JP2000332273A - Solar battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar battery having a high voltage characteristic by forming a compound semiconductor thin film between a light absorbing layer and a buffer layer, the semiconductor thin film having a large energy difference between the bottom of a conduction band and a Fermi level. SOLUTION: This solar battery includes a substrate 11, and a lower electrode film 12, a compound semiconductor thin film 13, a compound semiconductor thin film 14, a compound thin film (buffer layer) 15, a window layer 16 and an upper electrode film 17 which are laminated sequentially on the substrate 11. The film 13 is a semiconductor thin film which functions as a light absorbing layer, and contains a group Ib element, a group IIIb element, and a group VIb element. The film 14 contains a group Ib element, a group IIIb element, and a group VIb element and also contains sulfur at a higher composition ratio than that of the film 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell using a compound semiconductor thin film 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) comprising a group Ib element, a group IIIb element, and a group VIb element, or Cu (In, Ga) Se in which Ga is dissolved in solid form. ₂ (C
It has been reported that a thin-film solar cell using (IGS) as a light absorption layer has an advantage that it exhibits high energy conversion efficiency and does not deteriorate conversion efficiency due to light irradiation or the like.

In a conventional CIS or CIGS solar cell, a buffer layer is generally formed on a CIS film or a CIGS film formed by a vapor deposition method or a selenization method by a chemical deposition method or the like.

FIG. 7 shows an example of a conventional solar cell. As shown in FIG. 7, a conventional solar cell 1 has a substrate 2, a back electrode 3 laminated on the substrate 2, and a p
It includes a type compound semiconductor thin film 4, a buffer layer 5, a ZnO film 6, and a transparent conductive film 7. The buffer layer 5 is made of Zn (O, O
H, S).

In a conventional solar cell 1, a CIS film or C
A pn junction is formed between the p-type compound semiconductor thin film 4 made of an IGS film and the buffer layer 5. Solar cell characteristics are greatly affected by band matching of these stacked semiconductors. Therefore, various combinations and arrangements of semiconductor thin films have been conventionally studied.

[0006]

However, in the above conventional solar cell 1, the energy difference between the bottom of the conduction band of Zn (O, OH, S) and the Fermi level is small (see FIG. 3). Has a problem that the voltage characteristics are not sufficient.

According to the present invention, a compound semiconductor thin film having a large energy difference between the bottom of the conduction band and the Fermi level is formed between a buffer layer and a CIS film (or a CIGS film) in order to solve the above-mentioned conventional problems. Accordingly, it is an object to provide a solar cell having good voltage characteristics.

[0008]

In order to achieve the above object, a solar cell according to the present invention is a solar cell comprising an upper electrode film and a lower electrode film, wherein the upper electrode film, the lower electrode film, Between the first and second electrodes sequentially arranged from the lower electrode film side.
A compound semiconductor thin film, a second compound semiconductor thin film, and a compound thin film, wherein the first compound semiconductor thin film is Ib
A group III element, a group IIIb element and a group VIb element,
The compound semiconductor thin film of Ib group element, IIIb group element and VI
and a group b element and sulfur (S) at a higher composition ratio than the first compound semiconductor thin film (including the case where the first compound semiconductor thin film does not contain sulfur). Here, the energy difference E ₂ from the Fermi level of the second compound semiconductor thin film to the bottom of the conduction band is larger than the energy difference E ₁ from the Fermi level of the first compound semiconductor thin film to the bottom of the conduction band. Thus, a solar cell having good voltage characteristics can be obtained.

In the above solar cell of the present invention, the compound thin film is made of ZnO, ZnS, ZnSe, Zn (O, OH),
Zn (O, OH, S), Zn (O, Se), Zn (O,
OH, Se) and Zn _x Mg _Y O (where 0 <X <
It is preferable that the material be at least one compound selected from 1, 0 <Y <1). Thus, a solar cell in which the buffer layer does not contain Cd and has good voltage characteristics can be obtained.

In the solar cell according to the present invention, the Ib group element contained in the first and second compound semiconductor thin films is Cu, and the IIIb group element contained in the first and second compound semiconductor thin films. The element is preferably at least one element selected from In and Ga. Thereby, a solar cell having high characteristics can be obtained.

In the solar cell of the present invention, the group VIb element contained in the first compound semiconductor thin film is Se, and the group VIb element contained in the second compound semiconductor thin film is sulfur. preferable. By setting the group VIb element contained in the first compound semiconductor thin film to Se, a semiconductor thin film suitable for a light absorption layer can be obtained. Further, by making the Group VIb element contained in the second compound semiconductor thin film sulfur, the energy difference between the bottom of the conduction band of the second compound semiconductor thin film and the Fermi level becomes particularly large, and a solar cell having good voltage characteristics is obtained. A battery is obtained.

[0012] In the solar cell of the present invention, it is preferable that the second compound semiconductor thin film contains a group II element. Thereby, a solar cell having high characteristics can be obtained.

In the above solar cell of the present invention, the group II element is preferably at least one element selected from Mg, Ca, Zn and Cd. As a result, a solar cell having particularly high characteristics can be obtained.

In the solar cell according to the present invention, the first compound semiconductor thin film may include the group Ib element, the group IIIb element, and the group VIb element in A: B: C (where 0.15 ≦ C).
A ≦ 0.35, 0.15 ≦ B ≦ 0.35, 0.4 ≦ C ≦
0.6), and the second compound semiconductor thin film includes the group Ib element, the group IIIb element, and the group VIb element in a ratio of D: E: F (where 0.15 ≦ D ≦ 0. 35,
0.15 ≦ E ≦ 0.35, 0.4 ≦ F ≦ 0.6). Thereby, a solar cell having high characteristics can be obtained.

In the solar cell of the present invention, the first compound semiconductor thin film may be formed by combining the group Ib element, the group IIIb element, and the group VIb element with A: B: C (where 0.05 ≦ C).
A ≦ 0.2, 0.25 ≦ B ≦ 0.4, 0.45 ≦ C ≦
0.65), and the second compound semiconductor thin film contains the group Ib element, the group IIIb element, and the group VIb element in a ratio of D: E: F (where 0.05 ≦ D ≦ 0. 2,
0.25 ≦ E ≦ 0.4, 0.45 ≦ F ≦ 0.65). Thereby, a solar cell having high characteristics can be obtained.

In the above solar cell of the present invention, the first compound semiconductor thin film is formed by combining the group Ib element, the group IIIb element and the group VIb element with A: B: C (provided that 0.15 ≦
A ≦ 0.35, 0.15 ≦ B ≦ 0.35, 0.4 ≦ C ≦
0.6), and the second compound semiconductor thin film contains the group Ib element, the group IIIb element, and the group VIb element in a ratio of D: E: F (where 0.05 ≦ D ≦ 0. 2,
0.25 ≦ E ≦ 0.4, 0.45 ≦ F ≦ 0.65). Thereby, a solar cell having high characteristics can be obtained.

In the above solar cell of the present invention, a third compound semiconductor thin film is provided between the first compound semiconductor thin film and the second compound semiconductor thin film, and the third compound semiconductor thin film is made of an Ib group. The element, the group IIIb element and the group VIb element are represented by G: H: I (provided that 0.05 ≦ G ≦ 0.2, 0.25
≦ H ≦ 0.4, 0.45 ≦ I ≦ 0.65). Thereby, a solar cell having high characteristics can be obtained.

The method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell including an upper electrode film and a lower electrode film, wherein after forming the lower electrode film, an Ib group element and IIIb
A first step of forming a first compound semiconductor thin film containing a group III element and a group VIb element,
a second step of forming a second compound semiconductor thin film containing a group b element and containing sulfur at a higher composition ratio than that of the first compound semiconductor thin film; and forming a compound thin film on the second compound semiconductor thin film. And a third step of forming. According to the above manufacturing method, the solar cell of the present invention can be easily manufactured.

In the above method, the compound thin film may be made of Z
nO, ZnS, ZnSe, Zn (O, OH), Zn
(O, OH, S), Zn (O, Se), Zn (O, O
H, Se) and Zn _x Mg _Y O (provided that 0 <X <1,
It is preferable that it is composed of at least one compound selected from 0 <Y <1).

In the above manufacturing method, the group Ib element contained in the first and second compound semiconductor thin films is Cu, and the group IIIb element contained in the first and second compound semiconductor thin films is In and It is preferably at least one element selected from Ga.

In the above manufacturing method, the group VIb element contained in the first compound semiconductor thin film is preferably Se, and the group VIb element contained in the second compound semiconductor thin film is preferably sulfur.

In the above-mentioned manufacturing method, it is preferable that in the second step, the second compound semiconductor thin film is formed by including a part of the first compound semiconductor thin film with sulfur.

In the above manufacturing method, in the second step, the step of including sulfur in a part of the first compound semiconductor thin film is performed by bringing the first compound semiconductor thin film into contact with a solution containing sulfur. It is preferably performed.
As a result, VIb contained in the first compound semiconductor thin film
Since part of the group III element is replaced by sulfur, a second compound semiconductor thin film containing sulfur at a higher composition ratio than the first compound semiconductor thin film can be easily formed.

In the above method, the solution may further contain a group IIIb element. As a result, a second compound semiconductor thin film containing a group IIIb element different from the first compound semiconductor thin film, or a second compound semiconductor thin film containing a group IIIb element at a different composition ratio from the first compound semiconductor thin film is formed. can get.

In the above production method, the pH of the solution is adjusted to
It is preferably 1.5 or more and 2.5 or less. Thereby, the second compound semiconductor thin film can be formed efficiently.

In the above manufacturing method, the second step may further include a step of forming a second compound semiconductor thin film and then including at least a group II element in the second compound semiconductor thin film. Thereby, the second compound semiconductor thin film containing the group II element can be easily formed.

In the above manufacturing method, in the second step, the step of including the group II element in the second compound semiconductor thin film includes the step of: disposing the second compound semiconductor thin film in an aqueous solution containing the group II element. It is preferably performed by contact. Thus, the second compound semiconductor layer can easily contain a group II element.

In the above production method, the pH of the aqueous solution is adjusted to
It is preferably 10 or more and 14 or less. Thereby, the second compound semiconductor layer can particularly easily contain a group II element.

In the above-mentioned production method, the aqueous solution is preferably
It is preferable to include at least one compound selected from halides, acetates, nitrates, and sulfates of group III elements as solutes. As a result, ions of the group II element are generated in the aqueous solution, and easily formed on the second compound semiconductor thin film.
Group II elements can be included.

In the above-mentioned manufacturing method, it is preferable that the method further includes a step of heat-treating the second compound semiconductor thin film after the second step and before the third step. Thereby, the crystallinity of the compound semiconductor thin film can be improved.

In the above-mentioned manufacturing method, the heat treatment is performed with nitrogen,
It is preferably performed in a gas atmosphere composed of at least one gas selected from hydrogen sulfide, argon and sulfur, or in a vacuum. This can prevent impurities from being mixed into the compound semiconductor thin film during the heat treatment.

In the above manufacturing method, the temperature of the heat treatment is 1
The temperature is preferably from 00 ° C to 600 ° C. By setting the temperature of the heat treatment to 100 ° C. or higher, the crystallinity of the compound semiconductor thin film can be effectively improved. Further, by setting the temperature of the heat treatment to 600 ° C. or less,
Deformation of the substrate can be prevented.

In the above manufacturing method, in the second step, the step of including the group II element in the second compound semiconductor thin film includes the step of forming the thin film including the group II element on the second compound semiconductor thin film. After the formation, the heat treatment may be performed by thermally diffusing the group II element.

In the above-described manufacturing method, in the second step, the second compound semiconductor thin film is formed of a group Ib element and a group III element.
It may be formed by simultaneously depositing a group b element and a group VIb element on the first compound semiconductor thin film.

In the above-mentioned manufacturing method, the first compound semiconductor thin film is formed of the group Ib element, the group IIIb element and the VI
A: B: C (provided that 0.15 ≦ A ≦ 0.
35, 0.15 ≦ B ≦ 0.35, 0.4 ≦ C ≦ 0.6)
Wherein the second compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by D:
E: F (however, 0.15 ≦ D ≦ 0.35, 0.15 ≦
E ≦ 0.35, 0.4 ≦ F ≦ 0.6).

In the above-described manufacturing method, the first compound semiconductor thin film may be formed by forming the group Ib element, the group IIIb element, and the VI
A: B: C (where 0.05 ≦ A ≦ 0.
2, 0.25 ≦ B ≦ 0.4, 0.45 ≦ C ≦ 0.65)
Wherein the second compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by D:
E: F (However, 0.05 ≦ D ≦ 0.2, 0.05 ≦ E
≦ 0.2, 0.45 ≦ F ≦ 0.65).

In the above-mentioned manufacturing method, the first compound semiconductor thin film is formed of the group Ib element, the group IIIb element and the VI
A: B: C (where 0.05 ≦ A ≦ 0.
2, 0.25 ≦ B ≦ 0.4, 0.45 ≦ C ≦ 0.65)
Wherein the second compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by D:
E: F (however, 0.15 ≦ D ≦ 0.35, 0.15 ≦
E ≦ 0.35, 0.4 ≦ F ≦ 0.6).

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 In Embodiment 1, an example of the solar cell of the present invention will be described.

FIG. 1 is a cross-sectional view of the solar cell 10 according to the first embodiment.

Referring to FIG. 1, solar cell 1 of Embodiment 1
Reference numeral 0 denotes a substrate 11, and a lower electrode film 12, a compound semiconductor thin film 13 (first compound semiconductor thin film), a compound semiconductor thin film 14 (second compound semiconductor thin film), and a compound thin film ( Hereinafter, referred to as a buffer layer) 15,
It includes a window layer 16 and an upper electrode film 17, and extraction electrodes 18 and 19 formed on the lower electrode film 12 and the upper electrode film 17.

As the substrate 11, for example, a glass substrate, a stainless steel substrate, a resin substrate, or the like can be used.

As the lower electrode film 12, for example, a metal thin film made of Mo or the like can be used. Upper electrode film 17
Is an electrode on the light incident side, for example, ITO (Ind
A transparent conductive film such as ium tin oxide (Im Tin Oxide) can be used.

The compound semiconductor thin film 13 is a semiconductor thin film functioning as a light absorbing layer and has a thickness of, for example, 0.5.
μm to 2.5 μm. The compound semiconductor thin film 13 is made of I
Includes Group b, Group IIIb and Group VIb elements. In the compound semiconductor thin film 13, for example, Cu can be used as the group Ib element, and at least one element selected from, for example, In and Ga can be used as the group IIIb element. In the compound semiconductor thin film 13, the group VIb element contains at least Se, and further contains sulfur as necessary. The compound semiconductor thin film 13 includes, for example, CuInSe ₂ , CuIn ₃ Se ₅ , Cu (In,
Ga) Se ₂ or Cu (In, Ga) ₃ Se ₅ , or a compound semiconductor in which part of Se is replaced with sulfur can be used.

The compound semiconductor thin film 14 is made of an Ib group element, II
Compound semiconductor thin film containing group Ib element and group VIb element
Contains sulfur in a composition ratio higher than 13. Compound semiconductor thin film
14 is, for example, 0.05 μm to 0.1 μm.
is there. In the compound semiconductor thin film 14,
For example, Cu can be used, and
Is at least one selected from In and Ga, for example.
One element can be used. Also compound semiconductor thin film
14, the group VIb element comprises at least sulfur,
Se is further contained as necessary. Compound semiconductor thin film 13
For example, CuInS_Two, CuIn_ThreeS_Five, Cu
(In, Ga) S_TwoOr Cu (In, Ga) _ThreeS_Five,Ah
Or a semiconducting compound in which some of these sulfurs are replaced by Se
The body can be used.

The compound semiconductor thin film 14 further comprises
The compound semiconductor thin film 14 containing a group II element may be referred to as a compound semiconductor thin film 14a. At this time, as the group II element, for example, Mg, Ca, Zn
And at least one element selected from Cd. When the compound semiconductor thin film 14 contains a group II element, an n-type compound semiconductor thin film is obtained, and a pn junction with few defects at the interface with the p-type compound semiconductor thin film 13 is obtained. Therefore, the compound semiconductor thin film 14
By including the group III element, a solar cell having high characteristics can be obtained. When the compound semiconductor thin film 14 contains a group II element, the compound semiconductor thin film 13 also
The fourth surface layer may contain a group II element.

The buffer layer 15 is made of a compound semiconductor. The buffer layer 15 includes, for example, ZnO, ZnS,
ZnSe, Zn (O, OH), Zn (O, OH, S),
Zn (O, Se), Zn (O, OH, Se) and Zn
_X Mg _Y O (however, a thin film made of at least one selected from 0 <X <1, 0 <Y <1) can be used. Here, Zn (O, OH) refers to a Zn—O bond and Z
a compound containing an n-OH bond; Zn (O, O
H, S), Zn (O, Se), Zn (O, OH, Se)
The same applies to.

For the window layer 16, for example, a ZnO film can be used.

For the extraction electrodes 18 and 19, for example, a metal thin film obtained by laminating a NiCr film and an Au film can be used.

As the compound semiconductor thin film 13 and the compound semiconductor thin film 14, those having various compositions can be used.

For example, when the compound semiconductor thin film 13 is made of Ib
Group element, group IIIb element, and group VIb element as A: B: C (provided that 0.15 ≦ A ≦ 0.35, 0.15 ≦ B ≦ 0.3
5, 0.4 ≦ C ≦ 0.6), and the compound semiconductor thin film 14 includes a group Ib element, a group IIIb element, and a group VIb element in D: E: F (where 0.15 ≦ D ≦ 0.35, 0.
15 ≦ E ≦ 0.35, 0.4 ≦ F ≦ 0.6). For example, if the compound semiconductor thin film 13 is C
uInSe ₂ and the compound semiconductor thin film 14 is made of CuIn
This corresponds to the case of S ₂ or the case where a part of In is substituted with Ga.

The compound semiconductor thin film 13 is composed of the group Ib element, the group IIIb element and the group VIb element A: B: C (provided that 0.05 ≦ A ≦ 0.2, 0.25 ≦ B ≦ 0. 4,
0.45 ≦ C ≦ 0.65), and the compound semiconductor thin film 14 contains a group Ib element, a group IIIb element, and a group VIb element in D: E: F (where 0.05 ≦ D ≦ 0. 2, 0.2
5 ≦ E ≦ 0.4, 0.45 ≦ F ≦ 0.65). For example, if the compound semiconductor thin film 13 is C
uIn ₃ Se ₅ and the compound semiconductor thin film 14 is CuIn
_This corresponds to the case of ₃ S ₅ or the case where Ga is partially substituted for In.

Further, the compound semiconductor thin film 13 includes the group Ib element, the group IIIb element and the group VIb element as A: B: C (provided that 0.15 ≦ A ≦ 0.35, 0.15 ≦ B ≦ 0. 3
5, 0.4 ≦ C ≦ 0.6), and the compound semiconductor thin film 14 includes a group Ib element, a group IIIb element, and a group VIb element in D: E: F (where 0.05 ≦ D ≦ 0.2, 0.2
5 ≦ E ≦ 0.4, 0.45 ≦ F ≦ 0.65). For example, if the compound semiconductor thin film 13 is C
uInSe ₂ and the compound semiconductor thin film 14 is made of CuIn ₃
If it is S _5, or corresponds If some of these In was replaced by Ga.

The compound semiconductor thin film 21 (third compound semiconductor thin film) may be further provided between the compound semiconductor thin film 13 and the compound semiconductor thin film 14. FIG. 2 is a cross-sectional view of the solar cell 20 in this case. The compound semiconductor thin film 21 is composed of a group Ib element, a group IIIb element and a group VIb element G: H: I (provided that 0.05 ≦ G ≦ 0.2, 0.2
5 ≦ H ≦ 0.4, 0.45 ≦ I ≦ 0.65). For example, as the compound semiconductor thin film 21, CuIn ₃ Se ₅ or a part of
Those substituted with a can be used.

In the solar cell of the first embodiment, the compound semiconductor thin film 13 is made of Cu (In, Ga) Se ₂ , and the compound semiconductor thin film 14 is made of Cu containing a group II element.
FIG. 3 shows the band structure when (In, Ga) S ₂ is used.
Is shown schematically in FIG. The compound semiconductor thin films 13 and 1
4, when the compound semiconductor thin film having the other composition described above is used, the band structure is similar to the band structure shown in FIG.

[0056] In FIG. 3, shows the energy difference between the bottom and the Fermi level of the conduction band of the compound semiconductor thin film 13 (the difference between the work function and electron affinity) in E _1, bottom and Fermi of the conduction band of the compound semiconductor thin film 14 showing the energy difference between the level E _2. As shown in FIG. 3, in the solar cell of Embodiment 1,
Compound semiconductor thin film 14, E ₂ is greater than E _1.
Further, the compound semiconductor thin film 14 is
When the compound semiconductor thin film 14 contains sulfur at a composition ratio larger than that of the compound semiconductor thin film 1,
3 is larger than the band gap. Therefore, according to the solar cell of the first embodiment, a solar cell having high voltage characteristics can be obtained.

Embodiment 2 In Embodiment 2, an example of a method for manufacturing the solar cell 10 described in Embodiment 1 will be described. In addition, about the same part as Embodiment 1, the overlapping description is abbreviate | omitted.

In the manufacturing method according to the second embodiment, first, FIG.
As shown in (a), a lower electrode film 12 is formed on a substrate 11. The lower electrode film 12 can be formed by, for example, an evaporation method or a sputtering method.

Thereafter, as shown in FIG. 4B, compound semiconductor thin films 13 and 14 are formed on the lower electrode film 12. A method for forming the compound semiconductor thin films 13 and 14 will be described later. When the solar cell 20 shown in FIG. 2 is formed, the compound semiconductor thin film 21 is formed between the compound semiconductor thin film 13 and the compound semiconductor thin film 14.

Thereafter, as shown in FIG. 4C, a buffer layer 15, a window layer 16, and an upper electrode film 17 are formed on the compound semiconductor thin film 14. The buffer layer 15 can be formed by, for example, a chemical deposition method, an evaporation method, a sputtering method, or the like. The window layer 16 and the upper electrode film 17 can be formed by, for example, an evaporation method or a sputtering method.

Thereafter, as shown in FIG. 4D, portions of the compound semiconductor thin films 13 and 14, the buffer layer 15, the window layer 16, and the upper electrode film 17 where the extraction electrode 18 is to be formed are removed. And 19 are formed.
For removing the compound semiconductor thin film 13 and the like, for example, a scribe method such as a laser scribe method, an etching method, or the like can be used. Also, the extraction electrodes 18 and 1
9 can be formed by an evaporation method or a sputtering method.

Thus, the solar cell described in Embodiment 1 can be formed.

Next, a method of forming the compound semiconductor thin films 13 and 14 will be described with reference to FIG.

In the manufacturing method according to the second embodiment, first, FIG.
As shown in (a), a compound semiconductor thin film 41 containing a group Ib element, a group IIIb element and Se is formed on the lower electrode film 12.
(First compound semiconductor thin film) is formed. The compound semiconductor thin film 41 can be formed by an evaporation method, a sputtering method, a chemical deposition method, or the like.

After that, as shown in FIG. 5B, a part of the compound semiconductor thin film 41 contains sulfur,
Compound semiconductor thin films 13 and 14 are formed.

In order to make part of the compound semiconductor thin film 41 contain sulfur, as shown in FIG.
1 may be brought into contact with the compound semiconductor thin film 41. By bringing the compound semiconductor thin film 41 into contact with the solution 51 containing sulfur, Se in the compound semiconductor thin film 41 is partially replaced by sulfur, and the compound semiconductor thin film 14 having a high sulfur composition ratio is formed. The part of the compound semiconductor thin film 41 where Se was not substituted is the compound semiconductor thin film 13.
Becomes

As the solution 51, for example, an aqueous solution containing thioacetamide, indium chloride, hydrochloric acid and the like can be used. The pH of the solution 51 is preferably 1.5 or more and 2.5 or less. The temperature of the solution 51 is 10 ° C. or more and 90 ° C.
C. or less is preferred. As a method of bringing the compound semiconductor thin film 41 into contact with the solution 51, for example, the substrate on which the compound semiconductor thin film 41 is formed may be immersed in the solution 51.

In the above first method, the solution 51
It may further contain a group Ib element. Thereby, the compound semiconductor thin film 14 containing a group IIIb element different from the compound semiconductor thin film 13 or the compound semiconductor thin film 1 containing a group IIIb element at a composition ratio different from that of the compound semiconductor thin film 13
4 is obtained. In this case, a solution containing sulfur,
Needless to say, a solution containing a Group IIIb element may be prepared and treated with each solution.

Next, the compound semiconductor thin film 1 containing a group II element
An example will be described in the case of forming 4a.

A first method for forming the compound semiconductor thin film 14a containing a group II element is as follows.
After forming 4, the compound semiconductor thin film 14 is brought into contact with an aqueous solution containing a group II element. This gives II
The group element is taken into the compound semiconductor thin film 14 to form the compound semiconductor thin film 14a. Also, depending on the processing conditions and the thickness of the compound semiconductor thin film 14, the compound semiconductor thin film 1
Group III elements are also taken into the surface layer on the compound semiconductor thin film 14 side among the three.

The aqueous solution containing a group II element includes, for example, II
An aqueous solution containing, as a solute, at least one compound selected from halides, acetates, nitrates, and sulfates of group III elements is exemplified. Group II elements include, for example, Mg, C
At least one element selected from a, Zn and Cd can be used.

The aqueous solution containing a group II element preferably has a pH of 10 or more and 14 or less. The aqueous solution containing a group II element preferably contains ammonia.

The compound semiconductor thin films 13 and 14 may be heat-treated after the treatment with the sulfur-containing solution or the aqueous solution containing the group II element. Heat treatment is nitrogen,
It is preferably performed in a gas atmosphere composed of at least one gas selected from hydrogen sulfide, argon and sulfur, or in a vacuum. Heat treatment is 100 ° C or more and 600 ° C
It is preferred to be performed at the following temperature.

A second method of forming the compound semiconductor thin film 14a containing a group II element is as follows.
After forming 4, a thin film containing a group II element is formed on the compound semiconductor thin film 14, and the group II element is thermally diffused. The thermal diffusion can be performed, for example, by performing a heat treatment at 250 ° C. for one hour. Depending on the thickness of the compound semiconductor thin film 14 and the conditions of the heat treatment, the surface layer of the compound semiconductor thin film 13 on the side of the compound semiconductor thin film 14 may also be II.
Group elements are incorporated.

In the manufacturing method according to the second embodiment, when the solar cell 20 described with reference to FIG.
After forming the compound semiconductor thin film 13 on the compound semiconductor thin film 13, a compound semiconductor thin film containing a group Ib element, a group IIIb element and a group VIb element (which can be formed in the same manner as the compound semiconductor thin film 41) is formed on the compound semiconductor thin film 13. The compound semiconductor thin film 21 and the compound semiconductor thin film 14 are formed by treating the compound semiconductor thin film with a solution containing sulfur in the same manner as described above.
May be formed.

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

(Embodiment 3) In Embodiment 3, another example of the method of manufacturing the solar cell of Embodiment 1 will be described. The manufacturing method according to the third embodiment is different from the manufacturing method according to the second embodiment only in the manufacturing method of the compound semiconductor thin films 13 and 14, and thus the overlapping description is omitted.

In the manufacturing method according to the third embodiment, first, FIG.
As shown in (a), a lower electrode film 12 is formed on a substrate 11.

Thereafter, as shown in FIG. 6B, a compound semiconductor thin film 13 is formed on the lower electrode film 12. The compound semiconductor thin film 13 can be formed by, for example, an evaporation method, a sputtering method, or a chemical deposition method.

After that, as shown in FIG. 6C, a compound semiconductor thin film 14 is formed on the compound semiconductor thin film 13.
The compound semiconductor thin film 14 is made of a group Ib element, a group IIIb element and a V
A group Ib element is formed by simultaneously depositing on the compound semiconductor thin film 13 under the condition that the composition ratio of sulfur is higher than that of the compound semiconductor thin film 13. The compound semiconductor thin film 14 can be formed by a vapor deposition method, a sputtering method, or a chemical deposition method.

The compound semiconductor thin film 1 containing a group II element
In the case of forming 4a, a group II element of the compound semiconductor thin film 14 may be contained by the method described in the second embodiment.

Thereafter, as shown in FIG. 6D, the buffer layer 15, the window layer 16, the upper electrode film 17, and the extraction electrode 1
8 and 19 are formed.

In this way, the solar cell 10 described in the first embodiment can be manufactured. When manufacturing the solar cell 20 described in the first embodiment, the compound semiconductor thin film 14 may include a group II element by the same method as that described in the second embodiment.

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

[0085]

The present invention will be described below more specifically with reference to examples.

Example 1 In Example 1, a CuInSe ₂ thin film as a compound semiconductor thin film 13 and a CuInS ₂ thin film as a compound semiconductor thin film 14 were formed, and then CuInS ₂ was added to a solution containing a compound containing Cd. By contacting the thin films, the compound semiconductor thin films 13 and 14a
An example in which is formed will be described.

First, a Mo film was formed on a glass substrate by a sputtering method. Thereafter, a CuInSe ₂ thin film (thickness: 2 μm) was formed on the Mo film by an evaporation method.

Next, a solution containing indium chloride (InCl ₃ ), which is a compound (salt) containing In, thioacetamide, and hydrochloric acid was prepared. The concentration of indium chloride in the solution was 0.005M, and the concentration of thioacetamide was 0.1M. The pH of the solution was 1.9. The container containing the solution was left standing in a warm water bath maintained at 75 ° C. A substrate on which a CuInSe ₂ thin film is formed in this solution,
Soaked for about 10 seconds. Thereafter, the substrate was taken out of the solution and washed with pure water.

Next, a solution containing cadmium sulfate (CdSO ₄ ), which is a compound (salt) containing cadmium, and ammonia was prepared. The concentration of cadmium sulfate in the solution was 0.001M, and the concentration of ammonia was 1M. The container containing the solution was left standing in a warm water bath maintained at 85 ° C. The substrate on which the compound thin film was formed was immersed in this solution for about 6 minutes. Thereafter, the substrate was taken out of the solution and washed with pure water.

The cross section of the semiconductor thin film treated as described above was observed with a transmission electron microscope. As a result, it was found that films having different compositions and a thickness of 4 nm to 5 nm were formed on the surface of the semiconductor thin film. As a result of composition analysis, this film was found to be CuInS ₂ . It was also found that Cd was present from the surface to a depth of about 50 nm.

In this embodiment, the case where a CuInSe ₂ thin film is used has been described. However, similar results were obtained with Cu (In, Ga) Se _{2 in} which part of In of CuInSe ₂ was replaced with Ga. As for the metal to be doped, the case where Cd was used was described, but similar results were obtained when Zn or Mg was used.

(Example 2) In Example 2, a CuInSe ₂ thin film as the compound semiconductor thin film 13, a CuIn ₃ Se ₅ thin film as the compound semiconductor thin film 21, and a CuIn ₃ S ₅ thin film as the compound semiconductor thin film 14 were formed. An example will be described in which a compound semiconductor thin film 14a is formed by contacting a CuIn ₃ S ₅ thin film with a solution containing a compound containing Cd.

First, a Mo film is formed on a glass substrate by a sputtering method, and CuInS
the formation of the e ₂ thin film. Further, CuI
A CuIn ₃ Se ₅ thin film was formed on the nSe ₂ thin film. At this time, the composition was controlled by changing the temperature of the cell containing In or Se to change the deposition amount. further,
A CuIn ₃ S ₅ thin film was formed on the CuIn ₃ Se ₅ thin film in the same manner as in Example 1. Finally, in the same manner as in Example 1, Cd was contained in the CuIn ₃ S ₅ thin film.

The cross section of the semiconductor thin film treated as described above was observed with a transmission electron microscope. As a result, it was found that films having different compositions and a thickness of 4 nm to 5 nm were formed on the surface of the semiconductor thin film. As a result of composition analysis, this film was found to be CuIn ₃ S ₅ . It was also found that Cd was present from the surface to a depth of about 50 nm.

In this embodiment, the CuInSe ₂ thin film and C
The case where a uIn ₃ S ₅ thin film is used has been described.
Some of nSe ₂ of In was replaced by Ga Cu (In,
Similar results were obtained when Ga) Se ₂ and Cu (In, Ga) ₃ S ₅ thin films were used. As for the metal to be doped, the case where Cd was used was described, but similar results were obtained when Zn or Mg was used.

(Embodiment 3) In this embodiment, a CuInSe ₂ thin film as the compound semiconductor thin film 13, a CuIn ₃ Se ₅ thin film as the compound semiconductor thin film 21, and a CuIn ₃ S ₅ thin film as the compound semiconductor thin film 14 are formed. An example of forming a semiconductor thin film in which a CuIn ₃ S ₅ thin film contains Cd by contacting a CuIn ₃ S ₅ thin film with a solution containing a compound containing Cd will be described.

First, a Mo film is formed on a glass substrate by a sputtering method, and CuInS
It was formed e ₂ film (thickness 2 [mu] m). Further, a CuIn ₃ Se ₅ thin film (thickness: 10 nm) was formed on the thin film by a vapor deposition method. Further, C is deposited on the CuIn ₃ Se ₅ thin film by a vapor deposition method.
A uIn ₃ S ₅ thin film (thickness: 5 nm) was formed. Next, Cd was contained in the CuIn ₃ S ₅ thin film in the same manner as in Example 1.

Analysis by Auger electron spectroscopy revealed that Cd was present at a depth of about 50 nm from the surface.

In this embodiment, the CuInSe ₂ thin film and C
The case where a uIn ₃ S ₅ thin film is used has been described.
Some of nSe ₂ of In was replaced by Ga Cu (In,
Similar results were obtained when Ga) Se ₂ and Cu (In, Ga) ₃ S ₅ thin films were used. As for the metal to be doped, the case where Cd was used was described, but similar results were obtained when Zn or Mg was used.

(Embodiment 4) In Embodiment 4, an example in which a solar cell is manufactured using the thin film formed by the method described in Embodiment 1 will be described.

An Mo film is formed on a glass substrate by a sputtering method, and Cu (In, Ga) Se ₂ is formed on the Mo film.
A film (1.8 μm in thickness) was formed by an evaporation method.

Thereafter, Cu (I
On the surface of the (n, Ga) Se ₂ thin film, Cu (In, Ga) S ₂
A thin film was formed. First, InCl ₃ (concentration 0.005)
M) and thioacetamide (concentration: 0.1 M) as a solute, and a solution prepared by adjusting the pH to 1.95 with HCl was prepared. The container containing the solution was left standing in a thermostat kept at 75 ° C. The glass substrate on which the Cu (In, Ga) Se ₂ film was formed was immersed in the above solution for a certain period of time, then pulled up and washed with pure water. The temperature of the solution when the substrate was taken out was about 70 ° C. After the treatment with the solution, a heat treatment was further performed. The heat treatment was performed by holding at 250 ° C. for 30 minutes in a nitrogen atmosphere.

Thereafter, a solution containing CdSO ₄ as a solute was prepared. The container containing the solution was allowed to stand in a thermostat maintained at 85 ° C. After the above substrate was immersed in the above solution, it was pulled up and washed with pure water. The temperature of the solution when the substrate was taken out was about 80 ° C.

Thereafter, a Zn (O, OH, S) film (thickness: 30 nm) as the buffer layer 15 was formed by a chemical deposition method. To form a Zn (O, OH, S) film,
Zinc acetate (Zn (CH ₃ COO) ₂ ) and thiourea (NH
₂ CSNH ₂ ) and ammonium acetate (CH ₃ COON)
A solution in which H ₄ ) and aqueous ammonia were mixed was prepared.
The concentrations were such that zinc acetate was 0.02M, thiourea was 0.3M, ammonium acetate was 0.1M, and ammonia was 0.5M.

The container containing the solution was allowed to stand in a warm water bath maintained at 85 ° C. After immersing the substrate in this solution for about 20 minutes, it was pulled up and washed with pure water. Thus, a Zn (O, OH, S) film was formed.

Further, a ZnO film (100 nm thick) as the window layer 16 and an ITO film (100 nm thick) as the upper electrode film 17 were formed on the Zn (O, OH, S) film by a sputtering method. The ZnO film was formed under the conditions of an argon gas pressure of 2 × 10 ⁻² Torr and a high frequency power of 400 W, and the ITO film was formed under an argon gas pressure of 8 × 10 ⁻³ Torr.
It was formed under the condition of a high frequency power of 400 W. Then, Ni
The extraction electrodes 18 and 19 were formed by laminating a Cr film and an Au film by an electron beam evaporation method. On the other hand, as a comparative example, a solar cell in which formation of a Cu (In, Ga) S ₂ film and treatment with a solution containing Cd were not performed was also manufactured.

The solar cell fabricated in this manner was provided with AM
The solar cell characteristics were measured by irradiating 1.5 or 100 mW / cm ² pseudo sunlight.

As a result of evaluating the characteristics of the solar cell manufactured by the above-described method, it was found that the short-circuit current of the solar cell of the present invention in which formation of the Cu (In, Ga) S ₂ film and treatment with the solution containing Cd were performed was 34 8.8 mA / cm ² , open circuit voltage 0.63 V, fill factor 0.66, conversion efficiency 14.5
%Met. On the other hand, in a solar cell in which the formation of the Cu (In, Ga) S ₂ film and the treatment with the solution containing Cd were not performed, the short-circuit current was 33.0 mA / cm ² , the open-circuit voltage was 0.54 V, and the fill factor was 0.1. 55, conversion efficiency is 9.8%
Met.

In the solar cell of Example 4, a film having a large energy difference between the bottom of the conduction band and the Fermi level is formed between the light absorbing layer and the buffer layer. Since the band matching was improved, a solar cell having high characteristics was obtained.

(Embodiment 5) In Embodiment 5, an example of manufacturing a solar cell using the compound semiconductor thin film formed by the method described in Embodiment 2 will be described.

A Mo film is formed on a glass substrate, and a Cu (In, Ga) Se ₂ thin film,
It was formed by laminating (In, Ga) ₃ Se ₅ thin films. Further, Cu (In, Ga) _{3 is formed} by the method described in the second embodiment.
By treating the Se ₅ thin film with a solution containing In and sulfur , the surface of the Cu (In, Ga) ₃ Se ₅ thin film has C
A u (In, Ga) ₃ S ₅ thin film was formed. Further, as in Example 2, Cu (In,
By processing the Ga) ₃ S ₅ thin film, Cu (In,
Was contained Cd in Ga) ₃ S ₅ film.

Thereafter, a buffer layer, a window layer, and an extraction electrode were formed in the same manner as in Example 4. When the characteristics of the solar cell manufactured in this manner were evaluated, solar cell characteristics equivalent to those of the solar cell of the present invention described in Example 4 were obtained.

(Embodiment 6) In Embodiment 6, an example in which a solar cell is manufactured using the thin film formed by the method described in Embodiment 3 will be described.

An Mo film is formed on a glass substrate, and a Cu (In, Ga) Se ₂ thin film and a C
u (In, Ga) ₃ Se ₅ thin film and Cu (In, Ga)
₃ S ₅ thin films were sequentially laminated. Further, the Cu (In, Ga) ₃ S ₅ film was treated with a solution containing Cd, so that the Cu (In, Ga) ₃ S ₅ film contained Cd.

Thereafter, a buffer layer, a window layer and an extraction electrode were formed in the same manner as in Example 4. When the characteristics of the solar cell manufactured in this manner were evaluated, solar cell characteristics equivalent to those of the solar cell of the present invention described in Example 4 were obtained.

The embodiments of the present invention have been described with reference to the examples. However, 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.

[0117]

As described above, in the solar cell of the present invention, the energy difference between the bottom of the conduction band and the Fermi level is between the compound semiconductor thin film serving as the light absorbing layer and the compound thin film (buffer layer). A large film is formed. Therefore, according to the solar cell of the present invention, a solar cell having good voltage characteristics can be obtained.

According to the method for manufacturing a solar cell of the present invention, the solar cell of the present invention can be easily manufactured.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing another example of the solar cell of the present invention.

FIG. 3 is a schematic view showing an example of a band structure of the solar cell of the present invention.

FIG. 4 is a process chart showing an example of a method for manufacturing a solar cell of the present invention.

FIG. 5 is a view showing a manufacturing process in a method for manufacturing a solar cell of the present invention.

FIG. 6 is a process chart showing another example of the method for manufacturing a solar cell of the present invention.

FIG. 7 is a cross-sectional view illustrating an example of a conventional solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10, 20 Solar cell 11 Substrate 12 Lower electrode film 13, 14, 14a, 41 Compound semiconductor thin film 15 Compound thin film (buffer layer) 16 Window layer 17 Upper electrode film 18, 19 Extraction electrode 51 Solution

Continued on the front page (72) Inventor Shigeo Hayashi 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. ) 5F051 AA07 AA09 AA10 CB11 CB24 CB29 CB30

Claims (30)

[Claims] 1. A solar cell comprising an upper electrode film and a lower electrode film, wherein the first compound semiconductor thin film is disposed between the upper electrode film and the lower electrode film sequentially from the lower electrode film side. , Second
Wherein the first compound semiconductor thin film comprises a group Ib element, a group IIIb element and a group VIb element, and wherein the second compound semiconductor thin film comprises a group Ib element and a group IIIb element And a group VIb element, and sulfur at a higher composition ratio than the first compound semiconductor thin film. 2. The method according to claim 1, wherein the compound thin film is composed of ZnO, ZnS, Z
nSe, Zn (O, OH), Zn (O, OH, S), Z
n (O, Se), Zn (O, OH, Se) and Zn _X
Mg _Y O (provided that, 0 <X <1,0 <Y <1) Solar cell according to claim 1 comprising at least one compound selected from the. 3. The Ib group element contained in the first and second compound semiconductor thin films is Cu, and the IIIb group element contained in the first and second compound semiconductor thin films is composed of In and Ga. The solar cell according to claim 1, which is at least one selected element. 4. The solar cell according to claim 3, wherein the group VIb element contained in the first compound semiconductor thin film is Se, and the group VIb element contained in the second compound semiconductor thin film is sulfur. . 5. The method according to claim 1, wherein the second compound semiconductor thin film further comprises:
The solar cell according to any one of claims 1 to 4, comprising a Group II element. 6. The solar cell according to claim 5, wherein the group II element is at least one element selected from Mg, Ca, Zn, and Cd. 7. The method according to claim 1, wherein the first compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by A:
B: C (however, 0.15 ≦ A ≦ 0.35, 0.15 ≦
B ≦ 0.35, 0.4 ≦ C ≦ 0.6), wherein the second compound semiconductor thin film comprises
D: E: F (provided that 0.15 ≦ D ≦ 0.35, 0.15 ≦ E ≦ 0.3
The solar cell according to any one of claims 1 to 6, wherein the ratio is in the range of 5, 0.4 ≦ F ≦ 0.6). 8. The method according to claim 1, wherein the first compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by A:
B: C (however, 0.05 ≦ A ≦ 0.2, 0.25 ≦ B
≦ 0.4, 0.45 ≦ C ≦ 0.65), wherein the second compound semiconductor thin film comprises
D: E: F (where 0.05 ≦ D ≦ 0.2, 0.25 ≦ E ≦ 0.4, and D: E: F)
The solar cell according to any one of claims 1 to 6, wherein the ratio is 0.45 ≦ F ≦ 0.65). 9. The semiconductor device according to claim 1, wherein the first compound semiconductor thin film is
The group b element, the group IIIb element and the group VIb element are represented by A:
B: C (however, 0.15 ≦ A ≦ 0.35, 0.15 ≦
B ≦ 0.35, 0.4 ≦ C ≦ 0.6), wherein the second compound semiconductor thin film comprises
D: E: F (where 0.05 ≦ D ≦ 0.2, 0.25 ≦ E ≦ 0.4, and D: E: F)
The solar cell according to any one of claims 1 to 6, wherein the ratio is 0.45 ≦ F ≦ 0.65). 10. A thin film transistor comprising a third compound semiconductor thin film between the first compound semiconductor thin film and the second compound semiconductor thin film, wherein the third compound semiconductor thin film includes a group Ib element and a group IIIb element. Group VIb element is represented by G: H: I (where 0.05 ≦
G ≦ 0.2, 0.25 ≦ H ≦ 0.4, 0.45 ≦ I ≦
The solar cell according to claim 9, which is contained at a ratio of 0.65). 11. A method for manufacturing a solar cell comprising an upper electrode film and a lower electrode film, wherein after forming the lower electrode film, the first method includes a group Ib element, a group IIIb element, and a group VIb element. A first step of forming a compound semiconductor thin film; and forming a second compound semiconductor thin film containing a group Ib element, a group IIIb element, and a group VIb element and containing sulfur at a higher composition ratio than the first compound semiconductor thin film. A second step of forming a compound thin film on the second compound semiconductor thin film. 12. The method according to claim 12, wherein the compound thin film is formed of ZnO, ZnS,
ZnSe, Zn (O, OH), Zn (O, OH, S),
Zn (O, Se), Zn (O, OH, Se) and Zn
_X Mg _Y O (provided that, 0 <X <1,0 <Y <1) producing a solar cell according to claim 11 comprising at least one compound selected from the. 13. The Ib group element contained in the first and second compound semiconductor thin films is Cu, and the IIIb group element contained in the first and second compound semiconductor thin films is selected from In and Ga. The method for producing a solar cell according to claim 11, wherein the solar cell is at least one element. 14. The group VIb element contained in the first compound semiconductor thin film is Se, and the group VIb element contained in the second compound semiconductor thin film is sulfur.
4. The method for manufacturing a solar cell according to 3. 15. The method according to claim 11, wherein in the second step, the second compound semiconductor thin film is formed by including sulfur in a part of the first compound semiconductor thin film.
15. The method for manufacturing a solar cell according to any one of items 14 to 14. 16. The method according to claim 16, wherein in the second step, the step of including sulfur in a part of the first compound semiconductor thin film is performed by bringing the first compound semiconductor thin film into contact with a solution containing sulfur. Item 16. A method for manufacturing a solar cell according to Item 15. 17. The method according to claim 16, wherein the solution further contains a group IIIb element. 18. The pH of the solution is 1.5 or more and 2.5 or more.
The method for manufacturing a solar cell according to claim 16, which is as follows. 19. The method according to claim 11, wherein the second step further includes, after forming the second compound semiconductor thin film, a step of including a group II element in the second compound semiconductor thin film. 3. The method for manufacturing a solar cell according to 1. 20. In the second step, the step of including the group II element in the second compound semiconductor thin film includes contacting the second compound semiconductor thin film in an aqueous solution containing the group II element. The method for manufacturing a solar cell according to claim 19, which is performed by: 21. The method according to claim 20, wherein the pH of the aqueous solution is 10 or more and 14 or less. 22. The method for manufacturing a solar cell according to claim 20, wherein the aqueous solution contains at least one compound selected from a halide, an acetate, a nitrate, and a sulfate of the Group II element as a solute. 23. The method of manufacturing a solar cell according to claim 15, further comprising, after the second step and before the third step, a step of heat-treating the second compound semiconductor thin film. Method. 24. The heat treatment is performed in a gas atmosphere consisting of at least one gas selected from nitrogen, hydrogen sulfide, argon and sulfur, or in a vacuum.
3. The method for manufacturing a solar cell according to 1. 25. The temperature of the heat treatment is not lower than 100 ° C. and not lower than 60 ° C.
The method for manufacturing a solar cell according to claim 23, wherein the temperature is 0 ° C or lower. 26. In the second step, the step of including the group II element in the second compound semiconductor thin film is performed after forming the thin film including the group II element on the second compound semiconductor thin film. 20. The method for manufacturing a solar cell according to claim 19, wherein the method is performed by thermally diffusing the group II element. 27. In the second step, the second compound semiconductor thin film comprises a group Ib element, a group IIIb element and a group VIb
The method for manufacturing a solar cell according to any one of claims 11 to 14, wherein the solar cell is formed by simultaneously depositing a group III element on the first compound semiconductor thin film. 28. The first compound semiconductor thin film, wherein the group Ib element, the group IIIb element, and the group VIb element are A: B: C (provided that 0.15 ≦ A ≦ 0.35; 1
5 ≦ B ≦ 0.35, 0.4 ≦ C ≦ 0.6), wherein the second compound semiconductor thin film comprises the Ib group element and the
D: E: F (provided that 0.15 ≦ D ≦ 0.35, 0.15 ≦ E ≦ 0.3
The method for producing a solar cell according to claim 11, wherein the ratio is included in a ratio of 5, 0.4 ≦ F ≦ 0.6). 29. The first compound semiconductor thin film according to claim 1, wherein said group Ib element, said group IIIb element, and said group VIb element are A: B: C (where 0.05 ≦ A ≦ 0.2, 0.1. 25
≦ B ≦ 0.4, 0.45 ≦ C ≦ 0.65), wherein the second compound semiconductor thin film comprises
D: E: F (provided that 0.05 ≦ D ≦ 0.2, 0.05 ≦ E ≦ 0.2, and D: E: F)
The method for producing a solar cell according to any one of claims 11 to 14, wherein the ratio is included in a ratio of 0.45 ≦ F ≦ 0.65). 30. The first compound semiconductor thin film, wherein the group Ib element, the group IIIb element, and the group VIb element are A: B: C (where 0.05 ≦ A ≦ 0.2, 0. 25
≦ B ≦ 0.4, 0.45 ≦ C ≦ 0.65), wherein the second compound semiconductor thin film comprises
D: E: F (provided that 0.15 ≦ D ≦ 0.35, 0.15 ≦ E ≦ 0.3
The method for producing a solar cell according to claim 11, wherein the ratio is included in a ratio of 5, 0.4 ≦ F ≦ 0.6).