JP2758741B2 - Photoelectric conversion element and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion element using a crystalline semiconductor powder and a method for manufacturing the same, and enables the manufacture of an inexpensive photoelectric conversion element.

[0002]

2. Description of the Related Art Photovoltaic conversion elements such as solar cells, light receiving elements, and optical sensors include those using a single crystal substrate, those using a polycrystalline substrate, and those using an amorphous material. is there. That is, a device using a single crystal substrate has high performance but is expensive. Amorphous materials are lightweight, can be bent and are inexpensive, but have poor performance and have problems in reliability. The one using a polycrystalline substrate is in the middle of the above in both performance and price, but still not sufficiently low price.

On the other hand, in the case of a solar cell which is an example of a photoelectric conversion element, a solar cell using a powder of a single crystal semiconductor or a polycrystalline semiconductor is considered in order to realize a high performance and low cost solar cell. ing. In this method, a single crystal semiconductor powder or a polycrystalline semiconductor powder is densely arranged on a substrate on which a back electrode is formed, and a part of the semiconductor powder is doped with impurities to form a pn junction.

[0004]

In a conventional photoelectric conversion device using a single crystal substrate or a polycrystal substrate, a substrate having a thickness larger than a necessary thickness is used as an element, which causes unnecessary increase in cost. Had become. On the other hand, in the case of a photoelectric conversion element using a single crystal or polycrystalline semiconductor powder, unlike an element using a single crystal or polycrystalline substrate, the cost can be reduced without using wasteful materials.

However, a solar cell using crystalline semiconductor powder, which is an example of a conventional photoelectric conversion element, uses a high-temperature process by impurity diffusion for forming a junction, or takes out an electrode from the surface when actually forming the element. In addition, problems such as insulation between the front electrode and the back electrode have not been sufficiently solved.

[0006]

According to a first aspect of the present invention , there is provided a substrate and a substrate formed on the surface of the substrate.
Low melting point metal layer, fixed on the substrate by the low melting point metal layer
A first conductivity type crystalline semiconductor powder, and the first conductivity type
Formed on the exposed surface of the crystalline semiconductor powder and the low melting point metal layer
an i-type amorphous semiconductor layer and the i-type amorphous semiconductor layer;
Second conductivity type amorphous semiconductor formed on semiconductor layer
And a second conductive type amorphous semiconductor layer.
Photoelectric conversion element comprising a transparent conductive layer
I will provide a. Further, the second aspect is the above-mentioned i-type amorpha.
The thickness of the scan semiconductor layer to provide a photoelectric conversion element characterized several 100Å and to Rukoto.

[0007] Further, a third aspect of the present invention is to provide a low melting point metal on a substrate.
Forming a first semiconductor layer of a first conductivity type on the low melting point metal layer.
Body powder, and heat and melt the low melting point metal layer
Crystal semiconductor powder is fixed on the low melting point metal layer, and the crystal semiconductor powder is fixed.
I-type amorphous on the exposed surface of the body powder and the low melting point metal layer
After forming the semiconductor layer, the i-type amorphous semiconductor
Amorphous semiconductor layer of second conductivity type on body layer, transparent conductive
3. The method according to claim 1, wherein the layers are sequentially formed.
And a method for manufacturing the photoelectric conversion element.

[0008]

The photoelectric conversion element of the present invention basically comprises one crystalline semiconductor powder of the first conductivity type and an i-type amorphous semiconductor layer and an amorphous semiconductor layer of the second conductivity type formed thereon. Acting as one photoelectric conversion element, the carrier moves in the stacking direction. These basic elements are connected by electrodes so as to be in parallel or in series, and used as a large-area photoelectric conversion element.

In the manufacturing method of the present invention, first, a crystalline semiconductor powder of the first conductivity type (for example, n-type Si) is formed by the low melting point metal layer.
Are fixed, and the i-type amorphous semiconductor layer and the second conductive type amorphous semiconductor layer (for example, p-type amorphous Si
By this, the front electrode is prevented from directly contacting the substrate surface which is the back electrode. A back electrode connected to the crystalline semiconductor powder is formed on the substrate surface, or the substrate itself is a back electrode, and when forming a junction with the amorphous semiconductor layer, the back electrode is formed by a gap of the crystalline semiconductor powder. In order to prevent short-circuiting of the amorphous semiconductor layer, a junction between the i-type amorphous semiconductor layer and the second conductive type amorphous semiconductor layer (for example, a p-type amorphous Si layer) is provided. Then, according to the present manufacturing method, a large-area photoelectric conversion element in which the layer made of the crystalline semiconductor powder and the amorphous semiconductor layer are formed on the substrate in this order is formed.

[0010]

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

Embodiment 1 FIG. 1 is a diagram for explaining a manufacturing process of a solar cell element according to the present invention. First, a low-melting metal film 2 having a thickness of about 20 μm is formed on a substrate 1 (FIGS. 1A and 1B). Stainless steel was used for the substrate 1 and solder was used for the low melting point metal film 2. In this case, it is sufficient that the material of the substrate 1 withstands a temperature of about 200 ° C. to 300 ° C., and the substrate 1 is covered with a conductive material or a conductive metal film so as to also serve as a back surface electrode. The low-melting point metal may be a simple substance such as Sn, In, or Zn, or an alloy such as solder. Next, an average particle size of 50 μm
One or two layers of the n-type single crystal or polycrystalline silicon powder 6 are densely attached (FIG. 1 (c)). The size of the powder crystal is appropriately determined according to the lifetime, light absorption coefficient, wavelength used, and the like. The size of the crystalline silicon is preferably about 50 μm, but may be smaller. The shape of the powder need not be spherical, but may be any shape. There is no problem even if particles having different particle sizes are mixed.

Next, the low melting point metal 2 is melted, and the n-type crystalline silicon powder 6 is coated on the substrate 1 serving as the back electrode by the low melting point metal film 2.
(FIG. 1 (d)). Next, an i-type amorphous silicon layer 3 is formed at a substrate temperature of 200 ° C.
(e)). If the i-type amorphous silicon layer is too thick, the efficiency is reduced. If the i-type amorphous silicon layer is too thin, the front electrode and the back electrode are short-circuited.

Next, a p-type amorphous silicon layer 4 is formed at a substrate temperature of 200 ° C. (FIG. 1F). The thickness of the p-type amorphous silicon layer is desirably 100 ° to 200 °. This forms a heterojunction of p-type amorphous silicon and n-type crystalline silicon. Finally, a transparent conductive film 5 is formed on the amorphous silicon layer 4 (FIG. 1 (g)). If necessary, a metal collecting electrode is appropriately formed thereon to complete a large-area solar cell.

In the present solar cell, the movement of carriers in the lateral direction of the layer made of crystalline silicon powder 6 is hindered. However, in the solar cell having this structure, the movement of carriers in the thickness direction largely determines the efficiency. The efficiency is almost the same as when this layer is formed of a single crystalline silicon layer. In this embodiment, since the substrate temperature can be formed at 300 ° C. or lower throughout the entire process, restrictions on the material of the substrate are relaxed compared to the case where impurities are diffused at a high temperature to form a junction, and various substrates can be used. . Also, less production energy is required.

Embodiment 2 FIG. 2 is a view for explaining a manufacturing process of a solar cell according to a second embodiment of the present invention. This embodiment is a method for manufacturing a solar cell module having a series connection structure. First, as the substrate 1, glass,
Use an insulating or insulating material such as plastic (FIG. 2 (a)). Here, glass was used. A low melting point metal film 2 is formed in a strip shape on the substrate 1 (FIG.
(b)). This will be the back electrode.

Next, an n-type crystalline silicon powder 6 having an average grain size of 50 μm is arranged (FIG. 2C), and the low melting point metal film 2 is melted and bonded (FIG. 2D). Next, an i-type amorphous silicon layer 3 is formed on the upper surface of the crystalline silicon powder at a substrate temperature of 200 ° C. As shown in FIG. 2, the metal film is selectively formed so as to have a structure covering one end face of the metal film (FIG. 2E). Next, a p-type amorphous silicon layer 4 is selectively formed on the crystalline silicon powder 6 at a substrate temperature of 200 ° C. (Figure 2
(f)). The thickness of the p-type amorphous silicon layer is 100 to 20
0Å is desirable. This forms a heterojunction of amorphous silicon and crystalline silicon.

Finally, the transparent electrode 5 is selectively formed so as to be connected from the upper surface of the p-type amorphous silicon to the exposed end face of the lower electrode 2 of the adjacent strip-shaped element. Are connected in series (FIG. 2
(g)). As described above, a solar cell module in which adjacent solar cell elements are connected in series is formed.

In the above two embodiments, the crystalline silicon powder is n-type, but p-type may be used. In this case, the amorphous silicon layer is n-type.

[0019]

According to the photoelectric conversion element of the present invention, since a junction is formed by the amorphous semiconductor layer on the surface of the crystalline semiconductor powder, the junction can be formed at a low temperature, and a flexible substrate can be used as the substrate. Become. Further, since a crystalline semiconductor powder is used and the amorphous layer may be thin, the material used is smaller than that of a device using a crystal substrate, and the cost can be reduced. Further, the first conductivity type crystalline semiconductor powder and the
I-type amorphous semiconductor layer on exposed surface of low melting point metal layer
Just forming it can prevent short circuit between the substrate and the transparent conductive layer.
You. In addition, the thickness of the i-type amorphous semiconductor layer is
By setting the thickness to 00 °, a short circuit occurs between the substrate and the transparent conductive layer.
Without lowering the conversion efficiency.

Further, since the solar cell formed according to the present invention does not suffer from light degradation which has been a problem in amorphous solar cells, a highly reliable element can be produced.

On the other hand, according to the manufacturing method of the present invention, a solar cell element having a large area can be manufactured, a module can be easily connected in series by applying a thin film integration technique, and a required voltage output can be obtained. Can be made.

The present invention can be widely applied to photoelectric conversion devices, and can also be used as fine photoelectric conversion devices.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a photoelectric conversion element according to Example 1 of the present invention.

FIG. 2 is a diagram illustrating a manufacturing process of a photoelectric conversion element according to Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Low-melting-point metal film 3 i-type amorphous silicon layer 4 p-type amorphous silicon layer 5 transparent conductive film 6 crystalline silicon powder

Claims (3)

(57) [Claims] A substrate and a low melting point gold formed on the surface of the substrate
Metal layer and a second layer fixed on the substrate by the low melting point metal layer.
One conductivity type crystalline semiconductor powder and the first conductivity type crystal semiconductor
Body powder and an i-type electrode formed on an exposed surface of the low melting point metal layer.
A morphus semiconductor layer and the i-type amorphous semiconductor layer
A second conductivity type amorphous semiconductor layer formed thereon;
Transparent conductive layer formed on the second conductive type amorphous semiconductor layer
The photoelectric conversion device characterized Rukoto such from the conductive layer. 2. The thickness of the i-type amorphous semiconductor layer.
2. The light according to claim 1, wherein
Electric conversion element . 3. A low melting point metal layer is formed on a substrate,
Placing a first conductivity type crystalline semiconductor powder on the point metal layer,
The low melting point metal layer is heated and melted to remove the crystalline semiconductor powder.
Fixing the crystalline semiconductor powder and the low melting point
Forming an i-type amorphous semiconductor layer on the exposed surface of the metal layer
After that, the second conductivity type is formed on the i-type amorphous semiconductor layer.
Amorphous semiconductor layer and transparent conductive layer
3. The method for producing a photoelectric conversion element according to claim 1, wherein
Construction method.