JPH065896A - Solar cell - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a solar cell that exhibits improved output characteristics, particularly open-circuit voltage and fill factor, and that provides more improved output characteristics. A first non-single crystalline layer containing at least silicon atoms and a second non-single crystalline layer containing at least silicon atoms and having a conductivity type different from that of the first non-single crystalline layer are stacked. In the solar cell thus formed, Si _x O _1-x (0.325) is formed between the first non-single crystalline layer and the second non-single crystalline layer.
<X <0.34), which is substantially stoichiometric and is provided with a layer having a hydrogen content of 500 ppm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-single crystalline silicon solar cell having a pi and ni junction, and in particular, by providing a specific diffusion prevention layer at the junction interface, thermal diffusion of impurity atoms is prevented, The present invention relates to a solar cell that maintains a steep junction and, as a result, dramatically improves photoelectric conversion efficiency and reliability.

[0002]

2. Description of the Related Art In recent years, the demand for electric power has rapidly increased all over the world, and the problem of environmental pollution has become serious as the electric power production has been activated to meet such demand. By the way,
In nuclear power generation, which is expected as an alternative power generation method to thermal power generation and has already entered the practical period, serious radioactive contamination damages the human body and damages the natural environment, as represented by the Chernobyl nuclear power plant accident. The situation of invasion has caused the future spread of nuclear power generation to be threatened, and even some countries have actually set laws that prohibit the construction of new nuclear power plants. In addition, even if thermal power generation is used, the amount of fossil fuels represented by coal and oil will continue to increase in order to meet the increasing demand for electric power, and the amount of carbon dioxide emitted will increase accordingly. By increasing the concentration of greenhouse gases such as carbon dioxide and inviting the global warming phenomenon, the annual average temperature of the earth is steadily increasing, and the IEA
(International Energy Age
ncy) will reduce carbon dioxide emissions by 2005 to 2
It is recommended to reduce by 0%.

Against this background, population growth in developing countries and the accompanying increase in power demand are inevitable, and per capita power consumption by promoting further electronics in the future in advanced countries. Coupled with the increase in power supply, the problem of electricity supply has become a situation that must be considered globally. Under such circumstances, the solar cell power generation method that uses sunlight does not cause the problems such as the radioactive contamination and global warming described above, and the sunlight is pouring everywhere on the earth. Since there is little uneven distribution of energy sources, and relatively high power generation efficiency can be obtained without the need for complicated large-scale equipment, it is possible to respond to future increases in power demand without causing environmental damage. It has attracted attention as a clean power generation system, and various research and development has been conducted toward its practical application.

By the way, regarding a power generation method using a solar cell, in order to establish it as a method for supplying power demand, the solar cell used must have a sufficiently high photoelectric conversion efficiency and excellent characteristic stability. It is basically required to be available and capable of mass production. By the way, in order to cover the electricity required for a general household,
Where a solar cell with an output of about kW is required, and the photoelectric conversion efficiency of the solar cell is, for example, about 10%, the area of the solar cell for obtaining the required output is 3
It will be about 0 m ² . And, for example, in order to supply the necessary power for 100,000 households, 3,000,000 m ²
A solar cell with such an area is required.

For this reason, a readily available gaseous raw material gas such as silane is used, and this is subjected to glow discharge decomposition to produce non-single crystalline silicon or the like on a relatively inexpensive substrate such as glass or a metal sheet. The solar cell that can be made by depositing the semiconductor thin film of 1 is highly mass-producible, and there is a possibility that it can be produced at a lower cost and with less energy consumption than the solar cell that is made by using single crystal silicon or the like. Is being watched as. A study of applying this non-single crystalline silicon to a photovoltaic element such as a solar cell is described in W. E. S
Pear and P.P. G. Successful Doping by LeComber (Solid State Communica
section, Vol. 17, pp1193-1196, 1
975). E. Much research has been done, starting with the invention of the solar cell by Carlson (US Pat. No. 4,064,521).

The semiconductor layer, which is an important constituent element of the solar cell, has a semiconductor junction such as a so-called pn junction or pin junction. These semiconductor junctions are formed by sequentially stacking semiconductor layers of different conductivity types, implanting dopants of different conductivity types into a semiconductor layer of one conductivity type by an ion implantation method, or diffusing by thermal diffusion. To be achieved. Regarding this point, a solar cell using a thin film semiconductor such as amorphous silicon, which has been receiving attention, has been described. In its production, phosphine (PH ₃ , n-type semiconductor), diborane (B ₂ H ₆ , p-type semiconductor) A raw material gas containing an element such as a dopant is mixed with silane or the like which is a main raw material gas and decomposed using glow discharge or the like to obtain a semiconductor film having a desired conductivity type. It is known that the semiconductor junction can be easily achieved by sequentially stacking the semiconductor films in the order of pin or nip.

As a result of such research, a solar cell using non-single crystalline silicon has already been used for a clock, a small computer,
It is beginning to be used in small-scale power generation applications such as streetlights, but when generating power on a large scale, for example, for use for power, it has lower conversion efficiency and deterioration than single crystal solar cells and compound solar cells. However, the barriers that must be overcome are still left, and they are mentioned as the disadvantages of non-single crystalline silicon solar cells. Many attempts have been made to overcome this.

For example, a p-type non-single crystalline silicon carbide having a wide forbidden band is used as a window layer on the light incident side (YU).
chida, US-Japan Joint Semi
nar, Technological Applica
tions of Tetrahedral Amor
Phou Solids, Palo Alto, Ca
lifornia (1982)) or p in the window layer
Type microcrystalline silicon carbide (Y. Uchid
a et al, Technical Digest
of the International PVSE
C-3, Tokyo, Japan 1987 A-II
a-3) and the like.

Further, when non-single crystalline silicon carbide having a wide forbidden band is used for the window layer, the step of the energy band occurring at the pi interface is eliminated, and the photoelectric conversion efficiency in the short wavelength region due to carrier back diffusion and recombination. Method of providing a so-called graded buffer layer in which the forbidden band width is continuously changed at the interface for the purpose of preventing the decrease in RR.
a et al, Technical Digest
of the International PVSE
C-3, Tokyo, Japan 1987A-III
a-4) is being attempted.

Further, in order to increase the movement distance of carriers in the i-layer, a small amount of phosphorus atom (P) or boron atom (B) of 10 ppm or less is added to the i-layer (W. Ku.
wano et al, The conference
record of the nineteenth
IEEE photovoltaic special
ists conference-1987, p59
9, M.M. Kondo et al, the conf
erence record of the nine
teenh IEEE photovoltaic
specialtylists conference-19
87, p604) have also been tried.

Furthermore, the diffusion of the p-type and n-type dopants into the i-type semiconductor layer weakens the semiconductor junction at the pi and ni interfaces, resulting in a decrease in the photoelectric conversion efficiency of the photovoltaic element. Attempts have been made to prevent it. As an example of this, Japanese Patent Application Laid-Open No. 55-125681 (Applicant Sanyo Denki) discloses a method of forming a solar cell by providing a partition door between plasma reaction chambers through which a glass substrate placed on a belt conveyor is passed. ing. Further, in US Pat. No. 4,226,897, a gas gate (a gas that does not contribute to film formation is strongly flowed through a space for forming each semiconductor layer in an apparatus for continuously forming solar cells to form a film). It is disclosed that a gas is separated by using a mechanism that substantially acts as a partition wall to prevent the mixture of the dopant into other film formation spaces. As a result of many other studies including these attempts, the disadvantages of non-single crystalline silicon solar cells such as photoelectric conversion efficiency and deterioration have been gradually improved, but the following problems still remain. ing.

That is, the formation space of the p-type semiconductor layer or the n-type semiconductor layer is substantially separated from the formation space of the i-type semiconductor layer by using the method described above, thereby preventing the mixture of the dopant in the gas state. Even if it is possible, for example, when the i layer is formed on the n layer or after the formation, the dopant boron (B) in the n layer is thermally diffused into the i layer. Since the ni semiconductor junction is weakened, the open circuit voltage and fill factor of the solar cell deteriorate,
As a result, there remains a problem in initial characteristics that the photoelectric conversion efficiency becomes low. Further, even if the photoelectric conversion efficiency in the initial stage of manufacture is high to some extent, the thermal diffusion of the p-layer or n-layer dopant to the i-layer does not occur under actual conditions of use under various weather conditions and installation conditions. There is a reliability problem that gradually progresses and this accelerates deterioration of the solar cell.

[0013]

The object of the present invention has been made in view of the above points, and effectively prevents the dopant of the p layer or the n layer from thermally diffusing into the i layer during film formation. By providing the obtained diffusion prevention layer at the pi interface or the ni interface,
It is an object of the present invention to provide a solar cell having improved output characteristics, particularly open-circuit voltage and fill factor, resulting in improved output characteristics.

Another object of the present invention is to reduce the deterioration of the solar cell by providing an effective diffusion prevention layer at the pi interface or the ni interface to prevent the diffusion of the dopant in the actual use state, and as a result, the reliability is improved. To provide an improved solar cell.

[0015]

The present invention has been completed as a result of intensive research conducted by the present inventors in order to solve the problems in the prior art and achieve the above object.

In the solar cell of the present invention, the first non-single crystalline layer containing at least silicon atoms and the second non-single crystalline layer containing at least silicon atoms and having different conductivity types. The non-single crystalline layers are laminated, and Si _x O _1-x (0..x) is formed between the first non-single crystalline layer and the second non-single crystalline layer.
325 <x <0.34), which is substantially stoichiometric and has a hydrogen content of 500 ppm or less.

The specific contents of the solar cell of the present invention having the above structure will be described below. FIG. 1 is a schematic diagram showing the configuration of a typical example of the solar cell of the present invention. The solar cell 101 of the present invention shown in FIG. 1 includes a conductive substrate 102 and an n-type semiconductor layer 1.
03, the diffusion prevention layer 104, the i-type semiconductor layer 105, the p-type semiconductor layer 106, the transparent electrode 107, the collector electrode 108, and the extraction electrode 109, and it is premised that light enters through the transparent electrode 107. . The solar cell of the present invention is different from the conventional solar cell in the diffusion prevention layer 1 described above.
Having 04 is a big difference.

FIG. 7 is a schematic diagram showing the structure of another typical example of the solar cell of the present invention. In the solar cell 701 of this example, a transparent electrode 703, a p-type semiconductor layer 704, a diffusion prevention layer 705, an i-type semiconductor layer 706, n are formed on a transparent substrate 702.
The type semiconductor layer 707 and the back electrode 708 are formed in this order, and it is premised that light is incident through the transparent substrate 702.

FIG. 9 is a schematic view showing the structure of another typical example of the solar cell of the present invention. The solar cell 901 of this example is
This is a solar cell called a tandem type solar cell that is configured by stacking two pin junction solar cells using two types of semiconductor layers having different band gaps or layer thicknesses as i layers.
The solar cell 901 includes an n-type semiconductor layer (1) 903, a diffusion prevention layer (1) 904, an i-type semiconductor layer (1) 905, a diffusion prevention layer (2) 906, and a p-type semiconductor layer on a conductive substrate 902. (1) 907, diffusion prevention layer (3) 908, n-type semiconductor layer (2) 909, diffusion prevention layer (4) 910, i-type semiconductor layer (2) 911, diffusion prevention layer (5) 912, p-type semiconductor Layer (2) 913, transparent electrode 914 and current collecting electrode 915
Are formed in this order, and it is premised that light enters through the transparent electrode 914.

In any of the solar cell examples, the stacking order of the n-type semiconductor layer and the p-type semiconductor layer can be changed according to the purpose, but the p-type semiconductor layer is provided closer to the light incident surface. It is more desirable to use the generated carrier more effectively.

Each constituent element of these solar cells will be described below.

[0022]

[Substrate] Conductive substrate (10) in the solar cell of the present invention.
2, 902), a plate-like body and a film body of molybdenum, tungsten, titanium, cobalt, chromium, iron, copper, tantalum, niobium, zirconium, aluminum metal or their alloys can be mentioned. Among them, stainless steel, nickel-chromium alloy, nickel, tantalum, niobium, zirconium, titanium metal and alloys of these metals are particularly preferable from the viewpoint of corrosion resistance. Further, these metals or alloys, polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, a film or sheet of synthetic resin such as polyamide,
Those formed on glass, ceramic or the like can also be used.

The above-mentioned substrate may be used alone, but a layer having reflectivity and conductivity to visible light (hereinafter referred to as "reflective conductive layer") is provided on the substrate. desirable. As a material of the reflective conductive layer applicable to the present invention, silver, silicon, aluminum or an alloy thereof or an alloy with iron, copper, nickel, chromium or molybdenum is applicable. Among them, silver, aluminum and aluminum-silicon alloy are preferable. In addition, by making the thickness of the reflective conductive layer large, it is possible to use itself as a substrate.

As a method suitably used for forming the reflective conductive layer on the surface of the substrate, a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method and the like can be mentioned.

The transparent substrate (70 in the solar cell of the present invention
Examples of the constituent material of 2) include films or sheets of synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, and glass.

[0026]

[Electrode] In the solar cell of the present invention, an appropriate electrode is selected and used depending on the configuration of the device. Examples of those electrodes include a lower electrode, an upper electrode (transparent electrode), and a collector electrode (however, the upper electrode here means one provided on the light incident side, and the lower electrode is The one provided to face the upper electrode with the semiconductor layer sandwiched therebetween.

Since the lower electrode used in the present invention has a different surface on which light is incident depending on whether or not the above-mentioned substrate is translucent, the location where it is installed is different.

Specifically, in the case of the layer structure as shown in FIGS. 1 and 9, it is provided between the substrate (102, 902) and the n-type semiconductor layer (or p-type semiconductor layer) (103, 903). To be When the base body (102, 902) is conductive, the base body can also serve as the lower electrode. In the case of the layer structure as shown in FIG. 7, a transparent substrate (7
02) is used, and light is incident from the side of the base body, the lower electrode 708 is provided in order to extract a current and effectively reflect the light that reaches the electrode without being absorbed by the semiconductor layer. The semiconductor layer is provided so as to face the base 702 and sandwich the semiconductor layer.

The constituent material of the lower electrode preferably used in the solar cell of the present invention is Ag, Au, Pt, Ni, C.
Examples thereof include metals such as r, Cu, Al, Ti, Zn, Mo and W or alloys thereof. The lower electrode can be formed using these metals by a film forming means such as vacuum evaporation, electron beam evaporation, or sputtering. The metal thin film formed at that time must be considered so as not to become a resistance component to the output of the solar cell, and the sheet resistance value is preferably 5 or less.
It is desirable to be 0Ω or less, and more preferably 10Ω or less.

Lower electrodes (102, 708, 902) and n
Type semiconductor layer (or p type semiconductor layer) (103, 70
7, 903), although not shown in the figure, Z
A buffer layer may be provided to prevent short circuits such as nO and prevent diffusion of electrode metal. The effect of the buffer layer is not only to prevent the metal element constituting the lower electrode (102, 708, 902) from diffusing into the n-type semiconductor layer (or p-type semiconductor layer) but also to reduce the resistance value to some extent. The lower electrodes (102, 708,
902) and the upper (transparent) electrodes (107, 703, 91)
4) and the like, it is possible to prevent short circuit caused by defects such as pinholes, and to generate multiple interference by the thin film to confine incident light in the solar cell.

Materials preferably used as the constituent material of the buffer layer are magnesium fluoride-based materials, indium, tin, cadmium, zinc, antimony, silicon, chromium, silver, copper, aluminum oxides, nitrides, and Examples include materials selected from carbides and mixtures thereof. In particular, magnesium fluoride and zinc oxide are desirable because they are easy to form and have appropriate resistance and light transmittance as a buffer layer.

The transparent electrode (10 used in the present invention
7, 703, 914), the light transmittance is preferably 70% or more, and more preferably 80% or more in order to efficiently absorb light from the sun, white fluorescent lamps, etc. in the semiconductor layer. More desirable. Further, electrically, it is desirable that the sheet resistance value is 100Ω or less so as not to be a resistance component to the output of the solar cell. As materials having such characteristics, SnO ₂ , In ₂ O ₃ , ZnO, Cd
Examples thereof include metal oxides such as O, 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 extremely thinly and semitransparently. In the solar cell having the configuration shown in FIGS. 1 and 9, the transparent electrode is a p-type semiconductor layer (or an n-type semiconductor layer) (106,
903), and the solar cell having the structure shown in FIG. 7 is laminated on the base body, so it is necessary to select those having good adhesion to each other.
A resistance heating vapor deposition method, an electron beam heating vapor deposition method, a sputtering method, a spraying method, or the like can be used as a method for producing these, and is appropriately selected as desired.

The collecting electrode (10 used in the present invention
8, 905) are transparent electrodes (107, 914) for the purpose of reducing the sheet resistance value of the transparent electrodes (107, 914).
Provided on top. In the solar cell configured as shown in FIGS. 1 and 9, the transparent electrode (107,
914) to form the transparent electrodes (107, 91).
Since the substrate temperature at the time of forming 4) cannot be raised so much and the sheet resistance value of the transparent electrode must be relatively high, the collector electrode (108, 915) should be formed. Is particularly preferable. On the other hand, in the solar cell having the structure as shown in FIG. 7, since the transparent electrode 703 is formed directly on the substrate, the substrate temperature at the time of formation can be increased, and the sheet resistance value of the transparent electrode 703 can be relatively high. Since it can be lowered, the number of collecting electrodes is unnecessary or small. In FIG. 7, as an example in which the collector electrode is unnecessary, a solar cell having a configuration in which the extraction electrode 709 is directly provided on the transparent electrode 703 is shown.

As the constituent material of the collecting electrode preferably used for the solar cell of the present invention, Ag, Cr, Ni, Al, A
Examples include simple metals such as g, Au, Ti, Pt, Cu, Mo, W, alloys of these, and carbon. In addition, by combining these metals or carbon, the advantages of each metal or carbon (low resistance, less diffusion into the semiconductor layer, robust, easy electrode formation by printing etc.) are combined. Can be used. The shape and area of the semiconductor layer are appropriately designed so as to secure a sufficient amount of light incident on the semiconductor layer.
Its shape is uniformly spread over the light receiving surface of the solar cell, and its area is preferably 15% or less with respect to the light receiving area.
More preferably, it is 10% or less. The sheet resistance value is preferably 50Ω or less, more preferably 10Ω or less.

[0035]

[Semiconductor Layer] As a semiconductor material for the i-type semiconductor layer that is preferably used in the solar cell of the present invention, a-S
i: H, a-Si: F, a-Si: H: F, a-Si
C: H, a-SiC: F, a-SiC: H: F, a-S
iGe: H, a-SiGe: F, a-SiGe: H:
F, polycrystalline Si: H, polycrystalline Si: F, polycrystalline S
Examples include so-called group IV and group IV alloy-based semiconductor materials such as i: H: F. The amount of hydrogen atoms contained in the i-type semiconductor layer is preferably 20 atom% or less, more preferably 10 atom% or less.

The semiconductor material forming the p-type or n-type semiconductor layer that is preferably used in the solar cell of the present invention is
It can be obtained by doping the above-mentioned semiconductor material forming the i-type semiconductor layer with a valence electron control agent, but it is better that the semiconductor material forming the p-type or n-type semiconductor layer contains a crystal layer. Is preferable because the utilization rate and carrier density can be increased. In that case, the crystal grain size is preferably 30 Å or more. However, rather than the crystal layer being in direct contact with the interface between the diffusion preventing layer and the p-type or n-type semiconductor layer, the presence of at least an amorphous semiconductor layer at the interface improves the photoelectric conversion efficiency of the solar cell. Is preferred. It is considered that this is because the structural disorder and stress that occur at the interface between the diffusion prevention layer and the p-type or n-type semiconductor layer are alleviated, and the matching at the interface is enhanced.

In addition, the reliability of the solar cell is improved by interposing at least an amorphous semiconductor layer at the interface between the diffusion preventing layer and the p-type or n-type semiconductor layer rather than directly contacting the crystal layer. It is also preferable in that it is allowed. This is because the diffusion prevention layer and the p-type or n-type
By interposing the amorphous semiconductor layer at the interface of the type semiconductor layer, the thermal expansion coefficient is different between the diffusion prevention layer and the p-type or n-type semiconductor layer. To reduce the deterioration of the bonding characteristics and enhance the adhesiveness between the diffusion prevention layer and the p-type or n-type semiconductor layer to prevent peeling.
It is also presumed that this is the result of increased strength against bending and impact. The concentration of hydrogen contained in the p-type or n-type semiconductor layer is preferably 5 atom% or less, more preferably 1 atom% or less.

The raw material gas for forming the semiconductor layer used when forming these semiconductor layers is a simple substance of the above-mentioned constituent elements of the various semiconductor layers, hydrides, halides, organometallic compounds, etc. Those that can be introduced in a gas state are preferably used.

Of course, these raw material gases may be used alone or in combination of two or more. Also,
These source gases are He, Ne, Ar, Kr, Xe. R
It may be introduced by mixing with a rare gas such as n and a diluting gas such as H ₂ , HF and HCl.

The diffusion preventing layers (104, 705, 904, 906, 90) used in the solar cell of the present invention.
8, 910, 912) is made of Si _x
O _1-x (0.325 <x <0.34), which is substantially stoichiometric and has a hydrogen content of 500
It is below ppm.

As means for forming each of the semiconductor layers and the diffusion preventing layer used in the solar cell of the present invention, there are a microwave plasma CVD method, an RF plasma CVD method, a sputtering method and a reactive sputtering method, an ion plating method, Optical CVD method, thermal CVD method, MOCVD
Method, MBE method, HR-CVD method, etc., a film forming means capable of realizing so-called semiconductor deposited film formation can be mentioned.
These are appropriately selected and used.

A method of forming a non-single crystalline silicon solar cell having a diffusion barrier layer according to the present invention will be described in detail with reference to the drawings. In the description, a microwave (hereinafter abbreviated as “μW”) glow discharge decomposition method is adopted as an example, but the present invention is not limited thereto.

N-type semiconductor layer 103, diffusion prevention layer 104,
The i-type semiconductor layer 105 and the p-type semiconductor layer 106 are shown in FIG.
An example of the formation method using the apparatus according to the μW glow discharge decomposition method including the source gas supply system 1020 and the deposition system 1000 shown in FIG.

Gas cylinders 1071 to 1076 in the figure are filled with a raw material gas for forming each layer of the present invention, and 1071 is a SiH ₄ gas cylinder, 1072.
H ₂ gas cylinder, 1073 (hereinafter abbreviated as "PH ₃ / H _2") PH ₃ gas diluted to 10% with H ₂ gas bomb 1074 BF ₃ gas diluted to 10% with H ₂ gas (Hereinafter abbreviated as "BF ₃ / H ₂ ") cylinders 1075 are O ₂ gas cylinders and 1076 are Ar gas cylinders.

SiH ₄ gas from the gas cylinder 1071, H ₂ gas from the gas cylinder 1072, PH ₃ / H ₂ gas from the gas cylinder 1073, BF ₃ / H ₂ from the gas cylinder 1074.
Gas, O ₂ gas from the gas cylinder 1075, Ar gas from the gas cylinder 1076, valves 1051 to 105
6 is opened and introduced into each gas pipe up to the inflow valves 1031 to 1036, and the gas pressure in each pipe is adjusted to about 2 kg by the pressure regulators 1061 to 1066.
Adjust to / cm ² .

The substrate 1004 in the figure is arranged on a supporting means 1005 having a heater. Make sure that the inlet valves 1031 to 1036 and the leak valve 1009 of the deposition chamber 1001 are closed, and that the outlet valves 1041 to 1046 and the auxiliary valve 100 are closed.
8 is 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 reading of the vacuum gauge 1006 is preferably 1 x 10 ^-4 T
The auxiliary valve 1008 and the outflow valves 1041 to 1046 are closed when the pressure reaches orrr, more preferably 1 × 10 ⁻⁵ Torr. Next, the inflow valves 1031 to 1010
36 is gradually opened, and each gas is introduced into the mass flow controllers 1021 to 1026.

After preparation for film formation is completed as described above,
On the substrate 1004, the n-type semiconductor layer 103 and the diffusion prevention layer 1
04, film formation of the i-type semiconductor layer 105 and the p-type semiconductor layer 106 is started.

To form the n-type semiconductor layer 103, the substrate 1004 is heated and held at a temperature of preferably 200.degree. C. or higher, more preferably 250.degree. C. or higher by a heater 1005 ', and the outflow valves 1041, 1042, 1043 and auxiliary valves are used. The valve 1008 is gradually opened to prevent dust from scattering in the deposition chamber, and SiH ₄ gas, H ₂ gas and PH _{3 are} added.
/ H ₂ gas is introduced into the deposition chamber 100 through the gas introduction pipe 1003.
1. At this time, the SiH ₄ gas flow rate is 1 to 500 sccm, and the H ₂ gas flow rate is 10 sccm to 1
000 sccm, PH ₃ / H ₂ gas flow rate is 0.5% to 30% with respect to the flow rate of SiH ₄ gas.
Adjust with. The pressure in the deposition chamber 1001 is preferably 5
The opening of the conductance valve 1007 is adjusted while observing the vacuum gauge 1006 so that the desired pressure is 0 mTorr or less, more preferably 20 mTorr or less.

Next, a DC bias of 10V to 120V by the DC power supply 1011 and a high frequency power of 0W to 200W by the high frequency power supply 1012 (frequency 13.56).
The sum of (MHz) is applied to the bias applying electrode 1013.
After that, the power of a μW power source (not shown) is preferably set to 100.
W to 1200 W, more preferably 200 W to 800
Set to W, μW electric power is introduced into the deposition chamber 1001 through a waveguide, a waveguide section 1010, and a dielectric window 1002 (not shown) to generate μW glow discharge, and n on the substrate 1004.
A type semiconductor layer is formed. The thickness of the n-type semiconductor layer is preferably 20 Å (hereinafter abbreviated as “Å”)
To 300 Å, more preferably 30 Å to 200 Å at a desired value, the μW glow discharge is stopped, the DC power supply 1011 and the high frequency power supply 1012 are turned off, and the outflow valves 1041 and 1043 and the auxiliary valve 1 are connected.
008 is closed to stop the gas flow into the deposition chamber 1001.

Next, in order to form the diffusion prevention layer 104, the substrate 1004 is heated and held at a temperature of preferably 150 ° C. or higher, more preferably 200 ° C. or higher by a heater 1005 ′, and the outflow valves 1041 and 1045 and the auxiliary valves are heated. The valve 1008 is gradually opened to allow SiH ₄ gas and O ₂ gas to flow into the deposition chamber 1001 through the gas introduction pipe 1003. SiH ₄ gas flow rate at this time is 1 to 50 s
ccm, O ₂ gas flow rate is 1 to 100 sccm so that each mass flow controller 1021, 102
Adjust with 5. The pressure inside the deposition chamber 1001 is preferably 50 mTorr or less, more preferably 20 mTorr or less, while adjusting the opening of the conductance valve 1007 while observing the vacuum gauge 1006. Next, the sum of the DC bias of 10 V to 120 V from the DC power supply 1011 and the high frequency power of 10 W to 200 W (frequency 13.56 MHz) from the high frequency power supply 1012 is applied to the bias applying electrode 1013. After that, the power of a μW power source (not shown) is preferably 100 W to 1200 W.
W, more preferably set to 200 W to 800 W, and a waveguide, a waveguide section 1010, and a dielectric window 1002 (not shown).
A μW electric power is introduced into the deposition chamber 1001 via the electrode to generate a μW glow discharge. At that time, a rotatable mesh grid 1014 is installed near the substrate 1004 to remove low energy ions and selectively inject high energy ions onto the substrate. The thickness of the diffusion prevention layer 104 is preferably 5Å
When the desired layer thickness of 20 to 20 Å is reached, the μW glow discharge is stopped, and the DC power supply 1011 and the high frequency power supply 1012 are
Is stopped, and the outflow valves 1041 and 1045 and the auxiliary valve 1008 are closed to stop the gas inflow into the deposition chamber 1001.

Next, in order to form the i-type semiconductor layer 105, the substrate 1004 is heated and held at 150 ° C. or higher, more preferably 200 ° C. or higher by the heater 1005 ′, and the outflow valve 1041 and the auxiliary valve are used. 1
008 is gradually opened to introduce SiH ₄ gas into the gas introducing pipe 10
It is made to flow into the deposition chamber 1001 through 03. At this time, the SiH ₄ gas flow rate is preferably 1 sccm to 500.
Mass flow controller 102 to be sccm
Adjust with 1. The pressure inside the deposition chamber 1001 is preferably 50 mTorr or less, more preferably 20 mTorr or less, while adjusting the opening of the conductance valve 1007 while observing the vacuum gauge 1006. The rotatable mesh grid 1014 is removed from the vicinity of the substrate 1004 by rotating. Next, a DC bias of 10V to 120V from the DC power supply 1011 and 10W to 20W from the high frequency power supply 1012.
The sum of 0 W high frequency power (frequency 13.56 MHz) is applied to the bias applying electrode 1013. After that, the power of the μW power source (not shown) is preferably 100 W to 1200 W.
W, more preferably set to 200 W to 800 W, and a waveguide, a waveguide section 1010, and a dielectric window 1002 (not shown).
A μW electric power is introduced into the deposition chamber 1001 via the substrate to generate a μW glow discharge, and an i-type semiconductor layer is formed on the substrate 1004.

The layer thickness of the i-type semiconductor layer is preferably 100.
0Å to 8000Å, more preferably 2000Å to 6
When the desired value of 000Å is reached, the μW glow discharge is stopped, the outputs of the DC power supply 1011 and the high frequency power supply 1012 are turned off, and the outflow valves 1041 and 1043 and the auxiliary valve 1008 are closed to allow the gas to flow into the deposition chamber 1001. Stop.

Next, in order to form the p-type semiconductor layer 106, the substrate 1004 is heated and held at a temperature of preferably 150 ° C. or higher, more preferably 200 ° C. or higher by the heater 1005 ′, and the outflow valves 1041, 1042 are used. 104
4 is opened gradually, SiH ₄ gas, H ₂ gas, BF ₃ / H ₂
Gas is introduced into the deposition chamber 1001 through the gas introduction pipe 1003. SiH ₄ gas flow rate at this time is 1 sccm
To 500 sccm, the H ₂ gas flow rate is 10 sccm to 1000 sccm, and the BF ₃ / H ₂ gas flow rate is 0.5% to 30% with respect to the SiH ₄ gas flow rate.
Adjust with. The pressure in the deposition chamber 1001 is preferably 5
The opening of the conductance valve 1007 is adjusted while observing the vacuum gauge 1006 so that the desired pressure is 0 mTorr or less, more preferably 20 mTorr or less. next,
DC bias of 10V to 120V by DC power supply 1011 and 0W to 20 by high frequency power supply 1012
The sum of 0 W high frequency power (frequency 13.56 MHz) is applied to the bias applying electrode 1013. After that, the power of the μW power source (not shown) is preferably 100 W to 1200 W.
W, more preferably set to 200 W to 800 W, and a waveguide, a waveguide section 1010, and a dielectric window 1002 (not shown).
A μW electric power is introduced into the deposition chamber 1001 via the substrate to generate a μW glow discharge, and an i-type semiconductor layer is formed on the substrate 1004. When the thickness of the i-type semiconductor layer reaches a desired value of preferably 20 Å to 300 Å, more preferably 30 Å to 200 Å, the μW glow discharge is stopped, the output of the DC power supply 1011 and the high frequency power supply 1012 is cut off, and the outflow occurs. The valves 1041, 1042 and 1043 and the auxiliary valve 1008 are closed to stop the gas flow into the deposition chamber 1001.

Needless to say, the outflow valves 1041 to 1046 other than the required gas are completely closed when forming the respective layers, and the respective gases are stored in the deposition chamber 1001 and the outflow valve 1041. Through 1046
In order to avoid remaining in the pipe from the chamber to the deposition chamber 1001, the outflow valves 1041 to 1046 are closed, the auxiliary valve 1008 is opened, the conductance valve 1007 is fully opened, and the system is temporarily evacuated to a high vacuum. Shall be carried out as necessary.

Finally, the inflow valves 1031 to 103
6. Confirm that the leak valve 1009 of the deposition chamber 1001 is closed, and the outflow valves 1041 to 1041
046, confirm that the auxiliary valve 1008 is open, and then conductance (butterfly type) valve 1007
Is fully opened, and the deposition chamber 100 is driven by a vacuum pump (not shown).
1 and the gas pipe were evacuated, and when the reading of the vacuum gauge 1006 became about 1 × 10 ⁻⁴ Torr, the outflow valve 104
1 to 1046 and the auxiliary valve 1008 are closed, the leak valve 1009 is opened to leak the inside of the deposition chamber 1001, and the substrate on which the n-type semiconductor layer, the diffusion prevention layer, the i-type semiconductor layer, and the p-type semiconductor layer are formed on the surface 1004 is taken out from the deposition chamber 1001.

[0056]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 A non-single crystalline silicon solar cell having a diffusion barrier layer according to the present invention was manufactured as follows.

The n-type semiconductor layer 103, diffusion preventing layer 104, i-type semiconductor layer 105 and p-type semiconductor layer 106 made of non-single crystalline silicon were formed by the μW glow discharge decomposition method. The apparatus including the source gas supply system 1020 and the deposition system 1000 shown in FIG. 3 was used to form each silicon-containing layer. In the gas cylinders 1071 to 1076 in the figure,
Raw material gas for forming each layer of the present invention is filled, and 1071 is SiH ₄ gas (purity 99.99%).
Cylinder 1072 is H ₂ gas (purity 99.9999%)
Cylinder 1073 is PH ₃ diluted with H ₂ gas to 10%
Gas (purity 99.999%, hereinafter abbreviated as “PH ₃ / H ₂ ”) cylinder 1074 is BF ₃ gas diluted to 10% with H ₂ gas (purity 99.999%, hereinafter “BF ₃ /
Abbreviated as "H ₂ ") cylinder, 1075 is O ₂ gas (purity 9
9.99%) cylinder and 1076 are Ar gas (purity 9
9.999%) cylinder.

SiH ₄ gas from the gas cylinder 1071, H ₂ gas from the gas cylinder 1072, PH ₃ / H ₂ gas from the gas cylinder 1073, BF ₃ / H ₂ from the gas cylinder 1074.
Gas, O ₂ gas from the gas cylinder 1075, Ar gas from the gas cylinder 1076, valves 1051 to 105
6 is opened and introduced into each gas pipe up to the inflow valves 1031 to 1036, and the gas pressure in each pipe is adjusted to about 2 kg by the pressure regulators 1061 to 1066.
/ Cm ² was adjusted. The substrate 1004 in the figure has a size of 100 mm square, a thickness of 1.0 mm, and a layer thickness of about 0.
A substrate was used in which a 3 μm non-directed silver (Ag) layer was pre-deposited with an undirected zinc oxide (ZnO) layer having a layer thickness of about 1.0 μm.

Next, it is confirmed that the inflow valves 1031 to 1036 and the leak valve 1009 of the deposition chamber 1001 are closed, and the outflow valves 1041 to 1041.
046 and the auxiliary valve 1008 are confirmed to be open, and the conductance (butterfly type) valve 10
07 is fully opened and a vacuum pump (not shown) is used to form the deposition chamber 1.
The auxiliary valve 1 was exhausted when 001 and the gas pipe were evacuated and the reading of the vacuum gauge 1006 became about 1 × 10 ⁻⁴ Torr.
008 and outflow valves 1041-1046 were closed. Next, the inflow valves 1031 to 1036 are gradually opened to allow the respective gases to flow through the mass flow controller 1021.
Through 1026.

After the preparation for film formation is completed as described above, the n-type semiconductor layer 103, the diffusion prevention layer 104, the i-type semiconductor layer 105 and the p-type semiconductor layer 10 are formed on the substrate 1002.
6 was formed.

The n-type semiconductor layer 103 was formed as follows. That is, the substrate 1004 is heated by the heater 1005 '.
Heated to 300 ° C by the outflow valves 1041 and 104
3 and the auxiliary valve 1008 are gradually opened, and SiH ₄
Gas, H ₂ gas, and PH ₃ / H ₂ gas for introducing gas 10
It was made to flow into the deposition chamber 1001 through 03. At this time,
SiH ₄ gas flow rate is 10 sccm, H ₂ gas flow rate is 100
Each mass flow controller 1021, so that the flow rate of sccm and PH ₃ / H ₂ gas is 1.0 sccm.
Adjusted at 1022 and 1023. The opening of the conductance valve 1007 was adjusted while observing the vacuum gauge 1006 so that the pressure in the deposition chamber 1001 was 5 mTorr. Next, a +100 V DC bias from the DC power supply 1011 was applied to the bias applying electrode 1013. After that, the power of a μW power source (not shown) is set to 400 W, and μW power is introduced into the deposition chamber 1001 through a waveguide, a waveguide section 1010 and a dielectric window 1002 (not shown) to cause a μW glow discharge. , The formation of the n-type semiconductor layer on the substrate 1004 is started, and the μW glow discharge is stopped when the n-type semiconductor layer 103 having a layer thickness of about 200 Å is formed, and the DC power supply 1011
And the output of the high frequency power supply 1012 is turned off, and the outflow valves 1041, 1042 and 1043 and the auxiliary valve 1
008 was closed to stop the gas flow into the deposition chamber 1001, and the formation of the n-type semiconductor layer 103 was completed.

Next, the diffusion prevention layer 104 was formed as follows. That is, the substrate 1004 is heated by the heater 100.
Heated to 250 ° C by 5 ', and outflow valve 1041,1
045 and the auxiliary valve 1008 are gradually opened to
H ₄ gas and O ₂ gas were caused to flow into the deposition chamber 1001 through the gas introduction pipe 1003. At this time, the mass flow controllers 1021 and 1025 were adjusted so that the SiH ₄ gas flow rate was 5 sccm and the O ₂ gas flow rate was 6 sccm. The opening of the conductance valve 1007 was adjusted while observing the vacuum gauge 1006 so that the pressure in the deposition chamber 1001 was 5 mTorr. Next, DC power supply 1011
+ 45V DC bias and high frequency power supply 10
High frequency power of 50W by 12 (frequency 13.56MH
The sum of z) was applied to the bias applying electrode 1013. After that, the power of a μW power source (not shown) is set to 100 W, and μW power is introduced into the deposition chamber 1001 through a waveguide, a waveguide section 1010 and a dielectric window 1002 (not shown) to cause a μW glow discharge. Let At that time, a rotatable mesh grid 1014 was installed near the substrate 1004 to remove low energy ions and selectively inject high energy ions onto the substrate. When the diffusion prevention layer is formed on the n-type semiconductor layer and the diffusion prevention layer 104 having a layer thickness of 10 Å is formed, μW glow discharge is stopped, the outputs of the DC power supply 1011 and the high frequency power supply 1012 are cut off, and the outflow valve 104
1, 1045 and the auxiliary valve 1008 were closed to stop the gas flow into the deposition chamber 1001 and the formation of the diffusion prevention layer 104 was completed.

Next, the i-type semiconductor layer 105 was formed as follows. That is, the substrate 1004 is heated by the heater 10.
It was heated to 250 ° C. by 05 ′, the outflow valve 1041 and the auxiliary valve 1008 were gradually opened, and SiH ₄ gas was introduced into the deposition chamber 1001 through the gas introduction pipe 1003. At this time, the mass flow controller 1021 adjusted the SiH ₄ gas flow rate to 150 sccm. The conductance valve 1 is checked while observing the vacuum gauge 1006 so that the pressure in the deposition chamber 1001 becomes 5 mTorr.
The opening of 007 was adjusted. Next, at that time, the rotatable mesh grid 1014 was rotated and removed from the vicinity of the substrate 1004. Next, +60 by the DC power supply 1011
1 by the DC bias of V and the high frequency power source 1012
The sum of high-frequency power of 00 W (frequency 13.56 MHz) was applied to the bias applying electrode 1013. Thereafter, the power of a μW power source (not shown) is set to 300 W, and μW power is introduced into the deposition chamber 1001 through a waveguide, a waveguide section 1010 and a dielectric window 1002 (not shown) to cause a μW glow discharge. Then, the formation of the i-type semiconductor layer on the n-type semiconductor layer is started, the μW glow discharge is stopped when the i-type semiconductor layer 105 having a layer thickness of about 4000 Å is formed, the output of the DC power supply 1011 is cut off, and the outflow valve 1041 and Auxiliary valve 100
8 is closed to stop the gas from flowing into the deposition chamber 1001 and i
The formation of the type semiconductor layer 105 is completed.

Next, the p-type semiconductor layer 106 was formed as follows. That is, the substrate 1004 is heated by the heater 10.
It is heated to 200 ° C by 05 ', and the outflow valve 1041,
Gradually open 1042 and 1044 to remove SiH ₄ gas and H ₂
Gas and BF ₃ / H ₂ gas were caused to flow into the deposition chamber 1001 through the gas introduction tube 1003. At this time, the SiH ₄ gas flow rate is 10 sccm, the H ₂ gas flow rate is 100 sccm, and B
The mass flow controllers 1021, 1022 and 1024 were adjusted so that the F ₃ / H ₂ gas flow rate was 1 sccm. The opening of the conductance valve 1007 was adjusted while observing the vacuum gauge 1006 so that the pressure in the deposition chamber 1001 was 5 mTorr. Next, the DC power supply 101
A DC bias of +100 V according to No. 1 was applied to the bias applying electrode 1013. After that, the power of the μW power source (not shown) is set to 400 W, and the waveguide and the waveguide section 1010 (not shown) are set.
And μ in the deposition chamber 1001 through the dielectric window 1002.
W power was introduced to cause μW glow discharge, the formation of the p-type semiconductor layer on the i-type semiconductor layer was started, and the μW glow discharge was stopped when the p-type semiconductor layer 106 having a layer thickness of 100 Å was formed, and the DC power supply was applied. The output of 1011 is turned off, and the outflow valves 1041, 1042, 1044 and the auxiliary valve 1
By closing 008, the gas flow into the deposition chamber 1001 was stopped, and the formation of the p-type semiconductor layer 106 was completed.

Table 1 shows the manufacturing conditions of the above solar cell.

It is needless to say that the outflow valves 1041 to 1046 other than the required gas are completely closed when forming each layer, and the respective gases are discharged in the deposition chamber 1001 and outflow valve 1041. Through 1046
In order to avoid remaining in the pipe from the chamber to the deposition chamber 1001, the outflow valves 1041 to 1046 are closed, the auxiliary valve 1008 is opened, the conductance valve 1007 is fully opened, and the system is temporarily evacuated to a high vacuum. Was done as needed.

Next, the inflow valves 1031 to 1036,
Make sure that the leak valve 1009 of the deposition chamber 1001 is closed and that the outflow valves 1041 to 104
6. Confirming that the auxiliary valve 1008 is opened, the conductance (butterfly type) valve 1007 is fully opened, and the deposition chamber 1001 is opened by a vacuum pump (not shown).
And the gas pipe is evacuated, and when the reading of the vacuum gauge 1006 becomes about 1 × 10 ⁻⁴ Torr, the outflow valve 1041
Through 1046 and the auxiliary valve 1008 are closed, and the leak valve 1009 is opened to leak the inside of the deposition chamber 1001.
A substrate 1004 having an n-type semiconductor layer, a diffusion prevention layer, an i-type semiconductor layer, and a p-type semiconductor layer formed on the surface thereof is placed in a deposition chamber 10
It was taken out from inside 01.

Then, ITO (In ₂ O ₃ + SnO ₂ ) having a layer thickness of 700 Å was formed as a transparent electrode 107 on the p-type semiconductor layer 106 of the non-single crystalline solar cell by a known resistance heating vacuum deposition method. By vacuum vapor deposition, and further, Al having a layer thickness of 2 μm was vapor deposited as a collector electrode 108 by a known resistance heating vacuum vapor deposition method to prepare a non-single crystalline silicon solar cell (Sample No. 1).

Sample No. The composition ratio of the film constituent elements of the diffusion prevention layer of No. 1 was evaluated as follows. That is, the deposition chamber 1001 in FIG. 3 is equipped with an X-ray photoelectron spectroscopy analyzer (ESCA-850 manufactured by Shimadzu Corporation), and the diffusion prevention layer 104 is n-typed by the same method and under the same conditions as the above solar cell manufacturing method. Substrate 1 after being formed on a semiconductor layer
004 was transported to the measurement chamber of the above X-ray photoelectron spectroscopy analyzer in vacuum without exposing it to the atmosphere, and the composition of the elements constituting the diffusion prevention layer was analyzed. As a result, the main atoms constituting the diffusion prevention layer were Si and O, the ratio was 32.6%: 67.4%, and the other elements were below the detection limit. For this reason, the extremely thin diffusion barrier layer formed by the above-described manufacturing method and manufacturing conditions is substantially stoichiometric (stoichiometric) silicon dioxide (SiO ₂ ).
I found out.

Next, a quantitative analysis of hydrogen atoms (H) present in the diffusion barrier layer film was carried out as follows. That is,
The deposition chamber 1001 in FIG. 3 is equipped with a secondary ion mass spectrometer (IMS-4F manufactured by CAMECA), and the diffusion prevention layer 104 is formed on the n-type semiconductor layer by the same method and under the same conditions as the above solar cell manufacturing method. Substrate 1 after formation
When 004 was transported to the measurement chamber of the above-mentioned secondary ion mass spectrometer in a vacuum without being exposed to the atmosphere, the hydrogen atom (H) present in the film of the diffusion prevention layer was quantitatively analyzed.
It was below the detection limit (100 ppm). From this, it was found that the hydrogen atom concentration in the film of the diffusion prevention layer was extremely small and a very dense film was formed.

Further, in the deposition chamber 1001 shown in FIG.
Equipped with M device (HITACHI H8000),
After being formed on the n-type semiconductor layer by the same method and under the same conditions as the above solar cell manufacturing method, the substrate 1004 is transferred to the measurement chamber of the TEM device in a vacuum without being exposed to the atmosphere, and the n-type semiconductor layer is formed. When the crystallinity of the semiconductor layer was evaluated,
It was found that the non-single crystalline silicon forming the n-type semiconductor layer has microcrystallinity.

After forming the n-type semiconductor layer and the diffusion prevention layer thereon under the same method and under the same conditions as the above solar cell manufacturing method, the substrate 1004 is taken out, the cross section is polished, and then the STM device (digital Observation using an instrument Nanoscope AFM) confirmed that crystal grains were not in direct contact with each other at the interface between the n-type semiconductor layer and the diffusion prevention layer, but an amorphous semiconductor layer was interposed. .

Comparative Example 1  Without forming the diffusion prevention layer 104 on the n-type semiconductor layer,
Example 1 except that an i-type semiconductor layer was formed on the conductor layer
Similarly to the above, as shown in FIG.
N-type semiconductor layer 203, i-type semiconductor layer 204, p-type half
The conductor layer 205, the transparent electrode 206 and the collector electrode 207 are
Formed and fabricated a conventional non-single crystalline silicon solar cell
(Comparative sample No. 1).

First, the solar cell obtained in Example 1 (Sample N
o. 1) and the solar cell obtained in Comparative Example 1 (Comparative Sample No. 1), photoelectric conversion efficiency η = {maximum generated power per unit area (mW / cm ² ) / incident light intensity per unit area (MW / cm ² )} was evaluated.

Sample No. 1 of Example 1 Comparative sample No. 1 of Comparative Example 1 and Comparative Example 1. Five solar cells of No. 1 were produced and placed under AM-1.5 (100 mW / cm ² ) light irradiation, and a DC voltage was applied to the extraction electrode 109 (208 in FIG. 2) of FIG. The characteristics were measured and the open circuit voltage, the fill factor and the photoelectric conversion efficiency η were evaluated. Sample No. 1 for the solar cell No. 1
The solar cell No. 1 has an average open circuit voltage of 1.08 times,
The value of the fill factor was 1.1 times on average, and the photoelectric conversion efficiency η was 1.2 times on average.

Further, each of the solar cell manufactured in Example 1 (Sample No. 1) and the solar cell manufactured in Comparative Example 1 (Comparative Sample No. 1) was made into polyvinylidene fluoride (VDF).
It is vacuum-sealed with a protective film consisting of 1 and it is used under actual use conditions (installed outdoors, connecting a fixed resistance of 50 ohms to both electrodes).
After leaving for a year, the photoelectric conversion efficiency was evaluated again, and the deterioration rate due to light irradiation (the value of the photoelectric conversion efficiency damaged by the deterioration divided by the initial value of the photoelectric conversion efficiency) was examined. As a result, the deterioration rate of the solar cell having the diffusion prevention layer according to the present invention (Sample No. 1) was 6 as compared with the deterioration rate of the solar cell having no diffusion prevention layer (Comparative Sample No. 1).
It was kept as low as 5%.

Next, analysis of the depth profile of P of the solar cells manufactured in Example 1 (Sample No. 1) and Comparative Example 1 (Comparative Sample No. 1) was performed. First, the deposition chamber 1001 in FIG. 3 is equipped with a secondary ion mass spectrometer, and the n-type semiconductor layer 103 (or 203) and the diffusion prevention layer 104, i are prepared by the same method and under the same conditions as the solar cell of Example 1. Type semiconductor layer 105
(Or 204) and the p-type semiconductor layer 106 (or 2)
05) is formed, the substrate 1004 is transferred to the measurement chamber of the secondary ion mass spectrometer in a vacuum without being exposed to the atmosphere, and the distribution of P atoms in the depth direction (d) in the vicinity of the diffusion prevention layer is measured.
The analysis of the epth profile) was performed. As a result of the evaluation, as shown in FIG. 4, the solar cell of Example 1 (Sample N
o. As for the distribution of P in the depth direction in 1), since the diffusion prevention layer having a layer thickness of 10 Å exists, the P distribution changes sharply in the vicinity thereof, and the solar cell of Comparative Example 1 in which the diffusion prevention layer 104 is not provided (comparative) It was found that the diffusion of P into the i-type semiconductor layer was significantly smaller than that of Sample No. 1), and was suppressed almost completely.

From the above, the diffusion prevention layer of the present invention is P
Has the effect of suppressing the thermal diffusion of the solar cell and maintaining a steep ni junction, which dramatically improves the open circuit voltage, fill factor and photoelectric conversion efficiency η of the solar cell, and also improves reliability under actual use conditions. It turns out that it has improved significantly.

Example 2 The n-type semiconductor layer, the diffusion prevention layer, the i-type semiconductor layer, and the n-type semiconductor layer were prepared by the same method and conditions as in Example 1 except that the conditions for forming the diffusion prevention layer 104 were changed to those shown in Table 2. A p-type semiconductor layer, a transparent electrode and a current collecting electrode were sequentially formed to prepare a non-single crystalline silicon solar cell (Sample No. 2).

Next, the compositional analysis of the elements constituting the diffusion preventing layer formed under the conditions shown in Table 2 was conducted in the same manner as in Example 1. As a result, the main atoms constituting the diffusion prevention layer were Si and O, the ratio of which was 40%: 60%, and the other elements were below the detection limit. This value deviates from the stoichiometric ratio of silicon dioxide, and it was found that the diffusion prevention layer in Table 2 is a film having excess Si atoms.

Further, quantitative analysis of hydrogen (H) atoms present in the film of the diffusion preventing layer was carried out by the same method as in Example 1. As a result, it was found that the concentration of hydrogen (H) atoms in the diffusion prevention layer was extremely low at the detection limit (100 ppm) or less, and a very dense film was formed.

Further, by changing the gas flow rate ratio at the time of forming the diffusion prevention layer in various ways, only the composition ratio of silicon and oxygen in the diffusion prevention layer was changed to 10 types to prepare a solar cell (Sample No. .2) was manufactured by 5 sheets each, and the photoelectric conversion efficiency η was evaluated by the same method as described above, and the results shown in FIG. In FIG. 10, the relationship between the element composition ratio in the diffusion prevention layer and the photoelectric conversion efficiency is shown in the solar cell of Example 1 (Sample N).
o. The photoelectric conversion efficiency η of 1) is represented as 1. As is clear from FIG. 10, the diffusion prevention layer is Si _x O.
It was found that the value of photoelectric conversion efficiency was excellent in the case of _1-x (0.325 <x <0.34) and substantially stoichiometry.

Next, the depth profile of P of the solar cell in the case where the composition ratio of silicon and oxygen in the diffusion prevention layer was 40%: 60% was analyzed. As a result of the evaluation, the solar cell of Comparative Example 1 shown in FIG.
o. A slightly steep distribution of P was found in the vicinity of the diffusion prevention layer as compared with 1), but the solar cell of Example 1 (Sample N)
o. As compared with 1), diffusion of P into the i-type semiconductor layer was observed. As described above, in the solar cell of Example 1 provided with the diffusion preventing layer 104 having a substantially stoichiometric (stoichiometric) composition and a layer thickness of 10 Å, the substantially stoichiometric (chemical Non-stoichiometric composition and layer thickness of 10Å
It was found that the diffusion of P into the i-type semiconductor layer was significantly smaller than that of the solar cell of Example 2 in which the diffusion prevention layer of 1 was provided, and it was suppressed almost completely.

From the above, when the elemental composition of the diffusion prevention layer of the present invention is substantially stoichiometric (stoichiometric), thermal diffusion of P can be suppressed and a steep ni junction can be maintained. There is an effect, and the photoelectric conversion efficiency η of the solar cell is
Was found to improve dramatically.

Example 3 As shown in Table 3, the manufacturing conditions of the diffusion preventive layer 104 were changed by changing the DC bias voltage and the RF bias power to change the hydrogen atom concentration in the layer to 500 ppm, 1000 ppm and 2%.
Except that the n-type semiconductor layer, diffusion preventing layer, i-type semiconductor layer, p
Type semiconductor layer, a transparent electrode and a collector electrode are sequentially formed, and a non-single crystalline silicon solar cell (Sample No. 3-1, No. 3).
3-2 and No. 3-3) was created.

Next, the compositional analysis of the elements constituting the diffusion preventing layer formed under the conditions shown in Table 3 was conducted in the same manner as in Example 1. As a result, the main atoms constituting the diffusion prevention layer are Si and O, the ratio of which is 33.5%: 66.
5%, and other elements were below the detection limit. From this, it was found that the extremely thin diffusion barrier layer formed by the above manufacturing method and manufacturing conditions was substantially stoichiometric (stoichiometric) silicon dioxide (SiO ₂ ).

Further, quantitative analysis of hydrogen (H) atoms present in the film of the diffusion preventing layer was carried out by the same method as in Example 1. As a result, as shown in Table 3, by changing the DC bias voltage and the RF bias power, the hydrogen (H) atom concentration in the diffusion prevention layer was 500 ppm and 1000 p.
It was found that a pm and 2% film was formed.

Solar cells provided with diffusion barrier films having hydrogen atom concentrations of 500 ppm, 1000 ppm and 2% under the conditions of Table 3 (Samples No. 3-1, No. 3-2 and No. 3-). Each of 3) was manufactured, the photoelectric conversion efficiency η was evaluated by the same method as described above, and the dependence of the photoelectric conversion efficiency on the hydrogen atom concentration was investigated. As a result, the dependency shown in FIG. 5 was obtained. When compared with the solar cell of Comparative Example 1 having no diffusion prevention layer (Comparative Sample No. 1),
When the hydrogen atom concentration in the diffusion prevention layer is 1000 ppm or less, the photoelectric conversion efficiency is significantly improved, and particularly 500 ppm (Sample N
o. 3-1) was 1.09 times better, and 100 ppm or less (Sample No. 1) was 1.1 times better on average.

Next, these solar cells (Sample No. 3-
1 to No. 3-3) P distribution in the depth direction (depth)
Profile) was analyzed. As a result of the evaluation,
As the hydrogen atom concentration in the diffusion prevention layer decreases, FIG.
Distribution of P in the vicinity of the diffusion prevention layer gradually becomes steeper than that of Comparative Example 1 (Comparative Sample No. 1) of Comparative Example 1 of Comparative Example 1 (Comparative Sample No. 1).
It was found that the diffusion of P into the i-type semiconductor layer was almost completely suppressed as in 1).

From the above, when the hydrogen atom concentration in the diffusion prevention layer of the present invention is 500 ppm or less (particularly 100 ppm or less), there is an effect that thermal diffusion of P can be suppressed and a sharp ni junction can be maintained. Battery photoelectric conversion efficiency η
Was found to improve dramatically.

Example 4 The layer thickness of the diffusion prevention layer 104 was set to 4, 5, 2 as shown in Table 4.
An n-type semiconductor layer, a diffusion preventing layer, an i-type semiconductor layer, a p-type semiconductor layer, a transparent electrode and a current collecting electrode are sequentially formed by the same method and preparation conditions as in Example 1 except that 0 and 30Å are changed. Non-single crystalline silicon solar cell (Sample No. 4
-1, No. 4-2, No. 4-3 and No. 4-
4) was created.

Next, the compositional analysis of the elements constituting the diffusion barrier layer formed under the conditions shown in Table 4 was conducted in the same manner as in Example 1. As a result, the main atoms constituting the diffusion prevention layer are Si and O, and the ratio thereof is 33.5%: 66.5.
%, And other elements were below the detection limit. From this, it was found that the extremely thin diffusion barrier layer formed by the above manufacturing method and manufacturing conditions was substantially stoichiometric (stoichiometric) silicon dioxide (SiO ₂ ).

Further, quantitative analysis of hydrogen (H) atoms existing in the film of the diffusion prevention layer was carried out by the same method as in Example 1. As a result, it was found that the concentration of hydrogen (H) atoms in the diffusion prevention layer was extremely low at the detection limit (100 ppm) or less, and a very dense film was formed.

Layer thicknesses 4, 5, 20 and 3 under the conditions of Table 4.
No. 0 solar cell provided with a diffusion prevention layer (Sample No. 4-1,
No. 4-2, No. 4-3 and No. 4-4) were prepared for each 5 sheets, the photoelectric conversion efficiency η was evaluated by the same method as described above, and the dependency of the photoelectric conversion efficiency on the layer thickness of the diffusion prevention layer was investigated. As a result, the dependency shown in FIG. 6 was obtained. If the diffusion prevention layer thickness is 20 Å or more, the photoelectric conversion efficiency decreases because the series resistance of the solar cell increases, but the photoelectric conversion efficiency improves when the layer thickness is in the range of 5 to 20 Å, especially when the layer thickness is 10 Å (Sample No. In 1), the photovoltaic conversion efficiency η of the solar cell was 1.1 times better on average than the solar cell having no diffusion prevention layer (Comparative Sample No. 1).

Next, these solar cells (Sample No. 4-
1, No. 4-2, No. 4-3 and No. 4-4)
An analysis of the depth profile of P was performed. As a result of the evaluation, as the thickness of the diffusion prevention layer increased, the distribution of P in the vicinity of the diffusion prevention layer gradually became steeper than that of Comparative Example 1 (Comparative Sample No. 1) in FIG. 4, and especially the layer thickness was 5 Å or more. Then, in Example 1 of FIG.
It was found that the diffusion of P into the i-type semiconductor layer was almost completely suppressed as in 1), and that the layer thickness was required to be at least 5Å.

From the above, when the layer thickness of the diffusion prevention layer of the present invention is in the range of 5 to 20 Å (particularly 10 Å), there is an effect that thermal diffusion of P can be suppressed and a sharp ni junction can be maintained. It was found that the photoelectric conversion efficiency η of the battery was dramatically improved.

Example 5 As shown in FIG. 7, a solar cell to be prepared was used as a glass substrate 7
02, a transparent electrode 703, a p-type semiconductor layer 704, a diffusion prevention layer 705, an i-type semiconductor layer 706, and an n-type semiconductor layer 707.
And the back electrode 708 in that order, and the transparent electrode, the p-type semiconductor layer, the diffusion prevention layer, and the i layer were formed in the same manner as in Example 1 except that each layer was formed under the conditions shown in Table 5. A non-single crystalline silicon solar cell 701 is formed by forming a type semiconductor layer and an n-type semiconductor layer, and forming the back surface electrode 708 on almost the entire surface of the solar cell by the same forming method as the collecting electrode in the first embodiment. (Sample No. 5).

Next, the compositional analysis of the elements constituting the diffusion barrier layer formed under the conditions shown in Table 5 was conducted in the same manner as in Example 1. As a result, the main atoms constituting the diffusion prevention layer are Si and O, the ratio of which is 32.6%: 67.
4%, and other elements were below the detection limit. From this, it was found that the extremely thin diffusion barrier layer formed by the above manufacturing method and manufacturing conditions was substantially stoichiometric (stoichiometric) silicon dioxide (SiO ₂ ).

Further, a quantitative analysis of hydrogen (H) atoms existing in the film of the diffusion preventing layer was carried out by the same method as in Example 1. As a result, it was found that the concentration of hydrogen (H) atoms in the diffusion prevention layer was extremely low at the detection limit (100 ppm) or less, and a very dense film was formed.

Further, in the deposition chamber 1001 shown in FIG.
Equipped with M device (HITACHI H8000),
After forming the p-type semiconductor layer on the p-type semiconductor layer by the same method and under the same conditions as the solar cell manufacturing method described above, the substrate 1004 is transferred to the measurement chamber of the TEM device in a vacuum without being exposed to the atmosphere, and the p-type semiconductor layer is formed. When the crystallinity of the semiconductor layer was evaluated,
It was found that the non-single crystalline silicon forming the p-type semiconductor layer has microcrystallinity.

Further, after forming the p-type semiconductor layer and the diffusion prevention layer on the p-type semiconductor layer by the same method and under the same conditions as the above solar cell manufacturing method, the substrate 1004 is taken out and the cross section is polished, and then the STM device (digital Observation using an instrument Nanoscope AFM) confirmed that crystal grains were not in direct contact with each other at the interface between the p-type semiconductor layer and the diffusion prevention layer, and an amorphous semiconductor layer was interposed. .

Comparative Example 2 Except that the diffusion prevention layer 705 was not formed on the p-type semiconductor layer and the i-type semiconductor layer was continuously formed on the p-type semiconductor layer.
According to the same method and preparation conditions as in Example 5, the transparent electrode, p
A non-single crystalline silicon solar cell was prepared by forming a type semiconductor layer, a diffusion prevention layer, an i type semiconductor layer, an n type semiconductor layer and a back electrode (Comparative Sample No. 2).

Five solar cells of each of Example 5 and Comparative Example 2 were manufactured, and the photoelectric conversion efficiency η was evaluated by the same method as described above. As a result of the evaluation, as compared with Comparative Example 2 (Comparative Sample No. 2), Example 5 (Sample No. 5)
Had an average photoelectric conversion efficiency η of 1.1 times.

In the solar cells of Example 5 and Comparative Example 2, the depth profile of boron (B) was measured.
File) was analyzed in the same manner as in Comparative Example 1. As a result of the evaluation, as shown in FIG. 8, the solar cell of Example 5 (Sample N
o. In the depth direction distribution of boron (B) in 5), since the diffusion prevention layer exists, the distribution is steep in the vicinity thereof, and the distribution of boron (B) is larger than that of the solar cell of Comparative Example 2 (Comparative Sample No. 2). It was found that the diffusion of Al into the i-type semiconductor layer was significantly small and was almost completely suppressed.

From the above, the diffusion prevention layer of the present invention has the effect of suppressing the thermal diffusion of boron (B) and maintaining a steep pi junction, which results in the photoelectric conversion efficiency η of the solar cell.
Was found to improve dramatically.

Example 6 A solar cell shown in FIG. 9 was prepared. The solar cell shown in FIG. 9 has an n-type semiconductor layer (1) 90 on a stainless steel substrate 902.
3, diffusion prevention layer (1) 904, i-type semiconductor layer (1) 90
5, diffusion prevention layer (2) 906, p-type semiconductor layer (1) 90
7, diffusion prevention layer (3) 908, n-type semiconductor layer (2) 90
9, diffusion prevention layer (4) 910, i-type semiconductor layer (2) 91
1, diffusion prevention layer (5) 912, p-type semiconductor layer (2) 91
3, the transparent electrode 914 and the current collecting electrode 915 are formed in this order. The formation of each layer was performed in the same manner as in Example 1 except that the conditions shown in Table 6 were used to form an n-type semiconductor layer, an i-type semiconductor layer, a p-type semiconductor layer, a diffusion prevention layer, a transparent electrode and a collector electrode. Formed. Thus, a non-single crystalline silicon solar cell having a so-called laminated structure was prepared (Sample No. 6).

Next, the composition of the elements constituting the diffusion barrier layer formed under the conditions shown in Table 6 was analyzed in the same manner as in Example 1. As a result, the main atoms constituting the diffusion prevention layer were Si and O, the ratio was 34%: 66%, and the other elements were below the detection limit. From this,
The extremely thin diffusion barrier layer formed by the above manufacturing method and manufacturing conditions is substantially stoichiometric (stoichiometric).
It was found to be silicon dioxide (SiO ₂ ).

Further, quantitative analysis of hydrogen (H) atoms present in the film of the diffusion prevention layer was carried out by the same method as in Example 1. As a result, it was found that the concentration of hydrogen (H) atoms in the diffusion prevention layer was extremely low at the detection limit (100 ppm) or less, and a very dense film was formed.

When the crystallinity of the p-type and n-type semiconductor layers was evaluated by the same method as in Example 1, the non-single crystalline silicon forming the p-type and n-type semiconductor layers was found to be fine. It was found to have crystallinity.

When the interface between the p-type and n-type semiconductor layers and the diffusion prevention layer was observed by the same method as in Example 1, p
It was confirmed that the crystal grains were not in direct contact with each other at the interface between the n-type and n-type semiconductor layers and the diffusion preventing layer, and that an amorphous semiconductor layer was interposed.

Comparative Example 3 Five diffusion preventing layers (1) to (5) (904 in FIG. 9)
906, 908, 910 and 912), except that not all are formed, and the same method and manufacturing conditions as in Example 6,
An n-type semiconductor layer, an i-type semiconductor layer, a p-type semiconductor layer, a diffusion prevention layer, a transparent electrode and a current collecting electrode were formed to prepare a conventional laminated non-single crystalline silicon solar cell (Comparative Sample No.
3).

Five solar cells of Example 6 (Sample No. 6) and five solar cells of Comparative Example 3 (Comparative Sample No. 3) were produced, and the photoelectric conversion efficiency η was evaluated by the same method as described above. did. As a result of the evaluation, the comparative sample No. In comparison with Sample No. 3, 6, the photoelectric conversion efficiency η is 1.
It was 1x better.

Sample No. 6 and comparative sample No. As a result of evaluating the depth profile of boron (B) and P in each of the solar cells of Sample No. 3, sample No. The distribution of boron (B) and P in the depth direction in the solar cell of No. 6 is steep in the vicinity of each junction because of the presence of the diffusion prevention layer.
It was found that the diffusion of boron (B) into the i-type semiconductor layer and the diffusion of P into the i-layer were significantly smaller than those of the solar cell of Example 3, and were almost completely suppressed.

From the above, the diffusion prevention layer of the present invention has the effect of suppressing the thermal diffusion of boron (B) and P to the i layer and maintaining a steep pi junction and ni junction. It has been found that the photoelectric conversion efficiency η of is dramatically improved.

[0116]

[Table 1]

[0117]

[Table 2]

[0118]

[Table 3]

[0119]

[Table 4]

[0120]

[Table 5]

[0121]

[Table 6]

[0122]

As described above, the first non-single crystalline layer containing at least silicon atoms and the first non-single crystalline layer containing at least silicon atoms have different conductivity types. A second non-single crystalline layer is laminated to form a first
Between the first non-single crystalline layer and the second non-single crystalline layer of Si _x O
_1-x (0.325 <x <0.34), which is substantially stoichiometric and has a hydrogen content of 500 pp
The following effects can be obtained in the solar cell of the present invention, which is characterized by being provided with a layer having a thickness of m or less.

That is, by providing a diffusion preventing layer at the pi interface or the ni interface, which can effectively prevent the dopants of the p layer and the n layer from thermally diffusing into the i layer during film formation,
It is possible to provide a solar cell having improved output characteristics, particularly open circuit voltage and fill factor, and as a result, improved output characteristics.

Further, by providing an effective diffusion prevention layer at the pi interface or the ni interface to prevent the diffusion of the dopant in the actual use state, deterioration of the solar cell can be reduced, and as a result, a solar cell with improved reliability can be obtained. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram for explaining a layer configuration of a non-single crystalline silicon solar cell according to the present invention.

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

FIG. 3 is a schematic explanatory view of a deposition apparatus when using a microwave glow discharge method to form the solar cell of the present invention.

FIG. 4 is an explanatory diagram showing distributions of P concentration in the depth direction in a solar cell according to the present invention and a conventional solar cell.

FIG. 5 is an explanatory diagram showing the dependence of photoelectric conversion efficiency on the hydrogen atom concentration in the diffusion prevention layer.

FIG. 6 is an explanatory diagram showing the dependence of photoelectric conversion efficiency on the layer thickness of a diffusion prevention layer.

FIG. 7 is a schematic configuration diagram for explaining a layer configuration of a solar cell according to the present invention formed on an insulating substrate.

FIG. 8 is an explanatory diagram showing the distribution of boron (B) concentration in the solar cell according to the present invention and the conventional solar cell in the depth direction.

FIG. 9 is a schematic configuration diagram for explaining a layer configuration of a laminated non-single crystalline silicon solar cell according to the present invention.

FIG. 10 is a graph showing the relationship between the elemental composition ratio in the diffusion prevention layer and the photoelectric conversion efficiency, where the photoelectric conversion efficiency η of the solar cell of Example 1 is 1.

[Explanation of symbols]

101 Overall View of Solar Cell According to the Present Invention 102 Conductive Substrate 103 n-Type Semiconductor Layer 104 Diffusion Prevention Layer 105 i-Type Semiconductor Layer 106 p-Type Semiconductor Layer 107 Transparent Electrode 108 Current Collection Electrode 109 Lead-out Electrode 201 Overall View of Conventional Solar Cell 202 conductive substrate 203 n-type semiconductor layer 204 i-type semiconductor layer 205 p-type semiconductor layer 206 transparent electrode 207 current collecting electrode 208 extraction electrode 1000 μW film forming apparatus by glow discharge decomposition method 1001 deposition chamber 1002 dielectric window 1003 gas introduction tube 1004 substrate 1005 support base 1005 'heating heater 1006 vacuum gauge 1007 conductance valve 1008 auxiliary valve 1009 leak valve 1010 waveguide 1011 direct current power supply 1012 high frequency power supply 1013 bias applying electrode 1014 mesh-shaped grip 1020 raw material gas supply device 1021,1022,1023,1024,1025,
1026 Mass Flow Controller 1031, 1032, 1033, 1034, 1035
1036 gas inflow valve 1041, 1042, 1043, 1044, 1045
1046 Gas outflow valve 1051, 1052, 1053, 1054, 1055
1056 Raw material gas cylinder valve 1061, 1062, 1063, 1064, 1065
1066 Pressure regulator 1071, 1072, 1073, 1074, 1075
1076 Raw material gas cylinder 701 Overall view of solar cell according to the present invention 702 Insulating substrate 703 Transparent electrode 704 p-type semiconductor layer 705 Diffusion prevention layer 706 i-type semiconductor layer 707 n-type semiconductor layer 708 Backside electrode 709 Lead electrode 901 Laminated type according to the present invention Structural diagram of solar cell 902 Conductive substrate 903 n-type semiconductor layer (1) 904 Diffusion prevention layer (1) 905 i-type semiconductor layer (1) 906 Diffusion prevention layer (2) 907 p-type semiconductor layer (1) 908 Diffusion prevention Layer (3) 909 n-type semiconductor layer (2) 910 diffusion prevention layer (4) 911 i-type semiconductor layer (2) 912 diffusion prevention layer (5) 913 p-type semiconductor layer (2) 914 transparent electrode 915 current collecting electrode 916 Extraction electrode

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tatsuyuki Aoike 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Mitsuyuki Niwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. A first non-single crystalline layer containing at least silicon atoms and a first non-single crystalline layer containing at least silicon atoms.
Between a first non-single crystalline layer and a second non-single crystalline layer in a solar cell in which a second non-single crystalline layer having a conductivity type different from that of And Si _x O _1-x (0.3
25 <x <0.34), which is substantially stoichiometric and is provided with a layer having a hydrogen content of 500 ppm or less.