JPH06204533A - Semiconductor solar cell - Google Patents

Abstract

PURPOSE:To provide a semiconductor solar cell which has a high conversion efficiency and in which a leakage current between a semiconductor layer and a metal layer can be prevented and its manufacturing cost is low. CONSTITUTION:A semiconductor solar cell comprises a rear surface reflecting layer 103, a semiconductor junction layer 104 and a transparent electrode layer 108 sequentially laminated on a base 101 in which its surface is made of a metal layer, wherein the reflecting layer is formed of a mixture layer of an insulator 102a and metal 102b.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a future energy source for humanity,
Carbon dioxide, which is generated as a result of its use, will cause global warming, oil and coal, or accidents, and even nuclear power where there is no danger of radiation even during normal operation. There are many problems to be dependent on. Since solar cells use the sun as an energy source and have very little effect on the global environment, further widespread use is expected.

However, under the present circumstances, there are the following problems that prevent full-scale spread. Conventionally,
Single crystal or polycrystalline silicon has been often used as a solar cell. However, in these solar cells, much energy and time are required for crystal growth, and complicated steps are required thereafter, so that the mass production effect is difficult to increase, and it is difficult to provide a solar cell at a low cost. .

On the other hand, amorphous silicon (hereinafter a-S)
(hereinafter referred to as i)), and so-called thin film semiconductor solar cells using compound semiconductors such as CdS and CuInSe ₂ have been actively researched and developed. In these solar cells, it is only necessary to form as many semiconductor layers as necessary on an inexpensive substrate such as glass or stainless steel, and the manufacturing process thereof is relatively simple, and there is a possibility of cost reduction. However, thin-film solar cells have not been used in earnest since their conversion efficiency is lower than that of crystalline silicon solar cells and there is concern about their reliability for long-term use.
Therefore, various measures have been taken in order to improve the performance of the thin film solar cell.

One of them is a back surface reflection layer for increasing the reflectance of light on the surface of the substrate to return the sunlight not absorbed by the thin film semiconductor layer to the thin film semiconductor layer again and effectively use the incident light. . Therefore, when sunlight is incident on the transparent substrate from the substrate side, the electrode formed on the surface of the thin film semiconductor is made of a metal having a high reflectance such as silver (Ag), aluminum (Al) or copper (Cu). Good to do. When sunlight is incident on the surface of the thin film semiconductor layer, the semiconductor layer may be formed after forming a similar metal layer on the substrate. If a transparent layer having appropriate optical properties is interposed between the metal layer and the thin film semiconductor layer, the reflectance can be further increased by the multiple interference effect. Figure 2
(A) and (B) are the results of simulation showing the improvement of reflectance when a layer made of zinc oxide (ZnO) is interposed as a transparent layer between silicon and various metals.

The use of such a transparent layer is effective in enhancing the conversion efficiency and the reliability of the thin film solar cell. Japanese Patent Publication No. 60-41878 describes that a semiconductor layer and a metal layer can be prevented from alloying by using a transparent layer. U.S. Patents 4,532,372 and 4,598,30
No. 6 states that by using a transparent layer with appropriate resistance, it is possible to prevent excess current from flowing between the electrodes even if a short circuit occurs in the semiconductor layer.

[0007]

However, according to the findings of the present inventors, depending on the deposition conditions of the thin film semiconductor, the high temperature and high humidity of the formed solar cell can be obtained even though the transparent layer is provided. In some cases, it was not possible to obtain sufficient reliability for use below. Therefore, the thin-film semiconductor solar cell may be produced at a low price, but it has not come into full-scale use for solar power generation.

The present inventors have for the first time found that the conventional backside reflecting layer has the following problems. (1) Since the thin film semiconductor layer has a defective portion such as a pinhole, the transparent electrode on the surface of the thin film semiconductor layer and the transparent layer which is a component of the back surface reflective layer can directly contact through such a defective portion. . If the transparent layer does not have an appropriate resistance, it is impossible to prevent an excessive current from flowing as a leak current in this portion. (2) When the metal layer is made thin, the metal layer has an island structure depending on the material of the metal layer and the deposition conditions of the transparent layer, and the base body as the base is exposed to significantly reduce the reflectance, resulting in a solar cell. Will reduce the characteristics of.

The present invention has been made in consideration of the above circumstances, and it is possible to obtain a high conversion efficiency by effectively utilizing the sunlight incident on the back surface reflection layer, and moreover, to directly obtain the semiconductor layer and the metal layer. It is an object of the present invention to provide a highly reliable thin-film semiconductor solar cell, which can prevent electrical contact and leakage current at a defective portion. A further object of the present invention is to contribute to full-scale spread of solar power generation by providing a semiconductor solar cell at low cost.

[0010]

As a result of examining the above problems, the present inventors have come to recall the basic concept of the present invention described below. The semiconductor solar cell of the present invention is a semiconductor solar cell in which at least the surface thereof is formed of a metal layer or an alloy layer on a substrate, and a back surface reflection layer, a semiconductor bonding layer, and a transparent electrode layer are sequentially laminated, wherein the back surface reflection layer is It is characterized by comprising a mixed film of an insulator and a metal or an alloy.

Further, the solar cell of the present invention is a semiconductor solar cell in which a back reflection layer, a semiconductor bonding layer, and a transparent electrode layer are sequentially laminated on a substrate having at least its surface made of a metal layer or an alloy layer, The back reflection layer is composed of a plurality of layers, the layer in contact with the metal layer of the plurality of layers is composed of a mixed film of an insulator and a metal or an alloy, and the plurality of layers other than the layer composed of the mixed film are transparent conductive. Characterized by consisting of the body.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the present invention,
The insulator is made of an oxide, a nitride, a fluoride, or a mixture thereof, and the metal is any one of a noble metal, a noble metal alloy, Al, an Al alloy, Cu, and a Cu alloy, or It consists of a mixture of these.

Further, in another preferred embodiment of the present invention, the mixing volume ratio of the insulator and the metal is 1: 2 to 2.
The range is 1: 200. An example of the structure of the semiconductor solar cell according to the present invention is shown in FIG. Reference numeral 101 in FIG. 1 denotes a conductive base (substrate). A back reflection layer 103 made of a mixed film of an insulator 102a and a metal or alloy 102b is formed thereon.
To form. The back surface reflection layer returns a large amount of sunlight that has passed through the semiconductor layer to the semiconductor bonding layer. Also, the back surface reflection layer has an appropriate electric resistance. There is a semiconductor junction bonding layer 104 on this. Here, an example using a pin-type a-Si solar cell as the semiconductor junction layer is shown. That is, 105 is n-type a-Si, 106 is i-type a-Si, 1
07 is p-type a-Si. Reference numeral 108 is a transparent electrode on the surface. A comb-shaped collector electrode 109 is provided thereon.

The semiconductor solar cell having such a structure has the following effects. (1) Since the back surface reflection layer 103 is composed of a mixed film of the insulator 102a and the metal or alloy 102b, it has an appropriate resistance, and therefore, even if a defect occurs in the semiconductor layer, an excessive current does not flow. (2) Since the metal 102b in the back surface reflection layer 103 provides a high reflectance, the characteristics of the solar cell do not deteriorate even if the reflectance of the surface of the base substrate 101 as a base is low.

Experiments for showing the effect of the present invention will be described below. (Experiment 1) 5 cm × 5 cm stainless steel plate (SUS30
4) On top of this, a mixed film of MgF ₂ and Au was deposited to 1000 Å by the high frequency sputtering method. As the target, a MgF ₂ target on which Au metal pieces were arranged was used. The substrate temperature at this time was 100 ° C. From the appearance, the surface of the back reflection layer was glossy.

On the back reflective layer thus formed, a glow discharge decomposition method was used to produce SiH ₄ and PH ₃ as source gases.
Type a-Si layer is 200 angstroms, SiH ₄ is a source gas, i-type a-Si layer is 4000 angstroms, p-type microcrystals are SiH ₄ , BF ₂ and H ₂ as source gases (hereinafter, microcrystals are referred to as “μc”). Representation)) A Si layer was deposited to 100 angstrom to form a semiconductor junction layer. In addition, S
In a-Si by glow discharge decomposition method such as iH ₄ ,
Since it contains about 10% hydrogen (H), it is generally aS.
Although expressed as i: H, it is simply a for simplicity in this description.
-Si shall be described.

On this semiconductor bonding layer, an ITO film was deposited as a transparent electrode in a thickness of 650 Å by a resistance heating evaporation method. Further, a collector electrode having a width of 300 μm was formed thereon with a silver paste to obtain a sample 1a. After the mixed film deposition,
Sample 1 except that ZnO was deposited as a transparent conductor at a thickness of 5000 angstrom by the DC magnetron sputtering method.
Sample 1b was obtained in the same manner as a. That is, in the sample 1b, the surface reflection layer is composed of a plurality of layers of the mixed film and the film made of the transparent conductor (claim 2).

A sample 1c was obtained in the same manner as the sample 1a except that neither the mixed film nor the transparent conductive film was deposited. The three kinds of samples thus obtained were measured under a solar simulator of AM-1.5 to evaluate the conversion efficiency as a solar cell. As a result, the conversion efficiencies of Samples 1a, 1b, and 1c were 8.0%, 8.4%, and 6.7%, respectively. From this result, the following can be understood. That is, (1) Sample 1 using a back reflective layer in which the layer in contact with the surface of the substrate is formed of a mixed film of an insulator and a metal or an alloy.
In the cases a and 1b, the conversion efficiency is improved as compared with the sample 1c in which the back reflection layer is not formed.

(2) The conversion efficiency of the sample 1b was slightly higher than that of the sample 1a, probably because the multiple interference effect of the transparent conductive film forming the back surface reflection layer appeared. (Experiment 2) In Experiment 1, except that a nickel-plated copper plate was used instead of the stainless steel substrate, Sample 2a was prepared in the same manner as Sample 1a, Sample 2b was prepared in the same manner as Sample 1b, and Sample 2c was prepared in the same manner as Sample 1c. Obtained.

The surface of the nickel-plated copper plate is SEM.
When observed with, the unevenness was conspicuous, and it was rough. The surface roughness was. AM of 3 types of samples
The measurement results of the conversion efficiency at 1.5 are Samples 2a, 2b, 2
The values of c were 8.2%, 8.5% and 1.2%, respectively.
The results show the following. That is, (1) The conversion efficiency of the sample 2c in which the back reflection layer was not formed was remarkably low. It is considered that this is because defects such as pinholes were generated in the semiconductor layer due to the unevenness of the substrate surface, and the substrate and the transparent electrode were short-circuited via the defects.

(2) In Samples 2a and 2b, good solar cells were obtained without the occurrence of short circuit. It is considered that this is because the back surface reflection layer including the mixed film of the insulator and the metal in contact with the surface of the substrate has an appropriate resistance. (Front Surface Reflecting Layer) Next, the back surface reflecting layer in the semiconductor solar cell according to the present invention will be described in detail.

The mixed film forming the back surface reflection layer is composed of an insulator and a metal or alloy, and examples of the insulator include oxides such as SiO ₂ , MgO, TiO ₂ and SnO ₂ , MgF ₂ , LiF and CeF. ₃ , such as fluoride, Ti
Either a nitride such as N or a mixture thereof is used. The film formed only of the insulator may be transparent, and for example, when deposited on a glass substrate with a thickness of 500 Å, the transmittance thereof is 60% or more, preferably 65% or more with respect to light having a wavelength of 800 nm. More preferably, it is 70% or more.

The metal plays a role of conducting electricity generated by the incidence of light on the semiconductor layer and a role of a reflection layer for returning the light transmitted through the semiconductor layer to the semiconductor layer again.
Therefore, the metal may be a noble metal such as Au, Ag, Pt, or Rh, any of these noble metal-based alloys, Al, Al-based alloys, Cu, Cu-based alloys, or their own reflectance such as a mixture thereof. Use a substance with a high

For depositing the mixed film, there are used a vacuum evaporation method using resistance heating or an electron beam, a sputtering method, an ion plating method, a CVD method, a plating method, or a combination thereof. The case of the sputtering method will be described as an example of the film forming method. FIG. 3 shows an example of the sputtering apparatus. A deposition chamber 401 can be evacuated by an exhaust pump (not shown). A gas inlet pipe 402 connected to a gas cylinder (not shown) was used to supply argon (A
Inert gas such as r) and reactive gas such as oxygen, fluorine, and nitrogen are introduced at a predetermined flow rate as necessary, and the exhaust valve 4
The opening degree of 03 is adjusted so that the inside of the deposition chamber 401 has a predetermined pressure. The substrate 404 is fixed on the surface of the anode 406 having the heater 405 provided therein. Anode 406
A cathode electrode 408 having a target 407 fixed thereto is provided on the surface of the cathode electrode 408. Target 407
Is a block of insulator in the mixed film to be deposited.
The metal piece 420 is the metal in the mixed film to be deposited,
It is preferable to use a material having a purity of about 99.9% to 9.999%. The cathode electrode is connected to the power supply 409. A high voltage of high frequency (RF) is applied by the power source 409 to generate plasma 410 between the cathode and the anode. By the action of this plasma, the target 407 and the metal piece 42
Zero atoms are deposited on the substrate 404 as a mixed film of insulator and metal. Further, in a magnetron sputtering apparatus in which a magnet is provided inside the cathode 408 to increase the intensity of plasma, the deposition rate can be increased.

An example of deposition conditions will be given. 6 inch diameter S
5 mm x 30 mm purity 99.99 on the iO ₂ target
% Au was used so as to vertically cross the erosion part. At this time, the area of Au in the entire erosion portion was set to about 80%. Polished surface 5 cm x 5 cm 1 mm thick stainless steel plate (sus43
0) was used as the substrate. The distance between the target substrates was 5 cm. Ar pressure of 1.5 mTo while flowing 10 sccm
kept at rr. When RF power of 4 kW was applied, plasma was generated, and discharge was continued for 1 minute in this state. The substrate temperature was 100 ° C. The electric resistance of the thus obtained mixed film in the direction perpendicular to the substrate is 10E-1 per cm ^2.
The reflectance for light having a wavelength of Ω and a wavelength of 800 nm was 65%. Similar results were obtained in other mixed films and other film forming methods depending on the film forming conditions.

The mixed volume of the insulator and metal of the mixed film is
1: 2 to 1: 200, preferably 1: 3 to 1: 200,
More preferably, it is 1: 4 to 1: 200. When the amount of the insulator is larger than this range, the electric resistance becomes large and the reflectance also decreases. Further, when the amount of the insulator is small, the electric resistance becomes too low, and a short circuit may occur between the mixed film and the transparent electrode via a pinhole or the like of the semiconductor layer after the solar cell is formed.

The thickness of the mixed film is preferably 250 Å or more so as to cover the base substrate. Further, when the surface of the mixed film has a texture structure in order to obtain a light trapping effect in the semiconductor layer described later, a thickness of 1000 angstroms or more is preferable. The reason why the light confinement occurs due to the texture structure is considered to be scattering due to the phase shift of the incident light between the concave portion and the convex portion at the surface of the semiconductor and / or the interface with the transparent layer.

As the transparent conductive film in the second aspect of the present invention, for example, ZnO, ITO, SnO ₂ or the like is used. An example of deposition conditions will be given. The aforementioned SiO ₂ / A
When a zinc oxide target was used on the u mixed film, the distance between the target substrates was 5 cm, and Ar was passed at 15 sccm, the pressure was kept at 2 mTorr and a direct current voltage was applied, a current of 1 ampere of plasma flowed. In this state, discharge was continued for 5 minutes. The substrate temperature was 150 ° C. When the smooth zinc oxide transparent conductive layer thus obtained is used, a multiple interference effect of light can be expected. Further, a texture structure may be provided on the surface of the transparent conductive layer in order to obtain a light trapping effect. To obtain the texture structure on the surface, an average film thickness of 1000 Å or more is required.

Mixed film only one layer, and mixed film / plurality
In any of the back reflective layers in the case of a transparent conductive film of
Also, the value of electric resistance is the series resistance loss and the conversion efficiency of the solar cell.
Must be within a negligible range
From such a viewpoint, the unit area (1 cm ²) Per resistance range
Is 10^-6-10Ω, preferably 10^-Five~ 3Ω, further
Preferably 10^-Four~ 1Ω. It also penetrates the semiconductor layer
From the perspective of returning the light that has been emitted to the semiconductor layer again
The reflectance for light with a wavelength of 800 nm is 50% or more,
55% or more, more preferably 60% or more
It

[0030]

Embodiments of the semiconductor solar cell according to the present invention will be described below with reference to the accompanying drawings. (Example 1) In this example, a pin type a-Si solar cell having the structure shown in the schematic cross-sectional view of FIG. 1 was produced.

On a stainless steel plate 101 having a thickness of 5 cm × 5 cm and a thickness of 1 mm, with the apparatus shown in FIG. 3, Au having a purity of 99.99% on the SiO ₂ target occupied about 80% of the total area of Au. Therefore, the substrate temperature is set to 10 by using one that is arranged so as to cross the erosion portion vertically.
SiO ₂ and A with a thickness of 500 Å at 0 ° C
A backside reflective layer 103 of a mixed film of u was deposited.

When measured by
SiO₂The volume ratio of Au to Au was: Continued
The substrate on which the lower electrode is formed by a commercially available capacitive coupling type
Frequency CVD equipment (CHJ-3030 manufactured by ULVAC, Inc.)
Set Exhaust pump, through the exhaust pipe of the reaction vessel
Then, roughing and high vacuuming operations were performed. At this time, the board
The surface temperature is controlled by a temperature control mechanism so that the surface temperature becomes 250 ° C.
I controlled. When the gas is exhausted sufficiently,
, SiH_Four: 300 sccm, SiF_Four: 4 sccm,
PH ₃/ H₂(1% H₂Dilution): 55 sccm, H₂: 40
Introduce sccm, adjust throttle valve opening
Keeps the internal pressure of the reaction vessel at 1 Torr and stabilizes the pressure.
Immediately, 200W of electric power from the high frequency power supply
I put it in. The plasma lasted for 5 minutes. This allows
The n-type a-Si layer 105 was formed on the transparent layer 103.
After exhausting again, this time from the gas inlet pipe SiH_Four:
300 sccm, H₂: Introduce 40 sccm and slot
The internal pressure of the reaction vessel to 1 Torr by adjusting the opening of the valve.
Hold at r and stabilize the pressure.
Power of 300 W was applied from the source. Hold plasma for 2 minutes
I continued. As a result, the p-type μc-Si layer 107 becomes the i-type a.
-Si layer 106 was formed. Next, the sample is subjected to high frequency CV
Take it out from the D device and use the resistance heating vacuum deposition device to make ITO.
After depositing, print a paste containing iron chloride aqueous solution,
A desired transparent electrode 108 pattern was formed. Furthermore A
The g paste is screen-printed to form the collector electrode 109.
A thin film semiconductor solar cell was completed. 10 pieces in this way
Make a sample, AM1.5 (100mW / cm ²) Illumination
When the characteristics were evaluated under irradiation, the photoelectric conversion efficiency was 8.
Excellent change efficiency of 1 ± 0.2% was obtained with good reproducibility.
In addition, these solar cells are used in an environment with a temperature of 80 degrees and a humidity of 70%.
It was left under 480 hours, but the change efficiency was 8.0 ± 0.6%.
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 produced. MgF was deposited on a nickel-plated copper plate 101 having a size of 5 cm × 5 cm and a thickness of 0.2 mm by an electron beam evaporation method.
₂ by resistance heating at the same time in the same vacuum furnace at room temperature, and at the same time at room temperature to deposit a back reflection layer of a mixed film of MgF ₂ and Ag having a thickness of 600 angstroms, and then Si ₂ as an i layer. H ₆ at 5 sccm, GeH ₄ at 10 sccc
m, H ₂ of 300 sccm was introduced, and the internal pressure of the reaction vessel was adjusted to 1
Ten samples were prepared in the same manner as in Example 1 except that a-SiGe was used, which was held at Torr, 100 W of electric power was applied and plasma was maintained for 10 minutes to deposit. When the characteristics of these were evaluated under irradiation with AM1.5 (100 mW / cm ² ) light, the photoelectric conversion efficiency was 7.9 ± 0.3.
%, And excellent conversion efficiency was obtained with good reproducibility.

Example 3 A back surface reflection layer was continuously formed using the apparatus shown in FIG. Here, the substrate delivery chamber 703 has a cleaned width of 350 mm and a thickness of 0.2 mm.
A stainless sheet roll 701 having a length of 500 m is set. From here, the stainless sheet roll 702 is sent to the substrate winding chamber 706 through the back surface reflection layer deposition chamber 704. The sheet 702 can be heated to a desired temperature by the substrate heater 707 in each deposition chamber. The target 709 in the deposition chamber 704 is SiO ₂ and A.
g is mixed at a ratio of 1:10, and the back surface reflection layer of the mixed film is deposited on the sheet 702 by the RF magnetron sputtering method.

A back reflection layer was formed using this apparatus. The sheet feeding speed was set at 10 cm / min, and the substrate temperature during deposition of the back reflective layer was adjusted to 100 degrees by using the substrate heater 707. Ar flow and pressure 1.5 mTo
RF power of 5 kW was applied to each cathode. When the wound sheet was examined, the thickness of the mixed film was 700 angstrom, and it was a glossy surface.

On top of this, a-Si / a of the structure shown in FIG.
-SiGe tandem solar cells were formed. Here 801
Is a substrate, 802 is a metal layer, 803 is a transparent layer, 804 is a bottom cell, and 808 is a top cell. 805,
809 is an n-type a-Si layer, and 807 and 811 are p-type μc-.
Si, 806 is i-type a-SiGe layer, 810 is i-type a-
It is a Si layer. These thin film semiconductor layers are described in US Pat.
Roll toe as described in 492,181
It was continuously manufactured using a roll type film forming apparatus. Again 81
Reference numeral 2 is a transparent electrode, which was deposited by a sputtering apparatus similar to the apparatus of FIG. Reference numeral 813 is a collector electrode. Sheet 7 after patterning transparent electrodes and forming collector electrodes
02 was cut. In this way, all the steps were processed continuously, and the mass production effect was able to be achieved.

100 samples were prepared by this method, and the AM
When the characteristics were evaluated under irradiation with light of 1.5 (100 mW / cm ² ), excellent conversion efficiency of 9.3 ± 0.3% in photoelectric conversion efficiency was obtained with good reproducibility. Further, these solar cells were left for 480 hours in an environment of a temperature of 85 degrees and a humidity of 70%, but the conversion efficiency was 9.1 ± 0.6%, and deterioration was hardly observed. In addition, another 100 sheets created by this method are lit to a light equivalent to AM1.5 in the released state.
When irradiated for 0 hours, the deterioration due to light was 8.9 ± 0.4%, which was small. This is because by adopting the tandem structure, light having a longer wavelength can be effectively absorbed and the output voltage can be made higher.

(Example 4) A back reflective layer was formed in the same manner as in Example 1 except that a ZnO transparent conductive film was deposited at 3000 angstrom after the mixed film was deposited. Cu was deposited by 0.2 μm and indium (In) was deposited by 0.4 μm on this by a sputtering method. Next, this sample was transferred to a bell jar made of quartz glass and hydrogen selenide (H ₂ Se) diluted to 10% with hydrogen was flown into the bell jar while heating at 400 ° C. to form a CuInSe ₂ (CIS) thin film. On top of this, again use CdS by sputtering.
Of 0.1 micron and then annealed at 250 degrees to form a p / n junction. A transparent electrode and a collector electrode were formed on this in the same manner as in Example 1.

This solar cell is AM1.5 (100 mW /
cm ₂ ) When the characteristics were evaluated under light irradiation, the conversion efficiency was 7.6%, which was excellent.
It was found that it is also effective for thin film semiconductors other than Si.

[0040]

As described above, according to the present invention, since the back reflection layer is made of a mixed film of an insulator and a metal or an alloy, the light transmitted through the semiconductor layer is reflected back to the semiconductor layer to absorb the light. Can be increased to provide a solar cell with high conversion efficiency. Further, the present invention can provide a highly reliable solar cell because the leak current can be suppressed by an appropriate electric resistance even if there is a partial short circuit portion in the semiconductor.

Further, the back reflection layer provided in the present invention can be manufactured as a part of a method having high mass productivity such as a roll-to-roll method. Therefore, the present invention greatly contributes to the spread of solar power generation.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram showing a cross-sectional structure of an embodiment of a semiconductor solar cell according to the present invention.

FIG. 2 Zn vs. reflectance at the interface between silicon and metal
It is a graph which shows the characteristic which shows the effect of O, (A) is Zn.
When there is no O (transparent conductor), (B) shows the case where ZnO is present.

FIG. 3 is a conceptual configuration diagram showing a structure of a sputtering apparatus suitable for manufacturing a back surface reflection layer provided in an example of a semiconductor solar cell according to the present invention.

FIG. 4 is a conceptual configuration diagram showing the structure of another sputtering apparatus suitable for manufacturing the back surface reflection layer provided in the example of the semiconductor solar cell according to the present invention.

FIG. 5 is a conceptual configuration diagram showing a cross-sectional structure of another embodiment of the semiconductor solar cell according to the present invention.

[Explanation of symbols]

 101,801 Substrate (base), 102a, 802a Insulator, 102b, 802b Metal, 103,803 Backside reflective layer, 104 Semiconductor bonding layer 105,805,809 n-type a-Si, 106,810 i-type a-Si, 806 i-type a-SiGe, 107,807,811 p-type μc-Si, 108,812 transparent electrode, 109,813 collector electrode, 703 substrate delivery chamber, 706 substrate winding chamber, 404,702 substrate, 701 substrate Roll, 407,709 Target, 405,707 Substrate heating heater, 409 Power supply, 420 Metal piece,

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Atsushi Shiozaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsumi Nakagawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Toshihiro Yamashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A semiconductor solar cell in which a back surface reflection layer, a semiconductor bonding layer, and a transparent electrode layer are sequentially laminated on a substrate having at least its surface made of a metal layer or an alloy layer, wherein the back surface reflection layer is an insulator. A semiconductor solar cell comprising a mixed film of a metal or an alloy. 2. A semiconductor solar cell in which a back surface reflection layer, a semiconductor bonding layer, and a transparent electrode layer are sequentially laminated on a substrate having at least its surface formed of a metal layer or an alloy layer, and the back surface reflection layer is a plurality of layers. And a layer in contact with the metal layer of the plurality of layers is made of a mixed film of an insulator and a metal or an alloy, and a plurality of layers other than the layer made of the mixed film is made of a transparent conductor. And semiconductor solar cells. 3. The insulator is made of any one of an oxide, a nitride, a fluoride, or a mixture thereof, and the metal is a noble metal, a noble metal alloy, Al, an Al alloy, C.
3. The semiconductor solar cell according to claim 1, wherein the semiconductor solar cell is made of any one of u and Cu-based alloys or a mixture thereof. 4. The semiconductor solar cell according to claim 1, wherein a mixing volume ratio of the insulator and the metal or the metal is in a range of 1: 2 to 1: 200.