JP3027669B2 - Photovoltaic element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having a pin layer made of a non-single-crystal silicon-based semiconductor material and having a zinc oxide thin film layer between a base and the pin layer. The photovoltaic element is suitably applied to a solar cell, a photodiode, an electrophotographic photosensitive member, a light emitting element and the like.

[0002]

2. Description of the Related Art In recent years, photovoltaic devices using a zinc oxide (ZnO) thin film layer as a transparent conductive film have been energetically studied. For example, (i) “Optimization of Transparent and Reflecting El
ectrodes for AmorphousSilicon Solar Cells ”, Gordo
n RG, Hu J, Musher J, Giunta C, US DOE Rep. pp.44
In 1991, ZnO having a texture structure doped with fluorine was improved. (ii) “Research on amorphous silicon based thin fil
m photovoltaic devices.Task B: Research on stable
high efficiency, large area amorphous silicon base
d submodules ”, Delahoy AE, Ellls FB Jr, Kampas
FJ, Tonon T, Weakllem HA, US DOE Rep.pp.48 198
9 reports a solar cell using excellent high-grade doped ZnO. (iii) “Amorphous silicon pin solar cells using ind
ium doped ZnO transparent conducting coatings ”, S
ansores E, Campos J, Nair PK, Photovoltaic Sol.En
ergy Conf. vol. 8th No. 1 pp. 1008 1988, reports a solar cell using ZnO doped with indium. (iv) JP-A-62-259480 describes a solar cell using ZnO containing silicon as an impurity, but in the present invention, silicon in ZnO is contained not as an impurity but as a constituent element. In addition, the content is changed. Furthermore, the physical phenomena that bring about the effects are also different.

In addition, microwave plasma CVD (MWP)
A solar cell using the CVD method has also been studied as follows. (v) "a-Si solar cell by microwave plasma CVD", Kazufumi Higashi, Takeshi Watanabe, Juichi Shimada, Proc. 566, and the like. In this photovoltaic element, an i-layer having good quality and a high deposition rate is obtained by forming the i-layer by the MWPCVD method.

[0004] Examples of the doping layer formed by the MWPCVD method include, for example, (vi) “High Efficiency Amorphous Solar Cell Employi”.
ng ECR-CVD Produced p-Type Microcrystalline SiC Fi
lm ”, Y. Hattori, D. Kruangam, T. Toyama, H. Okamoto a
nd Y. Hamakawa, Proceedings of the International PVS
EC-3 Tokyo Japan 1987 pp.171, (vii) “HIGH-CONDUCTIVE WIDE BAND GAP P-TYPE a-SiC:
H PREPARED BY ECR CVDAND ITS APPlICATION TO HIGH E
FFICIENCY a-Si BASIS SOLAR CELLS ”, Y. Hattori, DK
ruangam, K. Katou, Y. Nitta, H. Okamoto and Y. Hamakaw
a, Proceedings of 19th IEEE Photovoltaic Specialist
s Conference 1987 pp.689. In these photovoltaic elements, a high quality p layer is obtained by using the MWPCVD method for the p layer.

[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, (viii) “Research on practical application of amorphous solar cells, Research on manufacturing technology for highly reliable elements of amorphous solar cells”, Overview of R & D on Sunshine Project. Solar energy1. Light utilization technology VOL.1985 pp.I.231-I.243 1986, (ix) “The chemical and configurational basis of hi
gh efficiency amorphous photovoltaic cells ”, Ovsh
insky.SR, Proceedings of 17th IEEE Photovoltaic Sp
ecialists Conference 1985 pp.1365, (x) “Development of the scientific and technical b
asis for integrated amorphous silicon modules.Res
erch on a-Si: F: H (B) alloys and module testing at I
ET-CIEMAT. ”, Gutierrez MT, P Delgado L, Photovol
t. Power Gener., pp. 70-75 1988, (xi) “The effect of fluorine on the photovoltaic p
roperties of amorphossilicon ”, Konagai.M, Nishiha
ta.K, Takahashi.K, Komoro.K, Proceedings of 15th IE
EE Photovoltaic Specialists Conference 1981 pp.90
6, etc.

However, even in these examples, the photodegradation phenomenon and the thermal stability are mentioned, but the delamination of the semiconductor layer is not mentioned. Research on photovoltaic elements containing microcrystalline silicon is also being made vigorously, but no mention is made of delamination.

[0007] In USP 4,400,409 patent specification
Adopts a roll-to-roll method
In addition, a plasma CVD apparatus for continuously forming a semiconductor layer is used.
It has been disclosed. The photovoltaic device of the present invention has such a device.
It is desirable to manufacture continuously using a device. This device
According to, a plurality of deposition chambers are provided,
Disposing a substrate along a path in which the substrate sequentially passes through the deposition chamber;
Forming a semiconductor layer having a desired conductivity type in the deposition chamber.
While continuously transporting the substrate in its longitudinal direction
As a result, a photovoltaic element having a pin junction can be continuously connected.
It is said that it can be manufactured on demand. The specification
In the book, the semiconductor layer contains each valence control agent
Source gas diffuses into other deposition chambers and
Gas gates are used to prevent
ing. Specifically, a slit-shaped separation between the deposition chambers
Are separated from each other by passages, and further, Ar,
H _Two, He and other scavenging gases are allowed to flow in, and the
Mutual diffusion is prevented. This roll-to-roll method
The method of forming a photovoltaic element is used when producing a photovoltaic element as in the present invention.
Is effective.

In the above conventional photovoltaic device, ZnO /
Improvement in suppression of recombination of photoexcited carriers near the pin layer interface and the ZnO / substrate interface is desired. Further, in these photovoltaic elements, it is desired to improve the open-circuit voltage and the short-circuit current.

Further, when light is irradiated for a long time, the photoelectric conversion efficiency is reduced, that is, so-called light deterioration is a problem. In addition, when vibration is applied for a long time, the photoelectric conversion efficiency is reduced, that is, so-called vibration deterioration is a problem. Further, there has been a problem of light deterioration and vibration deterioration when a bias voltage is applied to the photovoltaic element.

Further, in the case of a photovoltaic device in which the base contains at least one element of Ag, Al, and In, when a bias voltage is applied to the photovoltaic device and left for a long time,
There was a problem such as a short circuit.

Further, when a non-single-crystal silicon-based semiconductor layer containing microcrystalline silicon is formed on a ZnO thin film layer, there is a problem that the layer is easily peeled as compared with a layer containing no microcrystalline silicon.

Further, there is a problem that a non-single-crystal silicon-based semiconductor layer containing fluorine is easily peeled off when formed on a zinc oxide thin film layer as compared with a layer containing no fluorine.

Further, there has been a problem that the ZnO thin film layer formed by the roll-to-roll method is easily peeled off when stored in a roll and wound for a long time or transported.

[0014]

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, the object is to suppress the recombination of photoexcited carriers near the ZnO / pin layer interface and the ZnO / substrate interface. Another object is to improve the open-circuit voltage and the short-circuit current, and to improve the photoelectric conversion efficiency.

Another object is to suppress light deterioration and vibration deterioration. It is another object of the present invention to suppress light deterioration and vibration deterioration at the time of bias voltage. Further, Ag, Al,
An object of a photovoltaic element containing at least one element of In is to prevent a short circuit even when a bias voltage is applied to the photovoltaic element and the photovoltaic element is left for a long time.

It is another object of the present invention to prevent delamination even in a photovoltaic device in which a non-single-crystal silicon-based semiconductor layer containing microcrystalline silicon is formed on a ZnO thin film layer. Another object is to prevent delamination even in a photovoltaic element having a non-single-crystal silicon-based semiconductor layer containing fluorine. It is an object of the present invention to provide a photovoltaic element which is hardly delaminated even in a rolled state.

[0017]

The present invention solves the problems of the prior art, and as a result of intensive studies to achieve the above object,
It has been found that the photovoltaic device of the present invention comprises:
In a photovoltaic device in which a zinc oxide thin film layer and a pin layer (p layer, i layer, and n layer) made of a non-single-crystal silicon-based semiconductor material are stacked on a substrate, the zinc oxide thin film layer has a surface of zero. A c-axis oriented crystalline thin film having irregularities of 1 to 1.0 μm, containing silicon, and having a minimum silicon content at the interface with the substrate, And gradually increases toward the surface of the zinc oxide thin film layer.
It is characterized in that a large amount of silicon is contained in the vicinity of a crystal grain boundary .

A preferred embodiment of the present invention is a photovoltaic device in which the c-axis is substantially perpendicular to the substrate surface.

[0019]

A preferred embodiment of the present invention is a photovoltaic device in which the p layer or the n layer in contact with the zinc oxide thin film layer contains microcrystalline silicon.

A preferred embodiment of the present invention is a photovoltaic device in which the p layer or the n layer in contact with the zinc oxide thin film layer contains fluorine.

A preferred embodiment of the present invention is a photovoltaic device in which the substrate is a flexible band-shaped substrate and can be wound in a roll.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic illustration of a photovoltaic device according to the present invention. In FIG. 1, a photovoltaic element of the present invention has a substrate 101, a surface having irregularities and a c-axis orientation.
nO thin film layer 102, pin layer 103 made of non-single-crystal silicon-based semiconductor material, transparent electrode 104, current collecting electrode 105
And so on.

In the photovoltaic element shown in FIG. 1, light is normally applied from the transparent electrode side, but may be applied from the back side of the substrate. In this case, the base may be made of a material that transmits light, and a light reflection layer made of a metal material may be formed on the pin layer instead of the transparent electrode.

The pin layer of the photovoltaic device of the present invention
It may be a stack of pin structures such as an inpin structure and a pinpinpin structure.

The pin layer of the photovoltaic device of the present invention has n
A stack of nip structures such as an ip structure, a nipnip structure, and a nipnipnip structure may be used.

In the photovoltaic device of the present invention, the ZnO thin film layer contains silicon, and its content changes smoothly,
Since it is minimum at the interface with the substrate and gradually increases toward the pin layer, the interface between the ZnO thin film layer and the pin layer
This is to reduce recombination of photoexcited carriers at the interface between the O thin film layer and the substrate.

The interface between the ZnO thin film layer and the pin layer, Z
Since the internal stress generated at the interface between the nO thin film layer and the substrate is reduced, photodegradation of the photovoltaic element (deterioration of element properties due to long-time light irradiation) and vibration degradation (element properties due to long-term vibration application) Decrease). That is, it is considered that the photodegradation of the photovoltaic element breaks the weak bond due to the energy of light, and this becomes the center of recombination of the photoexcited carriers, thereby deteriorating the element characteristics. In addition, vibration degradation of the photovoltaic element breaks weak bonds due to vibration energy, which becomes the recombination center of photoexcited carriers,
It is considered that the element characteristics deteriorate. This weak bond is considered to be localized in the area where stress is generated,
It is particularly important to reduce the recombination centers generated at the interface between the ZnO thin film layer and the pin layer.

Further, since a trace amount of silicon in the ZnO thin film works as a valence electron controlling agent, the conductivity of the film can be improved, and the light transmittance of the ZnO thin film is not impaired. That is, when light is irradiated from the transparent electrode 104 side, light that could not be absorbed by the pin layer can be transmitted efficiently, and short-circuit current can be improved. When light is irradiated from the back side of the base 101, the light is efficiently guided to the pin layer.

In the present invention, a ZnO thin film layer having a c-axis orientation and being crystalline is used. As a result, irregularities are formed on the surface of the ZnO thin film as shown in FIG.
It can be led to the in layer, and the short-circuit photocurrent of the photovoltaic element can be improved. That is, when light is incident from the transparent electrode side, the light is refracted on the transparent electrode surface and the pin layer surface, so that the optical path length from the incident on the pin layer to the light reaching the crystalline ZnO layer surface is extended. P, more light
Can be absorbed in the in layer. Further, when the base is made of a material that reflects light, light that could not be absorbed by the pin layer can be once again made to enter the pin layer from the base and absorbed.

At this time, since the surface of the crystalline ZnO thin film layer 102 has irregularities, the reflected light can be refracted here, the optical path length can be extended, and the light can be absorbed more effectively. In order to absorb visible light, the unevenness can effectively absorb visible light when the height of the peak is 0.1 to 1.0 μm.

JP-A-62-259480 discloses that Zn
Although it is intended to prevent opacity (irregularities on the surface) of the O thin film layer, in the present invention, rather, the surface is positively eroded (textured) to make the surface opaque.

In particular, it is desirable that each crystal grain 107 is a wurtzite crystal and the c-axis (six rotation axis) is substantially perpendicular to the substrate. This makes p more effective
Light can be guided to the in layer. To make the c-axis almost perpendicular to the substrate, when forming a ZnO thin film layer by a sputtering method, a DC bias and / or an RF bias is applied to increase the plasma potential, or a negative D
Apply a C bias. Further, in order to make the c-axis substantially perpendicular to the base, countless fine projections may be formed on the surface of the base. For example, an Ag thin film layer may be formed on a stainless steel support at a support temperature of 200 to 600 ° C. It is desirable that the projections are formed at substantially equal intervals.

Further, by including a large amount of silicon in the crystal grain boundary 106, diffusion of impurities from the substrate can be prevented. That is, when a material containing an impurity (for example, a certain metal element) that adversely affects the pin layer is used for the base, the impurity must be prevented from diffusing into the pin layer. In the case of a crystalline ZnO thin film layer as shown in FIG. 1, impurities diffuse through crystal grain boundaries, which may degrade device characteristics. In particular, when a bias voltage is applied to the element for a long time, it becomes particularly noticeable, the shunt resistance becomes extremely small, and characteristics such as photoelectric conversion efficiency deteriorate. This is presumably because voids and voids are present at the crystal grain boundaries, so that impurities are easily diffused. Therefore, by including a large amount of silicon in the crystal grain boundaries,
These voids and voids are reduced to prevent diffusion. In addition, by containing a large amount of silicon in the crystal grain boundaries, dangling bonds are increased, and react with diffused impurities to prevent diffusion. It is desirable that the content of silicon be several times larger than that inside the crystal bulk.

In the present invention, the p-layer or the n-layer in contact with the ZnO thin film layer preferably contains microcrystalline silicon. A p-layer or an n-layer containing microcrystalline silicon has the advantageous characteristics of higher conductivity, less photodegradation and thermal stability than those containing no microcrystalline silicon, but the film is denser. Therefore, there was a problem that the layer was easily peeled off. However, in the present invention, since a large amount of silicon is contained in the surface of the ZnO thin film layer, delamination is difficult.

In the present invention, p in contact with the ZnO thin film layer
Preferably, the layer or the n-layer contains fluorine. The fluorine-containing p-layer or n-layer has higher conductivity than those not containing fluorine, has less light degradation, and has the advantageous characteristics of being thermally stable, but because the film is denser,
There was a problem if the layers were easily separated. However, in the present invention, Zn
Since a large amount of silicon is contained on the surface of the O thin film layer, stress is reduced, interlayer bonding force is increased, and delamination is difficult.

In the photovoltaic device of the present invention, the p layer or the n layer
Layer and the i-layer are formed by RF plasma CVD (RFPCVD).
Method) or microwave plasma CVD method (MWPCVD)
Method). Especially MWPCVD
According to the method, the deposition rate is high, the throughput can be improved, and the utilization efficiency of the source gas can be improved, so that the productivity can be improved. When the doping layer is formed by the MWPCVD method, a doping layer having good characteristics as a photovoltaic element can be obtained. That is, the doping layer is excellent as a doping layer because of good light transmittance, high electric conductivity, and low activation energy. Further, when formed by the MWPCVD method, a high-quality microcrystalline silicon-based semiconductor material or a high-quality amorphous silicon-based semiconductor material having a wide band gap can be relatively easily formed, which is effective as a method for forming a doping layer. The i-layer is particularly effective because the i-layer is thicker than the p-layer and the n-layer.

The ZnO thin film layer of the present invention is preferably formed by a sputtering method. Among them, a magnetron sputtering method with a high deposition rate and a microwave sputtering method described below are suitable. Microwave sputtering method "inerts an inert gas or a reactive gas into a vacuum vessel, generates ions by irradiating the gas with microwaves, and accelerates the ions by applying electromagnetic energy to a target. To form a deposited film on the substrate surface at high speed by irradiating the target surface with the target and sputtering the target. The electromagnetic energy is suitably RF or DC power.

Since the photovoltaic element of the present invention has a ZnO thin film layer and a pin layer formed on a flexible strip-shaped substrate, it can be wound into a roll and takes up space for storage or transportation. And handling becomes easy. It is also suitable for a manufacturing method using a roll-to-roll method, and can dramatically improve productivity. In the photovoltaic element of the present invention, since the ZnO thin film layer contains silicon as described above, it is difficult for the layer to be peeled even in a rolled state.

The photovoltaic element having the pin structure has been described above.
b, a photovoltaic element in which a pin structure such as a pinpinpin structure is laminated, or a nipnip structure or ni
The present invention is also applicable to a photovoltaic element in which a nip structure such as a pnnip structure is stacked.

FIG. 2 is a schematic explanatory view of a deposition apparatus suitable for producing the photovoltaic element of the present invention. The deposition device 2
00 is a deposition chamber 201, a vacuum gauge 202, a bias power supply 2
03, substrate 204, heater 205, waveguide 206, conductance valve 207, valve 208, target electrode 209, bias electrode 210, gas introduction pipe 211,
It comprises an applicator 212, a dielectric window 213, a sputtering power supply 214, a base shutter 215, a target 216, a target shutter 217, a microwave power supply 219, a toroidal coil 221, a vacuum exhaust pump (not shown), a source gas supply device, and the like. The vacuum exhaust pump is connected to an exhaust port 220 shown in the figure, and the source gas supply device is composed of a source gas cylinder, a valve, and a mass flow controller, and is connected to a gas introduction pipe 211. The dielectric window is made of a material that transmits microwaves well, such as alumina ceramics, quartz, and boron nitride.

The fabrication of the photovoltaic device of the present invention is performed as follows. First, the substrate 204 is brought into close contact with the heater 205 provided in the deposition chamber 201 of FIG. 2, and the deposition chamber is sufficiently evacuated to 1 × 10 ⁻⁵ Torr or less. A turbo molecular pump, an oil diffusion pump, or a cryopump is suitable for this exhaust. Thereafter, an inert gas such as Ar is introduced into the deposition chamber, the heater is turned on, and the substrate is heated. When the substrate temperature is stabilized at a predetermined temperature, the conductance valve 207 is adjusted to a predetermined pressure, and a method of forming a ZnO thin film layer described in detail below is performed. Next, a method of forming a pin layer described in detail below is performed. Next, the target is In ₂ O _{3 in} a vacuum.
+ SnO ₂ (5 wt%) and replace O ₂ in the deposition chamber.
A gas is introduced, and a DC magnetron sputtering method is performed to form ITO on the pin layer. Next, the deposition chamber is leaked, and a comb-shaped current collecting electrode is formed on the ITO surface by an electron beam vacuum evaporation method, thereby completing the fabrication of the photovoltaic element.

The pin layer is formed by MWPCVD or RFP
It is preferably formed by a CVD method. (A) When the pin layer is formed by the MWPCVD method When the pin layer is formed by the MWPCVD method, the source gas is introduced into the deposition chamber, the pressure is adjusted by the conductance valve 207, and the microwave is applied to the waveguide 206 and the applicator 2.
Irradiation is performed on the source gas through 12 to generate plasma. The pressure during the formation of the pin layer is a very important factor, and the optimal pressure in the deposition chamber is 0.5 to 50 mTorr.
Is preferred. The MW power introduced into the deposition chamber is
It is an important factor. The MW power is appropriately determined by the flow rate of the source gas introduced into the deposition chamber,
A preferable range is 100 to 5000 W. M
A preferable frequency range of W power is 0.5 to 10 G
Hz. Particularly, a frequency around 2.45 GHz is suitable. After forming the desired layer thickness, the introduction of MW power is stopped, the deposition chamber is sufficiently evacuated, and the next layer is formed after sufficiently purging with a gas such as H ₂ , He, or Ar.

When forming the pin layer, RF power may be applied to the bias electrode 210 together with MW power. In this case, the MW power to be introduced is desirably smaller than the MW power required to decompose the raw material gas introduced into the deposition chamber by 100%, and the RF power simultaneously introduced is preferably larger than the MW power. desirable. A preferable range of the simultaneously introduced RF power is 200 to 1000
0W. A preferable frequency range of the RF power includes 1 to 100 MHz. Especially 13.56MHz
Is optimal. When the area of the bias electrode for RF power supply is smaller than the area of the ground, it is better to ground the self-bias (DC component) on the power supply side for RF power supply. Further, a DC voltage may be applied to the bias electrode. A preferred range of the DC voltage is 30 to 300
About V. Further, RF power and DC voltage may be simultaneously applied to the bias electrode.

(B) When a pin layer is deposited by RFPCVD, a capacitively coupled RFPCVD method is suitable. When a pin layer is formed by the RFPCVD method, a source gas is introduced into a deposition chamber, and RF power is applied to a bias electrode to generate plasma. The substrate temperature is 100 to 500 ° C., the pressure is 0.1 to 10 Torr, the RF power is 1 to 2000 W,
The optimum deposition rate is 0.1 to 2 nm / sec. After forming the desired layer thickness, the introduction of MW power is stopped, the deposition chamber is sufficiently evacuated, and the next layer is formed after sufficiently purging with a gas such as H ₂ , He, or Ar.

The following method can be used to form a ZnO thin film layer containing silicon and varying its content.

(1) In case of forming by sputtering method RF magnetron sputtering method or DC magnetron sputtering method, which has a high forming speed, is suitable. In that case, an Ar gas and an O ₂ gas are introduced into a deposition chamber in which a toroidal coil is set around the target, a target made of ZnO: Si containing silicon is mounted on the target electrode 209, and the substrate temperature is set to 200. ~ 600
° C, and RF (1 to 100 MHz) power or DC power is applied to generate plasma to form a ZnO thin film layer on the substrate.

At this time, the pressure in the deposition chamber is a parameter closely related to the formation rate of the deposited film, and is appropriately determined according to the type of gas to be introduced, the size of the deposition apparatus, and the like. Usually, it is 1 to 30 mTorr. A predetermined amount of the above-mentioned gas is introduced into the deposition chamber from the gas cylinder via the mass flow controller, and the introduction amount is appropriately determined depending on the volume of the deposition chamber. Further, O ₂ gas may be introduced in addition to Ar gas.

To change the silicon content in the layer thickness direction, the RF power or the DC power may be changed over time. That is, for ZnO and silicon, the sputtering rate RF
Since the power (DC power) dependence is different, the silicon content is high at a high RF power (DC power), and the silicon content is low at a low RF power (DC power).

Further, in order to increase the silicon content at the crystal grain boundary, the RF content should be increased immediately before each crystal grain comes into contact with a neighboring crystal grain.
The power (DC power) may be increased.

(2) In the case of forming by sputtering method + RFPCVD method In the above-mentioned RF (DC) magnetron sputtering method, a silicon-containing gas such as SiH ₄ gas or Si ₂ H ₆ is newly introduced, and the amount of introduction is controlled by time. You only need to change it. In this case, a target made of ZnO containing no silicon may be used. Further, in order to increase the silicon content at the crystal grain boundary, a large amount of gas containing silicon may be flowed immediately before each crystal grain comes into contact with a neighboring crystal grain.

(3) When Forming by Microwave Sputtering Method Ar gas is introduced into the deposition chamber, the target made of ZnO: Si is mounted on the target electrode 209, the substrate temperature is set to 200 to 600 ° C., and RF (1 to 100 MH
z) Apply power or DC power (100-600V). The microwave power generated from the microwave power source is transmitted, expanded in the applicator, and irradiated with the above gas through the dielectric window 213 to generate plasma to form a ZnO thin film layer on the substrate.

At this time, the pressure in the deposition chamber is a parameter closely related to the formation rate of the deposited film, and is appropriately determined depending on the type of gas to be introduced, the size of the deposition apparatus, and the like. Usually, it is 0.1 to 10 mTorr. In addition, the above gas is introduced into the deposition chamber from the gas cylinder through a mass flow controller in a predetermined amount.
The introduction amount is appropriately determined depending on the volume of the deposition chamber. Further, O ₂ gas may be introduced in addition to Ar gas.

To change the silicon content in the layer thickness direction, the RF power or the DC power may be changed over time. That is, for ZnO and silicon, the sputtering rate RF
Since the power (DC power) dependence is different, the silicon content is high at a high RF power (DC power), and the silicon content is low at a low RF power (DC power).

Further, in order to increase the silicon content at the crystal grain boundary, the RF should be increased immediately before each crystal grain comes into contact with a neighboring crystal grain.
The power (DC power) may be increased.

(4) Microwave sputtering method + MW
When forming by PCVD method In the microwave sputtering method described above, Si is newly added.
A gas containing silicon, such as H ₄ gas or Si ₂ H _6, may be introduced, and the introduced amount may be changed over time. In this case, a target made of ZnO containing no silicon may be used.

Further, in order to increase the silicon content at the crystal grain boundary, a large amount of gas containing silicon may be flowed immediately before each crystal grain comes into contact with a neighboring crystal grain.

(5) When Forming by Roll-to-Roll Method In the microwave sputtering method or the ordinary sputtering method, the substrate temperature is set to 200 to 600 ° C.
A new gas containing silicon, such as SiH ₄ gas or Si ₂ H _6, may be introduced, and the introduced amount may be changed spatially with respect to the moving direction of the substrate.

Further, in order to increase the silicon content at the crystal grain boundary, a large amount of a gas containing silicon may be flowed where each crystal grain comes into contact with a neighboring crystal grain.

In the above-described method for forming the pin layer, the following gases or compounds capable of being gasified by bubbling are suitable as the source gas.

Source gases for containing silicon atoms include SiH ₄ , SiD ₄ , Si ₂ H ₆ , SiF ₄ and Si ₂
F ₆ is suitable.

Suitable source gases for containing fluorine atoms are F ₂ , SiF ₄ , GeF ₄ , CF ₄ , PF ₅ and BF ₃ .

As a raw material gas for containing carbon atoms,
The CH_Four, CD_Four, C_TwoH_Two, CF _FourIs suitable.

As a source gas for containing germanium atoms, GeH ₄ , GeD ₄ and GeF ₄ are suitable.

Suitable source gases for containing tin atoms are SnH ₄ , SnD ₄ , and Sn (CH ₃ ) ₄ .

Source gases for introducing Group III atoms of the periodic table into the p layer include B ₂ H ₆ , B (CH ₃ ) ₃ , and B
(C ₂ H ₅ ) ₃ , Al (CH ₃ ) ₃ and BF ₃ are suitable.

As a source gas for introducing a group V atom of the periodic table into the n-layer, PH ₃ , AsH ₃ and PF ₅ are suitable.

H ₂ S and H ₂ Se are suitable as source gases for introducing a Group VI atom of the periodic table into the n-layer.

O ₂ , CO ₂ , CO, and NO are suitable as source gases for containing oxygen atoms in the pin layer.

N ₂ , NO, NO ₂ , N ₂ O, NH _3, etc. are suitable as the source gas for containing nitrogen atoms in the pin layer.

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

In the case of forming the above-mentioned silicon-containing ZnO thin film layer, the target may be ZnO or ZnO.
O: Uses Si but does not contain oxygen Zn or Z
n: Si may be used. Silicon is an oxide (SiO ₂ )
The target may be contained in the form of When a target containing no oxygen is used, it is necessary to introduce O ₂ gas into the deposition chamber. As a gas introduced to contain silicon in the ZnO thin film layer, SiH ₄ , SiD ₄ , Si
₂ H ₆ , SiF ₄ and Si ₂ F ₆ are suitable.

Hereinafter, the configuration of the present invention will be described in more detail. Substrate The substrate may be composed of a simple substance of a conductive material or an insulating material, or may be a material in which a thin film layer is formed on a support made of a conductive material or an insulating material.

As the conductive material, for example, NiCr,
Stainless steel, Al, Cr, Mo, Au, Nb, Ta,
Metals such as V, Ti, Pt, Pb, Sn and the like, and alloys thereof are exemplified. In order to use these materials as a support, it is desirable that the material be in the form of a sheet or a roll formed by winding a belt-like sheet around a cylindrical body.

As the insulating material, 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 that the material be in the form of a sheet or a roll formed by winding a belt-like sheet around a cylindrical body.

In the photovoltaic device of the present invention, it is preferable that a conductive thin film layer is formed on one surface of the support, and a ZnO thin film layer is formed on the surface on which the conductive thin film layer is formed.

For example, in the case of glass, NiC
r, Al, Ag, Cr, Mo, Ir, Nb, Ta, V,
Ti, Pt, Pb, In ₂ O ₃ , SnO ₂ , ITO (In ₂
A conductive thin film layer made of a material such as O ₃ + SnO ₂ ) or an alloy thereof is formed, and if a synthetic resin sheet such as a polyester film is used, NiCr, Al, Ag, Pb, Z
n, Ni, Au, Cr, Mo, Ir, Nb, Ta, V,
A conductive thin film layer made of a material such as Tl or Pt or an alloy thereof is formed. If stainless steel is used, NiCr, Al, A
g, Cr, Mo, Ir, Nb, Ta, V, Ti, Pt,
Pb, In ₂ O ₃ , SnO ₂ , ITO (In ₂ O ₃ + Sn
A conductive thin film layer made of a material such as O ₂ ) or an alloy thereof is formed. As a forming method, it is formed by a vacuum deposition method, a sputtering method, a screen printing method, or the like.

The surface shape of the substrate is desirably smooth or uneven with a peak height of 0.1 to 1.0 μm on average. The thickness of the substrate is appropriately determined so that a desired photovoltaic element can be formed. However, when flexibility as a photovoltaic element is required, a range in which the function as a support is sufficiently exhibited is provided. Can be made as thin as possible. However,
The thickness is usually 10 μm or more from the viewpoint of production and handling of the support, mechanical strength and the like.

As a desirable base form in the photovoltaic device of the present invention, Ag, Al, Cu, A
The purpose is to form a conductive thin film layer made of a metal having high reflectance in the near infrared to visible light such as lSi. This layer functions as a light reflection layer, and a suitable layer thickness of these metals as the light reflection layer is 10 nm to 5000 nm. In order to make the surface of the light reflection layer uneven (texture), the substrate temperature at the time of formation may be 200 ° C. or higher.

ZnO Thin Film Layer Zn containing silicon formed by the above method
The light transmittance of the O thin film layer is 85% or more in the wavelength range of 400 nm to 900 nm, and the resistivity is 3 ×
It is less than 10 ⁻⁴ Ω · cm. The silicon content has a minimum value (Cmin) at the interface with the substrate and gradually increases in the direction of the pin layer. Further, the maximum value (Cmax) of the silicon content is taken at the crystal grain boundary. About 0.1% is suitable as Cmin, and about 10% is suitable as Cmax. As the change pattern of the silicon content in the layer thickness direction, a pattern which increases linearly from the substrate side as shown in FIG. 3-a, a pattern which increases exponentially from the substrate side as shown in FIG. 3-b,
As shown in FIG. 3C, a material that rapidly increases near the interface with the pin layer is suitable.

P layer, n layer This layer is an important layer that affects the characteristics of the photovoltaic element, and is composed of an amorphous silicon-based semiconductor material, a microcrystalline silicon-based semiconductor material, or a polycrystalline silicon-based semiconductor material. Is done.

Examples of amorphous (abbreviated as a-) silicon-based semiconductor materials include a-Si, a-SiC, and a-SiG.
e, a-SiGeC, a-SiO, a-SiN, a-S
iON, a-SiCON and the like. Microcrystal (μc
The silicon-based semiconductor material is μc-
Si, μc-SiC, μc-SiGe, μc-SiO,
μc-SiGeC, μc-SiN, μc-SiON, μ
c-SiOCN, and the like. Polycrystalline (poly-
The silicon-based semiconductor material is poly
—Si, poly-SiC, poly-SiGe, and the like.

In particular, as the 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-SiC, a-
SiO, a-SiN, a-SiON, a-SiCON,
μc-Si, μc-SiC, μc-SiO, μc-Si
N, μc-SiON, μc-SiOCN, poly-S
i, poly-SiC is suitable.

The 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.

The contained hydrogen (H, D) and fluorine work to compensate for dangling bonds and improve the doping efficiency. Hydrogen and fluorine content is 0.1-3
0 at% is mentioned as the optimum amount. In particular, in the case of crystallinity, 0.01 to 10 at% is mentioned as an optimum amount.

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.

As for the electrical characteristics, the activation energy is set to 0.1.
Those having 2 eV or less are preferable, and those having 0.1 eV or less are optimal. The resistivity is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less.

Further, the layer thickness is preferably 1 to 50 nm,
３０30 nm is optimal.

In particular, when a crystalline semiconductor material having little light absorption as described above or an amorphous semiconductor layer having a wide band gap is formed, the source gas is increased 2 to 100 times with a gas such as H ₂ , D ₂ or He. It is preferable to dilute and introduce relatively high MW or RF power.

Further, in the photovoltaic device of the present invention, silicon is contained in the ZnO thin film layer, and the content gradually increases toward the pin layer. Layer or n-layer, Z
Damage to the nO thin film layer, that is, interface level can be reduced.

I-Layer In the photovoltaic device of the present invention, the i-layer is the most important layer for generating and transporting photoexcited carriers. A slightly p-type or slightly n-type layer can be used as the i-layer, and is made of an amorphous silicon-based semiconductor material containing hydrogen.
Si, a-SiC, a-SiGe, a-SiGeC, a
-SiSn, a-SiSnC, a-SiSnGe, a-
SiSnGeC and the like can be mentioned.

Hydrogen (H, D) and fluorine contained in the i-layer work to compensate for dangling bonds in the i-layer, and improve the product of the carrier mobility and the lifetime in the i-layer. .
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 hydrogen and fluorine contents of the i-layer are 1 to 3
0 at% is mentioned as the optimum content.

The introduction amount of oxygen and nitrogen atoms is from 0.1 ppm to
1% is a suitable range. The thickness of the i-layer depends on the structure of the photovoltaic element (for example, pin, pinpin, nip) and i
0.05 to 1.0 μm depending on the band gap of the layer
Is an optimum layer thickness.

The i-layer of the present invention has a small tail state on the valence band side, and has a tail state inclination of 60.
The density is less than meV and the density of dangling bonds by electron spin resonance (ESR) is 10 ¹⁷ / cm ³ or less.

The MWCVD method is used to form the i-layer. Preferably, RF power is simultaneously introduced in the MWPCVD method as described above.
RF power and DC power are simultaneously introduced in the PCVD method.

In the case of forming a-SiC having a wide band gap, it is preferable to dilute the source gas 2 to 100 times with a gas such as H ₂ , D ₂ , He, and to introduce a relatively high MW power.

Transparent Electrodes Transparent electrodes are suitable materials of indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and ITO (In ₂ O ₃ + SnO ₂ ). These materials contain fluorine. You may.

For forming a transparent electrode, a sputtering method and a vacuum evaporation method are optimal. When formed by a sputtering method, a target such as a metal target or an oxide target is used in appropriate combination.

In the case of forming by a sputtering method, the substrate temperature is an important factor, and a preferable range is from 20 ° C. to 600 ° C. A gas for sputtering when the transparent electrode is formed by a sputtering method is A
and inert gas such as r gas. 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 above-mentioned inert gas or the like, the pressure is set to effectively perform sputtering.
0.1-50 mTorr is mentioned as a preferable range. The deposition rate of the transparent electrode depends on the pressure and the power introduced, and the optimal deposition rate is 0.01 to 10 nm / s.
ec.

[0101] As a vapor deposition source suitable for forming a transparent electrode in the vacuum vapor deposition method, metal tin, metal indium,
An indium-tin alloy is exemplified. A suitable range of the substrate temperature for forming the transparent electrode is from 25 ° C. to 600 ° C. Further, it is necessary to introduce oxygen gas (O ₂ ) and form the pressure in a 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 form 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 decreases, and
If it is larger than / sec, the film becomes coarse, and the transmittance, the electrical conductivity and the adhesion are reduced.

It is preferable that the thickness of the transparent electrode satisfy the conditions of the antireflection film. As a specific layer thickness, a preferable range is 50 to 500 nm.

The collecting electrode In order to make more light incident on the i-layer, which is the photovoltaic layer, and to efficiently collect generated carriers at the electrode, the shape of the collecting electrode (as viewed from the light incident direction) , And material are important. Usually, the shape of the current collecting electrode is a comb shape, and the line width, the number of lines, and the like are as follows:
And the size, the material of the collecting electrode, and the like. The line width is usually about 0.1 mm to 5 mm. As the material of the collecting electrode, Fe, Cr, Ni, Au, Ti, Pd, A
g, Al, Cu, AlSi, C (graphite), etc. are used, and Ag, Cu, Al, C
Metals such as r and C or alloys thereof are suitable.
The layer structure of the collecting electrode may be composed of a single layer, or may be composed of a plurality of layers.

It is desirable to form these metals 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 evaporation method, a mask having a shape of a collecting electrode is brought into close contact with the transparent electrode, and a desired metal evaporation source is evaporated in a vacuum by electron beam or resistance heating.
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, Ar gas is introduced into a vacuum, DC power is applied to a desired metal sputter target, and glow discharge is performed. By causing this, the 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, or a carbon paste is printed by a screen printing machine.

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

[0109]

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 A solar cell having the structure shown in FIG. 1 was manufactured using the deposition apparatus shown in FIG.

A source gas supply device (not shown) is connected to the deposition device of FIG. 2 through a gas introduction pipe. All raw material gas cylinders have been purified to ultra-high purity.
₄ gas cylinder, SiF ₄ gas cylinder, CH ₄ gas cylinder,
GeH ₄ gas cylinder, SnH ₄ gas cylinder, PH ₃ / H
₂ (dilution: 100 ppm) gas cylinder, B ₂ H ₆ / H
₂ (Dilution: 100 ppm) A gas cylinder, an H ₂ gas cylinder, and an Ar gas cylinder were connected. Targets are Ag and Z
There is nO: Si (1%), and sputtering can be performed by switching each in a vacuum. An RF power supply was used as a bias power supply.

First, a substrate was manufactured. 0.5m thick
A 50 × 50 mm ² stainless steel plate was subjected to ultrasonic cleaning with acetone and isopropanol and dried with hot air. A DC power supply was connected as a sputtering power supply, and an Ag light reflecting layer was formed using a DC magnetron sputtering method. The stainless plate was brought into close contact with the heater of FIG. 2, and the deposition chamber was evacuated from the exhaust port 220 to which the oil diffusion pump was connected.
When the pressure reaches 1 × 10 ^-6 Torr, Ar gas is supplied for 50 seconds.
The pressure was adjusted to 7 mTorr by a conductance valve. When the substrate temperature reached 150 ° C., a current was passed through the toroidal coil, and a DC power of 400 V was applied from a sputtering power supply to generate Ar plasma.

When the target shutter and the base shutter were opened to form a 0.3 μm-thick Ag light reflecting layer on the surface of the stainless steel plate, the two shutters were closed to extinguish the plasma, completing the manufacture of the base.

Next, a ZnO thin film layer having a silicon content varying in the layer thickness direction was formed by the formation method (1). The target electrode was switched to an RF power source, Ar gas was introduced at 50 sccm into the deposition chamber, the substrate temperature was 350 ° C., and the pressure was 5 m.
At Torr, RF power of 300 W was applied from a sputtering power source to the target electrode to generate Ar plasma. The target shutter and the base shutter were opened. When the RF power was monotonically increased with time to form a ZnO thin film layer containing silicon having a thickness of 0.7 μm on the surface of the Ag light reflection layer, the two shutters were closed to extinguish the plasma.

Next, an n-layer, an i-layer, and a p-layer were sequentially formed on the ZnO thin film layer. The n-layer made of a-Si and the i-layer made of a-Si were formed by RFPCVD, and the p-layer made of a-SiC was formed by MWPCVD.

To form an n-layer made of a-Si, H
₂ gas was introduced at 300 sccm, and the pressure in the deposition chamber was 1.
At 0 Torr, when the substrate temperature was stabilized at 250 ° C.,
SiH ₄ gas 2sccm, PH ₃ / H ₂ gas 200scc
m, H ₂ gas of 100 sccm was introduced, and the pressure in the deposition chamber was adjusted to 1.0 Torr. Set the power of the RF power supply to 5 W, apply RF power to the bias electrode,
Plasma was generated, the base shutter was opened, the formation of an n-layer on the ZnO thin film layer was started, and when the n-layer having a thickness of 20 nm was formed, the shutter was closed and the RF power was turned off.
The plasma was extinguished to complete the formation of the n-layer. SiH ₄ gas into the deposition chamber, stopping the flow of PH ₃ / H ₂ gas for 5 minutes, after which continued to flow H ₂ gas into the deposition chamber, stopping the inflow of the H ₂ gas, the deposition chamber and the gas in the pipe 1 × 10 ^-5 To
Evacuated to rr.

To form an i-layer made of a-Si, H
₂ gas is introduced at 500 sccm and the pressure is 1.5 Torr
r, The substrate temperature was set to 250 ° C. When the substrate temperature becomes stable, SiH ₄ gas is introduced, and the flow rate of SiH ₄ gas is 50 sccm, and the flow rate of H ₂ gas is 500 sccc.
m and the pressure in the deposition chamber were adjusted to 1.5 Torr. Next, the power of the RF power source was set to 50 W and applied to the bias electrode to generate plasma, the base shutter was opened, the formation of the i-layer on the n-layer was started, and the layer thickness was 250 nm.
When the i-layer was formed, the shutter was closed, the RF power was turned off, the plasma was extinguished, and the formation of the i-layer was completed.
SiH ₄ stop the flow of gas, 5 minutes, after which continued to flow H ₂ gas, stopping the inflow of the H ₂ gas was evacuated deposition chamber and the gas in the pipe up to 1 × 10 ^-5 Torr.

To form a p-layer made of a-SiC,
H ₂ gas was introduced at 500 sccm, the pressure in the deposition chamber was set to 0.02 Torr, and the substrate temperature was set to 200 ° C. When the substrate temperature becomes stable, SiH ₄ gas, C
H ₄ gas and B ₂ H ₆ / H ₂ gas were introduced. At this time, Si
H ₄ gas flow rate is 10 sccm, CH ₄ gas flow rate is 2 scc
m, H ₂ gas flow rate is _{100sccm, B 2 H 6 / H} 2 gas flow rate was adjusted to 500 sccm, the pressure becomes 0.02 Torr. Thereafter, the power of the MW power supply is set to 500 W, the MW power is introduced through the dielectric window, plasma is generated, the base shutter is opened, the formation of the p layer is started on the i layer, and the p layer having a layer thickness of 10 nm is formed. Was formed, the shutter was closed, the MW power was turned off, the plasma was extinguished, and the formation of the p-layer was completed. SiH ₄ gas, CH ₄ gas, B
₂ H ₆ / H ₂ stop the flow of gas, 5 minutes, after which continued to flow H ₂ gas, stopping the inflow of the H ₂ gas, and evacuating the deposition chamber and the gas in the pipe up to 1 × 10 ^-5 Torr, The deposition chamber leaked.

Next, a transparent electrode having a thickness of 7 was formed on the p-layer.
0 nm of ITO was vacuum deposited by a resistance heating vacuum deposition method.
Next, a mask having a comb-shaped hole is placed on the transparent electrode, and Cr
(40 nm) / Ag (1000 nm) / Cr (40 n
m) was vacuum-deposited by an electron beam vacuum deposition method.

Thus, the production of the solar cell has been completed. This solar cell will be referred to as (SC Ex. 1).

Comparative Example 1-1 Example 1 was repeated except that the RF power was kept constant over time when the ZnO thin film layer was formed.
Under the same conditions as above, a solar cell (SC ratio 1-1) was produced.

(Comparative Example 1-2) A solar cell (SC ratio 1-1) was formed under the same conditions as in Example 1 except that ZnO containing no silicon was used as a target when forming a ZnO thin film layer.
2) was produced.

(Comparative Example 1-3) A solar cell (SC ratio 1-3) was manufactured under the same conditions as in Example 1 except that the temperature of the base was 80 ° C when forming the ZnO thin film layer.

The solar cell (SC actual 1) and (SC ratio 1−
1), (SC ratio 1-2), and (SC ratio 1-3) were prepared six each, and the initial photoelectric conversion efficiency (photovoltaic power / incident light power), vibration deterioration, light deterioration, and bias voltage application The measurement of vibration deterioration and light deterioration at the time was performed.

The initial photoelectric conversion efficiency was determined based on the solar cell fabricated.
With AM-1.5 (100 mW / cm ^Two) Installed under light irradiation
And obtained by measuring the VI characteristics.

For the measurement of vibration deterioration, 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 25 ° C., and a vibration having a vibration frequency of 60 Hz and an amplitude of 0.1 mm was performed for 500 hours. After the addition, the reduction rate of the photoelectric conversion efficiency under AM-1.5 light irradiation (photoelectric conversion efficiency after vibration deterioration test / initial photoelectric conversion efficiency) was used.

The photodegradation was measured by installing 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 irradiating AM-1.5 light for 500 hours.
The measurement was performed based on the rate of decrease in photoelectric conversion efficiency under AM-1.5 light irradiation (photoelectric conversion efficiency after light deterioration test / initial photoelectric conversion efficiency).

As a result of the measurement, (S
C ratio 1-1), (SC ratio 1-2), (SC ratio 1-3), initial photoelectric conversion efficiency, reduction rate of photoelectric conversion efficiency after photodegradation,
The rate of decrease in photoelectric conversion efficiency after vibration degradation was as follows. These differences were mainly due to differences in open-circuit voltage and differences in short-circuit photocurrent.

Initial photoelectric conversion efficiency Vibration deterioration Light deterioration (SC actual 1) 1.00 times 1.00 times 1.00 times (1-1 of SC ratio) 0.96 times 0.92 times 0.94 times (SC ratio) 1-2) 0.95 times 0.93 times 0.95 times (SC ratio 1-3) 0.94 times 0.92 times 0.94 times First, when the surface of the solar cell was observed with an electron microscope,
In (SC Ex. 1), (SC Comp. 1-1), and (SC Comp. 1-2), the surface is uneven (texture) as shown in FIG. 1, and the surface unevenness is measured using a surface roughness meter. As a result, it was found that the average peak height was about 0.12 μm.
The surface irregularities (SC ratio 1-3) were 0.05 μm or less.

Next, samples of the ZnO thin film layer used for the four solar cells were prepared, and the crystallinity was evaluated using an X-ray diffractometer. (SC actual 1), (SC ratio 1-1), (SC ratio 1-1) Although the composition has c-axis orientation in the ratio 1-2), the (SC ratio 1-
In 3), it was found that it did not have crystallinity.

Next, the change of the silicon content in the layer thickness direction of the manufactured (SC Ex. 1) was obtained using SIMS, and as shown in FIG. It was found that the value varied depending on the RF power of the sputtering power supply. In (SC ratio 1-1), there is no change in the layer thickness direction. In (SC ratio 1-2), no silicon is detected. In (SC ratio 1-3), a change similar to (SC actual 1) is obtained. Was done.

As described above, the solar cell (SC Ex. 1) of the present invention is different from the conventional solar cell (SC ex.
-2) and (SC ratio 1-3).

(Example 2) A solar cell having the configuration shown in FIG. 1 in which the c-axis was substantially perpendicular to the substrate and the silicon content was large at the crystal grain boundaries was produced. In Example 1, A
g When forming the light reflecting layer, the substrate temperature was set to 350 ° C.
When forming the ZnO thin film layer, a solar cell (SC Ex. 2) was produced in the same manner as in Example 1, except that the RF power of the sputter power supply was suddenly increased immediately before the contact of each crystal grain.

When the same measurement as in Example 1 was performed, the vibration degradation and light degradation were almost the same, but the solar cell of (SC Ex. 2) was more excellent in initial photoelectric conversion than (SC Ex. 1). It has been found to be efficient. This is because the surface irregularities were optimized and the short-circuit current was improved.

(Comparative Example 2-1) A solar cell was manufactured in the same manner as in Example 2, except that a target not containing silicon was used when forming the ZnO thin film layer.

(Comparative Example 2-2) A solar cell was manufactured in the same manner as in Example 2, except that the RF power of the sputtering power supply was constant when forming the ZnO thin film layer.

(Comparative Example 2-3) A solar cell (SC ratio 2-3) similar to that of Example 2 was prepared except that the substrate temperature was set to 80 ° C when forming the ZnO thin film layer.

First, when the surface of the solar cell was observed with an electron microscope, (SC Ex. 2), (SC ratio 2-1), (SC ex.
In the ratio 2-2), the surface is uneven (texture) as shown in FIG. 1. When the surface unevenness was examined using a surface roughness meter, the average peak height was about 0.21 μm. I understood. The unevenness of (SC ratio 2-3) has a peak height of 0.
It was not more than 05 μm.

When the crystallinity was measured using an X-ray diffractometer, (SC Ex. 2), (SC ratio 2-1), (SC ex.
In the ratio 2-2), it was found that there was c-axis orientation, and the c-axis was perpendicular to the substrate. (SC ratio 2-3) was found to have no orientation and no crystallinity.

Further, measurement of vibration deterioration and light deterioration was performed by applying a forward bias. Solar cells (SC actual 2), whose initial photoelectric conversion efficiency was measured in advance, (SC ratio 2-1),
(SC ratio 2-2) and (SC ratio 2-3) were measured at a humidity of 50% and a temperature of 25 ° C., and a voltage of 0.8 V was applied as a forward bias voltage to measure vibration deterioration and light deterioration.

As a result of the measurement, it was found that (SC Ex. 2) had better characteristics than (SC Ex. 2-1), (SC Ex. 2-2) and (SC Ex. 2-3).

Example 3 A photodiode (PD Ex. 3) having the layer configuration shown in FIG. 1 was manufactured. First, a base was produced. A 0.5 mm thick, 20 × 20 mm ² glass substrate is ultrasonically cleaned with acetone and isopropanol, dried with hot air, and the light reflection of 0.1 μm thick Al on a glass substrate surface at room temperature by a vacuum evaporation method. The layer was formed, and the production of the base was completed. In the same manner as in Example 1, a ZnO thin film layer, an n layer (a-Si: P RFPCVD method), and an i layer (a
-Si RFPCVD method), p-layer (a-SiC: BM)
WPCVD method). When the ZnO thin film layer is formed, it is performed by the formation method of (2), using a target not containing silicon and using Si as a gas containing silicon.
The H ₄ gas was introduced, the flow rate was changed over time, and the silicon content was changed as shown in FIG. Next, the same transparent electrode and current collecting electrode as in Example 1 were formed on the p layer.

Comparative Example 3-1 A photodiode (PD ratio 3-1) was formed under the same conditions as in Example 3 except that the flow rate of the SiH ₄ gas was not changed when forming the ZnO thin film layer.
Was prepared.

(Comparative Example 3-2) A photodiode (PD ratio 3-2) was manufactured under the same conditions as in Example 3 except that no SiH ₄ gas was introduced when forming the ZnO thin film layer.

(Comparative Example 3-3) A photodiode (PD ratio 3-3) was manufactured under the same conditions as in Example 3 except that the temperature of the substrate was 80 ° C. when forming the ZnO thin film layer.

The on / off ratio (photocurrent / dark current measurement frequency of 10 kHz when AM-1.5 light was irradiated) of the manufactured 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. As a result, the photodiode (PD actual 3) of the present invention has more excellent characteristics than the conventional photodiodes (PD ratio 3-1), (PD ratio 3-2), and (PD ratio 3-3). I understood.

Example 4 A solar cell (SC Ex. 4) of FIG. 1 having a nip-type structure in which a p-layer containing microcrystalline silicon was formed on a ZnO thin film layer was manufactured. A ZnO thin film layer was formed in the same manner as in Example 1, and a p-layer (μc
-Si: B RFPCVD method), i-layer (a-Si RF
PCVD method), n-layer (a-SiC: P MWPCVD)
Method). When the ZnO thin film layer was formed, it was performed by the formation method of (3), and the RF power was changed with time to make the silicon content as shown in FIG. A transparent electrode and a current collecting electrode were formed in the same manner as in Example 1.

When the same measurement as in Example 1 was performed, the solar cell (SC Ex. 4) of the present invention was similar to the conventional solar cell (SC Comp. 1-1) and (SC Comp. -2),
(SC ratio 1-3) It turned out that it has the more excellent characteristic.

Example 5 A solar cell (SC Ex. 5) containing fluorine in the n-layer was manufactured. When forming the n-layer, Si
It was manufactured under the same conditions as in Example 2 except that 1 sccm of F ₄ gas was newly introduced.

Comparative Example 5 When forming a ZnO thin film layer,
A solar cell (SC ratio 5) was produced under the same conditions as in Example 5 except that a ZnO target containing no silicon was used.

The same measurement as in Example 1 was performed, and it was found that the solar cell (SC Ex. 5) had better characteristics than (SC ratio 5). In (SC Ex. 5), no delamination was observed, but in (SC ratio 5), delamination was slightly observed.

(Example 6) A ZnO thin film layer similar to that of Example 2 was formed on a glass substrate.
Except for flowing ₄ gas at 10 sccm, the same p
Solar cell in which a layer, an i-layer, and an n-layer are formed and a light reflecting layer made of Al and having a thickness of 0.5 μm is formed on the pin layer (SC Ex. 6)
Was prepared. The light reflecting layer was formed by an electron beam vacuum evaporation method.

(Comparative Example 6) When forming a ZnO thin film layer,
A solar cell (SC ratio 6) similar to that of Example 6 was produced except that the solar cell was formed using a target not containing silicon.

The same measurement as in Example 1 was carried out by irradiating light from the back surface of the glass substrate.
It was found to have characteristics superior to the ratio 6).

Example 7 The pinpi of FIG. 4A was used by using the deposition apparatus using the roll-to-roll method of FIG.
An n-type solar cell was produced.

The substrate (support) has a length of 300 m and a width of 30 c.
A strip-shaped stainless steel sheet having a thickness of 0.1 mm and a thickness of 0.1 mm was used.
FIG. 5 is a schematic view of an apparatus for continuously forming photovoltaic elements using a roll-to-roll method. In this apparatus, a substrate delivery chamber 510, a plurality of deposition chambers 501 to 509, and a substrate winding chamber 511 are sequentially arranged, and a separation passage 51 is provided therebetween.
Each deposition chamber has an exhaust port, and the inside can be evacuated. The strip-shaped substrate 513 is wound up from the substrate delivery chamber to the substrate winding chamber through the deposition chamber and the separation passage. At the same time, gas can be introduced from the gas inlets of the respective deposition chambers and separation passages, and the gas can be exhausted from the respective exhaust ports to form respective layers. In the deposition chamber 501, AlSi (9:
1), a ZnO thin film layer containing silicon in the deposition chamber 502, and a p-layer in the deposition chambers 503 to 508.
For the inpin layer, a transparent electrode made of ITO is formed in the deposition chamber 509.

In each of the deposition chambers, a halogen that heats the substrate from the back is provided.
Lamp heaters 518 are installed inside each deposition chamber.
It is heated to a predetermined temperature. In the deposition chamber 501, DC magnet
Perform the tron sputtering method, and from the gas inlet 526
Ar gas is introduced and the target is AlSi (9: 1)
Is used. RF magnetron sputtering in the deposition chamber 502
A ring method was performed, and Ar gas was introduced.
ZnO containing no silicon is used. In the deposition chamber 509
RF magnetron sputtering is performed, and O _TwoWith gas
Ar gas was introduced and the target was ITO (In)_TwoO_Three+
SnO_Two(5 wt%)).

550 is a top view of the deposition chambers 503 to 508. In the deposition chambers 503 and 508, an MWPCVD method is used. In the deposition chambers 504 and 507, a biased MWPCV is applied.
In the D method and the deposition chambers 505 and 506, the RFPCVD method can be performed. Each deposition chamber has a source gas inlet 514 and an exhaust port 515, an RF electrode 516 or a microwave applicator 517 is attached, and a source gas supply device (not shown) is provided at the source gas inlet 514.
Is connected. A vacuum exhaust pump (not shown) such as an oil diffusion pump or a mechanical booster pump is connected to an exhaust port of each deposition chamber, and a separation passage 5 connected to the deposition chamber.
12 has an inlet 519 through which a scavenging gas flows, and a scavenging gas as shown in the figure is introduced. A bias electrode 531 is arranged in the deposition chambers 503 and 507, which are the i-layer deposition chambers, and an RF power supply (not shown) is connected as a power supply.

Reference numeral 540 is a view of the deposition chamber 502 viewed from the side.
In order to gradually change the silicon content in the layer thickness direction, SiH ₄ gas was used as a scavenging gas introduced into the separation passage between the deposition chamber 502 and the deposition chamber 503. By doing so, part of the SiH ₄ gas flows into the deposition chamber 502, and more silicon is contained in the vicinity 543 of the interface with the pin layer, and gradually decreases toward the interface 541 with the Ag light reflection layer. Such a change in the content is obtained.

The delivery roll 520 is provided in the substrate delivery chamber.
And a guide roller 521 for applying an appropriate tension to the substrate and keeping the substrate horizontal at all times, and a winding roller 522 and a guide roller 523 in the substrate winding chamber.

First, the stainless steel sheet is wound around a delivery roll (average radius of curvature: 30 cm), 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 a vacuum 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. When the pressure of the entire apparatus becomes 1 mTorr or less, a scavenging gas as shown in FIG. 5 is introduced from a scavenging gas inlet 519, and the substrate is taken up by a take-up roll while moving in the direction of the arrow in the figure. Each source gas flows into each deposition chamber. At this time, the flow rate of the 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 is not diffused into another deposition chamber. Next, RF power or MW power is introduced to generate plasma, and respective layers are formed.

An AlSi light reflecting layer (substrate temperature 350 ° C., layer thickness 300 nm) is formed on the substrate in the deposition chamber 501, and a ZnO thin film layer (substrate temperature 350 ° C., layer thickness 60) is formed in the deposition chamber 502.
0 nm), an n1 layer (a-Si: P, layer thickness 20 nm) is formed in the deposition chamber 503, and an i1 layer (a-Si
Ge, layer thickness 180 nm), p1 layer (μc) in the deposition chamber 505
-Si: B, layer thickness 10 nm), n2 layer (μc-Si: P, layer thickness 20 nm) in the deposition chamber 506, i in the deposition chamber 507
2 layers (a-Si, layer thickness 250 nm), p in the deposition chamber 508
2 layers (μc-SiC: B, layer thickness 10 nm), deposition chamber 50
9, transparent electrodes (ITO, layer thickness 75 nm) were sequentially formed.

When the winding of the substrate was completed, all the MW power, RF power, and sputtering power were turned off, the plasma was extinguished, and the inflow of the raw material gas and the scavenging gas was stopped. The entire device was leaked, and the take-up roll was taken out.

Next, a carbon paste having a layer thickness of 5 μm and a line width of 0.5 mm was 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 was printed thereon to form a current collecting electrode. , Roll-shaped solar cell 250 mm x 10
It was cut to a size of 0 mm.

In the above, p using the roll-to-roll method
The fabrication of the inpin type solar cell (SC Ex 7) was completed.

Comparative Example 7 The same conditions as in Example 14 were adopted except that the scavenging gas flowing through the separation passage between the deposition chambers 502 and 503 was changed to Ar gas so that the ZnO thin film layer did not contain silicon. A solar cell (SC ratio 7) was produced.

When the same measurement as in Examples 1 and 2 was performed, it was found that the solar cell (SC Ex. 7) of the present invention had more excellent characteristics than the conventional solar cell (SC ratio 7). Do you get it.

When the crystallinity was evaluated with an X-ray diffractometer in the same manner as in Example 1, it was found that both (SC Ex. 7) and (SC ratio 7) had c-axis orientation. Also, in (SC Ex. 7), the silicon content in the ZnO thin film layer
It was found by SIMS that it had changed as follows.

(SC ratio 7) did not contain silicon. In addition, when (SC Ex. 7) and (SC Comp. 7) wound in a roll were stored in a dark place for 3 months, no delamination was observed in (SC Ex. 7), but in (SC Comp. 7) Slight delamination was observed.

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

[0171]

The photovoltaic device of the present invention has a ZnO / pin
It is possible to suppress recombination of photoexcited carriers near the layer interface and the ZnO / substrate interface, improve the open-circuit voltage and the short-circuit current, and improve the photoelectric conversion efficiency. Further, light deterioration and vibration deterioration of the photovoltaic element can be suppressed. Further, light deterioration, vibration deterioration, and short circuit when a bias voltage is applied to the photovoltaic element can be suppressed. Further, even in a photovoltaic element in which a non-single-crystal silicon-based semiconductor layer containing microcrystalline silicon is formed on a ZnO thin film layer, delamination does not occur. Further, even in a photovoltaic element in which a non-single-crystal silicon-based semiconductor layer containing fluorine is formed on a ZnO thin film layer, delamination does not occur. It does not delaminate even in a rolled state.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of a layer configuration of a photovoltaic element of the present invention.

FIG. 2 is a schematic diagram illustrating an example of a deposition apparatus.

FIG. 3 is a graph showing a change in a silicon content in a thickness direction in a ZnO thin film layer.

FIG. 4 is a schematic view showing another example of the layer configuration of the photovoltaic element of the present invention.

FIG. 5 is a schematic diagram showing an example of a roll-to-roll deposition apparatus.

[Explanation of symbols]

101, 411, 421 substrate, 102, 412, 422 ZnO thin film layer, 103 pin layer, 104, 414, 424 transparent electrode, 105, 415, 425 current collecting electrode, 106, 416, 426 crystal grain boundary, 107, 417, 427 crystal grain, 200 deposition apparatus, 201 deposition chamber, 202 vacuum gauge, 203 bias power supply, 204 substrate, 205 heater, 206 waveguide, 207 conductance valve, 208 valve, 209 target electrode, 210 bias electrode, 211 gas introduction pipe , 212 applicator, 213 dielectric window, 214 sputtering power supply, 215 substrate shutter, 216 target, 217 target shutter, 219 microwave power supply, 220 exhaust port, 221 toroidal coil, 413 pinpin layer, 423 pinpinpin layer, 501, 502, 503, 504, 505, 506, 5
07, 508, 509 deposition chamber, 510 substrate delivery chamber, 511 substrate winding chamber, 512 separation passage, 513 substrate, 514 gas inlet, 515 exhaust port, 516 RF electrode, 517 microwave applicator, 519 scavenging gas inlet, 521 guide Roller, 522 Take-up roll, 523 Guide roller, 526 Gas inlet, 527 Target electrode, 528 target, 529 Toroidal coil, 531 Bias electrode, 541 Interface with Ag light reflecting layer 543 Near interface with pin layer.

Continuation of the front page (56) References JP-A-5-110125 (JP, A) JP-A-62-122011 (JP, A) JP-A-59-224181 (JP, A) JP-A-62-35680 (JP, A) , A) JP-A-59-97515 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (5)

(57) [Claims] 1. A zinc oxide thin film layer and a pin layer (p layer, i layer, n layer) made of a non-single-crystal silicon semiconductor material on a substrate.
Layers), the zinc oxide thin film layer has a surface with irregularities of 0.1 to 1.0 μm,
a crystalline thin film having a c-axis orientation and containing silicon, wherein the silicon content has a minimum value at the interface with the substrate and gradually increases toward the pin layer ;
High content of silicon near the grain boundaries of the zinc oxide thin film layer
Photovoltaic element characterized in that it is. 2. The photovoltaic device according to claim 1, wherein the c-axis is substantially perpendicular to the surface of the base. Wherein the said p-layer or n-layer in contact with the zinc oxide thin film layer, the photovoltaic device according to claim 1 or 2, characterized in that it contains a microcrystalline silicon. 4. A photovoltaic element according to any one of claims 1 to 3, wherein the p-layer or n-layer in contact with the zinc oxide thin film layer is characterized by containing the fluorine. 5. A band-like substrate wherein the substrate having flexibility, the photovoltaic device according to any one of claims 1 to 4, characterized in that can be wound into a roll.