JPH1065197A - Photoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoelectric transducer, wherein absorption of light to semiconductor is increased and conversion efficiency is high by forming a photoelectric conversion layer and an incident light side transparent conducting layer, on a ZnO layer which is whitely muddy on a substrate. SOLUTION: A ZnO layer 103 is deposited on an Al substrate 101, by using a ZnO target to which Cu of 5% is added. The surface of the ZnO layer is uneven. A substrate on which a lower electrode is formed is set in a capacitance-coupled high-frequency CVD equipment, and high vacuum evacuation is performed by an evacuation pump. When the pressure is stabilized, plasma is generated, and an n-type a-Si layer 105, an i-type a-Si layer 106 and a p-type μc-Si layer 107 are formed on the transparent layer 103. After a specimen is taken out from the high-frequency CVD equipment, and ITO is deposited by a resistance-heating vacuum deposition equipment, paste containing iron chloride aqueous solution is printed, the pattern of a desired transparent electrode 108 is formed, Ag paste is screen-printed, and a collector electrode 109 is formed, thereby obtaining a solar cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having high performance, high reliability and easy mass production.

[0002]

2. Description of the Related Art As a future energy source for humankind,
There is no danger of radiation due to fossil fuels such as oil and coal, which are said to cause global warming due to the carbon dioxide generated as a result of their use, and even during normal operation, even during normal operation. Relying entirely on nuclear power is problematic. On the other hand, solar cells using the sun as an energy source have very little influence on the global environment, and are expected to be more widely used. However, at present, there are some problems that hinder full-fledged diffusion.

Conventionally, monocrystalline or polycrystalline silicon has been often used for photovoltaic power generation. However, solar cells as an example of these photovoltaic elements require a lot of energy and time to grow crystals, and require complicated processes thereafter. It was difficult. On the other hand, so-called thin-film semiconductor photovoltaic devices using amorphous silicon (hereinafter referred to as a-Si) or a compound semiconductor such as CdS.CuInSe ₂ have been actively studied and developed. In these photovoltaic devices, it is only necessary to form as many semiconductor layers as necessary on an inexpensive substrate such as glass or stainless steel, the manufacturing process is relatively simple, and the cost can be reduced. ing. However, thin-film semiconductor photovoltaic devices have not been used in earnest because their conversion efficiency is lower than that of crystalline silicon photovoltaic devices, and their reliability for long-term use is uncertain. In order to improve the performance of the thin-film semiconductor photovoltaic device, various devices have been devised.

One of them is a backside reflection layer for returning light not absorbed by the semiconductor layer to the semiconductor layer again by using a layer having an increased light reflectance to effectively use incident light. Therefore, when light is incident from the substrate side of the transparent substrate, the electrode formed on the surface of the semiconductor is made of silver (Ag),
It is preferable to use a metal having high reflectance such as aluminum (Al) or copper (Cu). In the case where light is incident from the surface of the semiconductor layer, a semiconductor layer may be formed after a similar metal layer is formed over a substrate. If a transparent layer having appropriate optical properties is interposed between the metal layer and the semiconductor layer, the reflectance can be further increased by the multiple interference effect.
FIG. 4A shows a case where a transparent layer is not provided between silicon and various metals, and FIG. 4B shows a case where zinc oxide (ZnO) is interposed as a transparent layer between silicon and various metals. And simulation results showing an improvement in reflectance.

[0005] The use of such a transparent layer is effective in improving the reliability of the photovoltaic element. Tokiko Sho 60-41
No. 878 describes that the use of a transparent layer can prevent alloying between a semiconductor and a metal layer. See also U.S. Patents 4,532,372 and 4,598,306.
Describes that the use of a transparent layer having an appropriate resistance can prevent an excessive current from flowing between the electrodes even if a short circuit occurs in the semiconductor layer.

Another method for improving the conversion efficiency of a photovoltaic element is a method in which the interface between the photovoltaic element and the front and / or back surface reflective layers is made fine (texture structure). With such a configuration, light is scattered at the interface between the photovoltaic element and the front surface and / or back surface reflection layer, is further confined inside the semiconductor, and can be effectively absorbed in the semiconductor (light trapping effect). Looks like When the substrate is transparent, the surface of a transparent electrode such as tin oxide (SnO ₂ ) on the substrate may have an uneven structure. In the case where light enters from the surface of the semiconductor, the surface of the metal layer used for the back reflection layer may have an uneven structure. M. Hiras
aka, K .; Suzuki, K .; Nakatani,
M. Asano, M .; Yano, H .; Okaniwa shows that a concave-convex structure for a back reflection layer can be obtained by depositing Al while adjusting the substrate temperature and the deposition rate.
(Solar Cell Materials 20
(1990) pp99-110) FIG. 5 shows an example of an increase in absorption of incident light due to the use of the back reflection layer having such an uneven structure. Here, the curve (a) shows the spectral sensitivity of an a-Si solar cell using smooth Ag as the metal layer, and the curve (b) shows the spectral sensitivity when Ag having an uneven structure is used.

Further, it is possible to combine the concept of the back surface reflection layer composed of two layers of the metal layer and the transparent layer with the concept of the uneven structure. U.S. Pat. No. 4,419,533 discloses the concept of a back reflection layer in which the surface of a metal layer has a textured structure and a transparent layer is formed thereon. Such a combination is expected to significantly improve the conversion efficiency of the solar cell. However, according to the findings of the present inventors, in many cases, the effect as expected in advance was not often obtained. Further, depending on the deposition conditions of the semiconductor, despite the provision of the transparent layer, sufficient reliability for use of the formed solar cell under high temperature and high humidity may not be obtained in some cases. For this reason, thin-film solar cells have not yet been widely used for photovoltaic power generation, although they may be produced at low prices.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a photovoltaic element having high conversion efficiency and high reliability by using an improved back reflection layer. The purpose is to do.

[0009]

The present inventors have found that the following problems exist in the conventional back reflection layer.

(1) Decrease in reflectance due to unevenness of the metal layer When the metal layer has an uneven structure, light reflected on the surface is irregularly reflected in various directions. However, in consideration of this point, even if the measurement is performed using a reflectance measuring device equipped with an integrating sphere that can collect the light reflected in all directions, the uneven metal layer has a higher reflectance than the smooth metal. It tends to be significantly lower.
In particular, the tendency is remarkable in the case of Al and Cu. Therefore, light that has passed through the semiconductor layer cannot be effectively reflected and returned to the semiconductor. As a result, the conversion efficiency of the photovoltaic element does not become as high as expected.

(2) Diffusion of metal to the surface of the transparent layer When depositing a semiconductor layer on the backside reflective layer, usually 20
The substrate temperature is set to 0 degree or more. At such a temperature, metal atoms can diffuse through the transparent layer to the surface of the transparent layer. It is considered that the function of the transparent layer is insufficient when the metal directly contacts the semiconductor layer in this manner, leading to a decrease in reliability.

(3) Diffusion of Metal into Semiconductor Layer When the transparent layer is formed, the underlying metal layer may be partially exposed. This phenomenon is particularly remarkable when the unevenness of the uneven structure of the metal layer is increased and the transparent layer is thinned. When a semiconductor layer is deposited thereon, metal atoms diffuse from the exposed portion of the metal layer into the semiconductor layer, which affects the characteristics of the semiconductor junction.

(4) Problems in the Post-Process Since the semiconductor layer has a defect such as a pinhole, the electrode on the surface of the semiconductor layer and the transparent layer can directly contact through such a defect. If the transparent layer does not have an appropriate resistance, it is impossible to prevent an excessive current from flowing in this portion.

If there is an exposed portion of the metal layer as described in (3) above, the upper electrode and the back electrode may come into contact with each other via a defective portion such as a semiconductor pinhole.

[0015]

As a result of studying these problems, the present inventors have come up with the following basic concept of the present invention.

According to the present invention, a substrate having a reflective metal surface and a large number of fine crater-shaped concave portions are formed on the substrate to form a white opaque ZnO layer, and a photoelectric conversion layer and an incident light are formed on the ZnO layer. A photoelectric conversion body comprising a light-side transparent conductive layer.

FIG. 1 shows an example of the structure of a photovoltaic device according to the present invention. 101 is a conductive substrate. A metal layer 102 having high reflectivity is formed on the surface. If the substrate itself is made of a material having a sufficiently high reflectivity, the metal layer 102 may be omitted.

Here, at least the surface of the metal layer 102 is a smooth surface having a reflectivity inherent to the metal, that is, a surface with irregularities of 1000 ° or less. The transparent layer 103 is formed thereon. The transparent layer 103 is transparent to light transmitted through the photoelectric conversion layer, has an appropriate electric resistance, and has an uneven structure. When the transparent layer has a plurality of layer regions, the first layer region 103a and the second layer region 103 in FIG.
3B shows an example including two layers. ) First layer area 103
The surface a has an uneven structure in which the unevenness is 500 ° -20,000 ° and the interval between the unevenness is 3000 ° -20,000 °, and is formed thereon. The electric characteristics of the second layer region 103b may be considerably higher than those of the first layer region 103a. However, in this case, it is necessary to make the thickness of the second layer region 103b as small as possible to reduce the resistance value per unit area of the solar cell. In the case where the transparent layer has a plurality of layer regions (FIG. 3 shows an example including two layers of the first layer region 103c and the second layer region 103d), the light incident surface of the first layer region 103c is uneven. When using an aqueous acid, alkali or salt solution at the time of forming surface irregularities of the second layer region 103d, which will be described later, the surface of the second layer region should not have a moderate electric resistance with a smooth surface having a pitch of 3000 ° or less. A first layer region 103c that is less likely to be eroded than 103d is used. The uneven pitch on the surface of the second layer region 103d is 3
000Å ～ 20,000Å Height of unevenness is 500Å ~ 200
The concave / convex structure of 00 ° and the light transmission characteristics and electric characteristics may be the same as those of the first layer region.

The transparent layer has chemical resistance to an etchant used in a later step. Above this is a semiconductor junction 104. Here, a pin type a is used as a semiconductor junction.
An example using a -Si photovoltaic element will be described. That is, 105 is n
Type a-Si, 106 is i-type a-Si, 107 is p-type a-Si
Si. When the semiconductor junction 104 is thin, FIG.
As shown in FIGS. 2 and 3, the entire semiconductor junction is
It often shows the same concavo-convex structure as 03. 108 is a transparent electrode on the surface. A comb-shaped integrated electrode 109 is provided thereon. The following effects are obtained by adopting such a structure.

(1) Since the surface of the metal layer 102 (or the substrate 101 itself) is smooth, the reflectance of light on the metal surface increases. Moreover, the transparent layer 103 (and the semiconductor junction 104)
Has a concave-convex structure, the phase of the incident light at the interface with the transparent layer is scattered due to the shift between the concave portion and the convex portion, so that an optical trapping effect occurs inside the semiconductor junction 104. Therefore, the incident light is effectively absorbed, and the conversion efficiency of the photovoltaic element is improved.

(2) Since the surface of the metal layer 102 (or the substrate 101 itself) is smooth, the contact area with the transparent layer 103 is reduced, and reactions such as diffusion of metal atoms into the transparent layer 103 are less likely to occur. .

Since the transparent layer 103 has an appropriate resistance, no excessive current flows even if a defect occurs in the photoelectric conversion layer 104. In addition, since the transparent layer 103 has chemical resistance, the back reflection layer is hardly damaged even in a later process.

(3) When the surface of the first layer region 103a has an uneven structure, even if a part of the metal layer 102 is exposed, it is again covered with the second layer region 103b. The probability of contact of the layer 102 is greatly reduced, and the reliability of the photovoltaic device is significantly improved.

(4) In addition, since the smooth first layer region 103c is deposited on the smooth metal layer, the frequency of partial exposure of the metal layer 102 which may occur when the metal layer has an uneven structure is extremely high. Thus, diffusion of metal atoms from the metal layer 102 to the semiconductor layer 104 can be prevented.

(5) Further, since the smooth first layer region 103c is deposited on the smooth metal layer 102, the frequency of partial exposure of the metal layer which may occur when the metal layer has an uneven structure is extremely high. And a highly reliable solar cell having almost no contact between the upper electrode and the metal layer can be obtained.

An experiment for showing the effect of the present invention will be described.

(Experiment 1) A 5 × 5 cm stainless steel plate (S
US430) by DC magnetron sputtering
Was deposited at 1500 °. The substrate temperature at this time was room temperature. Then, 4000 nm of ZnO was deposited thereon by a DC magnetron sputtering method. The substrate temperature at this time was 250 degrees. According to SEM observation, the surface of Al was smooth and glossy, but the surface of ZnO had a diameter of 4000-600.
Crater-like concave portions of about 0 ° were dense and cloudy. At this stage, the reflectance of light in the wavelength range of 6000-9000 ° was determined. On the back reflection layer thus formed, by glow discharge decomposition, an n-type a-Si layer was formed using SiH ₄ and PH ₃ as source gases at 200 °, an i-type a-Si layer was formed using SiH ₄ as source gas at 4000 °, and SiH 4 was formed. _4, BF _3, H
₂ as a source gas to form a p-type microcrystalline (μc) Si layer of 100
ÅThese were deposited to form a semiconductor junction. (Since about 10% of hydrogen (H) is contained in a-Si obtained by a glow discharge decomposition method such as SiH ₄ , it is generally referred to as a-Si: H. Therefore, an ITO film was deposited thereon by 650 ° as a transparent electrode by a resistance heating evaporation method. Further, an integrated electrode having a width of 300 μm was formed thereon using a silver paste to obtain a sample 1a.

Next, a sample 1b was obtained in the same manner as the sample 1a, except that the substrate temperature during the deposition of Al was set to 300 ° C.

Next, a sample 1c was obtained in the same manner as the sample 1a, except that the substrate temperature during the deposition of ZnO was room temperature.

Next, a sample 1d was obtained in the same manner as the sample 1a, except that a stainless steel substrate on which Al and ZnO were not deposited was used.

Next, an Al substrate having a surface of the same size as the stainless steel substrate polished to an irregular pitch of about 1000 ° was used.
Use 1e was obtained in the same manner as for sample 1a, except that l was not deposited.

The five samples thus obtained were designated AM-1.
5 was measured under a solar simulator, and the conversion efficiency as a photoelectric conversion element was evaluated. Table 1 shows the results. The following can be seen from Table 1. That is, (1) No matter what kind of back reflection layer is used, the conversion efficiency is improved as compared with the case where no back reflection layer is used. (2) The most efficient back surface reflective layer has an Al layer with a smooth surface and Z
This was the case where the nO layer had an uneven structure. (3) Even when polished Al is used as the substrate, smooth A
There is an effect equivalent to forming the l layer.

(Experiment 2) In Experiment 1, Ag was used instead of Al.
And a sample 2a was obtained in the same manner as in the sample 1a, except that no current collecting electrode was formed.

A sample 2 was prepared in the same manner as the sample 2a except that the substrate temperature during the deposition of Ag was changed to 350 degrees instead of the room temperature.
b was obtained.

In Sample 2a, the surface of Ag was smooth.
However, since the surface of ZnO has an uneven structure, the entire back reflection layer has no gloss. In Sample 2b, the surface of Ag showed an uneven structure.

Table 2 shows the measurement results of the conversion efficiency of both samples at AM-1.5. Although the conversion efficiency of Sample 2b was remarkably low, it was considered that a short circuit occurred due to current-voltage characteristics. Further observation of both samples by SEM shows that sample 2b
Spot defects were observed at various places, and the result of Auger analysis showed that Ag was diffused to the surface at these places.

(Experiment 3) aS in a deposition chamber where film deposition was performed for a long period without cleaning the deposition chamber
A sample 3a was obtained in the same manner as in the sample 1a of Experiment 1, except that i was deposited.

ZnO containing 0.5% of Cu for ZnO deposition
Except that a target was used, sample 3 was prepared in the same manner as sample 3a.
b was obtained.

Table 3 shows the measurement results of the conversion efficiency of both samples AM1.5. In each case, the conversion efficiency is lower than that of the sample 1a, and the influence of the short circuit is recognized. SE
According to M observation, many pinholes were observed in the a-Si layer in both samples. For reference, a chromium (Cr) electrode was formed directly on the surface of the back reflection layer, and a small current was passed to evaluate the resistivity of ZnO.
² (Ωcm), and 2 × 10 ⁵ (Ωcm) for sample 3b.
Met. That is, in sample 3b, ZnO was added by adding Cu.
It is considered that the specific resistance of the pinhole was appropriately increased and the current flowing through the pinhole was suppressed.

(Experiment 4) 0.5% Cu for ZnO deposition
Sample 1a of experiment 1 except that a ZnO target containing
A sample 4a was obtained in the same manner as in the case of the back reflection layer. The back reflection layer of Sample 1a was used as Sample 4b. Both samples were immersed in a 30% aqueous solution of iron chloride for 5 minutes. The aqueous iron chloride solution is an etchant used for patterning ITO. Although no particular change was observed in sample 4a, ZnO was significantly corroded in sample 4b. From this, it is anticipated that the use of the back reflection layer of the sample 4a makes it difficult for the thin film semiconductor to be damaged in a post-process even if there is a defect such as a pinhole.

(Experiment 5) In depositing the i-type a-Si layer in Experiment 1, the discharge power was tripled and the flow rate of SiH ₄ was 1
Sample 3 was obtained in the same manner as Sample 1a except that the deposition time was adjusted so that the thickness became 4000 °. When the surface shapes of the samples 1a and 5 and the back reflection layer used for them were observed by SEM, the following findings were obtained. On the surface of sample 1a, crater-shaped concave portions having a diameter of about 4000 to 6000 ° were densely packed and the depth of the crater was almost the same as the surface of the back reflection layer, whereas the surface of sample 5 was As a result, a raised structure having a finer pitch than that of the concave portion of the back reflection layer was developed, and the appearance was clearly different from the structure of the back reflection layer.

Next, when the sample 5 was evaluated under the solar simulator in the same manner as the sample 1a, the conversion efficiency was 8.
The value was 2%, which was lower than that of the sample 1a. This difference is mainly due to the low short-circuit photocurrent. When the surface shape of the semiconductor layer is different from the surface of the back reflection layer as in Sample 5, the light trapping effect is insufficient. I understood that.

(Experiment 6) A 5 × 5 cm stainless steel plate (S
US430) by DC magnetron sputtering
Was deposited at 1500 °. The substrate temperature at this time was room temperature. Then, 4000 nm of ZnO was deposited thereon by a DC magnetron sputtering method. The substrate temperature at this time was set to 300 degrees. According to the SEM observation, the surface of Al has an uneven pitch of 1
Although the surface was glossy with a smooth surface of 000 ° or less, crater-like concave portions having a diameter of about 4000 to 9000 ° were dense and cloudy on the surface of ZnO.

The difference between the heights of the irregularities is 2000-4000.
It was about Å. Further, ZnO was deposited thereon by a DC magnetron sputtering method at 500 °. The substrate temperature at this time was room temperature. According to SEM observation, the same concavo-convex structure as in the first layer region (at a substrate temperature of 300 ° C.) was maintained. At this stage, the reflectance of light in the wavelength range of 6000-9000 ° was determined. Thereafter, a semiconductor junction, a transparent electrode, and a current collecting electrode were formed in the same manner as in Experiment 1 to obtain a sample 6a.

Next, a sample 6b was obtained in the same manner as the sample 6a, except that the substrate temperature during the deposition of Al was set to 100 ° C.

Next, a sample 6c was obtained in the same manner as the sample 6a except that ZnO (semiconductor layer side) on the two-layer surface was not deposited.

Next, sample 6d was obtained in the same manner as sample 6a, except that the first layer of ZnO was deposited at a substrate temperature of 300 ° C. for 4500 ° and the second layer of ZnO was not deposited.

Next, the first layer of ZnO is heated at a substrate temperature of room temperature for 400 hours.
Sample 6e was obtained in the same manner as sample 6a except that 0 ° was deposited and ZnO of the second layer was not deposited.

Next, a first layer of ZnO is applied at a substrate temperature of 450 at room temperature.
0 ° and no second layer of ZnO was deposited
Sample 6f was obtained in the same manner as for sample 6a.

Next, an Al substrate having the same size as that of the stainless steel substrate polished to a roughness pitch of about 1000 ° was used.
Sample 6g was obtained in the same manner as Sample 6a, except that l was not deposited.

Further, an exposed portion of the metal layer is generated at the stage of forming the concave-convex structure for realizing an effective light trapping effect, and diffusion of metal atoms from the exposed portion to the semiconductor layer is provided by providing a second layer region. Can be prevented. Further, by providing the second layer region with a leakage current between the exposed portion and the upper electrode through a short-circuited portion in the semiconductor partially formed, the frequency is extremely reduced, and the photovoltaic element is formed. Is improved.

The seven samples thus obtained were designated AM-1.
5 was measured under a solar simulator to evaluate the conversion efficiency of a solar cell as an example of a photovoltaic element. Table 4 shows the results. The following can be seen from Table 4. That is, (1) When a smooth metal layer (with unevenness of 1000 ° or less) and a transparent layer having an uneven structure are combined (Samples 6a and 6
c, 6d, 6g) Conversion efficiency was improved. (2) Although there was almost no difference in the conversion efficiency between the samples 6a, 6c, 6d and 6g, the photovoltaic effect was observed when the transparent layer was one (6c, 6d) and two (6a, 6g). The yield of the power element is about 70% and about 95%, respectively, and the reliability is clearly improved in the two-layer configuration (the yield is based on the unit area (1
A photovoltaic element having a shunt resistance of 200 Ω or more per cm ² ) is accepted, and a shunt resistance less than 200 Ω is rejected.

This is because, when a concave-convex structure is formed in the transparent conductive layer, a portion where the concave portion is locally large occurs in one layer,
As a result, the metal layer was partially exposed, and when a photovoltaic element was fabricated, it is considered that an electrical short circuit occurred through the location. On the other hand, when two layers are used, it is considered that the exposed portion is effectively covered with the second layer, the occurrence rate of the electric short circuit is reduced, and the yield is improved.

(Experiment 7) In Experiment 6, Sample 7a was prepared in the same manner as Sample 6a, except that the thickness of the first layer of ZnO was 10,000 °, and then the substrate was immersed in a 10% acetic acid aqueous solution at room temperature for 1 minute. Obtained.

Next, a sample 7b was obtained in the same manner as the sample 7a, except that the thickness of the first layer ZnO was 25000 °.

Next, a sample 7c was obtained in the same manner as the sample 7b, except that the substrate was immersed in a 10% acetic acid aqueous solution at room temperature for 90 seconds. Next, except that the time for immersing the substrate in a 10% acetic acid aqueous solution at room temperature was set to 3 minutes, the sample 7 was treated in the same manner as the sample 7b.
d was obtained.

According to the SEM observation, the erosion of the acetic acid aqueous solution increased according to the immersion time of the unevenness of the uneven structure of the first ZnO transparent conductive film.

In Samples 7a and 7d, immediately after immersion in the acetic acid aqueous solution, the exposed portion of the metal layer was observed by SEM in some places. However, the exposed portion of the metal layer was deposited by depositing the second ZnO transparent layer. Not observed. Table 5 shows the measurement results of the conversion efficiencies of the four samples AM-1.5. Although high conversion efficiencies were obtained in Samples 7a, 7b and 7c, Sample 7
No high conversion efficiency was obtained with d.

(Experiment 8) Sample 8a was obtained in the same manner as in Sample 6a, except that no transparent layer was deposited in Experiment 6.

As a result of measuring the conversion efficiency of Sample 8a with AM-1.5, the conversion efficiency was 2.2%. Then, as a result of micro Auger analysis of the a-Si layer of the sample 8a, aluminum atoms were detected.

It was confirmed that when the metal layer and the semiconductor layer were in direct contact, the metal atoms diffused into the semiconductor layer.

(Substrate and Metal Layer) Various metals are used for the substrate. Among them, stainless steel plate, zinc steel plate, aluminum plate, copper plate and the like are preferable because of their relatively low price. These metal plates may be cut into a certain shape and used, or may be used in a long sheet-like form depending on the plate thickness. In this case, since it can be wound in a coil shape, it is suitable for continuous production, and storage and transportation are easy. Depending on the application, a crystal substrate such as silicon or a glass or ceramic plate may be used. The surface of the substrate may be polished, but may be used as it is when the finish is good, such as a stainless steel plate subjected to a bright annealing treatment.

In the case of a substrate having a low light reflectance as it is, such as stainless steel or a zinc steel plate, or a substrate made of a material having a low conductivity as it is, such as glass or ceramics, a substrate such as silver, aluminum, or copper is further provided thereon. By providing a metal layer with high reflectivity, it can be used as a substrate. However, when used as a back reflection layer, the short wavelength component of the spectrum of sunlight is already absorbed in the semiconductor layer, so it is sufficient if the reflectance is higher for light of longer wavelength than that. . Which wavelength or higher the reflectance should be higher depends on the light absorption coefficient and the film thickness of the semiconductor used.
For example, in the case of a-Si having a thickness of 4000 °, this wavelength is about 6000 °, and copper can be suitably used (see FIG. 4).

For deposition of the metal layer, a vacuum deposition method using resistance heating or an electron beam, a sputtering method, an ion plating method, a CVD method, a plating method, or the like is used. A case of a sputtering method will be described as an example of a film formation method. FIG.
Shows an example of a sputtering apparatus. Reference numeral 401 denotes a deposition chamber, which can be evacuated by an exhaust pump (not shown). Inside this, a gas introduction pipe 402 connected to a gas cylinder (not shown) is provided.
As a result, an inert gas such as argon (Ar) is introduced at a predetermined flow rate, the opening of the exhaust valve 403 is adjusted, and the inside of the deposition chamber 401 is set to a predetermined pressure. The substrate 404 is fixed to the surface of the anode 406 provided with the heater 405 inside. A target 4 is provided on the surface facing the anode 406.
A cathode electrode 408 to which the reference numeral 07 is fixed is provided. Target 407 is a block of metal to be deposited. Usually, it is a pure metal having a purity of about 99.9% to 99.999%, but a specific impurity may be introduced in some cases. The cathode electrode is connected to a power supply 409.
The power supply 409 provides radio frequency (RF) or direct current (D
A high voltage of C) is applied to generate plasma 410 between the cathode and the anode. The metal atoms of the target 407 are deposited on the substrate 404 by the action of the plasma. In a magnetron sputtering apparatus in which a magnet is provided inside the cathode 408 to increase the plasma intensity, the deposition rate can be increased.

(Transparent Layer and its Uneven Structure) The transparent layer is made of ZnO, In ₂ O ₃ , SnO ₂ , CdO, Cd
Oxides such as SnO ₄ and TiO are often used.
(However, the composition ratio of the compound shown here does not always match the actual state.) In general, the higher the light transmittance of each transparent layer is, the better, but the light in the wavelength range absorbed by the semiconductor is good. Need not be transparent. It is preferable that the transparent layer has a resistance in order to suppress a current caused by a pinhole or the like. On the other hand, the effect of the series resistance loss due to this resistance on the conversion efficiency of the photovoltaic element must be within a negligible range. From such a viewpoint, the unit area (1c
The range of resistance per m ² ) is preferably 10 ⁻⁶ to 10
Ω, more preferably 10 ^{-5 to} 3 Ω, most preferably 10 Ω
^{−4 to} 1Ω. The thickness of the transparent layer is preferably as small as possible from the viewpoint of transparency, but is required to be 500 ° or more from the viewpoint of multiple interference. Further, in order to obtain a surface uneven structure, an average film thickness of 1000 ° or more is required. In some cases, a higher film thickness is required from the viewpoint of reliability. In the case of a plurality of layer regions, an average film thickness of 1000 ° or more is required in order to obtain the uneven structure on the surface of the first layer region.

Means for forming the uneven structure on the first layer is as follows:
The temperature may be increased when a layer in contact with the metal layer is deposited. In this case, the first layer formation temperature T ₁ is appropriately changed depending on a material, an apparatus, and the like used for forming the first layer. For example, for example, DC using a ZnO target (purity 99.9%) is used.
In the magnetron sputtering method, T ₁ > 200 ° C. is preferable. The surface shape of such oxides used in the above transparent layer, since the forming temperature T advances the higher uneven structure, the relationship of the n-layer region T ₁ and T _n when the formation temperature is T _n of, T ₁ > T _n .

As another means for forming the concavo-convex structure, there is a method in which after depositing the first layer, the surface thereof is immersed in an acid, alkali or salt aqueous solution. Depending on the length of the dipping time, a desired uneven structure can be obtained. As the acid used at this time,
Acetic acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid and the like are often used as alkalis, and sodium hydroxide, potassium hydroxide and aluminum hydroxide are often used as alkalis, and iron chloride and aluminum chloride are often used as salts.

As another means for forming the concavo-convex structure, there is a method in which after depositing the first layer, the surface of the first layer is subjected to reverse sputtering or the like and the transparent layer whose concavo-convex structure is to be formed is hit with plasma, ions or the like. The concavo-convex structure forming means can be relatively easily performed, and is suitable for a badge type manufacturing method. The transparent layers after the second layer region must have a thickness that does not impair the concavo-convex structure formed by the first layer, and furthermore, 500-3000 in consideration of the thickness of the semiconductor layer to be deposited.
Å, preferably 500Å-2500Å, and more preferably 500Å-2000Å.

[0069] forming temperature T _n of at least one of the n layer region in the second layer region later, it may for coating irregularities of the first layer region as completely as possible is as low as possible good conditions to produce a smooth surface . The n-th formation temperature T _n varies as appropriate depending on the material, apparatus, and the like used for forming the n-th transparent layer. For example, in a DC magnetron sputtering method using a ZnO target (purity 99.9%), T _n < 2
00 ° C is preferred.

Further, in another example including a plurality of layer regions, as one of the first forming means for forming the uneven pitch of the first layer of 3000 ° or less, the first forming temperature T ₁ may be set as low as possible. The first formation temperature T ₁ is appropriately changed depending on a material, an apparatus, and the like used for forming the first layer.
For example, in a DC magnetron sputtering method using a ZnO target (purity 99.9%), T ₁ <200
C is preferred.

In the transparent layer formed by the second and subsequent forming means, the n-th layer region having an uneven structure requires an average film thickness of 1000 ° or more in order to obtain the uneven structure. Further, as one means for forming the uneven structure,
It is _preferable to increase the n-th forming temperature Tn. N-th forming temperature T
_n changes as appropriate depending on the material, apparatus, and the like used for forming the n-th layer region.
(9.9%), it is preferable that T _n > 200 ° C. in the DC magnetron sputtering method. The surface shape of such oxides used in the above transparent layer, since the forming temperature T advances the higher uneven structure, the relationship of T ₁ and T _n is T ₁ <
The T _n.

As another means for forming the concavo-convex structure, there is a method in which after depositing the first layer, the surface is immersed in an acid, alkali or salt aqueous solution. Depending on the length of the dipping time, a desired uneven structure can be obtained. As the acid used at this time,
Acetic acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid and the like are often used as alkalis, and sodium hydroxide, potassium hydroxide and aluminum hydroxide are often used as alkalis, and iron chloride and aluminum chloride are often used as salts.

As another means for forming a concave-convex structure, a transparent layer of which a desired concave-convex structure is to be formed among the transparent layers formed after the second layer region is deposited, and the surface thereof is formed by sputtering or the like. There is a method of hitting a transparent layer to have an uneven structure with plasma, ions, or the like. This uneven structure forming means can be performed relatively easily and is suitable for a badge type manufacturing method.

The total film thickness of the transparent layer deposited above the n-th layer region having an uneven structure in the layer regions formed by the second and subsequent forming means has a thickness that does not impair the uneven structure. In consideration of the thickness of the semiconductor, the total thickness is 500-3000, preferably 500-2500, and more preferably 500-20.
00 °.

For deposition of the transparent layer, a vacuum deposition method using resistance heating or an electron beam, a sputtering method, an ion plating method, a CVD method, a spray coating method, or the like is used. A sputtering method will be described as an example of a film formation method.
Also in this case, the sputtering apparatus shown in FIG. 6 can be used. Note that in the case of an oxide, there are a case where the oxide itself is used as a target and a case where a metal (Zn, Sn, or the like) target is used. In the latter case, it is necessary to flow oxygen into the deposition chamber simultaneously with Ar (this is called a reactive sputtering method).

An example of the deposition conditions and the concavo-convex structure forming conditions will be described. A 5 cm × 5 cm 1 mm thick stainless steel plate (sus430) having a polished surface was used as a substrate. When a ZnO target having a diameter of 6 inches and a purity of 99.9% was used, the distance between target substrates was set to 5 cm, Ar was flowed at 10 sccm, the pressure was maintained at 1.5 mTorr, and a DC voltage of 500 V was applied. Ampere current flowed. In this state, discharging was continued for 5 minutes. The substrate temperature was changed to room temperature, 100 degrees, 200 degrees, and 300 degrees to obtain samples 14a, 14b, 14c, and 14d. Table 6 summarizes the appearance of these samples and the results of SEM observation. Increasing the temperature changes the surface morphology of ZnO. In the samples 14c and 14d where turbidity occurred, crater-shaped concave portions were observed on the surface, and this is considered to be the cause of turbidity. Next, an example of deposition conditions and conditions for forming a concavo-convex structure when the first layer surface has a concavo-convex structure, which includes a plurality of layer regions.

The same applies until the application of the pressure and the DC voltage.
The discharge was continued for 15 minutes. The substrate temperature is set to room temperature, 100
Degrees, 200 degrees, and 300 degrees, samples 15a, 15b,
15c and 15d. Increasing the temperature changes the surface morphology of ZnO. In the samples 15c and 15d where turbidity occurred, crater-shaped concave portions were observed on the surface, and this is considered to be the cause of turbidity. Further, the samples prepared at a substrate temperature of 200 ° C. were immersed in a 10% acetic acid aqueous solution for 1 minute and 1.5 minutes, and the samples were designated as 15e and 15f, respectively. Table 7 summarizes the results of SEM observation of the appearance of these samples.

Samples 15a to 15f obtained in this manner
Again by the sputtering method under the same conditions as above.
When nO was deposited, a deposited film having substantially the same uneven surface as that of 15a to 15f was maintained. (However, the discharge time is 1.5 minutes).

Further, examples of deposition conditions and conditions for forming a concavo-convex structure when a plurality of layer regions are formed and at least one of the second and subsequent layer regions has a concavo-convex structure.

The same applies to the above pressure and DC voltage application.
In this state, the discharge was continued for 1.5 minutes. The substrate temperature was room temperature.

Next, ZnO in the second layer region was deposited again by the same sputtering method. However, the discharge time was 15 minutes, and the substrate temperature was changed to room temperature, 100 ° C., 200 ° C., and 300 ° C. to obtain samples 16a, 16b, 16c, and 16d. Table 8 summarizes the appearance of these samples and the results of SEM observation.

The light confinement may be caused by scattering of light in the metal layer when the metal layer itself has an uneven structure. However, when the metal layer is smooth and the transparent layer has an uneven structure, It is conceivable that scattering is caused by the phase of incident light being shifted between a concave portion and a convex portion on the surface of the semiconductor and / or the interface with the transparent layer. 3000-20 preferably as pitch
About 000Å, more preferably 4000 to 15000
Å, and preferably the height difference is 500 to 20,000
Å, more preferably 700〜１０10000Å. From this viewpoint, the samples 6c, 6d, 14c, 14d, 14e, 1
At 4f, 15c, and 15d, it can be said that a nearly ideal uneven structure is obtained. Further, when the surface of the semiconductor has an uneven structure similar to that of the transparent layer, scattering of light due to the phase difference of light easily occurs, and the effect of the light trap is high.

In order to control the specific resistance of the transparent layer, an appropriate impurity may be added. As the transparent layer of the present invention, the conductive oxide as described above may have a specific resistance that is too low. In order to make the whole thinner, it is preferable to add an impurity as an impurity to appropriately increase the resistance. For example, an appropriate amount of an acceptor-type impurity (eg, Cu in ZnO, Al in SnO ₂ , etc.) is added to a transparent layer, which is an n-type semiconductor, to improve the intrinsic property and the resistance.

When the transparent layer is composed of a plurality of layer regions, an appropriate impurity may be introduced into each of the layer regions. A moderate resistance can be given as a whole.

Since the intrinsic transparent layer is generally hard to be etched by an acid or alkali, it is hard to be immersed in a chemical used for patterning a semiconductor layer or an ITO layer in a later step of manufacturing a solar cell. Another advantage is that the durability of the solar cell when used in a high-temperature, high-humidity environment for a long period of time is increased.

However, in the case where etching using a solution of an acid, an alkali, a salt or the like is used to form the concave-convex structure of the transparent layer, if the transparent layer is made intrinsic, the working efficiency is undesirably reduced. In this case, after etching the transparent layer formed without initiating by the introduction of impurities, and then laminating the insulted transparent layer, the entire transparent layer has moderate resistance and chemical resistance. And a solar cell with high durability. In order to add impurities to the transparent film, desired impurities may be added to the evaporation source or the target as described in Experiments 3 and 4. In particular, in the case of the sputtering method, a small piece of a material containing impurities is placed on the target. May be placed.

[0087]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 In this example, a pin-type a-Si (provided that the metal layer 102 is not provided) photovoltaic element having the structure shown in the schematic sectional view of FIG. 1 was manufactured. 5x with polished surface
A ZnO layer 1 having an average thickness of 4000 ° at a substrate temperature of 250 ° C. using a ZnO target with 5% Cu added to an Al plate 101 having a thickness of 5 cm and a thickness of 1 mm using the apparatus shown in FIG.
03 was deposited. The surface of ZnO had an uneven structure.

Subsequently, the substrate on which the lower electrode was formed was mounted on a commercially available capacitively coupled high-frequency CVD apparatus (C
HJ-3030). Rough evacuation and high vacuum evacuation operations were performed by an evacuation pump through the evacuation pipe of the reaction vessel. At this time, the temperature of the substrate was controlled by a temperature control mechanism so as to be 250 ° C. When the sufficiently evacuated is performed, SiH ₄ 300 sccm from the gas introducing pipe, SiF ₄ 4
sccm, PH ₃ / H ₂ (1% H ₂ dilution) 55 sccm,
40 sccm of H ₂ was introduced, the opening of the throttle valve was adjusted, the internal pressure of the reaction vessel was maintained at 1 Torr, and when the pressure was stabilized, 200 W of power was immediately supplied from the high frequency power supply. The plasma was maintained for 5 minutes. Thereby, the n-type a-Si layer 105 was formed on the transparent layer 103. After exhausting again, this time the Si
H ₄ 300 sccm, SiF _{4 4} sccm, H ₂ 40 sc
cm, the opening degree of the throttle valve was adjusted, the internal pressure of the reaction vessel was maintained at 1 Torr, and when the pressure was stabilized, 150 W of electric power was immediately supplied from a high-frequency power source to maintain the plasma for 40 minutes. As a result, i-type a
The -Si layer 106 was formed on the n-type a-Si layer 105. After exhausting again, this time the SiH
₄ 50 sccm, BF ₃ / H ₂ (1% H ₂ dilution) 50 sccc
m, H ₂ 500 sccm was introduced, the opening of the throttle valve was adjusted, the internal pressure of the reaction vessel was maintained at 1 Torr, and when the pressure was stabilized, 3
The power of 00W was turned on. The plasma was maintained for 2 minutes. As a result, the p-type μc-Si layer 107 becomes i-type a-Si
Formed on layer 106. Next, the sample was taken out from the high-frequency CVD apparatus, ITO was deposited by a resistance heating vacuum evaporation apparatus, and then a paste containing an aqueous solution of iron chloride was printed to form a desired pattern of the transparent electrode 108. Further, an Ag paste was screen-printed to form a current collecting electrode 109, thereby completing a solar cell. In this way, 10 samples were prepared, and AM
When the characteristics were evaluated under irradiation with 1.5 (100 mW / cm ² ) light, an excellent conversion efficiency of 9.5 ± 0.2% in terms of photoelectric conversion efficiency was obtained with good reproducibility. Further, these solar cells were allowed to stand for 1000 hours in an environment of a temperature of 50 ° C. and a humidity of 90%, but the conversion efficiency was 9.2 ± 0.5%, and almost no decrease was observed.

Example 2 In this example, a pin-type a-SiGe photovoltaic element having the structure shown in the schematic sectional view of FIG. 1 was manufactured. 5x5cm thickness 1mm with polished surface
A copper layer 102 having a smooth surface and a thickness of 1500 ° was formed on a stainless steel plate 101 by plating. Next, Zn containing 1.0% of Cu was blown away in an oxygen atmosphere at a substrate temperature of 350 ° C. by an ion plating method, and a ZnO layer having an average thickness of 1 μm and an uneven surface was deposited. .

Subsequently, Si ₂ H ₆ was applied for 50 seconds as an i-layer.
ccm, 10sccm the GeH _4, the H ₂ 300sccm
And kept the internal pressure of the reaction vessel at 1 Torr,
The same procedure as in Example 1 was repeated except that a-SiGe deposited by applying a power of W and maintaining the plasma for 10 minutes was used.
Zero samples were prepared. AM1.5 (100m
(W / cm ² ) When the characteristics were evaluated under light irradiation, an excellent conversion efficiency of 8.5 ± 0.3% in photoelectric conversion efficiency was obtained with good reproducibility.

(Example 3) Using the apparatus shown in FIG. 7, a back reflection layer was continuously formed. Here, the substrate delivery chamber 603 has a cleaned width of 350 mm, a thickness of 0.2 mm,
A stainless steel sheet roll 601 having a length of 500 m is set. From here, the stainless sheet 602 passes through the metal layer deposition chamber 604 and the transparent layer deposition chamber 605 and is sent to the substrate winding chamber 606. The sheet 602 can be heated to a desired temperature by the substrate heaters 607 and 608 in each deposition chamber. Target 6 of deposition chamber 604
Reference numeral 09 denotes Al having a purity of 99.99%, and an Al layer is deposited on the sheet 602 by DC magnetron sputtering. The target 610 in the deposition chamber 605 has a purity of 99.5%.
(0.5% is Cu), and a ZnO layer is successively deposited by DC magnetron sputtering.
There are four targets 610 in relation to the deposition rate and the desired film thickness.

A back reflection layer was formed using this apparatus. The sheet feeding speed was set to 20 cm / min, and the substrate temperature during ZnO deposition was set to 25 using only the substrate heater 608.
It was adjusted to be 0 degrees. Ar flow, pressure 1.5m
At Torr, a DC voltage of 500 V was applied to each cathode. A current of 6 Amps flowed through the target 609, and a current of 4 Amps flowed through the target 610. Examination of the wound sheet revealed that the thickness of the Al layer was 1600 ° and Zn
The thickness of the O layer was 3800 ° on average, and the surface of the ZnO layer was cloudy.

The a-Si / a- layer having the structure shown in FIG.
A SiGe tandem photovoltaic device was formed. Where 70
1 is a substrate, 702 is a metal layer, 703 is a transparent layer, 704 is a bottom cell, and 708 is a top cell. Further 70
5, 709 are n-type a-Si layers, and 707, 711 are p-type μ-layers.
c-Si, 706 is an i-type a-SiGe layer, and 710 is an i-type a-Si layer. These semiconductor layers are described in U.S. Pat.
It was manufactured continuously using a roll-to-roll type film forming apparatus as described in 492,181. 712
Is a transparent electrode and was deposited by a sputtering apparatus similar to the apparatus of FIG. 713 is a current collecting electrode. Sheet 602 after patterning the transparent electrode and forming the collecting electrode
Was cut. In this way, all the processes were continuously processed, and a mass production effect was obtained.

In this way, 100 samples were prepared and the AM
When the characteristics were evaluated under irradiation with 1.5 (100 mW / cm ² ) light, an excellent conversion efficiency of 11.2 ± 0.2% in photoelectric conversion efficiency was obtained with good reproducibility. In addition, these photoelectric conversion elements were placed in an environment at a temperature of 50 ° C. and a humidity of 90% for 1000
After standing for a while, the conversion efficiency was 10.8 ± 0.6%, and almost no deterioration was observed. In addition, another 100 sheets created by this method are exposed to light equivalent to
After irradiation for an hour, the deterioration due to light was small at 10.5 ± 0.3%. This is because the tandem configuration effectively absorbs light having a longer wavelength, thereby increasing the output voltage. This is also because deterioration of the semiconductor layer under light irradiation can be reduced. Thus, a highly reliable photovoltaic element having high conversion efficiency combined with the effect of the back reflection layer of the present invention was obtained.

Example 4 A back reflection layer was formed in the same manner as in Example 1 except that a Cu plate having a polished surface was used as a substrate. On this substrate and the substrate on which the ZnO layer was not deposited, Cu was deposited by 0.2 μm and indium (In) was deposited by 0.4 μm by sputtering. Next, the sample was transferred to a quartz glass bell jar and heated to 400 ° C., and hydrogen selenide (H ₂ Se) diluted to 10% with hydrogen was passed through the bell jar, and CuInSe ₂ (CIS)
Was formed. A CdS layer was again deposited thereon by 0.1 μm by a sputtering method and then annealed at 250 ° C. to form a p / n junction. A transparent electrode and a current collecting electrode were formed thereon in the same manner as in Example 1.

This photovoltaic element was set to AM 1.5 (100 m
W / cm ² ) When the characteristics were evaluated under light irradiation, Z
The photovoltaic device having an nO layer provided excellent conversion efficiency of 9.5%, whereas the photovoltaic device without ZnO exhibited poor characteristics of 7.3%. Is a-
It has been found that the present invention is also effective for semiconductors other than Si.

Example 5 In this example, a pin-type a-Si (without the metal layer 102) photovoltaic element having the structure shown in the schematic sectional view of FIG. 2 was produced. An Al plate 101 having a thickness of 5 × 5 cm and a thickness of 1 mm was polished to a substrate temperature of 30 using a ZnO target by the apparatus shown in FIG.
ZnO layer 103a having an average thickness of 4000 ° at 0 degrees
Was deposited. The surface of ZnO had an uneven structure. Next, after lowering the substrate temperature to room temperature, a ZnO layer 103b having a thickness of 500 ° was deposited.

Example 1 was placed on the back reflection layer thus obtained.
Similarly to the case of the pin type a-Si semiconductor layer 104 and the transparent electrode 1
08, the collecting electrode 109 was formed to complete the photovoltaic element. In this way, ten samples were prepared, and AM1.5 (1
(00mW / cm ² ) When the characteristics were evaluated under light irradiation, an excellent conversion efficiency of 9.7 ± 0.2% in photoelectric conversion efficiency was obtained with good reproducibility. In addition, these photovoltaic elements
It was left for 1000 hours in an environment at a temperature of 50 ° C. and a humidity of 90%, but the conversion efficiency was 9.4 ± 0.5%, which was hardly reduced.

Example 6 In this example, a pin-type a-SiGe photovoltaic element having the structure shown in the schematic sectional view of FIG. 2 was manufactured. 5x5cm thickness 1mm with polished surface
A copper layer 102 having a smooth surface and a thickness of 1500 ° was formed on a stainless steel plate 101 by plating. Next, Zn was blown in an oxygen atmosphere at a substrate temperature of 350 ° C. by an ion plating method to deposit a ZnO layer having an average thickness of 1 μm and a surface having an uneven structure. next,
The substrate was immersed in a 10% acetic acid aqueous solution for 45 seconds, dried in a constant temperature bath at 80 ° C. for 20 minutes, and then set to a substrate temperature of 700 ° C. by the ion plating method again.
Layers were deposited.

Subsequently, Si ₂ H ₆ was applied for 50 seconds as an i-layer.
ccm, 10sccm the GeH _4, the H ₂ 300sccm
And kept the internal pressure of the reaction vessel at 1 Torr,
The same procedure as in Example 1 was repeated except that a-SiGe deposited by applying a power of W and maintaining the plasma for 10 minutes was used.
Zero samples were prepared. AM1.5 (100m
(W / cm ² ) When the characteristics were evaluated under light irradiation, an excellent conversion efficiency of 8.7 ± 0.3% in photoelectric conversion efficiency was obtained with good reproducibility.

(Example 7) A back reflection layer was continuously formed using the apparatus shown in FIG. Here, the substrate delivery chamber 603 has a cleaned width of 350 mm, a thickness of 0.2 mm,
A stainless steel sheet roll 601 having a length of 500 m is set. From here, the stainless sheet 602 is sent to the substrate winding chamber 606 via the metal layer deposition chamber 604, the first layer deposition chamber 605a, and the second layer area deposition chamber 605b. The sheet 602 is supplied to the substrate heater 60 in each deposition chamber.
7, 608a, 608b can be heated to a desired temperature. The target 609 in the deposition chamber 604 is made of Al having a purity of 99.99%, and an Al layer is deposited on the sheet 602 by DC magnetron sputtering. The targets 610a and 610b of the deposition chambers 605a and 605b are made of ZnO having a purity of 99.9%, and a ZnO layer is continuously deposited by DC magnetron sputtering. Deposition rate,
Due to the desired film thickness, the target 610a is formed of four sheets, and the target 610b is formed of one sheet having a half width.

Using this apparatus, a back reflection layer was formed. The sheet feeding speed was set to 20 cm / min, and the substrate temperature during ZnO deposition was set to 250 using only the substrate heater 608a.
Adjusted to the degree. The heater 608b was not used. Ar was flowed to a pressure of 1.5 mTorr,
A DC voltage of 500 V was applied to each cathode. A current of 6 A flowed through the target 609, a current of 4 A flowed through the target 610a, and a current of 2 A flowed through the target 610b. Examination of the wound sheet revealed that the thickness of the Al layer was 160
0 °, the average thickness of the ZnO layer is 4300
And the surface of the ZnO layer was clouded.

The a-Si / a structure shown in FIG.
-A SiGe tandem photovoltaic element was formed. Where 7
01 is a substrate, 702 is a metal layer, 703 is a transparent layer, 704
Is a bottom cell and 708 is a top cell. Further 70
3a is ZnO of the first layer, 703b is Zn of the second layer region.
O, 705 and 709 are n-type a-Si layers, 707 and 711
Is a p-type μc-Si, 706 is an i-type a-SiGe layer, 71
0 is an i-type a-Si layer. These semiconductor layers are rolled as described in U.S. Pat. No. 4,492,181.
It was manufactured continuously using a two-roll type film forming apparatus. A transparent electrode 712 is deposited by a sputtering apparatus similar to the apparatus shown in FIG. 713 is a current collecting electrode. After patterning the transparent electrode and forming the current collecting electrode, the sheet 602 was cut. In this way, all the processes were continuously processed, and a mass production effect was obtained.

In this way, 100 samples were prepared, and the AM
When the characteristics were evaluated under irradiation with 1.5 (100 mW / cm ² ) light, an excellent conversion efficiency of 11.5 ± 0.2% in photoelectric conversion efficiency was obtained with good reproducibility. In addition, these photovoltaic elements were put in an environment of 50 ° C. and 90% humidity for 1000
After standing for a while, the conversion efficiency was 11.0 ± 0.6%, and almost no deterioration was observed. In addition, another 100 sheets created by this method are exposed to light equivalent to
After irradiation for an hour, the deterioration due to light was small, at 10.7 ± 0.3%. This is because the tandem configuration effectively absorbs light having a longer wavelength, thereby increasing the output voltage. This is also because deterioration of the semiconductor layer under light irradiation can be reduced. Thus, a highly reliable photovoltaic element having high conversion efficiency combined with the effect of the back reflection layer of the present invention was obtained.

Example 8 A back reflection layer was formed in the same manner as in Example 5, except that a Cu plate having a polished surface was used as a substrate. On this substrate and the substrate on which the ZnO layer in the second layer region was not deposited, Cu was deposited by 0.2 μm and indium (In) was deposited by 0.4 μm by sputtering. Next, the sample was transferred to a quartz glass bell jar and heated to 400 ° C., and hydrogen selenide (H ₂ Se) diluted to 10% with hydrogen was flowed into the bell jar, and CuInS
A thin film of e ₂ (CIS) was formed. A CdS layer was again deposited thereon by 0.1 μm by a sputtering method and then annealed at 250 ° C. to form a p / n junction. A transparent electrode and a current collecting electrode were formed thereon in the same manner as in Example 5.

This photovoltaic element was used for AM1.5 (100 m
W / cm ² ) When the characteristics were evaluated under light irradiation, Z
The conversion efficiency of the photovoltaic device having two nO layers is 9.
In the case of 6% and one layer, excellent conversion efficiency was obtained together with 9.5%. However, when the IV characteristics were measured, the photovoltaic element having a shunt resistance per unit area product and 200Ω or less was 4% in the case of the two-layer region and 28% in the case of the one-layer region.
%, And higher reliability was obtained in the case of the two-layer region.

Further, an exposed portion of the metal layer is generated at the stage of forming the concave-convex structure for realizing an effective optical trapping effect, and diffusion of metal atoms from the exposed portion to the semiconductor layer is performed by providing a second layer region. Can be prevented. Further, by providing the second layer region with a leakage current between the exposed portion and the upper electrode through a short-circuited portion in the semiconductor partially formed, the frequency is extremely reduced, and the photovoltaic element is formed. Is improved.

Example 9 In this example, a pin-type a-Si (without the metal layer 102) photovoltaic element having the structure shown in the schematic sectional view of FIG. 3 was produced. A ZnO layer 103c having a thickness of 1000 ° was deposited on a 5 × 5 cm 1 mm thick Al plate 101 having a polished surface at a substrate concentration of room temperature using a ZnO target by the apparatus shown in FIG. An average thickness of 30 at a substrate temperature of 300 degrees
A ZnO layer 103d of 00 Å was deposited. Zn
The surface of O had an uneven structure.

Example 1 was formed on the back reflection layer thus obtained.
Similarly to the case of the pin type a-Si semiconductor layer 104 and the transparent electrode 1
08, the collecting electrode 109 was formed to complete the photovoltaic element. In this way, ten samples were prepared, and AM1.5 (1
(MW / cm ² ) When the characteristics were evaluated under light irradiation, an excellent conversion efficiency of 9.6 ± 0.2% in photoelectric conversion efficiency was obtained with good reproducibility. Further, these solar cells were allowed to stand for 1000 hours in an environment of a temperature of 50 ° C. and a humidity of 90%, but the conversion efficiency was 9.3 ± 0.5%, and almost no decrease was observed.

(Embodiment 10) In this embodiment, FIG.
A pin-type a-SiGe photovoltaic device having a configuration shown in FIG. 5x5cm thickness 1m with polished surface
1500 mm thick by plating on stainless steel 101
Formed a Cu layer 102 having a smooth surface. Then, Zn was blown off in an oxygen atmosphere at a substrate temperature of room temperature by an ion plating method, and a ZnO layer having a thickness of 800 ° was deposited.

Next, a ZnO layer having a thickness of 1 μm and a surface having an uneven structure was deposited again at a substrate temperature of 250 ° C. by the above-described ion plating method.

Subsequently, Si ₂ H ₅ was applied for 50 seconds as an i-layer.
ccm, 10sccm the GeH _4, the H ₂ 300sccm
And kept the internal pressure of the reaction vessel at 1 Torr,
The same procedure as in Example 9 was carried out except that a-SiGe deposited by applying a power of W and maintaining plasma for 10 minutes was used.
Zero samples were prepared. AM1.5 (100m
(W / cm ² ) When the characteristics were evaluated under light irradiation, an excellent conversion efficiency of 8.6 ± 0.4% in photoelectric conversion efficiency was obtained with good reproducibility.

Embodiment 11 In this embodiment, a solar cell as an example of a photovoltaic element manufactured by the method of the present invention is integrated with a storage battery such as a nickel cadmium storage battery (hereinafter referred to as a NiCd battery). This shows that the handling of the storage battery becomes extremely easy.

First, a 350 mm wide and 0.015 thick equivalent to JIS G3141 was used as a substrate for forming a solar cell.
mm-cold rolled steel sheet, a nickel-plated (5 micron thick) -coated sheet roll or the like was prepared and used in place of the stainless steel roll sheet 601 in exactly the same manner as in Example 3 except that a-Si / The transparent electrode 1521 on which the a-SiGe tandem photovoltaic element was formed was 58 mm × 10
After patterning to 0 mm to form a current collecting electrode 1513, it was cut into 70 mm x 110 mm. FIG. 11 shows a storage battery using the photovoltaic element thus manufactured as a battery case. FIG. 11A shows the external structure of the storage battery.

Here, a photovoltaic element is formed on the container 1501 as described above. A strong bottom plate is attached to withstand the pressure of the gas generated inside. No photovoltaic element is formed on the bottom plate, and this portion serves as a negative electrode terminal. FIG. 11B shows the internal structure of the storage battery. Inside the negative electrode plate 1504 and the positive electrode plate 1505
Are separated by a separator 1506 and wound. The electrode plates 1504 and 1505 are sintered bodies of an alloy of Ni and Cd, and the separator 1506 is a non-woven fabric made of nylon and is immersed in an electrolytic solution of potassium hydroxide. Negative electrode plate 15
04 is connected to a battery case 1501, and the positive electrode plate 1505 is connected to a positive electrode terminal 1502. Further, the inside is sealed by a synthetic resin sealing lid 1507 in which the packing 1508 is chewed so that the electrolyte does not leak. However, a safety valve 1509 is provided in the sealing lid 1507 to prevent an accident due to a rapid rise in pressure due to rapid charging and discharging.

Here, a lead wire is attached to the grid electrode 1513 on the surface of the photovoltaic element, and the grid electrode 1513 is connected to the positive terminal 1502 via the backflow prevention diode 1503. Further, in order to protect the surface of the photovoltaic element from damage, the battery case was covered with a cylindrical transparent heat-shrinkable sheet, and then heated with hot air to remove the positive electrode terminal 1505 and the bottom plate of the battery case. FIG. 12 shows an equivalent circuit in such a connection.
Shown in Here, the storage battery body 1510 is connected to a load 1 external to the negative terminal (bottom plate of the battery case) 1501 and the positive terminal 1502.
512.

Here, when light strikes the photovoltaic element 1511, a photovoltaic voltage of about 1.6 V is generated, and this voltage is
Join 510. Since the voltage of the storage battery is at most about 1.2 V, the backflow prevention diode 1503 is forward biased, and the storage battery 1510 is charged from the photovoltaic element 1511.

However, when light is not incident on the photovoltaic element 1511, the backflow prevention diode 1503 is biased in the reverse direction, so that current does not flow wastefully from the storage battery 1510. Also, when the battery is charged in a normal charger, the backflow prevention diode acts to prevent the unnecessary current from flowing through the photovoltaic element and charge the battery in the same manner as in a normal case. . In this way, the photovoltaic element storage battery of this embodiment is simply taken out of the battery case after discharging and left in a place exposed to strong light such as a window, or if the battery case lid of an electric appliance using the battery is transparent. If this is the case, it can be charged by light as it is, and since a special charger is unnecessary, it is particularly convenient for outdoor use. If the battery needs to be charged quickly, it can be charged with a conventional charger. In addition, the battery can be of any shape, such as a single-cell battery, a single-cell battery, a tank-type battery, etc., and can be used in many electric devices, and has a smart appearance.

Actually, these two batteries were put in a flashlight and used. When the batteries became dark and could not be used, they were taken out of the flashlight and placed side by side on a sunny window and charged.
When it was charged for a day on a sunny day and put back in the flashlight, it was fully charged and could be used again.

Embodiment 12 In general, as a solar cell for an artificial satellite, a compound crystal solar cell such as InP having a large output per unit area and little radiation damage is often used. However, since such a solar cell is generally used by connecting wafers, it has to be fixed on a panel. On the other hand, when launching an artificial satellite, the entire panel needs to be small and coherent, so a complex deployment-folding mechanism for a large number of panels is required, and even if the output per area of the solar cell is large, the overall The output per weight had to be low.

This example shows that a large output per unit weight can be obtained by a simple mechanism by using a solar cell as an example of a photovoltaic element manufactured by the method of the present invention as a power supply for an artificial satellite. It is.

First, as a substrate for forming a photovoltaic element, a width of 350 mm and a thickness of 0.15
a-Si / a-SiG in exactly the same manner as in Example 3 except that a sheet roll of an aluminum plate (including copper, manganese, etc.) was used in place of the stainless steel sheet 601.
An e-tandem photovoltaic element was manufactured, the transparent electrode 1512 was patterned into 105 mm × 320 mm, and a current collecting electrode 1513 was formed and then cut. Further, one end of the long side of each photovoltaic element was grinded to expose the substrate surface. Next, they were connected in series. This is shown in FIG.
That is, the photovoltaic element 1701 and the photovoltaic element 170
2 are connected from the back side by an insulating film 1703 such as a polystyrene film, a polyimide resin film, a cellulose triacetate resin film, and a trifluoride ethylene film resin while maintaining an interval of about 5 mm.
Between the current collecting electrode 1513 and the exposed surface 1704 of the substrate of the photovoltaic element 1702 with a copper sheet 1705 by heating and pressure bonding with copper ink, silver ink or the like. Here copper sheet 17
To prevent a short circuit from occurring between the substrate 05 and the substrate of the photovoltaic element 1701.
6 is over the edge. Further, a transparent Mylar film 1707 was adhered from above for protection.

Thus, a solar cell as an example of a sheet-like photovoltaic element having a length of about 20 m was obtained by connecting 200 photovoltaic elements in series. This photovoltaic element is configured as shown in FIG. Here, a rotatable shaft 1902 is attached to the main body 1901 of the satellite, and the shaft 1902 has sheet-like photovoltaic elements 1903, 19
04 etc. are wound. Reference numeral 1903 denotes a state in which the photovoltaic element is completely expanded, and 1904 denotes a state in which the photovoltaic element is half-wound. The current generated at the tip of the sheet-like photovoltaic element is connected to the artificial satellite body by a cable that can be wound simultaneously with the photovoltaic element (not shown). The sheet-like photovoltaic elements 1903 and 1904 and the cable can be freely deployed and wound by a drive system (not shown).

The system is used as follows. First, at the time of an artificial satellite meeting, a sheet-like photovoltaic element 1903,
Reference numeral 1904 denotes a state in which all are wound up. After the satellite is on board, the satellite is rotated slowly so that its axis of rotation points toward the sun. At the same time, when the sheet-shaped photovoltaic element is slowly drawn out, the sheet-shaped photovoltaic element is developed radially by the force of the centroid to generate power. When changing the orbit of the artificial satellite or recovering from the orbit for controlling the attitude, the sheet-like photovoltaic element is rewound by a motor or the like. After that, if necessary, it can be developed again to generate electricity. In the system composed of the six sheet-like photovoltaic elements, the output is 5 KW at the maximum and the total weight including the driving system is about 30 kg.
Therefore, a power generation system having a large output per weight can be constructed.

(Embodiment 13) This embodiment is an example in which a photovoltaic element manufactured by the method of the present invention is shaped into a waveform to provide a simple roofing material. The photovoltaic element manufactured by the method of Example 3 was cut into a length of 100 mm and a width of 900 mm, and each sheet was press-molded into a waveform. Length 1800mm, width 9
It was affixed to a corrugated plate made of a 00 mm vinyl chloride resin polyester resin or the like. FIG. 15 shows details of the connection between the photovoltaic elements. The photovoltaic element 2001 and the photovoltaic element 2002 are attached to the corrugated plate 2003 with an interval of 10 mm.

The grid electrode of the photovoltaic device 2001 and the exposed portion 2004 of the substrate of the photovoltaic device 2002 were connected by a copper sheet 2005. Reference numeral 2006 denotes an insulating film such as a polyimide resin sheet, a polyvinyl alcohol resin sheet, or a polystyrene film resin sheet for preventing a short circuit. Nail holes 2007 for fixing as roofing material
Are preliminarily opened on the corrugated plate 2003. Here, a large hole 200 is formed in the copper sheet 2005 to prevent a short circuit.
8 is open. However, nail holes are only drilled in the necessary series connection. From above, the PVA resin layer 200
9. The fluororesin layer 2010 was overlaid, pressed and heated, and shaped as one roof panel. FIG. 16 shows a state in which the roof is wiped using this. (Here roof material 2 shaped into one body
Reference numeral 102 denotes a small number of waveforms for the sake of simplicity. Here, the single photovoltaic element 2 of the roof material 2102
Reference numeral 101 shows the details thereof in FIG. Series connection unit 210
At 3, 2104, adjacent photovoltaic elements are connected. Here, a nail hole is drilled in the serial connection part 2103, and a nail hole is not drilled in the serial connection part 2104. Another roofing material 2
105 is fixed so as to overlap one waveform.
The photovoltaic element is not attached to the left end 2106 of the roofing material 2102. Further, since the corrugated plate is transparent, light is not blocked even if it is overlaid on the adjacent corrugated roofing material 2105. In this part, the output terminal from the left end of the roofing material 2102 is 21
After being connected to the output terminal on the right end of the terminal 05, the connection portion is sealed with an erosion resistant paint or the like for insulation of the terminal and is not exposed to the surface. In this way, the desired number of roofing materials are wiped and the series connection is completed at the same time.

If the series connection is not performed in some cases, a cable can be connected to the output terminal of each photovoltaic element, and the cable can be connected to the lower part 2108 of the waveform to take out the output to the outside. .

When eight sets of these four roofing materials connected in series were arranged in parallel and a roof inclined at 30 ° to the south was covered, an output of approximately 5 kW was obtained during the midsummer day, and it was used as a power source for ordinary households. Sufficient output was obtained.

(Embodiment 14) This embodiment is a photovoltaic device for an automobile used for driving a ventilation fan of an automobile, preventing discharge of a storage battery, and the like. Recently, photovoltaic elements for automobiles have begun to be put into practical use, but are installed in spaces such as sunroofs and high-speed running stabilizing rectifier plates so as not to impair the design of the automobile. However, there is no suitable space in a general specification car. In other words, the hood and ceiling are good in terms of being easily exposed to sunshine, but there is a problem in design, and the front and rear and side surfaces of the vehicle are easily damaged by contact or the like. Among them, the rear quarter pillar of the car has a moderate area, is less susceptible to damage, and has few design difficulties.

The present embodiment is a photovoltaic element for automobiles having a body mounted on a rear quarter pillar and a curved shape with a sense of one body, taking advantage of the characteristics of a photovoltaic element composed of a sheet-like metal substrate. It can be shown that can be made.

A photovoltaic element was produced in the same manner as in Example 12, and a single photovoltaic piece was produced by patterning a transparent electrode, forming a current collecting electrode, and cutting in accordance with the design of the car.

The components thus obtained were connected in series by the method of the thirteenth embodiment. FIG. 17 shows an example of a solar cell as an example of ten photovoltaic elements for an automobile having a storage battery with a voltage of 12 V. Here, the photovoltaic element piece located at the upper part of the column has a large length because the width of 2201 cannot be taken, and the photovoltaic element piece 2202 located at the lower part of the column is short because it is wide. The area is almost the same. Further, the longer the length of the photovoltaic element piece, the higher the density of the current collecting electrode 2203 so that the resistance loss of the transparent electrode can be sufficiently suppressed.

Although the color of the photovoltaic element is an important factor in the design, the thickness of the transparent electrode can be adjusted so as to match the color of other parts of the car. That is, when ITO is used as the transparent electrode, the thickness is generally 650 °, but in this case, it has an almost purple appearance. When the thickness of the transparent electrode is reduced to 450 ° to 500 °, yellowish green is exhibited, and when the transparent electrode is set to 500 ° to 600 °, the brown color is enhanced.
Further, when the thickness is 600 to 700 mm, the appearance becomes purple, and when the thickness is 700 to 800 mm, the color becomes more bluish, and the color can be adjusted to an appropriate color. However, when the thickness of ITO deviates from the standard, the output of the photovoltaic element decreases slightly. However, in the case of a tandem cell, when the ITO is thinned, the wavelength of light shifts to the short wavelength side, so the top cell is lightened. When the thickness is set and the ITO is thickened, on the contrary, the top cell is set thicker and the balance between the spectral sensitivities of the top cell and the bottom cell is adjusted, so that the decrease in efficiency can be minimized.

The photovoltaic element module 2302 for an automobile of this embodiment was mounted on the left and right rear quarter pillars of a four-door sedan vehicle 2301 (painted blue) shown in FIG. (FIG. 17 shows the one for the left side.) This was further assembled into a circuit whose outline is shown in FIG. Here, the left photovoltaic element 2401 and the right photovoltaic element 2402 are connected to the storage battery 2405 via backflow prevention diodes 2403 and 2404, respectively. When the sunshine is strong and the temperature inside the vehicle is high, the ventilation fan 2406 rotates. In order to perform this operation, when at least one of the signals from the current sensors 2409 and 2410 detecting the output current from the left and right photovoltaic elements is high and the signal from the temperature sensor 2408 is high Only the switch 2407 of the ventilation fan 2406 is turned on.

When the photovoltaic element module is provided in this manner, the room temperature, which had been above 80.degree. C. in the fine summer weather, can be lowered by about 30.degree. C., and left for one week or more in severe winter. Even so, the storage battery did not rise. Even after snowfall, the snow on the rear quarter pillar melts immediately after the solar radiation and can be charged immediately, so there was no problem even in regions with heavy snowfall.

[0136]

[Table 1]

[0137]

[Table 2]

[0138]

[Table 3]

[0139]

[Table 4]

[0140]

[Table 5]

[0141]

[Table 6]

[0142]

[Table 7]

[0143]

[Table 8]

[0144]

By using the back reflection layer of the present invention,
Since the light reflectance is increased and the light is effectively confined in the semiconductor, the absorption of light into the semiconductor is increased, and a photovoltaic device with high conversion efficiency can be obtained. In addition, metal atoms are less likely to diffuse into the semiconductor film, and even if there is a partial short circuit in the semiconductor, leakage current is suppressed by appropriate electrical resistance, and chemical resistance increases, resulting in new defects in the subsequent process. And a highly reliable photovoltaic element can be obtained. Further, such a back reflection layer can be manufactured as a part of a method having high productivity such as a roll-to-roll method. Thus, the present invention greatly contributes to the spread of photovoltaic elements.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a photovoltaic device according to an embodiment of the present invention, in which a single transparent layer is provided.

FIG. 2 is a diagram showing a cross-sectional structure of a photovoltaic device according to an embodiment of the present invention, in which a first layer region has a concave-convex structure.

FIG. 3 is a view showing a cross-sectional structure of a photovoltaic device according to an embodiment of the present invention, in which a second layer region has an uneven structure.

FIG. 4 shows Zn versus reflectance at the interface between silicon and metal.
The figure which shows the effect of O. (A) In the absence of ZnO, (b) Z
When there is nO.

FIG. 5 is a diagram showing an improvement in the spectral sensitivity of a photovoltaic element due to an uneven structure.

FIG. 6 is a view showing a structure of a sputtering apparatus suitable for manufacturing the back reflection layer of the present invention.

FIG. 7 is a view showing the structure of a sputtering apparatus suitable for producing a back reflection layer having one transparent layer according to the present invention.

FIG. 8 is a view showing a structure of a sputtering apparatus suitable for manufacturing a back reflection layer when the first layer region has an uneven structure according to the present invention.

FIG. 9 is a view showing a cross-sectional structure in a case where a transparent layer is a single layer region in another embodiment of the solar cell of the present invention.

FIG. 10 is a diagram showing a cross-sectional structure in a case where the first layer region has an uneven structure in another embodiment of the solar cell of the present invention.

11A and 11B are a diagram and a cross-sectional view in which a photovoltaic element of the present invention is used for a storage battery.

FIG. 12 is an equivalent circuit of an example of using a storage battery using the photovoltaic element of the present invention.

FIG. 13 shows a connection portion of a satellite battery using the photovoltaic device of the present invention.

FIG. 14 is a diagram of a satellite using the photovoltaic device of the present invention.

FIG. 15 is an enlarged view of a corrugated roofing material using the photovoltaic element of the present invention.

FIG. 16 is a corrugated roofing material using the photovoltaic element of the present invention.

FIG. 17 is a diagram of an embodiment of a module having a different collecting electrode density by changing the area using the photovoltaic element of the present invention.

FIG. 18 is a diagram of an automobile using the photovoltaic element of the present invention.

FIG. 19 is a diagram showing an equivalent circuit of an example of using an automobile using the photovoltaic element of the present invention.

[Explanation of symbols]

101, 701 Substrate 102, 702 Metal layer 103 Transparent layer 103a, 103c, 703a, 703c First layer region 103b, 103d, 703b, 703d Second layer region 105, 705, 709 n-type a-Si 106, 710 i-type a -Si 706 i-type a-SiGe 107,707,711 p-type μc-Si 108,712 transparent electrode 109,713 current collecting electrode 604 metal layer deposition chamber 605 transparent layer deposition chamber 605a, 605c first layer area deposition chamber 605b, 605d Second layer area deposition chamber 404, 602 Substrate 601 Roll of substrate 407, 609, 610, 610a, 610b, 610
c, 610d Targets 405, 607, 608, 608a, 608b, 608
c, 608d Substrate heater 409 Power supply 410 Plasma 1501 Battery case 1502 Positive electrode terminal 1503 Backflow prevention diode 1504 Negative electrode plate 1505 Positive electrode plate 1506 Separator 1507 Sealing lid 1508 Packing 1509 Safety valve 1510 Storage battery 1511 Photovoltaic element 1512 Transparent electrode 1513 Collector electrode Photovoltaic element 1702 Photovoltaic element 1703 Polyimide resin 1704 Substrate exposed surface 1705 Copper sheet 1706 Polyimide resin 1707 Mylar film 1901 Satellite main body 1902 Shaft 1903 Expanded photovoltaic element 1904 Rolled photovoltaic Device 2001 Photovoltaic device 2002 Photovoltaic device 2003 Corrugated plate 2004 Exposed part 2005 Copper sheet 2006 Polyimide resin 2007 Hole for fixing stainless steel 2008 Hole for copper sheet 2009 PVA resin 2010 Fluororesin 2101 Photovoltaic element unit 2102 Corrugated roof material 2103 Direct connection part with nail hole 2104 Direct connection part without nail hole 2105 Photovoltaic element 2106 Wave type Left end of roofing material 2107 Nail hole 2108 Lower corrugated part 2201 Photovoltaic element piece 2202 Photovoltaic element piece 2203, 2204 Current collecting electrode 2301 Car body 2302 Photovoltaic element 2401 Left photovoltaic element 2402 Right photovoltaic element 2403, 2404 Backflow prevention diode 2405 Storage battery 2406 Ventilation fan 2407 Ventilation fan switch 2408 Temperature sensor 2409, 2410 Sensor for detecting output current of photovoltaic element

Claims (2)

[Claims] 1. A substrate having a reflective metal surface, and a large number of fine crater-shaped concave portions formed, whereby Z
A photoelectric converter comprising an nO layer on the substrate, and a photoelectric conversion layer and an incident-light-side transparent conductive layer provided on the ZnO layer. 2. The photoelectric converter according to claim 1, wherein the ZnO layer is formed by setting the substrate temperature during film formation to a high temperature and then changing the substrate temperature to a low temperature.