JP3162261B2 - Solar cell manufacturing method and manufacturing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a solar cell, and more particularly to a method and an apparatus for manufacturing a solar cell capable of mass-producing a high-performance and low-cost solar cell.

[0002]

2. Description of the Related Art At present, energy consumed by humankind largely depends on thermal power generation using fossil fuels such as oil and coal, and nuclear power generation. However, to fossil fuels that cause global warming due to carbon dioxide generated during use, or to nuclear power, which can not be said to have no radiation danger even during normal operation as well as accidental accidents,
It will be problematic to rely entirely on the future. Therefore,
Attention has been paid to photovoltaic power generation using solar cells that have very little influence on the global environment, and further spread is expected.

[0003] However, in the current state of photovoltaic power generation, there are some problems that hinder full-scale spread.
Conventionally, monocrystalline or polycrystalline silicon has been often used in solar cells for photovoltaic power generation. However, these solar cells require a lot of energy and time to grow crystals,
In addition, since a complicated process is required thereafter, it is difficult to increase mass productivity, and it is difficult to provide the device at low cost. On the other hand, amorphous silicon (hereinafter a-Si), CdS, Cu
So-called thin-film semiconductor solar cells using compound semiconductors such as InSe 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.
The manufacturing process is relatively simple, and there is a possibility that the price can be reduced.

[0004] However, thin-film solar cells have not been used in earnest because their conversion efficiency is lower than that of crystalline silicon solar cells, and their reliability for long-term use is uneasy. In order to solve such a problem and improve the performance of the thin-film solar cell, various measures described below have been made.

One of them is to increase the reflectance of light on the substrate surface in order to return the sunlight that could not be absorbed by the thin film semiconductor layer to the thin film semiconductor layer again, that is, to use incident light more effectively. This is to provide a back reflection layer. For this purpose, when sunlight is incident from the substrate side using a transparent substrate, a metal having high reflectivity such as silver (Ag), aluminum (Al), copper (Cu), etc. The electrode is formed by using. On the other hand, when sunlight is incident from the surface of the thin film semiconductor layer, a semiconductor layer may be formed after forming a similar metal layer on a substrate.

Further, by interposing a transparent layer having appropriate optical properties between the metal layer and the thin film semiconductor layer,
For example, as shown in FIGS. 1A and 1B, the reflectance can be further increased by the multiple interference effect. FIG. 1 (a)
FIG. 1B shows a case where a-Si is formed on a metal.
Is a result of a simulation showing respective reflectances when zinc oxide (ZnO) is interposed as a transparent layer between a-Si and various metals.

The use of such a transparent layer is also effective in improving the reliability of a thin-film solar cell. For example, Japanese Patent Publication No. 60-41878 discloses that the use of a transparent layer can prevent alloying between a semiconductor and a metal layer. In U.S. Pat. Nos. 4,532,372 and 4,598,306, an excessive current flows between electrodes even when a short circuit occurs in a semiconductor layer by using a transparent layer having an appropriate resistance. There is a statement that it can be prevented from flowing.

Another method for improving the conversion efficiency of a thin-film solar cell is a method in which the interface between the reflective layer and the semiconductor layer on the front surface and / or back surface of the solar cell is made to have fine irregularities (texture structure). By adopting such a configuration, sunlight is scattered at the interface between the front and / or back reflection layers of the solar cell and the semiconductor layer, and further confined inside the semiconductor (light trapping effect). It can be effectively absorbed. For example, when sunlight is incident from the substrate side using a transparent substrate, tin oxide (SnO ₂ ) on the substrate is used.
It is known that the surface of a transparent electrode, such as the one having a textured structure, can be made to have a textured structure when the sunlight enters from the surface of the thin film semiconductor, and the surface of the metal layer used for the back reflection layer can be made a textured structure. I have.

M.Hirasaka, K.Suzuki, K.Nakatani, M.As
ano, M.Yano and H.Okaniwa show that a texture structure for the backside reflective layer can be obtained by depositing Al by adjusting the substrate temperature and deposition rate (Solar Cell Materials)
20 (1990) pp99-110). FIG. 2 shows an example in which the absorption of incident light is increased by using the back reflection layer having such a texture structure. Here, the curve (a) shows the spectral sensitivity of an a-Si solar cell using smooth Ag as the metal layer, and the curve (b) shows the spectral sensitivity when textured Ag is used.

From the above, in order to obtain a higher conversion efficiency,
It is conceivable to combine the above-described concept of the back surface reflection layer including the two layers of the metal layer and the transparent layer with the concept of the texture structure. U.S. Pat. No. 4,419,533 discloses a back reflection layer in which the surface of a metal layer has a textured structure and a transparent layer is formed thereon. Such a combination is expected to significantly improve the conversion efficiency of the solar cell.

[0011]

However, in order to improve the conversion efficiency of the solar cell, it is desirable that the texture period is 0.5 μm or more. In this case, it is necessary to reduce the deposition rate and further increase the film thickness. Therefore, a long time is required for the film formation by the batch method, and a large number of targets are required in a so-called roll-to-roll type sputtering in which a long substrate is transported in a longitudinal direction and continuously deposited. As a result, the size of the apparatus is increased. As described above, in order to enhance mass productivity, the feasibility is poor at present considering the size and handling of the apparatus.

Further, in order to obtain a back reflection layer having a high reflectance as described above, it is necessary to increase the thickness of the metal layer and reduce the deposition rate. Ag having a high reflectance is suitable as a material for the metal layer. However, since Ag is an expensive metal, if Ag is deposited thickly, the material cost increases, which hinders the cost reduction of the solar cell. Further, when the deposition rate is lowered, mass productivity is deteriorated, and there is a problem in equipment. That is, it is difficult to provide a high-performance and cheaper solar cell to the market by the conventional method.

The present invention has been made in view of the above-mentioned points, and provides a method of manufacturing a solar cell capable of manufacturing a back reflection layer having a high reflectance with high mass productivity, and a manufacturing apparatus which can be used for the method. The purpose is to provide.

It is another object of the present invention to provide a method of manufacturing a solar cell which has a low material cost and which can meet the demand for cost reduction, and which has higher performance and is less expensive. Another object of the present invention is to provide a manufacturing method having a small occupied area.

[0015]

According to a method for manufacturing a solar cell of the present invention, a method for manufacturing a solar cell, comprising forming at least a metal layer, a semiconductor layer, and a transparent electrode on a substrate, comprises:
Composed of at least two layers of said metal layer the first metal layer and second metal layer, after forming the first metal layer, annealing treatment
Agglomerated particles of the first metal layer are generated by
0.5μm or more texture circumference partially formed on
Forming a texture structure having a period, the second gold
Forming a metal layer, forming 10 ^-6 to 10 on the second metal layer
Forming a transparent layer having a resistance of Ω / cm ² .

Further , the apparatus for manufacturing a semiconductor device of the present invention comprises:
An apparatus for manufacturing a semiconductor device having a substrate delivery chamber, a first metal layer formation chamber, a substrate heating chamber for annealing treatment , and a second metal layer formation chamber in this order , wherein the substrate heating chamber is a substrate To
A roller for conveying along the outer circumference of the roller,
And a heater along the line.

[0017]

The operation and embodiments of the present invention will be described below in detail with reference to experiments performed in the course of completing the present invention.

A method for manufacturing a solar cell according to the present invention will be described with reference to a solar cell having a structure shown in a schematic sectional view in FIG. 3 as an example. In the figure, 101 is a substrate, 102 is a first metal layer, 10
3 is a second metal layer, 104 is a transparent layer, 105 is a semiconductor layer region, 106 is n-type amorphous silicon (a-Si)
Layer, 107 is an i-type a-Si layer, 108 is a P-type a-Si
The layer, 109 is a transparent electrode, and 110 is a pyroelectric electrode.

The solar cell shown in FIG. 3 has a first metal layer 102 partially formed on a substrate 101, and formed on and / or around the first metal layer 102. A second metal layer 103, and a transparent layer 104 on the second metal layer 103. A semiconductor layer region 105 is formed on the transparent layer 104, and the semiconductor layer region 105 is an n-type a-S
i-layer 106, i-type a-Si layer 107, n-type a-Si layer 1
08 have a so-called pin structure formed in this order. The transparent electrode 10 is formed on the semiconductor layer region 105.
In order to efficiently collect the electricity generated by the power supply 9, a current collecting electrode 110 is provided on the transparent electrode 109.

The solar cell having such a configuration is formed, for example, as follows. First, a first metal layer 102, a second metal layer 103, and a transparent layer 104 are formed on a substrate 101 to form a back reflection layer. Substrate 101 used in the present invention
Preferably, at least the surface is conductive, and for example, a metal substrate is more preferable, and a metal substrate or the like having a non-conductive support surface is preferably plated. After the first metal layer 102 is formed on the substrate 101 and then annealed, the aggregated particles 102 of the first metal layer are generated to form a texture structure. Depending on the film forming conditions, a fine texture structure may be formed even without annealing, but the annealing process may eventually produce a 0.5 μm
A texture structure having the above-described texture period can be obtained.

Further, a second metal layer 1 having a high reflectivity is further formed thereon.
03 is formed to increase the reflectance of the back reflection layer. A transparent layer 104 is formed thereon. The transparent layer is transparent to sunlight transmitted through the thin film semiconductor layer. In addition, it has an appropriate electric resistance, and its surface has a texture structure.
Further, it is preferable that it has chemical resistance to an etchant used in a subsequent step.

Subsequently, a thin-film semiconductor layer region 105 is formed on the above-mentioned back reflection layer. FIG. 3 shows an example in which a pin-type a-Si solar cell is used as the thin film semiconductor layer region as described above. That is, 106 is n-type a-Si, 1
07 is i-type a-Si, and 108 is p-type a-Si. When the thin film semiconductor layer region 105 is thin, the entire thin film semiconductor layer region often has the same texture structure as the transparent layer 104 as shown in FIG.

Finally, a transparent electrode 109, a current collecting electrode 110 and the like are formed to complete a solar cell. By using the above manufacturing method, (1) In order to obtain a back reflection layer having a high diffuse reflectance, conventionally, a metal layer had to be thickened. Is gone. The metal layer has a two-layer structure, and the first metal layer has C
By using an inexpensive metal such as u or Al, the manufacturing cost can be reduced. (2) Even if the deposition rate of the metal layer is not reduced, a texture structure in which the texture period has developed to 0.5 μm or more can be obtained by annealing for several minutes, so that mass productivity can be improved. (3) Since a back reflection layer having a high diffuse reflectance is obtained, a solar cell having a high conversion efficiency can be obtained as a result.

The metal used for the first metal layer of the present invention is preferably one that forms aggregated particles in an annealing step for several minutes. Specifically, for example, Au, Ag, Cu, Al, Mg
And its alloys. Further, the metal used for the second metal layer is preferably a metal having a reflectance of 85% or more with respect to light having a wavelength of 600 nm to 1200 nm.
1, Au, Ag, Cu and the like are preferably used. In particular, Ag having a reflectance of 98% or more is optimal. Although the case where the number of metal layers is two has been described so far, it goes without saying that three or more layers may be used as long as the effects of the present invention can be obtained.

It is to be noted that the first metal layer preferably has a thickness of 400 to 400 to form an effective texture structure.
It is formed to a thickness of 0 °, more preferably 600 ° to 2500 °, and annealed. The second metal layer may have at least a necessary reflection effect, for example, 350 °.
It is preferable to set the layer thickness to the above. However, considering the use of expensive materials such as Ag and the layer formation time, 1000
Å or less, more preferably 500 Å or more for more effective reflectivity and conductivity.

An experiment for demonstrating the operation and effect of the present invention will be described below. (Experiment 1) 5 cm × 5 by DC magnetron sputtering
Ag was deposited as a first metal layer on a stainless steel plate (SUS430) having a thickness of 2000 cm (at a deposition rate of 120 cm).
/ Sec). At this time, the substrate temperature was 200 ° C. This was annealed at 400 ° C. for 3 minutes in an atmosphere of 99.999% (5N) Ar flow rate of 1 liter / min. This is designated as Sample 1a.

Next, Cu, Al, M is used as the first metal layer.
A sample was prepared in the same manner as in Sample 1a using g, Zn, and Ni. Samples 1b, 1c, 1d, 1e, 1f, respectively
And

The six samples thus obtained were observed by SEM to examine the period of the texture. FIG. 4 shows the relationship between the texture cycle after annealing and the melting point of the metal. From FIG. 4, it can be seen that the texture period of the metal having a melting point of 1100 ° C. or less is 0.5 μm or more, and a good texture structure can be obtained.

On the other hand, when a metal having a low melting point is used for the first metal layer, mutual diffusion occurs when exposed to a temperature of 350 ° C. or more in the step after the deposition of the second metal layer, and the reflectance decreases. It turned out that there was a case. In light of the above results,
From the results of many experiments, the preferred melting point of the metal for the first metal layer is 650 to 1100 ° C.

(Experiment 2) The annealing temperature was set to 150 in Experiment 1.
C., 200 C., 400 C., 500 C., and 600 C., except that Samples 2a-1, 2a-2,
2a-3, 2a-4, and 2a-5 were produced.

In Experiment 1, the annealing temperature was set to 150 ° C.
Samples 2b-1, 2b-2, 2
b-3, 2b-4, and 2b-5 were produced.

Samples 2a-1 to 2a-5 and 2b-1 to 2
FIGS. 5A and 5B show the relationship between the irregular reflectance and the annealing temperature measured for b-5, respectively. FIG.
As shown in the graph, as the annealing temperature increases, the diffuse reflectance increases and the texture develops.

However, it was found that when the temperature exceeded 500 ° C., the substrate was distorted, and the adhesive strength of the film was sometimes reduced when the solar cell was used. Therefore, in view of this point, the annealing temperature is preferably in the range of 200 to 500C.

(Experiment 3) On the sample 1a produced in (Experiment 1), a substrate temperature of 200
Sample 3a was formed by further forming an Ag film at 600 ° C. at 600 ° C. For comparison, the substrate temperature was set to 500 ° C. and D
A sample 3b in which Ag was deposited at 4500 ° on a 5 × 5 cm stainless plate (SUS430) by a C magnetron sputtering method was produced.

Table 1 shows the results of measuring the reflectance of the above samples. As shown in Table 1, it was found that the reflectivity of Sample 3a was higher than that of Sample 3b, even though the film thickness was smaller, and that a more excellent texture structure was obtained by performing the annealing treatment.

[0036]

[Table 1]

(Experiment 4) The sample 1a formed in (Experiment 1) was used as a first metal layer, and an Ag600 layer was formed thereon as a second metal layer.
As a transparent layer, ZnO was formed at 10,000 °. Further, by the glow discharge decomposition method, the n-type a-Si layer was formed using SiH ₄ and PH ₃ as source gases at 200 °, the i-type a-Si layer using SiH ₄ as source gas at 4000 °, and SiH ₄ , BF ₃ and H ₂ were formed. A p-type microcrystalline (μc) Si layer was deposited at 100 ° as a source gas to form a thin film semiconductor junction. An 650 ° ITO film was deposited thereon as a transparent electrode by resistance heating evaporation. Further, a current collecting electrode having a width of 300 μm was formed thereon using a silver paste. The sample thus obtained is referred to as a sample 4a.

For comparison, a deposition rate of 60
Sample 4b was prepared in the same manner as Sample 4a, except that a back reflection layer with Ag of 4500 ° was deposited at Å / sec. The conversion efficiencies of the samples 4a and 4b were measured under a solar simulator of AM-1.5. As a result, the efficiency of the sample 4b was 9.0%, whereas the efficiency of the sample 4a manufactured by the manufacturing method according to the present invention was 9.6%, indicating that higher conversion efficiency was obtained.

Next, the back surface reflection layer used in the thin film semiconductor solar cell of the present invention will be described in more detail.

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

As described above, it is preferable to use a metal such as silver or aluminum having a high reflectance over the entire wavelength region, as described above, for the metal layer formed on the substrate such as stainless steel or zinc steel plate. However, the short wavelength component of the sunlight spectrum is already absorbed by the thin film semi-thin body, so it is sufficient if the reflectance is higher for light of longer wavelength. Which wavelength or more should reflectivity be high?
It depends on the light absorption coefficient and the film thickness of the thin film semiconductor used. For example, in the case of a-Si having a thickness of 4000 °, this wavelength is about 6000 °, and copper can be preferably used (FIG. 1).
(See (a) and (b)).

The metal layer of the present invention also functions as the other electrode (lower electrode) facing the transparent electrode. But,
If the resistance is high in the case of a glass or ceramic substrate, a conductive layer such as a metal may be further provided.

For deposition of the metal layer, 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 the like is used. The case of the sputtering method will be described as a preferable example of the film formation method. FIG. 6 shows a preferred example of the sputtering apparatus.

Reference numeral 801 denotes a deposition chamber, which can be evacuated by an exhaust pump (not shown). Inside this, an argon (Ar) gas is introduced from a gas introduction pipe 802 connected to a gas cylinder (not shown).
A predetermined flow rate of an inert gas or the like is introduced, the opening of the exhaust valve 803 is adjusted, and the inside of the deposition chamber 801 is set to a predetermined pressure. The substrate 804 is fixed to the surface of an anode 806 provided with a heater 805 inside. A cathode electrode 808 having a target 807 fixed to the surface thereof is provided opposite to the anode 806.

The target 807 is a block of metal to be deposited. Normally 99.9% to 99.99 purity
Although it is a pure metal of about 9%, a specific impurity may be introduced in some cases. The cathode electrode is connected to a power supply 809.

Power supply 809 generates radio frequency (RF)
Or a high voltage of direct current (DC) to generate plasma 810 between the cathode and the anode. The metal atoms of the target 807 are deposited on the substrate 804 by the action of the plasma. The deposition rate can be further increased by using a magnetron sputtering apparatus in which a magnet is provided inside the cathode 808 to increase the intensity of the plasma.

(Transparent layer and its texture structure) As the transparent layer, zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), cadmium oxide (CdO), tin oxide Cadmium (CdSnO
₄ ), Zn, In, Sn, C such as titanium oxide (TiO)
An oxide containing at least one metal selected from the group consisting of d and Ti is often used (however, the composition ratio of the compound shown here does not always match the actual state. The stoichiometric ratio is limited to the above. Is not.)

In general, the higher the light transmittance of the transparent layer, the better, but it is not necessary to be transparent for light in a wavelength range that is absorbed by the thin film semiconductor before reaching the transparent layer. It is preferable that the transparent layer has a resistance in order to suppress a current caused by a pinhole or the like, but the effect of the series resistance loss due to the resistance on the conversion efficiency of the solar cell must be negligible.

The range of resistance per unit area from such a point of view (1 cm ²⁾ is preferably 10 ^- a ^{6 ~10Ω,} more preferably 10 ^-5 ~3Ω, most preferably 10 ^-4 ~1Ω.

In order to control the specific resistance of the transparent layer, an appropriate impurity may be added. As the transparent layer of the present invention, the conductive oxide as described above tends to have a too low specific resistance. Therefore, it is preferable that the impurity be appropriately added to increase the resistance. For example, an acceptor-type impurity (for example, Cu, ZnO,
By adding an appropriate amount of SnO ₂ to Al or the like, it can be made intrinsic to increase the resistance. The addition of impurities can also enhance chemical resistance.

The thickness of the transparent layer is preferably as small as possible from the viewpoint of transparency. However, in order to obtain a texture structure on the surface, the average thickness is desirably 1000 ° or more. In some cases, a higher film thickness is required from the viewpoint of reliability.

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

To add an impurity to the transparent layer, a desired impurity may be added to an evaporation source or a target. In particular, a small piece of a material containing an impurity may be placed on a target in a sputtering method.

The reason why light confinement occurs due to the texture structure is that when the metal layer has a texture structure,
It is considered that light scattering occurs in the metal layer. Further, when the surface of the thin film semiconductor has a texture structure similar to that of the transparent layer, light scattering due to the phase difference of light easily occurs and the effect of the light trap is improved.

[0055]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. (Example 1) In this example, a pin type a-Si photovoltaic element having the structure shown in the schematic sectional view of FIG. 3 was manufactured.
Ag was further added on the sample 1a prepared in (Experiment 1) by 60%.
After the film is formed at a temperature of 250 ° C. using a ZnO target by the apparatus shown in FIG.
A ZnO layer 104 of 000 ° was deposited. The surface of ZnO had a texture structure.

Subsequently, the substrate 501 on which the lower electrode is formed
Was set on a mounting table 502 which is also an electrode of a commercially available capacitively coupled high-frequency CVD apparatus (CHJ-3030 manufactured by ULVAC, Inc.) shown in FIG. The evacuation pump 509 performed a rough evacuation and a high evacuation operation through the evacuation pipe of the reaction vessel 504. At this time, the temperature of the substrate was controlled by a temperature control mechanism so as to be 250 ° C.

At the point when exhaust is sufficiently performed, the gas supply
From step 505, the SiH_Four300 sccm, SiF_Four4
sccm, PH_Three/ H_Two(1% H_TwoDilution) 55scc
m, H _TwoIntroduce 40sccm of the throttle valve
By adjusting the opening, the internal pressure of the reaction vessel 504 becomes 1 Torr.
When the pressure is stabilized and the high-frequency power supply 5
From 2007, a power of 200 W was applied to the electrode 503. Plastic
The gap is maintained for 5 minutes, and the n-type a-Si layer 107 is
04.

After evacuating again, this time, 300 sccm of SiH ₄ , ₄ sccm of SiF _4, and ₄₀ sccm of H ₂
cm, the opening of the throttle valve was adjusted, the internal pressure of the reaction vessel was maintained at 1 Torr, and when the pressure was stabilized, 150 W of electric power was immediately supplied from the high frequency power supply 507. The plasma was maintained for 40 minutes to form an i-type a-Si layer on the n-type a-Si layer 106.

[0059] After the evacuated again, this time the SiH ₄ 5
0 sccm, 50 sccc of BF ₃ / H ₂ (1% H ₂ dilution)
m, introduced 500sccm of H _2, by adjusting the opening degree of the throttle valve, the internal pressure of the reaction vessel was maintained at 1 Torr, where the pressure is stabilized, 3 from the high frequency power supply immediately
The power of 00W was turned on. Sustain the plasma for 2 minutes,
A p-type μc-Si layer 108 was formed on the i-type a-Si layer 107.

Next, the sample was taken out from the high-frequency CVD apparatus, ITO was deposited by a resistance heating vacuum evaporation apparatus, and then a paste containing an aqueous solution of iron chloride was printed to obtain a desired transparent electrode 1.
09 pattern was formed. Further, the Ag paste was screen-printed to form the current collecting electrode 110, thereby completing the thin-film semiconductor solar cell.

According to this method, ten samples were prepared, and AM-
When the characteristics were evaluated under irradiation of 1.5 (100 mW / cm ² ) light, an excellent conversion efficiency of 9.5 ± 0.2% in photoelectric conversion rate was obtained with good reproducibility.

(Example 2) A back reflection layer was continuously formed using the apparatus shown in FIG. Here, the substrate delivery chamber 903 has a cleaned width of 350 mm, a thickness of 0.2 mm,
A stainless steel sheet roll 901 having a length of 500 m is set. From here, the stainless steel sheet 902 becomes the first metal layer deposition chamber 9 having the first metal target 908.
04, annealing chamber 909, second metal target 91
3 and a transparent layer deposition chamber 914 having a target 918 for forming a transparent layer, and then sent to the substrate winding chamber 917. Sheet 902
Are substrate heaters 907, 910, 91 in each deposition chamber.
At 2,915, it can be heated to a desired temperature.

The target 908 in the deposition chamber 904 is made of Al having a purity of 99.99%, and the sheet 90 heated to a substrate temperature of 150 ° C. by DC magnetron sputtering.
2, an Al layer was deposited at 2400 °.

Next, after being annealed at 300 ° C. by a heater 910 installed in an annealing chamber 909 and textured, the substrate is formed in a deposition chamber 911 using an Ag target 913 having a purity of 99.99% in the same manner as the Al layer. Temperature 15
Deposited 600 ° at 0 ° C.

The target 916 of the deposition chamber 914 is made of ZnO having a purity of 99.5% (0.5% is Cu).
Continued ZnO by DC magnetron sputtering
The layer was deposited at 10000 ° (substrate temperature 250 ° C.). The number of targets 918 was four in relation to the deposition rate and the desired film thickness. The sheet feeding speed was 20 cm per minute.

On this, a semiconductor layer, a transparent electrode, and a current collecting electrode are formed, and a pin having two pin structures of the structure shown in FIG.
A -Si / a-SiGe tandem solar cell was produced. Here, 201 is a substrate, 202-1 is a first metal layer, 202
-2 is a second metal layer, 203 is a transparent layer, 204 is a bottom cell, and 208 is a top cell. Further, 205, 20
9 is an n-type a-Si layer, 207 and 211 are p-type μc-S
i, 206 are i-type a-SiGe layers, 210 is i-type a-S
It is an i-layer. These thin film semiconductor layers are described in U.S. Pat.
Roll-to-two as described in US Pat.
It was manufactured continuously using a roll type film forming apparatus.

A transparent electrode 212 was deposited by a sputtering apparatus similar to the apparatus shown in FIG. 213 is a current collecting electrode. After patterning the transparent electrode and forming the current collecting electrode, the sheet 902 was cut. In this way, all the processes were continuously processed, and the mass productivity was improved.

In this way, 100 samples were prepared, and the AM
When the characteristics were evaluated under irradiation with 1.5 (100 mW / cm ² ) light, an excellent conversion efficiency of 11.3 ± 0.2% in photoelectric conversion efficiency was obtained with good reproducibility.

(Embodiment 3) FIG. 10 shows an improved annealing chamber of the apparatus shown in FIG. The manufacturing method is the same as that of the apparatus shown in FIG. 8, but the length of the apparatus and, consequently, the bottom area can be reduced by annealing with a heater 1010 provided along a roller 1018 provided in an annealing chamber 1009.

A semiconductor layer, a transparent electrode and a current collecting electrode were formed on the substrate treated by the apparatus shown in FIG. 8 in the same manner as in Example 2, and 100 similar solar cells were produced and evaluated in the same manner. As a result, a solar cell having an excellent photoelectric conversion efficiency of 11.2 ± 0.3% was obtained with good reproducibility.

[0071]

As described above, according to the present invention,
A back reflection layer having high light reflectance can be manufactured at low cost. As a result, a solar cell with high conversion efficiency can be manufactured at low cost.

Further, according to the present invention, since the characteristics of the back surface reflection layer can be further improved and formed stably, a solar cell having higher conversion efficiency can be stably provided.

Further, according to the present invention, it is possible to provide a manufacturing apparatus which can be suitably applied to a roll-to-roll type having a small occupied area, for example, a floor area. Thus, the present invention greatly contributes to the spread of solar cells.

The above-mentioned semiconductor layer may be a material containing microcrystals or a polycrystal in addition to an amorphous semiconductor such as a-Si. In other words, a non-single-crystal material may be used. good. It should be noted that the present invention is not limited to the above-described embodiment and description, and modifications and combinations can be appropriately made within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a graph for explaining a relationship between a reflectance and a wavelength.

FIG. 2 is a graph for explaining the effect of a texture structure on spectral sensitivity.

FIG. 3 is a schematic cross-sectional view for explaining a preferred example of the solar cell of the present invention.

FIG. 4 is a graph illustrating a relationship between texture periods due to annealing depending on a difference in melting point of a metal.

FIG. 5 is a graph illustrating a relationship between an annealing temperature and a reflectance.

FIG. 6 is a schematic cross-sectional view for explaining a configuration example of a preferred sputtering apparatus.

FIG. 7 is a schematic cross-sectional view for explaining a configuration example of a suitable plasma CVD (PCVD) apparatus.

FIG. 8 is a schematic cross-sectional view for explaining an example of a manufacturing apparatus suitably used in the present invention.

FIG. 9 is a schematic cross-sectional view for explaining a preferred example of the solar cell of the present invention.

FIG. 10 is a schematic cross-sectional view for explaining an example of a manufacturing apparatus suitably used in the present invention.

[Explanation of symbols]

101,201,501,804,902,1002
Substrate, 102, 202-1 First metal layer, 103, 202-2 Second metal layer, 104, 203 Transparent layer, 105 Semiconductor layer region, 106, 205, 209 n-type a-Si layer, 107, 210 i-type a-Si layer, 108 p-type a-Si layer, 109,212 transparent electrode, 110,213 current collecting electrode, 204 bottom cell, 206 i-type a-SiGe layer, 207,211 p-type μc-Si layer, 208 Top cell, 502,503 electrode, 504 reaction vessel, 505 gas supply means, 506 gas flow controller, 507,809 power supply, 508 pressure controller, 509 exhaust pump, 801 deposition chamber, 802 gas introduction pipe, 803 exhaust valve, 805,907,910,912,915,1007,
1010, 1012, 1015 substrate heater, 806 anode, 807, 908, 913, 916, 918, 1008,
1013, 1016 target, 808 cathode, 810 plasma, 901, 1001 substrate roll, 902 stainless sheet, 903, 1003 substrate delivery chamber, 904, 1004 first metal layer deposition chamber, 909, 1009 annealing chamber, 911, 1011 2, a metal layer deposition chamber, 914 a transparent layer deposition chamber, 917, 1017 a substrate winding chamber, and 1018 an annealing roller.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (14)

(57) [Claims] 1. A method for manufacturing a solar cell, comprising forming at least a metal layer, a semiconductor layer, and a transparent electrode on a substrate, wherein the metal layer comprises at least two layers of a first metal layer and a second metal layer. After the first metal layer is formed, aggregated particles of the first metal layer are generated by annealing treatment,
A step of forming a texture structure having a texture period of 0.5 μm or more partially formed on the substrate, a step of forming the second metal layer, and a step of forming a 10 ⁻⁶ layer on the second metal layer.
Forming a transparent layer having a resistance of 10 Ω / cm ^{2 to} 10 Ω / cm ² . 2. The method according to claim 1, wherein the first metal layer has a melting point of 650.degree.
The method for manufacturing a solar cell according to claim 1, comprising a metal or an alloy at 100 ° C. 3. The method according to claim 2, wherein the second metal layer has a wavelength of 600 to 12 nm.
The method for manufacturing a solar cell according to claim 1, comprising a metal having a reflectance of 85% or more for light of 00 nm. 4. The annealing treatment is performed at 200 to 500 ° C.
The method for manufacturing a solar cell according to claim 1, wherein 5. The method according to claim 1, wherein the first metal layer and the second metal layer are different metals. 6. The first metal layer is formed of Cu, Al, Mg,
The method for manufacturing a solar cell according to claim 1, comprising at least one element selected from the group consisting of Au and Ag. 7. The second metal layer is formed of Al, Au, Ag,
The method for manufacturing a solar cell according to claim 1, comprising at least one element selected from the group consisting of Cu. 8. The method for manufacturing a solar cell according to claim 1, wherein the thickness of the first metal layer before annealing is 400 ° to 4000 °. 9. The method according to claim 1, wherein the thickness of the transparent layer is 1000 ° or more. 10. The transparent layer is made of Zn, In, Sn, C
The method for manufacturing a solar cell according to claim 1, further comprising an oxide containing at least one metal selected from the group consisting of d and Ti. 11. The method according to claim 1, wherein the semiconductor layer has a pin semiconductor region in which a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are stacked. 12. The method according to claim 1, wherein the semiconductor layer comprises a non-single-crystal material. 13. An apparatus for manufacturing a semiconductor device having a substrate delivery chamber, a first metal layer formation chamber, a substrate heating chamber for annealing treatment, and a second metal layer formation chamber in this order. An apparatus for manufacturing a semiconductor device, comprising: a roller for transporting a substrate along an outer periphery thereof; and a heater along the roller. 14. The apparatus according to claim 13, further comprising a transparent layer deposition chamber after the second metal layer formation chamber.