JP2003298091A - Solar cell and its fabricating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy-to-fabricate solar cell exhibiting high conversion efficiency and its fabricating method. <P>SOLUTION: The solar cell has a pn junction defined by a p-type semiconductor layer 13 functioning as a light absorbing layer and an n-type semiconductor layer 14 formed thereon. The p-type semiconductor layer 13 is composed of a p-type compound semiconductor containing a group Ib element, a group IIIb element and a group VIb element, and the n-type semiconductor layer 14 is composed of an n-type compound semiconductor containing a group Ib element, a group IIIb element, a group VIb element and a dopant of a group II element. The n-type semiconductor layer 14 has a thickness of 10-40 nm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solar cell and a method for manufacturing the same.

[0002]

2. Description of the Related Art CuInSe ₂ (CIS), which is a compound semiconductor thin film (chalcopyrite structure compound semiconductor thin film) made of Ib group, IIIb group, and VIb group elements, or Cu (In, Ga) Se having Ga dissolved therein ₂ (CI
It has been reported that a thin film solar cell using GS) as a light absorption layer exhibits high energy conversion efficiency and has an advantage that the conversion efficiency does not deteriorate due to light irradiation or the like (hereinafter, referred to as CIS film or CIGS). The solar cells using the film may be collectively referred to as CIS solar cells).

In conventional high-efficiency CIS solar cells, CdS, Zn (O, S), etc. formed by a chemical deposition method are generally used as a buffer layer. In recent years, high-efficiency CIS solar cells that do not use a buffer layer have also been developed. In a solar cell that does not use a buffer layer, a group II element such as Zn, Cd, or Mg is added to the surface of the CIS film (or CIGS film) to form a homo-pn junction in which only the surface portion of the p-type semiconductor layer is n-typed. I am using.

[0004]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of various studies conducted by the inventors on such a homo-pn junction,
It has been newly found that the characteristics of a solar cell using such a pn junction vary greatly depending on the thickness of the n-type semiconductor layer.

The present invention has been made based on this new finding, and an object of the present invention is to provide a solar cell having high conversion efficiency and easy to manufacture, and a manufacturing method thereof.

[0006]

In order to achieve the above object, the solar cell of the present invention comprises a p-type semiconductor layer functioning as a light absorption layer and an n-type semiconductor layer laminated on the p-type semiconductor layer. A solar cell including a configured pn junction, wherein the p-type semiconductor layer comprises a group Ib element, a group IIIb element and VI.
The n-type semiconductor layer is made of a p-type compound semiconductor containing a b-group element, and the n-type semiconductor layer is made of an n-type compound semiconductor containing a Ib-group element, a IIIb-group element, a VIb-group element, and a II-group element as a dopant. The thickness of the semiconductor layer is 10 nm to 40 n
It is characterized by being m. In this solar cell, since the thickness of the n-type semiconductor layer is 10 nm to 40 nm, the carrier density of the n-type semiconductor layer is 1 × 10 ¹⁹ / cm ^3.
Even in the above case, high conversion efficiency can be maintained. Therefore, the allowable range of the concentration of the dopant added to form the n-type semiconductor layer is wide, and the manufacturing is easy.

The solar cell further includes a thin film laminated on the n-type semiconductor layer, and an electron affinity χ ₁ (eV) of the p-type semiconductor layer and an electron affinity χ ₂ (eV) of the thin film are 0 ≦. It is preferable to satisfy the relationship of (χ ₁ −χ ₂ ) <0.5. According to this structure, a highly efficient solar cell can be obtained.

In the above solar cell, the thin film is made of Zn and Mg.
It is preferable that the thin film contains a material represented by a composition formula Zn _1-x Mg _x O (0.05 ≦ x ≦ 0.35). According to this structure, a thin film satisfying the above electron affinity relationship can be easily formed.

In the solar cell, it is preferable that the thin film is a film formed by a sputtering method, and the p-type semiconductor layer and the n-type semiconductor layer are layers that are heat-treated after forming the thin film. According to this configuration, it is possible to recover damage that occurs in the semiconductor layer when the thin film is formed.

In the above solar cell, it is preferable that the carrier density of the n-type semiconductor layer is 1 × 10 ¹⁸ / cm ³ or more.

In the above solar cell, the n-type semiconductor layer is
The semiconductor layer is preferably formed by doping the p-type compound semiconductor with the Group II element. According to this structure, a homojunction can be easily formed.

In the above solar cell, the group II element is Zn,
At least one selected from Cd, Be, Mg and Ca
Preferably, it is one element.

In the above solar cell, the Ib group element is Cu.
And the IIIb group element is at least one element selected from In and Ga, and the VIb group element is Se.
It is preferably at least one element selected from S and S.

Further, the solar cell manufacturing method of the present invention includes a solar cell including a pn junction constituted by a p-type semiconductor layer functioning as a light absorption layer and an n-type semiconductor layer laminated on the p-type semiconductor layer. (I) forming a first semiconductor layer from a p-type compound semiconductor containing an Ib group element, a IIIb group element, and a VIb group element, and (ii) forming the first semiconductor layer. Supplying a group II element to the surface to form a p-type semiconductor layer and an n-type semiconductor layer by doping a part of the first semiconductor layer with the group II element. In the step (ii), the thickness of the n-type semiconductor layer is set to 10 nm to 40 nm. According to this manufacturing method, a high-efficiency solar cell can be easily manufactured with a wide allowable range of the concentration of the dopant added for forming the n-type semiconductor layer.

The above manufacturing method further includes (iii) a step of forming a thin film on the n-type semiconductor layer after the step (ii), and has an electron affinity χ of the p-type semiconductor layer.
₁ (eV) and the electron affinity χ ₂ (eV) of the thin film are 0 ≦
It is preferable to satisfy the relationship of (χ ₁ −χ ₂ ) <0.5.
According to this structure, a highly efficient solar cell can be manufactured.

In the above manufacturing method, the step (iii) is a step of forming the thin film containing Zn, Mg, and O by a sputtering method, and after the step (iii), (iv) the p It is preferable to further include a step of heat-treating a laminated film including the n-type semiconductor layer, the n-type semiconductor layer, and the thin film at a temperature in the range of 150 ° C to 250 ° C. According to this configuration, it is possible to recover damage that occurs in the semiconductor layer when forming the thin film.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In Embodiment 1, a solar cell of the present invention will be described. Solar cell 10 of Embodiment 1
A cross-sectional view of the above is shown in FIG.

Referring to FIG. 1, the solar cell 10 includes a substrate 1
1 and a first electrode film 12 sequentially stacked on the substrate 11,
A p-type semiconductor layer 13, an n-type semiconductor layer 14, a thin film 15 and a second electrode film 16, and extraction electrodes 17 and 18 are provided. The p-type semiconductor layer 13 and the n-type semiconductor layer 14 are adjacent to each other and form a pn junction.

As the substrate 11, a substrate generally used for solar cells can be applied. Specifically, a glass substrate, a stainless substrate, or a polyimide substrate can be used. Further, when the substrate 11 is a conductive substrate, an insulating layer may be formed on the surface thereof.

The first electrode film 12 is made of a conductive material and can be formed of Mo (molybdenum), for example.

The p-type semiconductor layer 13 is a semiconductor layer that functions as a light absorption layer, and contains a group Ib element, a group IIIb element and VIb.
It is made of a p-type compound semiconductor containing a group element. Cu can be used as the Ib group element. In the group IIIb element is In
And at least one element selected from Ga can be used. As the VIb group element, at least one element selected from Se and S can be used. Specifically, the p-type semiconductor layer 13 includes CuInSe ₂ , Cu (I
It can be formed of n, Ga) Se ₂ or a semiconductor in which a part of these Se is replaced with S.

The n-type semiconductor layer 14 is composed of a group Ib element and a group IIIb.
It is composed of an n-type compound semiconductor containing a group element, a VIb group element, and a group II element as a dopant. As the Ib group element, the IIIb group element, and the VIb group element, the elements described for the p-type semiconductor layer 13 can be used. For group II elements, Z
At least one element selected from n, Cd, Be, Mg and Ca can be used. n-type semiconductor layer 14
Is a p-type compound semiconductor forming the p-type semiconductor layer 13
It can be formed by adding a group element. As described in the embodiments below, the group II element is preferably supplied by a vapor deposition method.

The thickness of the n-type semiconductor layer 14 is 10 nm to 40 nm (preferably 10 nm to 30 nm). The carrier density of the n-type semiconductor layer 14 is 1 × 10 ^18.
/ Cm ³ or more is preferable. n-type semiconductor layer 14
With a thickness of 10 nm to 40 nm and a carrier density of 1 × 10 ¹⁸ / cm ³ or more, a particularly high conversion efficiency can be achieved.

The thin film 15 has an electron affinity χ ₂ (eV).
And the electron affinity χ ₁ (eV) of the p-type semiconductor layer 13 are 0
It is a thin film that satisfies the relationship of ≦ (χ ₁ −χ ₂ ) <0.5. The thin film 15 can be formed of, for example, a compound containing Zn, Mg, and O, and specifically, the composition formula Zn _1-x Mg _x O (0.05
It can be formed of a material represented by ≦ x ≦ 0.35). Thin film 1
5 can be formed by a sputtering method. When the thin film 15 is formed by the sputtering method, the p-type semiconductor layer 13 and the n-type semiconductor layer 14 are formed after the thin film 15 is formed because the n-type semiconductor layer 14 is damaged when the thin film 15 is formed.
Is preferably heat treated. Preferred heat treatment conditions will be described in the second embodiment.

The second electrode film 16 can be formed of a translucent conductive material, for example, ITO (Indium Tin).
Oxide). Further, the extraction electrodes 17 and 18 can be made of metal.

In the solar cell of Embodiment 1, the n-type semiconductor layer has a thickness of 10 nm to 40 nm. The inventors simulated the solar cell shown in FIG. 1 and calculated the change in conversion efficiency of the solar cell when the thickness and carrier density of the n-type semiconductor layer 14 were changed. The result is shown in FIG. As is clear from FIG. 2, when the thickness of the n-type semiconductor layer was 50 nm, the conversion efficiency was significantly reduced when the carrier density was 1 × 10 ¹⁹ / cm ³ or more. On the other hand, the thickness of the n-type semiconductor layer is 10 nm.
Or 40 nm, the carrier density is 1 × 1.
Even if it was 0 ¹⁹ / cm ³ or more, the decrease in conversion efficiency was small. As described above, by setting the thickness of the n-type semiconductor layer to 10 nm to 40 nm, the allowable range of the dopant concentration of the n-type semiconductor layer is widened, and the manufacture of a highly efficient solar cell is facilitated.

The solar cell 10 shown in FIG. 1 is an example, and the solar cell of the present invention is not limited to the configuration shown in FIG.
For example, the solar cell of the present invention may include other layers not shown in FIG. The solar cell of the present invention may be an integrated solar cell in which a plurality of unit cells are connected in series on a substrate.

(Second Embodiment) In a second embodiment, a method for manufacturing a solar cell of the present invention will be described. According to the manufacturing method of the second embodiment, the solar cell described in the first embodiment can be manufactured. Hereinafter, a method for manufacturing the solar cell 10 will be described with reference to FIG.

First, the first electrode film 12 is formed on the substrate 11. The first electrode film 12 can be formed by a sputtering method or a vapor deposition method. Next, as shown in FIG. 3A, a first semiconductor layer 31 is formed on the first electrode film 12 by a p-type compound semiconductor containing an Ib group element, a IIIb group element, and a VIb group element. (Step (i)). The first semiconductor layer 31 is
It can be formed of the same p-type compound semiconductor as the p-type semiconductor layer 13. The first semiconductor layer 31 can be formed by a vapor deposition method or a sputtering method.

Next, by supplying a group II element to the surface of the first semiconductor layer 31, as shown in FIG. 3 (b),
Part of the first semiconductor layer 31 is doped with a group II element to form the p-type semiconductor layer 13 and the n-type semiconductor layer 14 (step (ii)). That is, the portion of the first semiconductor layer 31 doped with the group II element is the n-type semiconductor layer 1
4 and the part where the II group element is not doped is p
Form the semiconductor layer 13. Group II elements to be doped include
The elements described in Embodiment 1 can be used. The Group II element is preferably supplied to the surface of the first semiconductor layer 31 by a vapor deposition method.

In step (ii), the thickness of the n-type semiconductor layer 14 formed, that is, the penetration depth of the group II element is
It is 10 nm to 40 nm (preferably 10 nm to 30 nm). The thickness of the formed n-type semiconductor layer 14 can be controlled by the substrate temperature during vapor deposition of the group II element. The substrate temperature is preferably in the range of 270 ° C to 320 ° C. The carrier density of the formed n-type semiconductor layer 14 is preferably 1 × 10 ¹⁸ / cm ³ or more. This carrier density can be controlled by the deposition time of the dopant. The vapor deposition time is preferably in the range of 5 minutes to 15 minutes.

Next, as shown in FIG. 3C, a thin film 15 is formed on the n-type semiconductor layer 14 (step (iii)). The thin film 15 can be formed by a sputtering method. As described in the first embodiment, the thin film 15 is a film containing, for example, Zn, Mg, and O, and has, for example, a composition formula Zn _1-x Mg _x O (0.0
It can be formed of a material represented by 5 ≦ x ≦ 0.35).

Next, as shown in FIG. 3D, the thin film 15
A second electrode film 16 is formed on top, and extraction electrodes 17 and 18 are formed. Before forming the take-out electrode 17, a part of the laminated film is removed to expose the first electrode film 12. The second electrode film 16 can be formed by a sputtering method. The extraction electrodes 17 and 18 can be formed by, for example, an electron beam evaporation method.

Then, the laminated film 32 (actually the entire solar cell) including the p-type semiconductor layer 13, the n-type semiconductor layer 14 and the thin film 15 is heat-treated (annealed) at a temperature in the range of 150 ° C. to 250 ° C. (anneal). Step (iv)). The preferable time of the heat treatment depends on the temperature of the heat treatment, but is, for example, about 5 minutes to 15 minutes. The heat treatment is preferably performed in an inert gas atmosphere. The heat treatment in step (iv) is
It may be performed after forming the thin film 15, and the second electrode film 1
It may be performed before forming 6.

According to the manufacturing method of the second embodiment, the solar cell described in the first embodiment can be easily manufactured.

[0037]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 In Example 1, a Cu (In, Ga) Se ₂ film was formed by a vapor deposition method, and Zn was added to the surface of the Cu (In, Ga) Se ₂ film by a vapor deposition method. An example of forming the n-type semiconductor layer will be described.

First, a Mo film is formed on a glass substrate by a sputtering method, and Cu (I
An n, Ga) Se ₂ film (film thickness: 2 μm) was formed. Then, the substrate temperature is set to 280 ° C., Zn is added for 3 minutes, and Cu (I
By depositing on the n, Ga) Se ₂ film, Cu (I)
Zn was added to the surface of the n, Ga) Se ₂ film. When the temperature of the Zn crucible as the vapor deposition source was 290 ° C. and the vapor-deposited sample was subjected to SIMS measurement, Cu (I
Zn from the surface of the n, Ga) Se ₂ film to a depth of 20 nm
Was found to be added.

On the other hand, SIMS measurement was performed on a sample that had been vapor-deposited for 3 minutes at a substrate temperature of 280 ° C. and a Zn crucible temperature of 310 ° C. As a result, the depth at which Zn was added was It was 20 nm as in the case where the temperature was 290 ° C. However, the Zn signal intensity was stronger than when the crucible temperature was 290 ° C.

Further, the substrate temperature is set to 330 ° C. and Zn is set to 3
Min., A Cu (In, Ga) Se ₂ film is vapor-deposited, and Cu (I
Zn was added to the surface of the n, Ga) Se ₂ film. When the temperature of the Zn crucible as the vapor deposition source was 290 ° C. and the vapor-deposited sample was subjected to SIMS measurement, Cu (I
Zn up to a depth of 50 nm from the surface of the n, Ga) Se ₂ film
Was found to be added.

For a sample which was vapor-deposited at a substrate temperature of 330 ° C. and a Zn crucible temperature of 310 ° C. for 3 minutes, S
When the IMS measurement was performed, the depth at which Zn was added was 50, which was the same as when the temperature of the Zn crucible was 290 ° C.
was nm. However, the Zn signal intensity was stronger than when the crucible temperature was 290 ° C.

As a result of repeated experiments, the Zn beam flux fluctuated even when the crucible temperature was constant, but the Zn doping depth was constant if the substrate temperature was the same. Therefore, it has been found that the depth at which Zn is doped (the thickness of the n-type semiconductor layer) can be controlled by controlling the substrate temperature.

Although the case where Zn was added was described in Example 1, Cd, Be, Mg or Ca was used instead of Zn.
Similar results were obtained when using.

Example 2 In Example 2, an example of producing a solar cell using the method of the present invention will be described.

First, a Mo film is formed on a glass substrate by a sputtering method, and Cu (I
An n, Ga) Se ₂ film (film thickness: 2 μm) was formed. Then, the substrate temperature is set to 280 ° C., the temperature of the Zn crucible that is the vapor deposition source is set to 300 ° C., and Cu (In, Ga) is used for 3 minutes.
Depositing a Zn to Se ₂ film, it was added Zn from Cu (In, Ga) Se ₂ film surface up to a depth of 20 nm. Thus, a p-type Cu (In, Ga) Se ₂ layer and an n-type semiconductor layer in which Zn was doped were formed.

Next, Zn was formed on the n-type semiconductor layer by a binary sputtering method using ZnO and MgO targets.
_{A 0.9} Mg _0.1 O film (film thickness: 100 nm) was formed. The sputter has an argon gas pressure of 2.7 Pa (2 × 10 ^-2 To
rr), the high frequency power applied to the ZnO target is 2
At 00W, the high frequency power applied to the MgO target is 1
It was performed under the condition of 00W.

Next, an ITO film (film thickness: 100 nm) as a transparent conductive film was formed on the Zn _0.9 Mg _0.1 O film by the sputtering method. The sputter has an argon gas pressure of 1.1.
High frequency power of 400 at Pa (8 × 10 ^-3 Torr)
It was conducted under the condition of W. After that, a NiCr film and an Ag film were laminated by an electron beam evaporation method to form an extraction electrode. The solar cell manufactured in this manner was irradiated with pseudo sunlight of AM 1.5 and 100 mW / cm ² to measure solar cell characteristics.

Next, the solar cell was placed in a nitrogen atmosphere at 200 ° C.
And heat treated for 10 minutes. Then, the solar cell after the heat treatment was irradiated with pseudo sunlight of AM 1.5 and 100 mW / cm ² to measure the solar cell characteristics. As a result, the short circuit current was 34.0 mA / cm ² , the open circuit voltage was 0.610 V, the fill factor was 0.671, and the conversion efficiency was 13.9%. on the other hand,
The characteristics of the solar cell before heat treatment are as follows: short-circuit current 29.6 mA /
cm ² , open-circuit voltage 0.529 V, fill factor 0.591,
The conversion efficiency was 9.25%. In Example 2, the Zn _0.9 Mg _0.1 O film (thin film 15) was formed by the sputtering method, and sufficient solar cell characteristics could not be obtained without heat treatment. However, when the thin film 15 is formed by a method other than the sputtering method or a sputtering method in which damage to the semiconductor layer is reduced, sufficient characteristics may be obtained without heat treatment.

When the substrate temperature was 280 ° C. and Zn was added, the beam intensity of Zn monitored by the beam flux monitor fluctuated each time the film was formed, but a solar cell having the above-described characteristics with good reproducibility was obtained. I was able to make it.

In this embodiment, the case where Zn is added has been described. However, instead of Zn, Cd, Be, Mg or Ca is used.
Similar results were obtained when was used.

Although the embodiments of the present invention have been described above with reference to examples, the present invention is not limited to the above embodiments and can be applied to other embodiments based on the technical idea of the present invention. .

[0053]

As described above, according to the solar cell and the method for manufacturing the same of the present invention, a solar cell having higher efficiency and easier to manufacture than the conventional CIS solar cell can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a solar cell of the present invention.

FIG. 2 is a graph showing the relationship between the thickness and carrier density of an n-type semiconductor layer and the conversion efficiency of a solar cell.

FIG. 3 is a process sectional view showing an example of a method for manufacturing a solar cell according to the present invention.

[Explanation of symbols]

10 solar cells 11 board 12 First electrode film 13 p-type semiconductor layer 14 n-type semiconductor layer 15 thin film 16 Second electrode film 17, 18 Extraction electrode 18 Extraction electrode 31 First semiconductor layer 32 laminated film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sato ▲ Takuya             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5F051 AA10 AA16 BA14 CA12 CB15                       CB18 CB24 DA03 DA20 FA04                       FA06 GA03                 5F103 AA01 DD30 HH01 HH10 JJ01                       JJ03 KK04 KK10 LL04 RR05

Claims (12)

[Claims] 1. A solar cell including a pn junction composed of a p-type semiconductor layer functioning as a light absorption layer and an n-type semiconductor layer laminated on the p-type semiconductor layer, wherein the p-type semiconductor layer is An n-type compound semiconductor including a p-type compound semiconductor containing a group Ib element, a group IIIb element, and a group VIb element, wherein the n-type semiconductor layer contains a group Ib element, a group IIIb element, a group VIb element, and a group II element serving as a dopant. A solar cell comprising a compound semiconductor, wherein the n-type semiconductor layer has a thickness of 10 nm to 40 nm. 2. A thin film laminated on the n-type semiconductor layer, wherein the electron affinity χ ₁ (eV) of the p-type semiconductor layer and the electron affinity χ ₂ (eV) of the thin film are 0 ≦ (χ ₁ −χ ₂ ) <0.
The solar cell according to claim 1, wherein the relationship of 5 is satisfied. 3. The solar cell according to claim 2, wherein the thin film contains Zn, Mg and O. 4. The composition formula Zn _1-x Mg _x O
The solar cell according to claim 3, comprising a material represented by (0.05 ≦ x ≦ 0.35). 5. The sun according to claim 4, wherein the thin film is a film formed by a sputtering method, and the p-type semiconductor layer and the n-type semiconductor layer are layers heat-treated after forming the thin film. battery. 6. The carrier density of the n-type semiconductor layer is 1 ×
The solar cell according to claim 1, which has a density of 10 ¹⁸ / cm ³ or more. 7. The solar cell according to claim 1, wherein the n-type semiconductor layer is a semiconductor layer formed by doping the p-type compound semiconductor with the group II element. 8. The group II element is Zn, Cd, Be, Mg
The solar cell according to claim 7, wherein the solar cell is at least one element selected from Ca and Ca. 9. The group Ib element is Cu, and the group III
9. The solar cell according to claim 1, wherein the b-group element is at least one element selected from In and Ga, and the VIb-group element is at least one element selected from Se and S. 9. 10. A method of manufacturing a solar cell comprising a pn junction constituted by a p-type semiconductor layer functioning as a light absorption layer and an n-type semiconductor layer laminated on the p-type semiconductor layer, comprising: (i) A step of forming a first semiconductor layer from a p-type compound semiconductor containing a group Ib element, a group IIIb element and a group VIb element; and (ii) supplying a group II element to the surface of the first semiconductor layer. Forming a p-type semiconductor layer and an n-type semiconductor layer by doping a part of the first semiconductor layer with the Group II element, wherein in the step (ii), the n-type semiconductor layer is formed. A method for manufacturing a solar cell, wherein the thickness of the semiconductor layer is 10 nm to 40 nm. 11. After the step (ii), (iii)
The method may further include the step of forming a thin film on the n-type semiconductor layer, wherein the electron affinity χ ₁ (eV) of the p-type semiconductor layer and the electron affinity χ ₂ (eV) of the thin film are 0 ≦ (χ ₁ −χ _2). ) <0.
The method for manufacturing a solar cell according to claim 10, wherein the relationship of 5 is satisfied. 12. The step (iii) comprises Zn, Mg and O.
A step of forming the thin film by a sputtering method including
After the step (iii), the method further includes (iv) a step of heat-treating the laminated film including the p-type semiconductor layer, the n-type semiconductor layer, and the thin film at a temperature in the range of 150 ° C to 250 ° C. The method for manufacturing a solar cell according to claim 11.