JPH04214678A - Solar battery - Google Patents

Abstract

PURPOSE:To provide a solar battery which has no deterioration in characteristic due to etching residue, no influence of residual fine particles, no diffusion of electrode material into a semiconductor layer, no deterioration in characteristic due to distortion of a substrate, and a high optoelectric transducing efficiency. CONSTITUTION:In a solar battery which is built up by depositing a non-single crystalline silicon-made p-type semiconductor layer 105, i-type semiconductor layer which serves for an active layer and n-type semiconductor layer 103 on a conductive substrate 101, a diamond layer 102 which has the uneven surface that contains a valence electron control agent is deposited between the conductive substrate 101 and the semiconductor layers.

Description

[Detailed description of the invention]

0001

FIELD OF APPLICATION This invention relates to high efficiency solar cells.

0002

[Prior art] In a solar cell using a light reflective substrate,
A method of improving the efficiency by forming the light reflecting surface as a rough surface with unevenness and increasing the path length of light with a low absorption wavelength is disclosed in, for example, US Pat. No. 4,126,150 (
Applicant, RCA), and disclosed in Japanese Patent Application Laid-Open No. 56-15227.
This is also stated in Publication No. 6 (applicant, Teijin). Further, in Japanese Patent Application Laid-Open No. 59-104185 (applicant: Exxon Research and Engineering Company), the optical effects of a roughened substrate are detailed.

[0003] As a method for forming unevenness, Japanese Patent Application Laid-Open No. 54-15
3588 (applicant: National Patent Development Corporation), the wet etching method was disclosed in Japanese Patent Application Laid-open No. 159383/1983 (Applicant: National Patent Development Corporation).
The sandblasting method and co-evaporation method were published in Japanese Unexamined Patent Application Publication No. 59-14 (Applicant, Energy Conversion Devices).
No. 682 (assigned by Electrolytic Foil Industry Co., Ltd., et al.) discloses surface roughening of aluminum by direct current electrolytic etching or chemical etching.

[0004] Furthermore, in JP-A-63-169769, a solar cell is formed 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]

[Problems with the Prior Art] The conventional method for forming irregularities on the surface of a substrate has various problems when forming a solar cell.

For example, when etching with a solution such as DC electrolytic etching or chemical etching, etching residue of the substrate is generated on the surface of the substrate. Therefore, when a semiconductor layer is deposited on such a substrate, etching residues diffuse into the semiconductor layer, degrading the characteristics of the solar cell. Also,
Since such etching residue has weak adhesion to the substrate, the semiconductor layer deposited thereon is likely to peel off, making it difficult to deposit a solar cell with uniform characteristics.

[0007] Furthermore, in the sandblasting method, fine particles are sprayed onto a substrate to form irregularities, so the sprayed fine particles remain on the substrate, and the fine particles may become the core of abnormal growth of the semiconductor layer. Further, since the fine particles have poor adhesion to the substrate, there is also the problem that the semiconductor layer deposited thereon tends to peel off. Furthermore, in the sandblasting method, fine particles are sprayed to form irregularities on the substrate surface, which may cause distortion in the substrate, which may relax over time and cause distortion in the deposited semiconductor layer. This led to peeling of the semiconductor layer and deterioration of electrical characteristics.

Furthermore, when forming irregularities on the surface of a substrate by co-evaporation, there is a problem that at least two types of raw materials are deposited at the same time, which tends to cause non-uniformity in the deposited film. There is a problem in that solar cells formed by deposition tend to have uneven characteristics.

Furthermore, the above-mentioned Japanese Patent Application Laid-Open No. 63-169769
In the example described in the publication in which a diamond thin film is used as a substrate of a solar cell, a transparent electrode is formed on the diamond thin film, and a semiconductor layer is laminated on the transparent electrode to form a solar cell. In such a layered structure, diamond is used as a high-resistance substrate instead of a glass substrate. Therefore, a transparent electrode was provided on the diamond thin film. In this conventional example, the excellent adhesion between the diamond thin film and the semiconductor layer was not utilized. Further, there was a problem that constituent elements of the transparent electrode diffused into the semiconductor layer.

0010

OBJECTS OF THE INVENTION It is an object of the present invention to solve the problems of the prior art.

[0011] That is, an object of the present invention is to provide a solar cell in which the solar cell characteristics are not deteriorated by etching residue.

Another object of the present invention is to provide a solar cell that is free from the effects of residual fine particles produced on a substrate by sandblasting or the like. Furthermore, it is an object of the present invention to provide a solar cell in which characteristics do not deteriorate due to relaxation of substrate strain over time due to collisions of fine particles.

A further object of the present invention is to provide a solar cell that is free from the effects of diffusion of electrode material into the semiconductor layer.

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

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

[0016]

[Means for solving the problems] The solar cell of the present invention is
In order to solve the above problems and achieve the objective, a p layer made of non-single crystal Si and an i layer as an active layer are formed on a conductive substrate.
In a solar cell configured by laminating semiconductor layers of a layer and an n layer, a diamond layer having an uneven surface and containing a valence electron control agent is provided between the conductive substrate and the semiconductor layer. It is characterized by intervening.

FIG. 1 is a schematic illustration of an example of the solar cell of the present invention.

In FIG. 1, the solar cell of the present invention includes a conductive substrate 101, a diamond layer 102, an n-type layer 103, an i
It is composed of a type layer 104, a p-type layer 105, and a transparent electrode 106.

Each layer constituting the solar cell of the present invention will be described in detail below.

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

[0021] As the electrically insulating material, polyester,
Films or sheets of synthetic resins such as polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, glass, ceramics, paper, etc. are usually used. It is desirable that at least one surface of these electrically insulating materials be subjected to conductive treatment, and that another layer be provided on the conductive treated surface side.

For example, in the case of glass, N is applied to the surface of the glass.
iCr, Al, Cr, Mo, Au, Ir, Nb, Ta,
V, Ti, Pt, Pd, In2O3, SnO2, ITO
Conductivity is imparted by providing a thin film made of (In2O3+SnO2), etc., or if it is a synthetic resin film such as polyester film, NiCr, Al, A
g, Pb, Zn, Ni, Au, Cr, Mo, Ir, Nb
, Ta, V, Ti, Pt, etc. are provided on the surface by vacuum evaporation, electron beam evaporation, sputtering, etc., or the surface is laminated with the above metal to impart conductivity to the surface. .

[0023] The thickness of the substrate is appropriately determined so that the desired solar cell can be formed, but due to manufacturing and handling considerations,
From the viewpoint of mechanical strength, etc., the thickness is usually 10 μm or more.

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

In the present invention, the diamond layer is formed of polycrystalline diamond. Polycrystalline diamonds include smooth polyhedral shapes, skeleton shapes, acicular crystal aggregate shapes, etc., but smooth polyhedral polycrystalline diamonds are suitable for the present invention.

The diamond layer formed of smooth polyhedral polycrystalline diamond as described above has irregularities on its surface.

[0027] Due to this unevenness, the semiconductor layer provided on the diamond layer is formed in the same shape as the diamond layer, so that the surface of the solar cell also has a smooth polyhedral shape having the same unevenness as the diamond layer.

Therefore, even if the light incident on the solar cell of the present invention is incident on the surface of a smooth polyhedron at an angle larger than the critical angle and causes total internal reflection, the totally reflected light is transferred to the surface of other smooth polyhedrons. Since it can be introduced into the solar cell more effectively, the incident light can be used effectively.

[0029] Furthermore, since the light introduced into the solar cell travels in the diagonal direction with respect to the thickness direction within the solar cell,
The effective length of the semiconductor layer for absorbing light energy and generating carriers can be set to be greater than the layer thickness of the semiconductor layer.

As a result, the amount of light absorbed within the solar cell increases, and the conversion efficiency of the solar cell increases. In particular, polycrystalline diamond in the shape of a smooth polyhedron has a polyhedral surface that is almost a mirror surface, and has better surface properties than the uneven microscopic surfaces of the prior art. As a result, the light confinement effect within the solar cell becomes better than before, and the conversion efficiency of the solar cell improves.

Furthermore, since the smooth polyhedral polycrystalline diamond layer has a very dense structure, it is possible to prevent metal from diffusing from the conductive substrate into the semiconductor layer. In addition, since polycrystalline diamond has a flexible crystal interface structurally, it can alleviate strain during solar cell production. As a result, it is possible to prevent the solar cell from deteriorating over time due to diffusion of impurities from the substrate or distortion.

A diamond layer suitable for the present invention has a layer thickness of 0.1 μm or more and 5 μm or less, and a surface area of In order to effectively utilize the incident light, the unevenness of
．． It is desirable that it is between 05S and 1S.

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

Furthermore, hydrogen is contained within the diamond layer, particularly at the polycrystalline interface. A suitable amount of hydrogen content is 1 to 5 at% for alleviating strain.

In addition, since the diamond layer of the present invention is provided between the conductive substrate and the semiconductor layer, it is necessary that the diamond layer has low resistance. A preferable dark conductivity of the diamond layer is 0.1 S/cm or more. The amount of impurity doping required to achieve such dark conductivity is 1 at % to 10 at %. If the amount of impurity doping is more than 10 at %, the diamond layer may not be composed of smooth polyhedral crystals.

In the present invention, when the impurity contained in the diamond layer is n-type,
Group elements are suitable, in particular N, P, As, Sb, Bi. Further, in the case of p-type, elements of Group 3 of the periodic table, particularly B, Al, Ga, In, and Tl are suitable.

[0037] In the present invention, starting materials that can be effectively used for introducing group 3 atoms include B2H6, B4H10, and B5H9, specifically for introducing boron atoms.
, B5H11, B6H10, B6H12, B6H14, etc., boron halides such as BF3, BCl3, BBr3, etc.;
3, GaCl3, InCl3, TlCl3, etc. can also be mentioned.

In the present invention, the starting materials that are effectively used for introducing Group 5 atoms are, specifically for introducing phosphorus atoms, hydrogenated phosphorus such as PH3 and P2H4, PH4
I, PF3, PF5, PCl3, PCl5, PBr3,
Examples include phosphorus halides such as PBr5 and PI3. In addition, AsH3, AsF3, AsCl3, AsBr3, A
sF5, SbH3, SbF3, SbF5, SbCl3,
Mention may also be made of SbCl5, BiH3, BiCl3, BiBr3, etc.

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 these methods, the microwave plasma CVD method is particularly suitable in terms of high deposition rate and high raw material gas utilization efficiency.

When the diamond layer of 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 the raw material gas include saturated hydrocarbons having 1 to 4 carbon atoms, and saturated hydrocarbons having 2 to 4 carbon atoms.
Examples include ethylene hydrocarbons, acetylene hydrocarbons having 2 to 3 carbon atoms, and the like.

Specifically, examples of saturated hydrocarbons include methane (CH4), ethane (C2H6), and propane (C3H6).
8), n-butane (n-C4H10), pentane (C5
H12), ethylene hydrocarbons include ethylene (C
2H4), propylene (C3H6), butene-1 (C4
H8), butene-2 (C4H8), isobutylene (C4
Examples of the acetylene hydrocarbons include acetylene (C2H2), methylacetylene (C3H4), and butyne (C4H6).

[0044] Also included are hydrocarbons containing halogen atoms. For example, CH3F, CH2F2, CH3Cl, C
H2Cl2, CF4, C2H5F, C2H4F2, C2
Examples include H4FCl, C2H2F2, C2H2FCl, and the like.

Furthermore, in forming the diamond layer of the present invention, hydrogen gas may be added in addition to the raw material gas for introducing carbon atoms.

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

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

When depositing the diamond layer of the present invention,
It is necessary to prevent gas phase reactions between the carbon atom introduction gases decomposed in the plasma. Therefore, it is desirable that the internal pressure at the time of plasma generation be 1 mTorr to 50 mTorr.

Furthermore, the carbon atom introduction gas and the hydrogen gas must be sufficiently decomposed or activated within the plasma. For this purpose, the power input into the reaction space is 0 relative to the flow rate of the gas for introducing carbon atoms and the volume of the reaction space.
．． It is desirable to set it to 01-1W/sccm*cm3.

In addition, the substrate temperature is an important factor when the carbon atom introduction gas decomposed by the plasma in the reaction space and the hydrogen gas react on the substrate to form the diamond layer of the present invention. In the invention, the temperature is preferably 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 for the n-type layer, a silicon-containing non-single crystal semiconductor is suitable, particularly hydrogenated and/or halogenated amorphous silicon (including microcrystals). Furthermore, if the material is more limited, microcrystalline silicon among amorphous silicones is most suitable.

The grain size of microcrystalline silicon crystals is preferably 50 Å to 500 Å, and optimally 10 Å to 500 Å.
It is 0 Å to 300 Å.

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

In the case of amorphous silicon, the content of hydrogen and/or halogen atoms is preferably 1 to 40
at%, optimally from 5 to 20 at%.

Furthermore, as the additive contained in the n-type layer, elements of group 5A of the periodic table are suitable. Among them, P, N, As, and Sb are particularly suitable.

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

Regarding the electrical characteristics of the n-type layer, it is preferable that the activation energy be 0.2 eV or less, and optimally 0.1 eV or less within the above-mentioned conditions. Further, the specific resistance is preferably 10 Ωcm or less, and optimally 1 Ωcm or less.

(I-type layer) In the present invention, the i-type layer is an important layer that generates and transports carriers in response to irradiated light. A non-single crystal material containing silicon atoms suitable for the i-type layer includes amorphous silicon (microcrystalline silicon). Among amorphous silicones, hydrogenated amorphous silicon and hydrogenated and/or halogenated amorphous silicon are particularly suitable.

Further, the content of hydrogen or halogen contained in amorphous silicon is very important in order to reduce localized levels and maintain high quality electrical characteristics. The bonding state between the hydrogen atom and the silicon atom is preferably such that one hydrogen atom is bonded to the silicon atom. The same applies to the bonding state between halogen atoms and silicon atoms.

[0061] The sum of the contents of hydrogen atoms and halogen atoms is preferably 1 at% to 40 at%, most preferably 5 at% to 20 at%.

Furthermore, the thickness of the i-type layer is an important parameter that influences the characteristics of the photovoltaic device of the present invention. The 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, taking into account the absorption coefficient of the i-type layer and the spectrum of incident light such as sunlight.

(P-type layer) In the present invention, the p-type layer is an important layer that controls the electromotive force and photocurrent of the photovoltaic element.

As the material for the p-type layer, a silicon-containing non-single crystal semiconductor is suitable, and hydrogenated and/or halogenated amorphous silicon (including microcrystalline silicon) is particularly suitable. Furthermore, if the material is more limited, microcrystalline silicon among amorphous silicones is most suitable.

The grain size of the microcrystalline silicon is preferably 30 Å to 200 Å, optimally 30 Å to 1
00 Å.

Further, the content of hydrogen and/or halogen atoms is preferably 1 to 10 at %, and optimally 1 to 7 at % in the case of microcrystalline silicon. In the case of amorphous silicon, the content of hydrogen and/or halogen atoms is preferably 1 to 40 at%, optimally 5 to 20 at%.

Furthermore, as the additive contained in the p-type layer, elements of Group 3A of the periodic table are 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%, most preferably 5 at% to 10 at%.

Regarding the electrical characteristics of the p-type layer, within each of the above conditions, activation energy is preferably 0.2 eV or less, and optimally 0.1 eV or less. Further, the specific resistance is preferably 10 Ωcm or less, and optimally 1 Ωcm or less.

The thickness of the p-type layer is preferably 10 Å to 50 Å.
0 Å, optimally between 50 Å and 300 Å.

(Transparent electrode) The transparent electrode used in the present invention must have a light transmittance of 85% or more in order to efficiently absorb light from a light source such as the sun or a white fluorescent lamp into the semiconductor layer. Further, it is desirable that the sheet resistance value is 100Ω or less so as not to become a resistance component electrically with respect to the output of the solar cell. Materials with such characteristics include, for example, SnO2 and In2O.
3. ZnO, CdO, Cd2SnO4, ITO (In2
metal oxides such as O3+SnO2), Au, Al, C
Examples include metal thin films formed by forming extremely thin, translucent metals such as u.

Examples of manufacturing methods include resistance heating evaporation, electron beam heating evaporation, sputtering,
A spray method or the like can be used, and the method is appropriately selected as desired.

In the present invention, the p-type layer, n-type layer, and i-type layer are formed by, for example, direct current plasma CVD, high frequency plasma CVD, etc.
It is suitable to form by the D method, microwave plasma CVD method, or the like.

[0075] The following gases may be mentioned as raw material gases suitable for the plasma CVD method.

The raw material gas for supplying Si used in the present invention includes SiH4, Si2H6, Si3H8,
Silicon hydride (silanes) in a gaseous state or that can be gasified, such as Si4H10, can be effectively used. In particular, SiH4, Si2H6 is preferred.

Many halogen compounds are effective as the raw material gas for introducing halogen atoms used in the present invention, such as halogen gases, halides, interhalogen compounds, halogen-substituted silane derivatives, and other gases. Preferred examples include halogen compounds that can be converted into gas or gasified.

Furthermore, silicon compounds containing halogen atoms, which are in a gaseous state or can be gasified and which have silicon atoms and halogen atoms as constituent elements, can also be mentioned as effective in the present invention.

[0079] Specific examples of halogen compounds that can be suitably used in the present invention include halogen gases such as fluorine, chlorine, bromine, and iodine, BrF, ClF, ClF3, and BrF.
5, BrF3, IF3, IF7, ICl, IBr, and other interhalogen compounds.

[0080] Examples of silicon compounds containing halogen atoms, so-called silane derivatives substituted with halogen atoms include, for example, SiF4, Si2F6, SiCl4, SiB
Preferred examples include silicon halides such as r4.

[0081] Such a silicon compound containing a halogen atom may be employed and introduced into the characteristic chamber of the present invention by the plasma CVD 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 raw material gases for introducing halogen atoms, but in addition, HF, HCl, HBr, HI Hydrogen halides such as SiH2F2, SiH2I2, SiH
2Cl2, SiHCl3, SiH2Br2, SiHBr
Gaseous or gasifiable halides having a hydrogen atom as one of their constituents, such as halogen-substituted silicon hydrides such as No. 3, can also be mentioned as effective starting materials.

These halides containing hydrogen atoms are
Hydrogen atoms, which are extremely effective in controlling electrical or photoelectric properties, are also introduced into the layer formed during layer formation, so hydrogen atoms are preferably used as raw materials for halogen introduction in the present invention. be done.

When the glow discharge method is used to form a layer containing Group 3 atoms or Group 5 atoms, the starting material that becomes the raw material gas for forming the layer is one of the above-mentioned starting materials for Si. A starting material for introducing Group 3 atoms or Group 5 atoms is added to those appropriately selected from among them. The starting material for introducing such Group 3 atoms or Group 5 atoms may be a gaseous substance or a gasified substance containing Group 3 atoms or Group 5 atoms as constituent atoms. , any one may be used.

[0085] In the present invention, starting materials that can be effectively used for introducing a group 3 atom include B2H6, B4H10, and B5H9, specifically for introducing boron atoms.
, B5H11, B6H10, B6H12, B6H14, etc., boron halides such as BF3, BCl3, BBr3, etc.;
3, GaCl3, InCl3, TlCl3, etc. can also be mentioned.

In the present invention, the starting materials effectively used for introducing Group 5 atoms include phosphorus hydrides such as PH3 and P2H4, and PH4I for introducing phosphorus atoms.
, PF3, PF5, PCl3, PCl5, PBr3, P
Examples include phosphorus halides such as Br5 and PI3. In addition, AsH3, AsF3, AsCl3, AsBr3, As
F5, SbH3, SbF3, SbF5, SbCl3, S
Mention may also be made of bCl5, BiH3, BiCl3, BiBr3, etc.

(Experimental Examples) The present invention will be explained in more detail using experimental examples below, 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 an apparatus for producing solar cells by the μW glow discharge decomposition method, which includes a raw material gas supply device 1020 and a deposition device 1000.

Gas cylinders 1071 to 1075 in the figure are sealed with raw material gas for forming each layer of the present invention, and 1071 is SiH4 gas (purity 99.99).
%) cylinder, 1072 is H2 gas (purity 99.9999
%) cylinder, 1073 is CH4 gas (purity 99.999
%) cylinder, 1074 is B2H6 gas diluted to 10% with H2 gas (purity 99.999%, hereinafter referred to as "B2H6/
(abbreviated as "H2") cylinder, 1075 is H2 gas.
% diluted PH3 gas (purity 99.999%, hereinafter abbreviated as "PH3/H2") cylinder. Moreover, when attaching the gas cylinders 1071 to 1075, each gas is introduced into the gas piping of the inflow valves 1031 to 1035 from the valves 1051 to 1055 in advance.

In the figure, 1004 is a substrate made of stainless steel (SUS430BA), 100 mm square and 0.25 mm thick.
It is made of aluminum and has a mirror finish on its surface.

First, SiH4 gas is supplied from the gas cylinder 1071, H2 gas is supplied from the gas cylinder 1072, and the gas cylinder 10
CH4 gas from 73, B2H6 from gas cylinder 1074
/H2 gas, PH3/H2 gas from gas cylinder 1075 is introduced by opening valves 1051 to 1055, and each gas pressure is adjusted to 2Kg/c by pressure regulators 1061 to 1065.
Adjusted to m2.

Next, confirm that the inflow valves 1031 to 1035 and the leak valve 1009 of the deposition chamber 1001 are closed, and also confirm 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 piping are evacuated by a vacuum pump (not shown), and the vacuum gauge 1006 reads approximately 1×10 −
When the temperature reached 4 Torr, the auxiliary valve 1008 and the outflow valves 1041 to 1045 were closed.

Next, the inflow valves 1031 to 1035 are gradually opened to supply each gas to the mass flow controller 1.
It was introduced between 021 and 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 the diamond layer, the substrate 10
04 is heated to 400°C by a heating heater 1005,
By gradually opening the outflow valves 1042, 1043, 1045 and the auxiliary valve 1008, H2 gas, CH4 gas, P
H3/H2 gas is introduced into the deposition chamber 1 through the gas introduction pipe 1003.
001. At this time, the H2 gas flow rate is 500
sccm, CH4 gas flow rate is 5 sccm, PH3/H2
Each mass flow controller 1022, 1023, and 1025 was adjusted so that the gas flow rate was 2.5 sccm. The pressure inside the deposition chamber 1001 is set to 20 mTorr by adjusting the conductance valve 10 while watching the vacuum gauge 1006.
Adjusted the aperture of 07. Next, a DC bias of -100 V was applied to the substrate 1004 with respect to the deposition chamber 1001 by a DC power supply 1011. Thereafter, the power of a μW power source (not shown) is set to 0.5 W/cm3, and the deposition chamber 100 is
μW power is introduced into 01 to generate μW glow discharge, and formation of a diamond layer is started on the substrate 1004. When a diamond layer with a thickness of 1 μm is formed, the μW glow discharge is stopped, and the output of the DC power source 1011 is turned off. Then, the outflow valves 1042, 1043, 1045 and the auxiliary valve 1008 were closed to stop the gas from flowing into the deposition chamber 1001, and the formation of the diamond layer was completed.

Next, to form the n-type layer, the substrate 100 is
4 is heated to 280°C by a heating heater 1005, and the outflow valves 1041, 1042, 1045 and the auxiliary valve 1008 are gradually opened, and SiH4 gas, H2 gas, P
H3/H2 gas is introduced into the deposition chamber 1 through the gas introduction pipe 1003.
001. At this time, the SiH4 gas flow rate was 5
The mass flow controllers 1021, 1022, and 1025 were adjusted so that the H2 gas flow rate was 5 sccm, the PH3/H2 gas flow rate was 5 sccm, and the PH3/H2 gas flow rate was 5 sccm. The pressure inside the deposition chamber 1001 is set to 10 mTorr by adjusting the conductance valve 10 while watching the vacuum gauge 1006.
Adjusted the aperture of 07. Next, a DC bias of -50 V was applied to the deposition chamber 1001 by the DC power supply 1011 to the substrate 1004 . After that, the power of a μW power supply (not shown) is set to 0.02 W/cm3, and the deposition chamber 100 is
A μW power is introduced into the diamond layer to generate a μW glow discharge, and the formation of an n-type layer on the diamond layer is started until the layer thickness is 0.0.
After forming an n-type layer of 0.01 μm, the μW glow discharge is stopped, the output of the DC power supply 1011 is cut off, and the outflow valves 1041, 1042, 1045 and the auxiliary valve 1008 are turned off.
was closed to stop the gas from flowing into the deposition chamber 1001, and the formation of the n-type layer was completed.

Next, to form the i-type layer, the substrate 100 is
4 is heated to 280° C. by a heating heater 1005, and the outflow valves 1041, 1042 and the auxiliary valve 1008 are gradually opened to introduce SiH4 gas and H2 gas into the gas inlet pipe 1.
003 into the deposition chamber 1001. At this time, the SiH4 gas flow rate is 50 sccm, and the H2 gas flow rate is 1
The mass flow controllers 1021 and 1022 were adjusted so that the flow rate was 00 sccm. The pressure inside the deposition chamber 1001 was set to 10 mTorr using a vacuum gauge 1006.
The opening of the conductance valve 1007 was adjusted while watching. Next, the board 1004 is connected to the DC power supply 1011.
A DC bias of -50 V was applied to the deposition chamber 1001. After that, the power of the μW power supply (not shown) is increased to 0.15W/
cm3, and introduce μW power into the deposition chamber 1001 through a waveguide (not shown), waveguide portion 1010, and dielectric window 1002 to generate μW glow discharge and form an i-type layer on the n-type layer. After forming an i-type layer with a thickness of 0.4 μm, the μW glow discharge was stopped and the output of the DC power supply 1011 was turned off, thereby completing the formation of the i-type layer.

Next, in order to form a p-type layer, the substrate 100 is
4 was heated to 280°C by the heating heater 1005, and the outflow valve 1044 was gradually opened to release SiH4 gas and H2 gas.
Gas, B2H6/H2 gas, was introduced into the deposition chamber 1001 through the gas introduction pipe 1003 to form a 5A group gas. At this time, Si
H4 gas flow rate is 5sccm, H2 gas flow rate is 500sc
cm, and each mass flow controller 1021, 1022 so that the B2H6/H2 gas flow rate is 5 sccm.
, 1024. The pressure inside the deposition chamber 1001 is 2
The opening of the conductance valve 1007 was adjusted while watching the vacuum gauge 1006 so that the pressure was 0 mTorr. next,
A substrate 1004 is connected to a deposition chamber 100 by a DC power supply 1011.
A DC bias of -70v was applied to the voltage. Thereafter, the power of a μW power source (not shown) is set to 0.5 W/cm3, and the waveguide, waveguide section 1010, and dielectric window 100 (not shown) are
2, μW power is introduced into the deposition chamber 1001 through μW
A glow discharge is generated and the formation of a p-type layer is started on the i-type layer, and when the p-type layer with a layer thickness of 0.005 μm is formed, μ
Stop the W glow discharge, turn off the output of the DC power supply 1011,
Further, the outflow valves 1041, 1042, 1044 and the auxiliary valve 1008 were closed to stop the gas from flowing into the deposition chamber 1001, and the formation of the p-type layer was completed.

[0100] The above solar cell production conditions are shown in Tables 1 and 2.
, shown in Table 3.

[0101] Needless to say, when forming each layer, the outflow valves 1041 to 1045 for gases other than the necessary gases are completely closed. 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 is closed.
7 is fully opened and the system is evacuated to a high vacuum as necessary.

[0102] ITO (In2O3+SnO2) was evaporated to a thickness of 0.085 μm as a transparent electrode on the p-type layer of the solar cell prepared by a known method, and A as a current collector electrode.
1 was deposited to a thickness of 2 μm using a known method to create a solar cell. Two solar cells were created by performing the same operation (Battery No. Real-1).

(Comparative Experiment Example 1) The substrate 1004 was heated to 350° C., and a thin silver film of 0.45 μm was deposited on the surface of the substrate 1004 by sputtering.
After further depositing a ZnO thin film of 2 μm to form a lower electrode, an n-type layer, an i-type layer, a p-type layer, and a transparent layer were formed on the lower electrode under the same conditions as in Experimental Example 1, except that no diamond layer was formed. Electrodes and current collecting electrodes were formed to create 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.

[0105] The initial characteristics are those of Experimental Example 1 (Battery No. 1)
and each 2 created in Comparative Experiment Example 1 (Battery No. Ratio 1)
AM-1.5 (100mW/cm2)
It was installed under light irradiation and evaluated by measuring the photoelectric conversion efficiency. As a result of the characteristic evaluation, the photoelectric conversion efficiency of the solar cell of Experimental Example 1 (Battery No. Actual 1) was 1.2 times better on average than that of Comparative Experimental Example (Battery No. Ratio 1).

[0106] Thermal deterioration characteristics were determined using Experimental Example 1 (Battery No. 1).
) and Comparative Experiment Example 1 (Battery No. Ratio 1), one solar cell each was left in a constant temperature dryer (DV-41 manufactured by Yamato Scientific Co., Ltd.) set at 100 ° C. for 1 hour,
Next, a refrigerator (manufactured by Hitachi, Ltd. R) set at 5℃
-107W) for 1 hour was repeated 10 times.
0 mW/cm2) was installed under light irradiation, and the photoelectric conversion efficiency was measured and evaluated. As a result of characteristic evaluation, comparative experiment example (Battery N
o. Compared to Ratio 1), the solar cell of Experimental Example 1 (Battery No. 1) had a photoelectric conversion efficiency that was 1.4 times better.

[0107] Stress deterioration characteristics were prepared using Experimental Example 1 (Battery No. Actual 1) and Comparative Experiment Example 1 (Battery No. Ratio 1). With the battery facing the stainless steel substrate inside, the radius of curvature is 54.
After repeating the operation 50 times to bend the solar cell to 50 mm and then return it to a flat surface, the solar cell was
．． 5 (100 mW/cm2) light irradiation, and the photoelectric conversion efficiency was measured and evaluated. As a result of the characteristic evaluation, experimental example 1 (battery No. ratio 1) was compared to comparative experimental example (battery No. 1).
The solar cell of Example 1) had a photoelectric conversion efficiency that was 1.3 times better.

[0108] In addition, 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 crystallinity analysis.
When the crystallinity of the diamond layer was evaluated by RAD-3b type), it was found that (111) and (2
20) Position corresponding to the diffraction line of the plane, 43.9°, 75.
A sharp diffraction line was observed at 4°, indicating that diamond crystals were formed. In addition, the surface properties of the sample for crystallinity analysis were measured using a surface roughness meter (SE-
30D), Rz (10-point average roughness)
was 0.2 μm.

[0109] Also, on a stainless steel substrate, under the same conditions as in Experimental Example 1, an i-type layer was formed with a thickness of 0.1 μm, and a p-type layer was formed with a thickness of 0.1 μm.
．． A sample for crystallinity analysis was prepared by forming a film with a thickness of 0.005 μm, and the crystallinity of the p-type layer was evaluated using RHEED (JEM-100SX manufactured by JEOL Ltd.).
It was found to be amorphous (including microcrystals).

(Experimental Example 2 and Comparative Experimental Example 2) Two diamond layers were prepared under the same conditions as in Experimental Example 1, except that the flow rate of CH4 gas was changed to the value shown in Table 4. Solar cells were created (Battery No. 2-1 to 3)
and battery no. ratio 2-1 to 2). Similarly to Experimental Example 1, a 1 μm diamond layer was formed on a stainless steel substrate under the conditions shown in Table 2 to prepare a sample for crystallinity analysis.

[0111] The solar cells and samples for crystallinity analysis prepared in Experimental Example 2 (Battery No. 2-1 to 3) and Comparative Experimental Example 2 (Battery No. Ratio 2-1 to 2-2) were compared with Experimental Example 1. Characteristics were evaluated in a similar manner.

FIG. 4 shows the initial characteristics, thermal deterioration characteristics, stress deterioration characteristics of the solar cell, and the crystallinity and surface properties of the diamond layer.
Shown below. In addition, the crystallinity is 43.9° in X-ray diffraction, which corresponds to the diffraction line of the (111) plane of cubic diamond.
It was determined by the half-width of the diffraction line at the position. As can be seen from FIG. 4, the solar cells of the present invention (Battery No. 1, No. 2-1)
~3) is the solar cell of the comparative experiment example (battery No. ratio 2-1~
2), it was found that it had excellent properties, and the effect of the present invention was verified.

(Experimental Example 3 and Comparative Experimental Example 3) When forming the diamond layer, each of Two solar cells were created (Battery No. Real 3-
1 to 3 and battery no. Ratio 3-1 to 2). Further, in the same manner as in Experimental Example 1, a 1 μm diamond layer was formed on a stainless steel substrate under the formation conditions shown in Table 4 to prepare a sample for conductivity measurement.

[0114] The solar cells produced in Experimental Example 3 (Battery No. Ratio 3-1 to 3) and Comparative Experiment Example 3 (Battery No. Ratio 3-1 to 3-2) were tested in the same manner as in Experimental Example 1 to determine their characteristics. We conducted an evaluation.

[0115] The conductivity measurement samples prepared in Experimental Example 3 (Battery No. Ratio 3-1 to 3) and Comparative Experiment Example 3 (Battery No. Ratio 3-1 to 3-2) had chromium ( After forming a chromium electrode by vapor-depositing Cr) with a diameter of 2 mm and a thickness of 0.1 μm, the sample for conductivity measurement was placed in a dark place, and a pA meter (manufactured by Yokogawa Hewlett-Packard Co., Ltd.) was used. 4140B), apply a voltage V between the chrome electrode and the stainless steel substrate, measure the current I flowing between both electrodes, and calculate the dark conductivity σd using the following formula using the layer thickness D of the diamond layer. I asked for it.

[0116]

[Outside]

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

FIG. 5 shows the initial characteristics, thermal deterioration characteristics, stress deterioration characteristics of the solar cell, and the dark conductivity of the diamond layer. As shown in FIG.
．． It was found that it had excellent properties compared to ratios 3-1 to 3-2), demonstrating the effect of the present invention.

(Experimental Example 4 and Comparative Experimental Example 4) When forming a diamond layer, B was used instead of PH3/H2 gas.
Two solar cells were each produced under the same production conditions as in Experimental Example 1, except that 2H6/H2 gas was used and the flow rate of B2H6/H2 gas was changed to the values shown in Table 6 (Battery No. 4).
-1 to 3 and battery No. Ratio 4-1 to 2). Also, Experimental Example 3
Similarly, a 1 μm diamond layer was formed on a stainless steel substrate under the formation conditions shown in Table 6 to prepare a sample for conductivity measurement.

The solar cells prepared in Experimental Example 4 (Battery No. 4-1 to 4-3) and Comparative Experimental Example 4 (Battery No. Ratio 4-1 to 4-2) were tested in the same manner as in Experimental Example 1 to determine their characteristics. Conductivity measurement samples prepared in Experimental Example 4 (Battery No. Ratio 4-1 to 4-3) and Comparative Experiment Example 4 (Battery No. Ratio 4-1 to 2) were evaluated in the same manner as in Experimental Example 3. The dark conductivity σd was determined by the method.

FIG. 6 shows the initial characteristics, thermal deterioration characteristics, 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 No.
．． Examples 4-1 to 3) are the solar cells of comparative experiment examples (Battery No. 4-3).
It was found that the composition had excellent properties compared to ratios 4-1 to 4-2), and the effect of the present invention was verified.

(Experimental Example 5 and Comparative Experimental Example 5) When forming the diamond layer, the layer thickness of the diamond layer was determined as shown in Table 7.
Two solar cells were each manufactured under the same conditions as in Experimental Example 1, except that the values were changed to the values shown in (Battery Nos. 5-1 to 5-1).
3 and battery no. Ratios 5-1 and 5-2), the characteristics were evaluated in the same manner as in Experimental Example 1.

FIG. 7 shows the initial characteristics, thermal deterioration characteristics, stress deterioration characteristics of the solar cell, and the layer thickness of the diamond layer. Figure 7
As can be seen, the solar cells of the present invention (Battery No. 1,
It was found that Examples 5-1 to 5-3) had superior characteristics to the solar cells of comparative experimental examples (cell No. ratios 5-1 to 5-2), and the effect of the present invention was verified.

[0124] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

[0125]

[Example] (Example 1) Two solar cells were created under the same creation conditions as Experimental Example 1,
Using these, a solar cell module was manufactured, and a charger having a circuit configuration as shown in FIG. 8 was manufactured. In Figure 8,
Electric power generated by the solar cell module 801 passes through a backflow prevention diode 803 and is then connected to a secondary battery (manufactured by Toshiba Corporation).
TN-1U) 804 is charged. 802 is an overcharge prevention diode.

(Comparative Example 1) Two solar cells were fabricated under the same fabrication conditions as Comparative Experimental Example 1, and a charger similar to that in Example 1 was fabricated using these.

[0127] The chargers manufactured in Example 1 and Comparative Example 1 were installed outdoors during the daytime on a sunny day, and the solar cell module 801
The secondary battery 804 was charged with the power generated in the above, and then each secondary battery 80 charged with the charger of Example 1 and Comparative Example 1 was charged.
4 into a flashlight (K-67 manufactured by Toshiba Corporation), turn on the light, and when the power of the secondary battery 804 is used up, use the charger of Example 1 and Comparative Example 1 again to
When the operation of charging the next battery 804 was repeated, the charger of Example 1 was approximately 1.3 times larger than the charger of Comparative Example 1.
The flashlight could be turned on for twice as long, demonstrating the effectiveness of the solar cell according to the present invention.

(Example 2) Two solar cells were fabricated in the same manner as in Experimental Example 1, except that the diamond layer, n-type layer, i-type layer, and p-type layer were fabricated under the conditions shown in Tables 8 and 9. were used to make a charger similar to that in Example 1, and used in the same manner as in Example 1.
The flashlight could be turned on for approximately the same time as in Example 1, demonstrating the effectiveness of the solar cell according to the present invention.

Further, on a stainless steel substrate, under the conditions shown in Table 6, a diamond layer was formed with a thickness of 1 μm, and an n-type layer was formed with a thickness of 0.0 μm.
A sample for crystallinity analysis was prepared by depositing a film with a thickness of 0.1 μm, and the crystallinity of the n-type layer was evaluated in the same manner as in Experimental Example 1. It was found to be ring-shaped and amorphous (including microcrystals).
It turned out to be.

[0130] Furthermore, Tables 8 and 9 were placed on the stainless steel substrate.
A sample for crystallinity analysis was prepared by forming an i-type layer of 0.1 μm and a p-type layer of 0.005 μm under the conditions shown in Figure 1. Similar to Experimental Example 1, the crystallinity of the p-type layer was measured. Upon evaluation, it was found to be ring-shaped and amorphous (including microcrystals).

(Example 3) The diamond layer, n-type layer, i-type layer, and p-type layer were as shown in Table 10.
Two solar cells were manufactured in the same manner as in Experimental Example 1, except that the manufacturing conditions shown in Table 11 were used, and these were used in Example 1.
When a similar charger was made and used in the same manner as in Example 1, the flashlight could be turned on for approximately the same amount of time as in Example 1, demonstrating the effectiveness of the solar cell according to the present invention.

[0132] Also, on the stainless steel substrate, No. 10, Table 1
A sample for crystallinity analysis was prepared by forming an i-type layer of 0.1 μm and an n-type layer of 0.005 μm under the preparation conditions shown in Example 1. When evaluated, it was found to be ring-shaped and amorphous (including microcrystals).

[0133]

【table】

[0134]

【table】

[0135]

【table】

[0136]

【table】

[0137]

【table】

[0138]

【table】

[0139]

【table】

[0140]

【table】

[0141]

【table】

[0142]

【table】

[0143]

【table】

[0144]

[Effects of the Invention] In the solar cell having the diamond layer of the present invention, the conversion efficiency was improved and the deterioration of characteristics over time was reduced. As a result, the characteristics of the solar cell were significantly improved.

[0145] Furthermore, the solar cell having the diamond layer of the present invention has a significantly improved manufacturing yield as compared to the conventional solar cell.

[Brief explanation of the drawing]

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

FIG. 2 is a schematic configuration diagram for explaining the layer configuration of a conventional solar cell.

FIG. 3 is a schematic explanatory diagram of a manufacturing device using a glow discharge method using μW, which is an example of the device for manufacturing the 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 the relationship between the dark conductivity and initial characteristics, thermal deterioration characteristics, and stress deterioration characteristics of the diamond layer of the present invention.

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

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

FIG. 8 is an electrical 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 10 using glow discharge decomposition method
01 Deposition chamber 1002 Dielectric window 1003 Gas introduction tube 1004 Substrate 1005 Heater 1006 Vacuum gauge 1007 Conductance valve 1008 Auxiliary valve 1009 Leak valve 1010 Waveguide 1011 DC power supply, 1020 Source gas supply device 1021 to 1025 Mass flow controller 10
31-1035 Gas inflow valve 1041-1045
Gas outflow valves 1051 to 1055 Raw material gas cylinder valves 1061 to 1065 Pressure regulators 1071 to 1075 Raw material gas cylinder 801 Solar cell module 802 Overcharge prevention diode 803 Backflow prevention diode 804 Secondary battery

Claims (1)

[Claims] 1. A solar cell configured by laminating semiconductor layers including a p-layer made of non-single crystal Si, an i-layer as an active layer, and an n-layer on a conductive substrate, the conductive substrate;
A solar cell characterized in that a diamond layer having an uneven surface and containing a valence electron control agent is interposed between the semiconductor layer and the semiconductor layer.