JPH1131830A - Method for depositing metal oxide and compound semiconductor solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation of characteristics by heating the mixture powder of an organic metal compound and a fluorine compound to sublimate the mixture powder directly or to bring the mixture powder into gas state, bringing the gas into contact with a heated heat-resistant substrate to decompose the gas thermally and depositing a metal oxide on the substrate thereby imparting a long term reliability. SOLUTION: A substrate 1 is set on a substrate heater 7 and a nozzle 10, facing the substrate 1, is coupled with a tube extending from a powder injection container 8 and a tube extending from a carrier gas introduction port 6. The nozzle 10 is provided, at the bottom thereof, with a port 3 for jetting the mixture powder of an organic metal compound or a metal compound and a fluorine compound or an antimony compound. The mixture powder in the powder injection container 8 is jetted from the jetting port 3 into a heating zone 4 by a carrier gas introduced from the carrier gas introduction port 6. The mixture powder is sublimated directly by a heater 9 and brought into gas state and then the gas is brought into contact with the substrate and decomposed thermally thus depositing a metal oxide 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a metal oxide film and a solar cell having a cadmium sulfide / cadmium telluride film formed on the metal oxide film.

[0002]

2. Description of the Related Art Heretofore, a transparent conductive film used for a solar cell has been formed by forming a tin oxide film on a glass substrate by a vacuum evaporation method or a sputtering method. Further, it has also been formed by a coating sintering method in which a tin oxide film is formed by applying an organic tin compound to a substrate and heat-treating it. Recently, an organometallic compound or a metal compound is placed in a heating vessel and heated, a substrate for film formation is placed in the vapor of the generated compound, and these compounds are thermally decomposed on or near the substrate surface, Chemical vapor deposition (CV) to form a metal oxide film on a substrate
D method) has been proposed (Japanese Patent Publication No. 55-18785).

A conventional CdS / CdTe solar cell has a cadmium sulfide film formed on a tin oxide film formed by a sputtering method or an evaporation method, and a cadmium telluride film formed thereon. In addition, CIS
Solar cells are made of copper plates or copper,
Metal plates such as iron, stainless steel, aluminum, etc.
Using palladium, molybdenum or the like, or a conductive electrode surface formed on an electrically insulating sheet or the like, a p-type semiconductor layer made of cadmium telluride or copper indium selenide is formed on this substrate, Further, the p
A cadmium sulfide film is formed on the n-type semiconductor layer as a window layer of an n-type semiconductor by a solution growth method to form a pn junction, and a metal oxide film is formed on the CdS film by a sputtering method to form a solar cell. Battery cells have been manufactured.

[0004] When a tin oxide film is formed by using a vacuum deposition method such as a vacuum evaporation method or a sputtering method, there is a problem in that the apparatus cost is increased. In particular, in order to form a film having a large area of 100 cm ² or more, a large-sized apparatus is required, and the cost of the apparatus is high. Also, when forming a high quality film,
In the vacuum film forming method, the film forming speed is low. For example, a film thickness of 1000
When forming an Angstrom tin oxide film, it takes about 10 to 30 minutes. Further, the uniformity of the obtained film is poor, and the uniformity of the film thickness is not good. For example, 30
Within the substrate surface of × 30 cm ^2, the variation in the film thickness between the center and the end of the substrate is 20 to 30%. On the other hand, the coating sintering method can form an inexpensive and large-area tin oxide film. However, when the film manufactured by this method is left in a high-temperature and high-humidity atmosphere for a long time, the film resistance changes by 20 to 30%. Therefore, when a solar cell is manufactured using this and used outdoors for a long period of time, there arises a problem that the resistance value of the metal oxide film increases with time and the conversion efficiency decreases. Therefore, it is rarely used at present.

[0005] In the CVD method, it is difficult to control the concentration of steam generated from the heating vessel. In particular, since the vapor pressures of the source material and the dope material are different, it is difficult to control the doping amount of the obtained tin oxide film. Further, in order to produce a high-quality film having a uniform film quality over a large area, an expensive apparatus is required. Among the above-described methods of forming a tin oxide film, a tin oxide film is formed by using a vacuum evaporation method or a sputtering method having a relatively small change in resistance under high temperature and high humidity, and CdS / CdTe is formed.
When a solar cell is manufactured, the manufacturing cost of the metal oxide film is high, so that the manufacturing cost of the entire solar cell increases. When the area is large, the quality of the metal oxide film becomes non-uniform.
% Cannot be manufactured. Further, there is a problem that characteristics are deteriorated due to a variation in the film resistance of the metal oxide film.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is inexpensive, has excellent mass productivity, and has high long-term reliability.
It is an object of the present invention to provide a manufacturing method for manufacturing a large-area metal oxide film with small characteristic variations on a substrate such as glass. Still another object is to provide a low-cost and high-efficiency solar cell using the metal oxide film obtained by this manufacturing method.

[0007]

According to a method of manufacturing a metal oxide film according to the present invention, a mixed powder of an organometallic compound or a metal compound and a fluorine compound or an antimony compound is uniformly dispersed by a carrier gas and sprayed. Step, heating the mixed powder, directly sublimation, or the step of evaporating through melting to a gas state, and thermally decomposed by contacting the gas on a heated heat-resistant substrate,
Forming a metal oxide film on the substrate. further,
An excellent solar cell can be obtained by forming a solar cell by using the metal oxide produced according to the present invention for a negative electrode connected to an n-type semiconductor film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A fluorine compound and an antimony compound are doped into a metal oxide film in a certain amount, whereby
It has the effect of lowering the film resistance of the metal oxide film. By controlling the amount of these fluorine compounds or antimony compounds added to the organometallic compound or metal compound,
It is possible to control the vapor partial pressure of the fluorine compound or antimony compound in the vapor of the mixed powder. That is, since the ratio of these compounds contained in the mixed powder and the ratio in the formed oxide film match, the doping amount of the fluorine compound or antimony compound in the obtained metal oxide film can be freely controlled. Becomes easier.

In terms of the effect of lowering the film resistance and the high light transmittance, it tends to be better to use a fluorine compound as the dopant. Further, since the resistance value of the obtained oxide film slightly changes depending on the addition amount of the fluorine compound or the antimony compound, it is necessary to select an optimum addition amount.

The organometallic compound and the metal compound preferably contain at least tin. This is because the tin oxide film has characteristics of good light transmittance and low resistance, and is suitable for use as a transparent conductive film of a solar cell. Further, since the alkyl metal halide and the metal halide have a property of being thermally decomposed on the film-forming substrate to form a high-quality oxide film on the substrate surface, the organometallic compound is an alkyl metal halide and the metal compound It is preferably a metal halide such as tin tetrachloride.

The temperature of the film-forming substrate must be maintained at a temperature at which the vaporized source is thermally decomposed into tin oxide. This temperature differs depending on the type of the source, and it is desirable to process at a temperature suitable for each source. In particular, maintaining the temperature of the substrate in the range of 300 to 600 ° C.
It is preferable because the film formation speed is the fastest and the obtained film quality is excellent. Also, the deformation of the glass substrate is small. When the temperature of the substrate is lower than 300 ° C., the film formation speed is greatly reduced and the film resistance is increased. On the other hand, if the temperature is higher than 600 ° C., the glass substrate is deformed, so that a smooth film cannot be formed.

As the film forming substrate, glass, metal, ceramic or plastic can be used. Specifically, stainless steel, titanium, aluminum, copper, iron and the like can be used as the metal substrate, and alumina, zirconia, silica and the like can be used as the ceramic substrate. Further, as the plastic substrate, a fluororesin or the like is preferable. In particular, since glass has high heat resistance, it can be applied to a source having a high thermal decomposition temperature. Although plastics are inexpensive and there are many types, many of them have low heat resistance, so that they can be applied to a source having a low thermal decomposition temperature.

The thickness of the obtained metal oxide film can be controlled by controlling the time for spraying the source material. When the film thickness is small, the voltage loss of the product increases due to the increase in the sheet resistance, which causes a problem in function. When the film thickness is large, the light transmittance decreases, and when used for a solar cell or the like, the performance decreases.

Since the heating vessel having a simple structure is used for manufacturing the metal oxide film according to the present invention, the cost of the apparatus can be reduced. Furthermore, a high-quality, large-area metal oxide film can be obtained at low cost in a short time. Among the metal oxide films obtained according to the present invention, the film thickness is 100 to ¹⁰⁰⁰⁰ angstroms, and the resistivity is 1 × 10 ⁻⁶ to 1 × 10 ⁻² Ω · c.
m, a transparent conductive film having a light transmittance of 50% to 95% in a visible region having a light wavelength of 400 to 800 nm has excellent electrical and optical characteristics as a transparent conductive film.
Therefore, when a solar cell is constructed using the metal oxide film produced according to the present invention as a transparent conductive film, a solar cell having excellent performance can be obtained.

For example, a transparent conductive film is formed on a transparent and insulating substrate, and a compound semiconductor film made of cadmium sulfide is formed on the transparent conductive film as a window layer of an n-type semiconductor. A cadmium telluride film is formed as a p-type semiconductor layer on the compound semiconductor film to form a pn junction. Then, a current collector is formed on the p-type semiconductor film, a positive electrode electrically connected to the current collector is formed, and a negative electrode electrically connected to the transparent conductive film is formed. Thus, it is preferable to form a compound semiconductor solar cell.

The cadmium sulfide film is preferably prepared by thermally decomposing an organometallic complex, and the cadmium telluride film is preferably formed by a print coating sintering method or a proximity sublimation method. In such a solar cell, the light transmittance of the metal oxide thin film is high and the quality of the compound semiconductor film is also high, so that the photoelectric conversion efficiency is high.

Further, on a substrate having conductivity and heat resistance,
A p-type semiconductor layer made of cadmium telluride or copper indium selenium compound is formed, and a compound semiconductor film made of cadmium sulfide described above is formed as an n-type semiconductor film on the p-type semiconductor layer to form a pn junction. . Then, a transparent conductive film is formed on the n-type semiconductor film, and a negative electrode electrically connected to the transparent conductive film is formed. And p
A compound semiconductor solar cell may be formed by forming a positive electrode electrically connected to the type semiconductor film on the type semiconductor film. This conductive and heat-resistant substrate, copper plate, or copper, iron, stainless steel, on one side of a metal plate such as aluminum,
A material plated with copper, silver, platinum, palladium, molybdenum, or the like, or a conductive electrode formed on an electrically insulating sheet can be used.

[0018]

FIG. 1 shows a structural example of an apparatus for forming a metal oxide film on a substrate surface. Reference numeral 1 denotes a film-forming substrate. A metal oxide film (transparent conductive film) 2 is formed on the surface of the substrate 1. The substrate 1 is placed on a substrate heater 7 and is heated by the substrate heater 7 to a temperature at which a source material can be thermally decomposed. In opposition to this substrate, there is a nozzle 10 provided with a source powder outlet 3 at the bottom. The nozzle 10 is connected with a pipe extending from the powder injection container 8 and a pipe extending from the carrier gas inlet 6. Further, a heating zone 4 is provided between the substrate 1 and the ejection port 3.

The heating zone 4 can be set to a desired temperature by a heater 9 provided on the side surface. When the temperature of the heating zone 4 is set to a temperature at which the source powder evaporates through sublimation or melting, the source powder that has passed through this zone can be brought into a gaseous state. The temperature of the heating zone 4 is most preferably in the range from the melting point of the organometallic compound to the boiling point. If the temperature is higher than the thermal decomposition temperature of the organometallic compound, thermal decomposition occurs in the heating zone 4 and no thermal decomposition reaction occurs on the surface of the glass substrate, so that a metal oxide film is not formed. The source powder in the powder injection container 8 is sprayed by the carrier gas introduced from the carrier gas inlet 6 into the ejection port 3.
Injected from. The injected source powder is vaporized in the heating zone 4. The vaporized source material is heated substrate 1
, And is thermally decomposed to deposit as a metal oxide film (transparent conductive film) 2.

Example 1 Trimethyltin chloride powder and antimony fluoride powder, which are alkyl metal halides, were mixed with 10
The mixture was mixed at a weight ratio of 0: 2, and the source powder injection container 8 of FIG.
I entered. The temperature of the heating zone 4 was set to 100 to 150 ° C., and the glass substrate was heated to 550 ° C. by the substrate heater 7. The size of the substrate was 30 × 30 cm ² . The source material was ejected from the ejection port 3 of the nozzle 10 for 20 seconds. The thickness of the tin oxide film formed at this time was 4000 Å. The film resistance of the obtained tin oxide film was a sheet resistance of 20 to 21 Ω / □, and the variation in the film resistance depending on the position in the glass substrate surface was within 5%. Also,
When the light transmittance was measured, the wavelength range was 400 to 800.
It was 50-90% in nm.

Example 2 The size of the glass substrate was set to 100
Except that it is × 100 cm ² , the same as in Example 1
A tin oxide film was formed. The variation in the film resistance of the obtained tin oxide film depending on the position in the glass substrate surface was within 10%, which was extremely small. Also, when the light transmittance was measured,
The wavelength range was 50 to 90% at 400 to 800 nm.

Example 3 A tin oxide film was prepared by using tetramethyltin or dimethyltin dichloride instead of trimethyltin chloride of Example 1. Further, a tin oxide film was formed using tin tetrachloride which is a metal halide. The resistivity of each of the obtained tin oxide films was 1 × 10 ⁻⁶ Ω · cm,
It had excellent performance. In addition, a high-temperature and high-humidity test was performed on a tin oxide film formed using dimethyltin dichloride, tetramethyltin, and methyltin chloride at 60 ° C. and 95% RH, and the change over time in resistivity was examined. Table 1 shows the results.

[0023]

[Table 1]

According to Table 1, the change in the resistivity of the film after 2000 hours was within 10%, which was stable.

Example 4 A solar cell was manufactured using the tin oxide film obtained in Example 1 as a transparent conductive film. FIG. 2 is a sectional view of the structure. A tin oxide film 12 is formed on a glass substrate 11 as in Example 1, and a cadmium sulfide film 14 is formed on the tin oxide film 12 by a thermal decomposition method of an organometallic compound. The cadmium telluride film 15 is formed by proximity sublimation. Further, a carbon electrode 16 is formed on the cadmium telluride film 15 and Ag is formed on the cadmium sulfide film 14 and the carbon electrode 16.
The compound semiconductor solar cell element is formed by manufacturing the In electrode 17.

Specifically, the cadmium dimethyldithiocarbamate complex is heated and vaporized, and the vapor contains
The glass substrate 11 heated to 50 ° C. was set. The tin oxide film 1 was previously formed on the glass substrate 11 in the same manner as in Example 1.
2 was formed, and the substrate was set so that the vapor was applied to the tin oxide film. The vapor of the cadmium dimethyldithiocarbamate complex was thermally decomposed on the surface of the tin oxide film 12 to form a cadmium sulfide film 14 on the surface 12 of the tin oxide film.

Further, a glass substrate formed with tin oxide and cadmium sulfide was placed in a vessel in which a cadmium telluride source was placed, and the pressure in the vessel was reduced to 1 torr. Subsequently, the cadmium telluride source is heated to 640 ° C.
The glass substrate was set at 600 ° C. and held for 2 minutes to form a cadmium telluride film 15 on the cadmium sulfide film 14. Further, a carbon electrode 16 is formed on the cadmium telluride film 15, and the cadmium sulfide film 14 is formed on the carbon electrode 16.
An AgIn electrode 17 was formed thereon. The photoelectric characteristic of the CdS / CdTe solar cell thus manufactured is 100 m
The conversion efficiency was 14.5% under a light source of W / cm ² .
The characteristic variation of the solar cell was within 10%.

Example 5 A soda lime plate was used as a thin film forming substrate, and a molybdenum electrode was formed on one surface of the substrate by a vapor deposition film method. Further, a copper indium selenide (CIS) thin film was formed by a multi-source evaporation method comprising copper, indium, and selenium. Further, a cadmium sulfide film was formed thereon in the same manner as in Example 5, and a tin oxide was formed thereon in the same manner as in Example 1. FIG. 3 shows the characteristics of this solar cell. From FIG. 3, the characteristics of this solar cell are such that the open-circuit voltage is 560 m under a light source of 100 mW / cm ^2.
V, short circuit current 40 mA / cm ² , conversion efficiency η = 14.2
%Met.

[0029]

As described above, according to the present invention, a metal oxide film having a large area, uniformity, and excellent weather resistance can be formed by using an inexpensive and simple heating device. Also,
By using such a metal oxide film, a solar cell with good conversion efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration example of an apparatus for forming a metal oxide film on a substrate surface according to the present invention.

FIG. 2 is a longitudinal sectional view of a solar cell formed using a metal oxide film according to the present invention.

FIG. 3 is a characteristic diagram of one embodiment of the solar cell according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 film-forming substrate 2 transparent conductive film 3 spout 4 heating zone 5 source powder 6 carrier gas inlet 7 substrate heater 8 source powder injection container 9 heater 10 nozzle 11 glass substrate 12 tin oxide film 14 CdS film 15 CdTe film 16 Carbon electrode 17 AgIn electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Shibuya 1-1, Matsushita-cho, Moriguchi-shi, Osaka Matsushita Battery Industry Co., Ltd. (72) Mikio Murozono 1-1-1, Matsushita-cho, Moriguchi-shi, Osaka Matsushita Battery Industrial Co., Ltd.

Claims (8)

[Claims] 1. A step of spraying a mixed powder of an organometallic compound or a metal compound and a fluorine compound or an antimony compound with a carrier gas, a step of bringing the powder into a gaseous state, and a heat-resistant substrate heated by the gas. Forming a metal oxide film on the substrate by contacting the metal oxide film on the substrate. 2. The method according to claim 1, wherein the organometallic compound and the metal compound contain at least tin. 3. The method according to claim 1, wherein the organometallic compound is an alkyl metal halide. 4. The method according to claim 1, wherein the metal compound is a metal halide. 5. The temperature of the heated film-forming substrate is:
The method for producing a metal oxide film according to claim 1, wherein the temperature is 300 to 600 ° C. 5. 6. The method for producing a metal oxide film according to claim 1, wherein said film forming substrate is glass, metal, ceramic or plastic. 7. An insulating and light-transmitting substrate, a transparent conductive film formed on the substrate, an n-type semiconductor film made of cadmium sulfide formed on the transparent conductive film, and an n-type semiconductor film formed on the n-type semiconductor film. A formed p-type semiconductor layer made of cadmium telluride as a light absorbing layer, a current collector formed on the p-type semiconductor layer, a positive electrode electrically connected to the current collector,
A solar cell comprising: a negative electrode electrically connected to the n-type semiconductor layer; and the transparent conductive film is a metal oxide film formed by the method according to claim 1. 8. A p-type semiconductor film made of cadmium telluride or copper indium selenide formed on a substrate having conductivity and heat resistance, and a window layer of an n-type semiconductor formed on the p-type semiconductor film. A cadmium sulfide film, a transparent conductive film formed on the cadmium sulfide film, a negative electrode electrically connected to the transparent conductive film, and a positive electrode electrically connected to the substrate, A solar cell, wherein the transparent conductive film is a transparent conductive film formed by the method according to claim 1.