JPS59223276A - Manufacture of sintered film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a sintered film for use in solar cells.

Conventional structure and problems One method for producing sintered films is to create a printing paste using semiconductor powder, apply this paste onto a substrate using a screen printing method, and then dry and bake it. There is a way to do it. In this manufacturing method, a flux is added to the printing paste in order to cause crystal growth of the semiconductor powder during firing. Sintering of a semiconductor film using such a flux has hitherto been mainly used as a method for manufacturing high-resistance photoconductive elements. In this case, the firing method is to put the substrate coated with the semiconductor film into a firing furnace as it is, or to put it in a sealed container and put it into the firing furnace.

However, Japanese Patent Publication No. 52-26305 describes the use of a firing container with a perforated lid in order to make the characteristics of the photoconductive elements uniform when producing a large number of high-resistance photoconductive elements on the same substrate. This is disclosed.

On the other hand, a semiconductor film for solar cells needs to have low resistance. However, with the method of manufacturing a sintered semiconductor film by applying a semiconductor layer to a substrate using screen printing and subsequent firing, it has been difficult to manufacture a low-resistance film for solar cells by leaving the substrate as is in a firing furnace. Should I put it in?
It was baked in a sealed container. However, in either case, it is difficult to obtain a low-resistance semiconductor film, and solar cells manufactured by firing films using a flux do not exhibit sufficient output characteristics and have not been put to practical use so far.

Hereinafter, the drawbacks of the conventional example will be explained in detail. Group II compound semiconductors are promising as semiconductor materials for solar cells, and thin film solar cells are being actively developed. In that case, CdCl2 is used as a flux to obtain a sintered film of CdS, CdSe, etc. However, a semiconductor film for solar cells must have low resistance, and when used as a window material for a heterojunction solar cell,
Although it is important to have high light transmittance, it has been difficult to obtain a sintered film that satisfies such requirements using a manufacturing method using a flux such as CdCl2. Cd the reason
This will be explained by taking the production of an S film as an example.

CdCl2 is used as a flux to obtain a CclS sintered film, and the effect of this flux on the sintered film is very large. For example, when a substrate coated with a CdS film is placed in a closed container and fired in a belt-type firing furnace, CdS first melts into the CdCl2 melt at a temperature above the eutectic point (522G), and then As the temperature increases, CdCl2 begins to evaporate.

As a result, CdS crystals grow in the supersaturated melt, and a CdS sintered film is obtained. However, in a closed container, this CdCl2 does not evaporate outside the container, so crystals grow sufficiently and a film with high transmittance is obtained. However, during firing, a large amount of CI- of CbCI2 remains in the film, and The resistance of the film becomes high and it cannot be used as a fired film for solar cells.

Also, if the substrate is placed in a belt furnace and fired,
Since the CdCl2 flux instantaneously evaporates in the film during sintering, CdS crystal growth does not occur sufficiently, resulting in a CdS film with small grain size. However, although this type of film results in less CI- remaining in the film, the growth of crystal grains is insufficient, resulting in a high resistance CdS film with low transmittance. It cannot be used as a sintered film for solar cells.

Therefore, if a hole is made in the lid of the firing container and the evaporation of the CdCl2 flux is controlled through the hole, sufficient crystal growth will occur, resulting in a low-resistance sintered film with a small amount of CI remaining in the film. Therefore, by changing the diameter and number of holes in the lid of the firing container, CdC can be obtained during firing.
A method for controlling the l2 flux evaporation rate was investigated. As a result, it was found that a low-resistance sintered film could be easily obtained with good reproducibility by adjusting the area of the substrate placed in the firing container and the area of the hole in the lid of the firing container.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor thin film with low resistance in manufacturing a solar cell made of a semiconductor thin film manufactured using a flux. In other words, the above-mentioned Tokko Akira! In Japanese Patent No. 2-26306, a manufacturing method in which a substrate is placed in a boat with a perforated lid and fired, which was used to equalize the photoconductive properties of multiple high-resistance photoconductive elements on the same substrate, has been improved. The aim is to obtain a resistive semiconductor thin film.

The film to be sintered is fired in a firing container with several openings.
In the production of the sintered film, the total area of the plurality of openings is made to be 4% to 2.0% of the area of the film to be sintered.

DESCRIPTION OF EMBODIMENTS Hereinafter, actual examples of the present invention will be explained based on the drawings. Figures 1 and 2 are partial views of the boat and lid of the firing container used to carry out the present invention, and Figure 3 is the structure of a solar cell manufactured by the method of the embodiment of the present invention. It is a diagram.

This paste was printed on the entire surface of a 10 cm x 10 cm glass substrate using a screen printer, and then dried in a dryer at 100 C for 1 hour. After drying, the substrate is placed in a firing boat 1 made of alumina, and a perforated lid 2 made of alumina is placed on top of it. The depth of the firing boat is 3 mm, and the size of the boat is 10.2 cm x 10.2 cm in inner diameter. This fired ut is placed in a belt-type firing furnace maintained at a temperature of 690C and fired for about 60 to 90 minutes. In order to examine the effect of the firing holes 3, alumina lids with different diameters and numbers of holes were fabricated, and the CdS substrates described above were fired. Using these approximately 30 μm thick CdS sintered films, their properties as solar cells were evaluated. A solar cell having the structure shown in FIG. 3 was manufactured in the following manner. C
A CdTe printing paste is made by adding 0.67 of CdCl2 powder to d powder and Te powder 1007 and mixing with an appropriate amount of propylene glycol. This printing paste is applied onto the CdS sintered film 6 on the glass substrate 4 by screen printing and dried. This substrate is placed in the above-mentioned alumina firing container and fired for about 1 hour at a temperature of 620C in a belt type firing furnace. The alumina firing containers used at this time are all the same, and the area of the holes in the lid is 181 holes of 1rrrm, and the total area of the holes is approximately 1.42a.
It is l.

A carbon layer is printed using carbon paste on the CdTe film 6 thus obtained, and the carbon electrode 7 is formed by firing it in a belt-type firing furnace at 400 C for about 30 minutes. An Aq electrode 8 was formed on the carbon electrode, and an Ag-Ir electrode 9 was formed on the CdS film by screen printing and subsequent heat treatment, and lead wires 10 were taken out from the Aq electrode and the Ag'-Ir electrode to form Cd S/Cd Te. A solar cell was created.

The energy conversion efficiency (intrinsic conversion efficiency) was measured by irradiating this solar cell with light from a solar simulator of A M 1 * 6100”W/cm. Characteristics of each CdS film and these CdS/Cd T e when the total area of holes in the lid is changed
The characteristics of solar cells were shown.

Table 1 As is clear from Table 1, when the total area of the lid size is small, the sheet resistance of the CdS film is high and the amount of CI remaining in the film is also large. However, as the total area of the holes increases, the sheet resistance decreases, and when the total area of the holes is in the range of 0.4 to 2 mOa, the sheet resistance of 70 to 180 Ω/hole is almost constant. A membrane has been obtained. However, when the total hole area is further increased, the sheet resistance of the CdS film gradually increases and the crystal grain size also begins to decrease. This decrease in crystal grain size causes an increase in film resistance and a decrease in light transmittance.

Looking at the effects of the above characteristics of the CdS film on the conversion efficiency of a solar cell, the conversion efficiency is poor when the total area of the holes is 0.3 cd or less. This is largely due to the high sheet resistance of the CdS film and the decrease in sensitivity on the short wavelength side as shown by curve 11 of the spectral sensitivity characteristic in FIG. This is C
This is due to the amount of CI remaining in ,dSlq, and if a large number of solar cells are produced, a thick CdS layer will be formed at the interface between the CdS film and the CdTe film due to the action of CI-.
It was found that a x T e 1-x layer was formed and the sensitivity on the short wavelength side decreased due to light absorption by this layer. Therefore, it is desirable that the amount of C1- remaining in the CdS film is small. When a solar cell is fabricated using a CdS film with a total hole area of 0.4 cm or more, the spectral sensitivity characteristics are as shown in curve 12, where the sensitivity on the short wavelength side is at the fundamental absorption edge of the CdS film (
0.52 μm), and no influence on the characteristics by the residual cl-g was observed.
Solar cells ranging from ta to 2, Ooti are Cd51
The sheet resistance of lQ＼,゛ is low, and the crystal grain size is 26 to 36 μm.
Because of its large size and high light transmittance, the intrinsic conversion efficiency is 7.0~
It is high and stable at 8.5%. However, the total area of the holes is 3.
1cI! In the above case, the remaining CI amount is the total area of the holes 0.
4-2. It is low as in the case of OCl, and there is no decrease in sensitivity on the short wavelength side, but when the sheet resistance of the CdS film starts to increase, the intrinsic conversion efficiency decreases due to the decrease in light transmittance due to the decrease in crystal grain size. has started to decline due to the increase in large area and is 7.0%
I couldn't get more than that.

As described above, it was found that changes in the total area of the holes in the lid of the alumina firing container during CdS film firing clearly change the characteristics of the CdS film and the CdS/CdTe solar cell fabricated using it. . In other words, when the total area of the holes is small, the amount of C1- remaining in the CdS film has a negative effect on the photovoltaic properties, and when the total area of the holes is large, the CdS film
The crystal grain size of the film did not grow sufficiently, resulting in high film resistance and low light transmittance, making it impossible to obtain a solar cell with high conversion efficiency. A film that exhibits characteristics of sufficiently low resistance and high light transmittance as a CdS film for solar cells has a total area of 0.4 to Q m Ocr 1 m & obtained Pa IJ, which poses no practical problem. .

In addition, when producing CdS printing paste, CdCl2 powder α
A similar experiment was carried out by changing the concentration from 26 to 12 y to 100 y of CdS powder, but the trend was almost the same as in Table 1. When the total area of the lid is 0.4 to 2,000 y,
The resistance of the CdS film was low and the conversion efficiency of the solar cell was high. Still, the holes of the alumina lid hole are the same size on the left and right,
If the CdS film is arranged uniformly and vertically symmetrically, the film resistance of the CdS film will be uniform, and the variation in resistance value will be 1Q×1.
It was within ±10% for o\ct4 substrate. A similar tendency occurs during firing of the CdTe film that forms this CdS film junction, and when the total area of the alumina lid holes for firing is within the above range, the best junction characteristics are obtained, and the conversion efficiency of the solar cell is also improved. It was high at 7.0-8.6%.

Furthermore, Zn, which is used as a window material for solar cells,
Similar results were obtained for the xCd1-xS film (x=o, 1) when CdCl2 was used as the fluxing agent. When the total area of insertion is 0.4~2a0cnf, the resistance of ZnxCd, -xS sintered film is lowest at 300~
The resistance was 600Ω/mouth.

Such alumina firing containers can be made of any material that is chemically and heat resistant, such as quartz glass or porcelain, and the holes in the lid can be made of any material.
A similar effect can be obtained even if there is a part other than a hole through which CdCl2 can pass.

Effects of the Invention According to the method of the present invention, a sintered film with low resistance can be stably obtained by simply adjusting the large area of the lid by using a firing container with a perforated lid when producing a sintered film using a flux. It will be done. That is, until now it has been difficult to obtain a low-resistance fired film for solar cells, but according to the method of the present invention, the total area of the lid size during firing is 0.4 to 2.0% of the sintered film area. A low-resistance film can be easily obtained by using only a firing container, and its industrial advantages are great.

In addition, solar cells with high conversion efficiency can be manufactured with good reproducibility without losing the characteristics of the screen printing belt furnace firing method, which is a manufacturing method that allows easy mass production of inexpensive and practical solar cells. There are also advantages.

[Brief explanation of the drawing]

Figure 1 (color) is a plan view of the boat portion of the firing container used in the method for producing a sintered film of the present invention, Figure 1 (b) is a cross-sectional view of the same,
FIGS. 2(a) and (b) are a plan view and a sectional view of the lid of the firing container, respectively, FIG. 3 is a sectional view showing the structure of a solar cell manufactured by the manufacturing method of the present invention, and FIG. 4 1 is a comparison diagram of spectral sensitivity characteristics for explaining the effects of a solar cell manufactured by the manufacturing method of the present invention. 1... Boat of the firing container, 2... Lid of the baking container 3... Hole in the lid, 4... Glass substrate, 5...・CdS film, 6...CdT
e film, 7... Carbon film, 8... Aq main electrode 9...Ag-In electrode, 1o...
··Lead. Patent applicant: Director of the Agency of Industrial Science and Technology

Claims (1)

[Claims] In the production of a sintered film, the total area of the plurality of openings is 0.4% to 2.0% of the area of the film to be sintered.
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