JPH06204537A - Thin film semiconductor solar cell - Google Patents

Abstract

PURPOSE:To provide a thin film semiconductor solar cell having a rear surface reflecting layer which can obtain high conversion efficiency without influence of processing conditions. CONSTITUTION:An aluminum layer 102A is so formed as to exposed different type metal on a board 101 via fine holes 102B, a rear surface reflecting layer formed by providing a transparent layer 103 of a texture structure having an uneven part of a suitable pitch on a front surface is formed on the metal layer, and a thin film semiconductor junction 104 and a transparent electrode 108 are formed thereon. Thus, a part of the metal which is not affected by influence of partial oxidation is formed to utilize high reflectivity of the metal layer and an increase in series resistance is suppressed, and growth of the structure can be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film semiconductor solar cell having a back reflection layer.

[0002]

2. Description of the Related Art In a thin film semiconductor solar cell, an electrode formed on the surface of a thin film semiconductor is used in a structure in which sunlight is incident from the transparent substrate side in order to effectively utilize incident sunlight. , Silver (Ag), aluminum (A
1), copper (Cu), or other metal having a high reflectance, while in the case of a structure in which sunlight is incident from the front surface side of the semiconductor layer, the same metal layer is formed on the substrate and then the semiconductor layer is formed. Are known to form.

Further, in the case of the latter structure, when a transparent layer having appropriate optical properties is interposed between the metal layer and the thin film semiconductor layer, the reflectance is further increased by the multiple interference effect and the thin film semiconductor solar It is also known that the reliability of batteries can be improved. On the other hand, Japanese Examined Patent Publication No. 60-41878 discloses prevention of alloying between a semiconductor and a metal layer by using the transparent layer. Further, in US Pat. Nos. 4,532,372 and 4,598,306, when a transparent layer having an appropriate resistance is used, even if a short circuit portion occurs in the semiconductor layer, an excessive current is applied between the electrodes. There is a statement that it is possible to prevent the flow.

On the other hand, in the case of a thin film semiconductor solar cell, as another means for increasing the conversion efficiency, a method in which at least one interface between the front surface and the back surface reflection layer of the solar cell is made into fine unevenness (texture structure). There is. In such a method, sunlight is scattered at the interface between the front surface of the solar cell and the back surface reflection layer, and the scattered light is confined inside the semiconductor (optical trap effect), so that more effective light absorption in the semiconductor is achieved. This is what was planned.

In this case, when the substrate is transparent, the surface of the transparent electrode such as tin oxide (SnO ₂ ) on the substrate has a texture structure, and when sunlight is incident from the surface of the thin film semiconductor, A technique is known in which the surface of the metal layer used for the back surface reflection layer has a texture structure. In addition, M.
Hirasaka, K .; Suzuki, K .; Nakat
ani, M .; Asano, M .; Yano, H .; Okan
iwa et al. disclose a technique in which a texture structure for a back reflection layer is obtained by depositing Al while adjusting the substrate temperature and the deposition rate (Solar C).
ell Materials 20 (1990) pp9
9-110).

Further, there is also known a technique in which a method of providing a back reflection layer composed of two layers of a metal layer and a transparent layer and a method of forming a texture structure are combined. For example, U.S. Pat. No. 4,419,533 discloses a method of providing a back reflection layer having a textured structure on the surface of a metal layer and having a transparent layer formed thereon. It is intended to improve the conversion efficiency of solar cells.

[0007]

However, according to the knowledge of the present inventors, it has been found that the above-mentioned conventional technique cannot actually achieve the expected effect. In addition, depending on the deposition conditions of the thin film semiconductor, despite the provision of the transparent layer, there may be a case where the formed solar cell cannot have sufficient reliability for use under high temperature and high humidity. For this reason, the thin-film semiconductor solar cell may be produced at a low price, but it has not been widely used for solar power generation.

Specifically, the conventional backside reflecting layer has the following problems. (1) When a back surface reflection layer having a laminated structure of a metal layer and a transparent layer is used, the voltage-current characteristics of the solar cell are
A large decrease in F (fill factor) is seen. This is especially the case when Al is used as the metal. (2) When the transparent layer is textured, the reproducibility of its size (pitch of unevenness, etc.) is not necessarily good. Therefore, the Jsc of the solar cell cannot be increased as expected.

The present inventors conducted the following experiments in order to elucidate the causes of these problems. First, 1000 Å of Al was deposited on a 5 × 5 cm stainless steel plate (SUS430) by a DC magnetron sputtering method using a multi-target system device. The substrate temperature at this time was room temperature. In the same apparatus, the substrate temperature was raised to 250 degrees without breaking the vacuum, and 4000 Å ZnO was immediately deposited by the DC magnetron sputtering method.
According to SEM observation, the surface of Al was smooth and glossy, but the surface of ZnO was clouded because crater-shaped recesses having a diameter of about 4000 to 5000 Å were dense.
This is substrate 1.

Then, after depositing Al in the same apparatus, the substrate was once taken out from the apparatus, left for 1 day, and then set in the apparatus again to deposit ZnO. This is substrate 2. When the surface of ZnO of the substrate 2 was observed, the crater-shaped recesses had a diameter of about 2500 to 4000 Å and little cloudiness. Further, the substrate 3 was formed by the same procedure as that of the substrate 1 except that the substrate temperature was raised to 250 degrees after Al deposition and then left as it was (annealed) for 1 hour until the start of ZnO deposition. When the surface of ZnO of the substrate 3 was observed, the crater-shaped recesses had a diameter of about 4000 to 5000 Å and became cloudy.

Further, Cr electrodes were formed on these substrates and the resistance between them was evaluated. This resistance is
It was ² per 0.2Ω the substrate 1 1 cm, but in the substrate 2 1 cm ² per 5 [Omega, was 1 cm ² per 2Ω in the substrate 3. An n-type a-Si layer of 200 Å, SiH ₄ , and GeHe ₄ was formed on the three kinds of back reflection layers thus formed by glow discharge decomposition method using SiH ₄ and PH ₃ as source gases.
With the source gas as an i-type a-SiGe layer of 4000 Å, S
Using iH ₄ , BF ₃ , and H ₂ as source gases, p-type microcrystals (μ
c) A 100 Å Si layer was deposited to form a thin film semiconductor junction.

10% is contained in a-Si or a-SiGe by glow discharge decomposition method such as SiH ₄ or GeHe _4.
Since a certain amount of hydrogen (H) is contained, a-Si:
It should be written as H or a-SiGe: H,
In this specification, it is simplified and simply referred to as a-Si or a-SiGe.
Shall be written. Above the thin film semiconductor junction,
650 an ITO film as a transparent electrode by resistance heating vapor deposition
Deposited with a thickness of Å. Furthermore, it is a silver paste on the width of 3
A collecting electrode of 00 μm was formed. The solar cell samples thus obtained were classified as solar cell 1, solar cell 2, and solar cell 3, respectively.

Next, these solar cells were replaced with AM-1.5.
The current-voltage characteristics were evaluated by measuring under a (100 mW / cm ² ) solar simulator. Table 1 summarizes the above measurement results.

[0014]

[Table 1] The following can be said from the correlation between the characteristics of the substrates 1 to 3 and the characteristics of the solar cells 1 to 3. (1) The solar cell 2 has a small Jsc. It is considered that this is because the pitch of the irregularities of ZnO is small and light confinement is insufficient. (2) Further, the solar cell 1 and the solar cell 2 have a small FF.
This is probably because the series resistance is high and the voltage drop is large. (3) As described above, the characteristics of the back surface reflection layer and further the characteristics of the solar cell using the back surface reflection layer are affected by the difference after the deposition of the Al layer.

In order to clarify the cause of such a phenomenon, the Auger analysis of the substrates 1 to 3 was performed to measure the composition profile of the substrates.
It was found that an aluminum oxide layer of about 0 to 60Å was formed. It is considered that the increase in series resistance and the change in texture structure are due to the formation of this aluminum oxide layer.
Al is a metal having a high reflectance and a low price, and is suitable as a back surface reflection layer of a solar cell. However, since the surface characteristics are unstable as described above, the reproducibility is poor and the substrate temperature during the deposition of the semiconductor layer is limited, so that the application range is narrow.

The present invention has been made to solve the above-mentioned problems of the prior art, and by using the improved back reflection layer, incident sunlight can be effectively used, and the space between the substrate and the semiconductor layer can be effectively used. Since the series resistance is reduced, high conversion efficiency can be obtained, and moreover, the direct contact between the semiconductor layer and the metal layer and the leakage current at the defective part can be prevented, so that the reliability is high and the cost can be reduced. The purpose is to provide.

[0017]

In order to solve the above-mentioned problems of the prior art, the thin-film semiconductor solar cell according to claim 1 has a first portion, at least the surface of which is made of aluminum or an aluminum alloy, A thin film semiconductor junction is formed on a back reflective layer on which a transparent layer having a textured structure is formed on at least a surface of the substrate mixed with a second portion made of a metal different from the first portion. ,
Further, it is characterized in that a transparent electrode is formed thereon.

According to a second aspect of the present invention, in the first aspect of the present invention, the second portion occupies 30% or less of the total surface area of the substrate and is distributed in an island shape on the substrate. It is characterized by According to a third aspect of the present invention, in the back reflection layer, the metal layer forming the back reflection layer is at least Al.
_(100-x) Si x of the first layer on the substrate side is (where 2 ≦ x ≦ 0.5), Al (100-x) Si x ( where 2 ≦ x ≦ 0.
5) which is a transparent layer-side second layer.

[0019]

In FIG. 1, 101 is a metal substrate. A metal layer 102A having a high reflectance is formed on the surface thereof. Innumerable fine holes 102B are formed in the metal layer 102A, so that the metal substrate 101 is formed through the holes 102B.
The surface of is exposed. The transparent layer 103 is formed on it. The transparent layer is transparent to sunlight that has passed through the thin film semiconductor layer 104, has an appropriate electric resistance, and its surface has a texture structure. A thin film semiconductor junction 104 is formed on the transparent layer 103.

Here, p is used as the thin film semiconductor junction 104.
An example using an in-type a-Si solar cell is shown. Ie 10
5 is n-type a-Si, 106 is i-type a-Si, 107 is p
Type a-Si. When the thin film semiconductor junction 104 is thin, the entire thin film semiconductor junction often exhibits a texture structure similar to that of the transparent layer 103, as shown in FIG. 1
Reference numeral 08 is a transparent electrode on the surface. A comb-shaped collector electrode 109 is provided thereon.

The procedure for obtaining a thin film semiconductor solar cell having such a structure is as follows. 5 x 5 cm stainless steel plate (SU
S430) using a multi-target system device,
250 Å of Al was deposited by the C magnetron sputtering method. The substrate temperature at this time was 250 degrees. In the same apparatus, 4000 Å of ZnO was immediately deposited by the DC magnetron sputtering method without breaking the vacuum in the same apparatus.

According to SEM observation, the surface of ZnO was clouded because crater-shaped recesses having a diameter of 5000 to 6000 Å were densely gathered. This is substrate 4. Also,
High magnification (100,000 times) on the surface after Al deposition
When observed by SEM, the deposited Al layer has a diameter of 500
~ 1000 Å Unshaped hole is about 5000 ~ 600
It was open innumerably at a pitch of about 0.

Then, after depositing Al in the same apparatus, the substrate was once taken out from the apparatus, left for 1 day, and then set in the apparatus again to deposit ZnO. This is the substrate 5. When the surface of ZnO of the substrate 5 was observed, the crater-shaped recesses had a diameter of about 400 to 6000 Å and were clouded. Then, after the Al deposition, the substrate temperature was raised to 250 ° C., and ZnO was added.
Substrate 6 was formed by the same procedure as that for substrate 4, except that the substrate 6 was annealed for 1 hour until the start of deposition. When observing the surface of ZnO of the substrate 6, the crater-shaped recesses have a diameter of 5000 to 600.
It was about 0Å and was cloudy.

Further, Cr electrodes were formed on these substrates and the resistance between them was evaluated. 1c for board 4
0.2 Ω per m ² , substrate 5 0.5 Ω per cm ² ,
The substrate 6 had a resistance of 0.4 Ω / cm ² . Using the substrate having the back surface reflection layer thus formed, solar cells 4 to 6 were formed in the same procedure as the solar cells 1 to 3.

Next, these solar cells were replaced with AM-1.5.
The current-voltage characteristics were evaluated by measuring under a (100 mW / cm ² ) solar simulator. Table 2 summarizes the above measurement results.

[0026]

[Table 2] Further, when Auger analysis of the substrates 4, 5 and 6 was performed, an oxide layer of about 30 to 60 Å was observed on the surface of Al in the substrates 5 and 6. As described above, although the formation of an oxide layer on the surface of Al through the history similar to that of the substrates 1 to 3 was recognized, the characteristics of the substrate and the characteristics of the solar cell were hardly changed. The reason why such improvement was observed is speculated as follows. (1) Even if the surface of Al, which is the metal layer 102A, is oxidized, the stainless steel surface of the substrate 101 is exposed from the holes, so that the conduction is not impaired. Moreover, since the ratio of the area of the holes is small, the average reflectance is almost the same as in the case of the entire surface Al. (2) The ZnO texture structure is developed by Al pores 10.
Since it reflects the distribution of 2B, it is unlikely to be affected by changes in the state of the surface.

Next, A containing 5 wt% of Si instead of Al
The experiment was conducted using 1Si alloy as a metal layer. Since AlSi has excellent stability at high temperatures, it is a material that is often used in a structure in contact with a semiconductor layer. A instead of Al
A substrate 7 was obtained in the same manner as the substrate 1 except that 1Si was used. Substrate 2 except that AlSi was used instead of Al
Substrate 8 was obtained in the same manner as in. A substrate 9 was obtained in the same manner as the substrate 5 except that AlSi was used instead of Al. These substrates were evaluated in the same manner as the substrates 1 to 6. In addition, A on the substrate 9
SEM observation of the surface of the state where the deposition of 1 was completed at a high magnification (100,000 times) revealed that the deposited Al layer had a diameter of 500 to
An irregular hole of about 1000Å is almost 4000-500
It was open innumerably at a pitch of 0Å.

Using the back reflective layer thus formed, solar cells 7, 8 and 9 were formed in the same manner as solar cells 1, 2 and 5. These solar cells are then AM-1.5.
The current-voltage characteristics were evaluated by measuring under a (100 mW / cm ² ) solar simulator. Table 3 summarizes the above measurement results.

[0029]

[Table 3] When Auger analysis of the substrates 7, 8 and 9 is performed, the substrates 8 and 9 are
In Fig. 5, an oxide layer of about 50Å was observed on the surface of AlSi. Therefore, in the solar cell 8, deterioration of the solar cell characteristics is recognized, but in spite of the change in the surface property of AlSi, in the solar cell 9, no deterioration of the solar cell characteristics is recognized, and not only in the case of Al but also in the case of AlSi. It has been found that the above-mentioned invention also produces an effect when configured as in the present invention. That is, according to the structure of the present invention, the stability is good and the high reflectance of Al can be utilized.

Next, the back reflection layer used in the thin film semiconductor solar cell of the present invention will be described in detail. (Substrate and Metal Layer) Various metals are used as 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 before use, or may be used in the form of a long sheet depending on the plate thickness. In this case, since it can be wound in a coil shape, it is suitable for continuous production and can be easily stored and transported. A crystal substrate made of silicon or a plate made of glass or ceramics may be used depending on the application. Although the surface of the substrate may be polished, it may be used as it is if it has a good finish such as a bright annealed stainless steel plate.

For a substrate such as stainless steel or zinc steel plate which has a low light reflectance as it is, a metal layer having a high reflectance such as aluminum is deposited and used on the substrate. Further, even a material having a low conductivity as it is, such as glass or ceramics, can be used as a substrate by providing a metal layer having a high reflectance. As a metal with high reflectance, aluminum is easy to deposit and inexpensive, and is suitable for application to large area devices. From the standpoint of further improving the reflectance and improving the thermal stability, an alloy containing an appropriate amount of a metal such as Cu, Ag, Ni, Mo, Cr in addition to Si is preferably used in aluminum. it can.

For depositing the metal layer, a resistance heating or vacuum evaporation method using an electron beam, a sputtering method, an ion plating method, a CVD method, a plating method or the like is used. The case of the sputtering method will be described as an example of the film forming method. Figure 4
Shows an example of a sputtering apparatus. In the figure, 401 is a deposition chamber, which can be evacuated by an exhaust pump (not shown). A predetermined flow rate of an inert gas such as argon (Ar) is introduced into the inside of the deposition chamber 401 through a gas introduction pipe 402 connected to a gas cylinder (not shown) to adjust the opening of the exhaust valve 403 to a predetermined amount. It is regarded as pressure. Also,
The substrate 404 is fixed on the surface of an anode 406 having a heater 405 provided therein. A cathode electrode 408 is provided facing the anode 406 and having a target 407 fixed on the surface thereof. The target 407 is a block of metal such as Al to be deposited.

Usually, purity is 99.9% to 99.999%
Although it is a pure metal to some extent, a specific impurity may be introduced depending on the case. The cathode electrode is connected to the power supply 409. A radio frequency (RF) or direct current (DC) high voltage is applied by the power source 409 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 this plasma. Further, 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.

An example of deposition conditions will be given. An Al target having a diameter of 6 inches and a purity of 99.99% was used. Polished surface 5 cm x 5 cm 1 mm thick stainless steel plate (SUS
430) was used as the substrate. Distance between target substrates is 5c
m. Ar flow of 10 sccm, pressure 1.5
kept at mTorr. When a DC voltage of 500V is applied using an Al target having a diameter of 6 inches and a purity of 99.99%,
Plasma was generated and a current of 2 amps flowed. In this state, discharging was continued for 1 minute.

The substrate temperature is room temperature, 100 degrees, 200 degrees,
Samples 5a, 5b, 5c and 5d were used instead of 300 degrees. When the temperature was raised, the surface of Al changed from a smooth surface to a texture structure. In addition, deposition is performed at a substrate temperature of 300 degrees
SE with high magnification (100,000 times)
According to M observation, the deposited Al layer has a diameter of 500 to 1
An irregular shaped hole of about 000Å is approximately 5000-7000Å
It was opened innumerably at a certain pitch. Similar tendencies are observed with other metals and other film forming methods.

(Transparent Layer and Its Texture Structure) Examples of the transparent layer include ZnO, In ₂ O ₃ , SnO ₂ and C.
Many oxides such as dO, CdSnO ₄ , and TiO are used (however, the composition ratios of the compounds shown here do not always match the actual conditions). Generally, the higher the light transmittance of the transparent layer, the better, but it need not be transparent to the light in the wavelength range absorbed by the thin film semiconductor. Also,
The transparent layer preferably has an electric resistance in order to suppress a current due to a pinhole or the like. However, this resistance needs to be in a range in which the effect of the series resistance loss on the conversion efficiency of the solar cell can be ignored.

From this viewpoint, the range of resistance per unit area (1 cm ² ) is preferably 10 ^{−6 to} 10 Ω, more preferably 10 ^{−5 to 3} Ω, and most preferably 10 ^{−4 to 1} Ω. Further, the film thickness of the transparent layer is preferably as thin as possible from the viewpoint of transparency, but an average film thickness of 1000 Å or more is required to obtain the texture structure of the surface. Further, from the viewpoint of reliability, a film thickness larger than this may be required. The texture structure will be described in detail later.

For depositing the transparent layer, a vacuum evaporation 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 forming method.
Also in this case, the sputtering apparatus as shown in FIG. 4 can be used. However, for oxides, there are cases where the oxide itself is used as a target and cases where a metal (Zn, Sn, etc.) target is used. In the latter case, it is necessary to flow oxygen into the deposition chamber at the same time as Ar (this is called a reactive sputtering method).

An example of deposition conditions will be given. A stainless steel plate (SUS430) having a size of 5 cm × 5 cm and a thickness of 1 mm whose surface was polished was used as a substrate. Diameter 6 inches Purity 9
Using a 9.9% ZnO target with a distance between target substrates of 5 cm and Ar flow of 10 sccm,
Keeping the pressure at 1.5mTorr and applying DC voltage,
Plasma was generated and a 1 amp current flowed. In this state, discharge was continued for 5 minutes. Substrate temperature is room temperature, 100
ZnO was deposited by changing the temperature to 200 degrees or 300 degrees. When the temperature was raised, the surface of ZnO became cloudy. As shown in FIG. 5, a crater-like concave portion was observed on the surface of the sample in which the white turbidity occurred, which is considered to be the cause of the white turbidity.

The reason for the light confinement is considered to be light scattering in the metal layer when the metal layer itself has a texture structure, but when the metal layer is smooth and the transparent layer has a texture structure. Is considered to be scattered at the interface of at least one of the surface of the thin film semiconductor and the transparent layer due to the phase shift of the incident light between the concave portion and the convex portion. The pitch is preferably about 3000 to 20000Å, more preferably 4000 to 15000Å, and the height difference is preferably 500 to 20000Å, more preferably 700 to 10000Å. Further, if the surface of the thin film semiconductor has a texture structure similar to that of the transparent layer, light scattering is likely to occur due to the phase difference of light, and the effect of optical trapping is high.

In order to control the specific resistance of the transparent layer, it is advisable to add appropriate impurities. As the transparent layer of the present invention, the specific resistance of the above-mentioned conductive oxide tends to be too low. Therefore, it is preferable that impurities are added to appropriately increase the resistance. For example, an acceptor-type impurity (for example, ZnO) is added to a transparent layer that is an n-type semiconductor.
In addition, Cu, SnO ₂ and Al, etc., can be added in appropriate amounts to make the material intrinsic and increase the resistance. Also, adding impurities often enhances chemical resistance.

In order to add impurities to the transparent film, desired impurities may be added to the evaporation source or the target as described in the above experimental example. Particularly, in the sputtering method, a material containing impurities on the target. You can put a small piece of.
In FIG. 9, the back reflection layer has a texture structure, and is composed of a metal layer 902 and a transparent layer 905 formed on the metal layer 902 having a specific resistance in the range of 10 ⁻² to 10 ⁵ Ωcm. Is formed, and a transparent electrode 9 is formed on the
1 shows a thin film semiconductor solar cell in which 10 is formed. In the thin-film semiconductor solar cell, the metal layer 902 of the back reflection layer is at least Al _(100-X) Si _X (however,
0 ≦ x ≦ 0.5), the first layer 903 on the substrate side, and A
1 _(100-X) Si _X (where 2 ≦ x ≦ 6) and the second layer 904 on the transparent layer side. If the other manufacturing conditions are made in the same manner, the conversion efficiency becomes 7.5% and the conversion efficiency becomes Al.
This is an improvement over the case where only Si is used.

Although the reason for producing such an effect is not clear, it is presumed that the light can be more effectively scattered to the semiconductor layer by using two layers of materials having slightly different texture shapes. Next, each constituent element of the thin-film solar cell configured as shown in FIG. 9 will be described in detail.

(Substrate) As the substrate, various metals, organic films, glass, semix, etc. are used. 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 before use, or may be used in the form of a long sheet depending on the plate thickness. In this case, since it can be mounted in a coil shape, it is suitable for continuous production and can be easily stored and transported.

The surface of the substrate may be polished, but may be used as it is if it has a good finish such as a bright annealed stainless steel plate. (Metal Layer) A vacuum deposition method, a sputtering method, a CVD method, or the like can be used to deposit the metal layer. FIG. 10 shows an example of the sputtering apparatus. As shown in the figure, in this case, two deposition chambers 1001 and 1002 are provided so that two kinds of materials can be continuously produced. One target 1010 is Al and the other target 1011 is Al ₉₅ Si ₅ .

(Transparent Layer) Generally, the higher the light transmittance of the transparent layer, the better. However, this condition does not have to hold for light having a wavelength that is sufficiently absorbed by the thin film semiconductor, and the thin film semiconductor Does not need to hold for light of a wavelength that is not absorbed at all. That is, in the case of an a-SiGe semiconductor layer, it suffices to satisfy at least light having a wavelength in the range of 6500 to 10000Å.

Therefore, ZnO, SnO ₂ or the like can be preferably used for the transparent layer. Further, the transparent layer preferably has a certain amount of resistance in order to suppress a short circuit current due to a pinhole or the like in the semiconductor layer. On the other hand, the series resistance loss due to this resistance must be a thin enclosure that can be ignored by the shadow guard on the conversion efficiency of the solar cell. From this viewpoint, the range of resistance of the transparent layer is preferably 10 ^-2 to 10 ⁵ Ωcm. As a method of depositing the transparent layer, a resistance heating or vacuum vapor deposition method using an electron beam, a sputtering method as shown in FIG. 11, an ion plating method, a CVD method, a spray coating method and the like are used.

(Thin-Film Semiconductor Layer) The thin-film semiconductor layer having the structure shown in FIG. 9 can be manufactured by a microwave CVD apparatus or a capacitive coupling type high frequency CVD apparatus. When the gas has been sufficiently evacuated, SiH ₄ , SiF ₄ , PH ₃
/ H ₂ (1% H ₂ dilution), H ₂ 40 sccm were introduced,
The opening of the throttle valve is adjusted to maintain the internal pressure of the reaction container at an appropriate pressure, and when the pressure becomes stable, energy is immediately input from the microwave power source or the high frequency power source.

When plasma is generated by this, an n-type a-Si layer 207 is formed on the transparent layer 205. After evacuating again, this time from the gas inlet pipe SiH ₄ , GeH
Introduce ₄ , SiF ₄ , and H ₂ and adjust the opening of the throttle valve to keep the internal pressure of the reaction vessel at an appropriate pressure, and when the pressure becomes stable, immediately apply energy to sustain the plasma. .

As a result, the i-type a-SiGe layer 208 is formed on the n-type a-Si layer 207. At this time, if necessary, the flow rate ratio of SiH ₄ and GeH ₄ may be changed to form a film having an appropriate composition. After exhausting again, this time introduce SiH ₄ , BF ₃ H ₂ (1% H ₂ diluted) and H ₂ from the gas introduction pipe, adjust the opening of the throttle valve, and adjust the internal pressure of the reaction vessel to an appropriate value. The pressure was maintained, and when the pressure became stable, energy was immediately applied to continue the plasma. In this way, the p-type a-Si layer 209 is formed on the i-type a.SiGe layer 208.

The order of p-type and n-type layers may be reversed. In this description, a batch-type CVD apparatus is used, but a roll-to-roller having separate deposition layers for forming each layer using a belt-shaped substrate is used.
It may be continuously produced by a roll CVD apparatus. (Transparent electrode and collector electrode) Next, the sample is taken out from the high frequency CVD device, ITO is deposited by the resistance heating vacuum vapor deposition device, and then a paste containing an aqueous solution of iron chloride is printed to obtain the pattern of the desired transparent electrode. To form. Further, Ag paste is screen-printed to form a collecting electrode to complete a thin film semiconductor solar cell.

[0052]

Example 1 In this example, a pin-type a-Si photovoltaic element having the structure shown in the schematic sectional view of FIG. 2 was produced. Surface polished 5 x 5 cm, 1 mm thick Al
With the sputtering apparatus shown in FIG. 4, Cr was deposited on the plate 201 for a short time by the EB vapor deposition apparatus at a substrate temperature of 300 ° C. SEM of the surface in this state at high magnification (100,000 times)
Upon observation, the Cr layer 202B as a metal layer was deposited in the form of minute islands or spots depending on the deposition time. After being left in the air for 1 week, a ZnO target was used for a sputtering apparatus at a substrate temperature of 250 ° C. and an average thickness of 4
A 000 Å ZnO layer 203 was deposited to form substrates 11-14. The surface of ZnO has a texture structure.

As a comparative example, the substrate 10 was prepared in the same procedure as in Example 1 except that the metal layer Cr was not deposited.
Was produced. Further, the substrates 10 to 14 were replaced with commercially available capacitive coupling type high frequency CVD equipment (CHJ-303 manufactured by ULVAC, Inc.).
0). Rough evacuation and high vacuum evacuation were performed through the exhaust pipe of the reaction vessel using an exhaust pump. At this time, the surface temperature of the substrate was controlled by the temperature control mechanism so as to be 250 ° C. When the gas has been sufficiently exhausted, the gas introduction pipe is used to feed SiH ₄ 300 sccm and SiF _{4 4} sc
cm, PH ₃ / H ₂ (diluted 1% H ₂ ) 55 sccm, H
The ₂ 40 sccm was introduced, by adjusting the opening degree of the throttle valve, the internal pressure of the reaction vessel was maintained at 1 Torr, when the pressure is stable, and immediately put power of 200W from the high frequency power source. The plasma lasted for 5 minutes.

As a result, the n-type a-Si layer 205 was formed on the transparent layer 203. After exhausting again, this time, SiH ₄ 300sccm, SiF ₄ 4s
ccm, introducing H ₂ 40 sccm, by adjusting the opening degree of the throttle valve, the internal pressure of the reaction vessel was maintained at 1 Torr, when the pressure is stable, immediately from the high frequency power source 15
A power of 0 W was applied and the plasma was maintained for 40 minutes.

As a result, the i-type a-Si layer 206 becomes the n-type a
-Si layer 205 was formed. After exhausting again,
This time, SiH ₄ 50sccm, BF ³ /
H ² (1% H ² diluted) 50 sccm, H ₂ 500 sccc
m 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 became stable, 300 W of electric power was immediately supplied from the high frequency power source.
The plasma lasted for 2 minutes.

As a result, the p-type μc-Si layer 207 was formed on the i-type a-Si layer 106. Next, the sample was taken out from the high-frequency CVD apparatus, ITO was deposited by a resistance heating vacuum vapor deposition apparatus, and then a paste containing an aqueous solution of iron chloride was printed to form a desired transparent electrode 208 pattern. Further, Ag paste is screen-printed to collect the collector electrode 2
09 to form thin film semiconductor solar cells 10 to 14 (substrate 10
(Corresponding to ~ 14) was completed. AM these solar cells
The characteristics were evaluated under irradiation with light of 1.5 (100 mW / cm ² ). Table 4 summarizes the characteristics of these substrates and solar cells.

[0057]

[Table 4] Compared to the solar cell 10 in which no Zn layer is formed, Cr
In the solar cells 11 and 12 formed with, FF is remarkably large, while Jsc is hardly reduced. Thus, the effect of the present invention was confirmed. The Jsc of the solar cell 14 is remarkably lowered, which is considered to be caused not only by the high area ratio of Cr having a low reflectance but also by the poor development of the texture structure of ZnO. Therefore, it is preferable that the different metals are deposited in an island shape and the area ratio is 30% or less.

(Example 2) In this example, a pin type a-SiGe photovoltaic element having the structure shown in FIG. 3 was produced. A Ni layer 302B having a textured surface having a thickness of 1 μm was formed by plating on a stainless steel plate 301 having a surface of 5 × 5 cm and a thickness of 1 mm. An Al layer 302A having a thickness of 1000 Å was deposited thereon by a resistance heating vapor deposition method.

Further, this was immersed in an aqueous solution of aluminum hydroxide, a substrate was used as a positive electrode, a carbon rod was used as a negative electrode, and a DC voltage was applied to form a substrate 15. When the substrate 15 was analyzed by the micro Auger method, Al was preferentially dissolved and Ni was exposed only near the top of the convex portion of the texture. On the other hand, the substrate not immersed in the aluminum hydroxide aqueous solution was used as the substrate 1.
It was set to 6.

Next, Zn containing 1.0% Cu in the oxygen atmosphere was blown to the substrates 15 and 16 by an ion plating method at a substrate temperature of 300 ° C. to obtain an average thickness of 1
At μm, a ZnO layer with a textured surface was deposited. Continuing, 50 scc of Si ₂ H ₅ was used as the i layer.
m, GeH ₄ at 10 sccm and H ₂ at 300 sccm were introduced, the internal pressure of the reaction vessel was maintained at 1 Torr, and 100 W
Solar cells 15 and 16 were produced in the same manner as in Example 1 except that the a-SiGe deposited by applying the electric power of 1. and continuing the plasma for 10 minutes was used.

AM1.5 (100 mW /
cm ² ) The characteristics of the solar cell 1
In Example 5, the FF was as good as 62%, but in the solar cell 16, the FF was extremely low at 34%. In this case Zn
Since O is deposited by the reactive sputtering method using O ₂ , A
It is considered that the surface of 1 was oxidized. However, the solar cell 15 having the configuration of the present invention is not affected by the influence.

Example 3 In this example, the back surface reflection layer was continuously formed by using the apparatus shown in FIG. A substrate roll 601 having a width of 350 mm, a thickness of 0.2 mm, and a length of 500 m and made of an aluminum alloy containing 10% Cu is set in the substrate delivery chamber 603. By containing Cu, the mechanical strength of the sheet at high temperature is significantly increased. From here, the aluminum sheet 602 includes a metal layer deposition chamber 604 and a transparent layer deposition chamber 605.
After that, it 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. The target 609 of the deposition chamber 604 has a purity of 9
Sn is deposited on the sheet 602 by DC magnetron sputtering at 9.99% Sn. Deposition chamber 605
Target 610 is ZnO of 99.9% purity, DC
The ZnO layer is subsequently deposited by magnetron sputtering. Target 6 depending on the deposition rate and the desired film thickness
10 consists of 4 sheets.

A back reflection layer was formed using this apparatus. The sheet feeding speed was 20 cm / min, and the substrate temperature of Sn was 200 ° C. using only the substrate heater 608.
The substrate temperature of was adjusted to 250 degrees. Ar is flowed to adjust the pressure to 1.5 mTorr, and 50 is applied to each cathode.
A DC voltage of 0V was applied. A current of 2 amps flowed to the target 609 and a current of each ampere flowed to the target 610. When the wound sheet was examined, Sn was distributed in an island shape and the area ratio was 20%. The ZnO layer has an average thickness of 38
It was 00Å and the surface of the ZnO layer was cloudy.

On top of this, a-Si / a- of the structure shown in FIG.
A SiGe tandem solar cell was formed. Here, 701 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 705, 7
09 is an n-type a-Si layer, and 707 and 711 are p-type μc-S.
i and 706 are i-type a-SiGe layers, and 710 is i-type a-S.
It is the i layer. The film formations 705 and 706 were performed at 400 degrees. These thin film semiconductor layers are described in US Pat.
It was continuously manufactured using a roll-to-roll type film forming apparatus as described in No. 2,181.

On the other hand, 712 in FIG. 7 is a transparent electrode, and this transparent electrode was deposited by a sputtering apparatus similar to the apparatus shown in FIG. Reference numeral 713 is a collecting electrode. After patterning the transparent electrode and forming the collecting electrode, the sheet 602
Cut off. In this way, all the processes were processed continuously, and the mass production effect could be improved. When 100 samples were prepared by this method and the characteristics were evaluated under AM1.5 (100 mW / cm ² ) light irradiation, the photoelectric conversion efficiency was 11.4 ± 0.
Excellent conversion efficiency of 2% was obtained with good reproducibility. In addition, these solar cells can be used in an environment with a temperature of 50 degrees and a humidity of 90%.
After being left for 00 hours, the conversion efficiency was 11.5 ± 0.5% and no deterioration was observed. In addition, another 100 sheets created by this method are exposed to light equivalent to AM1.5 in the open state.
When irradiated for 00 hours, the deterioration due to light was as small as 10.7 ± 0.3%.

This is because light having a longer wavelength is effectively absorbed by adopting the tandem structure. Also a-S
This is because the deposition temperature of the iGe layer was set high, so that deterioration under light irradiation was suppressed. Thus, a thin film solar cell having high conversion efficiency and high reliability in combination with the effect of the back surface reflecting layer of the present invention was obtained. On the other hand, a solar cell was manufactured by the same steps as above except that Sn was not deposited. The photoelectric conversion efficiency was 4.7% ± 2.3%, which was extremely low and there was no reproducibility. It is considered that this is because the resistance of the back surface reflection layer after the substrate was annealed at 400 ° C. was high, and thus the surface of AlCu and ZnO reacted with each other. It has been found that even in such a case, the solar cell having the constitution of the present invention is not affected by the characteristics.

Example 4 A back reflective layer was formed in the same manner as in Example 1. Cu and 0.2 μm of Cu and 0.4 μm, respectively, were deposited on this substrate and the substrate on which Cr was not deposited by a sputtering method. Next, this sample was transferred to a quartz glass bell jar, and while being heated to 400 ° C., hydrogen selenide (H ₂ Se) diluted to 10% with hydrogen was caused to flow into the bell jar to obtain CuInSe ₂ (CIS).
Thin film was formed. A CdS layer was again deposited thereon to a thickness of 0.1 μm by sputtering and then annealed at 250 ° C. to form a p / n junction. Example 1 on this semiconductor layer
A transparent electrode and a collector electrode were formed in the same manner as in.

This solar cell is AM1.5 (100 mW /
cm ²⁾ when performing characterization under light irradiation, while the conversion efficiency in a solar cell with a Cr layer was obtained an excellent conversion efficiency of 11.8% 9.5 with no solar cell ZnO
%, The characteristics were inferior, and it was found that the present invention is effective for thin film semiconductors other than a-Si. (Embodiment 5) In this embodiment, stainless steel having a width of 100 mm and a length of 10 m (SUS 4
The strip of 30) was rolled into a substrate. The sputtering apparatus shown in FIG. 10 was used to deposit the metal layer. Also,
Two deposition chambers 1001 and 1002 are provided so that two kinds of materials can be continuously produced, and the exhaust pump 1003 can evacuate.

Argon (A) was introduced into the inside from gas introduction pipes 1004 and 1005 connected to a gas cylinder (not shown).
r) is introduced at a predetermined flow rate, the opening degree of the exhaust valve 1006 is adjusted, and the inside of the deposition chambers 1001 and 1002 is set to a predetermined pressure. Further, infrared heaters 1008 and 1009 are provided on the back surface of the belt-shaped substrate 1007. A cathode electrode, on which the targets 1010 and 1011 are fixed, is provided so as to face the substrate. Targets 1010, 1
011 is a block of material to be deposited.

The target 1010 is Al having a purity of about 99.99%, and the target 1011 has a purity of 99.99.
% Al ₉₅ Si ₅ . The cathode electrode is 101
2, 1013 connected to the power supply. A high DC voltage is applied by this power source to generate plasma (not shown) between the cathode and the substrate, and the material atoms of the targets 1010 and 1011 are deposited on the substrate 1007 by the action of this plasma. A magnet is provided inside the cathode to which the targets 1010 and 1011 are attached to concentrate the plasma on the target to increase the deposition rate.

An example of deposition conditions will be given. A stainless steel (SUS430) strip having a width of 100 mm and a ridge of 10 m whose surface is bright annealed is used as a substrate, and tension is applied between the substrate feeding part 1014 and the substrate winding part 1015 at a conveying speed of 200 mm / min. sent. The distance between the target substrates was 5 cm. Deposition chambers 1001, 10
While flowing Ar at 100 sccm for each 02,
The pressure was kept at 2.0 mTOrr. Target 101
0 and 1011 are 10 inch x 10 inch square,
Al having a purity of 99.99% and --Al ₉₅ Si ₅ were used. When a DC voltage of 350 V was applied to each target, plasma was generated and a current of 1.7 amps flowed.

In this state, the discharge was continued for 1 hour. The substrate temperature was monitored by bringing a thermocouple (not shown) into contact with the back surface of the substrate and controlling the infrared heater to 300 degrees. A portion of this substrate was cut out and the composition of the metal film was analyzed by Auger electron spectroscopy (AES). In the first layer, although a pure Al was used as the target, about 0.3 atomic% of Si was slightly measured, and a slight distribution in the thickness direction was recognized in the composition. This is probably due to the mixing of Si from the adjacent AlSi deposition chamber.

Although the boundary between the first layer and the second layer was not clear, it is considered that the region in which at least about 5 atom% of Si, which is almost the same as the target, was measured is the second layer. For the transparent layer, the sputtering apparatus shown in FIG. 11 was used, and the deposition conditions were as follows. A roll-shaped substrate on which Al and Al ₉₅ Si ₅ were deposited was tensioned between the substrate feeding part 1101 and the substrate winding part 1102 and fed at a conveying speed of 50 mm per minute.

The deposition chamber 1103 is evacuated by the exhaust pump 1104. Ar gas is introduced here from the gas introduction pipe 1105.
The flow rate was 0 sccm, the opening of the exhaust valve 1106 was adjusted, and the pressure in the deposition chamber was set to 2 mtorr. As the target 1107, a ZnO target having a size of 10 inches × 10 inches and a purity of 99.99% was used, and the distance from the substrate 1108 was 5 cm. The target is fixed to a cathode electrode having a magnet installed inside, and this cathode electrode is connected to a power supply 1109.

When a DC voltage of 360 V was applied to this cathode, a current of 0.8 amps flowed and plasma was generated. In this state, the discharge was continued for 2.5 hours. The substrate temperature was controlled to 200 degrees by the infrared heater 1110 on the back surface of the substrate. A part of this substrate was cut and Cr was vapor-deposited on the surface for resistance measurement by a vacuum vapor deposition machine. Thus, the resistance value was measured, and the resistance value was calculated from the film thickness by the stylus type film thickness measuring device, and was 10 ² Ωcm. As the thin film semiconductor layer, a thin film semiconductor layer of pin type a.SiGe having the structure shown in FIG. 9 was prepared as follows.

The substrate on which the back reflection layer is formed is 5 cm × 5
Commercially available capacitive coupling type high frequency CVD
It was set in a device (CHJ-3030 manufactured by ULVAC, Inc.). Rough evacuation and high vacuum evacuation were performed with an exhaust pump through the exhaust pipe of the reaction vessel. At this time, the surface temperature of the substrate was controlled by the temperature control mechanism so as to be 250 ° C.
When the gas is sufficiently exhausted, the SiH
₄ 300sccm, SiF ₄ 4sccm, PH ₃ / H ₂
(1% H ₂ dilution) 55 sccm, H ₂ 40 sccm were 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 became stable, the power of 200 W was immediately supplied from the high frequency power source. Was thrown in.

The plasma was maintained for 5 minutes. Thereby, the n-type a-Si layer 907 was formed on the transparent layer 905. After exhausting again, this time from the gas inlet pipe SiH
_{4 900sccm, GeH 4 200sccm, SiF} 4
4 sccm, 40 sccm of H ₂ were 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 became stable, the power of 150 W was immediately supplied from the high frequency power source, and it was generated. The plasma was maintained for 40 minutes. Thereby, the i-type a-SiGe layer 9
08 was formed on the n-type a-Si layer 907.

After evacuation again, this time, SiH ₄ 50 sccm, BF ₃ H ₂ (diluted with 1% H ₂ ) was introduced from the gas inlet pipe.
Introduce 50 sccm and H ₂ 500 sccm, adjust the opening of the throttle valve, and set the internal pressure of the reaction vessel to 1 Torr.
When the pressure was maintained at r and the pressure became stable, 300 W of power was immediately applied from the high frequency power supply. The plasma lasted for 2 minutes.

In this way, the p-type a-Si layer 909 becomes i
Formed on the type a-SiGe layer 908. After that, ITO was deposited as a transparent electrode by a resistance heating vacuum vapor deposition device, and a paste containing an aqueous solution of iron chloride was printed to form a desired transparent electrode pattern. Further, Ag paste was screen-printed to form a collector electrode, and a thin film semiconductor solar cell was completed. Ten samples were prepared by this method, and the AMl. 5 (1
00 mW / cm ² ) When the characteristics are evaluated under light irradiation,
The photoelectric conversion efficiency was 7.5 ± 0.3%, which was excellent in reproducibility.

Example 6 In this example, Example 5 is used.
Same material and same equipment were used. However, the metal layer is not deposited by continuous sputtering of Al and AlSi, but only Al is deposited once, and then the roll-shaped substrate is taken out again.
It was attached to the apparatus shown in FIG. 1 to deposit AlSi. When a part of this substrate was cut out and the composition was analyzed by AES as in Example 1, the amount of Si in the first layer was below the measurement limit.

The second layer is made of AlS containing about 5 atomic% of Si.
It was i. The other conditions were the same as in Example 1 to complete the solar cell. When the characteristics were evaluated by irradiation with light, a photoelectric conversion efficiency of 7.5 ± 0.3% was obtained. (Comparative Example 1) In this comparative example, the pin type a-S in which the back surface reflection layer of the structure shown in FIG. 8 is made of Al / Ti / ZnO.
An iGe solar cell was produced. Specifically, instead of the target of Al ₉₅ Si ₅ in Example 1, the purity is 99.99.
% Ti was used. The thickness of Al is the same as that of Example 1
_The substrate transfer speed was set to 100 mm / min in order to obtain a total thickness of ₉₅ Si ₅ .

Further, in order to make the thickness of Ti about 50 Å, the DC voltage applied to the target of Ti is 100V,
Furthermore, the thickness between the substrate and the target was shielded to control the deposited thickness. Other conditions were exactly the same as in Example 5, and a solar cell was prepared, and the characteristics were evaluated under light irradiation. The photoelectric conversion efficiency was 7.4 ± O. It was 2%. (Comparative Example 2) In this comparative example, the back surface reflection layer shown in FIG. 8 is a pin type a-SiG made of Al ₉₅ Si ₅ / ZnO.
e A solar cell was produced. Specifically, A in Example 1
the only target of l ₉₅ Si ₅ was used for the sputtering. Al ₉₅ Si of a thickness of ₅ Example 1 Al and Al ₉₅ Si
_The substrate transfer speed is 100 per minute to make the total thickness of ₅
mm. When other conditions were exactly the same as in Example 5 and a solar cell was prepared and characteristics were evaluated under light irradiation, a conversion efficiency of 7.0 ± 0.3% was obtained in photoelectric conversion efficiency.

[0084]

As described above, according to the first and second aspects of the present invention, by using the back surface reflection layer according to the present invention, particularly, aluminum or its alloy whose surface state is unstable is used. However, a solar cell with high reproducibility, large current, low series resistance loss, and high conversion efficiency can be obtained. Further, even if the substrate temperature during film formation of the thin film semiconductor is raised, the change in the characteristics is small, so that a thin film semiconductor junction with excellent characteristics can be obtained, and a solar cell with even higher conversion efficiency can be obtained. Moreover, since the solar cell according to the present invention can be manufactured by a method having high mass productivity such as a roll-to-roll method, it greatly contributes to the spread of solar power generation.

According to the third aspect of the present invention, since the light is effectively confined in the thin film semiconductor by using the back surface reflection layer according to the present invention, the absorption of the light into the thin film semiconductor is increased and the conversion is performed. A highly efficient solar cell can be obtained. Further, metal atoms are less likely to diffuse into the semiconductor film, and even if there is a partial short circuit in the thin film semiconductor, the leak current is suppressed by an appropriate electric resistance, and a highly reliable solar cell can be obtained.

Furthermore, the back surface reflection layer of the invention according to the third aspect can exert a sufficient effect even if the transparent layer constituting the back surface reflection layer is thin.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a thin film semiconductor solar cell according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a thin film semiconductor solar cell according to Example 1.

FIG. 3 is a cross-sectional view showing a configuration of a thin film semiconductor solar cell according to Example 2.

FIG. 4 is a schematic side sectional view showing a configuration of a sputtering apparatus suitable for manufacturing the back surface reflection layer according to the present invention.

FIG. 5 is an SEM photograph of a transparent layer having a texture structure.

FIG. 6 is a schematic cross-sectional view showing the configuration of another sputtering apparatus suitable for manufacturing the back surface reflection layer according to the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a thin film semiconductor solar cell according to Example 3.

FIG. 8 is a cross-sectional view showing a configuration of a conventional thin film semiconductor solar cell.

FIG. 9 is a cross-sectional view showing the configuration of a thin film semiconductor solar cell according to Example 5.

FIG. 10 is a schematic side sectional view of a sputtering apparatus for forming a metal layer.

FIG. 11 is a schematic side sectional view of a sputtering apparatus for forming a transparent layer.

[Explanation of symbols]

101, 701 substrate 102, 702 metal layer 102A first metal 102B second metal 103, 703 transparent layer 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 collector electrode 202A first metal 202B second metal 302A first metal 302B second metal 604 metal layer deposition chamber 605 transparent layer deposition chamber 404 , 602 Substrate 601 Substrate roll 407, 609, 610 Target 405, 607, 608 Substrate heating heater 409 Power supply 801, 901 Substrate 802, 803, 804, 902, 903, 904 Metal layer 805, 905 Transparent layer 806 Thin film semiconductor layer 907 , 907 n-type a-Si 808, 908 i a-Si or i-type a-SiGe 809, 909 p-type a-Si 81, 910 transparent electrode 811, 911 collector electrode 1001, 1002, 1103 deposition chamber 1007, 1108 substrate 1014, 1101 substrate delivery part 1015, 1102 substrate Winding part 1010, 1011, 1107 Target 1008, 1009, 1110 Infrared heater for substrate heating 1012, 1013, 1109 Power supply 1003, 1104 Exhaust pump 1006, 1106 Exhaust valve 1004, 1005, 1105 Gas introduction pipe

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Atsushi Shiozaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masahiro Kanai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Takahiro Fukuoka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Gojin Yoshino 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. A substrate, at least the surface of which is mixed with a first portion made of aluminum or an aluminum alloy and a second portion made of a metal different from the first portion, at least on the substrate. A thin film semiconductor solar cell, comprising a thin film semiconductor junction formed on a back reflective layer having a transparent layer having a textured surface, and a transparent electrode formed on the thin film semiconductor junction. 2. The thin film according to claim 1, wherein the second portion occupies 30% or less of the total surface area of the substrate, and is distributed in an island shape on the substrate. Semiconductor solar cells. 3. The back reflection layer, wherein the metal layer constituting the back reflection layer is at least Al _(100-x) Si _x (where 2 ≦ x ≦
0.5) the first layer on the substrate side and Al _(100-x) Si
The thin film semiconductor solar cell according to claim 1, wherein the thin film semiconductor solar cell comprises a second layer on the transparent layer side with _x (where 2 ≦ x ≦ 0.5).