JPH0484467A - Manufacture of solar cell - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a solar cell board at low cost and with ease by using a heat resisting mold whose surface is coated with boron nitride about the manufacturing method of a solar cell which charges silicon powder into the heat resisting mold, heat-melting the silicon powder, and manufactures the solar cell board. CONSTITUTION:A proper amount of Si powder is set into a recessed part of a mold 1 where a cover 2 is placed on the mold. The recessed part of the mold 1 is cut at a depth from 0.2 to 1mm. The depth of cut is capable of controlling the thickness of a Si board to be formed. Then, the surface between the mold 1 and the cover 2 is coated with boron nitride. The mold into which Si powder is charged, is set to a furnace where the whole mold is heated at a temperature which exceeds the melting point of silicon. After the Si is melted, the temperature is lowered so that the Si may be solidified. When BN is used as a parting agent, the BN applied for the coating is not fused to the Si. Therefore, it is unnecessary to coat every time so that the mold may be used repeatedly. The molten Si does not react with the mold, which makes it possible to part the Si from the mold easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a solar cell, and particularly to a method for manufacturing an inexpensive solar cell substrate.

[Conventional technology]

Figure 2 is a cross-sectional view showing how silicon (Si) powder is charged into a heat-resistant mold for manufacturing a conventional solar cell substrate. Part 2 is the same<BN mold, lid part, 3 is Si
It is a powder.

Furthermore, Fig. 3 shows the cross-sectional structure of a furnace for heating the mold charged with the Si powder shown in Fig. 2 at a high temperature, where 1 is the mold vessel shown in Fig. 2, 2 is the lid of the mold, and 3 is the mold lid. Si powder, 4 is a furnace container, 5 is a heater for heating the inside of the furnace to a high temperature, 6
7 is a reflective plate to prevent the heat of the heater 5 from escaping to the outside, and 7 is a mold 1.2 when the Si powder 3 is melted at a high temperature.
A weight 8 is used to apply pressure to the mold, similar to the weight 7.

Next, a method for manufacturing the solar cell substrate will be explained.

Set an appropriate amount of Si powder 3 in the concave part of the container 1 in Fig. 2,
Place lid 2 on top. The mold 1.2 filled with the Si powder 3 in this manner is placed inside the furnace 4 shown in FIG. and,
By heating the heater 5 with electricity, the inside of the furnace 4 is brought to a high temperature state. The reflector plate 6 is designed to prevent the heat of the heater 5 from escaping to the outside of the container and to maintain a uniform temperature distribution within the furnace. The entire mold was heated to the melting point of Si (1414°C
) After heating to melt the Si powder 3, the temperature is lowered to solidify the Si. During heating, a weight 7 is placed on the mold or pressure is applied with a brace 8 in order to make the molten Si conform to the mold. Solidified Si becomes plate-shaped, so
Take this out from mold vessel 1. After that, S
A solar cell is completed by applying common solar cell manufacturing methods such as shrimp growth and impurity diffusion.

[Problem to be solved by the invention] Since the conventional solar cell manufacturing method was as described above,
There was a problem in that the molten Si often fused to the mold 1.2, making it difficult to release the formed Si plate from the mold.

This invention was made in order to solve the above-mentioned problems, and it is possible to release molded Si from a mold into a container, making it possible to manufacture solar cell substrates inexpensively and easily. The purpose is to provide a method for manufacturing batteries.

[Means to solve the problem]

The method for manufacturing a solar cell according to the present invention includes using a heat-resistant mold whose surface is coated with borax nitride, charging Si powder into the mold, and heating and melting it to produce a solar cell substrate. This is what I did.

[Effect]

In this invention, since the surface of the heat-resistant mold is coated with borium nitride, the surface of the mold becomes smooth, making it difficult for molten Si to fuse to the mold, and allowing the molded Si plate to separate. It becomes easier to mold.

(Example〕 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a heat-resistant mold used in a solar cell manufacturing method according to an embodiment of the present invention. In the figure, 1 is a part of the heat-resistant mold made of, for example, BN, which has a higher melting point than Si. , 2 is the lid of the heat-resistant mold, 3 is Si powder as a substrate material, and 9 is a mold release agent.

Fig. 3 shows the cross-sectional structure of a furnace for heating the mold shown in Fig. 1 at high temperature, where 1 is the mold vessel shown in Fig. 1, 2 is the mold lid, and 3 is the Si silicon shown in Fig. 1. 4 is a furnace container, 5 is a heater to make the inside of the furnace high temperature, 6 is a reflection plate to prevent the heat of the heater 5 from escaping to the outside of the container, 7 is a Si powder 3 at high temperature. A weight 8 is a press mechanism for applying pressure to the mold, similar to the dust 7, to make it fit into the mold when melted.

Next, a method for manufacturing a Si substrate, which is a solar cell substrate, will be explained.

An appropriate amount of Si powder 3 is set in the concave part of the mold vessel 1 shown in FIG. 1, and a lid 2 is placed on it. The concave part of the container is cut to a depth of about 0°2 to 1 mm, and the amount of cut is determined by the amount of the Si to be formed.
The thickness of the substrate can be adjusted.

Next, the surfaces of vessels 1 and M2 are coated with borium nitride (BN). This coating method includes spraying BN powder dissolved in a solvent, directly applying it with a brush, etc.
Furthermore, there is a method of coating a very smooth N film using a CVD method or the like.

Next, the mold filled with Si powder is set in the furnace shown in FIG. By heating the heater 5 with electricity, the inside of the furnace is heated to a high temperature. The reflector plate 6 is designed to prevent the heat of the heater 5 from escaping to the outside of the container and to maintain a uniform temperature distribution within the furnace. The entire mold was heated to the melting point of Si (1414℃)
After heating to the above temperature to melt the Si, the temperature is lowered and the Si is melted.
solidify. During heating, a weight 7 is placed on the mold or pressing is performed using a press 8 to make the Si conform to the mold.

The solidified Si becomes a plate, and is then taken out from the container and used as a Si substrate.

Here, mold release agents have been used in the past (for example, Saito et al., 15th IEE Photovoltaic Ink Specialists Conference, 1981, pp. 576-580 (T, 5aito
Others, 15th IEEE Photovoltaic
5specialists Conference 19
81 pp., 576-580), silicon nitride powder (Si3N4) is used as the mold release agent, and there is no one that uses BN as in this example, and furthermore, in the experiment. As a result, it was found that silicon nitride has a poorer mold release effect than BN.

That is, the silicon nitride mold release agent has silicon nitride powder and Si
Silicon nitride fuses to the plate and mold, breaks contact between Si and the mold, and separates during mold release to achieve the mold release effect. However, in the case of BN, the surface of the mold is smoothed and the Si is released. It is presumed that the mold release effect is achieved by preventing the mold from getting wet.

Therefore, when silicon nitride is used as a mold release agent, it is necessary to apply the mold release agent every time, but when BN is used as the mold release agent, the coated BN does not fuse to the Si, so it is necessary to apply it every time. (The mold can be used repeatedly.)

Next, the mold release effect will be explained with reference to FIG. FIG. 4(a) is an explanatory diagram when molten Si is in direct contact with a BN vessel. BH molds are made by machining, so
When the surface is enlarged, it has a large uneven structure as shown in FIG. 4(a). Although it is generally said that BN does not easily react with Si, it has been observed that molten Si penetrates into the uneven structure, and in some places, molten Si penetrates into the BN mold as shown in 11. It was done. In such cases, it was difficult to easily release the Si plate from the mold.

Therefore, as shown in FIG. 4(b), when a mold release agent 9 made of BN is applied to the surface of a mold made of BN, the surface of the mold becomes smooth and there is no reaction between the mold and the Si plate.
As a result, it became very easy to release the molded 81 substrate.

In this example, the surface of the heat-resistant mold was coated with BN, so that the surface of the mold became smooth and the Si substrate did not react with the mold.
The i-substrate can be easily released from the mold. Furthermore, since BN was used as the mold release agent in this example, the mold release agent was not fused to the Si substrate when the molded Si substrate was released from the mold. Continuous use is possible as there is no need to coat each time.

In the above embodiments, BN was used as the mold material, but any material that can withstand the melting point of Si may be used, and other materials other than BN, such as silicon nitride, carbon, quartz, silicon carbide, etc. Possible materials include alumina.

In addition, in the above example, an example was shown in which BN was used as a mold release agent and only one layer was coated on the mold.
This embodiment is not limited to this, for example, BN
Two layers of 5iiN may be coated on the substrate.
A, BN may be sequentially coated to form a two-layer coating structure (or a combination of these may form a multi-layer structure, and the same effects as in the above embodiments can be obtained.

[Effects of the Invention] As described above, in this invention, a heat-resistant mold with a BN coating on the surface is used, so the molten Si does not react with the mold and can be easily released. effective.

Furthermore, since Si does not react with the mold release agent coated on the surface of the mold, the mold release agent does not peel off when the Si substrate is released from the mold, making it possible to use the mold repeatedly.
This has the effect that the i-substrate can be manufactured at low cost.

Furthermore, since the mold release effect is very good, the manufacturing process can be simplified.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view of a mold part used in a solar cell manufacturing method according to an embodiment of the present invention, FIG. 2 is a cross-sectional side view of a mold part used in a conventional solar cell manufacturing method, and FIG. 3 is a heating mold. , a cross-sectional side view of a furnace for pressing, and FIG. 4 is a diagram illustrating a comparison of the mold release effect of the solar cell substrate and mold according to the present invention and a conventional example. 1 is the container part of the mold, 2 is the lid part of the mold, 3 is Si
powder, 4 is a heating furnace container, 5 is a heater, 6 is a reflector, 7
is a weight, 8 is a press mechanism, 9 is a mold release agent, 10 is a molten S
i and 11 are the parts where the molten Si and the mold vessel are reacting. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a method for manufacturing a solar cell in which silicon powder is charged into a heat-resistant mold and the silicon powder is heated and melted to produce a solar cell substrate, the surface of the heat-resistant mold is coated with borax nitride. 1. A method for manufacturing a solar cell, characterized by using a solar cell.