JP2733384B2 - Solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-efficiency solar cell that scatters incident light to increase light absorption in an active layer.

[0002]

2. Description of the Related Art In a solar cell using a light-reflective substrate,
For example, US Pat. No. 4,126,150 (Applicant, RCA) suggests a method for improving the efficiency by forming the light reflecting surface as a rough surface having irregularities and increasing the path length of light having a low absorption wavelength. JP-A-56-1522
No. 76 (applicant, Teijin). Further, Japanese Patent Application Laid-Open No. 59-104185 (Applicant, Exxon Research and Engineering Company) details the optical effect of a roughened substrate.

As a method of forming unevenness, Japanese Patent Application Laid-Open No. 54-15 / 1979
In Japanese Patent No. 3588 (Applicant, National Patent Development Corporation), the wet etching method is used. JP-A-59-1
No. 4682 (applicant, electrolytic foil industry, etc.) discloses roughening of aluminum by a direct current electrolytic etching method or a chemical etching method.

In Japanese Patent Application Laid-Open No. 63-169768, an example is described in which a transparent electrode is formed on a diamond thin film, and a p-type layer, an i-type layer and an n-type layer are laminated on the transparent electrode. It is shown.

[0005]

2. Description of the Related Art The conventional method of forming unevenness on the surface of a substrate has various problems when a solar cell is formed.

[0006] For example, in etching with a solution such as direct current electrolytic etching or chemical etching, an etching residue of the substrate is generated on the substrate surface. Therefore, when a semiconductor layer is deposited on such a substrate, the etching residue diffuses into the semiconductor layer, thereby deteriorating the characteristics of the solar cell. Also,
Such an etching residue has a problem that the semiconductor layer deposited thereon is easily peeled off because of poor adhesion to the substrate, and it is difficult to deposit a solar cell having uniform characteristics.

In the sand blast method, fine particles are sprayed on a substrate to form irregularities, so that the fine particles sprayed on the substrate remain, and the fine particles sometimes become nuclei for abnormal growth of the semiconductor layer. Further, there is also a problem that the fine particles have poor adhesion to the substrate, so that the semiconductor layer deposited thereon is easily peeled off. Furthermore, in the sand blast method, since fine particles are sprayed to form irregularities on the substrate surface, distortion occurs in the substrate, which may cause distortion in the deposited semiconductor layer because it is relaxed with time. This has led to peeling of the semiconductor layer and deterioration of electrical characteristics.

In the case of forming irregularities on the substrate surface by the co-evaporation method, at least two kinds of raw materials are simultaneously vapor-deposited, so that there is a problem that non-uniformity is likely to occur in the vapor-deposited film. There is a problem that characteristics are likely to be generated in the solar cell formed by deposition.

Further, the above-mentioned Japanese Patent Application Laid-Open No. 63-169969
In the case of using a diamond thin film as a substrate of a solar cell described in Japanese Patent Application Laid-Open Publication No. H11-209, a solar cell is formed by forming a transparent electrode on the diamond thin film and laminating a semiconductor layer on the transparent electrode. In such a layer configuration, diamond is used as a high-resistance substrate instead of a glass substrate. Therefore, a transparent electrode is provided on the diamond thin film. In this conventional example, excellent adhesion between the diamond thin film and the semiconductor layer cannot be utilized. Further, there is a problem that constituent elements of the transparent electrode diffuse into the semiconductor layer.

[0010]

An object of the present invention is to solve the problems of the prior art.

That is, an object of the present invention is to provide a solar cell in which the solar cell characteristics do not deteriorate due to the etching residue.

It is another object of the present invention to provide a solar cell free from the effects of residual fine particles generated on a substrate by a sandblast method or the like. Another object of the present invention is to provide a solar cell in which characteristics are not deteriorated due to temporal relaxation of substrate distortion due to collision of fine particles.

Still another object of the present invention is to provide a solar cell free from the influence of the diffusion of the electrode material into the semiconductor layer.

Another object of the present invention is to provide a solar cell having high conversion efficiency.

Still another object of the present invention is to provide a solar cell free from the problem of deterioration of the solar cell over time due to distortion of the substrate.

[0016]

[Means for Solving the Problems] The solar cell of the present invention comprises:
In order to solve the above problems and achieve the object, on a conductive substrate, a p-type layer made of a non-single crystal containing Si, an i-type layer as an active layer, and an n-type semiconductor layer are stacked. In a solar cell configured as above, at least one of the p-type layer and the n-type layer contains a carbon atom, and has irregularities on the surface between the conductive substrate and the semiconductor layer, and controls valence electrons. Of a polyhedral diamond layer in the form of a smooth polyhedron containing an additive
It has a prevention layer .

FIG. 1 is a schematic explanatory view of one example of the solar cell of the present invention.

In FIG. 1, a solar cell according to the present invention comprises a conductive substrate 101, a diamond layer 102, an n-type layer 103, i
It comprises a mold layer 104, a p-type layer 105 and a transparent electrode 106.

Hereinafter, each layer constituting the solar cell of the present invention will be described in detail.

(Conductive Substrate) In the present invention, the conductive substrate is formed of a conductive material or an insulating material subjected to a conductive treatment. As the conductive material, for example, NiC
r, stainless steel, Al, Cr, Mo, Au, Nb, T
a, V, Ti, Pt, Pb and other metals or alloys thereof.

As the electrically insulating material, polyester,
Films or sheets of synthetic resin such as polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, etc., glass, ceramics, paper and the like are usually used. It is desirable that at least one surface of these electrically insulating materials is subjected to conductive treatment, and another layer is provided on the conductive-treated surface side.

For example, in the case of glass, N
iCr, Al, Cr, Mo, Au, Ir, Nb, Ta,
V, Ti, Pt, Pd, In ₂ O ₃ , SnO ₂ , ITO
By providing a thin film made of (In ₂ O ₃ + SnO ₂ ) or the like, conductivity is imparted, or if it is a synthetic resin film such as a polyester film, NiCr, Al, A
g, Pb, Zn, Ni, An, Cr, Mo, Ir, N
b, Ta, V, Ti, Pt, etc.
Provided on the surface by electron beam evaporation, sputtering, etc.,
Alternatively, the surface is laminated with the metal to impart conductivity to the surface.

The thickness of the substrate is appropriately determined so that a desired solar cell is formed.
In terms of mechanical strength and the like, the thickness is usually 10 μm or more.

(Diamond Layer) In the present invention, the diamond layer is an important layer that functions to improve the exchange efficiency of the solar cell and to reduce deterioration over time.

In the present invention, the diamond layer is formed of polycrystalline diamond. The polycrystalline diamond includes a smooth polyhedron shape, a skull crystal shape, a needle crystal aggregate shape, and the like. In the present invention, a polycrystal diamond having a smooth polyhedron shape is suitable.

As described above, the diamond layer formed of polycrystalline diamond having a smooth polyhedral shape has irregularities on the surface of the diamond layer. The light radiated into the solar cell is scattered by the unevenness, and the scattered light is totally reflected on the surface of the solar cell, or the scattered light travels obliquely in the thickness direction in the solar cell. As a result, the amount of light absorbed in the solar cell increases,
The conversion efficiency of the solar cell increases. In particular, polycrystalline diamond having a smooth polyhedron shape has a substantially polyhedral surface on the smooth polyhedron, and has a better surface property than each minute surface of concavities and convexities according to the prior art. As a result, the light confinement effect in the solar cell becomes better than before, and the conversion efficiency of the solar cell is improved.

Further, since the polycrystalline diamond layer having a smooth polyhedral shape has a very dense polycrystalline diamond structure, diffusion of metal from the conductive substrate into the semiconductor layer can be prevented.

Also, polycrystalline diamond has a soft crystalline interface structurally, so that strain during the production of a solar cell can be reduced. As a result, it is possible to prevent deterioration of the solar cell over time due to diffusion or distortion of impurities from the substrate.

Not all smooth polyhedral shapes are suitable for the smooth polyhedral polycrystalline diamond layer having such a function, but very limited ones are suitable.

The diamond layer suitable for the present invention has a layer thickness of 0.1 μm to 5 μm and a surface unevenness of 0.05 S to 5 μm.
1S.

The size of the smooth polyhedral crystal is 0.05 μm to 5 μm in average radius.

Further, hydrogen is contained in the diamond layer, particularly at the polycrystalline interface. A hydrogen content of 1 to 5 at% is suitable.

In addition, since the diamond layer of the present invention is provided between the conductive substrate and the semiconductor layer, the diamond layer needs to have low resistance. The preferred dark conductivity of the diamond layer is 0.1 S / cm or more.
The doping amount of the impurity necessary for achieving such dark conductivity is 1 at% to 10 at%. When the doping amount of the impurity is more than 10 at%, the diamond layer cannot be formed of a smooth polyhedral crystal.

In the present invention, when the valence electron controlling agent contained in the diamond layer is an n-type, an element belonging to Group 5 of the periodic table, particularly N, P, As, Sb or Bi is suitable. I have. In the case of a p-type, an element belonging to Group 3 of the periodic table, particularly, B, Al, Ga, In, or Tl is suitable.

The diamond layer in the present invention is deposited by a hot filament CVD method, a high frequency plasma CVD method, a microwave plasma CVD method, a direct current plasma CVD method, an ion beam method, or the like.

Among them, the microwave plasma CVD method is particularly suitable.

In the case where the diamond layer in the present invention is deposited by the plasma CVD method, suitable source gases include the following source gases.

Examples of the carbon atom-containing compound serving as a raw material gas for introducing carbon atoms include saturated hydrocarbons having 1 to 4 carbon atoms, ethylene hydrocarbons having 2 to 4 carbon atoms, and 2 to 3 carbon atoms.
Acetylene-based hydrocarbons.

Specifically, as the saturated hydrocarbon, meta-
(CH_Four), Ethane (C_TwoH₆), Propane (C
_ThreeH₈), N-butane (n-C_FourH_Ten), Pentane (C_FiveH
₁₂), And ethylene (C
_TwoH_Four), Propylene (C _ThreeH₆), Butene-1 (C
_FourH₈), Butene-2 (C_FourH₈), Isobutylene (C
_FourH₈), Penten (C_FiveH_Ten), Acetylenic hydrocarbons
Acetylene (C_TwoH_Two), Methyl acetylene
(C_ThreeH_Four), Butyne (C_FourH₆) And the like.

In addition, hydrocarbons containing halogen atoms are also included.

Specifically, CH ₃ F, CH ₂ F ₂ , CH ₃ C
1, CH ₂ Cl ₂ , CF ₄ , C ₂ H ₅ F, C ₂ H ₄ F ₂ , C ₂ H _{4
FCl, C 2 H 2 F 2} , C 2 H 2 FCl , and the like.

Further, in forming the diamond layer of the present invention, hydrogen gas is essential in addition to the above-mentioned source gas for introducing carbon atoms.

The mixing ratio of the raw material gas for introducing carbon atoms to the hydrogen gas suitable for forming the diamond layer of the present invention is 1 to 3.
10%.

In the present invention, as a starting material for introducing a Group 3 atom, specifically, for introducing a boron atom, B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H
_{11, B 6 H 10, B} 6 H 12, B 6 H 14 borohydride such as, B
Examples thereof include boron halides such as F ₃ , BCl ₃ , and BBr _{3. In} addition, AlCl ₃ , GaCl ₃ , and In
Cl ₃ and TlCl ₃ can also be mentioned.

In the present invention, the starting material for introducing a group 5 atom is effectively used. Specifically, for introducing a phosphorus atom, a hydrogenated phosphorus such as PH ₃ or P ₂ H ₄ , ₄ I,
PF ₃ , PF ₅ , PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ ,
Phosphorus halides such as PI ₃ ; In addition, As
H ₃ , AsF ₃ , AsCl ₃ , AsBr ₃ , AsF ₅ , Sb
_{H 3, SbF 3, SbF 5} , SbCl 3, SbCl 5, Bi
H ₃ , BiCl ₃ , BiBr _{3 and the} like can also be mentioned.

In addition, when depositing the diamond layer of the present invention by the plasma CVD method, it is desirable to deposit under the following conditions.

When depositing the diamond layer of the present invention,
It is necessary to prevent a gas phase reaction between the carbon-introducing gases decomposed in the plasma. Therefore, it is necessary to control the internal pressure at the time of plasma generation between 1 mTorr and 50 mTorr.

The gas for introducing carbon atoms and the hydrogen gas must be sufficiently decomposed or activated in the plasma. For this purpose, the power supplied into the reaction space needs to be controlled between 0.01 to 1 W / sccm · cm ³ with respect to the flow rate of the gas for introducing carbon atoms and the volume of the reaction space.

In addition, the temperature of the substrate is an important factor in forming the diamond layer of the present invention when the gas for introducing carbon atoms and the hydrogen gas which are decomposed by the plasma in the reaction space react on the substrate. In the present invention, the temperature is desirably 200 ° C to 800 ° C.

(N-type layer) In the present invention, the n-type layer is an important layer that controls the electromotive force and photocurrent of the solar cell.

As the material of the n-type layer, a silicon-containing non-single-crystal semiconductor is suitable, and in particular, hydrogenated and halogenated amorphous silicon (including microcrystalline silicon)
Are suitable. More specifically, microcrystalline silicon in amorphous silicon is optimal.

When light irradiation is performed from the n-type layer side,
In order to reduce light absorption in the n-type layer and introduce more light into the i-type layer, it is preferable to use amorphous silicon carbide (including microcrystalline silicon carbide) as a material for the n-type layer. .

Microcrystal silicon and microcrystal silicon carbide preferably have a particle size of 30 ° to
200 °, optimally between 30 ° and 100 °.

In the case of microcrystalline silicon or microcrystalline silicon carbide, the content of hydrogen and halogen atoms is preferably 1 at% to 10 at%.
%, Optimally between 1 at% and 7 at%.

In the case of amorphous silicon and amorphous silicon carbide, the contents of hydrogen and halogen atoms are as follows:
Preferably 1 at% to 40 at%, optimally 5 at%
２０20 at%.

As the valence electron controlling agent contained in the n-type layer, a Group 5A element of the periodic table is suitable. Among them, phosphorus (P), nitrogen (N), arsenic (As), and antimony (S6) are particularly suitable.

In addition, the content of the valence electron controlling agent contained in the n-type layer is preferably 1 at% to 20 at%,
Optimally, it is 5 at% to 10 at%.

Regarding the electrical characteristics of the n-type layer, those having an activation energy of 0.2 eV or less are preferable, and those having an activation energy of 0.1 eV or less are optimal within the above-mentioned conditions. The specific resistance is preferably 10 Ωcm or less, and most preferably 1 Ωcm or less.

(I-type layer) In the present invention, the i-type layer is an important layer that generates and transports carriers with respect to irradiation light. As a non-single-crystal material containing silicon atoms suitable for the i-type layer, amorphous silicon (microcrystalline silicon) can be given. Among amorphous silicon, hydrogenated amorphous silicon, hydrogenated and halogenated amorphous silicon are particularly suitable.

The content of hydrogen or halogen contained in the amorphous silicon is very important for reducing localized levels and maintaining high quality electric characteristics. The bonding state of a hydrogen atom and a silicon atom is preferably a state in which one hydrogen atom is bonded to a silicon atom. The same applies to the bonding state between a halogen atom and a silicon atom.

The content of hydrogen atoms and halogen atoms is
It is preferably 1 at% to 40 at%, and most preferably 5 a%.
t% to 20 at%.

Further, the thickness of the i-type layer is an important parameter that affects the characteristics of the photovoltaic device of the present invention.
A preferred layer thickness of the i-type layer is 0.1 μm to 1 μm,
The optimum layer thickness is between 0.2 μm and 0.6 μm.

This layer thickness is desirably designed within the above range in consideration of the absorption coefficient of the i-type layer and the spectrum of sunlight and the like.

(P-type layer) In the present invention, the p-type layer is an important layer that controls the photovoltaic power and photocurrent of the solar cell.

As the material of the p-type layer, a non-single-crystal semiconductor containing silicon atoms is suitable, and in particular, hydrogenated and halogenated amorphous silicon (including microcrystalline silicon) and hydrogenated and halogenated amorphous silicon carbide are suitable. is there.

More specifically, in order to further increase photovoltaic power and photocurrent, microcrystalline silicon carbide having a wide bandgap and high transmittance to sunlight is preferable.

In the present invention, the microcrystalline silicon and the microcrystalline silicon carbide preferably have a particle size of 30 to 500 °, and most preferably 50 to 500 °.
It is 300Å.

In the case of a microcrystal, the content of hydrogen and halogen atoms is preferably 1 at% to 1 at%.
0 at%, and optimally 1 at% to 7 at%.

In the present invention, when amorphous, the content of hydrogen and halogen atoms is preferably 1a
t% to 40 at%, optimally 5 to 20 at%.

The thickness of the p-type layer is preferably from 10 ° to 50 °.
0 °, optimally between 30 ° and 200 °.

The carbon content in amorphous silicon carbide (including microcrystalline silicon carbide) is preferably 5 at% to 50 at%, and most preferably 10 at% to 30 at%.
at%.

Further, as an additive contained in the p-type layer, an element belonging to Group 3 of the periodic table is suitable. Among them, boron (B), aluminum (Al), gallium (Ga)
Is optimal.

In addition, the content of the additive contained in the p-type layer is preferably 1 at% to 20 at%, and most preferably 5 at% to 10 at%.

Regarding the electrical characteristics of the p-type layer, those having an activation energy of 0.2 eV or less are preferable and those having an activation energy of 0.1 eV or less are optimal within the above-mentioned conditions. The specific resistance is preferably 10 Ωcm or less, and most preferably 1 Ωcm or less.

(Transparent Electrode) The transparent electrode used in the present invention preferably has a light transmittance of 85% or more in order to efficiently absorb light from the sun or a white fluorescent lamp into the semiconductor layer. Further, the sheet resistance is set to 1 so that the resistance of the output of the solar cell does not become a resistance component.
It is desirable that the resistance is not more than 00Ω. As a material having such characteristics, for example, SnO ₂ , In ₂ O ₃ , ZnO, C
Examples thereof include metal oxides such as dO, Cd ₂ SnO ₄ and ITO (In ₂ O ₃ + SnO ₂ ), and metal thin films in which a metal such as Au, Al, and Cu is formed to be extremely thin and translucent.

As the manufacturing method, a resistance heating evaporation method, an electron beam heating evaporation method, a sputtering method, a spraying method, or the like can be used, and it is appropriately selected as desired.

In the present invention, the p-type layer, the n-type layer, and the i-type layer are formed by DC plasma CVD, high-frequency plasma CVD,
It is suitable to form by a microwave plasma CVD method or the like.

The following gases are mentioned as source gases suitable for the plasma CVD method.

The source gas for supplying Si used in the present invention includes SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , Si ₄
Silicon hydrides (silanes) in a gaseous state or capable of being gasified, such as H _10, are mentioned as being effectively used.
In terms of the ease of handling the layer creation work and the good Si supply efficiency,
Preferred are iH ₄ and Si ₂ H ₆ .

As the raw material gas for introducing a halogen atom used in the present invention, many halogen compounds can be mentioned. For example, a gas state such as a halogen gas, a halide, an interhalogen compound, or a silane derivative substituted with a halogen can be used. Or a gaseous halogen compound is preferred.

Further, in the present invention, a silicon compound containing a halogen atom, which is a gas state or can be gasified, comprising silicon atoms and halogen atoms as constituents, can also be mentioned as effective ones.

Examples of the halogen compound that can be suitably used in the present invention include halogen gas of fluorine, chlorine, bromine and iodine, BrF, ClF, ClF ₃ and Br.
Interhalogen compounds such as F ₅ , BrF ₃ , IF ₃ , IF ₇ , ICl, and IBr can be mentioned.

Examples of the silicon compound containing a halogen atom, ie, a silane derivative substituted with a halogen atom, include, for example, SiF ₄ , Si ₂ F ₆ , SiCl ₄ , SiBr ₄
And the like are preferred.

The above-mentioned silicon compound containing a halogen atom may be employed and introduced into a chamber characterized by the present invention by a glow discharge method to form a plasma atmosphere of the gas.

In the present invention, the above-mentioned halogen compounds or halogen-containing silicon compounds are effectively used as the raw material gas for introducing halogen atoms. In addition, HF, HCl, HBr, HI , SiH ₂ F ₂ , SiH ₂ I ₂ , SiH ₂ C
Halogen-substituted silicon hydrides such as l ₂ , SiHCl ₃ , SiH ₂ Br ₂ , SiHBr ₃ , and other gaseous or gasifiable halides having a hydrogen atom as one of the constituent elements are also listed as effective starting materials. Can be.

These halides containing a hydrogen atom include:
In the present invention, a hydrogen atom which is extremely effective in controlling electric or photoelectric characteristics is introduced simultaneously with the introduction of a halogen atom into a layer formed at the time of layer formation. Is done.

The carbon atom-containing compound serving as a raw material for introducing carbon atoms includes, for example, a saturated hydrocarbon having 1 to 4 carbon atoms,
Examples thereof include an ethylene hydrocarbon having 2 to 4 carbon atoms and an acetylene hydrocarbon having 2 to 3 carbon atoms.

Specifically, as the saturated hydrocarbon, meta-
(CH_Four), Ethane (C_TwoH₆), Propane (C
_ThreeH₈), N-butane (n-C_FourH_Ten), Pentane (C_FiveH
₁₂), And ethylene (C
_TwoH_Four), Propylene (C _ThreeH₆), Butene-1 (C
_FourH₈), Butene-2 (C_FourH₈), Isobutylene (C
_FourH₈), Penten (C_FiveH_Ten), Acetylenic hydrocarbons
Acetylene (C_TwoH_Two), Methyl acetylene
(C_ThreeH_Four), Butyne (C_FourH₆) And the like.

Examples of the source gas containing Si, C and H as constituent atoms include alkyl silicides such as Si (CH ₃ ) ₄ and Si (C ₂ H ₄ ).

When a glow discharge method is used to form a layer containing Group 3 atoms or Group 5 atoms, the starting material serving as a source gas for forming the layer is the same as the starting material for Si described above. A starting material for introducing a Group 3 atom or a Group 5 atom is added to one appropriately selected from the above. As such a starting material for introducing a Group 3 atom or a Group 5 atom, a gaseous substance having a Group 3 atom or a Group 5 atom as a constituent atom or a gasified substance that can be gasified is used. , Any of them.

In the present invention, a substance effectively used as a starting material for introducing a Group 3 atom includes, specifically, B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H
_{11, B 6 H 10, B} 6 H 12, B 6 H 14 borohydride such as, B
Examples thereof include boron halides such as F ₃ , BCl ₃ , and BBr _{3. In} addition, AlCl ₃ , GaCl ₃ , and In
Cl ₃ and TlCl ₃ can also be mentioned.

In the present invention, the effective use of the starting material for introducing a group V atom is, specifically, for introducing a phosphorus atom, for example, hydrogen phosphide such as PH ₃ or P ₂ H ₄ , PH ₄ I, P
_{F 3, PF 5, PCl 3} , PCl 5, PBr 3, PFr 5, P
Halogenated phosphorus such as I ₃ and the like. In addition, AsH ₃ ,
AsF ₃ , AsCl ₃ , AsBr ₃ , AsF ₅ , SbH ₃ ,
SbF ₃ , SbF ₅ , SbCl ₃ , SbCl ₅ , BiH ₃ ,
BiCl ₃ , BiBr _{3 and the} like can also be mentioned.

(Experimental Examples) Hereinafter, the present invention will be described in more detail by way of experimental examples, but the present invention is not limited thereto.

Experimental Example 1 A solar cell of the present invention was formed by a microwave (hereinafter abbreviated as “μW”) glow discharge decomposition method.

FIG. 3 shows a solar cell manufacturing apparatus comprising a source gas supply device 1020 and a deposition device 1000 by the μW glow discharge decomposition method.

In the gas cylinders 1071 to 1075 in the figure, the source gas for forming each layer of the present invention is sealed, and 1071 is a SiH ₄ gas (purity 99.99).
%) Cylinder 1072 is H ₂ gas (purity 99.9999)
%) Cylinder, 1073 is CH ₄ gas (purity 99.999%)
%) Bomb, 1074 H 10% in diluted the B ₂ H ₆ gas (99.999% purity at ₂ gas, hereinafter "B ₂ H ₆ /
Abbreviated with H ₂ ") bomb, 1075 10% with H ₂ gas
Is a PH ₃ gas (purity: 99.999%, hereinafter abbreviated as “PH ₃ / H ₂ ”). In addition, when the gas cylinders 1071 to 1075 are attached, the respective gases are introduced from the valves 1051 to 1055 into the gas pipes of the inflow valves 1031 to 1035 in advance.

In the figure, reference numeral 1004 denotes a substrate,
Square, 0.25mm thick stainless steel (SUS430B
A), and the surface is mirror-finished.

First, an SiH ₄ gas from the gas cylinder 1071, an H ₂ gas from the gas cylinder 1072,
CH ₄ gas from 73, B ₂ H ₆ /
H ₂ gas, PH ₃ / H ₂ gas from gas cylinder 1075,
Valves 1051 to 1055 are opened and introduced, and each gas pressure is adjusted to 2 kg / cm ² by pressure regulators 1061 to 1065.
Was adjusted.

Next, it is confirmed that the inflow valves 1031 to 1035 and the leak valve 1009 of the deposition chamber 1001 are closed, and that the outflow valves 1041 to 1045 and the auxiliary valve 1008 are opened. The conductance (butterfly type) valve 1007 is fully opened, the deposition chamber 1001 and the gas pipe are evacuated by a vacuum pump (not shown), and the vacuum gauge 1006 reads about 1 × 10 ^−4.
When the pressure reached Torr, the auxiliary valve 1008 and the outflow valves 1041 to 1045 were closed.

Next, the inflow valves 1031 to 1035 are gradually opened, and each gas is supplied to the mass flow controller 1.
021 to 1025.

After the preparation for film formation was completed as described above, a diamond layer, an n-type layer, an i-type layer, and a p-type layer were formed on the substrate 1004.

To form a diamond layer, the substrate 10
04 is heated to 400 ° C. by a heater 1005,
The outlet valves 1042, 1043, 1045 and the auxiliary valve 1008 are gradually opened, and H ₂ gas, CH ₄ gas, PH
₃ / H ₂ gas is supplied to the deposition chamber 100 through the gas introduction pipe 1003.
1 was introduced. At this time, the H ₂ gas flow rate is 500 sc
cm, CH ₄ gas flow rate was 5 sccm, and PH ₃ / H ₂ gas flow rate was 2.5 sccm.
The pressure inside the deposition chamber 1001 is adjusted to 20 mTorr while the conductance valve 10
07 opening was adjusted. Next, a DC bias of −100 V was applied to the deposition chamber 1001 by the DC power supply 1011 to the substrate 1004. Thereafter, the power of a μW power supply (not shown) is set to 0.5 W / cm ³ , and the deposition chamber 10 is passed through a waveguide (not shown), a waveguide 1010 and a dielectric window 1002.
01, a μW glow discharge is generated, and the formation of a diamond layer on the substrate 1004 is started.
When a diamond layer having a thickness of 1 μm was formed, the μW glow discharge was stopped, the output of the DC power supply 1011 was turned off, and
The outflow valves 1042, 1043, 1045 and the auxiliary valve 1008 were closed to stop the gas flow into the deposition chamber 1001, and the formation of the diamond layer was completed.

Next, to form an n-type layer, the substrate 100
4 was heated to 280 ° C. by the heater 1005, and the outflow valves 1041, 1042, 1043, 1045 and the auxiliary valve 1008 were gradually opened, and SiH ₄ gas, H ₂
Gas, CH ₄ gas, and PH ₃ / H ₂ gas into the gas introduction pipe 100
3 and flowed into the deposition chamber 1001. At this time, S
iH ₄ gas flow rate 5 sccm, H ₂ gas flow rate 50 scc
m, the flow rate of CH ₄ gas was adjusted to 0.5 sccm, and the flow rate of PH ₃ / H ₂ gas was adjusted to 5 sccm by each of the Masul flow controllers 1021, 1022, 1023, and 1025. The pressure in the deposition chamber 1001 is 10 mTorr
The opening of the conductance valve 1007 was adjusted while watching the vacuum gauge 1006 so that Next, the substrate 1004
To the deposition chamber 1001 by the DC power supply 1011
A DC bias of 60 V was applied. Then, μ (not shown)
The power of the W power source is set to 0.05 W / cm ³ , and μW power is introduced into the deposition chamber 1001 through a waveguide (not shown), the waveguide unit 1010, and the dielectric window 1002 to generate μW glow discharge. The formation of an n-type layer was started on the diamond layer, and when an n-type layer having a thickness of 0.01 μm was formed, μW
The glow discharge is stopped, the output of the DC power supply 1011 is turned off,
Also, outflow valves 1041, 1042, 1043, 104
5 and the auxiliary valve 1008 were closed, the gas flow into the deposition chamber 1001 was stopped, and the formation of the n-type layer was completed.

Next, to form an i-type layer, the substrate 100
4 was heated to 280 ° C. by the heater 1005, and the outflow valves 1041 and 1042 and the auxiliary valve 1008 were gradually opened, and SiH ₄ gas and H ₂ gas were introduced into the gas introduction pipe 10.
03 into the deposition chamber 1001. At this time,
SiH ₄ gas flow rate is 50 sccm, H ₂ gas flow rate is 100
The mass flow controllers 1021 and 1022 adjusted the pressure to become sccm. The opening of the conductance valve 1007 was adjusted while watching the vacuum gauge 1006 so that the pressure in the deposition chamber 1001 became 10 mTorr. Next, a DC bias of −50 V was applied to the deposition chamber 1001 by the DC power supply 1011 to the substrate 1004. Thereafter, the electric power of the μW power supply (not shown) is reduced to 0.15 W / c
m ³ , and μW power is introduced into the deposition chamber 1001 through a waveguide, a waveguide 1010 and a dielectric window 1002 (not shown) to generate μW glow discharge, and the i-type layer is placed on the n-type layer. When the formation was started and the i-type layer having a layer thickness of 0.4 μm was formed, the μW glow discharge was stopped, the output of the DC power supply 1011 was turned off, and the formation of the i-type layer was completed.

Next, to form a p-type layer, the substrate 100
4 was heated to 280 ° C. by the heater 1005, and the outflow valves 1041, 1042, 1043, 1044 and the auxiliary valve 1008 were gradually opened, and SiH ₄ gas, H ₂
Gas, CH ₄ gas, and B ₂ H ₆ / H ₂ gas
3 and flowed into the deposition chamber 1001. At this time, S
iH ₄ gas flow rate is 3 sccm, H ₂ gas flow rate is 500 sc
cm, CH ₄ gas flow rate was 0.5 sccm, and B ₂ H ₆ / H ₂ gas flow rate was 5 sccm. The pressure in the deposition chamber 1001 is 20 mTorr
The opening of the conductance valve 1007 was adjusted while watching the vacuum gauge 1006 so that Next, the substrate 1004
To the deposition chamber 1001 by the DC power supply 1011
A DC bias of 100 V was applied. Thereafter, the power of a μW power supply (not shown) is set to 0.5 W / cm ³ , and μW power is introduced into the deposition chamber 1001 through a waveguide (not shown), a waveguide unit 1010, and a dielectric window 1002. A discharge is generated to start formation of a p-type layer on the i-type layer. When a p-type layer having a thickness of 0.005 μm is formed, the μW glow discharge is stopped, an output of the DC power supply 1011 is turned off, and an outflow valve is formed. By closing 1041, 1042, 1043, 1044 and the auxiliary valve 1008, the gas flow into the deposition chamber 1001 was stopped, and the formation of the p-type layer was completed.

Tables 1, 2 and 3 show the conditions for producing the above solar cell.

When forming the respective layers, it goes without saying that the outflow valves 1041 to 1045 other than the necessary gas are completely closed, and the respective gases are discharged in the deposition chamber 1001 and outflow valve 1041. In order to avoid remaining in the piping extending from -1045 to the deposition chamber 1001, the outflow valves 1041 to 1045 are closed, the auxiliary valve 1008 is opened, and the conductance valve 100
7 is fully opened, and the operation of once evacuating the system to a high vacuum is performed as necessary.

On the p-type layer of the solar cell thus produced, ITO (In ₂ O ₃ + SnO ₂ ) was deposited as a transparent electrode by 0.085 μm by a known method.
Was deposited by 2 μm by a known method to prepare a solar cell.
By performing the same operation, two solar cells were prepared (battery No. actual-1).

(Comparative Experimental Example 1) A substrate 1004 was heated at 350 ° C.
And a silver thin film of 0.45 μm and a ZnO thin film of 2 μm were formed on the surface of the substrate 1004 by a sputtering method.
An n-type layer, an i-type layer, a p-type layer, a transparent electrode, and a current collector were formed on the lower electrode under the same conditions as in Experimental Example 1 except that the diamond layer was not formed after the lower electrode was formed by m evaporation. Electrodes were formed to produce two solar cells (battery No. ratio−
1).

The initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics of the solar cells prepared in Experimental Example 1 (Battery No. Actual 1) and Comparative Experimental Example 1 (Battery No. Ratio 1) were evaluated.

The initial characteristics are shown in Experimental Example 1 (Battery No. Actual 1).
And 2 each prepared in Comparative Example 1 (battery No. ratio 1)
AM-1.5 (100 mW / cm^Two )
It was installed under light irradiation, and the photoelectric conversion efficiency was measured and evaluated.
As a result of the characteristic evaluation, the comparative example (battery No. ratio 1)
Therefore, the solar cell of Experimental Example 1 (Battery No. Actual 1)
The conversion efficiency was 1.25 times better on average.

The thermal degradation characteristics were measured in Experimental Example 1 (Battery No.
1) and Comparative Example 1 (battery No. ratio 1)
A constant-temperature dryer with each solar cell set at 100 ° C
(Yamato DV-41) for 1 hour
And then set at 5 ° C (Hitachi, Ltd.)
(R-107W) for 10 minutes
After that, similarly to the evaluation of the initial characteristics, AM-1.5 (1
00mW / cm^Two ) Installed under light irradiation to improve photoelectric conversion efficiency
It was measured and evaluated. As a result of the characteristic evaluation, a comparative experiment example (battery
No. In comparison with the ratio 1), the thickness of the experimental example 1 (battery No.
The positive battery had a photoelectric conversion efficiency 1.4 times better.

The stress deterioration characteristics were measured in Experimental Example 1 (battery No.
1) and Comparative Example 1 (battery No. ratio 1)
One of each of the suns whose deterioration characteristics have not been evaluated
The battery was placed on a stainless steel substrate with a radius of curvature of 54.
mm, and then returned to the plane 50 times.
Incidentally, similarly to the evaluation of the initial characteristics, the solar cell is
1.5 (100 mW / cm^Two ) Installed under light irradiation,
The conversion efficiency was measured and evaluated. As a result of characteristic evaluation,
In contrast to the experimental example (battery No. ratio 1), the experimental example 1 (battery N)
o. Actually, the solar cell 1) has a photoelectric conversion efficiency of 1.35 times better.
Had been.

A 1 μm diamond layer was formed on a stainless steel substrate under the same conditions as in Experimental Example 1 to prepare a sample for crystal analysis, and an X-ray diffractometer (Rigaku Electric R)
AD-3b type), the crystallinity of the diamond layer was evaluated.
0) Position corresponding to diffraction line on plane, 43.9 °, 75.4
A sharp diffraction line was observed at °, indicating that diamond crystals had been formed. Further, the surface property of the sample for crystallinity analysis was measured using a surface roughness meter (SE-3 manufactured by Kosaka Laboratory Co., Ltd.)
0D), Rz (ten-point average roughness) was 0.2 μm.

On a stainless steel substrate under the same conditions as in Experimental Example 1, an i-type layer was formed to a thickness of 0.1 μm and a p-type layer was further formed to a thickness of 0.005 μm to prepare a sample for crystallinity analysis. The crystallinity of the p-type layer was evaluated by RHEED (JEM-100SX manufactured by JEOL Ltd.).
It was found to be amorphous (including microcrystals).

(Experimental Example 2 and Comparative Experimental Example 2) Except that the flow rate of CH ₄ gas was changed to the value shown in Table 4 when forming the diamond layer, the same conditions as in Experimental Example 1 were used and two layers were formed. (Battery Nos. 2-1 to 2-3)
And battery No. Ratio 2-1 to 2). In the same manner as in Experimental Example 1, a 1 μm diamond layer was formed on a stainless steel substrate under the conditions shown in Table 4 to prepare a sample for crystallinity analysis.

The solar cells and the samples for crystallinity analysis prepared in Experimental Example 2 (Battery Nos. 2-1 to 3) and Comparative Experimental Example 2 (Battery Nos. 2-1 to 2) were used as Experimental Examples 1 and 2. The characteristics were evaluated in the same manner.

FIG. 4 shows the initial characteristics, thermal deterioration characteristics and stress deterioration characteristics of the solar cell, and the crystallinity and surface properties of the diamond layer.
Shown in The crystallinity was 43.9 ° corresponding to the diffraction line of the (111) plane of cubic diamond in X-ray diffraction.
Was determined from the half width of the diffraction line at the position. As can be seen from FIG. 4, the solar cell of the present invention (battery Nos. Ex. 1 and Ex. 2-1)
To 3) are solar cells (battery No. ratios 2-1 to 2-1) of comparative experimental examples.
In contrast to 2), it was found to have excellent characteristics, demonstrating the effect of the present invention.

(Experimental Example 3 and Comparative Experimental Example 3) In forming a diamond layer, the flow rate of PH ₃ / H ₂ gas was set as shown in Table 5.
2 were prepared under the same conditions as in Experimental Example 1 except that the values were changed to the values shown in FIG.
Nos. 1 to 3 and battery Nos. Ratio 3-1 to 2). In the same manner as in Experimental Example 1, a diamond layer was formed to a thickness of 1 μm on a stainless steel substrate under the conditions shown in Table 4 to prepare a sample for conductivity measurement.

The solar cells prepared in Experimental Example 3 (battery Nos. 3-1 to 3) and Comparative Experimental Example 3 (battery Nos. 3-1 to 2) were evaluated in the same manner as in Experimental Example 1. An evaluation was performed.

The samples for measuring conductivity prepared in Experimental Example 3 (Battery Nos. 3-1 to 3) and Comparative Experimental Example 3 (Battery Nos. 3-1 to 2) had chromium (chromium) on the surface of the diamond layer. Cr) was deposited in a size of 2 mm in diameter and 0.1 μm in thickness to form a chromium electrode. Then, the sample for conductivity measurement was set in a dark place, and a pA meter (manufactured by Yokogawa Hewlett Packard Co., Ltd.) 4140B), a voltage V is applied between the chromium electrode and the stainless steel substrate, a current I flowing between the two electrodes is measured, and the dark conductivity σd is calculated using the layer thickness D of the diamond layer by the following equation. I asked.

[0122]

[Outside]

The dark conductivity σd of the sample for crystallinity analysis (Battery No. 1) prepared in Experimental Example 1 was determined in the same procedure.

FIG. 5 shows the initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics of the solar cell, and the dark conductivity of the diamond layer.
As can be seen from FIG. 5, the solar cell of the present invention (Battery No. Ex. 1, Ex.
o. It was found that the composition had excellent characteristics with respect to the ratio 3-1 to 2), and the effect of the present invention was demonstrated.

[0125] In forming a (Experiment Example 4 and Comparative Example 4) diamond layer, PH ₃ / H ₂ gas instead using B ₂ H ₆ / H ₂ gas, the flow rate of B ₂ H ₆ / H ₂ gas Were changed to the values shown in Table 4, and two solar cells were prepared under the same conditions as in Experimental Example 1 (battery No. actual 4-1 to 3 and battery No. ratio 4-1 to 4-1). 2). In the same manner as in Experimental Example 3, a diamond layer was formed to a thickness of 1 μm on a stainless steel substrate under the conditions shown in Table 6 to prepare a sample for conductivity measurement.

The solar cells prepared in Experimental Example 4 (Battery Nos. 4-1 to 3) and Comparative Experimental Example 4 (Battery Nos. 4-1 to 2) were evaluated in the same manner as in Experimental Example 1. Evaluation was performed, and the conductivity measurement samples prepared in Experimental Example 4 (Battery Nos. 4-1 to 3) and Comparative Experimental Example 4 (Battery Nos. 4-1 to 2) were obtained in the same manner as in Experimental Example 3. The dark conductivity σd
I asked.

FIG. 6 shows the initial characteristics, thermal deterioration characteristics and stress deterioration characteristics of the solar cell, and the dark conductivity σd of the diamond layer. As can be seen from FIG. 6, the solar cell of the present invention (battery N
o. Examples 4-1 to 3) are solar cells (battery N) of a comparative example.
o. -Ratio 4-1 to 2), it was found to have excellent characteristics, demonstrating the effect of the present invention.

(Experimental Example 5 and Comparative Experimental Example 5) In forming a diamond layer, two layers were formed under the same conditions as in Experimental Example 1 except that the thickness of the diamond layer was changed to the value shown in Table 7. Of the solar cell (battery No.
Examples 5-1 to 3 and the battery No. Ratio 5-1 to 2), Experimental Example 1
The characteristics were evaluated in the same manner as described above.

FIG. 7 shows the initial characteristics, thermal deterioration characteristics and stress deterioration characteristics of the solar cell, and the thickness of the diamond layer. FIG.
As can be seen from FIG. 1, the solar cell of the present invention (battery No. 1;
Examples 5-1 to 3) were found to have excellent characteristics with respect to the solar cell (battery No. ratio 5-1 to 2) of the comparative experimental example, and the effect of the present invention was demonstrated.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[0131]

(Example 1) Under the same preparation conditions as in Experimental example 1, 2
A plurality of solar cells were prepared, and using these, a solar cell module was prepared, and a charger having a circuit configuration as shown in FIG. 8 was prepared. In FIG. 8, electric power generated by the solar cell module 801 is charged into a secondary battery (TN-1U manufactured by Toshiba Corporation) 804 via a backflow prevention diode 803. Reference numeral 802 denotes an overcharge prevention diode.

Comparative Example 1 Two solar cells were produced under the same production conditions as in Comparative Experimental Example 1, and a charger similar to that of Example 1 was produced using these solar cells.

The chargers produced in Example 1 and Comparative Example 1 were installed outdoors during daylight sunny weather, and the solar cell module 801 was installed.
Is charged in the secondary battery 804, and then the secondary batteries 804 charged by the chargers of Example 1 and Comparative Example 1 are used.
4 was put into a flashlight (K-67, manufactured by Toshiba Corporation) to turn on the light, and when the power of the secondary battery 804 was used up, the secondary battery was again charged using the chargers of Example 1 and Comparative Example 1. When the operation of charging the battery 804 was repeated,
The charger of No. 1 was able to light the flashlight about 1.3 times longer than the charger of Comparative Example 1, and the effect of the solar cell according to the present invention was demonstrated.

(Example 2) Diamond layer, n-type layer, i
Except that the mold layer and the p-type layer were made under the fabrication conditions shown in Table 6, two solar cells were fabricated in the same manner as in Experimental Example 1, and a charger similar to that of Example 1 was fabricated using these. When used in the same manner as in Example 1, the flashlight could be turned on for substantially the same time as in Example 1, and the effect of the solar cell according to the present invention was demonstrated.

Further, a diamond layer was formed to a thickness of 1 μm and an n-type layer was further formed to a thickness of 0.01 μm on a stainless steel substrate under the conditions shown in Tables 8 and 9 to prepare a sample for crystallinity analysis. When the crystallinity of the n-type layer was evaluated as in Example 1, it was found to be ring-shaped and amorphous (including microcrystals).

Further, Tables 8 and 9 were placed on a stainless steel substrate.
Under the conditions shown in (1), an i-type layer was formed to a thickness of 0.1 μm, and a p-type layer was further formed to a thickness of 0.005 μm to prepare a sample for crystallinity analysis. Upon evaluation, it was found to be ring-shaped and amorphous (including microcrystals).

(Example 3) Diamond layer, n-type layer, i
Two solar cells were produced in the same manner as in Experimental Example 1 except that the mold layer and the p-type layer were made under the production conditions shown in Tables 10 and 11, and the same charger as in Example 1 was produced using these. Was used in the same manner as in Example 1. As a result, the flashlight was able to be turned on for substantially the same time as in Example 1, and the effect of the solar cell according to the present invention was demonstrated.

On a stainless steel substrate under the conditions shown in Table 7, the i-type layer was 0.1 μm, and the n-type layer was 0.00 μm.
A sample for crystallinity analysis was formed by forming a film having a thickness of 5 μm, and the crystallinity of the n-type layer was evaluated in the same manner as in Experimental Example 1. As a result, it was found that the layer was ring-shaped and amorphous (including microcrystal). .

[0139]

【table】

[0140]

【table】

[0141]

【table】

[0142]

【table】

[0143]

【table】

[0144]

【table】

[0145]

【table】

[0146]

【table】

[0147]

【table】

[0148]

【table】

[0149]

【table】

[0150]

According to the solar cell having the diamond layer of the present invention, the conversion efficiency is improved and the deterioration with time of the characteristics is reduced. As a result, the characteristics of the solar cell were remarkably improved.

Further, the solar cell having the diamond layer of the present invention has significantly improved production yield as compared with the conventional solar cell.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a layer configuration of a solar cell of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a layer configuration of a conventional solar cell.

FIG. 3 is a schematic explanatory view of a manufacturing apparatus by a glow discharge method using μW as an example of an apparatus for manufacturing a solar cell of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the crystallinity and surface properties of the diamond layer of the present invention and the initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics of a solar cell.

FIG. 5 is an explanatory diagram showing a relationship between the dark conductivity of the diamond layer of the present invention and initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics.

FIG. 6 is an explanatory diagram showing a relationship between the dark conductivity of the diamond layer of the present invention and initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics.

FIG. 7 is an explanatory diagram showing the relationship between the thickness of the diamond layer of the present invention and the initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics of a solar cell.

FIG. 8 is an electric circuit diagram of a charger using the solar cell of the present invention.

[Explanation of symbols]

 101 conductive substrate 102 diamond layer 103 n-type layer (or p-type layer) 104 i-type layer 105 p-type layer (or n-type layer) 106 transparent electrode 201 conductive substrate 202 lower electrode 203 n-type layer (or p-type layer) ) 204 i-type layer 205 p-type layer (or n-type layer) 206 transparent electrode 1000 μW film forming apparatus by glow discharge decomposition method 1001 deposition chamber 1002 dielectric window 1003 gas introduction tube 1004 substrate 1005 heating heater 1006 vacuum gauge 1007 conductance valve 1008 Auxiliary valve 1009 Leak valve 1010 Wave guide unit 1011 DC power supply 1020 Source gas supply device 1021 to 1025 Mass flow controller 1031 to 1035 Gas inflow valve 1041 to 1045 Gas outflow valve 1051 to 1055 Bar of source gas cylinder Bed 1061-1065 pressure regulator 1071-1075 raw material gas cylinder 801 photovoltaic modules 802 overcharge preventing diode 803 reverse current prevention diode 804 secondary batteries

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuzo Koda Canon Inc. 3- 30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor Yasushi Fujioka 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inside (72) Inventor Mitsuyuki Niwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-64-77973 (JP, A) JP-A-2-96382 ( JP, A) JP-A-3-62973 (JP, A) JP-A-63-169769 (JP, A)

Claims (1)

(57) [Claims] 1. A solar cell comprising a semiconductor substrate comprising a p-type layer made of a non-single crystal containing Si, an i-type layer as an active layer, and an n-type layer stacked on a conductive substrate. At least one of the p-type layer and the n-type layer contains carbon atoms, and the surface between the conductive substrate and the semiconductor layer has irregularities, and the polyhedral polyhedron has a valence electron controlling agent. Crystal
A solar cell comprising a diffusion prevention layer comprising an earmond layer .