JPH11312817A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a substrate from warping due to thermal stress when a thin film is formed even if a low melting material such as SLG containing much Na is used in order to improve the crystal growth in a thin light-absorbing layer by evaporation caused by diffusion of Na. SOLUTION: A solar cell wherein a CIS (a compound of element selected from among Cu, In and Se) or CIGS-based (a compound of element selected from among Cu, In, Ca and Se) thin film is formed as a light-absorbing layer 3 on a substrate 1 via a metal electrode layer 2. The substrate 1 is a coupled body of a first substrate 11 containing Na and a second substrate 12 made of a high melting material. The thin light absorbing layer 3 is formed on the first substrate 11 via the electrode layer 2 by evaporation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell using a semiconductor thin film, and more particularly to a substrate structure thereof.

[0002]

2. Description of the Related Art Conventionally, a CIS type (Cu, In,
In a solar cell in which a thin film of (Se compound) is formed, by using soda lime glass SLG containing a large amount of sodium Na for the substrate, the Na component of the substrate is reduced when the CIS thin film is formed by vapor deposition. Diffusion promotes crystal growth, thereby forming a CIS film with good energy conversion efficiency.
0-74966).

[0003]

The problem to be solved is that when a CIS thin film is formed on a SLG substrate via a Mo electrode layer by vapor deposition, a high substrate temperature (550 ° C. or higher) required for film formation is required. The SLG substrate is softened, and the difference in the thermal expansion coefficient between the SLG substrate and the Mo electrode layer formed on the SLG substrate (Mo has a lower thermal expansion coefficient) causes the SLG substrate to be softened.
That is, the substrate warps together with the Mo electrode layer.

FIG. 3 shows an SLG substrate 1 'on which an electrode layer 2 made of Mo is formed.

FIG. 4 shows a state in which the entire light-absorbing layer 3 is warped when it is formed on the electrode layer 2 by vapor deposition.

The warpage of the substrate not only has an adverse effect such as causing distortion in the crystal growth of CIS, but also makes it difficult to form a module. This tendency becomes more conspicuous as the size of the substrate increases, which hinders a future increase in area.

[0007]

According to the present invention, a CIS (Cu, I) as a light absorbing layer is provided on a substrate via a metal electrode layer.
compound of an element selected from n, Se) or CIGS
In a solar cell in which a thin film of a system (a compound of an element selected from Cu, In, Ga, and Se) is formed, a soda-lime glass SL whose substrate contains a large amount of Na component is provided.
Even if a substrate made of a low melting point material such as G is used, the substrate is made of a Na-containing first substrate and a high melting point material so that the substrate does not warp and withstand high temperatures when forming a CIS or CIGS thin film. As a combination with the second substrate, the first substrate
The light absorbing layer is formed on the substrate through the electrode layer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG. 1, a substrate 1 of a solar cell is a combined body of a first substrate 11 containing Na and a second substrate 12 made of a high melting point material.

The first substrate 11 is made of a SiO 2 glass having a high Na content, for example, soda lime glass SL.
G is used. Further, as the second substrate 12, a glass material such as non-alkali glass, low alkali glass, quartz glass, and Pyrex glass can be used, and a metal, ceramic, or polymer material can be used.

The production of the substrate 1 composed of the first substrate 11 and the second substrate 12 includes, for example, the first substrate 11 and the second substrate 12.
Or the second substrate 12
The first substrate 11 is formed thereon by dip coating, vapor deposition, ion coating of SLG, CVD of a SiO 2 glass material having a high Na content, or spin-on glass.
Can be formed.

As shown in FIG. 2, an electrode layer 2 is formed on the first substrate 11 by sputtering using a metal material such as molybdenum (Mo).

A light absorbing layer 3 is provided on the electrode layer 2.
A CIS-based or CIGS-based thin film is formed by vapor deposition.

At this time, the high substrate temperature (55
0 ° C. or higher), and the first substrate 11 which is a low melting point material
Is softened, the second substrate 12 is made of a high melting point material, so that the substrate 1 does not warp due to thermal stress.

Further, when the film of the light absorbing layer is formed by vapor deposition, the Na component of the first substrate 11 diffuses to promote crystal growth, thereby forming the light absorbing film 3 having good energy conversion efficiency. Will be able to do that.

Even if the second substrate 12 is made of a material having a different thermal expansion coefficient from that of CIS or CIGS, the first substrate 11 as a low melting point material such as SLG having a thermal expansion coefficient relatively close to that of CIS or CIGS therebetween. Is interposed,
It is possible to effectively absorb the stress due to the difference in thermal expansion applied to the light absorbing layer 3 when forming the film.

[0016]

As described above, according to the present invention, a CIS or CIG as a light absorbing layer is formed on a substrate via a metal electrode layer.
In a solar cell in which an S-based thin film is formed, an electrode is formed on a first substrate containing Na and a second substrate made of a material having a high melting point. Since the thin film of the light absorbing layer is formed by vapor deposition through the layer, the substrate has a low melting point such as soda lime glass SLG having a high Na content so as to promote the crystal growth of the light absorbing layer by diffusion of the Na component. Even if a material is used, the substrate can be prevented from warping during the formation of the thin film.

[Brief description of the drawings]

FIG. 1 is a front sectional view illustrating a substrate of a solar cell according to an embodiment of the present invention.

FIG. 2 is a front sectional view showing a state in which a light absorbing layer is formed on a substrate via an electrode layer in the same example.

FIG. 3 is a front sectional view showing a state where an electrode layer is formed on an SLG substrate in a conventional solar cell.

FIG. 4 is a front sectional view showing a state in which warpage occurs when a light absorbing layer is formed on a conventional substrate via an electrode layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 11 1st substrate 12 2nd substrate 2 Electrode layer 3 Light absorption layer

Claims (2)

[Claims] 1. A solar cell in which a CIS or CIGS-based thin film as a light absorbing layer is formed on a substrate via an electrode layer, wherein the substrate comprises a sodium-containing first substrate and a high melting point material. A solar cell comprising a combination with a second substrate, wherein a light absorption layer is formed on the first substrate via an electrode layer. 2. The method according to claim 1, wherein the first substrate is made of SiO2 having a high Na content.
The solar cell according to claim 1, wherein the second substrate is made of a non-alkali glass, a low alkali glass, a metal, a ceramic, or a polymer material.