JP2002222966A - Photoelectric converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a photoelectric converter using crystal semiconductor grains has a low reliability. SOLUTION: The photoelectric converter comprises many crystal semiconductor grains 5 arranged on a board 2 having one electrode layer 3, an insulating substance 4 filled among the grains 5, and another electrode 6 connected to upper part sides of the grains 5. In the converter, the one layer 3 is formed of an alloy of aluminum and silicon to prevent occurrence of excess melt of the grains 2 at a connecting time, and a strength of the board 2 can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectric conversion device using crystalline semiconductor particles used for photovoltaic power generation.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional photoelectric conversion device using crystalline semiconductor particles. As shown in FIG. 3, in US Pat. No. 4,514,580, an aluminum film 12 is formed on the surface of a steel substrate 11, and the aluminum film 12 is formed.
There is disclosed a photoelectric conversion device in which a pulverized silicon particle 13 is bonded to an insulating layer 3, an n-type silicon portion 14, and a transparent conductive layer 15 are sequentially formed.

Further, as shown in FIG.
Japanese Patent No. 24179 discloses that an opening is formed in a first aluminum foil 25, and a silicon sphere having an n-type skin portion 27 on a p-type silicon portion 26 is joined to the opening, and an n-type skin on the back side of the sphere 26 is formed. The part 27 is removed and the oxide layer 2
8 is disclosed, in which the oxide layer 28 on the surface in contact with the p-type silicon portion 26 on the back side of the sphere is removed, and is bonded to the second aluminum foil 29.

[0004]

However, in the conventional photoelectric conversion device shown in FIG. 3, since the aluminum film 12 is formed only on the surface of the steel substrate 11 as the substrate, the aluminum film 12 is easily oxidized. Further, when bonding the aluminum film 12 and the crushed silicon particles 13,
There is a problem that the pulverized silicon particles 13 are excessively melted, and in some cases, the pulverized silicon particles 13 are completely melted.

In order to solve this problem, it is necessary to increase the thickness of the aluminum film 12, and if the aluminum film 12 is made thicker, there arises a problem that the particle size of the ground silicon particles 13 to be bonded must also be increased.

That is, as described in US Pat. No. 4,514,580, a silicon particle size of 300 to 1000 μm is limited to an aluminum film thickness of 100 to 500 μm. It was difficult to make the film thinner.

[0007] Further, as shown in FIG.
In the photoelectric conversion element disclosed in Japanese Patent Application Publication No.
When the silicon sphere having the shaped skin portion 27 is bonded to the second aluminum foil 29, when the bonding temperature becomes 577 ° C. or higher, which is the eutectic temperature of aluminum and silicon, the aluminum 29 serving as the substrate is melted and the silicon sphere 26 is melted. However, there is a problem that the pierce through the second aluminum foil 29.

The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide a low-cost photoelectric conversion device which suppresses an excessive reaction between a substrate material and crystalline semiconductor particles. Is to do.

[0009]

According to a first aspect of the present invention, there is provided a photoelectric conversion device comprising: a substrate having one electrode layer; In a photoelectric conversion device in which an insulating material is filled therebetween and the other electrode is connected to the upper side of the crystalline semiconductor particles, the one electrode layer is made of an alloy of aluminum and silicon.

Further, in the photoelectric conversion device according to claim 1, the silicon content in the one electrode layer is 1.5 to 1.5.
It is characterized by being 30 wt%.

In a photoelectric conversion device using crystalline semiconductor particles, by providing aluminum having a low melting point and a high electric conductivity at the junction between the substrate and the crystalline semiconductor particles, a low-temperature bonding and a low-resistance electrode can be realized. However, the use of aluminum alone causes a problem because the crystalline semiconductor particles are excessively melted during bonding. Therefore, in the present invention, the problem of melting of the crystalline semiconductor particles at the time of joining can be solved by using an alloy composed of aluminum and silicon.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. In FIG. 1, 2 is a substrate, and 3 is one electrode layer.

The substrate 2 is made of a metal having a melting point higher than that of aluminum.
Any ceramic may be used, for example, aluminum, aluminum alloy, iron, stainless steel, nickel, alumina, and the like.

One electrode layer 3 is made of an alloy of aluminum and silicon. By using the alloy of aluminum and silicon, it is possible to prevent the crystal semiconductor particles 5 from being excessively melted when the one electrode layer 3 and the crystal semiconductor particles 5 are joined. This is particularly effective when the particle size of the crystal semiconductor particles 5 is reduced to 0.2 to 0.6 mm in order to reduce the amount of silicon used as the crystal semiconductor particles 5.

The amount of silicon to be contained in one electrode layer 3 is preferably about 1.5 to 30 wt%.
If it is less than 1.5 wt%, it is not enough to prevent excessive melting, and if it exceeds 30 wt%, the aluminum alloy becomes brittle and the strength is sharply reduced. is there. Further, even if one or more elements selected from magnesium, manganese, chromium, titanium, nickel, zinc, silver, and copper are added as the second additive element, the prevention of excessive melting can be maintained.

The thickness of one electrode layer 3 is 20 μm or more. If the thickness is less than 20 μm, a sufficient thickness cannot be obtained due to insufficient film thickness when bonding with the crystalline semiconductor particles.

When formed on the photoelectric conversion element, one electrode layer 3 made of an alloy of aluminum and silicon is used.
In this case, an additional alloy layer of silicon and aluminum is formed by diffusion of silicon from the crystalline semiconductor particles.

An insulator 4 is provided on one electrode layer 3 made of an alloy of aluminum and silicon. The insulator 4 is made of an insulating material for separating the positive electrode and the negative electrode. For example, SiO ₂ , Al ₂ O ₃ , PbO, B ₂ O ₃ , Z
There is an insulator using a glass slurry containing nO or the like as an optional component. When the insulator 4 is formed on the substrate 1, it needs to have a certain degree of hardness or viscosity, and it is necessary to temporarily hold the pushed semiconductor particles 5. And the substrate 1
It has a property of melting at a heating temperature at the time of forming an ohmic junction between the semiconductor particles 5 and partially covering the semiconductor particles 5.

On the aluminum alloy layer 3, a large number of crystalline semiconductor particles 5 of the first conductivity type are provided. The crystalline semiconductor particles 5 are made of B, Al, Ga, or the like exhibiting p-type in Si, or n.
P, As, etc., which have a shape, contain trace elements. Examples of the shape of the crystalline semiconductor particles 5 include those having a polygonal shape, those having a curved surface, and the like. For example, when the semiconductor particles 5 are pushed from above the insulator layer 4 and brought into contact with the substrate 1,
In order to efficiently push the insulator layer 4, it is preferable that the insulator layer 4 has a curved surface, especially a spherical shape. The particle size distribution may be uniform or non-uniform, but if uniform, a process for adjusting the particle size is required. When the semiconductor particles 5 are pushed from above the insulator layer 5 and brought into contact with the substrate 1, even if the semiconductor particles 5 are not uniform, the jig for pushing the crystalline semiconductor particles 5 is made of a flexible material so that the substrate can be sufficiently covered. 1 can be contacted. Further, by having a convex curved surface, the dependence on the light ray angle of light is small.

The crystal semiconductor particles 5 have a particle size of 0.2
0.8 mm is preferable, and when it exceeds 0.8 mm, the amount of silicon used in the conventional crystal plate type photoelectric conversion element including the cut portion is not changed, and the merit of using the crystalline semiconductor particles is lost. If it is smaller than 0.2 mm, another problem that it becomes difficult to assemble the substrate 1 occurs. More preferably, 0.2-
0.6 mm is preferred.

On the insulating layer 4 and the crystal semiconductor particles 5, a second conductivity type crystal semiconductor layer 6 also serving as a surface electrode is provided. The crystalline semiconductor layer 6 is formed by, for example, introducing a small amount of an n-type phosphorus-based compound vapor phase or a p-type boron-based compound vapor phase into a silane compound vapor phase by a vapor phase growth method or the like. Note that the crystalline semiconductor layer 6 only needs to include single crystal, polycrystal, or microcrystal. Also,
Since the crystalline semiconductor layer 6 also has the role of an electrode, it is not necessary to separately provide a transparent conductive film, so that the process is simplified and the cost can be reduced. Furthermore, if a transparent conductive film is formed as an electrode at a defective portion when the crystalline semiconductor layer 6 is formed, the semiconductor particles 5 located below the defective portion of the crystalline semiconductor layer 6 and the transparent conductive film leak. Occurs.

The concentration of trace elements in the layer is determined due to the conductivity.
The degree may be high, for example 1 × 10 ¹⁶-10^{twenty one}atm /
cm^ThreeIt is about.

A protective film 7 is provided on the crystal semiconductor layer 6 of the second conductivity type. The protective film 7 preferably has the property of a transparent dielectric, for example, silicon oxide, CVD, PVD or the like.
Cesium oxide, aluminum oxide, silicon nitride, titanium oxide, SiO ₂ —TiO ₂ , tantalum oxide, yttrium oxide, or the like is formed on the crystalline semiconductor layer 6 in a single layer or in a single layer or in combination. The protective film 7 needs to be transparent because it is in contact with the light incident surface, and needs to be a dielectric material to prevent leakage from the above problem.
If the thickness of the protective film 7 is optimized, a function as an anti-reflection film can be expected.

In order to reduce the series resistance, it is possible to improve the conversion efficiency by providing pattern electrodes such as fingers and bus bars at regular intervals on the crystal semiconductor layer 6 or the protective film 7.

[0025]

Next, specific examples of the photoelectric conversion device of the present invention will be described. [Example 1] A substrate in which aluminum alloys having different silicon contents shown in Table 1 were formed on a stainless steel substrate by cold compression bonding at a thickness of 50 µm, and a glass paste was used as an insulator layer, and a glass paste was used to form 100 µm on the substrate. It was applied to a thickness. The glass used for the glass paste had a softening temperature of about 400 ° C. 0.2-0.6mm diameter on it
The p-type silicon particles were placed, pressed and brought into contact with various aluminum alloys, and heated at a temperature of 577 ° C. for 5 to 10 minutes to bond the silicon particles to the aluminum alloy. Then, an n-type crystalline silicon layer was formed to a thickness of 400 nm on the silicon particles and the insulator layer, and silicon nitride was formed as a protective film.

Table 1 summarizes the appearance and photoelectric conversion efficiency results of the five samples prepared as described above.

[0027]

[Table 1]

In Comparative Examples 1 to 3, the silicon particles were completely melted in two out of five sheets. From this fact, it is considered that reliability is low when the silicon content in the aluminum alloy is less than 1.5% in consideration of manufacturing variations. In Comparative Example 4, the aluminum alloy was brittle, and the aluminum alloy could not be formed on the stainless steel substrate when forming the substrate.

On the other hand, in Examples 1 to 5, there was no problem in the formation of the substrate and the molten state of the silicon particles, and good photoelectric conversion elements were obtained. It is considered that when the content of silicon in the aluminum alloy is in the range of about 1.5 to 30%, excessive melting of silicon particles can be prevented and the initial strength of the substrate can be maintained. Thus, it was confirmed that the photoelectric conversion element of the present invention was a photoelectric conversion element that could maintain high reliability.

[0030]

As described above, according to the photoelectric conversion device of the present invention, a large number of crystal semiconductor particles are provided on a substrate having one electrode layer, and an insulating material is filled between the crystal semiconductor particles. In a photoelectric conversion device in which the other electrode is connected to the upper side of the crystal semiconductor particles, the one electrode layer is formed of an alloy of aluminum and silicon to prevent excessive melting of the crystal semiconductor particles. In addition, a photoelectric conversion device that can maintain the strength as a substrate can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a photoelectric conversion element of the present invention.

FIG. 2 is a sectional view showing another embodiment of the photoelectric conversion element of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a photoelectric conversion element of Conventional Example 1.

FIG. 4 is a cross-sectional view illustrating an example of a photoelectric conversion element of Conventional Example 2.

[Explanation of symbols]

 2 ... substrate 3 ... one electrode layer 4 ... insulator layer 5 ... first conductivity type crystalline semiconductor particles 6 ... second conductivity type semiconductor layer (the other Electrode layer) 7 ... Protective layer

Continuation of the front page (72) Inventor Hisao Arimune 6F, 1166, Haseno, Snake-cho, Yokaichi-shi, Shiga Prefecture F-term in the Shiga Yokaichi Plant (reference) 5F051 AA03 AA20 DA03 DA20 FA06 FA15 GA02 GA03

Claims (2)

[Claims] A large number of crystal semiconductor particles are provided on a substrate having one electrode layer, an insulating material is filled between the crystal semiconductor particles, and the other electrode is connected to the upper side of the crystal semiconductor particles. The photoelectric conversion device, wherein the one electrode layer is made of an alloy of aluminum and silicon. 2. The photoelectric conversion device according to claim 1, wherein the content of silicon contained in the one electrode layer is 1.5 to 30 wt%.