JPH0548126A - Photoelectric conversion element and its manufacture - Google Patents

Abstract

PURPOSE:To provide a basic structure for manufacturing an inexpensive photoelectric conversion element and the manufacturing method of the conversion element. CONSTITUTION:This photoelectric conversion element is formed by successively forming an i-type amorphous silicon layer 3, p-type amorphous silicon layer 4, and transparent conductive film 5 on a substrate 1 after n-type crystalline silicon powder 6 is stuck to the surface of the substrate 1 by melting a low- melting point metal 2. When such structure is used, an inexpensive photoelectric conversion element can be manufactured, because the need of a crystalline silicon substrate which has been an obstacle in reducing the cost of photoelectric conversion elements can be eliminated. In addition, the area and degree of integration of the element can be increased.

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, which makes it possible to manufacture an inexpensive photoelectric conversion element.

[0002]

2. Description of the Related Art Photoelectric 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, but these have advantages and disadvantages. is there. That is, the one 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 are problematic in terms of reliability. Although the one using a polycrystalline substrate is in the middle of the above in performance and price, it is still not sufficiently low in price.

On the other hand, in 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 impurities are partially doped in the semiconductor powder to form a pn junction.

[0004]

In a conventional photoelectric conversion element using a single crystal substrate or a polycrystalline substrate, a substrate having a thickness greater than that required for the element is used, which causes an unnecessary increase in cost. Was becoming. On the other hand, in the photoelectric conversion element using the single crystal or polycrystalline semiconductor powder, unlike the one using the single crystal or polycrystalline substrate, it is possible to reduce the cost without wastefully using the material.

However, a solar cell using a crystalline semiconductor powder, which is an example of a conventional photoelectric conversion element, uses a high temperature process by impurity diffusion for junction formation, and in the case of actually forming it as an element, extraction of electrodes on the surface is taken out. Also, problems such as insulation between the front surface electrode and the back surface electrode have not been sufficiently solved.

[0006]

In order to achieve the above object, the present invention comprises the steps of sequentially forming an i-type amorphous semiconductor layer and a second conductivity type amorphous semiconductor layer on a first conductivity type crystalline semiconductor powder. A photoelectric conversion element characterized by being provided.

A low melting point metal layer is formed on a substrate, and first-conductivity-type crystalline semiconductor powder is densely arranged on the low melting point metal layer,
The low melting point metal layer is heated to fix the crystalline semiconductor powder to the low melting point metal layer, and an i-type amorphous semiconductor layer and a second conductivity type amorphous semiconductor layer are sequentially formed on the crystalline semiconductor powder. A method for manufacturing the photoelectric conversion element of the present invention is provided.

[0008]

The photoelectric conversion element of the present invention basically comprises one crystal semiconductor powder of the first conductivity type, an i-type amorphous semiconductor layer formed thereon, and an amorphous semiconductor layer of the second conductivity type. It functions as one photoelectric conversion element, and the carrier moves in the stacking direction. Then, these basic elements are connected by electrodes 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.
Is fixed and the i-type amorphous semiconductor layer and the second conductivity type amorphous semiconductor layer (for example, p-type amorphous Si
The bonding with the layer prevents the front electrode from coming into direct contact with the substrate surface, which is the back electrode. A backside electrode connected to the crystalline semiconductor powder is formed on the substrate surface, or the substrate itself serves as the backside electrode, and this backside electrode is formed due to the gap of the crystalline semiconductor powder when the junction is formed by the amorphous semiconductor layer. In order to prevent the amorphous semiconductor layer from short-circuiting, a junction between the i-type amorphous semiconductor layer and the second conductivity type amorphous semiconductor layer (for example, p-type amorphous Si layer) is provided. Then, according to the present manufacturing method, a large-area photoelectric conversion element in which a layer made of crystalline semiconductor powder and an amorphous semiconductor layer are formed in this order on the substrate is formed.

[0010]

The present invention will be described in detail with reference to the following examples.

Example 1 FIG. 1 is a diagram for explaining a manufacturing process of a solar cell element according to the present invention. First, the low melting point metal film 2 having a thickness of about 20 μm is formed on the 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, the material of the substrate 1 may be one that can withstand a temperature of about 200 ° C. to 300 ° C., and it is covered with a conductive material or a conductive metal film to serve also as a back electrode. The low melting point metal may be a simple substance such as Sn, In, or Zn, or an alloy such as solder. Next, the average particle size is 50 μm on the low melting point metal film 2.
One or two layers of the n-type single crystal or polycrystal silicon powder 6 are densely adhered (FIG. 1 (c)). The size of the powder crystal is appropriately determined according to the lifetime, the absorption coefficient of light, the wavelength used, and the like. The size of the crystalline silicon is preferably about 50 μm, but it may be smaller than this. The shape of the powder does not have to be spherical and may be any shape. Also, 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 applied to the substrate 1 serving as the back electrode to form the low melting point metal film 2
It is fixed via (Fig. 1 (d)). Next, the i-type amorphous silicon layer 3 is formed at a substrate temperature of 200 ° C. (see FIG. 1).
(e)). If the i-type amorphous silicon layer is too thick, the efficiency is reduced, and if it 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. 1 (f)). The film thickness of the p-type amorphous silicon layer is preferably 100Å to 200Å. As a result, a heterojunction composed of p-type amorphous silicon and n-type crystalline silicon is formed. Finally, the transparent conductive film 5 is formed on the amorphous silicon layer 4 (FIG. 1 (g)). If necessary, a metal collector electrode is appropriately formed on this to complete a large-area solar cell.

In this 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 of this structure, the movement of carriers in the film thickness direction almost 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 can be relaxed and various substrates can be used as compared with the case where impurities are diffused at a high temperature to form a junction. .. Also, it requires less manufacturing energy.

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

Next, n-type crystalline silicon powder 6 having an average grain shape of 50 μm is placed (FIG. 2 (c)), and the low melting point metal film 2 is melted and adhered (FIG. 2 (d)). Next, the 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 that covers one end surface of the metal film (FIG. 2E). Next, the p-type amorphous silicon layer 4 is selectively formed on the crystalline silicon powder 6 at the substrate temperature of 200 ° C. (Fig. 2
(f)). The thickness of p-type amorphous silicon layer is 100Å ~ 20
0Å is desirable. As a result, a heterojunction of amorphous silicon and crystalline silicon is formed.

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 surface of the lower electrode 2 of the adjacent strip-shaped element, and each strip-shaped element is formed. 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.

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

[0019]

Since the photoelectric conversion device of the present invention forms a bond on the surface of the crystalline semiconductor powder by the amorphous semiconductor layer, the bond can be formed at a low temperature, and a flexible substrate can be used as the substrate. Become. Further, since the crystalline semiconductor powder is used and the amorphous layer may be thin, less material is used and the cost can be reduced as compared with the element using the crystal substrate.

Further, the solar cell formed according to the present invention does not suffer from the photodegradation which has been a problem in the amorphous solar cell so far, so that a highly reliable element can be produced.

On the other hand, according to the manufacturing method of the present invention, a solar cell device having a large area can be manufactured, and the series connection is easy due to the application of the thin film integration technology, and the required voltage output can be obtained in the module. 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 drawings]

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

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

[Explanation 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 (2)

[Claims] 1. A photoelectric conversion element, comprising an i-type amorphous semiconductor layer and a second-conductivity type amorphous semiconductor layer sequentially formed on a first-conductivity-type crystalline semiconductor powder. 2. A first-conductivity-type crystalline semiconductor powder is placed on a low melting point metal layer formed on a substrate, and the metallic layer is heated and melted to fix the crystalline semiconductor powder onto the metallic layer,
The method for producing a photoelectric conversion element according to claim 1, wherein an i-type amorphous semiconductor layer and a second conductivity type amorphous semiconductor layer are sequentially formed on the crystalline semiconductor powder.