an i- type semiconductor layer is formed. In a stack cell type photovoltaic device having a structure stacked two or more times, at least one of the doping layers D is
By being formed by the method for manufacturing a photovoltaic device according to claim 1, the built-in potential of the pin junction at that portion increases, and the open-circuit voltage (V _OC ) of the entire stack type photovoltaic device increases. However, the light absorption by the doping layer was reduced, the short-circuit current (J _SC ) was increased, and the photoelectric conversion efficiency was improved.

Further, when used in a doping layer above a tunnel junction (ie, a pn junction) in a stack type photovoltaic element, mutual expansion of the valence electron controlling agent in the tunnel junction is reduced. . As a result, the open-circuit voltage (V _OC ) and the fill factor (FF) of the photovoltaic element
And the photoelectric conversion efficiency was improved.

(Claim 4) According to the invention of claim 4, the doping layer D contains
Since the composition ratio of α has a variation in the film thickness direction, the built-in potential of the photovoltaic element further increases, and the open-circuit voltage (V _OC ) of the photovoltaic element _decreases. And the photoelectric conversion efficiency was further improved.

(Claim 5) According to the invention according to claim 5, the doping layer D is
Partially crystallized or polycrystallized in the film thickness direction, the built-in potential of the photovoltaic device further increases, the open-circuit voltage (V _OC ) of the photovoltaic device increases, and the Light absorption was further reduced, the short circuit current (J _SC ) was increased, and the photoelectric conversion efficiency was further improved.

Although the detailed mechanism of the above-mentioned operation has not been clarified yet, the following may be considered.

First, after forming a p-type or n-type doping layer and before forming an i-type semiconductor layer, the surface of the doping layer is exposed to a plasma containing an element for expanding the band gap of the doping layer. An element for expanding the band gap of the doping layer is implanted into the doping layer, and the optical band gap increases.

According to this method, when depositing the doping layer, a gas containing an element which expands the band gap of the doping layer is used as a source gas as a part of the mixed gas to decompose the material, thereby widening the optical band gap. Compared to the case of forming a doping layer, a doping layer having high conductivity and low activation energy was able to be formed with the same optical band gap. This seems to be due to the following reasons.

That is, when a doping layer having a desired optical band gap is formed by deposition, it is generally difficult to obtain a doping layer having high conductivity and low activation energy as the optical band gap is widened. This is not only because the intrinsic state dark conductivity decreases with an increase in the band gap and the activation energy increases, but also as the band gap increases, the localization level of the doping layer increases and the activation level increases. It is considered that the density of donors and acceptors decreased. This problem,
For one thing, as the raw material gas when depositing a doping layer, but shall lightnings use a mixed gas of raw material gas containing an element to increase the raw material gas and the band gap including a main structural elements of the doping layer, generally these 2 Since the decomposition efficiencies of the different types of source gases for the same energy are different
It is conceivable that the element that widens the band gap is easily segregated in the film. Conventionally, in order to solve this problem, the type of material gas of the doping layer has been studied, and a film forming method that devises a method of decomposing the material gas has been studied. There was a problem in terms of damage to the underlying layer.

On the other hand, according to the method for forming a doping layer of the present invention, the element for expanding the band gap of the doping layer is implanted after the deposition of the doping layer.
During deposition, conductivity is high, activation energy is low,
What is necessary is just to deposit under the optimal deposition conditions which can produce a thin film with few localized levels. Thereafter, although for injection into the doping layer an element to expand the band gap by the plasma treatment, such injection element to expand the band gap by glow discharge flop plasma is conventional used in the crystalline silicon, etc. It is completely different from ion implantation. In conventional ion implantation, ions are accelerated in the form of a beam, and the energy of ions is high. On the other hand, ion implantation by glow discharge plasma has low energy of the substance to be implanted, and the ion energy is extremely high. It is injected into the body of the shallow realm.

Therefore, the layer to be processed is not damaged by the accelerated ions. In addition, since two kinds of source gases are not dispersed with the same energy as in the case of deposition, it is easy to find the optimum processing conditions, and the element that expands the band gap rarely segregates in the film. Therefore, a doping layer having a small local level and a large optical band gap can be formed without impairing the film quality of the doping layer. Therefore,
The density of the activated donor and acceptor is maintained, even with open optical bandgap of the doped layer,
It is considered that high conductivity and low activation energy could be maintained.

In order to decompose the above two kinds of source gases and deposit a doping layer uniformly over a large area, it is necessary to devise a deposition apparatus.
It is easy to finely control the depth at which the element for expanding the optical band gap of the doping layer is injected, and uniform injection over a large area can be easily performed.

Further, when depositing a doping layer having a large optical band gap or a doping layer made of microcrystal or polycrystal, a condition in which the energy of ions is large is required, and a layer underlying the doping layer may be damaged. However, in the case of the present invention, even when a doping layer having a large optical band gap or a doping layer made of microcrystal or polycrystal is formed, it is necessary to perform the deposition under the condition that the ion energy is large. Therefore, no damage is caused to the underlying layer of the doping layer. In particular, when a stacked photovoltaic element is used as the doping layer above the tunnel junction, the layer underlying the doping layer, that is, the doping layer below the tunnel junction is not damaged, and the tunnel junction is not damaged. The interdiffusion of impurities in the portion was reduced, the open-circuit voltage (V _OC ) and the fill factor (FF) of the photovoltaic element were increased, and the photoelectric conversion efficiency was improved.

Further, according to the present invention, it is easy to finely control the depth at which the element for expanding the optical band gap of the doping layer is implanted, so that the band gap is expanded in the thickness direction of the doping layer. By changing the composition ratio of the elements, the band gap of the doping layer can be changed in the thickness direction. For example, when the band gap near the interface between the doping layer and the i-type semiconductor layer is particularly increased, it is considered that the built-in potential is larger than when the band gap of the doping layer is uniform in the film thickness direction.

Furthermore, according to the present invention, the vicinity of the surface of the deposited amorphous doping layer is microcrystallized or adjusted by adjusting the conditions of the plasma treatment for injecting an element for expanding the band gap of the doping layer. It can be polycrystallized or non-crystallized near the surface of the deposited microcrystalline or polycrystalline doping layer.

For example, by enlarging the band gap and micro-crystallizing or poly-crystallizing the vicinity of the surface of the deposited amorphous doping layer, the absorption coefficient of the doping layer is reduced, and Short circuit current (J _SC ) increased. Also, by microcrystallization or polycrystallization,
The activation energy of the doping layer was reduced, the built-in potential of the photovoltaic element was increased, and the open-circuit voltage (V _OC ) and fill factor (FF) were improved.

Further, for example, by increasing the band gap and decrystallizing the vicinity of the surface of the deposited microcrystalline or polycrystalline doping layer, the built-in potential of the photovoltaic element is increased. Further, the interface state caused by the contact between the i-type semiconductor layer and the microcrystalline or polycrystalline doping layer was reduced by the interposition of the amorphous doping layer. As a result, the open-circuit voltage (V _OC ) and the fill factor (FF) of the photovoltaic element increased.

This is because the doping layer made of a microcrystalline or polycrystalline semiconductor and the i-type semiconductor layer made of an amorphous semiconductor are generally in contact with each other, so that the p / i interface or the n / i interface is formed.
When an interface is formed, it is considered that an interface level occurs at the p / i interface or the n / i interface. In the above case, the doping layer made of a microcrystalline or polycrystalline semiconductor and the i-type made of an amorphous semiconductor are used. Since there is a doping layer made of an amorphous semiconductor between the semiconductors, an interface state generated when the amorphous semiconductor is in contact with the microcrystalline or polycrystalline semiconductor is at the p / p interface or the n / n interface. It is considered that the adverse effect due to the interface state was significantly reduced, and the built-in potential was increased. Further, a doping layer made of an amorphous semiconductor having a band gap wider than that of the microcrystalline or polycrystalline semiconductor exists between the doping layer made of the microcrystalline or polycrystalline semiconductor and the i-type semiconductor layer made of the amorphous semiconductor. It is considered that the built-in potential has been increased.

[0054]

[Example of embodiment]

(Configuration of Photovoltaic Element) As the configuration of the photovoltaic element of the present invention, there are two types, a single cell type shown in FIG. 1 and a stacked cell type shown in FIG. Below,
The configuration of the photovoltaic element of the present invention and the method of manufacturing the same will be described with reference to the drawings.

FIG. 1 is an example of a schematic sectional view showing a single-cell type photovoltaic device according to the present invention. However,
The present invention is not limited to the photovoltaic element having the configuration shown in FIG. 1, reference numeral 101 denotes a substrate; 102, a back electrode; 103, an n-type semiconductor layer which is a feature of the present invention;
Denotes an i-type semiconductor layer, 105 denotes a p-type semiconductor layer, 106 denotes a transparent electrode, and 107 denotes a current collecting electrode. FIG. 1 shows a configuration in which light enters from the p-type semiconductor layer side. In the case of a photovoltaic element having a configuration in which light enters from the n-type semiconductor layer side, 103 is a p-type semiconductor layer which is a feature of the present invention. , 105 become n-type semiconductor layers. Further, FIG. 1 shows a configuration in which light is incident from the opposite side to the substrate. In a photovoltaic element having a configuration in which light is incident from the substrate side, the positions of the transparent electrode and the back electrode are reversed, and 102 is a transparent electrode. 103 may be a p-type semiconductor layer, 105 may be an n-type semiconductor layer, and 106 may be a back surface electrode.

FIG. 2 is an example of a schematic sectional view showing a stacked cell type photovoltaic element according to the present invention. However,
The present invention is not limited to the photovoltaic element having the configuration shown in FIG.

The stacked cell type photovoltaic element shown in FIG.
It has a structure in which three pin junctions are stacked, and 216
Is the first pin junction counted from the light incident side, and 215 is the second pin junction.
And 214 is a third pin junction. These three pin junctions are formed on the back surface electrode 202 formed on the substrate 201, and are connected to the three pin junctions.
A transparent electrode 212 and a current collecting electrode 213 are formed at the top of the junction to form a stacked photovoltaic element.

Each of the pin junctions is composed of an n-type semiconductor layer 203, 206, 209, an i-type semiconductor layer 204,
207, 210, p-type semiconductor layers 205, 208, 211
Consists of Further, as in the photovoltaic element of FIG. 1, the arrangement of the doping layers and the electrodes may be switched depending on the incident direction of light.

Hereinafter, each layer constituting the photovoltaic element of the present invention will be described in detail in the order of formation.

(Substrate) The substrate according to the present invention has a semiconductor layer 103 to a thin film having a thickness of about 1 μm on its surface.
Used for depositing 105, 203-211.
Such substrates 101 and 201 have a crystal form (single crystalline or non-single crystalline), an electrical property (conductive or insulating), and an optical property (light-transmitting or non-light-transmitting). It doesn't matter. However, those having little deformation and distortion and having desired strength are preferable.

As the material of the substrate, for example, Fe, N
i, Cr, Al, Mo, Au, Nb, Ta, V, Ti,
Metals such as Pt and Pb or alloys thereof, for example, brass, thin plates such as stainless steel and composites thereof, and polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, Films or sheets of heat-resistant synthetic resin such as epoxy or composites thereof with glass fiber, carbon fiber, boron fiber, metal fiber, etc., and thin plates of these metals, metal thin films of different materials on the surfaces of resin sheets and the like; And / or glass, ceramics, etc. obtained by subjecting an insulating thin film such as SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN or the like to a surface coating treatment by a sputtering method, a vapor deposition method, a plating method, or the like.

When the substrate is electrically conductive such as a metal, it may be used as an electrode for direct current extraction. When the substrate is electrically insulating such as a synthetic resin or the like, the surface on the side where the deposited film is formed is coated with Al. , Ag, Pt, Au, Ni, Ti, Mo, W,
Fe, V, Cr, Cu, stainless steel, brass, nichrome,
A so-called simple metal or alloy such as SnO ₂ , In ₂ O ₃ , ZnO, ITO, or a transparent conductive oxide (TCO) is subjected to surface treatment in advance by plating, vapor deposition, sputtering, or the like to form an electrode for extracting current. It is desirable to form it.

Of course, even if the substrate is made of an electrically conductive material such as a metal, the reflectance of long-wavelength light on the surface of the substrate can be improved, and the interaction of constituent elements between the substrate material and the deposited film can be improved. A different kind of metal layer or the like may be provided on the side of the substrate on which the deposited film is formed for the purpose of preventing diffusion or the like. Further, when the substrate is relatively transparent and a photovoltaic element having a layer structure in which light enters from the side of the substrate is used, a conductive thin film such as the transparent conductive oxide or a metal thin film is previously deposited. It is desirable to form it.

The surface of the substrate may be a so-called smooth surface or a fine uneven surface. In the case of a minute uneven surface, the uneven shape is spherical, conical,
When the shape is a pyramid or the like and the maximum height ( _Rmax ) is preferably 0.05 μm to 2 μm, light reflection on the surface becomes irregular reflection, and the optical path length of the reflected light on the surface increases. Bring.

The shape of the substrate can be a plate having a smooth surface or an uneven surface, a long belt, a cylindrical shape, or the like, depending on the application, and its thickness is such that a desired photovoltaic element can be formed. If the photovoltaic element is required to have flexibility, or if light is incident from the side of the substrate, it is possible that the function as the substrate is sufficiently exhibited. It can be as thin as possible. However, the thickness is usually 10 μm or more from the viewpoint of the production and handling of the substrate, the mechanical strength, and the like.

(Back Electrode, Light Reflecting Layer) The back electrodes 102 and 202 in the present invention are electrodes disposed on the back of the semiconductor layer in the light incident direction. Therefore, 102 in FIG.
Or when the substrate 101 is translucent and light is incident from the direction of the substrate, it is disposed at the position 106.

As the material of the back electrode, for example, gold,
Examples include metals such as silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel. Among them, metals having high reflectance, such as aluminum, copper, silver, and gold, are particularly preferable. In the case of using a metal having a high reflectance, the back electrode can also serve as a light reflecting layer for reflecting light that could not be absorbed by the semiconductor layer again to the semiconductor layer.

The shape of the back electrode may be flat, but it is more preferable that the back electrode has an uneven shape for scattering light.
By having an uneven shape that scatters light, it scatters long-wavelength light that could not be absorbed by the semiconductor layer, extends the optical path length in the semiconductor layer, improves the long-wavelength sensitivity of the photovoltaic element, and increases the short-circuit current. And the photoelectric conversion efficiency can be improved. Uneven shape for scattering the light, it is desirable the height difference of the unevenness of the peaks and valleys is 2.0μm from 0.2μm at R _max.

However, when the substrate also serves as the back electrode,
In some cases, it is not necessary to form the back electrode.

The back electrode is formed by a vapor deposition method, a sputtering method, a plating method, a printing method, or the like. When the back electrode is formed to have an uneven shape that scatters light, the formed metal or alloy film is formed by dry etching, wet etching, sandblasting, heating, or the like.
In addition, the above-mentioned metal or alloy can be deposited while heating the substrate to form an uneven shape for scattering light.

The back electrode 102 and the n-type semiconductor layer 10
Although not shown in the figure, a diffusion preventing layer made of conductive zinc oxide or the like may be provided between the first and third layers. The effect of the diffusion preventing layer is not only to prevent the metal element forming the back surface electrode 102 from diffusing into the n-type semiconductor layer, but also to provide a slight resistance value so that the back surface provided with the semiconductor layer interposed therebetween. To prevent short-circuiting caused by defects such as pinholes between the electrode 102 and the transparent electrode 106, and to produce multiple interference by a thin film and confine incident light to a photovoltaic element. Can be.

(Semiconductor Layer) As the material of the semiconductor layer in the present invention, for example, a material using a group IV element such as Si, C, Ge or the like, or a material using a group IV alloy such as SiGe, SiC, SiSn, etc. Used.

Among the above semiconductor materials, semiconductor materials particularly preferably used in the photovoltaic device of the present invention include, for example, a-Si: H (abbreviation for hydrogenated amorphous silicon), a -Si: F, a-Si: H: F, a-SiG
e: H, a-SiGe: F, a-SiGe: H: F, a
And group IV and group IV alloy-based amorphous semiconductor materials such as -SiC: H, a-SiC: F, and a-SiC: H: F.

The semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a source compound containing an element serving as a valence electron controlling agent or a forbidden band width controlling agent when forming a semiconductor layer is used alone, or mixed with the deposited film forming source gas or the diluent gas. What is necessary is just to introduce in a film space.

The semiconductor layer is controlled by valence electrons.
At least a portion thereof is doped p-type and n-type to form at least one set of pin junctions. And
By stacking a plurality of pin junctions, a so-called stack cell configuration is obtained.

As a method of forming a semiconductor layer, microwave plasma CVD, RF plasma CVD, light C
Various CVD methods such as VD method, thermal CVD method, MOCVD method, or various evaporation methods such as EB evaporation, MBE, ion plating, ion beam method, sputtering method,
It is formed by a spray method, a printing method, or the like. As a method adopted industrially, a plasma CVD method in which a raw material gas is decomposed by plasma and deposited on a substrate is preferably used. In addition, as the reaction device, a batch type device, a continuous film forming device, or the like can be used as desired.

Hereinafter, a semiconductor layer using a group IV or group IV alloy-based amorphous semiconductor material particularly suitable for the photovoltaic device of the present invention will be described in more detail.

(1) i-type Semiconductor Layer (Intrinsic Semiconductor Layer) Particularly in a photovoltaic device using a group IV or group IV alloy-based amorphous semiconductor material, an i-type layer used for a pin junction is exposed to irradiation light. It is an important layer for generating and transporting carriers.
Slightly p-type and slightly n-type layers can also be used as the i-type layer.

As described above, the group IV and group IV alloy-based amorphous semiconductor materials contain a hydrogen atom (H, D) or a halogen atom (X), which has an important function.

The hydrogen atoms (H, D) or the halogen atoms (X) contained in the i-type layer work to compensate for dangling bonds in the i-type layer, and the carrier in the i-type layer. To improve the product of the mobility and the lifetime. Further, it works to compensate for the interface state of each interface of the p-type layer / i-type layer and the n-type layer / i-type layer, and has the effect of improving the photovoltaic power, photocurrent and photoresponsiveness of the photovoltaic element. There is something.

The optimum content of hydrogen atoms and / or halogen atoms contained in the i-type layer is 1 to 40 at%. In particular, those having a large content of hydrogen atoms and / or halogen atoms distributed on each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer are preferred distribution forms,
The preferred range of the content of hydrogen atoms and / or halogen atoms near the interface is 1.1 to 2 times the content in the bulk. Further, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed in accordance with the content of silicon atoms.

In the stack type photovoltaic element, the material of the pin-junction i-type semiconductor layer close to the light incident side is a material having a wide band gap, and a material far away from the light incident side is p-type.
As a material for the in-junction i-type semiconductor layer, a material having a narrow band gap is preferably used.

Amorphous silicon and amorphous silicon germanium are formed by an element for compensating for dangling bonds.
a-Si: H, a-Si: F, a-Si: H: F, a-
SiGe: H, a-SiGe: F, a-SiGe: H:
It is written as F or the like.

[0084] Further, as a characteristic of the preferred i-type semiconductor layer for the photovoltaic element of the present invention, the content of hydrogen atoms (C _H) is, 1.0~25.0%, AM1.5,100
The photoelectric conductivity (σ _p ) under mW / cm ² simulated sunlight irradiation is
1.0 × 10 ⁻⁷ S / cm or more, the dark conductivity (σ _d )
1.0 × 10 ⁻⁹ S / cm or less, Urbach Energy by Constant Photocurrent Method (CPM)
Those having a local state density of 10 ¹⁷ / cm ³ or less are preferably used.

(2) P-type semiconductor layer or n-type semiconductor layer (doping layer) The p-type semiconductor layer or n-type semiconductor layer in the present invention is a layer characterizing the photovoltaic device of the present invention. It is an important layer that determines the characteristics.

As a material for the p-type semiconductor layer or the n-type semiconductor layer, a non-single-crystal material is preferably used. The non-single-crystal material of the present invention includes an amorphous material (denoted as a-), a microcrystalline material (denoted as μc-), and a polycrystalline material (pol).
y-).

As an amorphous material (denoted as a-) or a microcrystalline material (denoted as μc-), for example, a-
Si: H, a-Si: HX, a-SiC: H, a-Si
C: HX, a-SiGe: H, a-SiGe: HX, a
-SiGeC: H, a-SiGeC: HX, a-Si
O: H, a-SiO: HX, a-SiN: H, a-Si
N: HX, a-SiON: H, a-SiON: HX, a
—SiOCN: H, a-SiOCN: HX, μc-S
i: H, μc-Si: HX, μc-SiC: H, μc −
SiC: HX, μc-SiO: H, μc-SiO: H
X, μc-SiN: H, μc-SiN: HX, μc-S
iGeC: H, μc-SiGeC: HX, μc-SiO
N: H, μc-SiON: HX, μc-SiOCN:
H, μc-SiOCN: p-type valence electron controlling agent (Group III atom B, Al, Ga, In, T
l) and n-type valence electron controlling agents (atoms P and A of group V in the periodic table)
s, Sb, Bi) are added at a high concentration.

As the polycrystalline material (denoted as poly-), for example, poly-Si: H, poly-Si:
HX, poly-SiC: H, poly-SiC: H
X, poly-SiO: H, poly-SiO: HX,
poly-SiN: H, poly-SiN: HX, po
ly-SiGeC: H, poly-SiGeC: HX,
poly-SiON: H, poly-SiON: HX,
poly-SiOCN: H, poly-SiOCN: H
X, poly-Si, poly-SiC, poly-S
A p-type valence electron controlling agent (Group III atom B, Al, Ga, In, Tl) or n in iO, poly-SiN, etc.
Type valence electron control agents (Group V atoms P, As, S in the periodic table)
b, Bi) at a high concentration.

In particular, as the p-type layer or the n-type layer on the light incident side, a crystalline semiconductor layer with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable.

The addition amount of Group III atoms of the periodic table to the p-type layer and the addition amount of Group V atoms of the periodic table to the n-type layer are within the range of 0.1 to 1.0.
The optimal amount is 1 to 50 at%.

A hydrogen atom (H, D) or a halogen atom contained in the p-type layer or the n-type layer functions to compensate for dangling bonds of the p-type layer or the n-type layer, and This is to improve the doping efficiency of the layer. A hydrogen atom or a halogen atom added to the p-type layer or the n-type layer is 0.1 to 40 a.
t% is mentioned as the optimum amount. In particular, when the p-type layer or the n-type layer is crystalline, the number of hydrogen atoms or halogen atoms is 0.1 to
8 at% is mentioned as the optimum amount.

Further, those having a large content of hydrogen atoms and / or halogen atoms at each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer are mentioned as preferable distribution forms. A preferred range of the content of hydrogen atoms and / or halogen atoms in the vicinity of the interface is 1.1 to 2 times the content in the bulk.

As described above, by increasing the content of hydrogen atoms or halogen atoms near each interface between the p-type layer / i-type layer and the n-type layer / i-type layer, the defect level and mechanical strain near the interface can be improved. Can be reduced, and the photovoltaic power and the photocurrent of the photovoltaic device of the present invention can be increased.

The p-type layer and the n-type layer of the photovoltaic element preferably have an activation energy of 0.2 eV or less, and most preferably have an activation energy of 0.1 eV or less. The non-resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness of the p-type layer and the n-type layer is 1 to
50 nm is preferred, and 3 to 10 nm is optimal.

Further, the doping layer, which is a feature of the present invention, is formed by exposing the surface of the doping layer to a plasma containing an element for expanding the band gap of the doping layer after the deposition. Examples of the element that expands the band gap of the doping layer include C, O, and N when the main constituent element of the doping layer is Si.

Further, depending on the processing conditions of the plasma containing the element for expanding the band gap, the composition ratio of the element for expanding the band gap in the doping layer, which is a feature of the present invention, can be changed over the thickness direction. The part may be microcrystallized or polycrystallized.

(3) Method for Forming Semiconductor Layer A suitable method for forming a group IV and group IV alloy-based amorphous semiconductor layer suitable for the semiconductor layer of the photovoltaic device of the present invention is as follows. , An RF plasma CVD method, a microwave plasma CVD method, or the like, and a plasma CVD method using alternating current or high frequency.

In the microwave plasma CVD method, a material gas such as a raw material gas or a diluent gas is introduced into a deposition chamber (vacuum chamber) which can be reduced in pressure, and the inside pressure of the deposition chamber is kept constant while exhausting the gas by a vacuum exhaust pump. A microwave oscillated by a microwave power source is guided by a waveguide, introduced into the deposition chamber through a dielectric window (alumina ceramics or the like), and generates a plasma of a material gas to decompose the material. This is a method for forming a desired deposited film on a substrate arranged in the above-described manner, and can form a deposited film applicable to a photovoltaic device under a wide range of deposition conditions.

When the semiconductor layer for a photovoltaic device of the present invention is deposited by microwave plasma CVD, the substrate temperature in the deposition chamber is 100 to 450 ° C., and the internal pressure is 0.5 to 30 m.
Torr, microwave power is 0.01 to 1 W / c
m ² and the frequency of the microwave are preferably in the range of 0.1 to 10 GHz.

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 Torr, and the RF power is 0.001 to 5.
0 W / cm ² and a deposition rate of 0.01 to 3 nm / sec are preferable conditions.

The source gas suitable for depositing the group IV and group IV alloy amorphous semiconductor layer suitable for the photovoltaic device of the present invention includes a gasizable compound containing silicon atoms,
A gasizable compound containing a germanium atom, a gasifiable compound containing a carbon atom, a gasifiable compound containing a nitrogen atom, a gasifiable compound containing an oxygen atom, and the like, and a mixed gas of the compound can be given. it can.

As the gasizable compound containing a silicon atom, a chain or cyclic silane compound is used, and specifically, for example, SiH ₄ , Si ₂ H ₆ , Si
F ₄ , SiFH ₃ , SiF ₂ H ₂ , SiF ₃ H, Si ₃ H ₈ ,
SiD ₄ , SiHD ₃ , SiH ₂ D ₂ , SiH ₃ D, SiF
D ₃ , SiF ₂ D ₂ , Si ₂ D ₃ H ₃ , (SiF ₂ ) ₅ , (Si
F ₂ ) ₆ , (SiF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , Si ₂ H ₂
F ₄ , Si ₂ H ₃ F ₃ , SiCl ₄ , (SiCl ₂ ) ₅ , Si
Br ₄ , (SiBr ₂ ) ₅ , Si ₂ Cl ₆ , SiHCl ₃ , S
Examples thereof include those in a gas state or those which can be easily gasified, such as iH ₂ Br ₂ , SiH ₂ Cl ₂ , and Si ₂ Cl ₃ F ₃ .

Specifically, a gas containing a germanium atom
The compound which can be converted to is GeH_Four, GeD_Four, GeF_Four,
GeFH_Three, GeF_TwoH_Two, GeF_ThreeH, GeHD_Three, Ge
H_TwoD _Two, GeH_ThreeD, Ge_TwoH₆, Ge_TwoD₆Etc.
You.

Specifically, gasification containing a carbon atom can be performed.
As the compound, CH_Four, CD_Four, C _nH_{2n + 2}(N is integer
Number), C_nH_2n(N is an integer), C_TwoH_Two, C₆H₆, CO_Two,
CO and the like.

Examples of the nitrogen-containing gas include N ₂ , NH ₃ , and ND.
₃ , NO, NO ₂ and N ₂ O. Examples of the oxygen-containing gas include O ₂ , CO, CO ₂ , NO, NO ₂ , N ₂ O, and CH.
₃ CH ₂ OH, CH ₃ OH and the like.

In order to control valence electrons, a p-type layer or an n-type layer
Materials introduced into the mold layer include Group III atoms and Group V atoms in the periodic table.

As the starting material for introducing a group III atom effectively, specifically, for introducing a boron atom, B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H ₁₁ , B
_{6 H 1 0, B 6 H} 12, B 6 borohydride of H _14, etc., BF _3, B
Examples thereof include boron halides such as Cl ₃ .
In addition, AlCl ₃ , GaCl ₃ , InCl ₃ , TIC
l ₃ and the like can also be mentioned. Particularly, B ₂ H ₆ and BF ₃ are suitable.

Effectively used as a starting material for introducing a group V atom is, specifically, P for introducing a phosphorus atom.
Phosphorus hydride such as H ₃ , P ₂ H ₄ , PH ₄ I, PF ₃ , PF ₅ ,
Phosphorus halides such as PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , and PI ₃ are mentioned. In addition, AsH ₃ , AsF ₃ ,
AsCl ₃ , AsBr ₃ , AsF ₅ , SbH ₃ , SbF ₃ ,
SbF ₅ , SbCl ₃ , SbCl ₅ , BiH ₃ , BiC
l _3, BiBr _3, and the like can also be mentioned. Especially PH ₃ ,
PF ₃ is suitable.

The compounds capable of being gasified are H ₂ , H
The gas may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

Particularly, a microcrystalline or polycrystalline semiconductor or a-S
When depositing a layer having a small light absorption or a wide band gap such as iC: H, the source gas is diluted 2 to 100 times with hydrogen gas, and a relatively high microwave power or RF power is introduced. Is preferred.

(4) Method of Plasma Treatment of Doping Layer Hereinafter, a method of plasma treatment of the doping layer, which is a feature of the present invention, will be described.

In the plasma treatment of the doping layer, a material gas, a diluent gas, or the like is introduced into a deposition chamber (vacuum chamber) which can be decompressed, and the internal pressure of the deposition chamber is kept constant while evacuating by a vacuum pump. Glow discharge plasma that generates a plasma of a material gas by applying AC or high frequency is used. As the frequency, various frequencies from DC to microwaves of about 10 GHz can be used.

The material gas contains carbon, oxygen, nitrogen, etc., which are elements for expanding the band gap of the doping layer of the photovoltaic device of the present invention.

Specific examples of the gasizable compound containing a carbon atom include CH ₄ , CD ₄ , C _n H _{2n + 2} (n is an integer), C _n H _2n (n is an integer), C ₂ H ₂ , C ₆ H ₆ , CO ₂ ,
CO and the like. N ₂ , N
H ₃ , ND ₃ , NO, NO ₂ , and N ₂ O are mentioned.

The oxygen-containing gases include O ₂ , CO, CO ₂ ,
NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH and the like. Further, as the diluent gas, H ₂ , He, N
Gases such as e, Ar, Xe, and Kr can be used.

Further, since a semiconductor layer is not deposited, a source gas suitable for depositing a group IV or group IV alloy amorphous semiconductor layer may not be used. Also, when a source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layers is used, the pressure of the gas for generating plasma is set lower than that under normal deposition conditions so that a deposition reaction does not occur. It is desirable to lower the voltage, increase the DC voltage or AC power applied to the plasma, or increase the dilution ratio with the dilution gas.

As described above, the implantation of the element for expanding the band gap of the doping layer by the glow discharge plasma is completely different from the conventional ion implantation used for crystalline silicon or the like. In the conventional ion implantation, the ions are accelerated in a beam form, and the energy of the ions is high. On the other hand, the implantation by the glow discharge plasma has a low energy of the implanted material and is extremely shallow from the surface of the deposited layer. It is implanted only up to the region. Further, delicate control of the implantation depth is easy, and uniform implantation over a large area can be easily performed. Further, since the surface of the i-type semiconductor layer is not damaged by the accelerated ions, it is possible to form a doping layer having few localized levels without deteriorating the film quality of the deposited layer. Therefore, the doping layer can be formed uniformly over a large area with good film quality.

Suitable conditions for the glow discharge plasma depend on the material of the doping layer to be processed, the type of material gas, the frequency of power applied to the plasma, and the like. Indoor substrate temperature is 100-450 ° C, internal pressure is 0.5-30mTo
rr, the microwave power is preferably 0.01 to 1 W / cm ² , and the microwave frequency is preferably 0.1 to 10 GHz. DC, AC, LF or R
In the case of F plasma, the substrate temperature in the deposition chamber is 100 to 35.
0 ° C., internal pressure 0.1 to 10 Torr, power 0.01
５5.0 W / cm ² is a preferable condition.

Further, depending on the conditions of the glow discharge plasma, it is possible to control the depth and concentration of the element for expanding the band gap of the doping layer, and to change the crystallinity near the surface of the doping layer. It is. The control method is described below.

First, one is to control the pressure of the material gas. By lowering the pressure of the gas, the injection efficiency of the element that widens the band gap of the doping layer increases. Although the details of this mechanism have not been clarified, it is considered that when the gas pressure is reduced, the self-bias of the electrode is increased, so that the energy of positive ions decomposed in the plasma state is increased. It is also conceivable that the mean free path of positive ions is increasing.

It is also to control the DC voltage or AC power applied to the plasma. Increasing the DC voltage or the AC power increases the efficiency of injecting the element that widens the band gap of the doping layer. At the same time, the vicinity of the surface of the microcrystalline or polycrystalline doping layer can be made amorphous. Although the details of this mechanism have not been clarified, it is considered that when the DC voltage or the AC power is increased, the plasma potential is increased, and the energy of the positive ions decomposed in the plasma state is increased.

Further, a special effect is produced by the fact that hydrogen is contained in the mixed gas of the plasma processing. In other words, first, hydrogen ions or radicals are generated by the plasma, but the hydrogen ions or radicals have an etching action, so that the mixed gas of the aforementioned group IV and group IV alloy-based amorphous semiconductor layer is added to the mixed gas. Even when a source gas suitable for deposition is included, by increasing the dilution ratio with hydrogen gas, the deposition of the source gas can be suppressed, and an element for expanding the band gap of the doping layer can be implanted. .

Second, by implanting not only the element for expanding the band gap but also hydrogen atoms into the doping layer, the dangling bond (dangling bond) of the doping layer caused by the implantation of the element for expanding the band gap is implanted. ), And can increase the activation rate of the acceptor or the donor.

Third, by implanting hydrogen atoms near the surface of the doping layer, the band gap of the doping layer near the surface is further increased, and light absorption in the doping layer is reduced.

Fourth, the crystallinity near the surface of the doping layer can be increased by increasing the dilution ratio with hydrogen gas and increasing the DC voltage or AC power applied to the plasma at the same time.

(Transparent Electrode) The transparent electrode 10 of the present invention
Numeral 6 has both a role as an electrode on the light incident side for transmitting light and a role as an anti-reflection film by optimizing the film thickness. The transparent electrode 106 is required to have a high transmittance in a wavelength region where the semiconductor layer can absorb light and a low resistivity. Preferably, the transmittance at 550 nm is at least 80%, more preferably at least 85%. The resistivity is preferably 5 × 10
^-3 Ωcm or less, more preferably 1 × 10 ⁻³ Ωcm or less. As the material, for example, I
n ₂ O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), Zn
O, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂
A conductive oxide such as O ₃ , MoO ₃ , and Na _x WO _3, or a mixture thereof is preferably used. Further, an element (dopant) that changes the conductivity may be added to these compounds.

As an element (dopant) for changing the conductivity, for example, when the transparent electrode 107 is ZnO,
Al, In, B, Ga, Si, F, etc., In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc., and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

As the method for forming the transparent electrode 106, an evaporation method, a CVD method, a spray method, a spin-on method, a dipping method, or the like is suitably used.

(Current Collecting Electrode) The current collecting electrode 10 of the present invention
7 is formed on a part of the transparent electrode 106 as necessary when the resistivity of the transparent electrode 106 cannot be sufficiently reduced;
It functions to lower the resistivity of the electrode and lower the series resistance of the photovoltaic element. As the material, for example, a metal such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, zirconium, or an alloy such as stainless steel, or a powdered metal is used. Conductive paste and the like. The shape is formed, for example, in a branch shape as shown in FIG. 3 so as not to block incident light to the semiconductor layer as much as possible.

Also, in the entire area of the photovoltaic device,
The area occupied by the collecting electrode is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less.

Further, a pattern of the collecting electrode is formed by using a mask, and the forming method includes a vapor deposition method, a sputtering method,
A plating method, a printing method, or the like is used.

When a photovoltaic device (module or panel) having a desired output voltage and output current is manufactured using the photovoltaic device of the present invention, the photovoltaic devices of the present invention are connected in series or in series. They are connected in parallel, protective layers are formed on the front and back surfaces, and output output electrodes and the like are attached. When the photovoltaic elements of the present invention are connected in series, a diode for preventing backflow may be incorporated.

[0133]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a photovoltaic element made of a non-single-crystal silicon-based semiconductor material will be described in detail, but the present invention is not limited to this.

Example 1 In this example, the single-cell type photovoltaic element shown in FIG. 1 was produced using the deposition apparatus shown in FIG. In this example, when the element that enlarges the band gap of the doping layer D is α, the surface of the doping layer D contains the α after forming the doping layer D and before forming the i-type semiconductor layer. The case of exposure to plasma was examined.

In the following, the method of making the same will be described according to the procedure. (1) A stainless steel support 101 having a thickness of 0.5 mm and a size of 50 × 50 mm ² was subjected to ultrasonic cleaning with acetone and isopropanol, and dried with warm air. Thereafter, a 0.3 μm-thick Ag light-reflecting layer and a 350 μm-thickness
A reflection enhancement layer of ZnO having a layer thickness of 1.0 μm was formed at a temperature of 0 ° C. to form a back electrode 102. After these steps, the substrate 4
90.

(2) Using the deposition apparatus 400, the substrate 49
On each of the semiconductor layers, a semiconductor layer was formed. The deposition apparatus 400 can perform both the microwave plasma CVD method and the RF plasma CVD method.

A raw material gas cylinder (not shown) is connected to this deposition apparatus through a gas introduction pipe. The raw material gas cylinders were all purified to ultra-high purity, and were SiH ₄ gas cylinder, SiF ₄ gas cylinder, SiH ₄ / H ₂ (SiH ₄ gas diluted with H ₂ , dilution degree: 10%) gas cylinder, C
H ₄ gas cylinder, C ₂ H ₆ gas cylinder, GeH ₄ gas cylinder, GeF ₄ gas cylinder, Si ₂ H ₆ gas cylinder, PH ₃ /
H ₂ (dilution: 2%) gas cylinder, BF ₃ / H ₂ (dilution: 1%) gas cylinder, H ₂ gas cylinder, He gas cylinder, NH ₃ gas cylinder, O ₂ / He (dilution degree: 1%) gas cylinder, NO A gas cylinder was connected.

(3) The substrate 490 is placed in the load chamber 40
The load chamber 401 was evacuated by a vacuum evacuation pump (not shown) until the pressure reached about 1 × 10 ⁻⁵ Torr.

(4) The gate valve 406 was opened and transported into the transport chamber 402 and the deposition chamber 417, which were previously evacuated by a vacuum exhaust pump (not shown). The back surface of the substrate 490 is heated by a substrate heating heater 410.
Then, the inside of the deposition chamber 417 was evacuated by a vacuum evacuation pump (not shown) until the pressure reached about 1 × 10 ⁻⁵ Torr. Preparation for film formation was completed as described above.

(5) RF n-type layer made of a-Si (RF
To form an n-type semiconductor layer formed by a plasma CVD method, H ₂ gas is introduced into the deposition chamber 417 through a gas introduction pipe 429, and H ₂ gas is supplied at 200 scc.
The valve (not shown) was opened so as to reach m, and adjustment was performed with a mass flow controller (not shown). Deposition chamber 417
The inside pressure was adjusted to 1.1 Torr by a conductance valve (not shown).

(6) The substrate heating heater 410 is set so that the temperature of the substrate 490 becomes 350 ° C. When the substrate temperature is stabilized, the SiH ₄ gas and PH ₃ / H ₂ gas are not introduced into the deposition chamber 417. The gas was introduced through the gas introduction pipe 429 by operating the illustrated valve. At this time, the pressure in the deposition chamber 417 is adjusted to 1.1 Torr by adjusting the mass flow controller (not shown) so that the SiH ₄ gas is ₂ sccm, the H ₂ gas is 50 sccm, and the PH ₃ / H ₂ gas is 0.5 sccm. Was adjusted as follows.

(7) The power of the RF high frequency (hereinafter abbreviated as “RF”) power supply 422 is set to 0.005 W / cm ² , and RF power is introduced into the plasma forming cup 420.
A glow discharge is caused to start forming an RF n-type layer on the substrate.
F power is turned off, glow discharge is stopped, and the RF n-type layer 103 is turned off.
Finished the formation.

(8) SiH into the deposition chamber 417
_After stopping the inflow of ₄ gases, PH ₃ / H ₂ , and continuing the flow of H ₂ gas into the deposition chamber for 5 minutes, stopping the inflow of H ₂ , and vacuuming the deposition chamber and the gas pipe to 1 × 10 ⁻⁵ Torr. Exhausted.

(9) Before the formation of the i-type semiconductor layer, the surface of the doping layer D is exposed to plasma containing an element (α) for expanding the band gap of the doping layer D.
_Four gases and He gas were introduced into the deposition chamber 417 through a gas introduction pipe 429 by operating a valve (not shown).
At this time, 10 sccm of CH ₄ gas and 30 s of He gas were used.
The pressure in the deposition chamber 417 was adjusted to 0.5 Torr by adjusting with a mass flow controller so as to be ccm. The power of the RF power source 422 was set to 0.06 W / cm ² ,
RF power was introduced to 20 to generate glow discharge and exposed to the plasma containing α for 300 seconds to form an n-type layer made of a-SiC.

(10) The i-type layer 104 made of a-Si was formed by microwave plasma CVD. First,
The substrate 490 was transferred by opening the gate valve 407 into the transfer chamber 403 and the i-type layer deposition chamber 418 that were previously evacuated by a vacuum pump (not shown). The back surface of the substrate 490 is heated by a substrate heating heater 411.
Then, the inside of the i-type layer deposition chamber 418 is heated to about 1 × 10 ⁻⁵ Torr by a vacuum exhaust pump (not shown).
Evacuation was performed until the pressure became r.

(11) To form an i-type layer, the substrate 49
Substrate heating heater 4 so that the temperature of
11 was set, and when the substrate was sufficiently heated, a valve (not shown) was gradually opened to allow SiH ₄ gas and H ₂ gas to flow into the i-type layer deposition chamber 418 through the gas introduction pipe 449. At this time, the mass flow controllers (not shown) were adjusted so that the SiH ₄ gas was 50 sccm and the H ₂ gas was 100 sccm. The opening of the conductance valve (not shown) was adjusted so that the pressure in the i-type layer deposition chamber 418 became 5 mTorr.

(12) The RF power supply 424 is set to 0.50 W / c
m ² and applied to the bias bar 428. afterwards,
The power of a microwave power supply (not shown) was set to 0.20 W / cm ² , and the i-type layer deposition chamber 418 was passed through the microwave introduction waveguide 426 and the microwave introduction window 425.
Microwave power is introduced into the inside, a glow discharge is generated, and a shutter 427 is opened to start forming an i-type layer on the n-type layer. The discharge was stopped, the output of the bias power supply 424 was turned off, and the formation of the i-type layer 104 was completed.

(13) Close the valve (not shown) to open the i-type layer.
SiH into deposition chamber 418 _FourStop gas flow
Into the i-type layer deposition chamber 418 for 2 minutes._TwoGas
After continuing the flow, the valve (not shown) is closed and the i-type layer deposition chamber is closed.
1 × 10 in chamber 418 and gas pipe^-FiveTor
e was evacuated to r.

(14) In the following procedure, a p-type semiconductor layer 105 made of μc-Si (microcrystal silicon)
Was formed.

First, the transfer chamber 404 and p which have been previously evacuated by a vacuum pump (not shown)
The gate valve 408 was opened into the mold layer deposition chamber 419 to transfer the substrate 490. The back surface of the substrate 490 was heated by being brought into close contact with a heater 412 for heating the substrate, and the inside of the p-type layer deposition chamber 419 was evacuated by a vacuum exhaust pump (not shown) until the pressure became about 1 × 10 ⁻⁵ Torr.

The substrate heating heater 412 is set so that the temperature of the substrate 490 becomes 230 ° C. When the substrate temperature is stabilized, H ₂ gas, SiH ₄ / H ₂ gas, BF ₃ / H ₂
The gas was introduced into the deposition chamber 419 through a gas introduction pipe 469 by operating a valve (not shown). At this time, a valve (not shown) is operated to supply 50 sccm of H ₂ gas and Si gas.
H ₄ / H ₂ gas is 0.5 sccm, BF ₃ / H ₂ gas is 0.1 sccm.
The pressure in the deposition chamber 419 was adjusted to 2.0 Torr by adjusting the mass flow controller so that the pressure became 5 sccm.
The opening of the conductance valve (not shown) was adjusted so that

The power of the RF power supply 423 is set to 0.15 W / cm
² , RF power is introduced into the plasma forming cup 421 to generate glow discharge, and p
The formation of the mold layer was started, and when a layer thickness of 10 nm was formed, the RF power was turned off to stop glow discharge, and the formation was completed.

(15) The valve (not shown) is closed, and SiH ₄ / H ₂ gas and BF ₃ /
Stopping the flow of H ₂ gas for 3 minutes, after which continued to flow H ₂ gas into the p-type layer deposition chamber 419, stopping the inflow of H ₂ closes the valve (not shown), p-type layer deposition chamber 41
The inside of 9 and the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr.

(16) The unload chamber 40 previously evacuated by a vacuum pump (not shown)
5, the substrate 490 was transported by opening the gate valve 409, and a leak valve (not shown) was opened to leak the unload chamber 405. (17) On the p-type layer, as the transparent conductive layer 106, a layer thickness of 7
0 nm of ITO was vacuum deposited by a vacuum deposition method.

(18) A mask having a comb-shaped hole is placed on the transparent conductive layer 106, and Cr (40 nm) / Ag (100
0 nm) / Cr (40 nm) and the comb-shaped current collecting electrode 107 of FIG. 3 was vacuum-deposited by a vacuum deposition method. Thus, the creation of the photovoltaic element has been completed. This photovoltaic element is called (SC Ex. 1).

(Comparative Example 1-1) In this example, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D was not exposed to the plasma containing α. Is different from (Example 1).

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC ratio 1-1).

In the following, (Example 1) and (Comparative Example 1-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 1 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 1-1) (SC actual 1). (FF).

[0161]

[Table 1] From Table 1, it was found that the photovoltaic element of (SC Ex. 1) had better open-circuit voltage (V _OC ) and short-circuit current (J _SC ) and better photoelectric conversion efficiency (η).

(Comparative Example 1-2) In this example, the following three points are different from (Example 1). (A) When forming an RF n-type layer, SiH ₄ gas is used for 2 seconds.
ccm, CH ₄ gas 0.2 sccm, H ₂ gas 50 s
The mass flow controller was adjusted so that ccm and PH ₃ / H ₂ gas became 0.5 sccm, and the pressure in the deposition chamber was adjusted so as to be 1.1 Torr.

(B) When forming the RFn-type layer, the power of the RF power supply is set to 0.025 W / cm ² , RF power is introduced into the plasma forming cup, glow discharge is generated, and RFn is formed on the substrate. Start forming a mold layer, 10 nm thick
A-SiC RFn-type layer was formed.

(C) Prior to forming the i-type semiconductor layer, the step of exposing the surface of the doping layer to plasma containing the element (α) for expanding the band gap of the doping layer was omitted.

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC ratio 1-2).

Hereinafter, (Example 1) and (Comparative Example 1-
An evaluation test performed on each of the six photovoltaic elements obtained in 2) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 2 shows the photoelectric conversion efficiency (η), open circuit voltage (V _OC ), short circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 1-1) (SC actual 1). (FF).

[0169]

[Table 2] From Table 2, it was found that the photovoltaic element of (SC Ex. 1) had better open-circuit voltage (V _OC ) and better photoelectric conversion efficiency (η).

Further, in order to see unevenness and variation in the substrate,
On the p-type layer, 25 holes (area 0.25 cm)^Two)of
Place an open mask and use it as a transparent conductive layer with a thickness of 70 nm.
Was formed by a vacuum evaporation method. Table 3 shows such
The open circuit voltage (V _OC), Fill factor (FF)
Is a result of examining unevenness and variation in the substrate. However
The maximum value on the same substrate was set to 1.

[0171]

[Table 3] From Table 3, it was found that the photovoltaic element of (SC Ex. 1) had improved uniformity of photoelectric conversion characteristics because the unevenness and variation in the substrate were smaller.

Example 2 In this example, as shown below, conditions for forming an RF n-type layer made of μc-Si, conditions for exposing the surface of the doping layer to plasma, and a-SiG
The conditions for forming the MWi-type layer made of e are different from those of the first embodiment.

(A) Conditions for Forming RF n-Type Layer The RF n-type layer was deposited by RF plasma CVD under the condition of μc-Si. At this time, the SiH ₄ / H ₂ gas is ₄ sc
cm, H ₂ gas is 100 sccm, PH ₃ / H ₂ gas is 1
The pressure was adjusted with a mass flow controller to be sccm, and the pressure in the deposition chamber was adjusted to be 0.5 Torr. The substrate heating heater was set so that the substrate temperature became 380 ° C., and when the substrate temperature was stabilized, the power of the RF power supply was set to 0.04 W / cm ² and RF power was introduced into the plasma forming cup. , A glow discharge is caused to start forming an RF n-type layer on the substrate,
A 0 nm RF n-type layer was formed.

(B) Conditions for exposing the surface of the doping layer to plasma Before the formation of the i-type semiconductor layer, NH is used to expose the surface of the doping layer D to plasma containing the element α for expanding the band gap of the doping layer D. _Three gases and He gas were introduced into the deposition chamber through a gas introduction pipe by operating a valve (not shown). At this time, 5 sccm of NH ₃ gas and H
e gas was adjusted with a mass flow controller to 35 sccm, and the pressure in the deposition chamber was 2.0 To
rr. Reduce the power of the RF power source to 0.06
W / cm ² , RF power was introduced into the plasma forming cup to generate glow discharge, and the RF n-type layer was exposed to plasma containing an element (α) for expanding the band gap for 100 seconds, and the surface of the RF n-type layer was exposed. Was made amorphous to form a-SiN, thus completing the formation of the n-type layer of the present invention.

(C) Conditions for Forming MWi-Type Layer The MWi-type layer (i-type semiconductor layer formed by microwave CVD) was made of a-SiGe. In order to form an MWi-type layer, a substrate heating heater is set so that the substrate temperature becomes 380 ° C., and when the substrate is sufficiently heated, a valve (not shown) is gradually opened, and a SiH ₄ gas, a GeH ₄ gas , H
_Two gases were introduced into the i-type layer deposition chamber through the gas introduction pipe. At this time, the SiH ₄ gas is 50 sccm, G
The mass flow controllers (not shown) adjusted the eH ₄ gas to 35 sccm and the H ₂ gas to 120 sccm. The pressure in the i-type layer deposition chamber is 6 mTo
The opening of the conductance valve (not shown) was adjusted so as to be rr. Next, the RF power was set to 0.2 W / cm ² and applied to the bias bar. Thereafter, the power of a microwave power supply (not shown) was set to 0.1 W / cm ² , microwave power was introduced into the i-type layer deposition chamber, glow discharge was generated, and the shutter was opened to place the RF power on the RFi-type layer. MW
The formation of the i-type layer was started. When the i-type layer having a thickness of 0.1 μm was formed, the microwave glow discharge was stopped, and the formation of the MWi-type layer was completed.

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC Ex. 2).

(Comparative Example 2-1) In this example, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D was not exposed to the plasma containing α. Is different from (Example 2).

The other points were the same as in (Example 2). The photovoltaic element produced in this example was called (SC ratio 2-1).

In the following, (Example 2) and (Comparative Example 2-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 4 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 2-1) (SC actual 2). (FF).

[0182]

[Table 4] From Table 4, it was found that the photovoltaic element of (SC Ex. 2) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

Example 3 In this example, as shown below, the conditions for forming the RF n-type layer made of a-Si, the conditions for exposing the surface of the doping layer to plasma, and the method for forming the MWi-type layer made of a-SiC were used. The forming conditions are different from those of the first embodiment.

(A) Conditions for Forming RF n-Type Layer The RF n-type layer was deposited by RF plasma CVD under the condition that a-Si was obtained. At this time, the SiH ₄ gas was 2 sccm,
H ₂ gas is 50 sccm, PH ₃ / H ₂ gas is 0.5 sc
cm with a mass flow controller,
The pressure in the deposition chamber was adjusted to be 1.1 Torr. The substrate heating heater is set so that the substrate temperature becomes 380 ° C., and when the substrate temperature becomes stable, R
The power of the F power source was set to 0.005 W / cm ² , RF power was introduced into the plasma forming cup, glow discharge was generated, and the formation of an RF n-type layer on the substrate was started.
m RF n-type layers were formed.

(B) Conditions for exposing the surface of the doping layer to plasma Before forming the i-type semiconductor layer, the surface of the doping layer D is exposed to plasma containing the element α for expanding the band gap of the doping layer D. _Four gases and H ₂ gas were introduced into the deposition chamber through a gas introduction pipe by operating a valve (not shown). At this time, 10 sccm of CH ₄ gas and H ₂
The gas was adjusted with a mass flow controller to 30 sccm, and the pressure in the deposition chamber was 1.0 Torr.
r was adjusted. 0.03W RF power
/ Cm ² , RF power is introduced into the plasma forming cup to generate glow discharge, and the RF n-type layer is exposed to plasma containing an element (α) for expanding the band gap for 120 seconds to expose the surface of the RF n-type layer. The formation of the n-type layer according to the present invention was completed by crystallizing the material into μc-SiC.

(C) Conditions for Forming MWi-Type Layer The MWi-type layer (i-type semiconductor layer formed by microwave CVD) was made of a-SiC. In order to form the MWi-type layer, a substrate heating heater is set so that the substrate temperature becomes 380 ° C., and when the substrate is sufficiently heated, a valve (not shown) is gradually opened, and a SiH ₄ gas and a CH ₄ gas are used. , H ₂ gas was caused to flow into the i-type layer deposition chamber through a gas introduction pipe. At this time, the mass flow controllers (not shown) were adjusted so that the SiH ₄ gas became 50 sccm, the CH ₄ gas became 35 sccm, and the H ₂ gas became 120 sccm. The pressure in the i-type layer deposition chamber was adjusted to 6 mTorr. Next, the RF power supply was turned on at 0.2 W / cm.
Set to ² and applied to the bias bar. Thereafter, the power of a microwave power supply (not shown) was set to 0.1 W / cm ² , and i
Microwave power was introduced into the mold layer deposition chamber, glow discharge was generated, and the shutter was opened to start forming an MWi type layer on the RFi type layer. When an i-type layer having a layer thickness of 0.1 μm was formed, Stop microwave glow discharge, M
The creation of the Wi type layer has been completed.

The other points were the same as in (Example 1). The photovoltaic element created in this example was called (SC Ex. 3).

(Comparative Example 3-1) In this example, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D was not exposed to the plasma containing α. Is different from (Example 3).

The other points were the same as in (Example 3). The photovoltaic element produced in this example was called (SC ratio 3-1).

Hereinafter, (Example 3) and (Comparative Example 3-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 5 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 3-1) (SC actual 3). (FF).

[0193]

[Table 5] From Table 5, it was found that the photovoltaic element of (SC Ex. 3) was superior in the open-circuit voltage (V _OC ) and the short-circuit current (J _SC ) and in the photoelectric conversion efficiency (η).

(Embodiment 4) In this embodiment, instead of (Example 1) having the light incident side as the p-layer and the layer structure being the substrate / n-layer / i-layer / p-layer, the light incident side is the n-layer. The layer structure is defined as
The difference is that the layers are p-layer / i-layer / n-layer.

In the following, in the fabrication of the photovoltaic device of this example, the conditions for forming the RFp type layer made of a-Si, the conditions for exposing the surface of the doping layer to plasma, and the conditions for forming the MWi type layer made of a-SiC , And RF comprising a-Si
The conditions for forming the n-type layer will be described.

(A) Conditions for Forming RFp-Type Layer The RFp-type layer was deposited by RF plasma CVD under the condition of a-Si. The substrate heating heater was set so that the substrate temperature became 350 ° C., and when the substrate temperature was stabilized, H ₂ gas, SiH ₄ / H ₂ gas, and BF ₃ / H ₂ were introduced into the deposition chamber. At this time, H ₂ gas is 50 scc
m, the mass flow controller was adjusted so that the SiH ₄ / H ₂ gas was 0.5 sccm and the BF ₃ / H ₂ gas was 5 sccm, and the pressure in the deposition chamber was adjusted to be 2.0 Torr. 0.15W / c RF power
m ² , RF power was introduced into the plasma forming cup to generate glow discharge, the formation of an RFp-type layer on the substrate was started, and the RF power was turned off when the RFp-type layer having a thickness of 10 nm was formed. Thus, the glow discharge was stopped, and the formation of the p-type layer was completed.

(B) Conditions for exposing the surface of the doping layer to plasma Before forming the i-type semiconductor layer, the surface of the doping layer D is exposed to plasma containing the element α for expanding the band gap of the doping layer D. ₂ / He gas was introduced into the deposition chamber through a gas introduction pipe by operating a valve (not shown). At this time, the O ₂ / He gas was adjusted by the mass flow controller to be 40 sccm, and the pressure in the deposition chamber was adjusted to be 0.5 Torr. The power of the RF power source is set to 0.06 W / cm ² , the RF power is introduced into the plasma forming cup, a glow discharge is generated, and the plasma containing the element (α) for expanding the band gap of the RF p-type layer for 100 seconds. And the surface of the RF p-type layer was changed to a-SiO to complete the formation of the p-type layer of the present invention.

(C) Conditions for Forming MWi-Type Layer An MWi-type layer (i-type semiconductor layer formed by microwave CVD) was prepared under the same conditions as in (Example 1).

(D) Conditions for Forming RF n-Type Layer The RF n-type layer was deposited under the condition of a-Si by RF plasma CVD. At this time, 50 sccm of H ₂ gas and S
iH ₄ gas is 2 sccm, PH ₃ / H ₂ gas is 0.5 sc
cm with a mass flow controller,
The pressure in the deposition chamber was adjusted to 0.5 Torr. The substrate heating heater is set so that the substrate temperature becomes 230 ° C., and when the substrate temperature is stabilized, R
The power of the F power source was set to 0.005 W / cm ² , RF power was introduced into the plasma forming cup, glow discharge was generated, and the formation of an RF n-type layer on the substrate was started.
m RF n-type layers were formed. Thereafter, the RF power was turned off to stop glow discharge, and the formation of the n-type layer was completed.

The other points were the same as in (Example 1). The photovoltaic element created in this example was called (SC Ex. 4).

(Comparative Example 4-1) In this example, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D was not exposed to the plasma containing α. Is different from (Example 4).

The other points were the same as in (Example 4). The photovoltaic element produced in this example was called (SC ratio 4-1).

Hereinafter, (Example 4) and (Comparative Example 4-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 6 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 4-1) (SC actual 4). (FF).

[0206]

[Table 6] From Table 6, it was found that the photovoltaic element of (SC Ex. 4) was superior in the open-circuit voltage (V _OC ) and the short-circuit current (J _SC ), and in the photoelectric conversion efficiency (η).

(Embodiment 5) In this embodiment, instead of forming the single cell type photovoltaic element shown in FIG. 1 in (Example 1), a triple cell type (pin type) shown in FIG. (Stacked cell type) composed of a structure in which the semiconductor junction is laminated three times. The photovoltaic element of this example used the deposition apparatus of FIG.

The layer structure of the photovoltaic element of this example is
1 / back surface electrode 202 / first pin junction 214 / second pin junction 215 / third pin junction 216 / transparent electrode 212 / collecting electrode 213. Further, each pin junction had the following layer configuration from the substrate side.

The layer structure of each pin junction in this example is shown below. Here, an element that enlarges the band gap of the doping layer D is represented by α.

The first pin junction 214 is
In order from the side of No. 2, an RF n-type layer (n1 layer) 203 / a-Si made of μc-Si whose surface has been made amorphous (a-SiC) by exposure to the plasma containing α
Layer 251 / a-SiGe MWi type layer (i1
Layer) RFi-type layer 261 / μc composed of 204 / a-Si
A p-type layer (p1 layer) 205 made of -Si was used.

[0211] The second pin junction 215 is connected to the first pin junction 215.
Μc-Si whose surface has been made amorphous (a-SiC) by exposing it to the plasma containing α in order from the junction 214 side.
N-type layer (n2 layer) 206 of the present invention composed of: RFi-type layer 252 composed of a-Si / MWi composed of a-SiGe
Type layer (i1 layer) 207 / RFi type layer 2 made of a-Si
A p-type layer (p2 layer) 208 made of 62 / μc-Si was used.

The third pin junction 216 is connected to the second pin junction 216.
Μc-Si whose surface is made amorphous (a-SiC) by exposing it to the plasma containing α in order from the side of the junction 215.
N-type layer (n3 layer) 209 of the present invention consisting of: RFi-type layer 210 consisting of a-Si / p-type layer (p3 layer) 211 consisting of μc-Si.

In the following, a method for forming the first pin junction 214 will be described according to the procedure. The numbers in parentheses indicate the steps.

(1) In order to form an RF n-type layer made of μc-Si, a substrate heating heater was set at a substrate temperature of 380 ° C., and SiH ₄ gas, H ₂ gas, and PH ₃ / H ₂ gas were deposited. It was introduced into the chamber. At this time, SiH ₄ gas is 2
The mass flow controller was adjusted so that the sccm, the H ₂ gas was 50 sccm, and the PH ₃ / H ₂ gas was 0.5 sccm, and the pressure in the deposition chamber was adjusted to be 1.1 Torr. 0.04W / c RF power
m ² , RF power was introduced into the plasma forming cup to generate glow discharge, the formation of the RF n-type layer on the substrate was started, and the RF power was turned off when the RF n-type layer having a thickness of 10 nm was formed. To stop the glow discharge, and to stop the n-type μc-S
Finished forming i.

(2) Before the formation of the i-type semiconductor layer, CH ₄ gas and He gas are supplied into the deposition chamber to expose the surface of the doping layer D to plasma containing the element α for expanding the band gap of the doping layer D. Was introduced. At this time,
The mass flow controller was used to adjust CH ₄ gas to 10 sccm and He gas to 30 sccm, and the pressure in the deposition chamber was adjusted to 1.0 Torr. The power of the RF power source is set to 0.06 W / cm ² , RF power is introduced into the plasma forming cup to generate glow discharge, and the RF n-type layer is exposed to plasma containing the element α for expanding the band gap for 100 seconds. The formation of the n-type layer of the present invention was completed by amorphizing the surface of the RF n-type layer into a-SiC.

(3) RFi-type layer 25 made of a-Si
1. MWi type layer 204 made of a-SiGe, a-Si
RFi type layer 261 made of RF plasma CVD
Method, microwave plasma CVD method, RF plasma CVD
Formed by the method.

(3-1) To form an RFi-type layer, the temperature of the substrate was set to 350 ° C., and when the substrate was sufficiently heated, Si ₂ H ₆ gas and H ₂ gas were supplied to the i-type layer deposition chamber. Allowed to flow in. At this time, 4 scc of Si ₂ H ₆ gas
Each mass flow controller was adjusted so that m and H ₂ gas became 100 sccm. The pressure in the i-type layer deposition chamber was adjusted to 0.8 Torr.
Next, the RF power source 424 was set to 0.007 W / cm ² , applied to a bias bar to generate a glow discharge, and opened a shutter to start forming an i-type layer on the RF n-type layer. When the 10-nm i-type layer was formed, the RF glow discharge was stopped, the output of the RF power supply was turned off, and the formation of the RFi-type layer was completed.

(3-2) To form an MWi-type layer, the temperature of the substrate was set at 380 ° C., and when the substrate was sufficiently heated, SiH ₄ gas, GeH ₄ gas, and H ₂ gas were added to the i-type layer. Flowed into the deposition chamber. At this time, the respective mass flow controllers were adjusted so that the SiH ₄ gas became 50 sccm, the GeH ₄ gas became 35 sccm, and the H ₂ gas became 120 sccm. The pressure in the i-type layer deposition chamber was adjusted to 6 mTorr. Next, set the RF power supply to 0.2
W / cm ² was set and applied to the bias bar. afterwards,
The power of the microwave power supply was set to 0.1 W / cm ² and i
Microwave power was introduced into the mold layer deposition chamber, glow discharge was generated, and the shutter was opened to start forming an MWi type layer on the RFi type layer. When an i-type layer having a layer thickness of 0.1 μm was formed, The microwave glow discharge was stopped, the output of the bias power supply was turned off, and the formation of the MWi-type layer was completed.

(3-3) In order to form an RFi-type layer, the temperature of the substrate was set at 250 ° C., and when the substrate was sufficiently heated, Si ₂ H ₆ gas and H ₂ gas were added to the i-type layer deposition chamber. Allowed to flow in. At this time, Si ₂ H ₆ gas is ₂ scc
m, H ₂ gas was adjusted with mass flow controllers each so that 80 sccm. The pressure in the i-type layer deposition chamber was adjusted to be 0.7 Torr. Next, an RF power source was set to 0.007 W / cm ² , a bias was applied to the bias bar, a glow discharge was generated, and a shutter was opened to start forming an i-type layer on the RF n-type layer and a layer thickness of 20 nm. When the i-type layer was formed, the RF glow discharge was stopped, the output of the RF power supply was turned off, and the formation of the RFi-type layer was completed.

(3-4) A p-type semiconductor layer 205 made of μc-Si was formed. Set the temperature of the substrate to 230 ° C,
When the substrate temperature is stabilized, H ₂ gas, SiH ₄ / H ₂
A gas, BF ₃ / H ₂ gas, was introduced into the deposition chamber.
At this time, the mass flow controller was adjusted so that the H ₂ gas became 50 sccm, the SiH ₄ / H ₂ gas became 0.5 sccm, and the BF ₃ / H ₂ gas became 0.5 sccm, and the pressure in the deposition chamber was 2.0 Torr. It was adjusted to become. The power of the RF power supply 423 was set to 0.15 W / cm ² , RF power was introduced into the cup for plasma formation, glow discharge was generated, and the formation of a p-type layer made of μc-Si was started. When 10 nm was formed, the RF power was turned off to stop glow discharge, and the formation was completed. Through the above steps, the formation of the first pin junction 214 has been completed.

In the following, a method for forming the second pin junction 215 will be described. (4) In the step of forming the second pin junction 215, a-S
Only the conditions for forming the MWi type layer made of iGe are different from those of the step of forming the first pin junction 214. What changed in the conditions for forming the MWi type layer made of a-SiGe
50 sccm of H ₄ gas, 30 sccm of GeH ₄ gas,
The point is that the H ₂ gas is set to 120 sccm. Through the above steps, formation of the second pin junction 215 has been completed.

In the following, a method of forming third pin junction 216 will be described according to the procedure. The numbers in parentheses indicate the steps.

(5) RF n-type layer 20 made of μc-Si
To form No. 9, a substrate heating heater was set at a substrate temperature of 350 ° C. Otherwise, the RF n-type layer of the present invention was formed in the same manner as the RF n-type layer in the second pin junction.

(6) To form the RFi-type layer 210,
The temperature of the substrate was set to 200 ° C., and when the substrate was sufficiently heated, Si ₂ H ₆ gas and H ₂ gas were introduced into the gas introduction pipe 449.
Through the chamber into the i-type layer deposition chamber. At this time, the Si ₂ H ₆ gas was ₂ sccm, and the H ₂ gas was 80 sccc.
m was adjusted by each mass flow controller. The pressure in the i-type layer deposition chamber is 0.6 Torr
r was adjusted. Next, set the RF power supply to 0.07 W
/ Cm ² , and applied to a bias rod to generate glow discharge and open a shutter to start the creation of an RFi-type layer. When an i-type layer having a thickness of 120 nm is created, the RF glow discharge is stopped. , Turn off the output of the RF power supply,
The creation of the i-type layer has been completed.

(7) P-type semiconductor layer 2 made of μc-Si
To form 11, the substrate temperature was set at 170 ° C. Other than that, it was formed by the same method as the p-type layer in the second pin junction. By the above steps, the third pin
The formation of the joint 216 has been completed.

(8) ITO having a thickness of 70 mm was vacuum-deposited as a transparent conductive layer 212 on the RFp-type layer 211 by a vacuum deposition method. Next, a mask having a comb-shaped hole is placed on the transparent conductive layer 212, and Cr (40 nm) / Ag (1000
nm) / Cr (40 nm) comb-shaped collecting electrode 21
3 was vacuum-deposited by a vacuum deposition method. The photovoltaic element produced in this example was called (SC Ex. 5).

(Comparative Example 5-1) In this example, after forming the doping layer D and before forming the i-type semiconductor layer, the surface of the doping layer D was not exposed to the plasma containing α. Is different from (Example 5).

The other points were the same as in (Example 5). The photovoltaic element produced in this example was called (SC ratio 5-1).

In the following, (Example 5) and (Comparative Example 5-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 7 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 5-1) (SC actual 5). (FF).

[0232]

[Table 7] From Table 7, it was found that the photovoltaic element of (SC Ex. 5) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

(Comparative Example 5-2) In this example, the following three points are different from (Example 5). (A) When forming an RF n-type layer, SiH ₄ gas is used for 2 seconds.
ccm, CH ₄ gas 0.2 sccm, H ₂ gas 50 s
The mass flow controller was adjusted so that ccm and PH ₃ / H ₂ gas became 0.5 sccm, and the pressure in the deposition chamber was adjusted so as to be 1.1 Torr.

(B) When forming the RFn-type layer, the power of the RF power source is set to 0.025 W / cm ² , RF power is introduced into the plasma forming cup, glow discharge is generated, and RFn is formed on the substrate. Start forming a mold layer, 10 nm thick
A-SiC RFn-type layer was formed.

(C) Before forming the i-type semiconductor layer, the step of exposing the surface of the doping layer D to plasma containing the element (α) for expanding the band gap of the doping layer D was omitted.

The other points were the same as in (Example 5). The photovoltaic element produced in this example was called (SC ratio 5-2).

In the following, (Example 5) and (Comparative Example 5-
An evaluation test performed on each of the six photovoltaic elements obtained in 2) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 8 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 5-2) (SC actual 5). (FF).

[0240]

[Table 8] From Table 8, it was found that the photovoltaic element of (SC Ex. 5) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

Also, in order to see unevenness and variations in the substrate,
On the p-type layer, 25 holes (area 0.25 cm)^Two)of
Place an open mask and use it as a transparent conductive layer with a thickness of 70 nm.
Was formed by a vacuum evaporation method. Table 9 shows such
The open circuit voltage (V _OC), Fill factor (FF)
Is a result of examining unevenness and variation in the substrate. However
The maximum value on the same substrate was set to 1.

[0242]

[Table 9] From Table 9, it was found that the photovoltaic element of (SC Ex. 5) has improved uniformity of the photoelectric conversion characteristics since the unevenness and variation in the substrate are smaller.

[0243]

As described above, according to the first aspect of the present invention, the p-type semiconductor layer, the i-type semiconductor layer, and the n-type semiconductor layer are stacked to form a pin-type semiconductor junction, and at least a part thereof is formed. In a method of manufacturing a photovoltaic device using an amorphous semiconductor, a p-type or n-type doping layer is formed, and before the i-type semiconductor layer is formed, the surface of the doping layer is Exposure to a plasma containing a bandgap-enlarging element increases the optical bandgap of the doped layer, resulting in a high density of activated acceptors or donors, low activation energy, and a large optical bandgap It was possible to form a doping layer compatible with a small coefficient.

[0244] According to the invention of claim 2, the manufacturing method of the foregoing photovoltaic element, by forming the Doping layer, absorption of light is reduced by doping layer,
The built-in potential of the photovoltaic element increased, the open-circuit voltage (V _OC ) and the short-circuit current (J _SC ) of the photovoltaic element increased, and the photoelectric conversion efficiency improved.

According to the third aspect of the present invention, a pin-type semiconductor junction is formed by laminating a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer using at least a part of an amorphous semiconductor. In a so-called stack type photovoltaic element in which a plurality of layers are stacked, by forming at least a part of the doping layer by the above-described method of manufacturing a photovoltaic element, the built-in potential of the pin junction in that part increases. As a result, the open-circuit voltage (V _OC ) of the entire stack type photovoltaic element increased, the light absorption by the doping layer decreased, the short-circuit current (J _SC ) increased, and the photoelectric conversion efficiency improved. Further, when used in a doping layer above the tunnel junction of a stack type photovoltaic element, the interdiffusion of the valence electron controlling agent at the tunnel junction decreases, and the open voltage (V _OC ) and fill factor (F.
F.) increased, and the photoelectric conversion efficiency improved.

[0246] According to the invention of claim 4, the composition ratio of the element to expand the band gap contained in Doping layer
The over its thickness direction, by varying, built-in potential further increases of the photovoltaic element, to increase the open circuit voltage of the photovoltaic element (V _OC) is the photoelectric conversion efficiency is further improved.

[0247] According to the invention of claim 5, Doping layer over its thickness direction, by a part is finely crystallized or polycrystalline, further increase in potential of the photovoltaic element As a result, the open-circuit voltage (V _OC ) of the photovoltaic element increased, the light absorption by the doping layer further decreased, the short-circuit current (J _SC ) increased, and the photoelectric conversion efficiency further improved.

Furthermore, as an effect common to the claims of the present invention, the doping layer can be formed uniformly over a large area, and the photovoltaic element can be formed uniformly over a large area. Since the thickness of the doping layer is small, its thickness distribution and characteristic distribution over a large area strongly affect the characteristic distribution over a large area of the photovoltaic element. Since the characteristic distribution can be made uniform,
The characteristic distribution of the photovoltaic element also becomes uniform.

Further, according to the present invention, the condition of high ion energy is not required at the time of depositing the doping layer, and the stress inside the doping layer is reduced by the plasma treatment. The adhesion was improved, and the production yield of the photovoltaic element was improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer configuration of a single-cell type photovoltaic element according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a layer configuration of a stack cell type photovoltaic element according to the present invention.

FIG. 3 is a schematic view of an example of a photovoltaic element according to the present invention as viewed from above.

FIG. 4 is a schematic explanatory view of a multi-chamber separation type deposition apparatus used for forming a photovoltaic element according to the present invention.

[Explanation of symbols]

101, 201 substrate, 102, 202 back electrode, 103 n layer, 104 i layer, 105 p layer, 106, 212 transparent electrode, 107, 213 current collecting electrode, 203 n1 layer, 204 i1 layer, 205 p1, 206 n2 layer 207 i2 layer, 208 p2 layer, 209 n3 layer, 210 i3 layer, 211 p3 layer, 214 first pin junction, 215 second pin junction, 216 third pin junction, 251, 252, 261, 262 RFi Mold layer, 400 multi-chamber separation type deposition apparatus, 401 load lock chamber, 402 transfer chamber for n-type layer (or p-type layer), 403 transfer chamber for MW-i layer (or RF-i layer), 404 transfer chamber for p-type layer (or n-type layer), 405 unload chamber, 406, 407, 408, 409 gate valve, 410, 411, 412 413 substrate heater, 413 substrate transport rail, 417 deposition chamber for n-type layer (or p-type layer), 418 deposition chamber for MW-i layer (or RF-i layer), 419 p-type layer (or n) Chamber, 420, 421 RF introduction cup, 422, 423 RF power supply, 424 bias application power supply, 425 MW introduction window, 426 MW introduction waveguide, 427 MW-i layer deposition shutter 428, a bias electrode, 429, a gas supply pipe for an n-type layer (or p-type layer) deposition gas supply facility, 449 a gas supply pipe for a MW-i layer (or RF-i layer) deposition gas supply facility, 469 p-type A gas supply pipe of a gas supply facility for layer (or n-type layer) deposition.

Claims (5)

(57) [Claims] 1. A has a semiconductor junction of the p-type semiconductor layer and a pin-type in which two doped layers made of n-type semiconductor layer are stacked via an i-type semiconductor layer, and at least the i
In the method for manufacturing a photovoltaic device in which the crystal form of the doping layer D located below the type semiconductor layer is non-single-crystal, the element that enlarges the band gap of the doping layer D is α. A method for manufacturing a photovoltaic device, comprising: exposing the surface of the doping layer D to the plasma containing α after forming D and before forming the i-type semiconductor layer. 2. A has a semiconductor junction of the p-type semiconductor layer and a pin-type in which two doped layers made of n-type semiconductor layer are stacked via an i-type semiconductor layer, and at least the i
In a photovoltaic device in which the crystal form of the doping layer D located below the type semiconductor layer is non-single-crystal, the doping layer D is formed by the method for manufacturing a photovoltaic device according to claim 1. A photovoltaic element characterized by the above-mentioned. 3. A stacked cell type having a structure in which a pin-type semiconductor junction in which two doping layers composed of a p-type semiconductor layer and an n-type semiconductor layer are laminated via an i- type semiconductor layer is laminated twice or more. A photovoltaic device, wherein at least one of the doping layers D is formed by the method for manufacturing a photovoltaic device according to claim 1. 4. The method according to claim 1, wherein said α contained in said doping layer D is
4. The photovoltaic device according to claim 2, wherein the composition ratio of the photovoltaic device changes over the thickness direction. 5. The photovoltaic device according to claim 2, wherein the doping layer D is partially crystallized or polycrystallized in the thickness direction. .