JPH0823110A - Manufacture of thin film solar cell - Google Patents

Abstract

PURPOSE:To provide a satisfactory junction a P-type semiconductor layer and an n-type semiconductor layer and improve the conversion efficiency, by forming the P-type semiconductor layer made of chalcopyrite-type compound, dipping the p-type semiconductor layer with an ammonia solution and forming the n-type semiconductor layer thereon. CONSTITUTION:A metal electrode layer 2 of molybdenum is formed on a glass substrate 1. A P-type chalcopyrite-type compound semiconductor layer 3 of CuInS2 or CuInSe2 and an n-type semiconductor layer 4 are sequentially formed on the metal electrode layer 2. Then, a transparent electrode layer 5 is provided on the n-type semiconductor layer 4. After the P-type chalcopyrite-type compound semiconductor layer 3 is formed and then dipped in an ammonia solution, the n-type semiconductor layer 4 is formed thereon. By thus dipping the P-type chalcopyrite-type compound semiconductor layer 3 in the ammonia solution, a needle crystal due to a different phase produced on the surface of the P-type chalcopyrite-type compound semiconductor layer 3 can be selectively removed by etching. Thus, the chalcopyrite-type compound semiconductor layer without having a different phase on the surface thereof can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film solar cell comprising a chalcopyrite type compound semiconductor layer.

[0002]

2. Description of the Related Art Chalcopyrite type compound semiconductors such as copper indium disulphide (CuInS ₂ ) and copper indium diselenide (CuInSe ₂ ) have been attracting attention as materials capable of achieving solar cells with high conversion efficiency. FIG. 1 is a cross-sectional view of a conventional thin film solar cell using a chalcopyrite type compound semiconductor. Thickness 0.5
A metal electrode layer 2 of molybdenum (Mo) or the like having a thickness of about 1 μm is formed on a glass substrate 1 having a thickness of about 1.5 mm. Metal electrode layer 2
A p-type chalcopyrite type compound semiconductor layer 3 of CuInS ₂ , CuInSe ₂ or the like having a thickness of 1 to 3 μm and a thickness of 5 to
100 nm cadmium sulfide (CdS), zinc oxide (Z
nO) and other n-type semiconductor layers 4 are sequentially formed.
Approximately 1 μm of indium-tin oxide (ITO) and aluminum-added zinc oxide (ZnO: A) on the type semiconductor layer 4.
The transparent electrode layer 5 such as 1) is provided.

There are various methods for forming a chalcopyrite type compound semiconductor thin film. For example, copper (Cu) or silver (Ag) is formed on the electrode layer 2 by a sputtering method.
Ib group metal layer such as Indium (In), gallium (G
a) a group IIIb metal layer such as a) is laminated, and the layer is applied with H ₂ S,
There is a known technique of performing annealing using a gas containing a chalcogen element such as H ₂ Se.

[0004]

However, when a chalcopyrite type compound semiconductor thin film is formed by the above method, for example, if it is a CuInS ₂ thin film, C is formed on the outermost surface.
Different phases such as uIn ₅ S ₈ , Cu ₂ S, In ₂ S ₃ are CuI
When the n-type semiconductor layer such as CdS is formed at the same time as nS _{2 is} formed thereon, there is a problem that causes deterioration of the junction characteristics.

An object of the present invention is to provide a method for producing a thin film solar cell, which is a solar cell comprising a chalcopyrite type compound semiconductor layer and which can solve the above-mentioned problems by a simple method and improve the junction characteristics. It is in.

[0006]

In such a situation,
As a result of diligent studies on a method of removing a heterogeneous phase on the surface of a chalcopyrite type compound semiconductor layer, the present inventors have found that, when the formed chalcopyrite type compound semiconductor layer is immersed in ammonia water, the heterogeneous phase can be selectively removed by etching. The present invention has been completed.

That is, the present invention is a method of manufacturing a thin film solar cell, which comprises depositing a p-type semiconductor layer made of a chalcopyrite type compound, immersing it in aqueous ammonia, and then laminating an n-type semiconductor layer. The cross-sectional view of the thin film solar cell of the present invention is the same as that of FIG. A metal electrode layer 2 of molybdenum (Mo) or the like having a thickness of about 1 μm is formed on a glass substrate 1 having a thickness of 0.5 to 1.5 mm. 1 ~ 3μ thickness on the metal electrode layer 2
m of p-type chalcopyrite type compound semiconductor layer 3 such as CuInS ₂ or CuInSe _{2 and} an n-type semiconductor layer 4 of 5 to 100 nm thick such as cadmium sulfide (CdS) and zinc oxide (ZnO) are formed in this order. A transparent electrode layer 5 of indium-tin oxide (ITO), aluminum-added zinc oxide (ZnO: Al) or the like having a thickness of about 1 μm is provided on the n-type semiconductor layer 4.

Chalcopyrite type compound in the present invention
Is a group Ib metal of the periodic table of elements such as Cu and Ag, Al,
Group IIIb metals and S, S of the periodic table of elements such as Ga and In
Chalcopyrite composed of e and Te chalcogen elements
It is a general term for compounds having a (chalcopyrite) type structure.
There are many types of chalcopyrite-type compounds.
Of these, CuInS₂, CuInSe₂, CuIn
Te₂, CuGaSe₂, CuGaTe₂, AgInS
₂, AgInSe₂, AgInTe₂, AgGaS
e₂, AgGaTe ₂Or their solid solutions are suitable
It has a wide band gap and is a material for thin-film solar cells.
Is preferred as More preferably CuInS₂, C
uInSe₂, CuGaSe₂Is mentioned.

The chalcopyrite type compound semiconductor layer is formed by a vacuum deposition method in which the chalcopyrite type compound itself is evaporated as an evaporation source, a sputtering method using the chalcopyrite type compound itself as a target, and a component element of the chalcopyrite type compound. Multi-source vacuum vapor deposition method in which each element is vapor-deposited separately, multi-sputtering method in which component elements of chalcopyrite type compound are separately used as targets, or laminated thin films of constituent metals such as Cu
Although not particularly limited, such as chalcogenization of the -In thin film, when a method of chalcogenizing a laminated thin film of constituent metals is used, a different phase is easily generated on the surface of the chalcopyrite compound semiconductor layer, and the effect of the present invention Appears more prominently.

In the present invention, the concentration and temperature of the ammonia water are not particularly limited, but the higher the concentration and the temperature, the higher the speed of removing the different phase by etching, but the volatilization of ammonia tends to become severe. Therefore, the concentration is preferably 0.01 to 50%, more preferably 0.1 to 30%. Moreover, about temperature, 5-80 degreeC is preferable, More preferably, it is 10-60.
° C.

Further, in the present invention, if the immersion time in the ammonia water is too short, the heterogeneous phase cannot be sufficiently removed by etching, and if it is too long, the effect does not change, so 0.1 to 50 hours is preferable. , More preferably 1
40 hours. In the present invention, the material of the n-type semiconductor layer is preferably one having a forbidden band width larger than that of a chalcopyrite type compound semiconductor which is a partner to form a junction, and examples thereof include CdS, ZnS, ZnSe and In ₂ S ₃ . Chalcogenide compound, ZnO, SnO ₂ , ZrO ₂
And the like.

The method for forming the n-type semiconductor layer is not particularly limited, such as the vapor deposition method, the sputtering method and the solution growth method. However, the solution growth method can form a good bond because it can form a film with good coverage at a low temperature. It is preferable to do so. A feature of the present invention is that a chalcopyrite type compound semiconductor thin film is brought into contact with aqueous ammonia, and for example, a CuInS ₂ thin film is CuIn
Good bonding characteristics with n-type semiconductor layer by selectively etching away different phases such as ₅ S ₈ , Cu ₂ S, In ₂ S ₃ and exposing a chalcopyrite compound semiconductor thin film without any different phases on the outermost surface. That is, a thin film solar cell can be manufactured.

[0013]

EXAMPLES Examples of the present invention will be specifically described below.

[0014]

Example 1 A thin film solar cell having a structure similar to that shown in FIG. 1 was prepared.
Was. First, a glass substrate 1 having a thickness of 1 mm has a thickness of 1 μm.
The Mo electrode layer 2 was formed by the sputtering method. next
By a sputtering method on a predetermined area on the Mo electrode layer
After stacking Cu thin film and In thin film (composition ratio Cu / In
= 0.95 Measured with JCXA-733 manufactured by JEOL Ltd.
)), 5 mol% H₂Ar gas containing S gas
Heat treatment at 550 ° C for 3 hours in an atmosphere to a thickness of 2 μm
CuInS ₂The thin film 3 was formed. After that, the temperature is 25 ℃
Was immersed in 25% aqueous ammonia for 20 hours.

Regarding the CuInS ₂ thin film before and after the immersion in ammonia water, an electron microscope (S-27 manufactured by Hitachi, Ltd.) was used.
00) Observation and X-ray diffraction spectrum (manufactured by Rigaku Corporation)
RU-200B) was measured. Before immersion in ammonia water, needle-like crystals due to a different phase were observed on the surface of the CuInS ₂ thin film, and the CuIn ₅ S ₈ phase was detected by X-ray diffraction, whereas after immersion, the needle-like crystals were mostly removed. Therefore, the X-ray diffraction spectrum has no peaks other than CuInS ₂ . In addition, the X-ray diffraction peak intensity and the half width of CuInS ₂ did not change before and after the immersion in ammonia water.

Next, CuInS after soaking in ammonia water
₂ Form a 50 nm n-type CdS layer 4 on the thin film by the solution growth method, and then form 0.5 μm by the sputtering method.
The ITO transparent electrode layer 5 was formed. As a result of measuring the current / voltage characteristics between ITO and Mo of the thin film solar cell element thus manufactured, good diode characteristics were confirmed. The current ratio at 4V in the forward / reverse direction was about 500. When this device was irradiated with light of AM 1.5, the conversion efficiency was 7.5%.

[0017]

Comparative Example 1 H₂CuInS heat treated in S gas₂Thin
Except not to immerse the membrane in ammonia water
In the same manner as in Example 1, p-type CuInS₂And n-type C
A thin film solar cell made of dS was produced. CuInS₂Thin
On the film surface, a different phase CuIn _FiveS₈There are needle crystals
In order to achieve
When measuring the pressure characteristics, the amount of current when a reverse bias is applied is large.
The current ratio at 4V in the forward / reverse direction is about 100
Met. In addition, AM1.5 was added to the manufactured solar cell element.
When irradiated with light, the conversion efficiency was 4.3%.

[0018]

According to the present invention, it is possible to form a chalcopyrite type compound semiconductor thin film having no foreign phase on the surface,
A thin-film solar cell manufactured using this thin film is useful because it has good junction characteristics with the n-type semiconductor layer and high conversion efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an element structure of a thin film solar cell according to the present invention and a conventional technique.

[Explanation of symbols]

 1. Glass substrate 2. Metal electrode layer 3. Chalcopyrite type compound semiconductor layer 4. n-type semiconductor layer 5. Transparent electrode layer

Claims (1)

[Claims] 1. A method for manufacturing a thin-film solar cell, comprising depositing a p-type semiconductor layer made of a chalcopyrite type compound, immersing the p-type semiconductor layer in ammonia water, and then stacking an n-type semiconductor layer.