JP2834627B2 - Photovoltaic element and power generation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pin type photovoltaic device and a power generation system made of a non-single-crystal silicon semiconductor material. In particular, a photovoltaic element in which a doping layer and an i-type layer are formed by a microwave plasma CVD method (MWPCVD method), and a semiconductor layer made of a non-single-crystal silicon-based semiconductor material (hereinafter simply referred to as a semiconductor layer) contains fluorine. It is about. The present invention also relates to a photovoltaic device having excellent productivity. In addition, the present invention relates to a power generation system using the photovoltaic element.

[0002]

2. Description of the Related Art In recent years, photovoltaic elements have been energetically studied using the MWPCVD method, which has a higher deposition rate and an excellent source gas utilization efficiency. For example, as an example of forming an i-type layer by the MWPCVD method, see “a-Si solar cell by microwave plasma CVD method”, Kazufumi Higashi, Takeshi Watanabe, Juichi Shimada, Proceedings of the 50th JSAP pp. 566. And the like. In this photovoltaic element, an i-type layer having good quality and a high deposition rate is obtained by forming the i-type layer by the MWPCVD method.

As an example in which a doping layer is formed by the MWPCVD method, for example, ◆ “High Efficiency”
ncy Amorphous Solar Cell
Employing ECR-CVD Process
d p-TypeMicrocrystalline
SiC Film ", Y. Hattori, D. Kru
angam, T .; Toyama, H .; Okamoto
andY. Hamakawa, Proceedings
of the International PVS
EC-3 Tokyo Japan 1987 pp.
171. ◆ "HIGH-CONDUCTIVE WID
E BAND GAP P-TYPE a-SiC: H
PREPARED BY ECR CVD AND
ITS APPLICATION TO HIGH E
FFICIENCY a-Si BASIS SOLA
R CELLS ", Y. Hattori, D. Krua
ngam, K .; Katou, Y .; Nitta, H .; Ok
amoto andY. Hamakawa, Proce
edings of 19th IEEEPhotov
oltaic Specialists Confer
ence pp. 1987. 689. And the like. In these photovoltaic elements, a high quality p-type layer is obtained by using the MWPCVD method for the p-type layer.

However, in these examples, the MWPCVD method is not used for forming both the i-type layer and the p-type layer.
At present, i-type layers formed by MWPCVD and MWPCV
When the doping layers formed by the method D are stacked, many defect levels are generated at the interface, and it is considered that a photovoltaic element having good characteristics has not been obtained.

[0005] Further, studies have been made on a non-single-crystal silicon-based semiconductor layer containing fluorine and a photovoltaic element using the same. For example, ◆ “Research on practical application of amorphous solar cells, Research on manufacturing technology for amorphous solar cells with high reliability”,
Overview of Sunshine Project R & D. Solar cell energy1. Light utilization technology VOL. 1985 pp. I. 231
-I. 243 1986. ◆ "The chemical
l and configurational bass
is of high efficiency amo
rphotophotovoltaic cell
s ", Ovshinsky S.R., Proceedi
ngs of 17th IEEE Photovol
taic Specialists Conferen
ce 1985 pp. 1365. ◆ “Prepara
Tion and properties of sp
buttered a-Si: H: F films ", B
eyer W, Chevallier J, Reich
elt K, Solar Energy Materi
al vol. 9, No2, pp. 229-245 1
983. ◆ "Development of the
scientific and technical b
asis for integrated amorp
house silicon modules. Res
ear on a-Si: F: H (B) allo
ys and module testingat I
ET-CIEMAT. ", Gutierrez M
T, P Delgado L, Photovolt, P
lower Gener. Pp. 70-75 198
8. ◆ "The effect of fluorin
e on the photovoltaic pro
parties of amorphossilic
on. ", Konagai M, Nishihata
K, Takahashi K, Komori K, Pr
receiveds of 15th IEEE Ph
otovoltaic Specialists Co
nreference 1981 pp. 906. And the like. However, even in these examples, the photodegradation phenomenon and the thermal stability are mentioned, but the relationship between the fluorine layer thickness direction change and the photoelectric conversion efficiency, or the hydrogen layer thickness direction change, or vibration degradation There is no mention of the relationship. In these examples, a high-quality doping layer is obtained, but a photovoltaic element having high photoelectric conversion efficiency has not been obtained.

Conventionally, in a photovoltaic device having a pin structure made of a non-single-crystal silicon-based semiconductor material, there are various photovoltaic devices in which the i-type layer contains silicon atoms and germanium atoms and the band gap is changed. Proposals have been made. For example, $ "Optimum dep
position conditions fora-
(Si, Ge): H using a triode-
configured rf glow disc
harge system ", JA Bragagn
olo, P .; Littlefield, A .; Mastr
Ovitoand G. Storti, Proceed
ings of 19th lEEEE Photovo
Itaic Specialists Conferen
ce1987 pp. 878. ◆ "Efficienc
y improvement in amorphou
s-SiGe: H solar cells and
its application to tandem
type solar cells ", S. Yoshi
ida, S .; Yamanaka, M .; Konagai
and K. Takahashi, Proceedin
gs of 19th lEEEE Photovolt
aic Specialists Conference
1987pp. 1101. ◆ "Preparatio
n of high quality a-SiGe:
H Films and it's applicati
on to the high efficiency
triple-junction amorphous
solar cells ", K. Sato, K. Ka
wabata, S .; Terazono, H .; Sasak
i, M. Deguchi, T .; Itagaki, H .; M
Orikawa, M .; Aiga and K.S. Fuji
Kawa, Proceedings of 20th
IEEE Photovoltaic Specili
sts Conference 1988 pp. 7
3. ◆ USP 4,816,082 has been reported.

[0007] A theoretical study of the characteristics of a photovoltaic device having a changing band gap is described in, for example, ◆ “A Nove
l design for amorhouse sil
icon alloy solar cells ",
S. Guha, J .; Yang, A .; Pawlikew
icz, T .; Glatfilter, R.A. Ross, a
nd S.D. R. Ovshinsky, Proceedi
ngs of 20th IEEE Photovoltt
aic Specialists Conference
1988 pp. 79. ◆ "Numerical m
modeling of multijunction
amorphous silicon based P
-IN solar cells ", AH Paw
likiewicz and S. Guha, Proc
eating of 20th IEEE Photo
volatileSpecialists Confere
nce 1988 pp. 251 etc. have been reported.

In such a conventional photovoltaic device, p
/ I, i-type layer in which the band gap is changed at the interface for the purpose of preventing recombination of photoexcited carriers near the i / n interface, increasing the open-circuit voltage, and improving the hole carrier range. Is formed. However, even in these examples, the photodeterioration phenomenon and the photoelectric conversion efficiency are mentioned, but the relation with the vibration deterioration and the relation with the delamination are not described.

In the above-mentioned conventional photovoltaic device, when the MWPCVD method is used for both the formation of the i-type layer and the formation of the doping layer, the recombination of photoexcited carriers near the p / i interface and the n / i interface, It is desired to improve the open circuit voltage and the hole carrier range.

The doping layer and the i-type layer are formed by MWPCV.
The photovoltaic device formed by the method D has a problem that the photoelectric conversion efficiency is reduced (light deterioration) when the photovoltaic device is irradiated with light.

Further, the doping layer and the i-type layer are formed by MWPC.
The photovoltaic element formed by the VD method has a problem that distortion occurs near the interface between the doping layer and the i-type layer, and the photoelectric conversion efficiency is reduced (vibration degradation) when placed in an environment where vibration is present for a long time.

Further, in the above-described photovoltaic element, light deterioration and vibration deterioration when the apparatus is placed in a high-temperature environment for a long time are remarkable.

Further, in the above-described photovoltaic element, light deterioration and vibration deterioration when the apparatus is placed in a high-humidity environment for a long time were remarkable.

Further, the non-single-crystal silicon-based semiconductor layer containing fluorine is extremely harder than that containing no fluorine.
There was a problem that it was easily peeled.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photovoltaic element which solves the above-mentioned conventional problems. That is, an object of the present invention is to provide a conventional photovoltaic element having an improved deposition rate and an improved photoelectric conversion efficiency.

Another object of the present invention is to provide a photovoltaic element in which light deterioration and vibration deterioration are suppressed.

Still another object of the present invention is to control light deterioration and vibration deterioration of a photovoltaic element in a high temperature environment.

Still another object of the present invention is to control light deterioration and vibration deterioration of a photovoltaic element in a high humidity environment.

Still another object of the present invention is to provide a photovoltaic element in which a semiconductor layer does not peel even when the photovoltaic element is placed in such an environment.

Still another object of the present invention is to provide a photovoltaic device having excellent productivity.

Still another object of the present invention is to provide a power generation system using a photovoltaic element which has achieved the above object.

[0022]

SUMMARY OF THE INVENTION The present invention has been found as a result of intensive studies to solve the conventional problems and to achieve the above-mentioned object. , A p-type layer, an i-type layer, and an n-type layer made of a non-single-crystal silicon-based semiconductor material containing hydrogen are sequentially laminated on a substrate, and the i-type layer is made of fluorine and germanium or /
And a tin, and formed by the microwave plasma CVD method, the p-type layer, n
At least one of the mold layers has a laminated structure of a layer (MW doping layer) formed by a microwave plasma CVD method and a layer (RF doping layer) formed by an RF plasma CVD method, and The doping layer is arranged so as to be sandwiched between the MW doping layer and the i-type layer, and the content of germanium and / or tin contained in the i-type layer changes smoothly in the layer thickness direction. It is characterized by the following.

In a preferred embodiment of the present invention, at least one of the two interfaces of the i-type layer is in the vicinity of the interface.
A photovoltaic element in which the content of germanium or / and tin in the mold layer is minimized, and the content is maximized on the p-type layer side from the center position of the i-type layer.

Further, a preferred embodiment of the present invention is a photovoltaic device in which the i-type layer contains both a valence electron controlling agent as a donor and a valence electron controlling agent as an acceptor.

A preferred embodiment of the present invention is a photovoltaic device having an i-type layer (RF-i layer) formed by RF plasma CVD between the i-type layer and the RF doping layer.

Further, a desirable mode of the present invention is a photovoltaic device in which the RF-i type layer contains both a valence electron controlling agent as a donor and a valence electron controlling agent as an acceptor.

In a preferred embodiment of the present invention, the MW doping layer, RF doping layer, RF-i layer, i
Near at least one of the two interfaces of the mold layer,
This is a photovoltaic element in which the hydrogen content of the layer is maximum.

Further, as a desirable mode of the present invention, the MW doping layer, RF doping layer, RF-i layer, i
Near at least one of the two interfaces of the mold layer,
This is a photovoltaic device in which the content of the valence electron controlling agent in the layer is maximum.

A desirable mode of the present invention is a photovoltaic device in which at least one of the i-type layer, the RF-i layer, the MW doping layer, and the RF doping layer contains oxygen and / or nitrogen atoms. .

Further, a desirable mode of the present invention is a photovoltaic device in which at least one of the RF-i layer, the MW doping layer and the RF doping layer contains fluorine.

Further, as a desirable mode of the present invention, the content of fluorine contained in the i-type layer, the RF-i layer, the MW doping layer, and the RF doping layer changes smoothly in the layer thickness direction, and at least This is a photovoltaic element having a minimum content near one interface.

Further, the power generation system of the present invention monitors the voltage and / or current of the above-mentioned photovoltaic element and outputs the electric power from the photovoltaic element to a storage battery and / or an external load. And a storage battery for storing power from the photovoltaic element and / or supplying power to an external load.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1A is a schematic explanatory view of a photovoltaic element of the present invention. In FIG. 1A, a photovoltaic element of the present invention is formed by a substrate 101, a MWn CVD method, a MWn type layer 102 having an n-type conductivity, and an RFn formed by an RFPCVD method and having an n-type conductivity. Mold layer 103, M
I-type layer 104 formed by WPCVD and containing hydrogen, fluorine and germanium or / and tin, RFPCV
RF p-type layer 10 formed by method D and having p-type conductivity
5. MWp-type layer 106 having p-type conductivity, formed by MWPCVD method, transparent electrode 107, and current collecting electrode 10
8 and so on.

FIG. 1B is another example of a schematic explanatory view of the photovoltaic element of the present invention. In FIG. 1B, the photovoltaic device of the present invention has a substrate 111 and an n-type conductive type.
Layer 112, i-type layer 114, RFp-type layer 115, MWp
It comprises a mold layer 116, a transparent electrode 117, a current collecting electrode 118, and the like.

FIG. 1C is another example of a schematic explanatory view of the photovoltaic element of the present invention. In FIG. 1C, a photovoltaic element of the present invention includes a substrate 121, an MWn-type layer 122, an RF
n-type layer 123, i-type layer 124, p having p-type conductivity
It comprises a mold layer 125, a transparent electrode 127, a current collecting electrode 128, and the like.

1A to 1C, an n-type layer,
The p-type layer is formed by RFPCVD or MWPCVD, but is preferably formed by RFPCVD.

Further, as shown in FIGS. 1 (a) to 1 (c), p
In addition to the photovoltaic element having the in-type structure, a photovoltaic element having a nip-type structure in which the stacking order of the n-type layer and the p-type layer may be reversed. Further, as shown in FIG. 1 (a) to FIG.
In a photovoltaic element having a stacked structure, i formed by a RFPCVD method between a doping layer having a stacked structure and an i-type layer.
Photovoltaic elements having a mold layer (RF-i layer) as shown in FIGS. 2A to 2C may be used.

Further, the doping layer having the laminated structure of the present invention may be, for example, an RFp type layer / MWp type layer / RFp type layer / i type layer, an i type layer / RFn type layer / MWn type layer / RFn type layer. (RF / MW) _n / RF may have a laminated structure composed of three or more layers, or MWp-type layer / R
A (MW / RF) _n- type laminated structure such as an Fp-type layer / MWp-type layer / RFp-type layer / i-type layer may be used.

Further, the photovoltaic element of the present invention is
A structure in which pin structures such as a structure and a pinpinpin structure are stacked may be used.

Further, the photovoltaic device of the present invention has a nipnip
It may be a laminated structure or a nip structure such as a nipnipnip structure.

In the photovoltaic device of the present invention, a doping layer,
In forming the i-type layer, since the MWPCVD method is used, the deposition rate is high, the throughput can be improved, and further, the utilization efficiency of the source gas can be improved, and the productivity is excellent. Things.

In the photovoltaic device of the present invention, since the doping layer is formed by the MWPCVD method, a doping layer having good characteristics as a photovoltaic device can be obtained.
That is, the doping layer is excellent as a doping layer because it has good light transmittance, high electric conductivity, and low activation energy, and is particularly effective as a doping layer on the light incident side. Further, a high-quality microcrystalline silicon-based semiconductor material or a high-quality amorphous silicon-based semiconductor material having a wide band gap can be formed relatively easily because it is formed by the MWPCVD method. Is effective as

Further, in the photovoltaic device of the present invention, since the doping layer is formed by the MWPCVD method, light deterioration of the photovoltaic device, particularly deterioration of the open-circuit voltage can be suppressed.

Although the detailed mechanism is unknown, it is considered as follows. Generally, it is considered that dangling bonds generated by light irradiation become recombination centers of carriers and deteriorate the characteristics of the photovoltaic element. MWPC
Doping layer (MW doping layer) formed by VD method
Is formed at a deposition rate of 2 nm / sec or more, so that the introduced valence electron controlling agent is not activated 100%,
It is considered that even if a dangling bond is generated, the inactive valence electron controlling agent terminates the dangling bond. Therefore, it is considered that the characteristics of the photovoltaic element, in particular, the decrease in the open-circuit voltage can be suppressed.

Since there is a doping layer (RF doping layer) formed by RFPCVD between the i-type layer formed by MWPCVD and the doping layer (MW doping layer) formed by MWPCVD, The level can be reduced, and the photoelectric conversion efficiency can be improved. The detailed mechanism is unknown, but is considered as follows.

The RF doping layer is formed at a low power at which a gas phase reaction is unlikely to occur, and the deposition rate is 1 nm / sec or less. As a result, the packing density is increased, and when the layer is stacked with the i-type layer, the interface state of each layer is reduced. In particular, the deposition rate of the i-type layer is 5 nm.
In the case of / sec or more, immediately after exciting or stopping the glow discharge by the microwave, the vicinity of the surface of the i-type layer is not sufficiently relaxed, so that the surface level increases.

By forming the i-type layer on the RF doping layer having a low deposition rate, the initial film of the i-type layer immediately after the occurrence of the glow discharge is affected by the underlayer, so that the packing density is increased and the dangling is increased. It is considered that the layer has few ring bonds and the surface level is reduced.

Further, by forming an RF doping layer having a low deposition rate on the surface of the i-type layer, the surface level of the i-type layer is reduced by annealing due to diffusion of hydrogen atoms which occurs simultaneously with the formation of the RF doping layer. It is thought that we can do it.

Further, by making the content of the valence electron controlling agent in the RF doping layer lower than the content of the valence electron controlling agent in the MW doping layer, the open voltage and the fill factor of the photovoltaic element can be improved. .

In addition, the photovoltaic element of the present invention is hardly deteriorated by vibration. Although the detailed mechanism is unknown, the MW doping layer having a very different constituent element ratio and i
By providing the RF doping layer between the mold layers, the local flexibility is increased, the internal stress between the MW doping layer and the i-type layer can be reduced, and the generation of a defect level due to the internal stress can be prevented. It can be considered that the photovoltaic element can be prevented from lowering in photoelectric conversion efficiency even if it is subjected to vibration for a long period of time. This is particularly effective when the hydrogen content is high at both interfaces of the RF doping layer.

It is generally known that the band gap becomes smaller as the germanium and / or tin content in the i-type layer made of an amorphous silicon semiconductor material is increased.

In the photovoltaic element of the present invention, the content of germanium and / or tin in the i-type layer changes smoothly in the layer thickness direction. By doing so, the photoelectric conversion efficiency is improved. That is, for example, as shown in FIG. 3A, the content of germanium or / and tin is reduced on the p-type layer side and the n-type layer side of the i-type layer, and the content of germanium or / and tin is maximized. 4A, the band gap of the i-type layer is maximized on the p-type layer side and the n-type layer side, and the p-type layer inside the bulk is provided, as shown in FIG. Is the smallest on the side. Therefore, the electric field in the conduction band increases on the p-type layer side of the i-type layer,
Electrons and holes are efficiently separated, and recombination of electrons and holes near the interface between the p-type layer and the i-type layer can be reduced. In addition, back diffusion of electrons into the p-type layer can be suppressed. Further, the electric field of the valence band increases from the i-type layer toward the n-type layer, and recombination of electrons and holes excited on the n-type layer side of the i-type layer can be reduced.

By reducing the content of germanium and / or tin near the interface between the doping layer and the i-type layer, the open-circuit voltage and fill factor of the photovoltaic element can be improved.

Further, by containing less germanium and / or tin in the vicinity of the interface than in the inside, it is possible to reduce the internal stress caused by a sudden change in the constituent elements peculiar to the interface. As a result, it is possible to control that the photoelectric conversion efficiency decreases even if the device is subjected to vibration for a long time. It is particularly effective when a heterojunction (Si / SiGe, SiC / SiGe, etc.) is provided between the i-type layer and the doping layer.

Generally, it is considered that there are many interface orders and internal stresses at the heterojunction interface. In the photovoltaic device of the present invention, by containing a small amount of germanium or / and tin near the interface of the heterojunction, the flexibility near the heterointerface can be increased, the internal stress can be reduced, and the interface state can be reduced. .

Hereinafter, an example of a desirable change pattern of the germanium or / and tin content of the i-type layer in the photovoltaic device of the present invention, which is considered from the change in the band gap in the layer thickness direction, will be described with reference to the drawings. I do.

FIG. 3A shows an example in which the germanium and / or tin content is rapidly changed on the p-type layer side as described above, and the maximum value of the content is on the p-type layer side inside the bulk. .

In this case, the band gap becomes as shown in FIG. 4A. When light is incident from the p-type layer side, a high electric field near the interface between the p-type layer and the i-type layer and the n-type layer The high voltage field near the interface of the mold layer can be more effectively used, and the collection efficiency of electrons and holes that are photoexcited in the i-type layer can be improved. Further, when light is incident from the n-type layer side in the nip type photovoltaic element, the change pattern may be reversed in the layer thickness direction. This is particularly effective when the band gap of the i-type layer is small.

FIG. 3B shows an example in which the maximum value of the content is at the interface with the p-type layer by slowly changing from the p-type layer side to the n-type layer side. In this case, the band gap is shown in FIG.
As shown in (b), the electric field of the valence band can be increased over the entire region of the i-type layer. In particular, the carrier range for holes can be improved, and the fill factor can be improved. When light is incident on the n-type photovoltaic element from the n-type layer side, the change pattern may be reversed in the layer thickness direction. When the content of germanium and / or tin in the i-type layer is relatively large,
Especially effective.

In FIG. 3C, the p-type layer side of the i-type layer and the n-type layer
This is an example in which the content of germanium and / or tin changes rapidly on the mold layer side. In this case, the band gap is as shown in FIG. 4C, and the electric field of the conduction band can be increased on the p-type layer side of the i-type layer, and in particular, the back diffusion of electrons into the p-type layer can be suppressed. Can be. In addition, the electric field of the valence band can be increased on the i-type layer side and the n-type layer side, and in particular, back diffusion of holes into the n-type layer can be suppressed. Further, the present invention is particularly effective for a photovoltaic element having an i-type layer having a relatively small content of germanium and / or tin. That is, when light is incident from the p-type layer side in FIG. 4C, the i-type layer having a large band gap cannot absorb light sufficiently,
Photoexcited carriers near the interface between the i-type layer and the n-type layer are separated by a strong electric field near the interface without recombination, and the collection efficiency can be increased. Further, it is effective for a photovoltaic element having a light reflection layer. That is, in the photovoltaic element having the light reflection layer, the light is incident from both layers, so that the collection efficiency can be similarly increased.

In the photovoltaic device of the present invention, the i-type layer, the MW doping layer, the RF doping layer, and the RF-i layer contain fluorine so that the photovoltaic device is placed in a high-temperature environment for a long time. In this case, light deterioration and vibration deterioration can be suppressed.

In addition, it is possible to suppress light deterioration and vibration deterioration when the photovoltaic element is placed in a high humidity environment for a long time.

In addition, when the photovoltaic element is placed in a high-temperature, high-humidity environment for a long period of time, light deterioration and vibration deterioration can be suppressed.

Although the details of the mechanism are unknown, the electric energy of the fluorine atom is very large, and the binding energy of the fluorine atom and the silicon atom, the fluorine atom and the germanium atom, and the binding energy of the fluorine atom and the tin atom are large. Therefore, it is considered that a thermally and mechanically stable and chemically stable semiconductor layer can be obtained.

Further, like hydrogen, fluorine can terminate dangling bonds in the semiconductor layer, so that defect levels can be reduced. Further, since the atomic radius is very small as in the case of hydrogen, no structural distortion is induced even when the semiconductor layer is contained in a semiconductor layer.

In the present invention, it is preferable that fluorine is contained in a small amount near the interface of the semiconductor layer. As will be described later, in the photovoltaic element of the present invention, a large amount of hydrogen is contained in the vicinity of the interface of the semiconductor layer to reduce structural distortion. In order to keep the packing density of the semiconductor layer high, it is considered that it is desirable to decrease the fluorine content in the vicinity of the interface where the hydrogen content is increased. By doing so, it is possible to reduce the level induced by the bond between hydrogen and fluorine in the semiconductor or the decrease in the distance between them.

In addition, by including fluorine in the doping layer, the doping efficiency can be improved, and the light transmittance can be improved, so that the photoelectric conversion efficiency can be improved. Further, by including fluorine in the doping layer, a microcrystalline silicon-based semiconductor material can be obtained with relatively low power, so that a doping layer made of the microcrystalline silicon-based semiconductor material is formed without adversely affecting the underlying layer. And the interface state can be reduced. Therefore, the photoelectric conversion efficiency can be improved.

In the photovoltaic device of the present invention, since the MW doping layer is formed by the MWPCVD method, a particularly good doping layer can be obtained.

Further, in the photovoltaic device of the present invention, since the fluorine-containing doping layer has a laminated structure, the effect of containing fluorine (suppression of light deterioration and vibration deterioration in a high temperature and high humidity environment) is obtained. ) Can be exhibited even more. Further, even when the photovoltaic element is placed in such an environment, the semiconductor layer does not peel off.

Hereinafter, an example of a desirable change pattern of the fluorine content of the i-type layer in the photovoltaic device of the present invention will be described with reference to the drawings.

FIG. 5A shows an example in which the fluorine content is rapidly changed on the p-type layer side, and the maximum value of the content is on the p-type layer side inside the bulk. In this case, it is desirable that the change pattern of the hydrogen content in the layer thickness direction be as shown in FIG. When light is incident on the n-type photovoltaic element from the n-type layer side, the change pattern may be reversed in the layer thickness direction. It is particularly effective when the p / i interface is composed of a heterojunction.

FIG. 5B shows an example in which the p-type layer is slowly changed from the p-type layer to the n-type layer, and the maximum value of the fluorine content is at the interface with the p-type layer. In this case, the change pattern of the hydrogen content in the layer thickness direction is preferably that shown in FIG.
When light is incident from the n-type layer side in a nip type photovoltaic element, the change pattern may be reversed in the layer thickness direction.

In FIG. 5C, the p-type layer side of the i-type layer and n-type layer
This is an example in which the fluorine content changes rapidly on the mold layer side.
In this case, the change pattern of the hydrogen content in the layer thickness direction is preferably that shown in FIG. This is particularly effective when the p / i interface and the n / i interface are composed of heterojunctions.

Although the effect of the i-type layer has been described above, changing the fluorine content in the layer thickness direction can be achieved by changing the RF doping layer, the MW doping layer, and the
This is applicable to the i-layer.

The photovoltaic element of the present invention is preferably one in which the content of hydrogen atoms in the i-type layer changes smoothly in the layer thickness direction.

By increasing the hydrogen content in the vicinity of the interface between the doping layer and the i-type layer, defect levels are compensated by hydrogen atoms, and dark current (during reverse bias) due to hopping conduction via the defect levels is reduced. However, the open voltage and the fill factor of the photovoltaic element can be improved.

Further, by containing more hydrogen atoms in the vicinity of the interface than in the inside, it is possible to reduce the internal stress due to a sudden change in the constituent elements specific to the vicinity of the interface.

As a result, it is possible to suppress a decrease in photoelectric conversion efficiency even when the device is subjected to vibration for a long time. Also i
Heterojunction (Si / SiG) between the mold layer and the doping layer
e, SiC / SiGe, etc.). Generally, it is considered that there are many interface states and internal stress at the interface of the hetero junction. In the photovoltaic device of the present invention, by including many hydrogen atoms near the interface of the heterojunction, the flexibility near the heterointerface can be increased, the internal stress can be reduced, and the interface state can be reduced.

As the change pattern of the hydrogen content in the thickness direction, the following example shown in FIG. 8 can be mentioned.

FIG. 8A shows an example in which the hydrogen content is rapidly changed on the p-type layer side, and the minimum value of the content is on the p-type layer side inside the bulk. When light is incident on the n-type photovoltaic element from the n-type layer side, the change pattern may be reversed in the layer thickness direction. It is particularly effective when the p / i interface is a heterojunction.

FIG. 8B shows an example in which the content is slowly changed from the p-type layer side to the n-type layer side, and the minimum value of the content is at the interface with the p-type layer. Especially when light is incident from the p-type layer side,
The packing density is increased on the p-type layer side of the i-type layer, which has the effect of suppressing light degradation. When light is incident on the n-type photovoltaic element from the n-type layer side, the change pattern may be reversed in the layer thickness direction. It is particularly effective when the n / i interface is a heterojunction.

In FIG. 8C, the p-type layer side of the i-type layer and n-type layer
This is an example in which the hydrogen content changes rapidly on the mold layer side. It is particularly effective when the p / i interface and the n / i interface are composed of heterojunctions. It is particularly effective when the photovoltaic element is placed in an environment where vibrations are large.

The distribution of the hydrogen content as described above can be applied not only to the i-type layer but also to each semiconductor layer.

In the present invention, light degradation can be suppressed by including both a valence electron controlling agent as a donor and a valence electron controlling agent as an acceptor in the i-type layer.

Although the details of the mechanism are unknown, in the case of the present invention, the valence electron controlling agent in the i-type layer is not 100% activated. As a result, even if a weak bond is broken by light irradiation to generate a dangling bond, it is considered that they react with an unactivated valence electron controlling agent to compensate the dangling bond.

In particular, it is considered that many weak bonds exist near the interface with the i-type layer. In the case of the present invention, a large amount of the valence electron controlling agent is distributed near the interface with the doping layer.
It is considered that the non-activated valence electron controlling agent compensates for the dangling bonds generated by breaking the weak bond.

Further, even when the light intensity applied to the photovoltaic element is weak, the probability of trapping of photoexcited electrons and holes is reduced because the defect level is compensated by the valence electron controlling agent. As described above, since a dark current at the time of reverse bias is small, a sufficient electromotive force can be generated.
As a result, excellent photoelectric conversion efficiency is exhibited even when the speed of light applied to the photovoltaic element is low.

In addition, the photovoltaic device of the present invention is one in which the photoelectric conversion efficiency does not easily decrease even if it is subjected to vibration for a long time. Generally, at the interface between the i-type layer and the doping layer, there are internal stresses at the interface because the constituent elements are very different.
It is considered that dangling bonds are formed by the vibration and the photoelectric conversion efficiency is reduced. However, since both the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor are contained in the i-type layer, even if dangling bonds are generated, the valence electron controlling agent is not activated. It is thought that it reacts and compensates for dangling bonds. Further, when the contents of the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor change smoothly in the layer thickness direction, and the content of the valence electron controlling agent increases near the interface. Especially effective. Further, a hetero junction (Si / SiGe, SiC / Si) is formed between the i-type layer and the doping layer.
Ge)) is particularly effective. Generally, it is considered that there are many interface states and internal stress at the interface of the hetero junction. In the photovoltaic device of the present invention, the interface state can be reduced by including a large amount of an inactive valence electron controlling agent near the interface of the heterojunction.

The following examples shown in FIG. 9 are examples of the pattern of change in the content of the valence electron controlling agent in the layer thickness direction. In FIG. 9, (B content) indicates the content of the valence electron controlling agent serving as the acceptor, and (P content) indicates the content of the valence electron controlling agent serving as the donor.

FIG. 9A shows that the content is maximized on the p-type layer side and the n-type layer side of the i-type layer, and minimized on the p-type layer side inside the bulk of the i-type layer. This is an example in which there is a sharp gradient of the content on the side. This is particularly effective when light is incident from the p-type layer side. When light is incident from the n-type layer side, the pattern may be reversed with respect to the layer thickness direction.

The present invention is particularly effective for a photovoltaic element having an i-type layer having a small band gap, such as the photovoltaic element of the present invention.

FIG. 9 (b) shows that the content is maximized on the p-type layer side of the i-type layer and minimized on the n-type layer side, so that there is a sharp gradient of the content on the p-type layer side. It is an example. This is particularly effective when light is incident from the p-type layer side. When light is incident from the n-type layer side, the pattern may be reversed with respect to the layer thickness direction. Further, the present invention is particularly effective for a photovoltaic element having an i-type layer having a small band gap.

FIG. 9 (c) shows that the content is maximized on the p-type layer side and the n-type layer side of the i-type layer, and there is a sharp gradient of the content on the p-type layer side and the n-type layer side. This is an example. Especially p
There is an effect when light is incident from the mold layer side. When light is incident from the n-type layer side, the pattern may be reversed with respect to the layer thickness direction. The change pattern as shown in FIG. 9C is particularly effective for a photovoltaic element having an i-type layer made of a material having a large band gap. That is, FIG.
In the case (c), when light is incident from the p-type layer side, carriers are also excited on the n-type layer side, so that it is desirable to increase the content of the valence electron controlling agent also in this region.

In the case of the i-type layer, the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor are preferably contained so as to compensate each other.

The distribution of the valence electron controlling agent can be applied to each semiconductor layer.

In the photovoltaic device of the present invention, the inclination of the tail state of the valence band of the i-type layer is an important factor that affects the characteristics of the photovoltaic device, and the tail at the minimum band gap is used. It is preferable that the inclination is smoothly continuous from the inclination of the state to the inclination of the tail state at the maximum band gap.

In the photovoltaic device according to the present invention, i formed by the RFPCVD method between the RF doping layer and the i-type layer.
By providing a mold layer (RF-i layer), the photoelectric conversion efficiency can be further improved. In addition, the open voltage and the fill factor of the photovoltaic element can be improved by including a larger amount of the valence electron controlling agent than inside the i-type layer.

For example, in FIG. 2A, FIG.
The RF-i layer is provided between the RF p-type layer and the i-type layer. Also, in FIG. 2B, an RF-i layer is provided between the RF n-type layer and the i-type layer in FIG. 1A. Further, in FIG. 2C, the RF n-type layer of FIG.
An RF-i layer is provided between the mold layers and between the RFp-type layer and the i-type layer.

The RF-i layer is preferably formed at a low power where a gas phase reaction does not easily occur, and the deposition rate is preferably 1 nm / sec or less. As a result, the packing density of the RF-i layer is increased, and when the RF-i layer is laminated with the i-type layer, the interface state of the i-type layer and the interface state of the doping layer are reduced. is there. In particular, the deposition rate of the i-type layer is 5 nm /
In the case where the deposition is performed at a deposition rate of sec or more, immediately after the glow discharge is started or stopped by the microwave, the interface state becomes extremely large because the vicinity of the surface of the i-type layer is not sufficiently relaxed. ing.

By forming the i-type layer on the RF-i layer, the i-type layer immediately after the start of the glow discharge by the microwave is affected by the underlayer, the packing density is increased, and the dangling bond is increased. It is considered that the layer has a small number of particles, and the surface level is reduced.

By forming the RF-i layer on the surface of the i-type layer, the surface level of the i-type layer can be reduced by annealing by diffusion of hydrogen atoms which occurs simultaneously with the formation of the semiconductor layer by RFPCVD. It is considered something.

Further, by including both a valence electron controlling agent as a donor and a valence electron controlling agent as an ataceptor in the RF-i layer, light degradation can be suppressed. Although the details of the mechanism are unknown, in the case of the present invention, R
Both the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor are contained in the Fi layer.
% Not activated. As a result, even if dangling bonds are generated by light irradiation, they are not activated. As a result, even if dangling bonds are generated by light irradiation, it is considered that they react with the inactive valence electron controlling agent to compensate for dangling bonds.

In addition, the photovoltaic device of the present invention is one in which the photoelectric conversion efficiency does not easily decrease even if it is subjected to vibration for a long period of time. Although the detailed mechanism is unknown, it is necessary to contain many hydrogen atoms near the interface where the ratio of constituent elements is very different, thereby alleviating the internal stress that is often present near the interface and preventing the occurrence of defect levels. It is thought that it is possible. Further, the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor, which are largely contained in the vicinity of the interface, are not 100% activated, and are not activated even if the bond is broken by vibration. It compensates for the dangling hands.

In the present invention, the i-type layer and / or the RF-i layer may contain tin (Sn), and the layer may be made of amorphous silicon tin (a-SiSn). S
The n atoms are covalently bonded to silicon (Si) atoms, so that an amorphous silicon-based semiconductor material having a small band gap can be obtained, and amorphous silicon germanium (a-SiG
The same band gap can be obtained with a smaller Sn content than the Ge atom content in e). Therefore, a-Si
It is considered that Sn can form a semiconductor with a smaller band gap by reducing disorder of the structure as compared with a-SiGe. Further, although Sn atoms have a larger covalent bond radius than Ge atoms, they are considered to be able to reduce structural distortion when alloyed with Si atoms because of their more metallic nature.

The band gap of a-SiSn suitable for the present invention is 1.30 to 1.65 eV, and the Sn content is preferably 0.1 to 30%. The hydrogen content is preferably in the range of 0.1 to 30%, and the ratio of hydrogen bonded to Sn is preferably 1 to 40%.

Further, the structure of a-SiSn suitable for the present invention contains microvoids and is distributed so that the relationship between the radius of the microvoids and the number of microvoids becomes a fractal relationship. is there. The deposition rate of microvoids is preferably 0.5 to 3%. The distribution of the microvoids as described above can suppress photodeterioration as compared with a-SiGe, although the reason is not clear yet.

Further, at least one of the i-type layer, the RF-i layer, the MW doping layer, and the RF doping layer may contain oxygen and / or nitrogen atoms. A very small amount (1%) of oxygen or / and nitrogen atoms is added to the i-type layer and the RF-i layer.
Below) can suppress the vibration deterioration of the photovoltaic element. The detailed mechanism is unknown, but by adding a small amount, the i-type layer, R
It is considered that the internal stress of the Fi layer can be reduced. Further, by containing the compound in the RF-i layer, back diffusion of electrons or holes can be prevented, and the photoelectric conversion efficiency of the photovoltaic element can be improved. Also, by adding a small amount (1% or less) to the MW doping layer and the RF doping layer, the stress inside the layer can be relaxed, and vibration degradation can be suppressed. In addition, the open voltage of the photovoltaic element can be improved by containing a large amount (1% or more). Preferably, the content of oxygen and / or nitrogen atoms changes in the layer thickness direction. As a preferable variation, the content is increased near one interface. A preferred variation in the i-type layer is one corresponding to the Ge or / and Sn atom content.

The photovoltaic element having a pin structure has been described above. However, a photovoltaic element having a pin structure such as a pinpin structure or a pinpinpin structure laminated, or ni
The present invention is also applicable to a photovoltaic element in which nip structures such as a pnip structure and a nipnipnip structure are stacked.

In the case of such a stacked photovoltaic element, n
RFn-type layer / MWn-type layer / RFp so that layers formed by the MWPCVD method are not continuous at the p-junction (pn-junction).
Type layer / MWp type layer / RFp type layer or RFn type layer /
MWn type layer / RFn type layer / RFp type layer / MWp type layer / R
It is desirable to form a junction having a structure such as an Fp type layer.

FIG. 6 is a schematic explanatory view of a manufacturing apparatus suitable for forming a semiconductor layer made of a non-single-crystal silicon-based semiconductor material of the photovoltaic device of the present invention. The manufacturing apparatus includes a deposition apparatus 400 and a source gas supply apparatus 2000. The deposition apparatus 400 includes a deposition chamber 401, a vacuum gauge 402,
03, substrate 404, heater 405, waveguide 406, conductance valve 407, auxiliary valve 408, leak valve 409, RF electrode 410, gas introduction tube 411, applicator 412, dielectric window 413, shutter 41
5, the source gas supply device 2000 includes mass flow controllers 2010 to 2019, and a valve 20.
20-2029, 2030-2039, pressure regulator 20
40-2049, raw material gas cylinders 2050-2059 and the like.

The fabrication of the photovoltaic device of the present invention is performed as follows.

First, the substrate 404 is brought into close contact with the heater 405 provided in the deposition chamber 401 shown in FIG.
Exhaust well below ^-4 Torr. For this exhaust, a turbo molecular pump or an oil diffusion pump is suitable.
After sufficiently exhausting the inside of the deposition chamber, a gas such as H ₂ , He, or Ar is introduced into the deposition chamber so that the pressure in the deposition chamber is substantially equal to that when the source gas for forming the semiconductor layer is flowed.
Switch on the heater 405 and set the substrate 100-500
When the temperature of the substrate is stabilized at a predetermined temperature, a predetermined amount of a source gas for forming a semiconductor layer is introduced from a gas cylinder into a deposition chamber via a mass flow controller. The supply amount of the source gas for forming the semiconductor layer introduced into the deposition chamber is appropriately determined by the volume of the deposition chamber.

When the semiconductor layer is formed by the MWPCVD method, the pressure during the formation of the semiconductor layer is a very important factor, and the optimum pressure in the deposition chamber is 0.5 to 50 mTorr.
Is preferred.

The MW power introduced into the deposition chamber is an important factor. The MW power is appropriately determined depending on the flow rate of the source gas introduced into the deposition chamber, but is preferably in the range of 0.005 to 1 W / cm ³ . The preferred frequency range of the MW power is 0.5 to
10 GHz. Particularly, a frequency around 2.45 GHz is suitable. Further, in order to form a semiconductor layer with reproducibility and to maintain a stable glow discharge for several hours to several tens of hours, the frequency stability of the MW power is very important. It is preferable that the fluctuation of the frequency be within a range of ± 2%. Further, the ripple of the microwave is preferably within ± 2%. The MW power generated from such a microwave power source (not shown) is
06, and transmitted from the applicator 412 to the dielectric window 4
13 into the deposition chamber. In such a state, the raw material gas is decomposed for a desired time to form a semiconductor layer having a desired thickness on the substrate. Thereafter, the introduction of MW power is stopped, the deposition chamber is evacuated, and the substrate is taken out of the deposition chamber after sufficiently purging with a gas such as H ₂ , He, or Ar. The dielectric window is made of a material that transmits microwaves well, such as alumina ceramics, quartz, and boron nitride.

In forming the i-type layer of the photovoltaic device of the present invention, RF power may be introduced into the deposition chamber together with MW power. In this case, the MW power to be introduced is desirably smaller than the MW power required to decompose the source gas introduced into the deposition chamber by 100%, and the RF power simultaneously introduced is desirably higher than the MW power. . A preferred range of the simultaneously introduced RF power is 0.01
２2 W / cm ³ . A preferable frequency range of the RF power includes 1 to 100 MHz. Especially 13.
56 MHz is optimal. The variation in RF frequency is ±
A smooth waveform within 2% is preferable. Although it is appropriately selected according to the area ratio between the area of the RF electrode for supplying RF power and the area of the ground, especially when the area of the RF electrode for supplying RF power is smaller than the area of the ground, It is better to ground the self-bias (DC component) on the power supply side. Self-bias (DC component) on the power supply side for RF power supply
Is not grounded, it is preferable that the area of the RF electrode for supplying RF power be larger than the area of the ground to which the plasma contacts.

In addition to the RF power, the RF electrode 41
A DC voltage may be applied to 0. As a polarity of the DC voltage, it is a preferable method to apply a voltage so that the RF becomes positive. The preferable range of the DC voltage is about 10 to 300V.

The details of the deposition mechanism of the preferred method for depositing the i-type layer described above are unknown, but are considered as follows.

MW required to decompose 100% of raw material gas
By applying a lower MW power to the source gas and a higher RF power to the source gas simultaneously with the MW power, it is considered that an active species suitable for forming a semiconductor layer can be selected. Further, it is considered that when the pressure in the deposition chamber when the source gas is decomposed is 50 mTorr or less, the mean free path of active species suitable for forming a high-quality semiconductor layer is sufficiently long, so that the gas phase reaction can be suppressed as much as possible. Can be And the pressure in the deposition chamber is 50mTo
It is considered that the RF power hardly affects the decomposition of the source gas in the state of rr or less, and controls the potential between the plasma and the substrate in the deposition chamber. That is, MWPCVD
Method, the potential difference between the plasma and the substrate is small, but R
By introducing the F power at the same time as the MW power, the potential difference between the plasma and the substrate (+ on the plasma side and − on the substrate side) can be increased. Since the plasma potential is positively higher than the substrate, active species decomposed by the MW power are deposited on the substrate, and at the same time, + ions accelerated by the plasma potential collide with the substrate and relax on the substrate surface. It is considered that the reaction is promoted and a high-quality semiconductor layer is obtained. This is particularly effective when the deposition rate is 5 nm / sec or more. Further, since RF has a higher frequency than DC, the difference between the plasma potential and the substrate potential is determined by the distribution of ionized ions and electrons. That is, the potential difference between the substrate and the plasma is determined by the synergistic effect between the ions and the electrons. Therefore, there is an effect that spark is less likely to occur in the deposition chamber. As a result, a stable glow discharge can be maintained for a long time of 10 hours or more.

In a normal RFPCVD method, a source gas containing fluorine (for example, SiF ₄ gas, GeF ₄ gas, CF
The decomposition energy of the _four gases, etc. is a source gas containing hydrogen (eg, SiH ₄ gas, GeH ₄ gas, CH ₄ gas, etc.).
About 10 times the decomposition energy of

Accordingly, a large amount of energy is applied to the glow discharge, which may adversely affect the underlying semiconductor layer. However, the MWPCVD method originally contains fluorine at a low power because the frequency of the applied electromagnetic wave is high. The source gas can be decomposed and is effective as a means for forming a fluorine-containing semiconductor layer. Further, since the radical of the fluorine-containing source gas has a relatively long life, MWP
In the CVD method, the mean free path can be further lengthened, so that the discharge space and the substrate surface can be easily separated without reducing the deposition rate. And MWP
When a fluorine-containing source gas is used in the CVD method, the stability of discharge is improved, and glow discharge can be maintained for a long time of 20 hours or more.

As a method of changing the content of germanium or / and tin contained in the semiconductor layer in the layer thickness direction, a source gas for containing germanium or / and tin in the semiconductor layer is temporally changed. I just need.

Another method for changing germanium and / or tin contained in the semiconductor layer in the thickness direction is as follows.
It is sufficient to increase the MW power to be introduced when it is desired to increase germanium and / or tin, and to decrease the MW power to be introduced when it is desired to reduce germanium and / or tin. Although the detailed mechanism is unknown, it is believed that increasing the MW power increases the active germanium or / and tin-containing radicals and includes more germanium or / and tin.

As a method for changing the valence electron controlling agent contained in the semiconductor layer in the layer thickness direction, a source gas for containing the valence electron controlling agent may be changed over time.

As a method of changing the hydrogen content contained in the semiconductor layer in the thickness direction, the MW power to be introduced where the hydrogen content is to be increased is increased, and the MW power to be introduced where the hydrogen content is to be reduced is increased. You can make it smaller. Although the detailed mechanism is still unknown,
It is considered that by increasing the MW power, radicals containing active hydrogen atoms increase, and more hydrogen atoms are contained.

As another method for changing the hydrogen content contained in the semiconductor layer in the layer thickness direction, the RF power applied to the RF electrode is increased where the hydrogen content is desired to be increased.
Where the hydrogen content is to be reduced, the RF power applied to the RF electrode may be reduced. Although the detailed mechanism is still unknown, increasing the RF power applied to the RF electrode raises the plasma potential and causes more hydrogen ions in the semiconductor layer to be more accelerated toward the substrate. It is considered that atoms are contained. Further, R
When the DC power is applied simultaneously with the F power, the DC voltage applied to the RF electrode may be increased by applying a large voltage with a positive polarity to increase the content of hydrogen atoms. What is necessary is just to apply a small voltage with a positive polarity to the DC voltage applied to the electrode. Although the detailed mechanism is still unknown, increasing the DC power applied to the RF electrode increases the plasma potential and increases the number of hydrogen atoms in the semiconductor layer because the hydrogen ions are accelerated toward the substrate. Is considered to be contained.

Still another method for changing the hydrogen content in the semiconductor layer in the thickness direction is to provide a halogen lamp or a xenon lamp in the deposition chamber in the semiconductor layer forming method of the present invention. These lamps are flashed during the formation of the semiconductor layer to temporarily raise the substrate temperature. At that time, if the hydrogen content is to be reduced, the number of flashes per unit time is increased by increasing the number of flashes per unit time, and the substrate temperature is temporarily increased.If the hydrogen content is desired to be increased, the number of flashes per unit time is reduced. The substrate temperature may be temporarily lowered. It is considered that by temporarily raising the substrate temperature, the desorption reaction of hydrogen from the surface of the semiconductor layer is activated.

As another method of changing the hydrogen content contained in the semiconductor layer in the thickness direction, a source gas containing fluorine and a source gas containing hydrogen are introduced at the time of forming the semiconductor layer, and the respective source gases are introduced. May be changed over time. Where a large amount of hydrogen is to be contained, a small amount of a fluorine-containing source gas may be flowed, and where a small amount of hydrogen is to be contained, a large amount of a fluorine-containing source gas may be supplied.

As a method of changing the fluorine content contained in the semiconductor layer in the layer thickness direction, a fluorine-containing gas may be changed at the time of forming the semiconductor layer. Where a large amount of fluorine is to be contained, a large amount of a fluorine-containing gas may be supplied, and where a small amount of fluorine is to be contained, a small amount of a fluorine-containing gas may be supplied.

As another method for changing the fluorine content in the layer thickness direction, a gas containing hydrogen may be changed over time during the formation of the semiconductor layer. Where a large amount of fluorine is to be contained, a small amount of gas containing hydrogen may be flowed, and where a small amount of fluorine is desired to be contained, a large amount of gas containing hydrogen may be supplied. It is considered that this is because fluorine bonded to the surface of the semiconductor layer reacts with a radical containing hydrogen to extract fluorine from the semiconductor layer and relatively reduce fluorine taken into the semiconductor layer.

When a semiconductor layer is deposited by the RFPCVD method, a capacitive coupling type RFPCVD method is suitable.

A doping layer and an RF-
When forming the i-layer, the substrate temperature in the deposition chamber is 100 to 5
00 ° C., pressure is 0.1 to 10 Torr, RF power is 0.1 Torr.
01 to 5.0 W / cm ² , and the deposition rate is 0.1 to ² nm /
sec is an optimal condition. R for a long time
To maintain the F glow discharge, the frequency of the RF power source fluctuates,
It is desirable that the ripple and the ripple be within 2%, respectively.

Further, US Pat. No. 4,400,409 discloses a roll-to-roll system.
There is disclosed a plasma CVD apparatus adopting the ll) method for continuously forming a semiconductor layer. It is desirable that the semiconductor layer of the photovoltaic element of the present invention be manufactured continuously using such an apparatus. According to this apparatus, a plurality of deposition chambers are provided, and a long and flexible substrate is arranged along a path through which the substrates sequentially pass through the deposition chamber, and the deposition chamber has a desired conductivity type. It is described that a photovoltaic element having a pin junction can be continuously manufactured by continuously transporting the substrate in the longitudinal direction while forming a semiconductor layer. Note that, in the specification, a gas gate is used to prevent a source gas for containing each valence electron controlling agent in a semiconductor layer from diffusing into another deposition chamber and being mixed into another semiconductor layer. Have been. Specifically, the deposition chambers are separated from each other by a slit-shaped separation passage, and a scavenging gas such as Ar, H ₂ , or He is caused to flow into each separation passage to prevent mutual diffusion of each source gas. ing.

In the above method for forming a semiconductor layer,
The following gases or gasifiable compounds are suitable as source gases.

As source gases for allowing silicon atoms to be contained in the semiconductor layer, SiH ₄ (H includes deuterium D), Six ₄ (X: halogen atom), Six ₂ H _4-n
(N is an integer), Si ₂ X _n H _{6-n and the} like. Collectively, it is referred to as “source gas (Si)”. In particular, SiH ₄ , Si
F ₄ , SiD ₄ and Si ₂ H ₆ are suitable.

In order to include fluorine atoms in the semiconductor layer
As the raw material gas of_Two, SiF _Four, Si_TwoF₆, G
eF_Four, CF_Four, C_TwoF₆, C_TwoClF_Five, CCl
F_Two, ClF_Three, CHF_Three, C_ThreeF₈, NF_Three, P
F_Five, BF_Three, SF_FourAnd the like. Collectively, "raw materials
Gas (F) ". Especially SiF_Four, GeF_Four, C
F_Four, PF _Five, BF_ThreeIs suitable.

As a source gas for containing carbon atoms in the semiconductor layer, CH ₄ (H includes deuterium D), C _n
H _{2n +} 2 (n is an _{integer), C n H 2n, CX} 4 (X is a halogen _{atom), C n X 2n + 2} , C 2 X 2n, C 2 H 2, C 6 H 6 and the like. It is collectively referred to as “source gas (C)”. Particularly, CH ₄ , CD ₄ and C ₂ H ₂ are suitable.

Source gases for containing germanium atoms in the semiconductor layer include GeH ₄ (H includes deuterium D), Ge _n H _{2 n + 2} , and GeX ₄ (X is a halogen atom).
And the like. It is collectively referred to as “source gas (Ge)”. In particular, GeH ₄ and GeD ₄ are suitable.

Source gases for containing tin atoms in the semiconductor layer include SnH ₄ (H includes deuterium D),
Sn _n H _{2n + 2} , SnX ₄ (X is a halogen atom), SnR
₄ (R: alkyl group), and a SnX _n R _4-n, and the like. It is collectively referred to as “source gas (Sn)”. Especially SnH
₄ , SnD ₄ and Sn (CH ₃ ) ₄ are suitable.

The valence electron controlling agent introduced to make the conductivity type of the semiconductor layer p-type is a group III atom (B, Al, Ga, In, Tl) of the periodic table, and the conductivity type is n. Examples of the valence electron controlling agent to be introduced into the mold include group V atoms (P, As, Sb, Bi) and group VI atoms (S, Se, Te) in the periodic table.

A group III atom of the periodic table is introduced into the semiconductor layer.
As the raw material gas for _TwoH₆, B_FourH_Ten,
B_FiveH₉, BF_Three, B (CH_Three)_Three, B (C
_TwoH_Five)_Three, BCl_Three, AlCl_Three, Al (C
H_Three)_Three, GaCl_Three, InCl_Three, TlCl_ThreeEtc.
I can do it. Collectively referred to as “source gas (III)”
I do. Especially B_TwoH ₆, B (CH_Three)_Three, B (C_TwoH_Five)
_Three, Al (CH_Three)_ThreeIs suitable.

As a source gas for introducing a group V atom of the periodic table into the semiconductor layer, PH ₃ , P ₂ H ₄ , PH ₄
I, PF ₃ , PF ₅ , PCl ₃ , PCl ₅ , PBr ₃ ,
PBr ₅ , PI ₃ , AsH ₃ , AsF ₃ , AsCl ₃ ,
AsBr ₃ , AsF ₅ , SbH ₃ , SbF ₃ , Sb
F ₅ , SbCl ₃ , SbCl ₅ , BiH ₃ , BiC
mention may be made of l _3, BiBr ₃ and the like.

The term “source gas (V)” is used as a generic term. Particularly, PH ₃ and AsH ₃ are suitable.

H ₂ S, SF ₄ , and S ₄ are used as source gases for introducing a Group VI atom of the periodic table into the semiconductor layer.
F ₆ , CS ₂ , H ₂ Se, SeF ₆ , TeH ₂ , TeF
₆ , (CH ₃ ) ₂ Te, (C ₂ H ₅ ) ₂ Te and the like. It is collectively referred to as “source gas (VI)”. Especially H ₂
S and H ₂ Se are suitable.

As a source gas for containing oxygen atoms in the semiconductor layer, O ₂ , CO ₂ , CO, NO, NO ₂ ,
N ₂ O, H ₂ O, CH ₃ CH ₂ OH, CH ₃ OH and the like can be mentioned. Collectively, it is referred to as “source gas (O)”. Particularly, O ₂ and NO are suitable.

For allowing oxygen atoms to be contained in the semiconductor layer,
The source gas is N_Two, NO, NO _Two, N_TwoO, NH_Three
And the like. Collectively referred to as “source gas (N)”.
Especially N_Two, NH_ThreeIs suitable.

These source gases are H ₂ , D ₂ , H
It may be appropriately diluted with a gas such as e or Ar and introduced into the deposition chamber.

The structure of the present invention will be described below in detail. The substrate may be formed of a single conductive material, or may be formed by forming a conductive layer on a support made of an insulating material or a conductive material. As a conductive material,
For example, NiCr, stainless steel, Al, Cr, Mo, A
Examples thereof include metals such as u, Nb, Ta, V, Ti, Pt, Pb, and Sn, and alloys thereof. In order to use these materials as a support, it is desirable to use a sheet or a roll formed by winding a long sheet around a cylindrical body.

As insulating materials, polyester, polyethylene, polycarbonate, cellulose acetate,
Examples include synthetic resins such as polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, and polyamide; glass, ceramics, and paper. In order to use these materials as a support, it is desirable to use a sheet or a roll formed by winding a long sheet around a cylindrical body. In these insulating supports, a conductive layer is formed on at least one surface thereof, and the semiconductor layer of the present invention is formed on the surface on which the conductive layer is formed.

For example, in the case of glass, NiC
r, Al, Ag, Cr, Mo, Ir, Nb, Ta, V,
Ti, Pt, Pb, In_TwoO_Three, ITO (In_TwoO_Three+
SnO _Two), ZnO and other materials or alloys thereof
An electric layer is formed and a synthetic resin sheet such as a polyester film
NiCr, Al, Ag, Pb, Z
n, Ni, Au, Cr, Mo, Ir, Nb, Ta, V,
Form conductive layers made of materials such as Tl and Pt or alloys thereof
NiCr, Al, Ag, C for stainless steel
r, Mo, Ir, Nb, Ta, V, Ti, Pt, Pb,
In_TwoO_Three, ITO (In_TwoO_Three+ SnO_Two), ZnO
A conductive layer made of such a material or an alloy thereof is formed. form
The deposition methods include vacuum deposition, sputtering,
It is formed by an ink-jet printing method or the like. The surface shape of the support is smooth
The peaks are irregular with a maximum height of 300 to 1000 nm
It is desirable.

The thickness of the substrate is appropriately determined so that a desired photovoltaic element can be formed, but when flexibility as the photovoltaic element is required, the function as a support is sufficiently exhibited. As thin as possible. However, the thickness is usually 10 μm or more from the viewpoints of production and handling of the support, mechanical strength and the like.

As a desirable substrate form in the photovoltaic element of the present invention, Ag, Al, Cu, A
The purpose is to form a conductive layer (light reflecting layer) made of a metal having a high reflectance in the near infrared to visible light such as 1Si. The light reflection layer is suitably formed by a vacuum evaporation method, a sputtering method, or the like. Suitable layer thicknesses of these metals as the light reflecting layer are 10 nm to 5000 nm. In order to texture the surface of the light reflection layer, the substrate temperature at the time of formation may be set to 200 ° C. or higher.

As a more desirable substrate form in the photovoltaic element of the present invention, ZnO, Sn
O ₂ , In ₂ O ₃ , ITO, TiO ₂ , CdO, Cd ₂
The purpose is to form a conductive layer (reflection increasing layer) made of SnO ₄ , Bi ₂ O ₃ , MoO ₃ , Na _x WO ₃ or the like. As a method for depositing the reflection increasing layer, a vacuum deposition method, a sputtering method, a CVD method, a play method, a spin-on method, a dipping method, and the like are mentioned as suitable methods. The optimum thickness of the reflection-enhancing layer varies depending on the refractive index of the material of the reflection-enhancing layer.
0 nm to 10 μm. In order to further texture the reflection-enhancing layer, it is preferable to raise the substrate temperature to 200 ° C. or higher when forming the reflection-enhancing layer. MW doping layer (MWp type layer, MWn type layer) This layer is an important layer which affects the characteristics of the photovoltaic device.

The MW doping layer is made of an amorphous silicon-based semiconductor material, a microcrystalline silicon-based semiconductor material, or a polycrystalline silicon-based semiconductor material. Amorphous (a
A-S is a silicon-based semiconductor material.
i, a-SiC, a-SiGe, a-SiGeC, a-
SiO, a-SiN, a-SiON, a-SiCON, and the like. Microcrystalline (abbreviated as μc-) silicon-based semiconductor materials include μc-Si, μc-SiC, and μc-
SiGe, μc-SiO, μc-SiGeC, μc-S
iN, μc-SiON, μc-SiOCN, and the like. Polycrystalline (abbreviated as poly-) silicon-based semiconductor materials include poly-Si, poly-SiC, p
poly-SiGe and the like.

In particular, as the MW doping layer on the light incident side, a crystalline semiconductor material with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable. Specifically, a-Si
C, a-SiO, a-SiN, a-SiON, a-Si
CON, μc-Si, μc-SiC, μc-SiO, μ
c-SiN, μc-SiON, μc-SiOCN, po
ly-Si and poly-SiC are suitable.

The introduction amount of the valence electron controlling agent introduced to make the conductivity type p-type or n-type is 1000 ppm to 10 ppm.
% Is mentioned as a preferable range, and it is desirable that the content is increased at at least one interface.

The contained hydrogen (H, D) and fluorine work to compensate for dangling bonds and improve doping efficiency. Hydrogen and fluorine content is 0.1-3
0 at% is mentioned as the optimum amount. In particular, when the MW doping layer is crystalline, the optimum amount is 0.01 to 10 at%. Further, those having a higher hydrogen content on the interface side are mentioned as a preferable distribution form, and the hydrogen content near the interface is preferably in a range of 1.1 to 3 times the content in the bulk as a preferable range. . Further, those having a low fluorine content on the interface side are mentioned as a preferable distribution form, and the range of 0.3 to 0.9 times in the bulk is mentioned as a preferable range.

The introduction amount of oxygen and nitrogen atoms is from 0.1 ppm to
20%, 0.1ppm-1% when contained in trace amount
Is a preferable range.

Regarding the electric characteristics, the activation energy is 0.1.
Those having 2 eV or less are preferable, and those having 0.1 eV or less are optimal. The specific resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness is 1 to
50 nm is preferred, and 3 to 30 nm is optimal.

In particular, when a crystalline semiconductor material having a small light absorption or an amorphous semiconductor layer having a wide band gap is formed, the source gas is diluted 2 to 100 times with a gas such as H ₂ , D ₂ , or He. However, it is preferable to introduce a relatively high MW power. RF doping layer (RF p-type layer, RF n-type layer) This layer is an important layer that affects the characteristics of the photovoltaic element.

The RF doping layer is made of an amorphous silicon-based semiconductor material, a microcrystalline silicon-based semiconductor material, or a polycrystalline silicon-based semiconductor material. Amorphous (a
A-S is a silicon-based semiconductor material.
i, a-SiC, a-SiGe, a-SiGeC, a-
SiO, a-SiN, a-SiON, a-SiCON, and the like. Microcrystalline (abbreviated as μc-) silicon-based semiconductor materials include μc-Si, μc-SiC, and μc-
SiGe, μc-SiO, μc-SiGeC, μc-S
iN, μc-SiON, μc-SiOCN and the like. Polycrystalline (abbreviated as poly-) silicon-based semiconductor materials include poly-Si, poly-SiC, and po.
ly-SiGe and the like.

In particular, as the RF doping layer on the light incident side, a crystalline semiconductor material with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable. Specifically, a-Si
C, a-SiO, a-SiN, a-SiON, a-Si
CON, μc-Si, μc-SiC, μc-SiO, μ
c-SiN, μc-SiON, μc-SiOCN, po
ly-Si and poly-SiC are suitable.

A preferable range of the introduction amount of the valence electron controlling agent for changing the conductivity type to p-type or n-type is 800 ppm to 8%, and it is preferable that the introduction amount is smaller than the introduction amount of the MW doping layer. . Further, it is desirable that the content is increased at at least one interface.

The contained hydrogen (H, D) and fluorine work to compensate for dangling bonds and improve doping efficiency. The content of hydrogen and fluorine is 0.1 to 2
5 at% is mentioned as the optimum amount. In particular, when the RF doping layer is crystalline, the optimum amount is 0.01 to 10 at%. Further, those having a higher hydrogen content on the interface side are mentioned as a preferable distribution form, and the hydrogen content near the interface is preferably in a range of 1.1 to 3 times the content in the bulk as a preferable range. . Further, those having a low fluorine content on the interface side are mentioned as a preferable distribution form, and the range of 0.3 to 0.9 times in the bulk is mentioned as a preferable range.

The introduction amount of oxygen and nitrogen atoms is from 0.1 ppm to
20%, 0.1ppm-1% when contained in trace amount
Is a preferable range.

Regarding the electric characteristics, the activation energy is 0.1.
Those having 2 eV or less are preferable, and those having 0.1 eV or less are optimal. The specific resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness is 1 to
50 nm is preferred, and 5 to 20 nm is optimal.

In particular, when forming a crystalline semiconductor material having little light absorption or an amorphous semiconductor layer having a wide band gap as described above, the source gas is diluted 2 to 100 times with a gas such as H ₂ , D ₂ or He. However, it is preferable to introduce a relatively high RF power. i-type layer In the photovoltaic device of the present invention, the i-type layer is the most important layer for generating and transporting photoexcited carriers.

As the i-type layer, a slightly p-type and slightly n-type layer can be used. The i-type layer contains silicon atoms and germanium or / and tin, and has a-SiGe, a-SiSn, a-
SiSnGe, a-SiGeC, a-SiSnC, a-
A photocrystalline semiconductor material such as SiSnGeC is used.

As the i-type layer of the photovoltaic device of the present invention,
It contains a hydrogen atom and the content of germanium and / or tin changes smoothly in the layer thickness direction. A preferable range of the germanium and / or tin content is 1 to 50%, and a preferable range of the band gap is 1.3 to 1.7 (eV).

The i-type layer preferably contains both a valence electron controlling agent as a donor and a valence electron controlling agent as an acceptor. More desirably, the content of the valence electron controlling agent changes smoothly in the layer thickness direction. It is desirable that the content is higher on the p-type layer side and / or the n-type layer side. Further, a trace amount of carbon atoms may be contained.

Hydrogen (H, D) and fluorine contained in the i-type layer work to compensate for dangling bonds of the i-type layer, and improve the product of carrier mobility and lifetime in the i-type layer. Things. Further, it has a function of compensating the interface state of the interface, and has an effect of improving the photovoltaic power, the photocurrent and the photoresponsiveness of the photovoltaic element. The optimal hydrogen and fluorine content of the i-type layer is 1 to 30 at%. In particular, those in which the hydrogen content is high on the interface side are mentioned as a preferable distribution form, and a range of 1.1 to 3 times in the bulk is mentioned as a preferable range, and 1.1 in the bulk is mentioned.
A range of up to 3 times is mentioned as a preferable range. Also,
Those having a low fluorine content on the interface side are preferred distribution forms, and 0.3 to 0.9 in the bulk.
A double range is mentioned as a preferred range.

The introduction amount of oxygen and nitrogen atoms is from 0.1 ppm to
1% is a suitable range.

The thickness of the i-type layer greatly depends on the structure of the photovoltaic element (for example, single cell, tandem cell, triple cell) and the band gap of the i-type layer.
1.0 μm is mentioned as the optimum layer thickness.

The i-type layer of the present invention has a deposition rate of 2.5 nm.
/ Sec, the tail state on the valence band side
It is small, and the tilt of the tail state is 60me
V or less and not determined by electron spin resonance (ESR).
The density of the joining hands is 10¹⁷/ Cm ^ThreeIt is as follows.

For the formation of the i-type layer, the MWPCVD method was used.
Preferably, as described above, RF in the MWPCVD method is used.
Power is simultaneously introduced, and more preferably, RF power and DC power are simultaneously introduced in the MWPCVD method as described above. RF-i layer In the photovoltaic device of the present invention, the RF-i layer is an important layer for transporting photoexcited carriers.

The RF-i layer is slightly p-type and slightly n-type.
A mold layer can also be used and is composed of an amorphous silicon-based semiconductor material or a microcrystalline silicon-based semiconductor material. As an amorphous silicon-based semiconductor material, for example, a-Si, a
-SiC, a-SiO, a-SiN, a-SiGe, a
—SiGeC, a-SiSn, a-SiSnC and the like. Examples of the microcrystalline silicon-based semiconductor material include μc-Si, μc-SiC, μc-SiGe, and μc-S
iSn, μc-SiO, μc-SiN, μc-SiO
N, μc-SiOCN and the like.

As shown in FIG. 2A, as the RF-i layer on the light incident side, a-Si, a-SiC, a-SiO, a-Si
By using a semiconductor material such as N, the open-circuit voltage of the photovoltaic element can be improved.

As shown in FIG. 2B, a-Si, a-SiGe, and a-Si RF-i layers on the side opposite to the light incident side are used.
By using a semiconductor material such as Sn, a-SiGeC, or a-SiSnC, the short-circuit current of the photovoltaic element can be improved.

Hydrogen (H, D) and fluorine contained in the RF-i layer work to compensate for dangling bonds of the RF-i layer, and the product of the mobility and lifetime of carriers in the RF-i layer. Is to improve. In addition, it has the effect of compensating for the interface state of the interface and improving the photovoltaic power, photocurrent and photoresponsiveness of the photovoltaic element. The optimum hydrogen and fluorine content of the RF-i layer is 1 to 30 at%. In particular, those having a large hydrogen content on the interface side are mentioned as a preferable distribution form, and a range of 1.1 to 3 times the content in the bulk is mentioned as a preferable range. Further, those having a low fluorine content on the interface side are mentioned as a preferable distribution form, and a range of 0.3 to 0.9 times the content in the bulk is mentioned as a preferable range.

In another desirable mode, a valence electron controlling agent (Group V atom and / or Group VI atom) as a donor and a valence electron controlling agent (Group III atom in the Periodic Table) serving as an acceptor are used. Both are contained. Further, it is preferable that a valence electron controlling agent serving as a donor and a valence electron controlling agent serving as an acceptor are contained so as to compensate each other.

Periodic Table III introduced into the RF-i layer
The preferable introduction amount of the group A atom, the group V atom and the group VI atom is 600 ppm or less, respectively.

The introduction amount of oxygen and nitrogen atoms is from 0.1 ppm to
20%, 0.1ppm-1% when contained in trace amount
Is a preferable range.

The optimum layer thickness of the RF-i layer is 0.5 to 30 nm or less. The RF-i layer has less tail state on the valence band side, and has an inclination of 5%.
The density is 5 meV or less, and the density of dangling bonds by electron spin resonance (ESR) is 10 ¹⁷ / cm ³ or less. Transparent Electrode The transparent electrode is made of a material suitable for indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and ITO (In ₂ O ₃ + SnO ₂ ).

For deposition of the transparent electrode, a sputtering method and a vacuum evaporation method are the most suitable deposition methods.

When depositing by sputtering, a target such as a metal target or an oxide target is used in appropriate combination.

When depositing by sputtering, the substrate temperature is an important factor, and a preferable range is from 20 ° C. to 600 ° C. Also, when depositing a transparent electrode by a sputtering method, as a sputtering gas,
An inert gas such as an Ar gas may be used. It is preferable to add oxygen gas (O ₂ ) to the inert gas as needed. Particularly when a metal is targeted, oxygen gas (O ₂ ) is essential. Further, when sputtering the target with the inert gas or the like, the pressure in the discharge space is preferably in the range of 0.1 to 50 mTorr for effective sputtering. The deposition rate of the transparent electrode depends on the pressure in the discharge space and the discharge power.
The range is from 01 to 10 nm / sec.

As a deposition source suitable for depositing a transparent electrode in the vacuum deposition method, there are metal tin, metal indium, and indium-tin alloy. The substrate temperature when depositing the transparent electrode is preferably in the range of 25 ° C. to 600 ° C. Further, it is necessary to introduce oxygen gas (O ₂ ) and to deposit at a pressure in the range of 5 × 10 ⁻⁵ Torr to 9 × 10 ⁻⁴ Torr. By introducing oxygen in this range, the metal vaporized from the evaporation source reacts with oxygen in the gas phase to deposit a good transparent electrode. The preferable range of the deposition rate of the transparent electrode under the above conditions is 0.01 to 10 nm / sec. Deposition rate is 0.0
If it is less than 1 nm / sec, the productivity is reduced and 10 nm / sec.
When the time is longer than sec, the film becomes coarse, and the transmittance, the conductivity and the adhesion are reduced.

It is preferable that the thickness of the transparent electrode is deposited so as to satisfy the conditions of the antireflection film. As a specific layer thickness of the transparent electrode, a preferable range is 50 to 500 nm. More light is incident on the i-type layer, which is a collecting electrode photovoltaic element,
In order to efficiently collect the generated carriers on the electrode, the shape (the shape viewed from the light incident direction) and the material of the current collecting electrode are important. Usually, the shape of the collecting electrode is a comb shape, and the line width and the number of lines are determined by the shape and size of the photovoltaic element viewed from the light incident direction, the material of the collecting electrode, and the like. . The line width is usually about 0.1 mm to 5 mm. The material of the collecting electrode is Fe, Cr, Ni, Au, Ti, P
d, Ag, Al, Cu, AlSi, C (graphite)
And the like, usually Ag, Cu, Al,
Metals such as Cr and C or alloys thereof are suitable.

The layer structure of the current collecting electrode may be a single layer or a plurality of layers.

These metals are desirably formed by a vacuum deposition method, a sputtering method, a plating method, a printing method, or the like.

In the case of forming by a vacuum deposition method, a mask having a shape of a collecting electrode is closely attached to the transparent electrode, and a desired metal deposition source is evaporated by an electron beam or resistance heating in a vacuum.
A collector electrode having a desired shape is formed on the transparent electrode.

In the case of forming by a sputtering method, a mask having a shape of a collecting electrode is brought into close contact with the transparent electrode, an Ar gas is introduced into a vacuum, DC is applied to a desired metal sputtering target, and a glow discharge is generated. By letting
A metal is sputtered to form a current collecting electrode having a desired shape on the transparent electrode.

In the case of forming by a printing method, an Ag paste, an Al paste, and a carbon paste are printed by a screen printing machine.

The thickness of these metals is 10 nm to
A suitable layer thickness is 0.5 mm.

The power generation system of the present invention will be described below.

A power generation system according to the present invention includes a photovoltaic element according to the present invention, and monitors the voltage and / or current of the photovoltaic element to transfer power from the photovoltaic element to a storage battery and / or an external load. The control system includes a control system that controls supply, and a storage battery that stores power from the photovoltaic element and / or supplies power to an external load.

FIG. 13 shows an example of a power supply system according to the present invention, which is a basic circuit for charging and supplying power using a photovoltaic element. In this circuit, a photovoltaic element of the present invention is used as a solar cell module, and a backflow prevention diode (D
C), a voltage control circuit (constant voltage circuit) for monitoring the voltage and controlling the voltage, a storage battery, a load, and the like.

To make a module, an adhesive sheet and a nylon sheet are placed on a flat plate, and the photovoltaic elements of the present invention are arranged thereon, serialized and parallelized, and further adhered thereon. It is good to carry out vacuum lamination with an agent sheet and a fluororesin sheet.

As the backflow prevention diode, a silicon diode, a Schottky diode or the like is suitable. Examples of the storage battery include a nickel cadmium battery, a rechargeable silver oxide battery, a lead storage battery, and a flywheel energy storage unit.

The voltage control circuit is substantially equal to the output of the solar cell until the battery is fully charged, but when the battery is fully charged, the charging current is stopped by the charge control IC.

The power generation system using such a photovoltaic element can be used as a power source for an automobile battery charging system, a ship battery charging system, a streetlight lighting system, an exhaust system, and the like.

As described above, the power supply system using the photovoltaic element of the present invention as a solar cell can be used stably for a long period of time, and even when the irradiation light applied to the solar cell fluctuates, Since it functions sufficiently as an element, it exhibits excellent stability.

[0203]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the photovoltaic element of the present invention will be described in detail by manufacturing a solar cell and a photodiode made of a non-single-crystal silicon-based semiconductor material, but the present invention is not limited thereto.

Example 1 The solar cell shown in FIG. 1B was manufactured using the manufacturing apparatus shown in FIG. n-type layer is RFPCV
Formed by Method D.

First, a substrate was manufactured. 0.5m thick
A 50 × 50 mm ² stainless steel substrate was subjected to ultrasonic cleaning with acetone and isopropanol and dried with warm air. Using a sputtering method, a 0.3 μm-thick Ag light reflecting layer and a 1.0 μm-thick ZnO reflection increasing layer at 350 ° C. were formed on the stainless steel substrate surface at room temperature at room temperature, and the fabrication of the substrate was completed. Was.

Next, a semiconductor layer was formed on the reflection-enhancing layer by the manufacturing apparatus shown in FIG. 6, which can perform both the MWPCVD method and the RFPCVD method, which includes the source gas supply device 2000 and the deposition device 400.

In the gas cylinders 2050 to 2059 in the figure, a raw material gas for producing the photovoltaic element of the present invention is sealed, and reference numeral 2050 denotes a SiH ₄ gas cylinder, 2050.
51 is a SiF ₄ gas cylinder, 2052 is a CH ₄ gas cylinder, 2053 is a GeH ₄ gas cylinder, 2054 is GeF
₄ gas cylinder, 2055 (hereinafter abbreviated as "PH ₃ / H _2") PH ₃ gas diluted to 100ppm with H ₂ gas bomb 2056 PF ₅ gas diluted to 100ppm with H ₂ gas (hereinafter "PF ₅ / H ₂ "and abbreviated)
Bomb, 2057 is B ₂ H ₆ gas diluted to 100 ppm with H ₂ gas (hereinafter abbreviated as “B ₂ H ₆ / H ₂ ”)
2058 is a BF ₃ gas cylinder (hereinafter abbreviated as “BF ₃ / H ₂ ”) diluted to 100 ppm with H ₂ gas, and 2059 is an H ₂ gas cylinder, all of which are purified to ultra-high purity. . In advance, gas cylinders 2050-2
059, each gas is supplied to the valve 203.
Introduced into the gas piping from 0 to 2039, pressure regulator 2
Each gas pressure was adjusted to ² Kg / cm ^{2 according} to 040 to 2049.

Next, the back surface of the substrate 404 on which the reflection layer and the reflection enhancement layer are formed is brought into close contact with the heater 405, the leak valve 409 of the deposition chamber 401 is closed, the conductance valve 407 is fully opened, and a vacuum (not shown) The inside of the deposition chamber 401 is evacuated by an exhaust pump, and the pressure in the deposition chamber is reduced to about 1
When the pressure reaches × 10 ^-5 Torr, the valve 2020
2029, the auxiliary valve 408 is opened, the inside of the gas pipe is evacuated, and when the pressure reaches about 1 × 10 ⁻⁵ Torr, the valves 2020 to 2029 are closed and 2030 to 203
9 was gradually opened, and each gas was introduced into the mass flow controllers 2010-2019.

After preparation for film formation is completed as described above, an RF n-type layer made of μc-Si
i-type layer made of a-SiGe, RF made of a-SiC
A p-type layer and a MWp-type layer made of a-SiC were sequentially formed.

To form an RF n-type layer made of μc-Si, the valve 2029 was gradually opened, H ₂ gas was introduced into the deposition chamber 401, and the flow rate was adjusted to 300 sccm by a mass flow controller. The pressure inside the deposition chamber was adjusted with a conductance valve so as to be 1.0 Torr. The heater 405 is set so that the temperature of the substrate 404 becomes 350 ° C., and when the substrate temperature becomes stable,
Further, the valves 2020 and 2025 are gradually opened to
H ₄ gas and PH ₃ / H ₂ gas flowed into the deposition chamber 401. At this time, the flow rate of the SiH ₄ gas was ₂ sccm, the flow rate of the H ₂ gas was 100 sccm, and the flow rate of the PH ₃ / H ₂ gas was 20 sccm.
0 sccm and the pressure in the deposition chamber were adjusted to 1.0 Torr. The power of the RF power source was set to 0.02 W / cm ³ , RF power was introduced to the RF electrode 410, glow discharge was generated, the shutter was opened, the formation of an RF n-type layer on the substrate was started, and the layer thickness was 20 nm. When the RF n-type layer was formed, the shutter was closed, the RF power was turned off, glow discharge was stopped, and the formation of the RF n-type layer was completed. Valve 202
0,2025 is closed and SiH ₄ gas and P
H ₃ / H ₂ stop the flow of gas, 5 minutes, into the deposition chamber H ₂
After the gas continued to flow, the outflow valve 2029 was closed, and the deposition chamber and the gas pipe were evacuated.

Next, in order to form an i-type layer made of a-SiGe, the valve 2029 is gradually opened, H ₂ gas is introduced at 300 sccm, the pressure becomes 0.01 Torr, and the substrate temperature becomes 350 ° C. The heater was set as follows. When the substrate temperature is stabilized, valves 2020 and 20
21 and 2023 are gradually opened, and SiH ₄ gas, SiF
_Four gases and GeH ₄ gas were introduced. At this time, the flow rate of the SiH ₄ gas is 130 sccm, and the flow rate of the SiF ₄ gas is 10 sccm.
cm, a GeH ₄ gas flow rate of 10 sccm, an H ₂ gas flow rate of 300 sccm, and a pressure of 0.01 Torr. Next, the power of the RF power supply was set to 0.32 W / cm.
Set to ³ and applied to the RF electrode. Then, M (not shown)
The power of the W power source is set to 0.20 W / cm ³ , and MW power is introduced into the deposition chamber through the dielectric window 413 to generate a glow discharge, open a shutter, and form an i-type layer on the RF n-type layer. Started. During the formation of the i-type layer, the computer connected to the mass flow controllers 2010 and 2013 was used to change the S pattern according to the change pattern shown in FIG.
The flow rate of the iH ₄ gas and the flow rate of the GeH ₄ gas were changed to change the layer thickness 2
When the i-type layer of 00 nm was formed, the shutter was closed, the MW power supply and the RF power supply were turned off to stop the discharge, and the formation of the i-type layer was completed.

The valves 2020, 2021, and 2023 are closed to stop the flow of the SiH ₄ gas, the SiF ₄ gas, and the GeH ₄ gas, and the H ₂ gas is kept flowing for 5 minutes. The piping was evacuated.

In order to form an RFp type layer made of a-SiC, the valve 2029 is gradually opened, and H ₂ gas is supplied.
The heater was set so that 0 sccm was introduced, the pressure was 1.0 Torr, and the substrate temperature was 200 ° C. Since the substrate temperature was stable, valves 2020, 2022 and
2027 is gradually opened, and SiH ₄ gas, CH ₄ gas,
B ₂ H ₆ / H ₂ gas was caused to flow into the deposition chamber 401. At this time, the flow rate of the SiH ₄ gas was 5 sccm, the flow rate of the CH ₄ gas was 1 sccm, the flow rate of the H ₂ gas was 100 sccm, and B ₂ H
₆ / H ₂ gas flow rate 200 sccm, pressure 1.0 To
rr. Reduce the power of the RF power source to 0.06
W / cm ³ , RF power was introduced to the RF electrode to generate glow discharge, the shutter was opened, and R was applied on the i-type layer.
The formation of the Fp-type layer was started. When the RFp-type layer having a thickness of 10 nm was formed, the shutter was closed, the RF power was turned off, the glow discharge was stopped, and the formation of the RFp-type layer was completed. The valves 2020, 2022, and 2027 are closed, and the deposition chamber 4
01, SiH ₄ gas, CH ₄ gas, B ₂ H ₆ / H ₂
After stopping the inflow of the gas and continuing the flow of the H ₂ gas for 5 minutes, the outflow valve 2029 was closed, and the deposition chamber and the gas pipe were evacuated.

Forming MWp type layer made of a-SiC
Gradually open the valve 2029_Two50 gas
0 sccm, and the pressure in the deposition chamber is 0.02 Torr.
r, the substrate temperature was set to 200 ° C. Substrate temperature
When the temperature is stabilized, valves 2020 and 202 are further added.
2,2027 is gradually opened and SiH_FourGas, CH_FourMoth
S, B_TwoH₆/ H_TwoGas was allowed to flow. At this time, SiH
_FourGas flow rate 10 sccm, CH_FourGas flow rate is 2scc
m, H_TwoGas flow rate 100sccm, B_TwoH₆/ H _TwoMoth
The flow rate is 500 sccm and the pressure is 0.02 Torr.
Was adjusted to Then, the power of the MW power (not shown) is
0.40W / cm^ThreeMW power through the dielectric window
Force to generate glow discharge and open the shutter.
Then, the formation of the MWp type layer on the RFp type layer was started.

When the WMp-type layer having a thickness of 10 nm was formed, the shutter was closed, the MW power was turned off to stop glow discharge, and the formation of the MWp-type layer was completed. Valve 2020,
2022, 2027 are closed to stop the flow of the SiH ₄ gas, CH ₄ gas, and B ₂ H ₆ / H ₂ gas, and the H ₂ gas is kept flowing for 5 minutes. Then, the valve 2029 is closed, and the deposition chamber and the gas piping are closed. The inside was evacuated, the auxiliary valve 408 was closed, the leak valve 409 was opened, and the deposition chamber was leaked.

Next, on the MWp type layer, as a transparent electrode,
ITO having a layer thickness of 70 nm was vacuum deposited by a vacuum deposition method.

Next, a mask having a comb-shaped hole was placed on the transparent electrode, and Cr (40 nm) / Ag (1000 nm) / C
A comb-shaped current collecting electrode made of r (40 nm) was vacuum deposited by a vacuum deposition method.

Thus, the production of the solar cell has been completed. This solar cell is referred to as (SC Ex. 1), and Table 1 shows conditions for forming the RF n-type layer, the i-type layer, the RFp-type layer, and the MWp-type layer.

(Comparative Example 1-1) When forming an i-type layer,
Example 1 except that the iH ₄ gas flow rate was 120 sccm and the GeF ₄ gas flow rate was 30 sccm, which was constant over time.
Under the same conditions as above, a solar cell (SC ratio 1-1) was produced.

(Comparative Example 1-2) No RFp type layer was formed,
A solar cell (SC ratio 1-2) was manufactured under the same conditions as in Example 1 except that the layer thickness of the MWp type layer was set to 20 nm.

The solar cells (SC Ex. 1) and (SC ratio 1−
1) and (SC ratio 1-2) were prepared in six pieces each, and the initial photoelectric conversion efficiency (photoelectromotive power / incident optical power), vibration degradation,
We measured vibration deterioration in high temperature environment, vibration deterioration in high humidity environment, light deterioration, light deterioration in high temperature environment, and light deterioration in high humidity environment.

The measurement of the initial photoelectric conversion efficiency can be obtained by placing the produced solar cell under irradiation with AM-1.5 (100 mW / cm ² ) light and measuring the VI characteristics. As a result of the measurement, (SC ratio 1−
The initial photoelectric conversion efficiencies of 1) and (SC ratio 1-2) were as follows.

(SC ratio 1-1) 0.88 times (SC ratio 1-2) 0.87 times The vibration degradation was measured by measuring the initial photoelectric conversion efficiency of a solar cell in advance at a humidity of 50% and a temperature of 50%. Installed in a dark place at 25 ° C, vibration with an oscillation frequency of 60 Hz and amplitude of 0.1 mm
AM1.5 (100 mW / cm ² ) after adding for 0 hours
The measurement was performed based on the rate of decrease in photoelectric conversion efficiency under irradiation (photoelectric conversion efficiency after vibration degradation test / initial photoelectric conversion efficiency).

The photodegradation was measured by placing a solar cell, whose initial photoelectric conversion efficiency was measured in advance, in an environment of a humidity of 50% and a temperature of 25 ° C., and applying AM-1.5 (100 mW / cm ² ) light. After irradiation for 500 hours, AM1.5 (100 mW / cm
² ) The reduction rate of the photoelectric conversion efficiency under irradiation (photoelectric conversion efficiency after light degradation test / initial photoelectric conversion efficiency) was used. As a result of the measurement, (SC ratio 1-1) with respect to (SC actual 1),
(SC ratio 1-2) Decrease in photoelectric conversion efficiency after photodegradation,
The rate of decrease in photoelectric conversion efficiency after vibration degradation was as follows.

Vibration deterioration Light deterioration (SC ratio 1-1) 0.87 times 0.88 times (SC ratio 1-2) 0.89 times 0.87 times Measurement of vibration deterioration in a high temperature environment and light deterioration A measurement was made. A solar cell whose initial photoelectric conversion efficiency was measured in advance was placed in a dark place at a humidity of 50% and a temperature of 80 ° C., and the vibration deterioration was measured. Further, the solar cell whose initial photoelectric conversion efficiency was measured in advance was set in an environment of a humidity of 50% and a temperature of 80 ° C., and the photodegradation was measured. As a result of the measurement, (SC
(Comparative example 1), (SC ratio 1-1), (SC ratio 1-2)
The rate of decrease in photoelectric conversion efficiency after vibration degradation and the rate of decrease in photoelectric conversion efficiency after light degradation were as follows.

Vibration deterioration Light deterioration (SC ratio 1-1) 0.88 times 0.87 times (SC ratio 1-2) 0.89 times 0.87 times (SC actual 1), (SC ratio 1-1) ), No delamination was observed, and it was found that (SC ratio 1-2) partially delaminated.

Measurement of vibration deterioration and light deterioration in a high humidity environment were performed. The solar cell whose initial photoelectric conversion efficiency was measured in advance was set in a dark place at a humidity of 90% and a temperature of 25 ° C., and the vibration deterioration was measured. Further, the solar cell whose initial photoelectric conversion efficiency has been measured in advance is subjected to a humidity of 90% and a temperature of 2%.
It was set in an environment of 5 ° C., and the photo degradation was measured. As a result of the measurement, (SC ratio 1-1), (SC ratio 1)
Ratio 1-2), the rate of decrease in photoelectric conversion efficiency after vibration degradation and the rate of decrease in photoelectric conversion efficiency after light degradation were as follows.

Vibration degradation Light degradation (SC ratio 1-1) 0.89 times 0.88 times (SC ratio 1-2) 0.88 times 0.87 times (SC actual 1), (SC ratio 1-1) ), No delamination was observed, and it was found that (SC ratio 1-2) partially delaminated.

The measurement of vibration deterioration and the measurement of light deterioration in a high temperature and high humidity environment were performed. The solar cell whose initial photoelectric conversion efficiency was measured in advance was set in a dark place with a humidity of 90% and a temperature of 70 ° C., and the vibration deterioration was measured. Further, the solar cell whose initial photoelectric conversion efficiency has been measured in advance is subjected to a humidity of 90%.
%, The temperature was set at 70 ° C., and the photodegradation was measured.

As a result of the measurement, (S
The reduction rate of the photoelectric conversion efficiency after vibration deterioration of (C ratio 1-1) and (SC ratio 1-2) and the reduction rate of the photoelectric conversion efficiency after light deterioration were as follows.

Vibration deterioration Light deterioration (SC ratio 1-1) 0.88 times 0.87 times (SC ratio 1-2) 0.89 times 0.89 times (SC actual 1), (SC ratio 1-1) ), No delamination was observed, and it was found that (SC ratio 1-2) partially delaminated.

Next, using a glass substrate and a stainless steel substrate,
A sample in which the flow rate of SiH _{4 and the} flow rate of GeH ₄ were constant over time was produced. An i-type layer was produced under the same conditions as in Example 1 except that the flow rate was constant and the layer thickness was 1 μm, and used as a sample for band gap measurement and analysis. further,
Several samples with different flow rates were made.
The band gap (Eg) of the glass substrate sample was determined using a spectrophotometer, and the Ge content of the stainless substrate sample was analyzed using an Auger electron spectrometer (AES). Using both results, G in the i-type layer
The relationship between the e content and the band gap was determined. Further, when the Ge content in the layer thickness direction of the solar cell (SC Ex. 1) and (SC ratio 1-2) was determined using an Auger electron spectrometer, the result was as shown in FIG. 7D. Further, a change in the band gap was determined using the above relationship between the Ge content and the band gap, and the result was as shown in FIG. 7D. Similarly, when the Ge content of (SC ratio 1-1) was obtained, it was found that there was no change in the Ge content in the layer thickness direction, the Ge content was constant, and the band gap was 1.51 (eV). As described above, the Ge content in the layer thickness direction,
And the change in band gap was found to depend on the GeH ₄ gas flow introduced.

Further, a secondary ion mass spectrometer (SIM)
When the change in the fluorine content in the i-type layer in the thickness direction was examined using S), it was found that all three had a constant content in the thickness direction.

As described above, the solar cell (SC actual 1) of this embodiment is different from the conventional solar cell (SC ratio 1-1) and (SC ratio 1).
It was found that it had more excellent characteristics than -2).

(Example 1-1) A solar cell was manufactured in which the position where the Ge content of the i-type layer became maximum was closer to the p-type layer side than the center position of the i-type layer. When forming the i-type layer, S
FIG. 7 shows the time change of the iH ₄ gas flow rate and the GeH ₄ gas flow rate.
A solar cell (SC Ex. 1-1) was manufactured in the same manner as in Example 1 except for (a). Changes in the Ge content and the band gap in the layer thickness direction in the same manner as in Example 1 were found, and the results were as shown in FIG. 7C. The same measurement as in Example 1 was performed, and it was found that the solar cell (SC Ex 1-1) of the present example had more excellent characteristics than (SC Ex 1).

Example 2 A solar cell (SC Ex. 2) was manufactured in which the content of Ge atoms in the i-type layer was changed as shown in FIG. 3B. Solar cell (SC Ex. 2) under the same conditions as in Example 1 except that the GeH ₄ gas flow rate was monotonically increased with time, and the SiH ₄ gas flow rate was monotonically decreased with time.
Was prepared. When the change in the band gap in the layer thickness direction was determined in the same manner as in Example 1, it was found that the results were as shown in FIG. 4B. When the same measurement as in Example 1 was performed, the solar cell (SC Ex. 2) of the present example exhibited more excellent characteristics than the conventional solar cells (SC ratio 1-1) and (SC ratio 1-2). It was found to have.

Example 3 A photodiode having the layer configuration shown in FIG. 1C was manufactured.

First, a substrate was manufactured. 0.5m thick
m, a glass substrate of 20 × 20 mm ² is ultrasonically washed with acetone and isopropanol, dried with warm air, and a 0.1 μm-thick A1 light reflecting layer is formed on the surface of the glass substrate at room temperature by a vacuum evaporation method. Finished making the substrate.

In the same manner as in Example 1-1, the MW was
p-type layer (μc-SiC), RF n-type layer (a-SiC),
i-type layer (a-SiGe), RFp-type layer (μc-SiC)
Were sequentially formed. Table 2 shows the conditions for forming the semiconductor layer.

Next, the same transparent electrode and current collecting electrode as in Example 1 were formed on the RFp type layer.

(Comparative Example 3-1) When forming an i-type layer,
The photodiode (PD ratio 3) was used under the same conditions as in Example 3 except that the iH ₄ gas flow rate was 120 sccm and the GeF ₄ gas flow rate was 30 sccm, which was constant over time, and the Ge content and the band gap in the layer thickness direction were constant. -1) was prepared.

(Comparative Example 3-2) No RF n-type layer was formed.
A photodiode (PD ratio 3-2) was manufactured under the same conditions as in Example 3 except that the layer thickness of the MWn-type layer was set to 40 nm.

First, the on / off ratio (photocurrent / dark current measurement frequency of 10 kHz when AM1.5 light was irradiated) of the fabricated photodiode was measured. This will be referred to as an initial on / off ratio. Next, the same measurement as in Example 1 was performed for the on / off ratio, and the photodiode of this example (PD actual 3) was a conventional photodiode (PD ratio 3).
-1) and (PD ratio 3-2).

Example 4 A solar cell shown in FIG. 1B having a nip type structure in which the order of lamination of an n-type layer and a p-type layer was reversed. The H ₂ gas cylinder was replaced with a He gas cylinder, and an RFp type layer (μc-S
i), i-type layer (a-SiGe), RFn-type layer (a-Si
C), a MWn type layer (a-SiC) was formed. In the formation of the i-type layer, SiH ₄ gas flow rate as shown in FIG. 7 (b), G
The flow rate of the eH ₄ gas was changed with time so that the position where the Ge content became maximum was closer to the p-type layer than the center position of the i-type layer. Table 3 shows the conditions for forming the semiconductor layer. A solar cell (SC Ex. 4) was manufactured under the same conditions as in Example 1 except for the semiconductor layer and the substrate.

(Comparative Example 4-1) When forming an i-type layer,
A solar cell (SC ratio 4-1) was manufactured under the same conditions as in Example 4 except that the iH ₄ gas flow rate was 120 sccm, the GeH ₄ gas flow rate was 30 sccm, and the time was constant.

(Comparative Example 4-2) No RF n-type layer was formed.
A solar cell (SC ratio 4-2) was manufactured under the same conditions as in Example 4 except that the layer thickness of the MWn-type layer was set to 20 nm.

When the same measurement as in Example 1 was performed, the solar cell of this example (SC Ex. 4) was a conventional solar cell (SC
It was found that the composition had more excellent characteristics than (Comparative 4-1) and (SC Comp. 4-2).

(Example 5) A solar cell having a minimum fluorine content near the interface of the i-type layer was manufactured. When forming the i-type layer, GeF ₄ gas was introduced instead of GeH ₄ gas, and the flow rate of SiH ₄ gas and the flow rate of GeF ₄ gas were changed over time as in Example 1 to reduce the fluorine content as shown in FIG. As shown in FIG. 7C, a solar cell having a Ge content varying as shown in FIG. 7C was obtained. Except for this, it was manufactured under the same conditions as in Example 1-1. When the same measurement as in Example 1 was performed,
It was found that the solar cell (SC Ex. 5) of this example had more excellent characteristics than (SC Ex. 1-1).

(Example 6) A solar cell having the maximum hydrogen content near the interface between the RFp type layer and the MWp type layer was manufactured. When the RF p-type layer was formed, the RF power was changed over time, and when the MWp-type layer was formed, the MW power was changed over time to obtain a hydrogen content change pattern as shown in FIG. Except for this, it was manufactured under the same conditions as in Example 1-1. The same measurement as in Example 1 was performed, and it was found that the solar cell (SC Ex. 6) of this example had more excellent characteristics than (SC Ex. 1-1).

Example 7 A solar cell in which the content of the valence control agent was maximized near the interface between the MWp type layer and the RFp type layer was manufactured. When forming the MWp type layer and the RFp type layer, the source gas of the valence electron controlling agent to be introduced was changed with time to obtain a change pattern of the B atom content as shown in FIG. 9A. Except for this, it was manufactured under the same conditions as in Example 1-1. The same measurement as in Example 1 was performed, and it was found that the solar cell (SC Ex. 7) of this example had more excellent characteristics than (SC Ex. 1-1).

Example 8 The content of the valence electron controlling agent in the i-type layer has the structure shown in FIG. 1A, changes smoothly in the layer thickness direction, and the content on the p-type layer side. Was manufactured (SC Ex 8). When forming an i-type layer,
Same as Example 1-1 except that the PH ₃ / H ₂ gas flow rate and the B ₂ H ₆ / H ₂ gas flow rate were changed over time to make the contents of P atoms and B atoms as shown in FIG. 9C. Solar cell (S
C Ex 8) was produced. Except for the semiconductor layer, the same one as in Example 1-1 was used. When the same measurement as in Example 1 was performed, the produced solar cell (SC Ex. 8) was (SC Ex. 1-1).
It has been found that it has more excellent properties than the above.

(Example 9) A solar cell (SC Ex. 9) in which fluorine was contained in the MWp type layer and the RFp type layer was manufactured. M
When forming the Wp-type layer and the RFp-type layer, BF ₃ / H
By introducing _two gases and changing the flow rate over time, the change in the fluorine content in the layer thickness direction was as shown in FIG. 5 (c). In addition, the B ₂ H ₆ / H ₂ gas was also changed with time to change the B content in the layer thickness direction as shown in FIG. 9 (c). Other conditions were the same as in Example 1-1. Example 1
When the same measurement as described above was performed, the produced solar cell (SC
Example 9) was found to have more excellent properties than (SC Example 1-1).

Example 10 A solar cell using a-SiSn for the i-type layer was manufactured. GeH ₄ gas cylinder SnH
_{4 When} replacing the (tin hydride) cylinder and forming the i-type layer, the flow rate of the SiH ₄ gas was changed with time in the same change pattern as in FIG. 7A, and the flow rate of the SnH ₄ gas was changed as shown in FIG. G
Change the time in the same manner as the eH ₄ gas flow rate change,
₃ Gas flow rate is 1 sccm, B ₂ H ₆ / H ₂ gas flow rate is 2
sccm, H ₂ gas flow rate 300 sccm, layer thickness 18
A solar cell (SC Ex. 10) was produced under the same conditions as in Example 1-1 except that the thickness was set to 0 nm.

(Comparative Example 10-1) In forming an i-type layer,
The flow rate of the SiH ₄ gas and the flow rate of the SnH ₄ gas were kept constant over time, and were set to 120 sccm and 30 sccm, respectively.
1) was produced.

(Comparative Example 10-2) Example 1 was repeated except that the RFp type layer was not formed and the MWp type layer had a thickness of 20 nm.
A solar cell (SC ratio 10-2) was manufactured under the same conditions as in Example 1.

The same measurement as in Example 1 was performed. As a result, the solar cell (SC Ex. 10) of this example was further improved than the conventional solar cells (SC ratio 10-1) and (SC ratio 10-2). It was found to have excellent properties.

(Example 11) In forming an i-type layer, the MW
A solar cell (SC Ex 11) in which the power was changed over time was manufactured. SiH ₄ gas flow rate is 110 sccm, SiF ₄
Gas flow rate is 10 sccm, GeH ₄ gas flow rate is 30 sccm
cm, constant in time, and MW power is 0.20 W
A solar cell (SC Ex. 11) was produced in the same manner as in Example 1, except that the density was monotonically increased from / cm ³ to 0.30 W / cm ³ . When the change in the Ge content in the layer thickness direction was obtained in the same manner as in Example 1, it was found that the change was as shown in FIG. Further, when the band gap in the layer thickness direction was determined, it was found that the band gap was as shown in FIG. When the same measurement as in Example 1 was performed,
It was found that the solar cell (SC Ex. 11) of this example had more excellent characteristics than the conventional solar cells (SC ratio 1-1) and (SC ratio 1-2).

(Example 12) Between the RF p-type layer and the i-type layer,
2 having PR-i layer between RF n-type layer and i-type layer
The solar cell of (c) was produced. Form two RF-i layers
A solar cell was fabricated in the same manner as in Example 8 except that
Was. The RF-i type layer is made of a-Si, _FourGas flow
The amount is 2sccm, SiF_FourGas flow rate is 0.5sccm,
H_TwoGas flow rate 50 sccm, PH_Three/ H_TwoGas flow
0.2sccm, B_TwoH₆/ H_TwoGas flow is 0.5sc
cm, pressure in the deposition chamber is 1.0 Torr, RF to be introduced
Power is 0.01W / cm^Three, Substrate temperature is 270 ° C, layer thickness
Was formed under the condition of 20 nm. The fabricated solar cell (SC
Example 12) has more excellent properties than (SC Example 8)
I found out.

Example 13 A triple solar cell as shown in FIG. 10 was manufactured using the manufacturing apparatus of FIG. 6 using the MWPCVD method.

First, a substrate was manufactured. A 50 × 50 mm ² stainless steel substrate was subjected to ultrasonic cleaning with acetone and isopropanol and dried in the same manner as in Example 1. Using a sputtering method, a layer thickness of 0.3
A light reflective layer of μm of Ag was formed.

At this time, the substrate temperature was set to 350 ° C., and the substrate surface was made uneven (textured). A ZnO reflection enhancement layer having a layer thickness of 2.0 μm was formed thereon at a substrate temperature of 350 ° C.

Next, preparation for film formation was completed in the same manner as in Example 1. The first MWn is formed on the substrate in the same manner as in the first embodiment.
Forming a first type n-type layer (a-Si), a first i-type layer (a-SiGe), and a first RFp-type layer (a-Si layer thickness 10 nm) , The first MWp
Type layer (μc-Si layer thickness 10 nm), second RF n-type layer (μc-Si), second i-type layer (a-Si), second R
Fp type layer (a-SiC layer thickness 10 nm), second MWp type layer (μc-SiC layer thickness 10 nm), third RF n type layer (a-SiC), third i type layer (a-SiC) , Third RFp type layer (a-SiC layer thickness 10 nm), third MW
A p-type layer (μc-SiC layer thickness 10 nm) was sequentially formed. When forming the first i-type layer, the SiH ₄ gas flow rate, G
The eH ₄ gas flow rate was changed over time as shown in FIG.
In other layers, when forming a layer formed by the MWPCVD method, the MW power is changed over time, and when forming a layer formed by the RFPCVD method, the RF power is changed over time to distribute the hydrogen content of each layer. Is as shown in FIG. 8 (c).

Next, a transparent electrode similar to that of Example 1 was formed on the third MWp type layer. Next, a current collecting electrode similar to that of Example 1 was formed on the transparent electrode by a vacuum evaporation method.

Thus, the triple solar cell (SC Ex. 13)
Finished.

(Comparative Example 13-1) The same operation as in Example 13 except that the flow rate of the SiH ₄ gas was set to 120 sccm, the flow rate of the GeH ₄ gas was set to 30 sccm, and the time was constant when forming the first i-type layer. Solar cell (SC ratio 13-
1) was produced.

(Comparative Example 13-2) The first RFp type layer, the second RFp type layer, and the third RFp type layer were not formed,
A first MWp type layer, a second MWp type layer, and a third M
A solar cell (SC ratio 13-2) was manufactured under the same conditions as in Example 13 except that the thickness of the Wp-type layer was set to 20 nm.

The same measurement as in Example 1 was performed. As a result, the solar cell (SC Ex. 13) of the present example was more excellent than the conventional solar cells (SC ratio 13-1) and (SC ratio 13-2). It was found to have excellent properties.

Example 14 A tandem solar cell shown in FIG. 11 was manufactured by using a manufacturing apparatus using the roll-to-roll method shown in FIG.

First, a long stainless sheet having a length of 300 m, a width of 30 cm, and a thickness of 0.1 mm, both surfaces of which were mirror-polished, was used as the substrate. A substrate temperature of 3 is formed on the surface of the stainless steel substrate by a sputtering apparatus using a roll-to-roll method.
A reflective layer made of Ag having a layer thickness of 0.3 μm is continuously formed at 50 ° C., and a Zn layer having a layer thickness of 2.0 μm is formed at a substrate temperature of 350 ° C.
A reflection increasing layer made of O was continuously formed. It was found that the surface of the substrate was textured as in Example 13.

FIG. 12 is a schematic view of an apparatus for continuously forming a semiconductor layer using a roll-to-roll method. The apparatus includes a substrate delivery chamber 1010 and a plurality of deposition chambers 1001 to 1010.
09 and the substrate take-up chamber 1011 are sequentially arranged, and a separation path 1012 is connected between them. A long-sized substrate 1013 passes through these, and is continuously connected from the substrate unloading chamber to the substrate take-up chamber. And the semiconductor layers can be simultaneously formed in the respective deposition chambers simultaneously with the movement of the substrate.

Reference numeral 1050 is a view of the deposition chamber as viewed from above. Each deposition chamber has a source gas inlet 1014 and a source gas exhaust port 1015, and an RF electrode 1016 or a microwave applicator 1017 is attached as needed. Halogen lamp heater 1 for heating the substrate
018 is installed inside. Source gas inlet 1
The devices 014 are connected to the same components as the source gas supply device 2000 of FIG. 6, and the exhaust ports of the source gases are connected to vacuum exhaust pumps such as an oil diffusion pump and a mechanical booster pump. Each RF
An RF power supply is connected to the electrodes, and a MW power supply is connected to the microwave applicator. The separation passage connected to the deposition chamber has an inlet 1019 through which scavenging gas flows. The substrate delivery chamber includes a delivery roll 1020 and a guide roll 1021 for applying an appropriate tension to the substrate and keeping the substrate always horizontal, and the substrate take-up chamber includes a take-up roll 1022 and a guide roll 1023.

First, the substrate on which the above-mentioned reflection layer and reflection enhancement layer are formed is wound around a delivery roll, set in a substrate delivery chamber, passed through each deposition chamber, and then wound around a substrate take-up roll. The entire apparatus is evacuated by an unillustrated evacuation pump, the lamp heaters in each deposition chamber are turned on, and the substrate temperature in each deposition chamber is set to a predetermined temperature. From the inlet 1019 of the scavenging gas When the pressure of the whole apparatus becomes less than 1mTorr allowed to flow H ₂ gas, while moving the substrate in the direction indicated by the arrow in the illustration, it will wound at a take-up roll. In the same manner as in the first embodiment, each source gas flows into each deposition chamber. At this time, the flow rate of the H ₂ gas flowing into each separation passage or the pressure of each deposition chamber is adjusted so that the raw material gas flowing into each deposition chamber does not diffuse into other deposition chambers.

Next, glow discharge is generated by introducing RF power or MW power to form respective semiconductor layers.

A first MWn-type layer (μc-Si layer thickness: 20 nm) is formed on a substrate in a deposition chamber 1001, and a first RF n-type layer (a-Si layer thickness: 10n) is deposited in a deposition chamber 1002.
m), a first i-type layer (a-SiGe)
The first RFp type layer (a-Si layer thickness 10 nm) in the deposition chamber 1004, the first MWp type layer (μc-Si layer thickness 10 nm) in the deposition chamber 1005, and the deposition chamber 10
06, the second RF n-type layer (μc-Si layer thickness 20 n
m), a second i-type layer (a-Si layer thickness 2)
50 nm), a second RFp-type layer (a-
SiC layer thickness 10 nm), second MW in deposition chamber 1009
A p-type layer (μc-SiC layer thickness 10 nm) was sequentially formed. For forming the semiconductor layers, SiH ₄ gas and SiF ₄ gas were used, and fluorine was contained in all the semiconductor layers. First
The source gas inlet of the deposition chamber 1003 for forming the i-type layer is divided into a plurality of portions, and SiH ₄ gas and S
iF ₄ gas, GeH ₄ gas, and H ₂ gas were introduced. i
When forming the mold layer, each mass flow controller was adjusted so that the change pattern of the GeH ₄ gas flow rate in the transport direction of the substrate became a change pattern as indicated by an arrow 1026. Thus, the change in the Ge content of the i-type layer in the layer thickness direction became as shown in FIG. When the transfer of the substrate is completed, turn off the MW power supply and RF power supply,
The glow discharge was stopped, and the inflow of the raw material gas and the scavenging gas was stopped. The entire apparatus was leaked, and the wound substrate was taken out.

Next, a 70 nm-thick ITO transparent electrode was continuously formed on the second MWp type layer at 170 ° C. by a sputtering apparatus using a roll-to-roll method.

Next, a part of this substrate was cut into a 50 mm × 50 mm
Is cut into a size, a carbon paste having a layer thickness of 5 μm and a line width of 0.5 mm is printed by a screen printing method, and a silver paste having a layer thickness of 10 μm and a line width of 0.5 mm is printed thereon. Formed.

Thus, the production of the tandem solar cell (SC Ex. 14) using the roll-to-roll method has been completed.

(Comparative Example 14-1) A solar cell (1) was formed under the same conditions as in Example 14 except that the flow rate of GeH ₄ gas was kept constant in the substrate transfer direction when forming the first i-type layer. S
C ratio 14-1) was produced.

(Comparative Example 14-2) The first RFp type layer and the second RFp type layer were not formed, and the first MWp type layer,
A solar cell (SC ratio 14-2) was manufactured under the same conditions as in Example 14 except that the thickness of the second MWp type layer was set to 20 nm.

The same measurement as in Example 1 was performed. As a result, the solar cell (SC Ex. 14) of this example was further more improved than the conventional solar cells (SC ratio 14-1) and (SC ratio 14-2). It was found to have excellent properties.

(Example 15) A tandem solar cell manufactured by using the manufacturing apparatus of FIG. 12 was modularized, applied to a power generation system, and subjected to a field test.

The light-irradiated 50 mm produced in Example 14
65 x 50mm triple solar cells (SC Ex 14)
I prepared a piece. E on a 5.0 mm thick aluminum plate
An adhesive sheet made of VA (ethylene vinyl acetate) is placed thereon, a nylon sheet is placed thereon, and 6
Five solar cells were arranged and serialized and parallelized. An EVA adhesive sheet was placed thereon, and a fluororesin sheet was placed thereon, followed by vacuum lamination to form a module. The initial photoelectric conversion efficiency of the manufactured module was measured in the same manner as in Example 1. The circuit was connected to the circuit showing the power generation system of FIG. 13, and a streetlight that was lit at night was used as the load. The whole system runs on the battery and the power of the module. This power generation system will be called (SBS actual 15).

(Comparative Example 15) Using 65 conventional tandem-type solar cells (SC ratio 14-1) and (SC ratio 14-2) not irradiated with light, they were modularized in the same manner as in Example 15, and the initial photoelectric conversion was performed. The efficiency was measured. This module was connected to the same power generation system as in Example 15. These power generation systems are referred to as (SBS ratio 15-1), (SBS ratio 15-
Let's call it 2).

Each of the modules was set at an angle capable of collecting sunlight most. The measurement of the field test was performed by measuring the photoelectric conversion efficiency after a lapse of one year and obtaining the deterioration rate (photoelectric conversion efficiency after one year / initial photoelectric conversion efficiency).

As a result, the power generation system using the solar cell according to the present invention (SBS Actual 15) is the same as the conventional power generation system (SB
It was found that they had better initial photoelectric conversion efficiency and field durability than (S ratio 15-1) and (SBS ratio 15-2).

(Example 16) A photovoltaic element containing oxygen and / or nitrogen atoms in a semiconductor layer was manufactured. First,
The PF ₅ / H ₂ gas cylinder was replaced with an O ₂ gas (abbreviated as “O ₂ / He gas”) cylinder diluted to 500 ppm with He, and the BF ₃ / H ₂ gas cylinder was further replaced with He by 10 p.
It was replaced with a N ₂ gas (abbreviated as “N ₂ / He gas”) cylinder diluted to pm.

(Example 16-1) In forming an i-type layer,
A solar cell (SC Ex 16-1) was produced under the same conditions as in Example 1 except that O ₂ / He gas was introduced at 100 sccm.

(Example 16-2) In forming an i-type layer,
Example 1 except that N ₂ / He gas was introduced at 20 sccm.
Under the same conditions as above, a solar cell (SC Ex 16-2) was produced.

(Example 16-3) In forming an i-type layer,
100 sccm of O ₂ / He gas and ₂ N ₂ / He gas
A solar cell (SC Ex 16-3) was produced under the same conditions as in Example 1 except that 0 sccm was introduced.

(Example 16-4) In forming the RF-i layer, O ₂ / He gas was ₂ sccm, and N ₂ / He gas was 1
A solar cell (SC Ex 16-4) was produced under the same conditions as in Example 1 except that sccm was introduced.

Example 16-5 A solar cell (SC Ex. 16) was formed under the same conditions as in Example 1 except that an O ₂ / He gas was introduced at 100 sccm and a N ₂ / He gas was introduced at 20 sccm when forming the MWp type layer. -5) was produced.

(Example 16-6) In forming an RFp type layer, O ₂ / He gas was ₂ sccm, and N ₂ / He gas was 1
A solar cell (SC Ex. 16-6) was produced under the same conditions as in Example 1 except that sccm was introduced.

When the same measurement as in Example 1 was performed,
It was found that the solar cells of (SC Ex 16-1) to (SC Ex 16-6) had more excellent characteristics than (SC Ex 1).

When the concentrations of oxygen atoms and nitrogen atoms in these fabricated solar cells were examined by SIMS, the concentration of the raw material gas (O) and the raw material gas (N) were almost the same as those of the introduced raw material gas (Si). It was found to be contained.

As described above, it was proved that the effect of the photovoltaic device of the present invention was exhibited irrespective of the device configuration, device material, and device manufacturing conditions.

[0296]

[Table 1]

[0297]

[Table 2]

[0298]

[Table 3]

[0299]

Industrial Applicability According to the present invention, light having improved photoelectric conversion efficiency by preventing recombination of photoexcited carriers, improving the open-circuit voltage and the carrier range of holes, improving the sensitivity to short-wavelength light and long-wavelength light. It is possible to provide an electromotive element.

Further, the photovoltaic element of the present invention can suppress light deterioration and vibration deterioration. The photovoltaic element of the present invention can suppress light deterioration and vibration deterioration even when placed in a high-temperature, high-humidity environment, and does not peel off. Further, the photovoltaic device of the present invention can increase the deposition rate of the photovoltaic device and can use the source gas at a high efficiency, so that the productivity can be dramatically improved.

Further, according to the present invention, it is possible to provide a power generation system having high field durability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a layer configuration of a photovoltaic device of the present invention.

FIG. 2 is a schematic view showing a layer configuration of a photovoltaic element of the present invention.

FIG. 3 is a graph showing a change in germanium content in a layer thickness direction.

FIG. 4 is a graph showing a change in a band gap in a layer thickness direction.

FIG. 5 is a graph showing a change in a fluorine content in a layer thickness direction.

FIG. 6 is a schematic view showing an example of a photovoltaic element manufacturing apparatus.

FIG. 7 is a graph showing a time change of SiH ₄ gas and GeH ₄ gas flow rates, and a change of a Ge content and a band gap in a layer thickness direction.

FIG. 8 is a graph showing a change in a hydrogen content in a layer thickness direction.

FIG. 9 is a graph showing a change in the thickness direction of a valence electron controlling agent.

FIG. 10 is a schematic diagram illustrating a layer configuration of a triple solar cell.

FIG. 11 is a schematic view showing a layer configuration of a tandem solar cell.

FIG. 12 is a schematic view showing an example of a photovoltaic device manufacturing apparatus using a roll-to-roll method.

FIG. 13 is a block diagram illustrating an example of a power generation system.

[Code description]

 101, 111, 121 Substrate 102, 122 MWn-type layer 103, 123 RFn-type layer 104, 114 i-type layer 105, 115 RFp-type layer 106, 116 MWp-type layer 107, 117, 127 Transparent electrode 108, 118, 128 Electrode 112 n-type layer 125 p-type layer 400 deposition apparatus 401 deposition chamber 402 vacuum gauge 403 RF power supply 404 substrate 405 heater 406 waveguide 407 conductance valve 408 auxiliary valve 409 leak valve 410 RF electrode 411 gas introduction pipe 412 applicator 413 dielectric Window 415 Shutter 1001 to 1009 Deposition chamber 1010 Substrate unloading chamber 1011 Substrate winding chamber 1012 Separation passage 1013 Long substrate 1014 Source gas inlet 1015 Source gas exhaust port 1016 RF electrode 1 17 microwave applicator 1018 a halogen lamp heater 1019 scavenging gas inlet 1020 feed roll 1021,1023 guide roll 1022 winding roll 2000 material gas feed system 2010 to 2019 mass flow controllers 2020 to 2039 the valve 2040 to 2049 pressure regulators 2050 to 2059 source-gas cylinder

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 31/04

Claims (18)

(57) [Claims] A p-type layer, an i-type layer, and an n-type layer made of a non-single-crystal silicon-based semiconductor material containing hydrogen are sequentially laminated on a substrate, and the i-type layer is made of fluorine and germanium or / and And tin and microwave plasma C
In the photovoltaic device formed by the VD method, at least one of the p-type layer and the n-type layer is formed by a layer (MW doping layer) formed by a microwave plasma CVD method and an RF plasma CVD method. Layer (RF doping layer), and the RF doping layer is disposed so as to be sandwiched between the MW doping layer and the i-type layer, and further contains germanium or The photovoltaic device wherein the content of tin and / or tin changes smoothly in the thickness direction. 2. The germanium and / or tin content is minimized near at least one of the two interfaces of the i-type layer, and is closer to the p-type layer than the center of the i-type layer. 2. The photovoltaic device according to claim 1, wherein the value is maximum. 3. The photovoltaic device according to claim 1, wherein the i-type layer contains both a valence electron controlling agent serving as a donor and a valence electron controlling agent serving as an acceptor. 4. The content of the valence electron controlling agent serving as a donor and the valence electron controlling agent serving as an acceptor is 2% of the i-type layer.
4. The photovoltaic device according to claim 3, wherein the maximum value is obtained near at least one of the two interfaces. 5. The method according to claim 1, wherein the content of fluorine contained in the i-type layer changes smoothly in the thickness direction of the layer and becomes minimum near at least one interface of the layer. The photovoltaic device according to any one of Items 1 to 4, wherein 6. The MW doping layer and / or RF
The photovoltaic device according to any one of claims 1 to 5, wherein the content of the valence electron controlling agent is maximized in the vicinity of at least one of the two interfaces of the doping layer. . 7. The MW doping layer and / or RF
The photovoltaic device according to any one of claims 1 to 6, wherein the doping layer contains fluorine. 8. The method according to claim 1, wherein the content of fluorine contained in the MW-ooping layer and / or the RF doping layer changes smoothly in the thickness direction of the layer, and becomes minimum near at least one interface of the layer. The photovoltaic device according to claim 7, characterized in that: 9. At least one of the MW doping layer, the RF doping layer and the i-type layer has a maximum hydrogen content near at least one of two interfaces. The photovoltaic device according to claim 1, wherein: 10. The method according to claim 1, wherein at least one of the MW doping layer, the RF doping layer, and the i-type layer is formed of oxygen or / and / or i-type.
And a nitrogen atom.
The photovoltaic element according to any one of the above. 11. An i-type layer (RF) formed by RF plasma CVD between the i-type layer and the RF doping layer.
The photovoltaic device according to any one of claims 1 to 10, wherein the photovoltaic device has an i-layer. 12. The photovoltaic device according to claim 11, wherein the RF-i layer contains both a valence electron controlling agent serving as a donor and a valence electron controlling agent serving as an acceptor. 13. The content of a valence electron controlling agent serving as a donor and a valence electron controlling agent serving as an acceptor contained in the RF-i layer is maximum near at least one of two interfaces. The photovoltaic device according to claim 12, wherein: 14. The RF-i layer according to claim 11, wherein at least one of two interfaces of the RF-i layer has a maximum hydrogen content in the vicinity of the interface. 3. The photovoltaic device according to claim 1. 15. The RF-i layer according to claim 11, wherein the RF-i layer contains oxygen and / or nitrogen atoms.
The photovoltaic element according to any one of the above. 16. The photovoltaic device according to claim 11, wherein the RF-i layer contains fluorine. 17. The method according to claim 1, wherein the content of fluorine contained in the RF-i layer changes smoothly in the thickness direction of the layer and is minimized near at least one interface of the layer. 17. The photovoltaic element according to 16. 18. The photovoltaic device according to claim 1, wherein a voltage and / or a current of the photovoltaic device is monitored to supply power from the photovoltaic device to a storage battery and / or an external load. A power generation system, comprising: a control system that controls supply; and a storage battery that stores power from the photovoltaic element and / or supplies power to an external load.