JPH07183550A - Amorphous photoelectric conversion device - Google Patents

Abstract

PURPOSE:To enhance an amorphous photoelectric conversion device in conversion efficiency, especially fill factor, and open and voltage by a method wherein a first and a second substantially intrinsic semiconductor thin film are formed of amorphous silicon hydride. CONSTITUTION:An amorphous semiconductor solar cell structure is basically formed of a blue glass plate on which tin oxide is deposited. That is, a glass plate/tin oxide is made to serve as a substrate 110, and a P-type semiconductor layer 112, an I-type semiconductor layer 113, an N-type semiconductor layer 114, a P-type semiconductor layer 115, an I-type semiconductor layer 116, and an N-type semiconductor layer 117 are successively laminated. It is preferable for a second electrode layer 111 that a substantially intrinsic semiconductor thin film on which sunlight is incident contains 15 to 50atom% of combined hydrogen, also it is preferable that a second substantially intrinsic semiconductor thin film contains 0.5 to 15atom% of combined hydrogen, and a first and a second semiconductor layer, a first and a second N-type semiconductor layer, and a first and a second electrode are so arranged as to conform to the above constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the performance of amorphous silicon solar cells, and more particularly to a technique for producing amorphous silicon solar cells with high conversion efficiency and high reliability.

[0002]

2. Description of the Related Art Amorphous silicon solar cells have already been put to practical use as a low-output energy source for driving calculators and watches. However, as an energy supply source with a large output used for electric power, it has not yet reached a satisfactory performance, and various studies have been carried out with the aim of improving the performance. The photoelectric conversion efficiency of a solar cell is represented by the product of open-circuit voltage, short-circuit photocurrent and fill factor.
It has been reported that the results are close to the theoretically predicted values estimated from the physical properties of the specified amorphous semiconductor, for example, a short-circuit photocurrent of 19 mA / cm ² and a fill factor of 0.78. Further, the open-end voltage is close to the voltage estimated when the material properties of each layer forming the photoelectric conversion element are taken into consideration. Based on the current situation and theoretical results, we aimed at power applications,
In order to develop an amorphous photoelectric conversion device with high conversion efficiency and high reliability, the first problem is to bring the defects in each constituent layer closer to a crystalline material. However, as a result of various investigations, the development of technology for extremely reducing material defects
Progress is saturating.

On the other hand, as a photoelectric conversion element structure which is expected to have higher conversion efficiency, there is a tandem type photoelectric conversion element structure in which elements having intrinsic semiconductor layers having different band gaps are monolithically and continuously laminated. As a photoelectric conversion element structure which is advantageous and effective for a thin film type photoelectric conversion element, research has been conducted so far. This tandem-type laminated structure photoelectric conversion element was found to be improved in light resistance because the intrinsic semiconductor layer can be designed to be relatively thin, and the structure of the photoelectric conversion element with high conversion efficiency and high reliability was found. As, many studies have been reported.

In an amorphous semiconductor, in order to change the band gap, a different element is usually added, and a trial similar to that of a so-called compound semiconductor which is generally called is performed. It is applied to the intrinsic semiconductor layer of the tandem type laminated structure photoelectric conversion device described above.
A wide bandgap material is added to an amorphous silicon semiconductor by adding a carbon atom or a nitrogen atom, and a narrow bandgap material is manufactured by adding a tin atom or a germanium atom. However, when a few% to several dozen% of different kinds of atoms are added to a material in which silicon atoms are a matrix, many defects are generated in the material. Various film forming conditions and film forming methods have been investigated in order to reduce the generated defect amount as much as possible, and the defect amount has been gradually reduced. The occurrence of defects is unavoidable, widening the band gap,
The defects in the narrowed material are large and unavoidable. Therefore, in the device in which these materials are applied to the tandem type laminated structure photoelectric conversion device, the expected open-end voltage, fill factor and short-circuit photocurrent cannot be obtained from the bandgap, and the expected conversion efficiency is not obtained. Well below. Therefore, it has been difficult to solve these problems in the amorphous silicon material of mixed system of different elements.

[0005]

DISCLOSURE OF THE INVENTION The present invention improves the quality of different bandgap materials used in a tandem type laminated structure photoelectric conversion device, and improves the conversion efficiency of an amorphous photoelectric conversion device, particularly the fill factor and the open end. The purpose is to increase the voltage.

[0006]

As described above, in a conventional amorphous semiconductor, a different element is added in order to change the band gap, and a trial similar to that of a generally called compound semiconductor is performed. The different element-added material is applied to the intrinsic semiconductor layer of the tandem type laminated structure photoelectric conversion device described above. A wide bandgap material is added to an amorphous silicon semiconductor by adding a carbon atom or a nitrogen atom, and a narrow bandgap material is manufactured by adding a tin atom or a germanium atom. However, when a few% to several dozen% of different kinds of atoms are added to a material in which silicon atoms are a matrix, many defects are generated in the material. Various film forming conditions and film forming methods have been investigated in order to reduce the generated defect amount as much as possible, and the defect amount has been gradually reduced. Inevitably, the defects of (2) are inevitable, and the defects of the material having the widened or narrowed band gap are large and unavoidable. Therefore, in the device in which these materials are applied to the tandem type laminated structure photoelectric conversion device, the expected open-end voltage, fill factor and short-circuit photocurrent cannot be obtained from the bandgap, and the expected conversion efficiency is not obtained. Well below. Therefore, it has been difficult to solve these problems in the amorphous silicon material of mixed system of different elements.

The inventors of the present invention, therefore, have developed a semiconductor thin film in which the band gap of a hydrogenated amorphous silicon semiconductor is controlled by changing the bonding amount of hydrogen atoms without using any different element, and a tandem type laminated structure photoelectric conversion film is formed. An amorphous photoelectric conversion element with improved fill factor, open-end voltage and short-circuit photocurrent could be produced only by applying it to the intrinsic semiconductor layer of the conversion element.

That is, the present invention comprises a substrate, a first electrode,
First p-type semiconductor thin film, first substantially intrinsic semiconductor thin film, first n-type semiconductor thin film, second p-type semiconductor thin film, second substantially intrinsic semiconductor thin film, second n -Type semiconductor thin film, in the amorphous solar cell formed by stacking the second electrode structure, the first substantially intrinsic semiconductor thin film and the second substantially intrinsic semiconductor thin film is hydrogen. An amorphous photoelectric conversion device, characterized in that the bound hydrogen content of the first substantially intrinsic semiconductor thin film is 15 to 50 atomic%. Photoelectric conversion element, and an amorphous photoelectric conversion element in which the amount of bound hydrogen in the second substantially intrinsic semiconductor thin film is 0.5 to 15 atomic%, and the second substantial Amount of bound hydrogen in a semiconductor film that is intrinsically 0.5 to 15 atomic%
And an amorphous photoelectric conversion device in which the amount of bound hydrogen in the first substantially intrinsic semiconductor thin film is 15 to 50 atom%.

The first and second substantially intrinsic semiconductor thin films referred to in the present invention are silicon hydride thin films, which are films containing no different elements other than silicon, hydrogen and fluorine. Further, the different elements not included in the present thin film are, for example, germanium in a silicon germanium hydride thin film, tin in a silicon hydride thin film, carbon in a hydrogenated silicon carbon thin film, nitrogen in a hydrogenated silicon nitride thin film, and hydrogenated oxidation. For example, oxygen in silicon. However, the content of the different element not contained in the thin film is not particularly limited in carrying out the present invention as long as it is an amount that does not affect the band gap of the thin film, and is included in the thin film. It should be noted that this is no problem. In particular, when forming a silicon hydride thin film, rather than intentionally introducing a gas or the like and adding a different element, impurities such as oxygen and nitrogen that are naturally mixed are not included in the different element here. Is not included, and the content of the different element is 2 atomic% or less. The relationship between the content of these and the optical band gap is shown in FIG. When the content is 2 atomic% or less, there is no change in the forbidden band and there is no influence, so it is clear that it may be contained as a different element.

The term "substantially intrinsic semiconductor thin film" as used herein means that which forms a photoactive region of an amorphous silicon solar cell. These intrinsic semiconductor thin films are easily formed from a compound having silicon in the molecule by applying plasma CVD (chemical vapor deposition) method, optical CVD, or thermal CVD (chemical vapor deposition) method.

The formation of the intrinsic semiconductor thin film by the CVD method using plasma will be specifically described. The plasma can be generated by applying a DC or AC voltage to the plasma generating electrode, and an AC frequency of 20 kHz to 100 MHz can be used. In particular, the commercial power frequencies of 50 kHz and 60 kHz and the radio frequency of 13.56 MHz, which is recognized by the Radio Law, are preferred frequencies for use. However, this frequency for plasma generation (including direct current) does not hinder the implementation of the present invention. The power to generate plasma is 0.001 mW / cm ² to 100 W / cm in terms of power density.
^{Use 2} .

The source gas is a silane compound represented by the general formula SinH _2n + ₂ (n; a positive integer of 1 or more), SiH _n X _4-n (X; halogen atom is a fluorine atom, chlorine atom, n; A positive integer from 1 to 4), Si ₂ H _n X _{6 -n} (X; halogen atom is a fluorine atom, chlorine atom, n; a positive integer from 1 to 6) The specific source gases that are easy to use industrially are monosilane (SiH ₄ ), disilane (S
i ₂ H ₆ ), trisilane (Si ₃ H ₈ ), silicon tetrafluoride (SiF ₄ ), difluorosilane (SiH ₂ F ₂ ), trifluorosilane (SiHF ₃ ).
, Monofluorosilane (SiH ₃ F) and hexafluorodisilane (Si ₂ F ₆ ).

These source gases may be diluted with an inert gas (argon, helium, etc.) or hydrogen gas before use. The diluted source gas is 1 to 100% expressed by volume concentration. The raw material gas is introduced through a gas flow meter, and the flow rate is 1 cc / min to 1000 cc / min. The forming temperature is 50 to 400 ° C, preferably 50 to 350 ° C, and the forming pressure is 0.01 to 100 torr, preferably 0.03 to 1.
Done at 5 Torr.

In addition to the plasma CVD method, photo CVD
The method and the thermal CVD method can also be used for forming the substantially intrinsic semiconductor thin film, and are not particularly limited in carrying out the present invention.

The thickness of the substantially intrinsic semiconductor thin film is
The first substantially intrinsic semiconductor thin film has a thickness of about 10 to 200 nm, and the second substantially intrinsic semiconductor thin film has a thickness of 100 to 1000 nm.
It is about nm. Regarding the substantially intrinsic semiconductor thin film, the amount of bound hydrogen in the first substantially intrinsic semiconductor thin film is 1
5 to 50 atom%, preferably 20 to 50 atom%.
The amount of bound hydrogen in the second substantially intrinsic semiconductor thin film is 0.5 to 15 atomic%, preferably 3 to 15 atomic%.

The semiconductor thin film according to the present invention is
It is an amorphous semiconductor thin film, and is a thin film that does not contain different elements other than silicon atoms, hydrogen atoms, and fluorine atoms contained in this thin film. The different elements not included in the present thin film include, for example, germanium in a silicon germanium hydride thin film, tin in a silicon hydride thin film, carbon in a hydrogenated silicon carbon thin film, nitrogen in a silicon hydronitride thin film, and hydrogenated silicon oxide. Oxygen and the like. However, in particular, oxygen atoms, nitrogen atoms, and carbon atoms are atoms mixed as impurities in the process of forming the thin film, and the content of the different element is an amount that does not affect the band gap of the thin film. The present invention is not particularly limited to the practice of the present invention and may be included in the thin film. Specifically, the content of the different element is 2 atomic% or less. Regarding this, as mentioned above, also, a very small amount of diborane or phosphine is intentionally mixed at the same time as the source gas, and a boron atom or a phosphorus atom is minutely added to the substantially intrinsic semiconductor thin film. The combined use of the conventional techniques for forming an intrinsic semiconductor thin film does not hinder the effects of the present invention.

As the first and second p-type semiconductor thin films, p, which is usually used in amorphous silicon solar cells, is used.
Type amorphous silicon, amorphous silicon carbide, microcrystalline silicon, microcrystalline silicon carbide or carbon-containing microcrystalline silicon thin film, multi-layered film of amorphous silicon carbide with different carbon content, amorphous A multi-layer laminated film of silicon and amorphous carbon is preferably used. As a forming means, a plasma CVD (chemical vapor deposition) method or an optical CV method is used.
The D (chemical vapor deposition) method is used. As a raw material, silane, disilane, or trisilane is used as a silicon compound. Further, as a substance imparting p-type conductivity, diborane, trimethylboron, boron trifluoride and the like are preferable. Further, as the carbon-containing compound, methane,
Saturated hydrocarbons such as ethane, unsaturated hydrocarbons such as ethylene and acetylene, and alkylsilanes such as monomethylsilane and dimethylsilane are used. In these mixed gas,
If necessary, dilution with an inert gas such as helium or argon or hydrogen does not hinder the present invention. Rather, when forming a microcrystalline silicon thin film, diluting with a large amount of hydrogen is more preferable. As the forming conditions, the film thickness is 2 to 50 nm, particularly preferably 5 to 20 nm, the forming temperature is 50 to 400 ° C., preferably 50 to 250 ° C., particularly preferably 75 to 250 ° C., and the forming pressure is It is carried out at 0.01 to 5 Torr, preferably 0.03 to 1.5 Torr, and particularly preferably 0.035 to 1.0 Torr. Plasma C
When formed by VD, high frequency power 0.01mW / cm ² -10W /
It is done in the cm ² range. In particular, when forming a microcrystalline silicon-based thin film, it is preferable to perform the high frequency power in the range of 0.5 to 10 W / cm ² .

As the first and second n-type semiconductor thin films, n-type microcrystalline thin films and n-type amorphous thin films are effectively used. For these, an n-type microcrystalline silicon thin film, a carbon-containing microcrystalline silicon thin film, a microcrystalline silicon carbide thin film, an amorphous silicon thin film, an amorphous silicon carbon thin film, an amorphous silicon germane thin film, etc. can be effectively used. These n-type semiconductor thin films are compounds selected from compounds having silicon in the molecule, germane, compounds having germanium in the molecule such as silylgermane, hydrocarbon gas, etc. as raw materials appropriately selected according to the intended semiconductor thin film, Plasma CVD by mixing a group V compound of the periodic table, such as phosphine or arsine, and hydrogen.
It is easily formed by applying a (chemical vapor deposition) method or a photo CVD (chemical vapor deposition) method. Further, diluting the source gas with an inert gas such as helium or argon does not hinder the effect of the present invention. Rather, in the case of a microcrystalline silicon thin film, it is more preferable to dilute it with a large amount of hydrogen. The formation conditions are such that the formation temperature is 50 to 400 ° C, preferably 100 to 350 ° C, and the formation pressure is 0.01 to 5 Torr, preferably 0.03 to 1.5.
Done in Torr. When formed by plasma CVD,
High frequency power is performed in the range of 0.01 to 10 W / cm ² . In particular, when forming a microcrystalline silicon-based thin film, high frequency power 0.
It is preferably performed in the range of 1 to 10 W / cm ² . The film thickness of the n-type semiconductor thin film is 10 to 50 nm.

In the present invention, the raw material gas preferably used will be described with reference to more specific examples. For compounds having silicon in the molecule, monosilane,
Disilane, hydrogenated silicon such as trisilane, monomethylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, ethylsilane, hydrogenated silicon substituted with an alkyl group such as diethylsilane, vinylsilane, divinylsilane, trivinylsilane, vinyldisilane, divinyldisilane, It is possible to effectively use silicon hydride having a radically polymerizable unsaturated hydrocarbon group such as propenylsilane and ethenylsilane in the molecule, and silicon fluoride in which hydrogen of these silicon hydride is partially or completely substituted with fluorine. .

Hydrocarbon gases such as methane, ethane, propane, ethylene, propylene and acetylene are useful as specific examples of the hydrocarbon gas. These hydrocarbon gases are convenient to use when changing the optical band gap in the formation of carbon-containing microcrystalline silicon thin films, microcrystalline silicon carbide thin films, and the like. Further, for this purpose, a silicon hydride substituted with an alkyl group, a silicon hydride having an unsaturated hydrocarbon group capable of radical polymerization in the molecule, and a fluorine in which a part or all of the hydrogen of the silicon hydride is substituted with fluorine. Materials such as silicon oxide are also useful.

The substrate referred to in the present invention is a material having a shape and a shape that allows the solar cell formed on the substrate to have a shape capable of retaining its shape, a surface shape, and a temperature during formation. If so, there is no limitation in practicing the present invention. Specifically, borosilicate glass, soda lime glass, glass plates such as quartz glass, alumina, boron nitride,
Ceramic plate of silicon, metal plate of aluminum, stainless steel, chromium, titanium, molybdenum or the like, ceramic plate coated with these metals, glass plate, polyether sulfone, polyether ether ketone,
Sheets and films made of polymers such as polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polyamide, and polyimide, and plates obtained by coating the above metal with these are used.

The first electrode and the second electrode are a transparent electrode or a metal electrode, and the transparency thereof is not particularly limited, but it is necessary that sunlight be incident on the photovoltaic layer. For this reason, one of the electrodes, or both of the electrodes, needs to have a transparent electrode material selected so that sunlight can enter.

For the transparent electrode, a metal oxide such as tin oxide, indium oxide, zinc oxide, or a translucent metal can be effectively used. The metal electrode can be appropriately selected and used from metals such as aluminum, chromium, nickel-chromium, silver, gold and platinum.

The solar cell structure using the amorphous semiconductor described in detail in the present invention is, specifically, on a soda-lime glass plate,
It is based on the solar cell structure shown in FIG. 2 with tin oxide formed. In the figure, 110: substrate, 111: transparent electrode, 112: p-type semiconductor thin film, 113: i-type semiconductor thin film, 114: n-type semiconductor thin film, 115: p-type semiconductor thin film, 116: i-type semiconductor thin film, 117: n. -Type semiconductor thin film, 118: backside electrode. That is, using a glass plate / tin oxide as a substrate, p-type semiconductor layer / i-type semiconductor layer / n
Type semiconductor layer / p type semiconductor layer / i type semiconductor layer / n type semiconductor layer are formed and laminated in this order, and the structure using silver as the second electrode is the most general structure, but the present invention is effective. In order to carry out the invention, the amount of bound hydrogen in the substantially intrinsic semiconductor thin film on the incident side of sunlight is preferably 15 to 50 atomic%, and the second substantially intrinsic semiconductor thin film is preferably 0.5. ~ 1
A first and a second p-type semiconductor layer, such that it is 5 atom%,
It is clear from the invention that the first and second n-type semiconductor layers and the first and second electrodes may be arranged and arranged.

When a substrate or a first electrode that does not transmit light is used on the substrate side, a transparent transparent electrode is used as the second electrode, and a second substantially transparent electrode on the sunlight incident side is used. The amount of bound hydrogen in the intrinsic semiconductor thin film is 15 to 50 atomic%,
0.5 to 15 atomic% of the first substantially intrinsic semiconductor thin film
The only thing that can be done by deploying the configuration is
it is obvious.

Further, in the present invention, the constitutions of the semiconductors and the materials that are the minimum indispensable constituents of the solar cell have been shown. The p-type semiconductor layer and the i-type semiconductor layer, the i-type semiconductor layer and the n-type semiconductor layer, Introducing an interface layer for improving the performance of the solar cell at the interface between the first n-type semiconductor layer and the second p-type semiconductor layer, the first electrode and the first p-type semiconductor layer, etc. It is obvious that the interface layers are not limited in any way, and that these interface layers can be used freely according to the purpose, and do not impede the purpose of the present invention.

Regarding the method of forming these semiconductor layers,
There are plasma CVD method, photo CVD method, vapor deposition method, and sputtering method, and the bound hydrogen amount of the first and second substantially intrinsic semiconductor thin film layers specified in the present invention is preferably 0.5 to.
The film forming method is not particularly limited as long as it can be controlled to 15 atom% and 15 to 50 atom%, and preferably,
Plasma CVD or optical CVD is a convenient method for film formation.

[0028]

【Example】

Example 1 A film forming apparatus to which plasma CVD can be applied was used as an apparatus for forming an amorphous silicon solar cell. FIG. 3 shows a schematic view of the plasma CVD apparatus. This is a schematic sectional view showing an example of an apparatus for producing a solar cell used in the present invention, in which 1 is a high frequency power source, 2 is a matching circuit device, 3 is a high frequency electrode, 4 is a gas supply system, and 5 is a substrate. Heater
6 is a vacuum exhaust system, 10 is a substantially intrinsic semiconductor layer deposition chamber, 21 is a high frequency power supply, 22 is a matching circuit device, 23 is a high frequency electrode, 24 is a gas supply system, 25 is a substrate heating heater, and 26 is a vacuum. Exhaust system, 30 is dope layer film forming chamber, 45 is heater, 46 is vacuum exhaust system, 50
Is a sample loading / unloading chamber, and 101 is a sample (substrate).

That is, the apparatus comprises a sample loading / unloading chamber, a doped film deposition chamber for forming first and second p-type and n-type semiconductor thin films, and first and second substantially intrinsic semiconductor thin films. It is composed of three i-layer film forming chambers for forming Hereinafter, the film thickness is indicated by Å. First, after installing a glass substrate made of tin oxide with a transparent electrode in the preparation room,
The substrate was heated by evacuation. Evacuate to a vacuum degree of 1 × 10 ^-6 torr and heat at 100 ° C for 30 minutes. Next, the substrate was transported to the dope film forming chamber to form a p-type amorphous silicon carbide thin film. A p-type amorphous silicon carbide thin film was prepared by introducing disilane / diborane / methane / hydrogen as a raw material gas at a ratio of 5 / 0.01 / 3/500 at a pressure of 0.2 Torr,
A high frequency power of 2.0 W / cm ^{2 was} applied at a forming temperature of 150 ° C., and a plasma CVD method was used. The formation rate of the p-type amorphous silicon carbide thin film was 0.2 Å / s, and the film formation time was 600 seconds, and the film thickness was 120 Å. After temporarily stopping the formation of the p-type amorphous silicon carbide thin film and performing vacuum evacuation of the residual gas, disilane / methane / hydrogen was added.
Introduced at a rate of 5/3/100, pressure 0.1 Torr, forming temperature 150
A high frequency power of 1.0 W / cm ^{2 was} applied at 0 ° C., and 100 Å was formed as a p / i interface layer by the plasma CVD method.
Next, the substrate is transferred to the i-layer deposition chamber and disilane 20cc / min
Of the amorphous silicon thin film by plasma CVD under the conditions of a pressure of 0.30 Torr and a forming temperature of 100 ° C.
A first substantially intrinsic semiconductor layer was formed with a thickness of Å. The plasma CVD method used high-frequency discharge of 13.56 MHz. At this time, the high frequency power was 0.1 W /. After forming the i-type semiconductor thin film, the substrate was transferred to the dope layer deposition chamber again. A raw material gas consisting of monosilane / phosphine / hydrogen was introduced so that the respective flow rates were 10 / 0.01 / 500. A first n-type semiconductor thin film of 300 Å was formed by plasma CVD under the conditions of a pressure of 0.2 Torr and a forming temperature of 150 ° C. The plasma CVD method used high-frequency discharge of 13.56 MHz. At this time, the high frequency power was 2.0 W / cm ² .

Further, in order to form a second p-type semiconductor layer, disilane / diborane / methane / hydrogen is used as a source gas in the same manner as in the preparation of the first p-type amorphous silicon carbide thin film. Introduced at a rate of 0.01 / 3/500, pressure 0.2 Torr,
A high-frequency power of 2.0 W / cm ^{2 was} applied at a formation temperature of 150 ° C. to form a film thickness of 120 Å by the plasma CVD method. As in the previous case, once the film formation of the p-type amorphous silicon carbide thin film was stopped and the residual gas was evacuated, disilane / methane / hydrogen was introduced at a ratio of 5/3/100, and the pressure was increased. 0.
High frequency power 1.0 W / cm at 1 Torr and formation temperature of 150 ℃
^{2 was} applied and 100 Å was formed as a p / i interface layer by the plasma CVD method. Next, the substrate is transferred to the i-layer deposition chamber, 10 cc / min of monosilane is introduced, and the pressure is 0.05 Torr.
Amorphous silicon thin film with a film thickness of 3000 Å by high frequency power of 0.1 W / cm ² by high frequency discharge plasma CVD method of 13.56 MHz under the condition of formation temperature of 185 ℃, the second substantially intrinsic semiconductor layer. Was formed. After forming the i-type semiconductor thin film, the substrate was transferred to the dope layer deposition chamber again.
A raw material gas consisting of monosilane / phosphine / hydrogen was introduced so that the respective flow rates were 10 / 0.01 / 500. Plasma C under the conditions of pressure 0.2 Torr and formation temperature 150 ℃
A first n-type semiconductor thin film having a film thickness of 700 Å was formed by the VD method. The plasma CVD method used high-frequency discharge of 13.56 MHz. At this time, the high frequency power was 2.0 W / cm ² .

Then, the film was taken out from the thin film forming apparatus and a silver electrode was formed by vacuum vapor deposition. Light of AM 1.5, 100 mW / cm ² was irradiated with a solar simulator to measure photoelectric characteristics of the amorphous silicon solar cell. As a result, an open circuit voltage of 1.83 V and a fill factor of 0.78, which are extremely high values, were obtained, and the effects of the present invention were confirmed.
/ cm ² , which is a large value, and as a result, the photoelectric conversion efficiency is
It was excellent at 11.6%. The amount of impurities contained in the substantially intrinsic semiconductor layer of the solar cell fabricated in this way was quantitatively measured using SIMS (Secondary Ion Mass Spectroscopy). Oxygen 0.2 atom%, nitrogen 0.002 atom% , Carbon 0.02 atomic%, germanium, and tin were not detected (less than a few ppm), and it was found that impurities do not contain foreign elements that affect the optical band gap. The amount of bound hydrogen was 24 atomic% in the first substantially intrinsic semiconductor thin film and 10 atomic% in the second substantially intrinsic semiconductor thin film.

Example 2 In Example 1, a solar cell was manufactured by changing the conditions for forming the first and second substantially intrinsic semiconductor thin films as follows. The first and second p-type semiconductor thin films, the first and second n-type semiconductor thin films, and the p / i interface layer are the same as in Example 1. The first substantially intrinsic semiconductor layer is
Introducing 20cc / min of monosilane and 50cc / min of hydrogen, pressure
0.20 Torr, formation temperature 80 ℃, high frequency power 0.1 W / cm ² plasma CVD method with a film thickness of 800 Å, and the second substantially intrinsic semiconductor layer is monoccisilane 10 cc / min.
, The pressure is 0.05 Torr, high frequency power is 0.05 W / cm ² ,
A thin film having a film thickness of 4000 Å was formed under the condition of the forming temperature of 230 ° C. When the performance of the obtained solar cell was measured, the open-ended voltage was 1.84 V, the fill factor was 0.77, and the short-circuit photocurrent was 8.5 mA / cm ² ,
The photoelectric conversion efficiency was 11.9%, which was extremely excellent. SIMS (Secondary Ion Mass Spectroscopy) is used to determine the amount of impurities contained in the substantially intrinsic semiconductor layer of the solar cell thus manufactured.
Quantitative measurement was carried out using 0.06 atomic% oxygen and 0.000 nitrogen.
It was found that 5 atomic%, 0.02 atomic% carbon, germanium, and tin were not detected (several ppm or less), and it was found that impurities did not contain heterogeneous elements that could affect the optical band gap. The amount of bound hydrogen was 26 atomic% in the first substantially intrinsic semiconductor thin film and 8 atomic% in the second substantially intrinsic semiconductor thin film.

Example 3 In Example 1, a solar cell was manufactured by changing the conditions for forming the first and second substantially intrinsic semiconductor thin films as follows. The first and second p-type semiconductor thin films, the first and second n-type semiconductor thin films, and the p / i interface layer are the same as in Example 1. The first substantially intrinsic semiconductor layer is
Monosilane / Silicon tetrafluoride 20 / 10cc / min, Hydrogen 50cc / m
After introducing in, the pressure was 0.15 Torr, the formation temperature was 100 ° C, and the high frequency power was 800 W by plasma CVD under the condition of 0.1 W / cm ^2.
The film thickness of Å, and the second substantially intrinsic semiconductor layer, monosisilane / silicon tetrafluoride 20 / 10cc / min was introduced, the pressure was 0.10 Torr, the high frequency power was 0.05 W / cm ² , the formation temperature. 250 ° C
A thin film having a film thickness of 4000 Å was formed under the above condition.

When the performance of the obtained solar cell was measured, the open circuit voltage was 1.80 V, the fill factor was 0.78, and the short circuit photocurrent was 8.4.
At mA / cm ² , the photoelectric conversion efficiency was 11.8%, which was extremely excellent. The amount of impurities contained in the substantially intrinsic semiconductor layer of the solar cell fabricated in this way was quantitatively measured using SIMS (Secondary Ion Mass Spectroscopy). Oxygen 0.4 atom%, nitrogen 0.01 atom% , Carbon 0.03 atomic%, germanium,
Tin is not detected (less than a few ppm), and fluorine is 1.5 atomic%
Therefore, it was found that the impurities do not include a different element that affects the optical band gap. The amount of bound hydrogen was 31 atom% in the first substantially intrinsic semiconductor thin film and 4 atom% in the second substantially intrinsic semiconductor thin film.

Comparative Example 1 The formation of the first substantially intrinsic semiconductor layer was as follows.
Amorphous silicon was formed under exactly the same conditions as in Example 1 except that it was formed.
Con solar cells were formed. First substantially intrinsic semiconductor
The layer is a mixed gas of monosilane / methane (gas flow ratio 5/0.
5) 10cc / min, pressure 0.15Torr, forming temperature 120 ℃, high frequency
Wave power is 0.1 W / cm ²70 by plasma CVD under the conditions
A film thickness of 0 Å was formed. The conditions for forming the intrinsic thin film are
Of the first substantially intrinsic thin film prepared in Example 1
Matched to the size of the optical band gap. Obtained solar cell
The open circuit voltage was 1.82V, and the
0.72 Short circuit photocurrent 8.1mA / cm²And the photoelectric conversion efficiency is 10.6%
And the solar cell characteristics with a low fill factor.

Comparative Example 2 The formation of the first substantially intrinsic semiconductor layer was as follows.
Amorphous silicon was formed under exactly the same conditions as in Example 2 except that it was formed.
Con solar cells were formed. First substantially intrinsic semiconductor
The layer is a mixed gas of monosilane / methane (gas flow ratio 5/0.
8) 15cc / min, pressure 0.20Torr, forming temperature 100 ℃, high frequency
Wave power is 0.1 W / cm ²80 by the plasma CVD method under the conditions
A film thickness of 0 Å was formed. The conditions for forming the intrinsic thin film are
Of the first substantially intrinsic thin film prepared in Example 2
Matched to the size of the optical band gap. Obtained solar cell
The open circuit voltage was 1.83V, and the
0.70 Short circuit photocurrent 8.1mA / cm²And the photoelectric conversion efficiency is 10.4%
And the solar cell characteristics with a low fill factor.

[0037]

As is apparent from the above examples and comparative examples, the first and second substantially intrinsic semiconductor layers are
In a solar cell formed substantially only of hydrogenated amorphous silicon without containing a different element other than hydrogen or fluorine, as a result of the film characteristics of the substantially intrinsic semiconductor layer being improved,
The fill factor of the solar cell characteristics was significantly improved compared to the solar cells using the materials used in the prior art, and a solar cell with excellent characteristics was formed. That is, the present invention greatly contributes to the improvement of the photoelectric conversion efficiency of the amorphous silicon solar cell at the practical level. As described above, the present invention can provide the technology that enables the high conversion efficiency required for the solar cell for electric power, and it must be said that it is an extremely great contribution to the energy industry.

[Brief description of drawings]

[Figure 1] Relationship between the content of different elements and the optical band gap

FIG. 2 is a schematic sectional view showing an example of a configuration of an amorphous solar cell used in the present invention.

FIG. 3 is a schematic sectional view showing an example of an apparatus for producing a solar cell used in the present invention.

[Explanation of symbols]

 1 High Frequency Power Supply 2 Matching Circuit Device 3 High Frequency Electrode 4 Gas Supply System 5 Substrate Heating Heater 6 Vacuum Evacuation System 10 Substantially Intrinsic Semiconductor Layer Deposition Room 21 High Frequency Power Supply 22 Matching Circuit Device 23 High Frequency Electrode 24 Gas Supply System 25 Substrate Heating Heater 26 Vacuum exhaust system 30 Doped layer deposition chamber 45 Heating heater 46 Vacuum exhaust system 50 Sample preparation / extraction chamber 101 Sample (substrate) 110 Substrate 111 Transparent electrode 112 p-type semiconductor thin film 113 i-type semiconductor thin film 114 n-type semiconductor thin film 115 p-type semiconductor thin film 116 i-type semiconductor thin film 117 n-type semiconductor thin film 118 back electrode

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kiyuki Yanagawa 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Nobuyuki Ishiguro 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chem Co., Ltd. (72) Inventor Kimihiko Saito 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A substrate, a first electrode, a first p-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, a first n-type semiconductor thin film, a second p-type semiconductor thin film, and a second p-type semiconductor thin film. In an amorphous solar cell formed by stacking a substantially intrinsic semiconductor thin film, a second n-type semiconductor thin film, and a second electrode,
An amorphous photoelectric conversion element, wherein the first substantially intrinsic semiconductor thin film and the second substantially intrinsic semiconductor thin film are made of hydrogenated amorphous silicon. 2. The amorphous photoelectric conversion device according to claim 1, wherein the amount of bound hydrogen in the first substantially intrinsic semiconductor thin film is 15 to 50 atom%. 3. The amorphous photoelectric conversion device according to claim 1, wherein the amount of bound hydrogen in the second substantially intrinsic semiconductor thin film is 0.5 to 15 atom%. 4. The bound hydrogen content of the second substantially intrinsic semiconductor thin film is 0.5 to 15 atomic%, and the bound hydrogen content of the first substantially intrinsic semiconductor thin film is 15 to 50. The amorphous photoelectric conversion device according to claim 1, wherein the amorphous photoelectric conversion device has an atomic%.