JPH1140826A - Thin-film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound thin-film solar cell of high efficiency. SOLUTION: A thin-film solar cell 10 is possessed of a first layer 3 of p-type semiconductor formed of at least a compound selected from among compounds I-II-VI2 , 1-III3 -VI5 , ad I-III3 -VI8 of I, III, and VI elements in the periodic table, a second layer 4 of n-type semiconductor kept in contact with the first layer 3 and formed of at least a compound selected from among compounds III-VI, III2 -VI3 , and III6 -VI7 of III and VI elements in the periodic table, third layers 5 and 6 of n-type semiconductor kept in contact with the second layer 4 and formed of a compound II-VI of II and VI element in the periodic table, and a fourth layer 7 of n-type semicodutor formed as a transparent conductive film in contact with the third layers 5 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin-film solar cell made of a compound semiconductor.

[0002]

2. Description of the Related Art Conventionally, as a thin film solar cell formed by a heterojunction of a compound semiconductor, for example, CuInS
It is known to have a p-type semiconductor layer made of e ₂ , an n-type semiconductor layer made of CdS, and an n-type semiconductor layer made of ZnO having a substantially wide band gap with substantially conductivity.

FIG. 3 is an explanatory sectional view of a conventional thin film solar cell formed by a heterojunction of a compound semiconductor. The thin-film solar cell 20 is structurally supported on a substrate 11 made of glass and having a thickness of 1 to 3 mm. An electrode 12 made of a metal layer having a thickness of 1 to 2 μm, preferably a molybdenum (Mo) layer is applied on the substrate 11. As a light absorbing layer of a thin-film solar cell, a 1-2 μm thick II
The p-type semiconductor layer 13 made of II-VI ₂ , preferably, indium copper diselenide (CuInSe ₂ )
2 on which II-VI, preferably cadmium sulfide (Cd
An n-type semiconductor layer 15 made of S) is disposed on the p-type semiconductor layer 13.

[0004] On the n-type semiconductor layer 15, 0.01
An n-type semiconductor layer 16 made of II-VI, preferably zinc oxide (ZnO), having a thickness of about 0.5 μm is provided. Then, on the n-type semiconductor layer 16, 300 to 13
A n-type semiconductor material having a wide band gap substantially transparent in a visible range of a wavelength of 00 nm, preferably aluminum oxide-doped zinc oxide (ZnO: Al);
A transparent conductive film 17 having a thickness of 2 μm is provided.

[0005]

The compound-based thin-film solar cell having such a structure has a shorter life span of carriers generated by the photoelectric effect as compared with a conventional silicon-based solar cell, and thus has a potential. There is a problem that only a performance lower than the energy conversion capability can be obtained, and a highly efficient compound-based thin film solar cell cannot be provided.

An object of the present invention is to solve such a problem. That is, an object of the present invention is to provide a highly efficient compound-based thin film solar cell.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a thin-film solar cell, comprising compounds I-III-VI ₂ , I-III ₃ -VI ₅ and I-III-VI ₂ of compounds of groups I, III and VI of the periodic table. I-
A first layer formed of a p-type semiconductor made of at least one compound selected from the group consisting of III ₅ -VI ₈ , and contacting the first layer to form a compound III of a group III, VI compound of the periodic table -VI, III ₂ -VI ₃ and a second layer formed of n-type semiconductor composed of at least one compound selected from the III ₆ -VI _7, first of the periodic table in contact on the second layer II-VI of a compound of a group II, VI element
A third layer formed of a type semiconductor, and a fourth layer as a transparent conductive film formed of an n-type semiconductor in contact with the third layer.

According to a second aspect of the present invention, in the first aspect, the Group I element is Cu, the Group III element is at least one element selected from In and Ga, and the Group VI element is Se and S. I-III-VI ₂ , I-III ₃ -VI ₅ and II of compounds which are at least one element selected from
II ₅ at least one of a thin film formed by the p-type semiconductor composed of a compound selected from -VI ₈ is characterized by having a single layer or multiple layers.

[0009] The third invention is the first or second invention, wherein
I-III-VI ₂ is represented by the following formula: Cu (In _1-x Ga _x ) (S _1-y Se _y ) ₂ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ) Is characterized by having a single layer or multiple layers of a thin film formed of a p-type semiconductor of the compound represented by the formula (1).

[0010] The fourth invention is the first or second invention, wherein
I-III ₃ -VI ₅ is represented by the following formula: Cu (In _{1 -x} Ga _x ) ₃ (S _{1 -y} Se _y ) ₅ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ) Is characterized by having a single layer or multiple layers of a thin film formed of a p-type semiconductor of the compound represented by the formula (1).

According to a fifth aspect of the present invention, in the first or second aspect,
I-III ₅ -VI ₈ is represented by the following formula: Cu (In _{1 -x} Ga _x ) ₅ (S _{1 -y} Se _y ) ₈ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ) Is characterized by having a single layer or multiple layers of a thin film formed of a p-type semiconductor of the compound represented by the formula (1).

According to a sixth aspect of the present invention, in the first, second, third, fourth or fifth aspect, the group III element is at least one selected from In, Ga and Al, and the group VI element is O,
I which is at least one selected from S, Se and Te
It is characterized by having a single layer or multiple layers of a thin film formed of an n-type semiconductor comprising at least one compound selected from II-VI, III ₂ -VI ₃ and III ₆ -VI ₇ .

According to a seventh aspect of the present invention, in the first, second, third, fourth, fifth or sixth aspect the invention is directed to III-VI, III ₂ -VI ₃ and I-VI.
II ₆ -VI ₇ are represented by the following formulas (In _1-x Ga _x ) (Se _y S _1-y ), (In _1-x Ga _x ) ₂ (Se _y S _1-y ) ₃ and (In _{1- x} Ga _x ) ₆ (Se _y S _1-y ) ₇ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ) Is characterized by having a single layer or multiple layers of a thin film formed of an n-type semiconductor of the compound shown in (1).

The eighth invention is directed to the first, second, third, fourth, fifth and sixth aspects.
Or, in the invention, the compound II- in which the Group II element is at least one element selected from Cd and Zn, and the Group VI element is at least one element selected from O, S, Se and Te It is characterized by having a single layer or multiple layers of a thin film formed of an n-type semiconductor made of VI.

The ninth invention is directed to the first, second, third, fourth, fifth,
In the invention of 6, 7, or 8, the transparent conductive film is made of ITO, Sn
It is characterized by comprising a single layer or a multilayer of a thin film formed of an n-type semiconductor of at least one compound selected from O ₂ and ZnO doped with Al or B.

In the present specification, “ITO” means oxidized
Indium tin (In_TwoO_Three+ SnO _Two ).

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view of a thin-film solar cell of the present invention.

The thin-film solar cell 10 of the present invention has a thickness of 1 to 3 mm.
Is structurally supported by a substrate 1 having a thickness of The substrate 1 used in the present invention is preferably soda lime glass, but any substrate such as a resin, a ceramic substrate, or a metal conventionally used in the manufacture of a solar cell may be used as long as the object of the present invention is not violated. Can also be used.

On the substrate 1, an electrode 2 made of a metal layer, preferably a Mo layer, having a thickness of 1 to 2 μm is applied.

On this electrode 2, a thickness of 1 to 2 μm
I-III-VI_Two, I-III_Three-VI _Five And I-III_Five-
VI₈P comprising at least one compound selected from
The type semiconductor layer 3 is arranged. This compound, for example,
If the Group I element is made of Cu and the Group III element is In,
And at least one selected from Ga and
At least the Group VI element is selected from Se and S
Consists of one type. This compound is preferably CuInS
e_Two And CuInS_Two , And the following formula: Cu (In_1-xGa_x) (S_1-ySe_y)_Two , Cu (In_1-xGa_x)_Three(S_1-ySe_y)_Five And Cu (In_1-xGa_x)_Five(S_1-ySe_y)₈ (Where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ). this
The compound thin film can have a single layer or multiple layers.

On the p-type semiconductor layer 3, 0.01 to
An n-type semiconductor layer 4 having a thickness of 0.3 μm and made of at least one compound selected from III-VI, III ₂ -VI ₃ and III ₆ -VI ₇ is arranged. In this compound, for example, the Group III element is composed of at least one element selected from In, Ga and Al, and the Group VI element is composed of at least one element selected from O, S, Se and Te. This compound is, specifically, In ₂ S
e ₃ , InSe, In ₆ Se ₇ , Ga ₂ S ₃ , GaS, G
a ₂ Se ₃ , GaSe, AlS, In ₂ S ₃ , InS, In
Te, AlSe, Al ₂ S ₃ , In ₂ Te ₃ , Al ₂ Se
₃ , AlTe and Al ₂ Te ₃ , preferably In ₂
Se ₃ and Ga ₂ S _{3 and the} following formula: (In _1-x Ga _x ) (S _1-y S _y ), (In _1-x G _ax ) ₂ (S _1-y S _y ) ₃ and (In _1-x Ga _x ) ₆ (S _1-y Se _y ) ₇ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. ). The thin film of this compound can have a single layer or multiple layers.

On the n-type semiconductor layer 4, an n-type semiconductor layer 5 made of II-VI compound and having a thickness of 0.01 to 0.5 μm is arranged. In this compound, for example, the Group II element is composed of at least one selected from Cd and Zn, and the Group VI element is composed of at least one selected from O, S, Se and Te. This compound is, specifically,
CdS, CdZnS, ZnS, ZnSe, CdSe and ZnO, preferably CdS. On this n-type semiconductor layer 5, an n-type semiconductor layer 6 made of another II-VI compound and having a thickness of 0.01 to 0.5 μm can be arranged. This compound is, for example, ZnO, CdZn
S, ZnS, ZnSe, CdSe and CdS, and preferably ZnO.

Then, on the n-type semiconductor layer 6, 300
A wide bandgap n-type semiconductor material that is substantially transparent in the visible range of 1300 nm wavelength, such as aluminum-doped zinc oxide (ZnO: Al), boron-doped zinc oxide (ZnO: B), ITO and A conductive film 7 made of SnO ₂ , preferably made of ZnO: Al and ZnO: B and having a thickness of 0.1 to 2 μm is provided.

Each layer constituting the thin-film solar cell of the present invention comprises:
It can be formed by using a known thin film forming means such as a sputtering method, a vacuum evaporation method, and a solution growth method.

[0025]

【Example】

(Example 1) 2 on a 1.1 mm thick soda lime glass
A Mo layer having a thickness of μm was formed by a sputtering method. On this Mo layer, Cu, In and Se are ternary-simultaneously vacuum-deposited to form a deposited film, which is then selenized in a selenium atmosphere to form a 1 μm-thick p-type semiconductor layer of CuInSe _2. Formed. On this p-type semiconductor layer, an n-type semiconductor layer made of In ₂ Se _{3 having a} thickness of 0.1 μm was formed by a vacuum evaporation method. Next, an n-type semiconductor layer made of CdS having a thickness of 0.1 μm is formed on the n-type semiconductor by a CBD method, and an n-type semiconductor layer made of ZnO having a thickness of 0.05 μm is formed on the n-type semiconductor layer made of CdS by a sputtering method. A type semiconductor layer was formed, and a 1.0 μm thick Al-doped ZnO n-type semiconductor layer was formed as a transparent electrode film on the n-type semiconductor layer made of ZnO by a sputtering method. The conversion efficiency of the thin-film solar cell thus obtained was 10.6%.

In the present embodiment, the "conversion efficiency" was measured by irradiating a solar cell with light using an artificial light source (Solar simulater) and outputting the result. The measurement conditions were: light intensity; 100 mW / cm ₂ , air mass (AM);
5, and temperature; 25 ° C.

The “CBD method” refers to a solution containing Cd.
(CdI_Two, CdSO_Four , Cd (CH _ThreeCOO)_TwoEtc.
Make a mixed solution of urea and adjust it to alkaline
Then, immerse the sample in this mixed solution and stir the mixed solution.
CdS film on sample by heating to 50-80 ° C while
Is a known method.

Example 2 A 2 μm thick Mo layer was formed on a 1.1 mm thick soda lime glass by a sputtering method. Ga, In and Cu are sequentially vacuum-deposited on the Mo layer to form a deposited film, which is then selenized with H ₂ Se to form a 1 μm thick Cu (In _0.85 Ga
_0.25 ) A p-type semiconductor layer made of Se ₂ was formed. This p
0.2 μm thick In ₂ on the semiconductor layer by vacuum evaporation.
An n-type semiconductor layer made of Se ₃ was formed. Next, this n
A 0.3 μm thick n-type semiconductor layer made of CdS is formed on the n-type semiconductor layer by a CBD method, and a 0.1 μm-thick Zn layer is formed by a sputtering method on the n-type semiconductor layer made of the CdS.
An n-type semiconductor layer made of O is formed, and the ZnO
On an n-type semiconductor layer made of
An 8-μm thick n-type semiconductor layer made of ZnO doped with Al was formed as a transparent electrode film. The conversion efficiency of the thin-film solar cell thus obtained was 11.7%.

Example 3 A Mo layer having a thickness of 1.5 μm was formed on a 1.1 mm-thick soda lime glass by a sputtering method. Cu and In are simultaneously vacuum-deposited on the Mo layer to form a deposited film, which is then selenized with H ₂ Se to obtain a 1.5 μm thick CuInSe.
₂ was formed. On this p-type semiconductor layer, an n-type semiconductor layer made of Ga ₂ S _{3 having a} thickness of 0.2 μm was formed by a vacuum evaporation method. Next, C is formed on this n-type semiconductor.
An n-type semiconductor layer made of CdS having a thickness of 0.05 μm is formed by a BD method, and an n-type semiconductor layer made of ZnO having a thickness of 0.2 μm is formed on the n-type semiconductor layer made of CdS by a sputtering method.
Type semiconductor layer, and a 0.6 μm thick B layer is formed on the n-type semiconductor layer made of ZnO by sputtering.
An n-type semiconductor layer made of ZnO doped with is formed as a transparent electrode film. The conversion efficiency of the thin-film solar cell thus obtained was 6.1%.

(Conventional Example 1) A 2 μm thick Mo layer was formed on a 1.1 mm thick soda lime glass by a sputtering method. Cu, In, and Se are vacuum-deposited on the Mo layer at the same time in a ternary manner to form a deposited film, which is then selenized in a selenium atmosphere to form a 1 μm thick CuIn.
A p-type semiconductor layer made of Se ₂ was formed. Next, this n
A 0.1 μm thick CdS n-type semiconductor layer is formed on the n-type semiconductor by the CBD method, and a 0.05 μm-thick Zd layer is formed on the n-type semiconductor layer of the CdS by a sputtering method.
forming an n-type semiconductor layer made of nO;
An n-type semiconductor layer of ZnO doped with Al having a thickness of 1.0 μm was formed as a transparent electrode film on the n-type semiconductor layer of O by a sputtering method. The conversion efficiency of the thin-film solar cell thus obtained was 8.3%.

(Conventional Example 2) A 2 μm thick Mo layer was formed on a 1.1 mm thick soda lime glass by a sputtering method. Ga, In and Cu are sequentially vacuum-deposited on the Mo layer to form a deposited film, which is then selenized with H ₂ Se to form a 1 μm thick Cu (In _0.85 Ga
_0.25 ) A p-type semiconductor layer made of Se ₂ was formed. next,
A 0.3 μm thick Cd is formed on the n-type semiconductor by the CBD method.
An n-type semiconductor layer made of S is formed, an n-type semiconductor layer made of ZnO having a thickness of 0.1 μm is formed on the n-type semiconductor layer made of CdS by a sputtering method, and the n-type semiconductor layer made of ZnO is formed. An n-type semiconductor layer made of ZnO doped with Al and having a thickness of 0.8 μm was formed thereon as a transparent electrode film by a sputtering method. The conversion efficiency of the thin-film solar cell thus obtained was 10.2%.

(Conventional Example 3) A 1.5 μm thick Mo layer was formed on a 1.1 mm thick soda lime glass by a sputtering method. Cu and In are simultaneously vacuum-deposited on the Mo layer to form a deposited film, which is then selenized with H ₂ Se to obtain a 1.5 μm thick CuInSe.
₂ was formed. Next, a 0.05 μm thick CdS n-type semiconductor layer is formed on the n-type semiconductor by the CBD method, and a 0.2 μm thick ZnO layer is formed on the CdS n-type semiconductor layer by the sputtering method.
An n-type semiconductor layer made of ZnO is formed on the n-type semiconductor layer made of ZnO by sputtering.
An n-type semiconductor layer made of ZnO doped with B and having a thickness of μm was formed as a transparent electrode film. The conversion efficiency of the thin-film solar cell obtained in this manner was 4.3%.

The thin-film solar cells obtained according to Examples 1 to 3 have improved conversion efficiency as compared with the corresponding thin-film solar cells obtained according to Conventional Examples 1 to 3. I understand.

[0034] The thin-film solar cell of the present invention comprises III-VI,
By having an n-type semiconductor layer made of at least one compound selected from III ₂ -VI ₃ and III ₆ -VI ₇ , I-III-VI ₂ , I-III ₃ -VI ₅ and II
The band structure from the p-type semiconductor layer made of at least one compound selected from II ₅ -VI ₈ to the transparent conductive film (FIG. 2) becomes gentler than the band structure of the conventional thin film solar cell (FIG. 4). . For this reason, in the thin-film solar cell of the present invention, the same phenomenon occurs that electrons are accelerated by the built-in electric field in the graded layer of the graded bandgap solar cell and become hard to recombine, and the lifetime of carriers generated by the photoelectric effect occurs. It is thought that the energy conversion ability becomes long enough to bring out the potential energy conversion ability.

[0035]

The present invention relates to compounds III-VI, III ₂ -VI ₃ and III of compounds of elements of groups III and VI of the periodic table.
By having an n-type semiconductor layer composed of at least one compound selected from ₆ -VI _7, it is possible to provide a thin film solar cell of high efficiency compound systems.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a thin-film solar cell of the present invention.

FIG. 2 is an explanatory diagram of a band structure of the thin-film solar cell of the present invention.

FIG. 3 is an explanatory sectional view of a conventional thin-film solar cell.

FIG. 4 is an explanatory view of a band structure of a conventional thin film solar cell.

[Explanation of symbols]

1 substrate 2 electrode _{3 I-III-VI 2,} I-III 3 -VI 5 and III
P-type semiconductor layer 4 made of at least one compound selected from I ₅ -VI ₈ n-type semiconductor layer 5 made of at least one compound selected from III-VI, III ₂ -VI ₃ and III ₆ -VI ₇ N-type semiconductor layer made of II-VI compound 6 n-type semiconductor layer made of II-VI compound 7 transparent conductive film 10 thin film solar cell

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Kamiya 1500 Yasushi Sogyo Co., Ltd., Susono City, Shizuoka Prefecture (72) Inventor Norio Mochizuki 1500 Onjuku 1500, Susono City, Shizuoka Prefecture Yazaki Sogyo Co., Ltd. (72) Kazue Suzuki Inventor 1500 Yasushi Sogyo Co., Ltd., Susono City, Shizuoka Prefecture (72) Inventor Kenji Sato Inside the 1500 Yazaki Sogyo Co., Ltd., Susono City, Shizuoka Prefecture (72) The inventor Masami Nakamura 1500 Onjuku Yasushi Sogyo Co., Ltd. Inventor Shin-ichi Nakagawa 1500 Onizuku, Susono City, Shizuoka Prefecture Yazaki Corporation (72) Inventor Masaharu Ishida 1500 Onjuku 1500, Susono City, Shizuoka Prefecture Yazaki Corporation

Claims (9)

[Claims] 1. I-III-VI ₂ , I-III ₃ -VI ₅ and I-III compounds of the Group I, III and VI elements of the Periodic Table
A first layer formed of a p-type semiconductor made of at least one compound selected from the group consisting of III ₅ -VI ₈ , and contacting the first layer to form a compound III of a group III, VI compound of the periodic table -VI, III ₂ -VI ₃ and a second layer formed of n-type semiconductor composed of at least one compound selected from the III ₆ -VI _7, first of the periodic table in contact on the second layer II-VI of a compound of a group II, VI element
A thin-film solar cell comprising: a third layer formed of a type semiconductor; and a fourth layer as a transparent conductive film formed of an n-type semiconductor in contact with the third layer. 2. The group I element is Cu, the group III element is at least one element selected from In and Ga, and the group VI element is at least one element selected from Se and S. I-III-VI ₂ , II of certain compounds
2. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a single-layer or multiple-layer thin film formed of a p-type semiconductor made of at least one compound selected from II ₃ -VI ₅ and I-III ₅ -VI _8. battery. 3. I-III-VI ₂ is represented by the following formula: Cu (In _1-x Ga _x ) (S _1-y Se _y ) ₂ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. 3. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a single layer or multiple layers formed of a p-type semiconductor of the compound represented by the formula (1). 4. I-III ₃ -VI ₅ is represented by the following formula: Cu (In _{1 -x} Ga _x ) ₃ (S _{1 -y} Se _y ) ₅ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. 3. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a single layer or multiple layers formed of a p-type semiconductor of the compound represented by the formula (1). 5. I-III ₅ -VI ₈ is represented by the following formula: Cu (In _{1 -x} Ga _x ) ₅ (S _{1 -y} Se _y ) ₈ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. 3. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a single layer or multiple layers formed of a p-type semiconductor of the compound represented by the formula (1). 6. The group III-element wherein the group III element is at least one element selected from In, Ga and Al, and the group VI element is at least one element selected from O, S, Se and Te. VI, III ₂ -VI ₃ and III ₆ -V
At least one thin-film solar cell according to claim 1, 2, 3, 4 or 5, wherein the compound thin film formed in a more becomes n-type semiconductor and having a single layer or multiple layers selected from I _7. 7. III-VI, III ₂ -VI ₃ and III
_6- VI ₇ are represented by the following formulas (In _1-x Ga _x ) (Se _y S _1-y ), (In _1-x Ga _x ) ₂ (Se _y S _1-y ) ₃ and (In _1-x Ga _x ) ₆ (Se _y S _1-y ) ₇ (where x and y are respectively 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1
Is the value indicated by. 7. The thin-film solar cell according to claim 1, wherein the thin-film solar cell has a single layer or multiple layers formed of an n-type semiconductor of the compound represented by the formula (1). 8. The group II element is at least one element selected from Cd and Zn, and the group VI element is O,
4. A thin film formed of an n-type semiconductor comprising II-VI of a compound which is at least one element selected from S, Se and Te, having a single layer or a multilayer. 8. The thin-film solar cell according to 4, 5, 6, or 7. 9. The transparent conductive film is made of ITO, SnO ₂ and Al.
Or a single layer or multiple layers of a thin film formed of an n-type semiconductor of at least one compound selected from ZnO doped with B.
9. The thin-film solar cell according to 6, 7, or 8.