JPH1167677A - Stannous oxysulfide film and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit an efficient and readily manufacture of a semiconductor material without containing elements having toxicity, which can be comparatively readily supplied and has no limitation in supply amount, by supplying a solution containing tin dichloride and thiounea of a specific concentration to a substrate which has been heated to a temperature within a specific range. SOLUTION: A solution containing tin dichloride of 0.001-0.12 M and thiourea at a molar ratio of 0.1-10 times the tin dichloride is supplied to a substrate 4 which has been heated to 175-425 deg.C. An atomizer 3, which has a structure of two-fluid-type spray gun, atomizes the solution provided from a solution supply portion 1 by means of a compressed air from a carrier gas supply portion 2 so as to spray the atomized solution 15 to the substrate 4 which has been heated to a predetermined temperature by a heater 5, thereby forming a stannous sulfide film 16. On the other hand, a sheath-type thermocouple is arranged at a side surface of the substrate 4 to control the heater 5 by a PID controller so that the temperature at the central portion of the surface of the substrate 4 is settled in a predetermined range of value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a tin oxysulfide film and a method for producing the same.
The present invention relates to a thin film composed of only a tin oxysulfide crystal or a thin film mainly composed of a tin oxysulfide crystal useful for a solar cell or the like, and a method for producing the thin film by a so-called spray pyrolysis method.

[0002]

2. Description of the Related Art As a semiconductor material used for a light absorbing layer of a solar cell, silicon has been mainly used so far, and gallium arsenide, cadmium telluride, copper indium selenide and the like are also used. Have been.

However, silicon has a small light absorption coefficient because it is an indirect transition type, and requires a thickness of about 100 μm to efficiently convert sunlight into electricity. Therefore, when a solar cell is obtained using silicon, a relatively large amount of material is required, and in addition, the supply amount of high-purity silicon is limited.

On the other hand, a technology has been developed which can efficiently convert sunlight into electricity even when the thickness is reduced by using amorphous silicon. However, even in this case, there is a problem that the supply amount of amorphous silicon is limited. .

Further, conventional semiconductor materials other than silicon contain toxic elements such as arsenic, cadmium, and selenium, and none of them are sufficient in terms of material toxicity.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to provide a semiconductor which is relatively easy to supply, has no limit on the amount of supply, and contains no toxic elements. It is an object of the present invention to provide a material and a method capable of efficiently and conveniently producing it.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, heated a solution containing a specific concentration of tin dichloride and thiourea to a specific temperature range. By supplying it on a substrate, a film containing a novel tin oxysulfide crystal was obtained, and it was found that the above object was achieved by such a tin oxysulfide film, and the present invention was completed.

That is, the present invention provides the following general formula: Sn ₂ O _x S _y (1) (where x and y are respectively x = 0.5 to 1.5,
y = 0.5 to 1.5 and x + y = 1 to 3) are included in the tin oxysulfide film.

The present invention also relates to a method for preparing a substrate heated to 175 to 425 ° C., comprising the steps of: adding 0.001 to 0.12 M tin dichloride; By supplying a solution containing the following, on the substrate, the following general formula: Sn ₂ O _x S _y (1) (where x and y are respectively x = 0.5 to 1.5,
a film satisfying the conditions of y = 0.5 to 1.5 and x + y = 1 to 3), and forming a film containing a tin oxysulfide crystal represented by the following formula: It is in.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

First, the tin oxysulfide film of the present invention will be described. The tin oxysulfide film of the present invention is obtained for the first time by the production method of the present invention described later, and contains a tin oxysulfide crystal represented by the following general formula: Sn ₂ O _x S _y (1). Such a tin oxysulfide crystal is composed of a tin atom, an oxygen atom and a sulfur atom, and more specifically, a tin atom forming a face-centered cubic structure as shown in FIG. Are cubic crystals formed by oxygen and sulfur atoms penetrating into gap positions (indicated by x in the figure). Tin atom,
Since the supply of oxygen and sulfur atoms is relatively easy, the supply amount of tin oxysulfide crystals is not limited. Moreover, tin atom, oxygen atom and sulfur atom are all non-toxic, and tin oxysulfide crystals have no toxicity problem.

In the tin oxysulfide crystal according to the present invention, oxygen atoms and sulfur atoms are 0.5 to 1.5 atoms (x) and 0.5 to 1.5 atoms (x) with respect to two tin atoms, respectively.
1.5 atoms (y), preferably from 0.9 to
1.1 atoms (x) and 0.9 to 1.1 atoms (y). If the ratio of oxygen atoms is higher than the upper limit, SnO ₂ tends to be mixed, while if the ratio of sulfur atoms is higher than the upper limit, SnS tends to be mixed.

The total number of oxygen atoms and sulfur atoms (x + y) is ideally two for two tin atoms, but lattice defects may be present, and the total number of atoms (x + y) x + y) is 1 to 3 atoms per 2 tin atoms;
Preferably it is 1.8 to 2.2 atoms. If the total number of atoms is higher than the upper limit or lower than the lower limit, the crystallinity tends to decrease.

One face-centered cubic lattice shown in FIG. 1 has a lattice constant of about 5.8 angstroms. As shown in FIG. 1, a tin oxysulfide crystal is composed of eight such face-centered cubic lattices. Have been. That is, the tin oxysulfide crystal is a cubic crystal having a lattice constant of about 11.6 angstroms.

The tin oxysulfide film of the present invention contains the above-mentioned tin oxysulfide crystal, and is composed of a film composed of only the tin oxysulfide crystal and a tin compound other than the tin oxysulfide crystal (tin oxide, tin oxide, etc.).
In addition to a pure tin oxysulfide film substantially free of tin chloride, stannous sulfide, and stannic sulfide, etc., a film mainly containing tin oxysulfide crystals is also included. Note that, as the film containing tin oxysulfide crystals as a main component, the number of moles of tin oxysulfide in the film is preferably equal to or more than the total number of moles of tin compounds other than tin oxysulfide, and the content of tin oxysulfide is preferably About 75
It is particularly preferred that it is at least mol%. Examples of tin compounds other than tin oxysulfide that can be contained in the tin oxysulfide film include tin oxide, tin chloride, stannous sulfide, and stannic sulfide.

The thickness of the tin oxysulfide film of the present invention is not particularly limited, and may be, for example, a thin film having a thickness of 0.1 to 10 μm.

Next, a method for producing the tin oxysulfide film of the present invention will be described. In the method for producing a tin oxysulfide film of the present invention, first, a solution containing tin dichloride and thiourea is prepared. The tin dichloride according to the present invention is tin (II) chloride represented by the chemical formula: SnCl _2, which usually exists as a dihydrate crystal. The thiourea according to the present invention is a compound represented by the chemical formula: NH ₂ C (＝ S) NH ₂ .

When such tin dichloride is used in combination with thiourea, and the tin dichloride concentration is adjusted to a relatively low concentration as described later and supplied onto a substrate heated to a predetermined temperature,
Thiourea is thermally decomposed into hydrogen sulfide, and sulfur ions are combined with tin ions. At the same time, oxygen ions in the atmosphere react with tin ions to cause oxidation, and as a result, tin oxysulfide crystals are efficiently obtained.

The solvent used in the present invention may be any solvent capable of dissolving tin dichloride and thiourea and leaving no residue on the substrate after being thermally decomposed. Water is preferably used. No.

[0020] The concentration of tin dichloride in the solution according to the present invention must be in the range of 0.001 to 0.12M. If the concentration of tin dichloride is less than 0.001M, the number of sprays required to obtain a tin oxysulfide film having a desired thickness becomes too large to be practical.
If it exceeds 12 M, appropriate oxidation does not occur on the substrate, so that tin oxysulfide crystals cannot be obtained. Further, the concentration of such tin dichloride is preferably from 0.005 to 0.1M, and particularly preferably from 0.01M to less than 0.08M. If the concentration of tin dichloride is less than the above lower limit, the number of sprays required to obtain a tin oxysulfide film having a desired thickness tends to be too large to be practical, while if it exceeds the above upper limit, the tin oxychloride crystal The temperature range in which can be obtained particularly efficiently tends to be narrow.

The concentration of thiourea in the solution according to the present invention must be in the range of 0.1 to 10 times the molar ratio of tin dichloride in the solution, and is 0.5 to 2 times the molar ratio of tin dichloride in the solution. Is particularly preferable, and it is particularly preferable that the molar ratio is in the range of 1 to 2 times. If the molar ratio of thiourea to tin dichloride is less than 0.1, SnO ₂ will be the main component, while if the molar ratio exceeds 10, crystallinity will decrease. The concentration of such thiourea is 0.001 to 0.12M.
Is preferable, and particularly preferably 0.005 to 0.1M. If the concentration of thiourea is lower than the lower limit, SnO ₂ tends to be mixed, and if the concentration exceeds the upper limit, crystallinity tends to decrease.

Further, the solution according to the present invention contains 0.1.
It is preferable that an acid of 01 to 10% by weight is further contained. The addition of such an acid tends to sufficiently prevent the formation of a precipitate (tin oxychloride) due to the hydrolysis of tin dichloride. Examples of such acids include mineral acids such as hydrochloric acid and organic acids such as acetic acid. However, the use of sulfuric acid is not preferred because tin compounds other than tin oxysulfide tend to be mainly produced.

Next, in the method for producing a tin oxysulfide film of the present invention, the solution containing tin dichloride and thiourea is supplied onto a substrate heated to 175 to 425 ° C., preferably 225 to 425 ° C. I do. When the temperature of the substrate exceeds 425 ° C., tin is oxidized on the substrate and tin oxide (Sn
O ₂₎ and will become in the other, oxysulfide tin is not generated because the thiourea is not thermally decomposed on the substrate at a temperature of the substrate is less than 175 ° C..

When the concentration of tin dichloride in the solution is relatively high (in the range of 0.03 to 0.12 M), the concentration of tin dichloride and the temperature of the heated substrate are expressed by the following formula: T> 2500C + 100 (2) (wherein C represents the concentration [M] of tin dichloride in the solution, and T represents the temperature [° C.] of the heated substrate). When the concentration of tin dichloride is relatively high, the lower limit of the temperature at which the tin oxysulfide crystals are efficiently generated tends to increase with the increase, so that the relatively low temperature that does not satisfy the condition of the above formula (2) is obtained. In the region, tin oxysulfide crystals tend not to be efficiently obtained.

In the method of the present invention, when the solution is supplied, it is preferable that the temperature of the substrate heated within the above-mentioned temperature range is not temporarily lowered by 10 ° C. or more. Therefore, it is preferable to repeat intermittently spraying onto the substrate a plurality of times the solution, spraying amount per one time is preferably 0.01~1.0cm ³ / 10cm ^2. Further, the total amount of the solution supplied onto the substrate is appropriately selected according to a desired thickness of the tin oxysulfide film.

The above-mentioned temperature of the substrate means the temperature of the central portion of the substrate surface (the portion where the tin oxysulfide film is to be formed) at the moment when the supply of the solution is started. It does not indicate a falling temperature.

In the method of the present invention, the precipitate (tin oxychloride) formed in the solution by the hydrolysis of tin dichloride is completely removed by filtration immediately before the solution is supplied onto the heated substrate. Is preferred. By doing so, the uniformity of the film tends to be improved.

Further, the atmosphere for supplying the above-mentioned solution onto the heated substrate may be an atmosphere containing oxygen, such as air, a mixed gas atmosphere of an inert gas such as a nitrogen gas or a rare gas and an oxygen gas. It may be.

According to the method of the present invention, a tin oxysulfide film can be formed on various substrates. Therefore, the substrate that can be used in the present invention is not particularly limited as long as it can withstand heating to the above-mentioned temperature range. For example, a glass substrate, a cadmium sulfide substrate, an indium tin oxide substrate, a tin oxide substrate, a zinc oxide substrate And a zinc sulfide substrate.

According to the method of the present invention, a tin oxysulfide film containing the above-mentioned novel tin oxysulfide crystal can be efficiently and simply manufactured.

The apparatus for carrying out the method of the present invention is not particularly limited, and a two-fluid spray gun or the like may be appropriately used. One preferred embodiment of the spray pyrolysis apparatus will be described below. As shown in FIG. 2, the apparatus of the present embodiment includes a solution supply unit 1, a carrier gas supply unit 2, an atomizer 3, a substrate 4, and a substrate holding unit 6 having a built-in heater 5. I have. The solution supply unit 1 includes a solution tank 8 for storing the raw material solution 7, a pump 9, a flow meter 10, and a pipe 11, and the carrier gas supply unit 2 generates and supplies a compressed gas. The apparatus includes a device 12, a flow meter 13, and a pipe 14.

The atomizer 3 is a two-fluid spray gun. The atomizer 3 atomizes the solution supplied from the solution supply unit 1 by a gas (for example, compressed air) supplied from the carrier gas supply unit 2. Substrate 4 heated to temperature
The tin oxysulfide film 16 is formed by spraying the solution 15 atomized above. A sheath-type thermocouple (not shown) is provided on the side surface of the substrate 4, and the temperature at the center of the surface of the substrate 4 is calculated from the display temperature of the thermocouple based on a calibration curve obtained in advance. And a PID controller (not shown) so that the temperature becomes a predetermined value.
The heater 5 is controlled by the control. Further, the distance from the spray port of the atomizer 3 to the substrate 4 is set to, for example, 20 to 50 cm, and the atomization pressure is set to, for example, 0.05 to 0.5 MPa.

[0033]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the following examples.

Example 1 The concentration of tin dichloride was 0.04M and the concentration of thiourea was 0.0
An aqueous solution was obtained by dissolving tin dichloride and thiourea in water so as to obtain 4M, and 0.4% by weight of hydrochloric acid was added to the aqueous solution to obtain a raw material solution. Then, using a spray pyrolysis apparatus shown in FIG. 2, a glass substrate (alkali-free glass, manufactured by Corning, trade name: Corning # 705) under the following conditions
9) The above raw material solution was sprayed thereon.

(Manufacturing conditions) Substrate temperature: 300 ° C. Spray solution amount: 0.25 cm ³ / spray frequency: 50 times Spray interval: The next spraying is performed when the temporary decrease in substrate temperature due to spraying is recovered. (About 10 seconds) Distance from spray port to substrate: 40 cm Atomization pressure: 0.25 MPa Carrier gas: compressed air.

As a result, 25 mm × 2 mm
A thin film having a thickness of about 0.5 μm was formed in a region of 5 mm.
When the X-ray diffraction pattern of the obtained thin film was measured using an X-ray diffractometer (trade name: RINT-1100, manufactured by Rigaku Corporation), a diffraction pattern as shown in FIG. 3 was observed.

When the obtained X-ray diffraction pattern was compared with a conventionally known X-ray diffraction pattern of a tin compound, there was no coincidence. Therefore, based on the obtained X-ray diffraction pattern, the crystal structure was determined by the following procedure.

(Determination of Crystal Structure) First, the diffraction angle 2θ _n (n is the number assigned to the diffraction line) of the X-ray diffraction line (diffraction peak) was read. Table 1 shows the obtained results. Then, (sin θ _n ) ² was calculated. Next, assuming that the crystal system is a cubic system (a structure in which cubes are arranged), the following equation: A × m = (sin θ _n ) ² (3) (where A is a constant and m is a plane index) Are the values of A and m that satisfy the relationship: If these are found, the crystal system is cubic, otherwise it is another crystal system. In this example, since the values of A and m satisfying the above relationship were found, it was found to be cubic.

Next, using the above A, the following equation: a ₀ = 2 × (A / λ) ^0.5 (4) (where a ₀ is a lattice constant (length of one side of a cube), and λ Is the X-ray wavelength (1.54 Å), and the lattice constant (a ₀ ) is obtained.
1.6 Å.

Next, the surface index (hkl) of the n-th diffraction line and the value of m corresponding to the n-th diffraction line have the following relationship: m = h ² + k ² + l ² (5) , The values of h, k, and l were determined based on this. Table 1 shows the obtained results. For example, when m = 16, (hkl) = (400) is uniquely determined, but when m = 17, (hkl) = (41)
0) and (322), and one of them was not determined.

Further, the spatial grating is determined by which value of the diffraction line m exists, and in this embodiment, m =
.. Were present, it was found that they were simple cubic lattices.

[0042]

[Table 1]

The above is the result derived based on the angle of the diffraction line. Next, the analysis was performed based on the intensity of the diffraction line.

As is clear from the data shown in Table 1,
The planes showing strong diffraction are (222), (400), (44)
0) and (622). These aspects are (11)
1), (200), (220), and (311) are twice as large as the surface indices, and (111), (200), (22)
0) and (311) are planes where diffraction occurs in the face-centered cubic lattice. Therefore, atoms that strongly diffract X-rays, that is, Sn atoms with a large atomic number, have a plane of a ₀ /2=5.8 angstroms. It was found that a heart cubic structure was formed.

Next, the chemical composition of the film obtained in this example was examined by a Rutherford backscattering method using a Rutherford backscattering measuring device (trade name: AN-2500, manufactured by Nisshin Hibolrage Co., Ltd.). , the film obtained in this embodiment comprises a tin atom, an oxygen atom and a sulfur atom as a main component, the ratio thereof is 2: 1: close to 1, Sn ₂ O
It was found to be tin oxysulfide described as S.

In the case of a Cu crystal having a simple face-centered cubic structure, for example, as shown in FIG. 4A, the diffraction intensity of the (111) plane is larger than that of the (200) plane (see Table 1). On the other hand, for example, a NiO crystal (salt type) as shown in FIG.
Then, the intensity ratio of the (200) plane is large (see Table 1). This is due to the fact that the atom enters the position of x in FIG.
This is because the atomic density of the (00) plane has increased.

In the crystal obtained in this example, (4
Since the diffraction intensity ratio of the (00) plane is as large as that of the NiO crystal (see Table 1), as shown in FIG. 1, the gap of the face-centered cubic structure formed by Sn atoms (indicated by ○ in the figure) is formed. It was found that O atoms and S atoms were present at the positions (indicated by x in the figure). And this is because the positive element Sn
The result was consistent with the result of RBS (Rutherford backscattering analysis) that the ratio of the atom to the sum of the O and S atoms as negative elements was about 1: 1.

That is, as shown in FIG. 1, O and S atoms have 32 non-equivalent gap positions in the lattice having a lattice constant (a ₀ ) of 11.6 angstroms (indicated by X in the figure). ) Turned out to be regularly arranged.

As described above, the crystals obtained in this example are:
It was a tin oxysulfide crystal different from the tin compounds (tin sulfide, tin oxide, etc.) reported so far. Further, since all the diffraction lines included in the X-ray diffraction pattern of the film containing this crystal were derived from the crystal structure specified above, this film was not a known mixture of tin sulfide and tin oxide. It turned out to be a specific compound having one crystal structure, namely tin oxysulfide.

(Evaluation of Electric Characteristics) Next, the electric characteristics of the obtained thin film were measured as follows. That is, spectral transmittance was measured using a spectrophotometer (trade name: V570, manufactured by JASCO Corporation) to determine the light absorption coefficient (α) of the thin film. The results obtained are shown in FIG. FIG. 5 shows that the absorption coefficient is 10 ^{4 in the} wavelength region shorter than about 700 nm.
cm ⁻¹ or more, indicating that the absorption coefficient was large.

Next, FIG. 6 is a graph in which the square root of the value obtained by multiplying the absorption coefficient (α) and the photon energy (hν) obtained in FIG. 5 is plotted against the photon energy (hν). Since the graph shown in FIG. 6 became a straight line having a bending point in the middle, it was found that the tin oxysulfide was an indirect transition type. Also, the energy at which bending occurs is E ₁ =
1.36 eV, E ₂ = 1.64 eV, band gap E _g = (E ₁ + E ₂ ) /2=1.50 eV, and phonon energy E _f = (E ₂ −E ₁ ) /2=0.14 eV. It turned out to be.

As described above, the tin oxysulfide film containing the tin oxysulfide crystal obtained by the present invention has a large light absorption coefficient and a band gap of 1.50 eV, so that it is very suitable for a light absorption film of a solar cell. It has been found that it has suitable characteristics.

Comparative Example 1 A thin film was formed on a glass substrate in the same manner as in Example 1 except that the substrate temperature was changed to 150 ° C. The X-ray diffraction pattern of the obtained thin film was measured in the same manner as in Example 1. As shown in FIG. 3, no diffraction peak corresponding to tin oxysulfide was observed, and tin dichloride (SnCl ₂ ) and thione Urea (N ₂
Only the H ₄ CS) diffraction peak was observed. That is,
When the substrate temperature was 150 ° C., the raw material did not thermally decompose, and no tin oxysulfide was generated.

Comparative Example 2 A thin film was formed on a glass substrate in the same manner as in Example 1 except that the substrate temperature was changed to 450 ° C. When the X-ray diffraction pattern of the obtained thin film was measured in the same manner as in Example 1, as shown in FIG. 2, no diffraction peak corresponding to tin oxysulfide was observed, and the diffraction peak of tin oxide (SnO ₂ ) was observed. Only observed. That is, when the substrate temperature was 450 ° C., the oxidation was promoted to form a tin oxide crystal phase, and no tin oxysulfide was generated.

Examples 2 to 21, Reference Examples 1 to 9 and Comparative Examples
3-7 A thin film was formed on a glass substrate in the same manner as in Example 1 except that the concentration of tin dichloride, the concentration of thiourea, the amount of hydrochloric acid added, and the substrate temperature were as shown in Tables 2 and 3, respectively.

When the X-ray diffraction pattern of each of the obtained thin films was measured in the same manner as in Example 1, the diffraction peaks shown in Tables 2 and 3 were observed. The evaluation (* 1) of the presence or absence of a diffraction peak corresponding to tin oxysulfide was indicated by "O" when such a peak was observed, and "-" when it was not observed. The evaluation of the presence or absence of diffraction peaks corresponding to tin compounds other than tin oxysulfide (tin oxide, tin chloride, stannous sulfide, etc.) (* 2) indicates that such a peak was observed as “○”. The case not performed was indicated as "-".

Further, a comprehensive evaluation (* 3) of each thin film was performed based on the evaluation results of the X-ray diffraction pattern according to the following criteria. Tables 2 and 3 show the obtained results.

(Criteria for Comprehensive Evaluation) ：: When only the diffraction peak of tin oxysulfide was observed Δ: When the diffraction peak of tin oxysulfide was observed together with the diffraction peak of a tin compound other than tin oxysulfide ×: Oxygen When no diffraction peak of tin sulfide was observed.

[0059]

[Table 2]

[0060]

[Table 3]

FIG. 7 shows the relationship between the overall evaluation of the thin films obtained in Examples 1 to 21, Reference Examples 1 to 9 and Comparative Examples 1 to 7 and the concentration of tin dichloride and the substrate temperature. Note that the dashed line shown in FIG. 7 is a straight line corresponding to the above equation (2).

From the results shown in FIG.
No tin oxysulfide is generated at ℃, substrate temperature is 450 ℃
However, no tin oxysulfide was produced. On the other hand, when the substrate temperature is 200 to 400 ° C., a thin film containing tin oxysulfide is generated. In particular, when the substrate temperature is 250 to 400 ° C. and the condition of the above formula (2) is satisfied, tin oxysulfide is used as a tin compound. Only a thin film containing only was produced.

The chemical compositions of the films obtained in Examples 4, 7, 8 and 11 were examined by the Rutherford backscattering method in the same manner as in Example 1. Table 4 shows the results. As is clear from the results shown in Table 4, the films obtained in these examples contain tin, oxygen, and sulfur atoms as main components, and the ratio thereof is 2: 0.37 to 1.14: 1 to
It was found to be in the range of 1.59.

[0064]

[Table 4]

Examples 22 to 24 A thin film was formed on a glass substrate in the same manner as in Example 1 except that the concentration of tin dichloride, the concentration of thiourea, the acid used, the amount of acid added and the substrate temperature were as shown in Table 5, respectively. Was formed.

When the X-ray diffraction pattern of each of the obtained thin films was measured in the same manner as in Example 1, the diffraction peaks shown in Table 5 were observed. The overall evaluation of each thin film was performed in the same manner as in Example 1 based on the evaluation result of the X-ray diffraction pattern. Table 5 shows the obtained results.

[0067]

[Table 5]

As is evident from the results of Examples 22 to 24 shown in Table 5, the acid used in the present invention may be acetic acid in addition to hydrochloric acid. A thin film containing only tin sulfide was produced. In addition, when the acid was added, the uniformity of the film was improved as compared with the case where the acid was not added.

Examples 25 to 28 Thin films were formed on glass substrates in the same manner as in Example 1 except that the concentration of tin dichloride, the concentration of thiourea, the amount of hydrochloric acid added and the substrate temperature were as shown in Table 6, respectively.

When the X-ray diffraction pattern of each of the obtained thin films was measured in the same manner as in Example 1, the diffraction peaks shown in Table 6 were observed. The overall evaluation of each thin film was performed in the same manner as in Example 1 based on the evaluation result of the X-ray diffraction pattern. Table 6 shows the obtained results.

[0071]

[Table 6]

As is clear from the results of Examples 25 to 28 shown in Table 6, tin oxysulfide was contained as a tin compound even when the molar ratio of thiourea to tin dichloride was 0.25 to 2.0. In particular, the above-mentioned molar ratio is 1.0
In the case of 2.0, a thin film containing only tin oxysulfide as a tin compound was produced.

Example 29 A thin film was formed on a glass substrate in the same manner as in Example 1 except that the thiourea concentration was 0.032 M, the amount of hydrochloric acid was 1.0% by weight, and a glass substrate with ITO was used as the substrate. Formed.

Then, the obtained thin film was exposed to air in air.
After heat treatment at 00 ° C. for 10 minutes, an electrode was formed on this film. When the obtained laminate was exposed to sunlight,
At a voltage of about 200 mV between the ITO and the electrode, about 1 mA /
cm ² of current flowed. From this, it was found that the tin oxysulfide film obtained in this example forms a semiconductor junction with ITO and functions as a semiconductor.

[0075]

As described above, the tin oxysulfide film containing the tin oxysulfide crystal of the present invention is a semiconductor material which is relatively easy to supply, has no limit on the supply amount, and does not contain any toxic elements. is there. Therefore, according to the present invention, it is possible to provide an excellent semiconductor material that can cope with an increase in the production volume of solar cells in the future and has no problem of containing toxic elements.

Further, according to the production method of the present invention, it is possible to efficiently and easily produce the thin film composed of only the tin oxysulfide crystal of the present invention or the thin film containing tin oxysulfide crystal as a main component. . Therefore, according to the method for producing a tin oxysulfide film of the present invention, a tin oxysulfide thin film useful for a solar cell or the like can be efficiently and inexpensively produced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a crystal structure of a tin oxysulfide crystal according to the present invention.

FIG. 2 is a schematic diagram showing one embodiment of a spray pyrolysis apparatus suitable for carrying out the method of the present invention.

FIG. 3 is a graph showing X-ray diffraction patterns of thin films obtained in Example 1, Comparative Examples 1 and 2, respectively.

FIG. 4A is a schematic diagram illustrating a crystal structure of a copper crystal, and FIG. 4B is a schematic diagram illustrating a crystal structure of a nickel oxide crystal.

FIG. 5 is a graph showing the relationship between the light absorption coefficient and the wavelength of the thin film obtained in Example 1.

FIG. 6 is a graph plotting the square root of the value obtained by multiplying the absorption coefficient (α) and the photon energy (hν) with respect to the photon energy (hν) for the thin film obtained in Example 1.

FIG. 7 is a graph showing the relationship between tin dichloride concentration and substrate temperature and evaluation of the obtained thin film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solution supply part, 2 ... Carrier gas supply part, 3 ... Atomizer, 4 ... Substrate, 5 ... Heater, 6 ... Substrate holding part, 7 ... Raw material solution, 8 ... Solution tank, 9 ... Pump, 10 ... Flow rate Total, 1
DESCRIPTION OF SYMBOLS 1 ... piping, 12 ... compressed gas generation / supply apparatus, 13 ... flow meter, 14 ... piping, 15 ... atomized solution, 16 ... tin oxysulfide film.

Claims (5)

[Claims] 1. The following general formula: Sn ₂ O _x S _y (1) (where x and y are respectively x = 0.5 to 1.5,
a tin oxysulfide crystal represented by the following formula: y = 0.5 to 1.5 and x + y = 1 to 3). 2. The tin oxysulfide film according to claim 1, wherein the tin oxysulfide crystal is a cubic crystal having a lattice constant of 11.6 angstroms. 3. On a substrate heated to 175 to 425 ° C.,
By supplying a solution containing 0.001 to 0.12 M tin dichloride and 0.1 to 10 times the molar ratio of thiourea to the tin dichloride, the following general formula: Sn ₂ O is formed on the substrate. _{xS y} (1) (where x and y are x = 0.5 to 1.5, respectively)
a film satisfying the conditions of y = 0.5 to 1.5 and x + y = 1 to 3), and forming a film containing a tin oxysulfide crystal represented by the following formula: . 4. The concentration of tin dichloride in the solution and the temperature of the heated substrate are defined by the following formula: T> 2500C + 100 (2) (where C is the concentration of tin dichloride in the solution [M And T represents the temperature of the heated substrate [° C.]). 5. The method according to claim 3, wherein the solution further contains 0.01 to 10% by weight of an acid.