JPH11274539A - Substrate with transparent conductive layer and photovoltaic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high photoelectric conversion photovoltaic element which can be produced at a high yield whereas at a low cost suited for the practical use, and the reliability is high and when used for a photosensor element. SOLUTION: In the substrate having transparent conductive layers each composed of at least one layer laminated on a support substrate, the angle of inclination arctan (df/dx) distribution with a sampling length dx ranging from 20-100 nm is a normal distribution having a kurtosis of -1.2 to 0.5 with center at 0 deg. and the standard deviation is set to 20-55 deg., provided that the distance from the suppont substrate of the transparent coudutive layer is set (f).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate with a transparent conductive layer, and more particularly, to improving the yield and weather resistance and durability in a manufacturing process while improving photoelectric conversion efficiency by an optical confinement effect. The present invention relates to a substrate having a transparent conductive layer and a photovoltaic element using the same. The photovoltaic element is used for a solar cell, a photodiode, an electrophotographic photoreceptor, and the like.

[0002]

2. Description of the Related Art Photovoltaic elements for converting light into electric energy are widely used as solar cells, such as calculators and wristwatches, and are widely used as small power sources for consumer use.
It is attracting attention as a technology that can be put to practical use as a substitute for so-called fossil fuels such as coal. Further, it is used as a sensor for a fax, a scanner, or the like, and is used for an electrophotographic photosensitive drum of a copying machine or the like. The photovoltaic element is
This is a technology that uses the photovoltaic power of a pn junction of a semiconductor and the photoelectric conversion of a semiconductor. The semiconductor, such as silicon, absorbs light to generate photocarriers of electrons and holes, and the photocarriers generate an electric field inside the pn junction. To drift out and take it out.

Heretofore, the most commonly used photovoltaic elements have used single crystal silicon as a material. Such a method of manufacturing a photovoltaic element can be manufactured by using a process substantially similar to a normal semiconductor process. Specifically, a single crystal of silicon whose valence electrons are controlled to p-type or n-type is formed by a crystal growth method such as a CZ method, and the single crystal is sliced to about 300 μm.
Make a silicon wafer of thickness m. Further, a pn junction is formed by forming a different kind of conductive layer on the wafer surface by using a suitable means such as diffusion of a valence electron controlling agent so as to have a conductivity type opposite to the conductivity type of the wafer. is there.

[0004] By the way, such photovoltaic devices using single crystal silicon have high production costs due to the high cost of manufacturing a silicon wafer and the high cost of a manufacturing process due to the use of a semiconductor process. Therefore, the production cost per unit power generation is higher than the existing power generation method, and it is considered that it is difficult to reduce this to a level that can be used for electric power.

Therefore, in promoting the practical use of photovoltaic elements as power, it has been recognized that cost reduction and large area are important technical issues.
The search for materials with high conversion efficiencies has been pursued.

[0006] Materials for such a photovoltaic element include:
A tetrahedral amorphous semiconductor or polycrystalline semiconductor such as amorphous silicon, amorphous silicon germanium or amorphous silicon carbide, or II such as CdS or Cu ₂ S
-VI and III-V compound semiconductors such as GaAs and GaAlAs. In particular, a thin-film photovoltaic element using an amorphous semiconductor or a polycrystalline semiconductor for the photovoltaic generation layer can produce a film having a larger area than a photovoltaic element using single-crystal silicon. It has advantages such as being thin and being able to be deposited on an arbitrary supporting substrate material, and is considered promising.

However, the above-mentioned thin-film photovoltaic element does not have the photoelectric conversion efficiency equivalent to that of a photovoltaic element using single-crystal silicon. Improvement and reliability improvement were issues to consider.

Therefore, various methods have been studied as means for improving the photoelectric conversion efficiency of the thin-film photovoltaic device.

One of the important issues for improving the photoelectric conversion efficiency of a thin-film photovoltaic device is to increase light absorption in a thin-film semiconductor layer and increase short-circuit current (Jsc). This is because if the semiconductor layer is thinned for cost reduction, light absorption is reduced as compared with a bulk semiconductor. Several techniques have been studied as techniques for increasing light absorption in a thin film semiconductor layer.

As one of the techniques, there is a technique of forming a reflection layer (also a back electrode) made of a metal film having high reflectivity such as Ag, Al, Cu, Au, etc., opposite to the light incident side of the photovoltaic element. Are known. In this technology, light transmitted through a semiconductor layer that generates carriers is reflected by a reflective layer, and then absorbed by the semiconductor layer again, light absorption in the thin film semiconductor layer is increased, and output current is increased to increase the photoelectric current. This is to improve the conversion efficiency.

On the other hand, a method for improving the surface properties of a substrate by interposing a transparent conductive thin film between a back electrode and a semiconductor layer is disclosed in Japanese Patent Publication Nos.
No. 41878. In these publications, as the effect of interposing a transparent conductive thin film between the back electrode and the semiconductor layer, improvement in flatness of the back electrode,
Alternatively, improvement of the adhesion of the semiconductor layer, prevention of alloying of the metal of the back surface electrode and the semiconductor layer, and the like are mentioned.

Japanese Patent Application Laid-Open No. 60-84888 discloses a technique for reducing a current flowing in a defect region of a semiconductor layer by interposing a transparent conductive thin film as a barrier layer between the back electrode and the semiconductor layer. Is disclosed.

[0013] Further, it has been found that the spectral sensitivity in the long wavelength region is increased by interposing a transparent conductive thin film made of TiO ₂ between the back electrode of Ag and the amorphous silicon semiconductor layer. Phys. Let
t. , 43 (1983) p644 (Y. Hamakaw).
a, et. al).

Further, by making the shape of the back electrode into an uneven shape (texture structure) having a size approximately equal to the wavelength of light, long-wavelength light that could not be absorbed by the semiconductor layer is scattered and an optical path in the semiconductor layer is scattered. A technology for increasing the length of the photovoltaic element, improving the long-wavelength sensitivity of the photovoltaic element, increasing the short-circuit current, and improving the photoelectric conversion efficiency is disclosed in Proc. 16th ・ IEEE ・
Photovoltaic ・ Specialist ・ C
onf. (1982) p1423 (T. Tiedje,
et. al) and Proc. 16th ・ IEEE ・
Photovoltaic ・ Specialist ・ C
onf. (1982) p1425 (H. Deckma
n, et. al).

By synthesizing the above techniques, a metal film having a concave-convex shape having a size approximately equal to the wavelength of light that scatters light and a high reflectivity is formed as a back surface reflection layer also serving as a back surface electrode. A configuration in which a transparent conductive thin film is interposed between the reflective layer and the semiconductor layer is considered to be most suitable for a photovoltaic element.

However, when a photovoltaic element is actually manufactured by employing the back electrode having such a configuration, there are some problems in view of workability and durability.

Conventionally, a typical uneven structure called a so-called texture structure, for example, the T.P. Tiedje, e
t. It has been considered that a material having pyramid-shaped irregularities as shown in FIG. However, it is necessary to further examine what shape is optimal for improving efficiency and yield, and improving workability in a post-process.

First, in a semiconductor layer formed on a surface having pyramid-shaped irregularities having steep vertices or valleys,
Stress is locally generated at the top of the pyramid, and a defective portion is easily generated in the semiconductor layer. Also, when an electromotive force is generated, the electric field is concentrated on the top of the pyramid, so that the leak current of the photovoltaic element increases through a defective portion of the semiconductor layer, etc., and the production yield of the photovoltaic element decreases. There is.

In particular, when the semiconductor layer is deposited at a high speed (for example, at a deposition rate of 10 ° / s or more), the deposition of the film tends to be non-uniform. Peeling of the film may be observed.

Further, the semiconductor layer formed on the surface having pyramid-shaped irregularities having uniformly steep vertices or valleys has a stronger electric field at the top of the pyramid than the semiconductor layer formed on the flat surface. In addition, due to the non-uniformity of the electric field, the open voltage (Voc) and the fill factor (FF) of the photovoltaic element may be lower than those of the photovoltaic element formed on the flat support substrate surface.

Furthermore, photodeterioration of the photovoltaic element may be increased (deterioration of element characteristics due to long-time light irradiation) and vibration deterioration (deterioration of element characteristics due to long-time application of vibration) may be observed. 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. Further, it is considered that vibration degradation of the photovoltaic element breaks a weak bond due to vibration energy, and this becomes a recombination center of photoexcited carriers, thereby deteriorating element characteristics.
This weak bond is considered to be localized in a region where stress is generated.

When a semiconductor layer is deposited at a high speed, a pinhole is particularly likely to be formed. When the conductivity of the transparent conductive layer is high, a short circuit may occur in the semiconductor layer.

For example, when Ag or Cu is used as the back metal reflection layer, when the humidity is high and a positive bias voltage is applied to the back metal reflection layer, Ag or Cu migrates and the light incidence side And the photovoltaic element was shunted (short-circuited).

On the other hand, when the transparent conductive layer is formed flat, there is a problem that light is not sufficiently absorbed in the semiconductor layer due to little scattering of light on the back surface, and depending on a combination of materials of the support substrate and the back electrode. There has been a problem that the adhesion between the support substrate and the backside reflective layer is insufficient, and peeling may occur between the transparent conductive layer and the semiconductor layer in the process of processing the photovoltaic element.

In the subsequent step of removing the electrical short circuit at the defective portion, if the surface has sharp irregularities, the reaction may progress too much at the top of the steep pyramid, and damage may be caused to a portion where no defect exists. . Therefore, in such a substrate, the range of setting conditions in the step of removing the electrical short circuit at the defective portion is narrowed. This requires strict control of the process and reduces productivity.

In the subsequent step of removing the electrical short circuit at the defective portion, if the transparent conductive layer film has low corrosion resistance, the transparent conductive film is etched through the pinhole, and conversely, the film is peeled off or a short circuit is induced. In some cases, the reliability may be impaired.

[0027]

The problems described above are caused by using a low-cost support substrate such as a resin film or stainless steel, or increasing the production speed by increasing the formation speed of a semiconductor layer. In particular, when a low-cost manufacturing process suitable for a photovoltaic element is adopted, the yield is reduced in the production of the photovoltaic element.

An object of the present invention is to solve the problems of workability, yield, and durability as described above and to increase the light absorption of the semiconductor layer by making the back reflection layer a specific structure. Another object of the present invention is to provide a photovoltaic element and a substrate with a transparent conductive layer that can be produced at a high yield, have high reliability, and have high photoelectric conversion efficiency, at low cost suitable for practical use.

[0029]

As a result of studying these problems, the present inventor has found that, when the distance from the supporting substrate surface is f, the inclination angle arctan (df) when the sampling length dx is in the range of 20 nm to 100 nm. The inventors have found that the above problem can be solved by forming a transparent conductive layer having a specific distribution of / dx), and have completed the present invention.
Here, the support substrate surface is not a real support substrate surface (which may have irregularities), but a virtual plane obtained by removing irregularities from the actual support substrate surface.

That is, in the present invention, in a substrate with a transparent conductive layer in which at least one transparent conductive layer is laminated on a support substrate, sampling is performed when the distance of the surface of the transparent conductive layer from the support substrate surface is f. Length dx is 20 nm to 10
The tilt angle arctan (df / d) in the range of 0 nm
The distribution of x) has a kurtosis of −1.2 to 0.5 centered on 0 °.
A substrate with a transparent conductive layer and a photovoltaic element using the substrate, wherein the substrate has a normal distribution of 20 ° to 55 °.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a photovoltaic device using a substrate with a transparent conductive layer according to the present invention. FIG. 1 (a)
(B) is a schematic sectional view showing one example of the photovoltaic element of the present invention. In FIG. 1A, reference numeral 101 denotes a support substrate. The transparent conductive layer 102 and the n-type semiconductor layer 10
3. The i-type semiconductor layer 104, the p-type semiconductor layer 105, the transparent electrode 106, and the current collecting electrode 107 are stacked. FIG.
As shown in (b), the support substrate 101 and the transparent conductive layer 10
2 may have a metal layer 108. This is an example, and the present invention is not limited to this configuration.

First, each layer of the substrate with a transparent conductive layer of the present invention will be described in detail.

(Transparent conductive layer 102) Semiconductor layers 103-1
In the case of a photovoltaic element in which light is incident on the semiconductor substrate 103 from the support substrate 101 side, the transparent conductive layer 102 is disposed on the surface of the semiconductor layers 103 to 105 in the light incident direction, transmits the incident light, At the same time, it also has a role of making light incident on the semiconductor layers 103 to 105 after being irregularly reflected and a role of a surface electrode of the photovoltaic element. Conversely, in the case of a photovoltaic element in which light enters from the transparent electrode 106 side, the transparent conductive layer 102 has a role as a light confinement layer and a reflection increasing layer.

It is desirable that the material of the transparent conductive layer is high in transmittance, has appropriate conductivity, and is inexpensive. In ₂ O ₃ ,
SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), ZnO, Cd
O, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂ O ₃ , M
Conductive oxides such as oO ₃ and Na _x WO ₃ , or a mixture thereof, or a compound obtained by adding a dopant to these compounds can be used.

Among them, aluminum, zinc, tin,
It is particularly preferable that it be made of at least one selected from oxides or nitrides of indium, titanium and tantalum and composite compounds thereof.

The conductivity of the transparent conductive layer is 10 ⁻⁸ (1 / Ωc).
m) to 10 ⁻² (1 / Ωcm) is preferable, and 10 ⁻⁷ (1 / Ωcm) is preferable.
Ωcm) to 10 ^-3 (1 / Ωcm) is more preferable. When the transparent conductive layer has an appropriate electrical conductivity, even if a pinhole is generated in the semiconductor layers 103 to 105 and an electrical short circuit occurs, the semiconductor layer 103 to 105 has resistance to such an extent that the characteristics do not deteriorate. it is conceivable that.

It is preferable to add a corrosion resistance improving material, that is, an impurity which increases corrosion resistance to the transparent conductive layer. By adding the corrosion resistance improving material, in a process of removing a defect in a later process, a wide range of conditions can be set in a process of removing an electrical short circuit of a defective portion, and the degree of recovery is good.
When the defects are removed, the transparent conductive layer is prevented from being melted, and the defects are prevented from being spread or generated.

Such additives vary depending on the material of the transparent conductive layer. For example, in the case of zinc oxide, copper or chromium is used, and in the case of tin oxide, aluminum or the like is preferable.

The method of forming the transparent conductive layer depends on the material of the transparent conductive layer, but the following method can be employed.

As a method of forming the transparent conductive layer, there are microwave plasma CVD method, RF plasma CVD method, optical CVD
It can be obtained by various CVD methods such as a thermal CVD method, an MOCVD method, various vapor deposition methods such as EB vapor deposition, sputter vapor deposition, MBE, ion plating, and ion beam, or a plating method and a printing method.

In the following, as an example, Z
A procedure for forming a transparent conductive layer made of nO will be described, but the present invention is not limited to this.

In the deposition of the transparent conductive layer, Xe, O ₂ and F ₂
Is used. By adjusting the addition amount of F _2, easily control the surface shape. This addition amount is 1% to 10%
Is desirable. The addition amount of F ₂ is no increase in the inclination angle by competition deposition inhibitory effect equal to or less than 10%, preferably not be a film if powdery not less than 1%.

The formation temperature is also an important factor, and a temperature range of approximately 200 ° C. to 300 ° C. is desirable without increasing the tilt angle. It is better that the deposition rate is relatively high.
Å / s to 100Å / s is desirable. The deposition pressure depends on the type of gas and the deposition equipment, but a relatively low pressure is better.
1 mTorr to 10 mTorr is preferred.

It is also effective to separately etch with an acid, an alkali or the like. As the acid, formic acid, acetic acid, sulfuric acid, hydrochloric acid, nitric acid and the like can be used. As the alkali, potassium hydroxide, sodium hydroxide, aluminum hydroxide and the like can be used. As the salt, iron chloride, aluminum chloride, aluminum sulfate and the like can be used. The time of immersion in the etchant is a very important factor, and the mixture of acetic acid and a salt such as aluminum sulfate can be controlled relatively stably. The temperature is a very important control parameter and depends on the concentration of the etchant, but the lower the temperature, the better the controllability.

In the present invention, the distribution of the inclination angle arctan (df / dx) at the sampling length dx is centered at 0 ° when the distance of the transparent conductive layer from the surface of the supporting substrate is f. It is a normal distribution with a kurtosis of -1.2 to 0.5, and the standard deviation is 20 ° to 55 °. Here, the support substrate surface is not a real support substrate surface (which may have irregularities), but is a virtual plane obtained by removing irregularities from the actual support substrate surface.

FIG. 2A is a conceptual diagram of the surface shape of the transparent conductive layer. By observing the surface of the transparent conductive layer with, for example, a probe microscope, and obtaining the inclination angle arctan (df / dx) from the surface inclination df / dx at an arbitrary sampling length dx, the distribution of the inclination angle can be obtained.

The distribution of the inclination angle shows a normal distribution centered on 0 °, and it is preferable that the distribution is not deviated to a certain angle.

The kurtosis representing the deviation from the normal distribution is expressed by the following equation. If the kurtosis is positive, the distribution is relatively acute, and if the kurtosis is negative, the distribution is flat.

[0049]

(Equation 1)

The kurtosis is -1.2 to 0.5, preferably-
It is 1.0-0.3, more preferably -0.7-0.2. When the thickness is within this range, there is an optical path length passing through the semiconductor layers 103 to 105, and there is an effect of canceling interference, which is preferable.

The standard deviation of the distribution of the inclination angle is 20 ° to 55 °
, Preferably 25 ° to 50 °, more preferably 30 ° to 45 °.

Within this range, the semiconductor layers 103 to 1
The light path length passing through 05 extends, and the light that passes through the transparent conductive layer 102 and is reflected by the support substrate 101 or the metal layer 108 is partially multiple-reflected, and the interference in the transparent conductive layer 102 is cancelled. It is preferable because there is no problem in that defects of the semiconductor layers 103 to 105 occur and the film thickness becomes too small to be effective in increasing the short-circuit photocurrent.

FIG. 2B is a conceptual diagram of local valleys and peaks in the surface shape of the transparent conductive layer. The angle formed by the local valley in the cross-sectional shape of the surface of the transparent conductive layer (ψ in the figure) )
Average value is preferably 170 ° to 110 °, more preferably 160 ° to 120 °, and still more preferably 150 ° to
130 °. Within this range, a semiconductor layer is not easily deposited on the transparent conductive layer, and no defect is caused by a reduction in the layer thickness, which is preferable. Especially when the deposition rate is 10Å
At more than / s, the adhesion of the semiconductor layer tends to be non-uniform, which is effective.

The average value of the angle (ψ in the figure) formed by local peaks in the cross-sectional shape of the surface of the transparent conductive layer is preferably 17
0 ° to 100 °, more preferably 160 ° to 110 °,
More preferably, it is 150 ° to 120 °. Within this range, stress is preferably generated in the semiconductor layer on the transparent conductive layer without causing a defect due to cracking of the semiconductor layer. In particular, when the deposition rate is 10 ° / s or more, the adhesion of the semiconductor layer tends to be uneven, which is effective.

The sampling length dx is preferably about 1/3 to 1/10 of the wavelength of light to be converted into an electric signal by the photovoltaic element. If the purpose is generally in the range of ultraviolet light, visible light, and near-infrared light, the wavelength is preferably 20 nm to 100 nm. When the sampling length is 20 nm or more, the inclination due to unevenness that does not contribute to the increase in short-circuit photocurrent is preferably measured. When the thickness is 100 nm or less, the pitch is close to the pitch of the unevenness, and there is no problem that unevenness with respect to a wavelength contributing to an increase in light absorption cannot be measured accurately, which is preferable.

When the transparent conductive layer has the above surface, the following effects can be obtained.

Since the light has a suitable angle distribution for the desired light reflection, the light path length of the light reflected on the back surface of the photovoltaic element is extended, and the light is reflected in various directions. And the short-circuit photocurrent of the photovoltaic element increases, thereby improving the photoelectric conversion efficiency.

The adhesion between the thin film (typically, a semiconductor layer) laminated on the transparent conductive layer and the transparent conductive layer is improved, and the transparent conductive layer is laminated on the transparent conductive layer in the manufacturing process of the photovoltaic element. It does not peel off from the thin film to be formed, so that the controllability and the degree of freedom of the manufacturing process are improved, and the yield of the manufacturing process of the photovoltaic element is improved. Also, the weather resistance is improved.

The series resistance of the photovoltaic element decreases,
The fill factor is improved, and the photoelectric conversion efficiency is improved.
Although the principle on which the series resistance is reduced is not clear, it is considered that the adhesion between the thin film laminated on the transparent conductive layer and the transparent conductive layer is improved.

The leak current of the photovoltaic element is reduced, and the production yield of the photovoltaic element is improved. Further, while maintaining the short-circuit photocurrent of the photovoltaic element at a high value, the open-circuit voltage and the fill factor are improved, and the photoelectric conversion efficiency is improved. That is, since there is no sharp valley portion and poor adhesion of the film does not easily occur, and since there is no sharp peak portion and cracks due to the stress of the film do not easily occur, high short-circuit due to light scattering is caused. While maintaining the photocurrent, the open voltage and the fill factor are improved, and the photoelectric conversion efficiency is improved.

Further, since defects due to local valleys and local peaks of the film stacked on the upper portion are reduced, photodegradation of the photovoltaic element (decrease in photoelectric conversion efficiency due to long-time light irradiation) and vibration degradation ( Reduction of photoelectric conversion efficiency due to long-time vibration application)
Is controlled.

In the subsequent step of removing defects, in the photovoltaic element using the substrate with a transparent conductive layer of the present invention, a wide range of conditions can be set in the step of removing the electrical short circuit at the defective portion, and the recovery is improved. Is also good. Conventionally, a portion of the defective portion from which the electrical short was removed was sometimes marked as a mark that could be visually confirmed. However, in the photovoltaic device using the substrate with a transparent conductive layer of the present invention, the mark was visually confirmed. Can not. This effect is also due to the fact that stress due to local valleys and local peaks of the film stacked on the top is reduced, and there is no place where the tilt angle is locally large and the film is thin, so there is no defect. This is because the reaction where no reaction is made does not proceed locally, and damage is less likely to occur.
In addition, since the stress in the defective part is reduced and there are no large defects such as cracks and cavities, secondary defects are suppressed even in the part where the electric short circuit of the defective part has been removed and confirmed visually. There is no trace that can be done.

Hereinafter, an experiment conducted by the present inventor on the above-described shape of the transparent conductive layer will be described.

(Experiment 1) A transparent conductive layer was formed under the following conditions, the surface was observed with a probe microscope, and the slope df / dx of the cross-sectional shape of the surface at a sampling length of 40 nm.
The inclination angle arctan (df / dx) was obtained from the above, and the distribution of the inclination angle was obtained.

Samples m1 to m2 ZnO (9
9.999%) and Xe, O_Two, F_TwoFor
Yes, F_Two1% (ml), 5% (m 2)
did. The substrate temperature is 200 ° C., the deposition pressure is 3 mTorr,
The deposition rate was 20 ° / s.

Sample m3 ZnO (9) was used as a target by DC magnetron sputtering.
9.999%), Ar is used as a gas type, the substrate temperature is 200 ° C., the deposition pressure is 10 mTorr, and the deposition rate is 2
0 ° / s.

Sample m4 ZnO (9) was used as a target by DC magnetron sputtering.
9.999%), Ar is used as a gas type, the substrate temperature is 200 ° C., the deposition pressure is 10 mTorr, and the deposition rate is 2
0 ° / s. 1% acetic acid + 1 aluminum sulfate
The temperature was adjusted to 20 ° C. with a 30% aqueous solution for 30 seconds.

Sample m5 ZnO (9) was used as a target by DC magnetron sputtering.
9.999%), Ar is used as a gas type, the substrate temperature is 200 ° C., the deposition pressure is 10 mTorr, and the deposition rate is 2
0 ° / s. It was heated to a temperature of 3% with 0.5% aqueous sulfuric acid.
The sample was kept at 0 ° C. for 20 seconds.

Sample m6 Prepared by an electrodeposition method. Aqueous solution is 85 ℃, 0.05mol
/ L of zinc nitrate and 0.01 g of dextrin as an additive
/ L, and 4-N zinc having a thickness of 1 mm was used as a counter electrode. The aqueous solution was an aqueous solution of zinc acetate, and the applied current was 1.0
mA / cm ² (0.1 A / dm ² ).

FIG. 5 shows the distribution of the inclination angle. Table 1 shows the standard deviation and the kurtosis of each inclination angle.

[0071]

[Table 1]

(Experiment 2) A sample was prepared in the same manner as in Experiment 1,
Assuming that the sampling length is 20 nm, the distribution of the inclination angle was obtained. FIG. 7 shows the relationship between the standard deviation of the distribution of the inclination angle and the short-circuit photocurrent, and FIG. 6 shows the relationship between the center line average roughness Ra and the short-circuit photocurrent. As shown in FIGS. 6 and 7, the center line average roughness Ra and the short-circuit photocurrent do not match when Ra is large,
The correlation was observed with the standard deviation of the distribution of the inclination angle until the element stopped functioning due to the occurrence of a defect or the like.

(Experiment 3) A film thickness of 1 μm and a conductivity of 10 ⁻⁴ (1 / Ωc) were formed on a supporting substrate (SUS304) by magnetron sputtering under various conditions in the same manner as in Experiment 1.
m) A transparent conductive layer made of a zinc oxide thin film was prepared. Further, a pin amorphous silicon semiconductor solar cell was stacked as a semiconductor layer as in Example 1, and the efficiency of the solar cell was measured in the same manner as in Example 1.

The surface shape of the transparent conductive layer and the characteristics of the device were compared. The evaluation was performed by changing the sampling length from 10 nm to 150 nm. FIG. 8 shows the relationship between the standard deviation of the distribution of the inclination angle and the short-circuit photocurrent using the sampling length as a parameter.
FIG. 8 shows that there was a correlation between the two at a sampling length of 20 nm to 100 nm.

(Metal layer 108) When the support substrate 101 is a non-translucent substrate, if the reflectance of the support substrate is insufficient, the metal layer is formed of the support substrate 101 and the transparent conductive layer 102.
It is desirable to provide between them.

The metal layer converts the long-wavelength light that could not be absorbed by the semiconductor layers 103 to 105 again into the semiconductor layers 103 to 105.
To increase the optical path length in the semiconductor layers 103 to 105 to increase the light absorption of the semiconductor layers 103 to 105, thereby increasing the short-circuit current (Jsc) of the photovoltaic element.

The metal layer has an inclination angle arctan (dfm / dx) when the sampling length dx is in the range of 20 nm to 100 nm, where fm is the distance between the surface in contact with the transparent conductive layer and the support substrate surface (the virtual plane as described above). ) Is a normal distribution with a kurtosis of −1.0 to 0.5 centered on 0 °, and the standard deviation is preferably 5 ° to 20 °.

The surface of the metal layer is observed with, for example, a probe microscope, and at an arbitrary sampling length dx, the inclination angle arctan (dfm / dx) is calculated from the surface inclination dfm / dx.
Is obtained, the distribution of the inclination angle can be obtained.

The kurtosis is more preferably -0.8 to 0.5.
4, more preferably -0.6 to 0.3. Further, the standard deviation is more preferably 7 ° to 17 °, further preferably 7 ° to 15 °.

Within this range, the absorption of light on the metal surface does not increase and the reflectance does not decrease, and the contact area with the transparent conductive layer 102 decreases due to the small surface area of the metal layer. This is preferable because reactions such as diffusion of metal atoms into the transparent conductive layer 102 hardly occur. In addition, exposure of the metal layer can be prevented when the transparent conductive layer 102 is stacked, which is preferable because an electrical short circuit of the semiconductor layers 103 to 105 is not caused. Further, there are not many places where the film thickness of the transparent conductive layer 102 is thin or there is no place at all, and in a step of removing a defect in a later step, a range of setting conditions in a step of removing an electrical short circuit of a defective portion is wide. It has good recovery and good recovery.

The main material of the metal layer has a high reflectance,
It is preferable to use a material that does not easily diffuse into the transparent conductive layer 102. Specific examples include metals such as gold, silver, copper, aluminum, magnesium, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel.
In particular, it is desirably made of at least one selected from gold, silver, copper, aluminum, magnesium and alloys thereof.

For the formation of the metal layer, various evaporation methods such as EB evaporation and sputter evaporation, various CVD methods, plating methods, printing methods, and the like are used.

As an example of the film forming method, a sputtering method is given. FIG. 3 shows an example of a sputtering apparatus.

FIG. 3 is a schematic sectional view showing an example of an apparatus capable of performing the DC magnetron sputtering method.
1 is a cylindrical deposition chamber, 302 is a substrate holder, 303 is a substrate, 304 is a heater, 305 is a matching box, 306 is an RF power source, 307 is a metal target for a metal layer, 310 is a DC power source, 311 is an RF power source, Reference numeral 312 denotes a DC power supply, reference numerals 313 to 315 denote shutters, reference numeral 316 denotes an exhaust pipe, reference numeral 317 denotes a gas introduction pipe, reference numeral 318 denotes a rotating shaft, and reference numeral 319 denotes a plasma. In addition, although not shown, there are a gas supply device connected to the gas introduction pipe 317 and a vacuum pump connected to the exhaust pipe 316. Further, reference numeral 320 denotes an arrow indicating a gas introduction direction, and 321 denotes an arrow indicating an exhaust direction.

First, the substrate 303 washed with acid and organic is washed.
Is mounted on a disk-shaped substrate holder 302, and a rotation shaft 318, which is the central axis of the disk-shaped substrate holder 302, is rotated. The inside of the deposition chamber 301 is evacuated to 10 ⁻⁶ Torr using an oil diffusion pump / rotary pump (not shown), and Ar, O ₂ , and HF are introduced from a gas introduction pipe 317.
RF power is introduced from the RF power supply 306 into the inside of the deposition chamber 301 to generate an Ar plasma 319. Adjust the matching box 305 to minimize reflected power. At this time, the substrate 303 is sputter-etched to have a more clean surface.

Next, the heater 304 is set to a temperature at which the metal layer is formed. When the temperature reaches a predetermined temperature, a DC power source 310 is turned on to generate Ar plasma, and the shutter 31 is turned on.
When the metal layer 3 is opened and a predetermined thickness is formed, the shutter 313 is closed and the DC power supply 310 is turned off. During deposition,
Temperature and pressure are controlled by a predetermined pattern. When a predetermined thickness is formed, close the shutter and
Turn off the RF power supply 306.

In addition to the apparatus shown in FIG.
The metal layer can be formed by a roll type device.

The deposition conditions are not particularly limited.
Mixing oxygen in an amount of 0.1% to 1% is preferable because a desired inclination angle can be stably obtained. Further, the substrate temperature is set to 20 ° C. to 10 ° C.
When the temperature is set to 0 ° C., the inclination angle of the metal surface is moderate, which is preferable.

The following is an experimental example of deposition conditions.

An Al target having a diameter of 6 inches was used.
Polished stainless steel plate (SUS304) 50mm
A substrate having a size of 50 mm and a thickness of 0.8 mm was used. The pressure was maintained at 20 mTorr while flowing 50 sccm of Ar with the distance between the targets being 70 mm. When a DC voltage of 300 V was applied, plasma was generated, and a current of 2 A flowed.

As shown in Table 2, the oxygen content was 0.1% to 1%.
%, It is easy to stably obtain a desired inclination angle.
Further, the substrate temperature is set to 20 ° C., 100 ° C., 200 ° C., 300 ° C.
° C, but as shown in Table 2, the higher the temperature, the larger the inclination angle of the metal surface. The same tendency was found in other metals.

[0092]

[Table 2] 所 定 A predetermined inclination angle is obtained. ○ Occasionally obtained but unstable. × Desired tilt angle cannot be obtained.

(Supporting substrate 101) Semiconductor layers 103 to 10
5 is a thin film having a thickness of at most about 1 μm and is deposited on a suitable supporting substrate. Such a support substrate may be a single-crystal or non-single-crystal substrate, and may be a conductive substrate or an electrically insulating substrate. Furthermore, they may be translucent or non-translucent, but may be modified,
It is preferable that the material has little distortion and a desired strength.

Specifically, Fe, Ni, Cr, Al, M
o, Au, Nb, Ta, V, Ti, Pt, Pb and other metals or alloys thereof, for example, brass, stainless steel and other thin plates and composites thereof, and polyester, polyethylene,
Film or sheet of heat-resistant synthetic resin such as polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, epoxy, etc. and their composite with glass fiber, carbon fiber, boron fiber, metal fiber, etc. A thin metal film of different materials and / or Si
Examples thereof include those obtained by subjecting an insulating thin film such as O ₂ , Si ₃ N ₄ , Al ₂ O ₃ , and AlN to a surface coating treatment by a sputtering method, a vapor deposition method, a plating method, or the like, glass, ceramics, and the like.

When the support substrate is electrically conductive such as a metal, it may be used as an electrode for direct current extraction. When the support substrate is electrically insulating such as a synthetic resin or the like, the surface on which the deposited film is formed is formed. Al, Ag, Pt, Au, Ni, Ti, M
o, W, Fe, V, Cr, Cu, stainless steel, brass, nichrome, SnO ₂ , In ₂ O ₃ , ZnO, so-called metal simple substance or alloy, and transparent conductive oxide (TCO) are plated and deposited. It is preferable that a surface treatment is performed in advance by a method such as sputtering to form an electrode for extracting current.

Of course, even if the support substrate is made of an electrically conductive material such as metal, the reflectance of long-wavelength light on the surface of the support substrate can be improved, or the structure between the support substrate material and the deposited film can be improved. For the purpose of preventing mutual diffusion of elements, a different kind of metal thin film or the like may be provided on the support substrate on the side where the deposited film is formed. In the case where the support substrate is relatively transparent and a photovoltaic element having a layer configuration in which light enters from the support substrate side is used, the conductive thin film such as the transparent conductive oxide or the metal thin film may be used. Is desirably formed in advance.

It is desirable that these materials be used as a supporting substrate in the form of a sheet or a roll formed by winding a belt-like sheet around a cylindrical body. In the case where a thin film is formed on a base to be a support substrate, the thin film is formed by a vacuum evaporation method, a sputtering method, a screen printing method, a dipping method, a plasma CVD method, or the like.

The smoothness of the surface of the support substrate is preferably such that the surface roughness Ra is 5.0 μm or less. In addition, the surface of the support substrate may be appropriately etched using an acidic solution such as HNO ₃ , HF, HCL, or H ₂ O ₄ to form unevenness.

When the supporting substrate is required to have flexibility,
The thickness can be made as thin as possible within a range where the function as a support is sufficiently exhibited. However, the thickness is usually 10 μm or more from the viewpoints of production, handling, mechanical strength, and the like of the support substrate.

Next, the respective layers of the photovoltaic element using the substrate with a transparent conductive layer of the present invention will be described in detail in the order of formation.

(Semiconductor Layers 103 to 105) The material of the semiconductor layer used in the present invention is, for example, I, such as Si, C, or Ge.
Those using group V elements, or SiGe, SiC, S
using a group IV alloy such as iSn, or CdS,
Those using II-VI group elements such as CdTe, or CuInSe ₂ , Cu (InGa) Se ₂ , CuInS ₂
And the like using an I-III-VI group ₂ element.

Among the above semiconductor materials, semiconductor materials particularly preferably used for the photovoltaic device of the present invention include a-Si: H (abbreviation for hydrogenated amorphous silicon) and a
-Si: F, a-Si: H: F, a-SiGe: H, a
-SiGe: F, a-SiGe: H: F, a-SiC:
Group IV and group IV alloy-based amorphous semiconductor materials such as H, a-SiC: F, and a-SiC: H: F, microcrystalline semiconductor materials, or polycrystalline semiconductor materials are given.

The semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a raw material compound containing an element serving as a valence electron controlling or forbidden band width controlling agent when forming a semiconductor layer is used alone, or mixed with the deposited film forming raw material gas or the diluent gas to form a film forming space. It should be introduced inside.

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

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

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

(1) i-type Semiconductor Layer (Intrinsic Semiconductor Layer) In particular, in a photovoltaic device using a group IV or group IV alloy-based amorphous semiconductor material, the i-type layer used for the pin junction is exposed to irradiation light. It is an important layer for generating and transporting carriers.

As the i-type layer, a slightly p-type or slightly n-type layer can be used.

As described above, the group IV and group IV alloy-based non-single-crystal semiconductor materials contain hydrogen atoms (H, D) or halogen atoms (X), which have an important function.

The hydrogen atoms (H, D) and the halogen atoms (X) contained in the i-type layer work to compensate for dangling bonds of the i-type layer, and the carriers of the i-type layer It improves the product of mobility and life. The p-type layer /
It works to compensate for the interface state of each interface of the i-type layer and the n-type layer / i-type layer, and has an effect of improving the photovoltaic power, the photocurrent and the photoresponsiveness of the photovoltaic element. Hydrogen atoms and / or halogen atoms contained in the i-type layer are 1 to 40a.
t% is mentioned as the optimal content. In particular, the p-type layer / i
A preferred distribution form includes a large distribution of hydrogen atoms and / or halogen atoms at each interface side of the n-type layer and the n-type layer / i-type layer, and the hydrogen atoms and / or and / or The preferred range of the halogen atom content is 1.1 to 2 times the content in the bulk. Further, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed in accordance with the content of silicon atoms.

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

Amorphous silicon and amorphous silicon germanium are converted to a by an element for compensating for dangling bonds.
-Si: H, a-Si: F, a-Si: H: F, a-S
iGe: H, a-SiGe: F, a-SiGe: H: F
And so on.

Furthermore, i suitable for the photovoltaic device of the present invention
As the characteristics of the semiconductor layer, the content of hydrogen atoms is (C
H): 1.0-25.0%, AM1.5, 100 mW
/ Cm ² under similar sunlight irradiation.
0 × 10 ⁻⁷ S / cm or more, dark conductivity (σd) is 1.0 ×
10 ^-9 S / cm or less, Urbach energy by the constant photocurrent method (CPM) is 55 me
V or less, and those having a localized level density of 10 ¹⁷ / cm ³ or less are suitably used.

(2) P-type semiconductor layer or n-type semiconductor layer As an amorphous material (denoted as a-) or a microcrystalline material (denoted as μc-) of a p-type semiconductor layer or an n-type semiconductor layer, For example, a-Si: H, a-Si: HX, a-S
iC: H, a-SiC: HX, a-SiGe: H, a-
SiGe: HX, a-SiGeC: H, a-SiGe
C: HX, a-SiO: H, a-SiO: HX, a-S
iN: H, a-SiN: HX, a-SiON: H, a-
SiON: HX, a-SiOCN: H, a-SiOC
N: HX, μc-Si: H, μc-Si: HX, μc −
SiC: H, μc-SiC: HX, μc-SiO: H,
μc-SiO: HX, μc-SiN: H, μc-Si
N: HX, μc-SiGeC: H, μc-SiGeC:
HX, μc-SiON: H, μc-SiON: HX, μ
c-SiOCN: H, μc-SiOCN: HX, etc., a p-type valence electron controlling agent (Group III atoms B, Al, G
a, In, Tl) and n-type valence electron controlling agents (Periodic Table V
Materials to which group atoms P, As, Sb, and Bi) are added at a high concentration.

Examples of the polycrystalline material (denoted as poly-) include poly-Si: H and poly-Si: H
X, poly-SiC: H, poly-SiC: HX,
poly-SiO: H, poly-SiO: HX, po
ly-SiN: H, poly-SiN: HX, poly
-SiGeC: H, poly-SiGeC: HX, po
ly-SiON: H, poly-SiON: HX, po
ly-SiOCN: H, poly-SiOCN: HX,
poly-Si, poly-SiC, poly-Si
O, poly-SiN, etc., p-type valence electron control agents (Group III atoms B, Al, Ga, In, Tl in the periodic table) and n-type valence electron control agents (Group V atoms P, P in the periodic table) As, Sb,
A material to which Bi) is added at a high concentration is exemplified.

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

The addition amount of Group III atoms of the periodic table to the p-type layer and the addition amount of Group V atoms of the periodic table to the n-type layer are 0.
1-50 atm% is suitable.

Further, hydrogen atoms (H, D) or halogen atoms contained in the p-type layer or the n-type layer work to compensate for dangling bonds of the p-type layer or the n-type layer, and This is to improve the doping efficiency of the layer. The addition amount of hydrogen atoms or halogen atoms added to the p-type layer or the n-type layer is preferably 0.1 to 40 atm%. In particular, when the p-type layer or the n-type layer is crystalline, the content of hydrogen atoms or halogen atoms is preferably 0.1 to 8 atm%. Furthermore, the p-type layer /
At each interface side of the i-type layer, the n-type layer / i-type layer, a hydrogen atom or /
And a large distribution of the content of halogen atoms are mentioned as a preferred distribution form, and the content of hydrogen atoms and / or halogen atoms in the vicinity of the interface is 1.1 to 2 times the content in the bulk. The range is mentioned as a preferable range. By increasing the content of hydrogen atoms or halogen atoms near each interface of the p-type layer / i-type layer / and the n-type layer / i-type layer, defect levels and mechanical strain near the interface can be reduced. The photovoltaic power and the photocurrent of the photovoltaic device of the present invention can be increased.

The electric characteristics of the p-type layer and the n-type layer of the photovoltaic element are preferably those having an activation energy of 0.2 eV or less, more preferably 0.1 eV or less. The non-resistance is preferably 100 Ωcm or less, and 1 Ωcm
The following is more preferred. Further, the thickness of the p-type layer and the n-type layer is preferably 1 to 50 nm, more preferably 3 to 10 nm.

Examples of a p-type semiconductor layer or an n-type semiconductor layer using II-VI group elements include CdS and CdT.
e, ZnO, ZnSe, etc., and I-III-VI
Examples of using a Group ₂ element include CuInSe ₂ , Cu (I
nGa) Se ₂ , CuInS ₂ , CuIn (Se,
S) ₂ , Cu (InGa) (SeTe) _{2 and the} like.

(3) Method of Forming Semiconductor Layer In order to form a suitable group IV and group IV alloy-based amorphous semiconductor layer as a semiconductor layer of the photovoltaic device of the present invention, a preferable manufacturing method is RF Plasma CV using alternating current or high frequency such as plasma CVD or microwave plasma CVD
Method D.

In the microwave plasma CVD method, a material gas such as a raw material gas or a diluent gas is introduced into a deposition chamber (vacuum champer) which can be decompressed, and the internal pressure of the deposition chamber is kept constant while being discharged by a vacuum pump. The microwave oscillated by the microwave power supply is guided by a waveguide, introduced into the deposition chamber through a dielectric window (alumina ceramics or the like), and generated by decomposing a material gas plasma,
This is a method for forming a desired deposited film on a substrate placed in a deposition chamber, and can form a deposited film applicable to a photovoltaic element under a wide range of deposition conditions.

When the semiconductor layer for a photovoltaic device of the present invention is deposited by microwave plasma CVD, the substrate temperature in the deposition chamber is 100 to 450 ° C., and the internal pressure is 0.5 to 30 m.
Torr, microwave power is 0.01 to 1 W / c
m ³ and the frequency of the microwave are preferably in the range of 0.1 to 10 GHz.

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 Torr, and the RF power is 0.001 to 0.001.
5.0 W / cm ² , the deposition rate is 0.1 to 30 ° / sec.
c is mentioned as a suitable condition.

The source gas suitable for depositing the group IV and group IV alloy amorphous semiconductor layer suitable for the photovoltaic device of the present invention includes a gasizable compound containing silicon atoms,
Examples include a gasizable compound containing a germanium atom, a gasizable compound containing a carbon atom, and a mixed gas of the compound.

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

Specific examples of the gasifiable compound containing a germanium atom include GeH ₄ , GeD ₄ , GeF ₄ ,
GeFH ₃ , GeF ₂ H ₂ , GeF ₃ H, GeHD ₃ , Ge
H ₂ D ₂ , GeH ₃ D, Ge ₂ H ₆ , Ge ₂ D _{6 and the} like.

Elements that increase the band gap of the pin junction i-type semiconductor layer near the light incident side of the stack type photovoltaic element include carbon, oxygen, nitrogen and the like.

Specific examples of the gasizable compound containing a carbon atom include CH ₄ , CD ₄ , C _n H _{2n + 2} (n is an integer), C _n H _2n (n is an integer), C ₂ H ₂ , C ₆ H ₆ , CO ₂ ,
CO and the like.

Examples of the nitrogen-containing gas include N ₂ , NH ₃ , ND
₃ , NO, NO ₂ and N ₂ O.

As the oxygen-containing gas, O ₂ , CO, C
O ₂ , NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH
And the like.

Examples of the substance introduced into the p-type layer or the n-type layer for controlling the valence electrons include group III atoms and group III atoms in the periodic table.

Examples of the material effectively used as a starting material for introducing a group III atom include B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , and B ₅ for introducing a boron atom. H ₁₁ , B
Borohydrides such as ₆ H ₁₀ , B ₆ H ₁₂ , B ₆ H ₁₄ , BF ₃ , B
Examples thereof include boron halide such as Cl ₃ . . In addition, AlCl ₃ , GaCl ₃ , InCl ₃ , T
1Cl _{3 and the} like can also be mentioned. Particularly, B ₂ H ₆ and BF ₃ are suitable.

Effectively as a starting material for introducing a group V atom
Specifically, PH is used for introducing a phosphorus atom.
_Three, P_TwoH_FourPhosphorus hydride, PH_Four, PF_Three, PF_Five, PCl
_Three, PCl_Five, PBr_Three, PBr_Five, PI_ThreeHalogenation
Phosphorus. In addition, AsH_Three, AsF_Three, AsCl
_Three, AsBr_Three, AsF_Five, SbH_Three, SbF_Three, SbF_Five ,
SbCl_Three, SbCl_Five, BiH_Three, BiCl_Three, BiBr
_ThreeAnd the like. Especially PH_Three, PF_ThreeSuitable for
I have.

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

Particularly, a microcrystalline or polycrystalline semiconductor or a-S
When depositing a wide band gap layer such as iC: H with little light absorption, it is necessary to dilute the source gas 2 to 100 times with hydrogen gas and to introduce a relatively high microwave or RF power. It is preferred.

(Transparent electrode 106) In the present invention, the transparent electrode is an electrode on the light incident side that transmits light,
By optimizing the film thickness, it also serves as an anti-reflection film. The transparent electrode has a high transmittance in a wavelength region where the semiconductor layers 103 to 105 can absorb,
Low resistivity is required. Preferably, 550n
It is desirable that the transmittance at a wavelength of m or more is 80% or more, more preferably 85% or more. The resistivity is preferably 5 × 10 ⁻³ Ωcm or less, more preferably 1 × 10 ⁻³ Ωcm or less.
× 10 ⁻³ Ωcm or less.

The materials include In ₂ O ₃ , SnO ₂ ,
ITO (In ₂ O ₃ + SnO ₂ ), ZnO, CdO, Cd ₂
SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ , N
A conductive oxide such as axWO ₃ or a mixture thereof is preferably used. SnO ₂ , In ₂ O ₃ , ITO
More preferably, it is a metal oxide or a composite oxide thereof selected from the above.

In addition, an element (dopant) that changes the conductivity may be added to these compounds. For example, when the transparent electrode is ZnO, Al, In, B, Ga, Si
When F or the like is In ₂ O ₃ , Sn, F, Te, T
When i, Pb, etc. are SnO ₂ , F, Sb,
P, As, In, Tl, Te, W, Cl, Br, I and the like are preferably used.

As a method for forming the transparent electrode, EB evaporation,
Various deposition methods such as sputter deposition, various CVD methods, spray methods, spin-on methods, and dipping methods are suitably used.

(Current Collecting Electrode 107) In the present invention, the current collecting electrode is formed on a part of the transparent electrode 106 as necessary when the resistivity of the transparent electrode 106 cannot be sufficiently low. And lowers the series resistance of the photovoltaic element.

Examples of the material include metals such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, zirconium, alloys such as stainless steel, and powdered metals. And a conductive paste using the same.
The shape of the semiconductor layers 103 to 105 is as small as possible.
It is formed so as not to block incident light to the light.

The area occupied by the current collecting electrode in the light incident side surface of the photovoltaic element is preferably 15% or less, more preferably 10% or less, and still more preferably 5%.
It is as follows.

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

When a photovoltaic element (module or panel) having a desired output voltage and output current is manufactured using the photovoltaic element of the present invention, the photovoltaic elements of the present invention are connected in series or in series. They are connected in parallel, protective layers are formed on the front and back surfaces, and output output electrodes and the like are attached. At this time, the support substrate 101 on which the photovoltaic elements are formed may be arranged on another substrate. When the photovoltaic elements of the present invention are connected in series, a diode for preventing backflow may be incorporated.

[0146]

The present invention will be described in more detail with reference to the following examples. The evaluation methods performed in the examples are as follows.

(1) Initial Photoelectric Conversion Efficiency A solar cell was placed under AM-1.5 (100 mW / cm ² ) light irradiation, and VI characteristics were measured.

(2) Light Deterioration Test A solar cell whose initial photoelectric conversion efficiency was measured in advance was placed in an environment of a humidity of 50% and a temperature of 25 ° C., and irradiated with AM-1.5 light for 500 hours. The photoelectric conversion efficiency under -1.5 light irradiation was measured, and the reduction rate (photoelectric conversion efficiency after light deterioration test / initial photoelectric conversion efficiency) was calculated.

(3) Vibration Deterioration Test A solar cell whose initial photoelectric conversion efficiency was measured in advance was placed in a dark place with a humidity of 50% and a temperature of 25 ° C.
After applying a vibration having an amplitude of 0.1 mm at 500 Hz for 500 hours, A
The photoelectric conversion efficiency under M-1.5 light irradiation was measured, and the reduction rate (photoelectric conversion efficiency after vibration degradation test / initial photoelectric conversion efficiency) was calculated.

(4) High Temperature and High Humidity Reverse Bias Test A solar cell whose initial photoelectric conversion efficiency was measured in advance was placed in a dark place at a humidity of 85% and a temperature of 85 ° C.
The leak current after applying 0.85 V for 500 hours was measured, and the increase rate (the leak current after the high-temperature high-humidity reverse bias test / the initial leak current) was calculated.

Example 1 First, a transparent conductive layer 102 was deposited using the deposition apparatus shown in FIG. 3 to produce a substrate with a transparent conductive layer.

First, the supporting substrate 101 was manufactured. A Corning glass substrate (# 7059) having a thickness of 1.1 mm and a size of 50 × 50 mm ² was subjected to ultrasonic cleaning with acetone and isopropanol and dried with hot air.

A source gas supply device (not shown) is connected to the deposition device of FIG. The raw material gas cylinders are all purified to ultra-high purity.
Ar gas cylinder, Xe gas cylinder, O ₂ gas cylinder, F ₂
There is a gas cylinder, the target is Al and ZnO,
Sputtering can be performed by switching each in a vacuum. An RF power supply 311 was used as a bias power supply.

A substrate 303 was placed on the substrate holder 302 shown in FIG. The deposition chamber 301 was evacuated from the exhaust pipe 316 connected to the oil expansion pump. When the pressure becomes 1 × 10 ⁻⁶ , 50 g of Xe gas is introduced into the deposition chamber 301 from the gas introduction pipe 317.
sccm, O ₂ gas at 5 sccm, and F ₂ gas at 0% of the total flow rate.
A gas mixed with a predetermined amount in the range of ５０50% was introduced, and the pressure was adjusted to 9 mTorr by a conductance valve (not shown). RF when substrate temperature reaches 200 ℃
An RF power of 300 W was applied from a power supply 311 to the transparent conductive layer target 308 to generate plasma 319. The shutter 314 was opened to start film deposition. Deposition rate is 2
0 ° / s.

On the support substrate 101, a Zn layer having a thickness of 2.0 μm was formed.
When the O transparent conductive layer 102 is formed, the shutter 31
4 was closed and the plasma 319 was extinguished. Transparent conductive layer 1
02 had a conductivity of 10 ^-4 (1 / Ωcm).

At this time, the ratio of F ₂ was changed (SC actual 1).
-1), (SC actual 1-2), (SC ratio 1-1), (SC
Ratio 1-2) was produced. And the sampling length 40n
m, the distribution of the inclination angle of the surface shape of the transparent conductive layer 102 was measured. Table 3 shows the results.

Next, the semiconductor layers 103 to 105 were deposited using the deposition apparatus shown in FIG. 4 to produce a solar cell having the structure shown in FIG. 1A.

First, an n-type semiconductor layer 103, an i-type semiconductor layer 104,
The p-type semiconductor layers 105 were sequentially formed. The p-type semiconductor layer 103 made of a-Si is formed by an RF plasma CVD method,
The i-type semiconductor layer 104 made of a-Si was formed by MW (microwave) plasma CVD, and the p-type semiconductor layer 105 made of μx-Si was formed by RF plasma CVD.

FIG. 4 shows an apparatus capable of carrying out a plasma CVD method, wherein 401 is a reaction chamber, and 402 is a transparent conductive layer 1.
02, a substrate 403, a heater, 404, a conductance valve, 405, a microwave waveguide,
06 is a microwave introduction part, 407 is a microwave introduction window made of alumina-ceramics, 408 is an RF introduction part,
409 is an RF power supply having a built-in matching circuit, 410 plasma, 411 is a shutter, 414 is an exhaust pipe, 415
Is a gas introduction pipe. 412 is the traveling direction of the microwave,
413 indicates an exhaust direction, and 416 indicates a gas introduction direction. Although not shown, a microwave power supply is connected to the microwave waveguide 405, and the vacuum pump is connected to the exhaust pipe 41.
4.

Further, a source gas supply device (not shown) is connected through a gas introduction pipe 415. The raw material gas cylinders are all purified to ultra-high purity, and are SiH ₄ gas cylinder, SiF ₄ gas cylinder, CH ₄ gas cylinder, GeH
₄ gas cylinder, PH ₃ / H ₂ (PH ₃ : 1%) gas cylinder,
A B ₂ H ₆ / H ₂ (B ₂ H ₆ : 1%) gas cylinder and an H ₂ gas cylinder were connected.

[0161] The microwave CV
The following procedure is used to actually form a layer using the D method.

First, the substrate 402 formed up to the transparent conductive layer 102 is attached to the heater 403 inside the reaction chamber 401, and a vacuum pump such as an oil diffusion pump is used so that the pressure inside the reaction chamber 401 becomes 1 × 10 ⁻⁴ Torr or less. Exhaust with. When the pressure becomes 1 × 10 ⁻⁴ Torr or less, H ₂ ,
A gas such as He is introduced from the gas introduction pipe 415 into the reaction chamber 401, the heater 403 is turned on, and the temperature of the substrate 402 is set to a desired temperature. When the temperature of the substrate 402 is stabilized, a source gas is introduced from the gas introduction pipe 415, and microwave power is reacted from a microwave power supply (not shown) through the microwave waveguide 405, the microwave introduction section 405, and the microwave introduction window 407. It is introduced into the chamber 401. When the plasma 410 is generated, the conductance valve 404 is adjusted to a desired pressure, and the RF power source 409 is adjusted.
And RF power is introduced from the RF introduction unit 408. At that time, it is preferable to adjust the matching circuit to minimize the reflected power. Next, the shutter 411 is opened, and when a layer having a desired film thickness is formed, the shutter 411 is closed, and the introduction of the RF power and the microwave power and the introduction of the raw material gas are stopped to prepare for forming the next layer. .

Hereinafter, each layer will be described specifically.

First, the n-type semiconductor layer 10 made of a-Si
3 was formed in the following procedure. 300 sccm of H ₂ gas
When the pressure in the reaction chamber 401 was stabilized at 1.0 Torr and the substrate temperature was stabilized at 250 ° C., the SiH ₄ gas was
ccm, PH ₃ / H ₂ gas 2sccm, H ₂ gas 100s
Ccm was introduced, and the pressure in the reaction chamber 401 was adjusted to 10 Torr. The power of the RF power source 409 is set to 5 W, RF power is applied to the bias electrode, and the plasma 41
0, the shutter 411 is opened, and the transparent conductive layer 1
02, the formation of the n-type semiconductor layer 103 is started, and the layer thickness 20
When the n-type semiconductor layer 103 of nm is formed, the shutter 411 is closed, the RF power source 409 is turned off, and the plasma 4
10, the formation of the n-type semiconductor layer 103 was completed.
SiH ₄ gas into the reaction chamber 401, stopping the flow of PH ₃ / H _{2, 2} minutes, after which continued to flow H ₂ gas into the reaction chamber 401, the flow of H ₂ is also stopped, the reaction chamber 401 and the gas The inside of the pipe was evacuated to 1 × 10 ⁻⁵ Torr.

Next, the i-type semiconductor layer 10 made of a-Si
4 was formed in the following procedure. 500 sccm of H ₂ gas
Introduced, pressure 0.01 Torr, substrate temperature 350 ° C
I tried to be. When the substrate temperature becomes stable, the Si
H ₄ gas was introduced, and the SiH ₄ gas flow rate was 50 sccm,
The H ₂ gas flow rate was adjusted to 500 sccm, and the pressure in the reaction chamber 401 was adjusted to 0.02 Torr. Then M
The power of the W power source is set to 500 W, and M
W power is introduced, plasma 410 is generated, the shutter 411 is opened, the formation of the i-type semiconductor layer 104 is started on the n-type semiconductor layer 103, and the shutter 411 is formed when the 200-nm-thick i-type semiconductor layer 104 is formed. And close M
The W power was turned off, the plasma 410 was extinguished, and the formation of the i-type semiconductor layer 104 was completed. Stop the flow of SiH ₄
After flowing H ₂ gas for a minute, the inflow of H ₂ gas is stopped,
The inside of the reaction chamber 401 and the inside of the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr.

Next, the p-type semiconductor layer 1 made of μc-Si
05 was formed by the following procedure. 500 scc of H ₂ gas
m, and the pressure in the reaction chamber 401 was set to 1 Torr, and the substrate temperature was set to 200 ° C. When the substrate temperature was stabilized, SiH ₄ gas and BF ₃ / H ₂ gas were introduced. At this time, the flow rate of the SiH ₄ gas is ₂ sccm, the flow rate of the H ₂ gas is 100 sccm, and the flow rate of the BF ₃ / H ₂ gas is 500 sccm.
cm and the pressure were adjusted to 1 Torr. Thereafter, the power of the RF power supply 409 is set to 50 W, plasma 410 is generated, the shutter 411 is opened, and the formation of the p-type semiconductor layer 105 on the i-type semiconductor layer 104 is started. After the formation of the p-type semiconductor layer 105, the shutter 411 was closed, the RF power supply 409 was turned off, and the plasma 410 was extinguished. Stop the flow of SiH ₄ gas and BF ₃ / H ₂ gas
After flowing H ₂ gas for a minute, the inflow of H ₂ gas is stopped,
The inside of the reaction chamber 401 and the inside of the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr, and the reaction chamber 401 was leaked.

Next, on the p-type semiconductor layer 105, ITO having a thickness of 70 nm was vacuum-deposited as a transparent electrode 106 by a resistance heating vacuum deposition method.

Next, a mask having a comb-shaped hole was placed on the transparent electrode 106, and Cr (40 nm) / Ag (1000 n
m) / Cig (40 nm) comb-shaped current collecting electrode 107
Was vacuum-deposited by an electron beam vacuum deposition method.

Thus, the production of the solar cell has been completed. Table 3 shows the evaluation results. In addition, evaluation was shown by the relative value when (SC actual 1-1) was set to 1. (SC actual 1-1) and (SC ratio 1
The difference of -1) was mainly caused by the difference between the fill filters and the short-circuit current.

[0170]

[Table 3]

<< Embodiment 2 >> The supporting substrate 101 (SUS30
4) The film thickness was 1 μm and the conductivity was 10 μm under various conditions by DC magnetron sputtering in the same manner as in Example 1.
^-4 (1 / Ωcm) transparent conductive layer 102 was produced. The sample was etched with 2% acetic acid for several seconds at different temperatures to produce various samples. The distribution of the inclination angle of the surface was determined at a sampling length of 20 nm. Table 4 shows the results.

As in the first embodiment, the semiconductor layers 103 to 105
Table 4 shows the results of evaluation by stacking pin amorphous silicon semiconductor solar cells.

[0173]

[Table 4]

<< Embodiment 3 >> The supporting substrate 101 (SUS30
4) The film thickness is 1 μm and the conductivity is 10 ⁻⁴ under various conditions by the magnetron sputtering method using the manufacturing method as in Example 1 above.
A transparent conductive layer 102 of (1 / Ωcm) tin oxide thin film was prepared.

The standard deviation of the distribution of the inclination angle is 2 ° to 30 ° ±
And evaluated. The average of the local valley angles on the surface was determined. Table 5 shows the results.

As in Example 1, a pin amorphous silicon semiconductor solar cell was laminated as a semiconductor layer. At this time, the deposition rate of the i-type semiconductor layer 104 was increased to 20 ° / s. Table 5 shows the evaluation results.

[0177]

[Table 5]

Example 4 A solar cell was fabricated in the same manner as in Example 3, except that the transparent conductive layer 102 was made of an indium oxide thin film, and the standard deviation of the distribution of the inclination angle was adjusted to 30 ° ± 2 °. . Table 6 shows the results.

[0179]

[Table 6]

<< Embodiment 5 >> The supporting substrate 101 (SUS30
4) A zinc oxide thin film having a thickness of 1 μm was formed as the transparent conductive layer 102 under various conditions by the magnetron sputtering method using the manufacturing method as in Example 1 above. The zinc oxide thin film was formed by embedding aluminum oxide on a target and simultaneously performing sputtering. The conductivity increased as the amount of aluminum oxide added increased.

As in the first embodiment, the semiconductor layer
In-amorphous silicon semiconductor solar cells were stacked.
At this time, the i-type semiconductor layer was deposited in the deposition chamber where the film deposition was performed for a long period without cleaning the deposition chamber.

The surface shape was measured at a sampling length of 20 nm. Both are normal distributions centered on 0 °,
The inclination angle is 35 ° ± 2 ° and the kurtosis is 0.21 ±.
0.03, the average of the local valley angles is 145 ° ± 2 °,
The average value of the local peak angles was 140 ° ± 2 °, and there was no clear change by the addition of aluminum oxide.

FIG. 9 shows the results of measuring photovoltaic conversion efficiencies by fabricating photovoltaic elements using films having different conductivities. FIG.
If the conductivity is 10 ^-8 (1 / Ωcm) or more, the series resistance does not become too large and the photoelectric conversion efficiency does not decrease as long as it is 10 ^-2 (1 / Ωcm) or less. For example, the shunt resistance does not decrease and the yield does not decrease.

When this sample surface was observed by SEM, many pinholes were observed in each sample.

Example 6 A supporting substrate 101 (SUS30
4) A zinc oxide thin film having a thickness of 1 μm was formed as the transparent conductive layer 102 under various conditions by the magnetron sputtering method using the manufacturing method as in Example 1 above. As the zinc oxide thin film, copper was buried in the transparent conductive layer as an impurity for increasing corrosion resistance on the target, and sputtering was performed at the same time. When the amount of copper added was changed, the conductivity did not change much. This sample was immersed in a 30% iron chloride aqueous solution for 5 minutes.
The aqueous iron chloride solution is an etchant used for patterning ITO. No change was seen in the sample made with the copper embedded target. There was no significant difference in the surface shape between the sample made with the copper embedded target and the sample not embedded.

As in the case of the first embodiment, the semiconductor layer
After laminating the in-amorphous silicon semiconductor solar cell, it was immersed in a 30% iron chloride aqueous solution for 1 minute to pattern the ITO. As a result of measuring the photoelectric conversion efficiency, the conversion efficiency was 0.73 in the sample manufactured without copper embedded.
The conversion efficiency was not reduced in the sample made with the target in which the copper was embedded, although it decreased twice.

Embodiment 7 A supporting substrate 101 (SUS30
4) An aluminum thin film having a thickness of 50 nm was formed as the metal layer 108 by magnetron sputtering under various conditions using the above-described manufacturing method as a method of forming the metal layer 108. Sampling length 20 for surface shape of metal layer
Measured in nm. Table 7 shows the results.

Thereafter, a zinc oxide thin film was formed as the transparent conductive layer 102 by DC magnetron sputtering. The film thickness was 1 μm, and the conductivity was 10 ⁻⁴ (1 / Ωcm).

As in the first embodiment, the semiconductor layer
The in-amorphous silicon semiconductor solar cells were laminated and evaluated. Table 7 shows the evaluation results.

[0190]

[Table 7]

[0191]

According to the photovoltaic device of the present invention, the short-circuit current can be improved, the open voltage and the fill factor can be maintained, and the photovoltaic device can be improved. In addition, light deterioration and vibration deterioration of the photovoltaic element can be improved, and durability can be improved even in a state where a reverse bias is applied in a high temperature and high humidity environment.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic cross-sectional views each showing an example of a photovoltaic element of the present invention.

FIG. 2A is a conceptual diagram of a tilt angle of a surface shape of a transparent conductive layer, and FIG. 2B is a conceptual diagram of a local valley and a local peak.

FIG. 3 is a schematic cross-sectional view showing an example of an apparatus for forming a metal layer and a transparent conductive layer of a substrate with a transparent conductive layer of the present invention.

FIG. 4 is a schematic cross-sectional view showing one example of an apparatus for forming a semiconductor layer of a photovoltaic element of the present invention.

FIG. 5 is a graph showing an inclination angle distribution of a surface of a transparent conductive layer.

FIG. 6 is a graph showing the relationship between the center line average roughness Ra of the surface of the transparent conductive layer and the short-circuit photocurrent.

FIG. 7 is a graph showing the relationship between the standard deviation of the distribution of the inclination angle of the surface of the transparent conductive layer and the short-circuit photocurrent.

FIG. 8 is a graph showing the relationship between the standard deviation of the distribution of the inclination angle of the surface of the transparent conductive layer and the short-circuit photocurrent using the sampling length as a parameter.

FIG. 9 is a graph showing the relationship between the conductivity of the transparent conductive layer and the photoelectric conversion efficiency.

[Explanation of symbols]

 101 Support substrate 102 Transparent conductive layer 103 N-type semiconductor layer 104 i-type semiconductor layer 105 p-type semiconductor layer 106 transparent electrode 107 collecting electrode 108 metal layer 301 deposition chamber 302 substrate holder 303 substrate 304 heater 305 matching box 306 RF power supply 307 metal Target 308 Transparent conductive layer target 309 Target 310, 312 DC power supply 311 RF power supply 313, 314, 315 Shutter 316 Exhaust pipe 317 Gas introduction pipe 318 Rotation axis 319 Plasma 320 Gas introduction direction 321 Exhaust direction 401 Reaction chamber 402 Substrate 403 Heater 404 Conductance valve 405 Microwave waveguide 406 Microwave introduction part 407 Microwave introduction window 408 RF introduction part 409 RF power supply 410 Plasma 411 Shut 412 Microwave traveling direction 413 Exhaust direction 414 Exhaust pipe 415 Gas introduction pipe 416 Gas introduction direction

Claims (12)

[Claims] In a substrate with a transparent conductive layer in which at least one transparent conductive layer is laminated on a supporting substrate, a sampling length dx when a distance of a surface of the transparent conductive layer from a surface of the supporting substrate is f is defined as: The distribution of the inclination angle arctan (df / dx) in the range of 20 nm to 100 nm is as follows:
A substrate with a transparent conductive layer, which has a normal distribution with a kurtosis of −1.2 to 0.5 centered on 0 ° and a standard deviation of 20 ° to 55 °. 2. The substrate with a transparent conductive layer according to claim 1, wherein the average value of the distribution of angles formed by local valleys in the range is 170 ° to 110 °. 3. The substrate with a transparent conductive layer according to claim 1, wherein the average value of the distribution of the angles formed by the local peaks in the range is 170 ° to 100 °. 4. The transparent conductive layer contains at least one selected from oxides, nitrides, or sulfides of aluminum, zinc, tin, indium, titanium, and tantalum, and composite compounds thereof. Claim 1
4. The substrate with a transparent conductive layer according to any one of items 1 to 3. 5. The method according to claim 1, wherein the conductivity of the transparent conductive layer is 10 ⁻⁸ ( ^1/1 ).
The substrate with a transparent conductive layer according to any one of claims 1 to 4, wherein the substrate has a resistivity of 10? ² (1 /? Cm). 6. The substrate with a transparent conductive layer according to claim 1, wherein the transparent conductive layer contains a corrosion resistance improving material. 7. The substrate with a transparent conductive layer according to claim 1, further comprising a metal layer between the support substrate and the transparent conductive layer. 8. A sampling length dx when a distance of a surface of the metal layer in contact with the transparent conductive layer from a support substrate surface is fm.
Is the tilt angle arct in the range of 20 nm to 100 nm.
The distribution of an (dfm / dx) is a normal distribution with a kurtosis of −1.0 to 0.5 centered on 0 ° and a standard deviation of 5 ° to
The substrate with a transparent conductive layer according to claim 7, wherein the angle is 20 °. 9. The method according to claim 9, wherein the metal layer is gold, silver, copper, aluminum,
9. The substrate with a transparent conductive layer according to claim 7, comprising at least one selected from magnesium and an alloy thereof. 10. A photovoltaic device comprising a substrate with a transparent conductive layer according to claim 1 and at least one semiconductor layer laminated thereon. 11. The photovoltaic device according to claim 10, wherein said semiconductor layer is made of a non-single-crystal silicon-based semiconductor. 12. The photovoltaic device according to claim 11, wherein the non-single-crystal silicon-based semiconductor includes a layer containing a microcrystalline phase.