Photovoltaic device

A photovoltaic device includes a conductive substrate, a semiconductor layer formed on the conductive substrate and made of a non-single-crystal semiconductor material containing at least silicon atoms, and a transparent electrode stacked on the semiconductor layer, wherein the transparent electrode is made of a conductive oxide containing carbon atoms, nitrogen atoms, or both and the carbon and/or nitrogen atoms are contained in larger quantities in the portion of the transparent electrode adjacent to the semiconductor layer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a photovoltaic device for use in a solar 
battery, a photosensor, or the like, the photovoltaic device being 
constituted by stacking a semiconductor layer made of non-single-crystal 
semiconductor material, which contains silicon atoms, and a transparent 
electrode made of an indium oxide, a tin oxide, an indium-tin oxide or the 
like. More particularly, the present invention relates to a photovoltaic 
device made of amorphous silicon type semiconductor material (fine crystal 
silicon type semiconductor material included) or polycrystal silicon type 
semiconductor material as the non-single-crystal semiconductor material. 
2. Related Background Art 
A transparent electrode is an important component which relates to the 
performance of a photovoltaic device. Hitherto, the transparent electrode 
has been made of an indium oxide, a tin oxide, or an indium-tin oxide 
formed into a film by depositing the employed material by spraying, vacuum 
evaporating, ion plating, sputtering or the like. 
The light transmissivity and the specific resistance of the transparent 
electrode, thus formed, are parameters which directly relate to the 
performance of the photovoltaic device. Also conditions under which the 
transparent electrode is deposited, for example, the temperature of the 
substrate, the degree of vacuum, the deposition speed, and the like are 
important parameters which affect the quality of the semiconductor layer 
which is positioned adjacent to the transparent electrode. 
Results of a study of the relationship between the photovoltaic device and 
the transparent electrode have been recently disclosed in "Optical 
Absorption of Transparent Conducting Oxides and Power Dissipation in 
a-Si:H pin Solar Cells Measured by Photothermal Deflection Spectroscopy," 
by F LeBlanc and J. Perrin et al., Technical Digest of the International 
PVSEC-5, Kyoto, Japan, 1990, pg. 253, and "Improvement of Interface 
Properties of TCO/p-layer in pin-type Amorphous Silicon Solar Cells," by 
Y. Ashida, N. Ishida, and N. Ishiguro et al., Technical Digest of the 
International PVSEC-5, Kyoto, Japan, 1990, pg. 367. 
Furthermore, a method of reducing the resistance of the transparent 
electrode by stacking an indium oxide film and a tin oxide film has been 
disclosed in Japanese Laid-Open Patent Application No. 54-134396. 
However, there is a desire to further reduce the resistance of the 
conventional transparent electrode composed of indium oxide, tin oxide, or 
indium-tin oxide. 
Furthermore, the transmissivity, the photovoltaic force, and the 
photoelectric current must be further improved. 
Since photovoltaic devices have been widely used recently in a variety of 
conditions, a separation has taken place between the transparent electrode 
and the layer which is positioned in contact with the transparent layer, 
depending upon the conditions of use. 
In addition, the problem of short circuits may arise when the photovoltaic 
device is repeatedly subjected to a heat cycle for an excessively long 
time. 
SUMMARY OF THE INVENTION 
An object of the present invention is to overcome the aforementioned 
problems experienced with the conventional photovoltaic device. 
Another object of the present invention is to provide a photovoltaic device 
having a transparent electrode free from distortion and exhibiting large 
photovoltaic force and photoelectric current. 
Another object of the present invention is to provide a photovoltaic device 
having a uniform non-single-crystal semiconductor layer, which is 
deposited on a transparent electrode thereof, and which is free from 
abnormal deposition. 
Another object of the present invention is to provide a photovoltaic device 
exhibiting stable characteristics. 
Another object of the present invention is to provide a photovoltaic device 
which is free from separation of the layers thereof because the structural 
distortion between the transparent electrode and the semiconductor layer 
adjacent to the transparent electrode can be considerably prevented. 
Another object of the present invention is to provide a photovoltaic device 
which can be manufactured with a satisfactory manufacturing yield. 
As a result of a study to overcome the aforementioned problems and to 
achieve the aforementioned objects, the following optimum structure was 
found. 
Therefore, according to the present invention, there is provided a 
photovoltaic device having a conductive substrate on which semiconductor 
layers composed of a p-type layer, an i-type layer, and an n-type layer 
made of non-single-crystal semiconductor materials which contain at least 
silicon atoms are stacked, and also having a transparent electrode stacked 
on the semiconductor layers, wherein the transparent electrode is made of 
an oxide such as an indium oxide, a tin oxide, or an indium-tin oxide 
which contains carbon and/or nitrogen atoms, and the carbon and/or 
nitrogen atoms are distributed in the transparent electrode in the region 
adjacent to the semiconductor layer in a larger quantity than in a region 
opposite to the semiconductor layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments of the present invention will now be described. 
However, the present invention is not limited to the descriptions made 
hereinafter. 
FIGS. 1 and 2 are schematic views which illustrate photovoltaic devices 
100, 200 according to the present invention. 
The photovoltaic device 100 according to the present invention is, as shown 
in FIG. 1, composed of an opaque and conductive substrate 101 having, in 
order on the upper surface thereof, a light reflective (conductive) layer 
102, a reflection promoting layer 103, an n- or p-type non-single-crystal 
silicon semiconductor layer 104, an i-type (substantially intrinsic) 
non-single-crystal silicon semiconductor layer 105, a p- or n-type 
non-single-crystal silicon semiconductor layer 106, a transparent 
electrode 107 containing carbon atoms, nitrogen atoms, or carbon and 
nitrogen atoms in a relatively larger quantity in the region adjacent to 
the semiconductor layer, and a current collecting electrode 108. The 
photovoltaic device, thus constituted, is irradiated with light 109 
incident from above the transparent electrode 107. 
The photovoltaic device 200 according to the present invention and shown in 
FIG. 2 is formed in a tandem structure composed of a transparent 
superstrate 201 having, on the lower surface thereof, a current collecting 
electrode 208, a transparent electrode 207 containing carbon atoms, 
nitrogen atoms, or carbon and nitrogen atoms in a relatively larger 
quantity in the region adjacent to the semiconductor layer, a p- or n-type 
non-single-crystal silicon semiconductor layer 206b, an i-type 
(substantially intrinsic) non-single-crystal silicon semiconductor layer 
205b, an n- or p-type silicon semiconductor layer 204b, a p- or n-type 
non-single-crystal silicon semiconductor layer 206a, an i-type 
(substantially intrinsic) non-single-crystal silicon layer 205a, an n- or 
p-type non-single-crystal silicon semiconductor layer 204a, a reflection 
promoting layer 203, a light reflective (conductive) layer 202, and a 
conductive (and/or protection) layer 210. The photovoltaic device 200, 
thus constituted, is irradiated with light 209 incident from above the 
transparent superstrate 201. 
Furthermore, a triple-type photovoltaic device formed by stacking three pin 
units is also adaptable to the present invention, although omitted from 
illustration. 
Transparent Electrode 
The photovoltaic device according to the present invention has a 
transparent electrode in which carbon atoms, nitrogen atoms, or carbon and 
nitrogen atoms are contained in a tin oxide, an indium oxide, or an 
indium-tin oxide. 
The transparent electrode, in which carbon atoms, nitrogen atoms, or carbon 
and nitrogen atoms are contained in a tin oxide, an indium oxide, or an 
indium-tin oxide, has characteristics such that the crystal particle size 
of the oxide, which constitutes the transparent electrode, is enlarged, 
and dispersion of the crystal particle size range is reduced. Furthermore, 
the presence of the carbon atoms or the nitrogen atoms in the transparent 
electrode will prevent distortion of the transparent electrode. As a 
result, the specific resistance of the transparent electrode is reduced 
and the transmissivity improved. 
Furthermore, the fact that the transparent electrode contains the carbon 
atoms or the nitrogen atoms will smooth the shape of the crystals of the 
aforementioned oxide which forms the transparent electrode, causing the 
surface property (for example, the smoothness) of the transparent 
electrode to be improved. In particular, when the transparent electrode is 
formed on the semiconductor layer, the distortion between the 
semiconductor layer and the transparent electrode can be reduced, causing 
the adhesion between them to be significantly improved. In addition, 
abnormal deposition of the non-single-crystal silicon semiconductor layer 
can be reduced when the non-single-crystal silicon semiconductor layer is 
deposited on the transparent electrode. Hence, even if a thin p- or n-type 
layer is deposited, a leakage current can be reduced. Therefore, average 
characteristics of the photovoltaic device can be improved. 
Furthermore, since a relatively larger quantity of the carbon or nitrogen 
atoms is distributed in the region of the transparent electrode adjacent 
to the semiconductor layer, the structural distortion due to the 
difference in material between the transparent electrode and the 
semiconductor layer can be reduced. 
It is preferable that the distribution of the carbon atoms or the nitrogen 
atoms contained in the transparent electrode be decreased in an 
exponential manner from a position adjacent to the boundary between the 
transparent electrode and the semiconductor layer toward the inside 
portion of the transparent electrode. The fact that the carbon atoms or 
the nitrogen atoms in the transparent electrode are decreased in the 
exponential manner will further reduce the structural distortion due to 
the difference in material between the transparent electrode and the 
semiconductor layer. Furthermore, changes due to the dispersion of the 
carbon atoms or the nitrogen atoms with time can be minimized. 
It is preferable that the range in which the carbon atoms or the nitrogen 
atoms are distributed in the exponential manner be from 3 nm to 50 nm. 
In the transparent electrode according to the present invention containing 
carbon atoms or nitrogen atoms, the temperature at which a satisfactory 
quality transparent electrode can be formed is lowered since the carbon 
atoms affect the growth of the crystals of the oxide, although the details 
have not been clarified yet. Therefore, excellent characteristics can be 
obtained even if the temperature is at a relatively low level. 
The transparent electrode containing the carbon atoms or the nitrogen atoms 
according to the present invention is deposited as follows. 
An optimum deposition method to deposit the transparent electrode 
containing the carbon atoms or the nitrogen atoms according to the present 
invention is sputtering or vacuum evaporation. 
Furthermore, DC magnetron sputtering apparatus 300 schematically shown in 
FIG. 3 exemplifies a sputtering apparatus suitable to deposit the 
transparent electrode containing carbon atoms or nitrogen atoms according 
to the present invention. 
The DC magnetron sputtering apparatus 300 is composed of a deposition 
chamber 301, a substrate 302, a heater 303, targets 304 and 308, 
insulating supporting members 305 and 309, DC power sources 306 and 310, 
shutters 307 and 311, a vacuum gauge 312, a conductance valve 313, gas 
introduction valves 314, 315, and 316, and mass flow controllers 317, 318, 
and 319. 
When a transparent electrode made of a tin oxide containing carbon atoms or 
nitrogen atoms according to the present invention is deposited on a 
substrate by using the DC magnetron sputtering apparatus 300, the target 
comprises carbon atoms or nitrogen atoms contained in metallic tin (Sn) or 
tin oxide (SnO.sub.2). 
When the transparent electrode according to the present invention is made 
of an indium oxide containing carbon atoms or nitrogen atoms, the target 
is made from a material which comprises carbon atoms or nitrogen atoms 
contained in metallic indium (In) or an indium oxide (In.sub.3 O.sub.3). 
When the transparent electrode according to the present invention is made 
of indium-tin oxide containing carbon atoms or nitrogen atoms, the target 
is made by combining metallic tin, metallic indium, a tin-indium metal 
alloy, a tin oxide, an indium-tin oxide, and an indium-tin oxide which 
contains carbon atoms or nitrogen atoms. If an arrangement is made such 
that a plurality of targets having different carbon or nitrogen atom 
contents are prepared and the aperture ratio of a shutter which 
corresponds to the target can be changed, the distribution of the content 
of the carbon or nitrogen atoms in the transparent electrode can be 
changed. 
As a starting material for generating carbon atoms to be contained by the 
target, graphitic carbon or diamond-shaped carbon is suitable. 
When the transparent electrode according to the present invention is 
deposited by a reactive sputtering method, the following process can be 
employed in which the aforementioned target and/or a target which does not 
contain carbon atoms or nitrogen atoms are combined and a raw material gas 
containing carbon atoms or nitrogen atoms is introduced into the 
deposition chamber or the nitrogen atoms are introduced into the 
transparent electrode by utilizing plasma energy. In this case, the 
distribution of the carbon atoms or the nitrogen atoms in the transparent 
electrode can be controlled by changing the quantity of the raw material 
gas which contains the carbon atoms or the nitrogen atoms introduced into 
the deposition chamber. 
Raw material gases containing carbon atoms which can be adapted to the 
reactive sputtering method are exemplified by CH.sub.4, CD.sub.4, C.sub.n 
H.sub.2n+2 (n is an integer), C.sub.n H.sub.2n (n is an integer), C.sub.2 
H.sub.2, C.sub.6 H.sub.6, CO.sub.2, CO, and the like. 
As raw material gases containing nitrogen atoms which can be adapted to the 
reactive sputtering method, N.sub.2, NH.sub.3, ND.sub.3, NO, NO.sub.2, 
N.sub.2 O, and the like are exemplified. 
It is preferable to make the maximum distribution density of carbon atoms 
or nitrogen atoms contained in the transparent electrode according to the 
present invention in the range from 5 ppm or more to 1000 ppm or less. 
Furthermore, it is preferable that the maximum quantity of carbon atoms or 
nitrogen atoms contained in the aforementioned target be 1000 ppm in order 
to cause the carbon atoms or the nitrogen atoms contained by the 
transparent electrode to be distributed in the maximum distribution 
density range from 5 ppm or more to 1000 ppm or less, although it depends 
considerably on the sputtering conditions. 
In order to cause carbon atoms or nitrogen atoms to be contained by the 
transparent electrode in the maximum distribution density of 1000 ppm or 
less by the sputtering method, it is preferable that the maximum amount of 
the gas containing carbon atoms or nitrogen atoms to be mixed with the 
sputtering gas be about 2000 ppm or less. 
In the case where the transparent electrode containing carbon atoms or 
nitrogen atoms is deposited by the sputtering method, the temperature of 
the substrate is an important factor and is preferably in a range from 
25.degree. C. to 600.degree. C. In particular, the transparent electrodes 
containing carbon atoms or nitrogen atoms, according to the present 
invention, exhibit excellent characteristics in comparison with the 
conventional technology in a temperature range from 25.degree. C. to 
250.degree. C. Furthermore, the sputtering gas for use in the case where 
the transparent electrode containing carbon atoms or nitrogen atoms, 
according to the present invention, is deposited by the sputtering method 
is an inert gas exemplified by argon (Ar), neon (Ne), xenon (Xe), helium 
(He), or the like. In particular, it is most preferable to employ Ar. In 
addition, it is preferable to add oxygen (O.sub.2) to the inert gas if 
necessary. In particular, the oxygen (O.sub.2) is required in the case 
where the target is made of metal. 
In the case where the target is sputtered by the inert gas or the like, it 
is preferable to make the pressure in the discharge space in the range 
from 0.1 to 50 mTorr in order to effectively perform the sputtering 
operation. 
In addition, a DC or an RF power supply is preferred as the power source to 
be employed in the sputtering method. A preferred electric power is 10 to 
1000 W during sputtering. 
An optimum deposition speed at which the transparent electrode containing 
carbon atoms or nitrogen atoms is formed according to the present 
invention is in the range from 0.01 to 10 nm/sec, although it depends upon 
the pressure and the electric discharge power in the discharge space. 
The second method adaptable to depositing the transparent electrode 
containing carbon atoms or nitrogen atoms, according to the present 
invention, is the vacuum evaporation method. 
A vacuum evaporation apparatus 500 is, as schematically shown in FIG. 5, 
composed of a deposition chamber 501, a substrate 502, a heater 503, an 
evaporation source 504, a conductance valve 509, gas introduction valves 
510 and 512, mass flow controllers 511 and 513 or the like. 
As a preferred evaporation source employed for depositing the transparent 
electrode containing carbon atoms or nitrogen atoms, a material prepared 
by adding carbon atoms or nitrogen atoms to metallic tin, metallic indium 
or the indium-tin alloy is exemplified. It is preferable that the maximum 
content of carbon atoms or nitrogen atoms contained in the evaporation 
source be 1000 ppm or less. 
It is preferable that the temperature of the substrate during deposition of 
the transparent electrode containing carbon atoms or nitrogen atoms, 
according to the present invention, be in the range from 25.degree. C. to 
600.degree. C. 
In the case where the transparent electrode containing carbon atoms or 
nitrogen atoms is deposited, it is preferable to introduce the oxygen 
(O.sub.2) gas at a pressure of 5.times.10.sup.-5 Torr to 9.times.10.sup.-4 
Torr after the pressure in the deposition chamber has been lowered to a 
level of 10.sup.-6 Torr or lower. 
By introducing oxygen in the aforementioned range, the above-mentioned 
metal gasified from the evaporation source reacts with oxygen in the gas 
phase so that an excellent transparent electrode can be deposited. 
In the case where the transparent electrode containing carbon atoms or 
nitrogen atoms is deposited by the reactive evaporation, the transparent 
electrode may be deposited by evaporating the evaporation source and/or 
the other evaporation source which does not contain the carbon atoms or 
nitrogen atoms, in a state where the gas containing carbon atoms or 
nitrogen atoms has been introduced into the deposition chamber at a 
pressure lower than 5.times.10.sup.-4 Torr. In addition, a process may be 
employed in which RF electric power is introduced at the aforementioned 
degree of vacuum to generate plasma and the evaporation is performed via 
the plasma thus generated. By changing, with time, the quantity of the gas 
containing carbon atoms or nitrogen atoms to be introduced into the 
deposition chamber, the distribution of the carbon atoms or nitrogen atoms 
contained in the transparent electrode can be arbitrarily changed. Also by 
changing the speed at which the evaporation source is evaporated while 
making the quantity of the gas containing carbon atoms or nitrogen atoms 
introduced into the deposition chamber a constant, the distribution of the 
carbon atoms or nitrogen atoms contained in the transparent electrode can 
be arbitrarily changed. 
It is preferable to make the speed at which the transparent electrode is 
deposited under the aforementioned conditions be 0.01 to 10 nm/sec. If the 
deposition speed is lower the 0.01 nm/sec, the manufacturing yield will 
deteriorate. If it is higher than 10 nm/sec, a rough film is undesirably 
formed, causing the transmissivity, the conductivity, and the adhesion to 
deteriorate. 
The preferred thickness of the transparent electrode which contains carbon 
atoms or nitrogen atoms is such that the conditions required for an 
anti-reflection film can be met. Specifically, it is preferable that the 
thickness of the transparent electrode range from 50 nm to 300 nm. 
By causing carbon atoms to be simultaneously contained by the transparent 
electrode which contains nitrogen atoms, the characteristics of the 
photovoltaic device can be further improved. 
By causing nitrogen atoms and carbon atoms to be simultaneously contained 
by the transparent electrode, the durability against the heat cycle to 
which the photovoltaic device according to the present invention is 
subjected can be further improved. In addition, the flexibility of the 
transparent electrode can be further improved, whereby cracking of the 
photovoltaic device is prevented. 
It is preferable to make the quantities of carbon atoms and nitrogen atoms 
added to the transparent electrode of the photovoltaic device according to 
the present invention to be in the range of 100 ppm or less. 
Such carbon atoms are introduced into the transparent electrode by the same 
means and method as those employed when nitrogen atoms are introduced. 
By using a target or an evaporation source which contains carbon atoms for 
performing sputtering or vacuum evaporation for the purpose of depositing 
the transparent electrode, the transparent electrode may contain carbon 
atoms. It is preferable that a graphite-form carbon or diamond-form carbon 
be used as the carbon source material contained by the target and the 
evaporation source. 
In the case where the transparent electrode containing nitrogen atoms and 
carbon atoms is deposited by the reactive sputtering method, the following 
process may be employed: the aforementioned target and/or the target which 
does not contain carbon atoms are combined so that the sputtering target 
is obtained, the raw material gas containing carbon atoms is, in addition 
to the aforementioned raw material gas containing nitrogen atoms, 
introduced into the deposition chamber, and plasma energy is utilized, so 
that carbon atoms may be introduced into the transparent electrode along 
with nitrogen atoms. 
The raw material gas containing carbon atoms usable for the reactive 
sputtering may be made of a material exemplified by CH.sub.4, CD.sub.4, 
C.sub.n H.sub.2n+2 (n is an integer), C.sub.n H.sub.2n (n is integer), 
C.sub.2 H.sub.2, C.sub.6 H.sub.6, CO.sub.2, CO, or the like. 
In the case where the transparent electrode containing carbon atoms and 
nitrogen atoms is deposited by the reactive evaporation, the evaporation 
source and/or the evaporation source which does not contain carbon atoms 
are evaporated in a state where the gas containing carbon atoms has been 
introduced into the deposition chamber to a pressure level of 
5.times.10.sup.-4 Torr or less. Furthermore, a process may be employed in 
which RF electric power is introduced at the aforementioned degree of 
vacuum so as to generate plasma, and the evaporation may be performed via 
the plasma thus generated. 
p-type layer or n-type layer 
The p- or n-type layer of the photovoltaic device according to the present 
invention is an important layer which influences the characteristics of 
the photovoltaic device. 
The amorphous material (hereinafter expressed as "a-") and the fine crystal 
material (hereinafter expressed as ".mu.c-") of the p- or the n-type layer 
of the photovoltaic device according to the present invention are 
exemplified by: material prepared by adding, at a high density, a p-type 
valence controlling agent (B, Al, Ga, In, or Tl of group IIIA of the 
periodic table) or an n-type valence controlling agent (P, As, Sb, or Bi 
of group VA of the periodic table) to a-Si:H, a-Si:HX, a-SiC:H, a-SiC:HX, 
a-SiGe:H, a-SiGeC:H, a-SiO:H, a-SiN:H, a-SiON:HX, a-SiOCN:HX, .mu.c-Si:H, 
.mu.c-SiC:H, .mu.c-Si:HX, .mu.c-SiC:HX, .mu.c-SiGe:H, .mu.c-SiO:H, 
.mu.c-SiGe:H, SiN:H, .mu.c-SiON:HX, .mu.c-SiOCN:HX, or the like. The 
polycrystal material (hereinafter expressed as "poly-") is exemplified by 
a material prepared by adding, at a high density, a p-type valance 
controlling agent (B, A1, Ga, In, or T1 of group IIIA of the periodic 
table) or an n-type valence controlling agent (P, As, Sb, or Bi of group 
VA of the periodic table) to poly-Si:H, poly-Si:HX, poly-SiC:H, 
poly-SiC:HX, poly-SiGe:H, poly-Si, poly-SiC, poly-SiGe, or the like. 
In particular, it is preferable that the p-type layer or the n-type layer 
on which light is incident be made of a crystalline semiconductor layer 
with small light absorption or an amorphous semiconductor layer having a 
wide band gap. 
It is preferable that the addition of any one of the atoms of group IIIA of 
the periodic table to the p-type layer and of any one of the atoms of 
group VA of the periodic table to the n-type layer be in the range of 0.1 
to 50 atom %. 
Hydrogen atoms (H, D) or halogen atoms (X) contained by the p-type layer or 
the n-type layer act to compensate the non-bonded atoms of the p- or 
n-type layer, improving the doping efficiency of the p- or n-type layer. 
The optimum quantity of hydrogen atoms to be added to the p- or n-type 
layer is 0.1 to 40 atom %. In particular, in the case where the p- or the 
n-type layer is crystalline, the optimum quantity of hydrogen atoms or 
halogen atoms is in the range of 0.1 to 8 atom %. Furthermore, it is 
preferable that the hydrogen atoms and/or halogen atoms be distributed in 
a portion adjacent to the boundary between the p-type layer and the i-type 
layer and between the n-type layer and the i-type layer. In addition, it 
is preferable that the hydrogen atoms and/or halogen atoms distributed 
adjacent to the aforementioned boundaries be in the range from 1.1 to 2 
times the quantity of the same in the bulk. By causing hydrogen atoms or 
halogen atoms to be contained in a larger quantity in the portion adjacent 
to the boundaries between the p-type layer and the i-type layer and 
between the n-type layer and the i-type layer, defect levels or mechanical 
distortions which may take place adjacent to the aforementioned boundaries 
can be reduced. Therefore, the photovoltaic force and the photoelectric 
current of the photovoltaic device according to the present invention can 
be increased. 
In addition, it is preferable that a large quantity of hydrogen atoms 
and/or halogen atoms be distributed adjacent the boundary between the 
transparent electrode and the p-type layer or between the transparent 
electrode and the n-type layer. In addition, it is preferable that the 
hydrogen atoms and/or halogen atoms distributed adjacent to the 
aforementioned boundaries be in the range from 1.1 to 2 times the quantity 
of the same in the bulk. By causing hydrogen atoms or halogen atoms to be 
contained in a larger quantity in the portion adjacent to the boundaries 
between the transparent electrode and the p-type layer or between the 
transparent electrode and the n-type layer, defect levels or mechanical 
distortions which may take place adjacent to the aforementioned boundaries 
can be reduced. Therefore, the photovoltaic force and the optical electric 
current of the photovoltaic device according to the present invention can 
be increased. 
It is preferable that the activation energy of the p- or n-type layer of 
the photovoltaic device according to the present invention be 0.2 eV or 
less, more preferably 0.1 eV or less. Furthermore, it is preferable that 
the specific resistance be 100 .OMEGA.cm or less, more preferably 1 
.OMEGA.cm or less. In addition, it is preferable that the thickness of 
each of the p-type and the n-type layers be 1 to 50 nm, more preferably 3 
to 10 nm. 
As the raw material gas suitable for depositing the p-type or n-type layer 
of the photovoltaic device according the present invention, a compound 
which contains silicon atoms and can be gasified, a compound which 
contains germanium atoms and can be gasified, a compound which contains 
nitrogen atoms and can be gasified, and a gas mixture of the 
aforementioned compounds may be used. 
Specifically, the compound which contains silicon atoms and can be gasified 
is exemplified by SiH.sub.4, SiH.sub.6, SiF.sub.4, SiFH.sub.3, SiF.sub.2 
H.sub.2, SiF.sub.3 H, Si.sub.3 H.sub.8, SiD.sub.4, SiHD.sub.3, SiH.sub.2 
D.sub.2, SiH.sub.3 D, SiFD.sub.3, SiF.sub.2 D.sub.2, SiD.sub.3 H, Si.sub.2 
D.sub.3 H.sub.3, or the like. 
The compound which contains germanium atoms and can be gasified is 
exemplified by GeH.sub.4, GeD.sub.4, GeF.sub.4, GeFH.sub.3, GeF.sub.2 
H.sub.2, GeF.sub.3 H, GeHD.sub.3, GeH.sub.2 D.sub.2, GeH.sub.3 D, 
GeH.sub.6, GeD.sub.6, or the like. 
The compound which contains carbon atoms and can be gasified is exemplified 
by CH.sub.4, CD.sub.4, C.sub.n H.sub.2n+2 (n is an integer), C.sub.n 
H.sub.2n (n is an integer), C.sub.2 H.sub.2, C.sub.6 H.sub.6, CO.sub.2, 
CO, or the like. 
The gas containing nitrogen is exemplified by N.sub.2, NH.sub.3, ND.sub.3, 
NO, NO.sub.2, N.sub.2 O, or the like. 
The gas containing oxygen is exemplified by O.sub.2, CO, CO.sub.2, NO, 
NO.sub.2, N.sub.2 O, CH.sub.3 CH.sub.2 OH, CH.sub.3 OH, or the like. 
The material to be introduced into the p-type or n-type layer for the 
purpose of controlling the valence electrons is exemplified by atoms of 
group IIIA or VA of the periodic table. 
As an effective starting material for introducing the boron atoms of group 
IIIA, a boron hydride such as B.sub.2 H.sub.6, B.sub.4 H.sub.10, B.sub.5 
H.sub.9, B.sub.5 H.sub.11, B.sub.6 H.sub.10, B.sub.6 H.sub.12, B.sub.6 
H.sub.14, or the like, and halogen hydrides such as BF.sub.3, BCl.sub.3, 
or the like are exemplified. Also, AlCl.sub.3, GaCl.sub.3, INC.sub.3, 
TlCl.sub.3, or the like are exemplified. In particular, B.sub.2 H.sub.6 
and BF.sub.3 are suitable for use. 
As an effective starting material for introducing the phosphorus atoms of 
group VA, a phosphorus hydride such as PH.sub.3, P.sub.2 H.sub.4, or the 
like and a phosphorus halogenide such as PH.sub.4 I, PF.sub.3, PF.sub.5, 
PCl.sub.3, PCl.sub.5, PBr.sub.3, PBr.sub.5, PI.sub.3, or the like are 
exemplified. Also ASH.sub.3, AsF.sub.3, AsCl.sub.3, AsBr.sub.3, AsF.sub.5, 
SbH.sub.3, SbF.sub.3, SbF.sub.5, SbCl.sub.3, SbCl.sub.5, BiH.sub.3, 
BiCl.sub.3, BiBr.sub.3, or the like are exemplified. In particular, 
PH.sub.3 and PF.sub.3 are suitable for use. 
The p- or n-type layer of the photovoltaic device according to the present 
invention can be preferably deposited by an RF plasma CVD method or a 
.mu.W plasma CVD method. 
In the case where the RF plasma CVD method is employed to deposit the 
aforementioned layer, a capacitance coupled type RF plasma CVD method is 
suitable for use. 
In the case where the p- or n-type layer is deposited by the RF plasma CVD 
method, the optimum conditions are as follows: the temperature of the 
substrate in the deposition chamber is 100.degree. to 350.degree. C., the 
internal pressure is 0.1 to 10 Torr, the RF power is 0.05 to 1.0 
W/cm.sup.2 and the deposition speed is 0.01 to 3 nm/sec. 
The compound which can be gasified may be diluted with H.sub.2, He, Ne, Ar, 
Xe, Kr gas, or the like before it is introduced into the deposition 
chamber. 
In the case where the layer is made of a fine crystal semiconductor which 
does not absorb light considerably or a layer having a wide band gap is 
deposited, it is preferable to dilute the raw material with a hydrogen gas 
2 to 100 times and to introduce relatively large RF power. The preferred 
RF frequency is 1 MHz to 100 MHz, more preferably, a frequency near 13.56 
MHz. 
In the case where the p- or n-type layer suitable for the present invention 
is deposited by the .mu.W plasma CVD method, it is preferable to 
constitute the .mu.W plasma CVD apparatus in such a manner that microwaves 
are introduced into the deposition chamber through a wave guide pipe via a 
dielectric window (made of alumina ceramics or the like). 
In the case where the p- or n-type layer suitable for the present invention 
is deposited by the .mu.W plasma CVD method, it is preferable that the 
temperature of the substrate in the deposition chamber be 100.degree. to 
400.degree. C., the internal pressure be 0.5 to 30 mTorr, the .mu.W power 
be 0.01 to 1 W/cm.sup.3, and the frequency of .mu.W be 0.5 to 10 GHz. 
Furthermore, the aforementioned compound which can be gasified may be 
diluted with H.sub.2, He, Ne, Ar, Xe, Kr gas, or the like before it is 
introduced into the deposition chamber. 
In particular, in the case where a fine crystal semiconductor, or a layer 
such as a-SiC:H which does not considerably absorb light, or a layer which 
has a wide band gap is deposited, it is preferable that the raw material 
gas be diluted with a hydrogen gas 2 to 100 times and a relatively large 
.mu.W power be introduced. 
i-type layer 
The i-type layer of the photovoltaic device according to the present 
invention is an important layer for generating and transporting charge 
carriers when it is irradiated with light. 
As the i-type layer of the photovoltaic device according to the present 
invention, a slightly p-type layer or a slightly n-type layer may be used. 
In the case where a semiconductor layer is used in which the product of 
the mobility and lifetime of the positive holes is smaller than the 
product of the mobility and lifetime of the electrons is used, it is 
suitable to employ a slightly p-type layer. In the case where a 
semiconductor layer is used in which the product of the mobility and 
lifetime of the electrons is smaller than the product of the mobility and 
lifetime of the positive holes, it is suitable to employ a slightly n-type 
layer. 
The material for the i-type layer of the photovoltaic device according to 
the present invention is exemplified by an amorphous (hereinafter 
expressed as "a-") material such as a-Si:H, a-Si:HX, a-SiC:H, a-SiC:HX, 
a-SiGe:H, a-SiGe:HX, a-SiGeC:HX, or the like. 
In particular, it is preferable to use a material caused to be intrinsic 
type by adding, as a valence controlling agent, atoms of group IIIA and/or 
atoms of group VA of the periodic table to the aforementioned amorphous 
material. 
Hydrogen atoms (H, D) or halogen atoms (X) contained by the i-type layer 
act to compensate the non-bonded atoms of the i-type layer so as to cause 
the i-type layer to have an improved product of the mobility of the 
carrier and its lifetime. It further acts to compensate the level of the 
boundaries between the p-type layer and the i-type layer and between the 
n-type layer and the i-type layer, improving the photovoltaic force, the 
photoelectric current, and the light responsiveness of the photovoltaic 
device. It is preferable that hydrogen atoms and/or halogen atoms be 
contained by the i-type layer in an amount from 1 to 40 atom %. In 
particular, it is preferable that hydrogen atoms and/or halogen atoms be 
distributed in a larger quantity adjacent to the boundaries between the 
p-type layer and the i-type layer and between the n-type layer and the 
i-type layer. Furthermore, it is preferable to make the contents of 
hydrogen atoms and halogen atoms adjacent to the boundaries to be 1.1 to 2 
times the contents in the bulk. 
It is preferable that the thickness of the i-type layer be 0.1 to 1.0 .mu.m 
although it depends considerably on the structure (for example, a single 
cell, a tandem cell or a triple cell) of the photovoltaic device and the 
band gap of the i-type layer. 
It is preferable that the physical properties of the i-type layer be as 
follows: the mobility of electrons is 0.01 cm.sup.2 /V/sec or more, the 
mobility of the positive holes is 0.0001 cm.sup.2 /V/sec or more, the band 
gap is 1.1 to 2.2 eV, the local state density at the center of the 
forbidden zone is 10.sup.18 cm.sup.3 /eV or less, and the inclination of 
the Urbach tail adjacent to the valence zone is 65 meV or less. 
Furthermore, it is preferable that the current-voltage characteristics of 
the photovoltaic device according to the present invention are measured 
under AM 1.5, 100 mW/cm.sup.2, the curve fitting is performed by the Hecht 
method, and the product of the mobility and the lifetime obtained from the 
curve fitting is 10.sup.-10 cm.sup.2 /V or more. 
It is preferable that the band gap of the i-type layer be widened adjacent 
to the boundaries between the p-type layer and the i-type layer and 
between the n-type layer and the i-type layer. In this case, the 
photovoltaic force and the photoelectric current of the photovoltaic 
device can be increased and deterioration due to light irradiation after 
the photovoltaic device is used for a long time can be prevented. 
A raw material gas suitable to deposit the i-type layer of the photovoltaic 
device according to the present invention is exemplified by a compound 
which contains silicon atoms and can be gasified, a compound which 
contains germanium atoms and can be gasified, a compound which contains 
carbon atoms and can be gasified, a compound which contains nitrogen atoms 
and can be gasified, and a gaseous mixture of the aforementioned 
compounds. 
Specifically, the compound which contains silicon atoms and can be gasified 
is exemplified by SiH.sub.4, SiH.sub.6, SiF.sub.4, SiFH.sub.3, SiF.sub.2 
H.sub.2, SiF.sub.3 H, Si.sub.3 H.sub.8, SiD.sub.4, SiHD.sub.3, SiH.sub.2 
D.sub.2, SiH.sub.3 D, SiFD.sub.3, SiF.sub.2 D.sub.2, SiD.sub.3 H, Si.sub.2 
D.sub.3 H.sub.3, or the like. 
The compound which contains germanium atoms and can be gasified is 
exemplified by GeH.sub.4, GeD.sub.4, GeF.sub.4, GeFH.sub.3, GeF.sub.2 
H.sub.2, GeF.sub.3 H, GeHD.sub.3, GeH.sub.2 D.sub.2, GeH.sub.3 D, 
GeH.sub.6, GeD.sub.6, or the like. 
The compound which contains carbon atoms and can be gasified is exemplified 
by CH.sub.4, CD.sub.4, C.sub.n H.sub.2n+2 (n is an integer), C.sub.n 
H.sub.2n (n is an integer), C.sub.2 H.sub.2, C.sub.6 H.sub.6, or the like. 
The material to be introduced into the i-type layer for the purpose of 
controlling the valence electrons of the i-type layer is exemplified by 
atoms of group IIIA and those of group VA of the periodic table. 
An effective starting material according to the present invention for 
introducing atoms of group IIIA is exemplified by a boron hydride such as 
B.sub.2 H.sub.6, B.sub.4 H.sub.10, B.sub.5 H.sub.9, B.sub.5 H.sub.11, 
B.sub.6 H.sub.10, B.sub.6 H.sub.12, B.sub.6 H.sub.14, or the like and 
halogen hydrides such as BF.sub.3, BCl.sub.3, or the like. Also 
AlCl.sub.3, GaCl.sub.3, INCl.sub.3, T1Cl.sub.3, or the like are 
exemplified. 
As an effective starting material for introducing the phosphorous atoms of 
group VA, a phosphorous hydride such as PH.sub.3, P.sub.2 H.sub.4, or the 
like and a phosphorous halogenide such as PH.sub.4 I, PF.sub.3, PF.sub.5, 
PCl.sub.3, PCl.sub.5, PBr.sub.3, PBr.sub.5, PI.sub.3, or the like are 
exemplified. Also AsH.sub.3, AsF.sub.3, AsCl.sub.3, AsBr.sub.3, AsF.sub.5, 
SbH.sub.3, SbF.sub.3, SbF.sub.5, SbCl.sub.3, SbCl.sub.5, BiH.sub.3, 
BiCl.sub.3, BiBr.sub.3, or the like are exemplified. 
It is preferable that the quantity of atoms of groups IIIA and VA of the 
periodic table introduced into the i-type layer for the purpose of 
controlling the conductivity be 1000 ppm or less. 
The preferred methods for depositing the i-type layer adaptable to the 
present invention are exemplified by the RF plasma CVD method and the 
.mu.W plasma CVD method. When the RF plasma CVD method is employed, it is 
preferable to use a capacitance coupled type RF plasma CVD apparatus. 
When the i-type layer is deposited by the RF plasma CVD method, the optimum 
conditions are as follows: the temperature of the substrate in the 
deposition chamber is 100.degree. to 350.degree. C. the internal pressure 
is 0.1 to 10 Torr, the RF power is 0.05 to 10 W/cm.sup.2, and the 
deposition speed is 0.01 to 3 nm/sec. 
Furthermore, the compound which can be gasified may be arbitrarily diluted 
with H.sub.2, He, Ne, Ar, Xe, Kr gas, or the like before it is introduced 
into the deposition chamber. 
When a layer such as a-SiC:H having a wide band gap is deposited, it is 
preferable that the raw material gas be diluted with hydrogen gas 2 to 100 
times and a relatively large RF power be introduced. The preferred RF 
frequency is 1 MHz to 100 MHz, more preferably 13.56 MHz. 
When the i-type layer according to the present invention is deposited by 
the .mu.W plasma CVD method, it is preferable to introduce microwaves into 
the deposition chamber through a wave-guide pipe via a dielectric window 
(made of alumina ceramics or the like). 
When the i-type layer according to the present invention is deposited by 
the .mu.W plasma CVD method, it is preferable that the temperature of the 
substrate in the deposition chamber be 100.degree. to 400.degree. C., the 
internal pressure be 0.5 to 30 mTorr, the .mu.W power be 0.01 to 1 
W/cm.sup.3, and the .mu.W frequency be 0.5 to 10 GHz. 
Furthermore, the compound which can be gasified may be arbitrarily diluted 
with H.sub.2, He, Ne, Ar, Xe, Kr gas, or the like before it is introduced 
into the deposition chamber. 
When a layer such as a-SiC:H having a wide band gap is deposited, it is 
preferable that the raw material gas be diluted with hydrogen gas 2 to 100 
times and a relatively large RF power be introduced. 
Conductive Substrate 
The conductive substrate may be made of conductive material, or a 
supporting member may be formed of an insulating material or a conductive 
material and processed to have conductivity. The material for the 
conductive supporting member is exemplified by metal such as NiCr, 
stainless steel, Al, Cr, Mo, Au, Nb, Ta, V, Ti, Pt, Pb, Sn, or the like, 
and their alloys. 
The electrically insulating supporting member may be made of a synthetic 
resin film or a sheet, the material of which is exemplified by polyester, 
polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl 
chloride, polyvinylidene, polystyrene, polyamide and the like, glass, 
ceramics, paper, and the like. It is preferable that the electrically 
insulating supporting member be manufactured in such a manner that the 
surface of at least one side is subjected to a process for providing 
conductivity and the photovoltaic layer is formed on the surface of the 
aforementioned side. 
In the case where glass is employed, a thin film made of NiCr, Al, Cr, Mo, 
Ir, Nb, Ta, V, Ti, Pt, Pb, In.sub.2 O.sub.3, ITO (In.sub.2 O.sub.3 +Sn), 
or the like is formed on the surface of the glass so as to provide 
conductivity. In the case where a synthetic resin film made of polyester 
film or the like is employed, a metal thin film made of NiCr, Al, Ag, Pb, 
Zn, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, Tl, Pt, or the like is formed on the 
surface of the synthetic resin film by vacuum evaporation, electron beam 
evaporation, sputtering, or the like. As an alternative to this, the 
aforementioned surface is laminated with the aforementioned metal before 
it has conductivity. The supporting member may be formed into a sheet 
having a flat and smooth surface or a wavy surface. Although its thickness 
is determined so as to form a desired photovoltaic device, it may be 
thinned as long as the function of the supporting member can be exhibited 
in a case where the photovoltaic device requires flexibility. However, the 
thickness usually must be 10 .mu.m or more so as to be easily manufactured 
and handled and to have satisfactory mechanical strength. 
Example 1 
A photovoltaic device according to the present invention was manufactured 
by a DC magnetron sputtering method and a microwave (hereinafter 
abbreviated to ".mu.W") glow discharge decomposition method. 
First, a transparent electrode, which contains carbon atoms, was formed on 
a substrate by the DC magnetron sputtering apparatus 300 shown in FIG. 3. 
Referring to FIG. 3, reference numeral 302 represents the substrate made 
barium borosilicate glass ("7059" manufactured by Corning K.K.) formed 
into a 50 mm .times.50 mm square and having a thickness of 1 mm. 
In FIG. 3, reference numeral 304 represents a target composed of indium 
(In), tin (Sn) and carbon (C) contained in a molar ratio of 85:15:0.005, 
the target 304 being insulated from the deposition chamber 301 by an 
insulating supporting member 305. 
Referring to FIG. 3, reference numeral 308 represents a target composed of 
indium (In) and tin (Sn) contained in a molar ratio of 85:15, the target 
308 being insulated from the deposition chamber 301 by an insulating 
supporting member 309. 
Referring to FIG. 3, reference numerals 314 and 315 represent gas 
introduction valves, each of which is connected to an oxygen (O.sub.2) and 
an argon (Ar) gas cylinder (not shown). 
First, the substrate 302 was heated to 350.degree. C. by a heater 303 and 
the inside of the deposition chamber 301 was exhausted by a vacuum pump 
(not shown) until a vacuum gauge 312 indicated a pressure of about 
1.times.10.sup.-5 Torr. At this time, the gas introduction valves 314 and 
315 were gradually opened to introduce the O.sub.2 gas and the Ar gas into 
the deposition chamber 301. In order to set the flow rate of the O.sub.2 
gas at 20 sccm and the Ar gas at 20 sccm at this time, corresponding 
mass-flow controllers 317 and 318 were used to control them. Furthermore, 
the opening of a (butterfly type) conductance valve 313 was adjusted while 
observing the vacuum gauge 312 so as to set the pressure in the deposition 
chamber 301 at 2 mTorr. Then, the voltage of a DC power source 306 was set 
at -400 V and DC power was supplied to the target 304, while the voltage 
of a DC power source 310 was set at -450 V and the DC power was supplied 
to the target 308, causing DC glow discharge to take place. Then, shutters 
307 and 311 were opened so that the process of manufacturing the 
transparent electrode on the substrate was commenced. Simultaneously, the 
voltage of the DC power source 310 was gradually changed from -450 V to 
-350 V at a predetermined rate until a transparent electrode of 70 nm 
thickness was formed. At this time, the shutters 307 and 311 were closed, 
and the outputs from the DC power sources 306 and 310 were turned off so 
that the DC glow discharge was terminated. Then, the gas introduction 
valve 315 was closed to stop the introduction of the Ar gas into the 
deposition chamber 301. Furthermore, the opening of the conductance valve 
313 was adjusted to make the internal pressure of the deposition chamber 1 
Torr, and the transparent electrode was subjected to a heat treatment for 
one hour, whereby a transparent electrode containing carbon atoms was 
manufactured. 
Then, a manufacturing apparatus 400, composed of a raw material gas supply 
section 1020 and a deposition section 1000, as shown in FIG. 4 and adapted 
for performing the .mu.W glow discharge decomposition method, was used to 
form a non-single-crystal silicon semiconductor layer on the transparent 
electrode. 
Referring to FIG. 4, gas cylinders 1071 to 1076 are filled with raw 
material gases for manufacturing the non-single-crystal silicon 
semiconductor layers according to the present invention. 
Reference numeral 1071 represents a SiH.sub.4 (purity was 99.999%) gas 
cylinder, 1072 represents a H.sub.2 (purity was 99.9999%) gas cylinder, 
1073 represents a cylinder for B.sub.2 H.sub.6 gas (purity was 99.99% and 
hereinafter abbreviated to "B.sub.2 H.sub.6 /H.sub.2 ") diluted with 
H.sub.2 gas to 10%, 1074 represents a cylinder for PH.sub.3 gas (purity 
was 99.99% and hereinafter abbreviated to "PH.sub.3 /H.sub.2 ") diluted 
with H.sub.2 gas to 10%, 1075 represents a CH.sub.4 (purity was 99.9999%) 
gas cylinder, and 1076 represents a GeH.sub.4 (purity was 99.99%) gas 
cylinder. When the cylinders 1071 to 1076 were installed, the 
aforementioned gases were introduced into the gas pipes via valves 1051 to 
1056 to gas introduction valves 1031 and 1036. 
Reference numeral 1004 represents a substrate on which the transparent 
electrode was formed by the aforementioned method. 
First, the SiH.sub.4 gas was introduced from the gas cylinder 1071, the 
H.sub.2 gas was introduced from the gas cylinder 1072, the B.sub.2 H.sub.6 
/H.sub.2 gas was introduced from the gas cylinder 1073, the PH.sub.3 
/H.sub.2 gas was introduced from the gas cylinder 1074, the CH.sub.4 gas 
was introduced from the gas cylinder 1075, and the GeH.sub.4 gas was 
introduced from the gas cylinder 1076 by opening valves 1051 to 1056, and 
the pressure of each gas was set to about 2 kg/cm.sup.2 by pressure 
adjusters 1061 to 1066. 
Then, closures of introduction valves 1031 to 1036 and a leak valve 1009 of 
a deposition chamber 1001 were confirmed, as well as opening of discharge 
valves 1041 to 1046 and an auxiliary valve 1008 and then a (butterfly 
type) conductance valve 1007 was fully opened and the deposition chamber 
1001 and the gas pipe were exhausted by a vacuum pump (not shown) until a 
vacuum gauge 1006 indicated a pressure of about 1.times.10.sup.-4 Torr. At 
this time, the auxiliary valve 1008 and the discharge valves 1041 to 1046 
were closed. 
Then, the introduction valves 1031 to 1036 were gradually opened so that 
the aforementioned gases were introduced into corresponding mass-flow 
controllers 1021 to 1026. 
After preparations for forming the layers were completed, the p-, the i-, 
and the n-type layers were formed on the substrate 1004. 
The p-type layer was formed in such a manner that the substrate 1004 was 
heated by a heater 1005 to 350.degree. C., and the discharge valves 1041 
to 1043 were gradually opened so that the SiH.sub.4 gas, the H.sub.2 gas 
and the B.sub.2 H.sub.6 /H.sub.2 gas were introduced into the deposition 
chamber 1001 via a gas introduction pipe 1003. At this time, the 
corresponding mass-flow controllers 1021 to 1023 were used to set the flow 
rate of the SiH.sub.4 gas at 10 sccm, the H.sub.2 gas at 100 sccm, and the 
B.sub.2 H.sub.6 /H.sub.2 gas at 5 sccm. In order to set the internal 
pressure of the deposition chamber 1001 at 20 mTorr, the opening of the 
conductance valve 1007 was adjusted while observing the vacuum gauge 1006. 
Then, the output power of a .mu.W power source (not shown) was set at 400 
mW/cm.sup.3 and it was supplied to the inside of the deposition chamber 
1001 via a wave-guide pipe (not shown), a wave-guide portion 1010 and a 
dielectric window 1002. As a result, .mu.W glow discharge was initiated, 
and the process of forming the p-type layer on the transparent electrode 
was conducted until a p-type layer which was 5 nm thick was formed. At 
this time, the .mu.W glow discharge was stopped, and the discharge valves 
1041 to 1043 and the auxiliary valve 1008 were closed to stop the 
introduction of the gases into the deposition chamber 1001. Thus, the 
process of forming the p-type layer was completed. 
Then, the i-type layer was formed in such a manner that the substrate 1004 
was heated to 350.degree. C. by the heater 1005, and the discharge valves 
1041 and 1042 and the auxiliary valve 1008 were gradually opened so that 
the SiH.sub.4 gas and the H.sub.2 gas were introduced into the deposition 
chamber 1001 via the gas introduction pipe 1003. At this time, the 
corresponding mass-flow controllers 1021 and 1022 were used to set the 
flow rate of the SiH.sub.4 gas at 100 sccm and the H.sub.2 gas at 200 
sccm. In order to set the internal pressure of the deposition chamber 1001 
at 5 mTorr, the opening of the conductance valve 1007 was adjusted while 
observing the vacuum gauge 1006. Then, a high frequency bias of 100 
mW/cm.sup.3 and a DC bias of 75 V with respect to the substrate 1004 were 
supplied from power source 1011 to a bias rod 1012. Then, the power output 
of the .mu.W power source (not shown) was set to 100 mW/cm.sup.3 and it 
was supplied to the inside of the deposition chamber 1001 via the 
wave-guide pipe (not shown), the wave-guide portion 1010, and the 
dielectric window 1002. As a result, .mu.W glow discharge was caused to 
take place, and the process of forming the i-type layer on the p-type 
layer was conducted until an i-type layer which was 400 nm thick was 
formed. At this time, the .mu.W glow discharge was stopped, and the output 
of the bias power source was stopped. Thus, the process of forming the 
i-type layer was completed. 
The n-type layer was formed in such a manner that the substrate 1004 was 
heated to 300.degree. C. by the heater 1005, and the discharge valves 
1041, 1042, and 1044 were gradually opened so that the SiH.sub.4 gas, the 
H.sub.2 gas and the PH.sub.3 /H.sub.2 gas were introduced into the 
deposition chamber 1001 via the gas introduction pipe 1003. 
At this time, the corresponding mass-flow controllers 1021, 1022, and 1024 
were used to set the flow rate of the SiH.sub.4 gas at 30 sccm, the 
H.sub.2 gas at 100 sccm and the PH.sub.3 /H.sub.2 gas at 6 sccm. In order 
to set the internal pressure of the deposition chamber 1001 at 10 mTorr, 
the opening of the conductance valve 1007 was adjusted while observing the 
vacuum gauge 1006. Then, the output power of the .mu.W power source (not 
shown) was set at 50 mW/cm.sup.3 so as to be supplied to the inside of the 
deposition chamber 1001 via the wave-guide pipe (not shown), the 
wave-guide portion 1010, and the dielectric window 1002. As a result, 
.mu.W glow discharge was initiated and the process of forming the n-type 
layer on the i-type layer was conducted until a n-type layer which was 10 
nm thick was formed. At this time, the .mu.W glow discharge was stopped, 
and the discharge valves 1041, 1042, 1044 and the auxiliary valve 1008 
were closed to stop the introduction of the gases into the deposition 
chamber 1001. Thus, the process of forming the n-type layer was completed. 
When each of the aforementioned layers is formed, the discharge valves 1041 
to 1046 must, of course, be closed completely except for the valves for 
the required gases. Furthermore, undesirable retention of the gases in the 
deposition chamber 1001 and the pipes arranged from the discharge valves 
1041 to 1046 to the deposition chamber 1001 is prevented by closing the 
discharge valves 1041 to 1046, by opening the auxiliary valve 1008, and by 
fully opening the conductance valve 1007 so as to temporarily exhaust the 
inside portion of the system to a high degree of vacuum if necessary. 
Then, Al was vacuum-evaporated on the n-type layer to a thickness of 2 
.mu.m to serve as a backside electrode, whereby the photovoltaic device 
was manufactured (device No. Example 1). 
The aforementioned conditions for manufacturing the photovoltaic device are 
shown in Tables 1-1 and 1-2. 
TABLE 1-1 
______________________________________ 
Barium borosilicate glass 
Substrate 
50 mm .times. 50 mm thickness 1 mm 
______________________________________ 
Transparent 
Conditions for manufacturing by DC magnetron 
Electrode 
sputtering 
Flow rate of O.sub.2 gas 
20 sccm 
Flow rate of Ar gas 
20 sccm 
Temperature of substrate 
350.degree. C. 
Internal pressure 
2 mTorr 
Thickness of layer 
70 nm 
Composition of target 
(molar ratio) DV voltage 
In 85 -400 V 
Sn 15 
C 0.005 
In 85 -450 V .fwdarw. -350 V 
Sn 15 (changed at a 
predetermined rate 
______________________________________ 
TABLE 1-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
10 400 20 350 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
5 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
n-type 
SiH.sub.4 
30 50 10 300 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
6 
(diluted to 10%) 
Backside 
Al 2 .mu.m 
Electrode 
__________________________________________________________________________ 
Comparative Example 1 
A conventional photovoltaic device was manufactured by a method similar to 
that according to Example 1. 
First, a transparent electrode was formed on a substrate by the 
manufacturing apparatus 300 as shown in FIG. 3 and adapted to perform the 
DC magnetron sputtering method. 
Similarly to Example 1, the substrate was heated to 350.degree. C., and the 
O.sub.2 gas and the argon gas were each introduced into the deposition 
chamber 301 at 20 sccm. Then, the internal pressure of the deposition 
chamber 301 was set at 2 mTorr. Then, the voltage of the DC power source 
310 was set at -400 V and the DC power was supplied to the target 308 so 
that DC glow discharge was generated. Then, the shutter 311 was opened so 
that the process of manufacturing the transparent electrode on the 
substrate 302 was commenced. A transparent electrode having a thickness of 
70 nm was deposited, the shutter 311 was closed and the DC power source 
310 was turned off to stop the DC glow discharge. Then, the gas 
introduction valve 315 was closed to stop the introduction of the Ar gas 
into the deposition chamber 301, and the opening of the conductance valve 
313 was adjusted to set the internal pressure of the deposition chamber 
301 at 1 Torr. Then, the transparent electrode was subjected to a heat 
treatment for one hour, and thus the transparent electrode was 
manufactured. 
Then, the p-, i-, and n-type layers and the backside electrode were formed 
on the transparent electrode under the same conditions as those according 
to Example 1, whereby a photovoltaic device was manufactured (device No. 
Comparative Example 1). 
The initial characteristics and the durability of the photovoltaic devices 
according to Example 1 (device No. Example 1) and Comparative Example 1 
(device No. Comparative Example 1) were measured. 
The initial characteristics were measured in such a manner that 
short-circuit currents and series resistances were measured by measuring 
the V-I characteristics while irradiating the photovoltaic devices 
according to Example 1 (device No. Example 1) and Comparative Example 1 
(device No. Comparative Example 1) with AM-1.5 light (100 mW/cm.sup.2). As 
a result, the photovoltaic device according to Example 1 (device No. 
Example 1) exhibited an excellent short-circuit current 1.04 times that of 
the photovoltaic device according to Comparative Example 1 (device No. 
Comparative Example 1) and an excellent series resistance 1.37 times the 
same. 
The durability was measured in such a manner that the changes in the 
photoelectric conversion efficiencies were evaluated after performing the 
following process: the photovoltaic devices according to Example 1 (device 
No. Example 1) and Comparative Example 1 (device No. Comparative Example 
1) were allowed to stand in the dark in an atmosphere the humidity of 
which was 85% and subjected 30 times to heat cycles each consisting of 
standing at a temperature of 85.degree. C. for four hours and at a 
temperature of -40.degree. C. for 30 minutes. As a result, the 
photovoltaic device according to Example 1 (device No. Example 1) 
exhibited an excellent photoelectric conversion efficiency 1.09 times that 
of the photovoltaic device according to Comparative Example 1 (device No. 
Comparative Example 1). 
Furthermore, the distribution of the carbon atoms in the transparent 
electrode according to Example 1 (device No. Example 1) was analyzed by 
using a secondary ionization mass analyzer ("IMS-3F" manufactured by 
CAMECA), which indicated that the quantity of carbon atoms was 
considerably reduced from the portion adjacent to the p-type layer toward 
the substrate. 
As a result, it was confirmed that the photovoltaic device (device No. 
Example 1) according to the present invention which used the transparent 
electrode containing carbon atoms has excellent characteristics in 
comparison with the conventional photovoltaic device (device No. 
Comparative Example 1) and therefore the beneficial effect of the present 
invention was confirmed. 
Example 2 
The transparent electrode, the p-, i-, and n-type layers and the backside 
electrode were formed under conditions similar to those for manufacturing 
the photovoltaic device according to Example 1 except that the alloys 
shown in Table 2 were used as the material of the target 304 whereby 
several photovoltaic devices were manufactured (device No. Examples 2-1 to 
2-5). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices (device No. Examples 2-1 to 2-5), thus manufactured, 
were measured by a method similar to that according to Example 1. The 
results are shown in Table 2. 
TABLE 2 
______________________________________ 
Short- Series 
Device Composition of target 
circuit resis- 
Durability 
No. (mole ratio) current tance characteristic 
______________________________________ 
Example 
In:Sn:C = 85:15:0.01 
1.05 1.31 1.07 
2-1 
Example 
In:C = 100:0.001 
1.05 1.30 1.07 
2-2 
Example 
Sn:C = 100:0.005 
1.05 1.29 1.06 
2-3 
Example 
In:Sn:C = 80:20:0.007 
1.06 1.37 1.06 
2-4 
Example 
In:Sn:C = 90:10:0.003 
1.05 1.33 1.07 
2-5 
______________________________________ 
*results of measurements were relative values with respect to Comparative 
Example 1 (device No. Comparative Example 1) 
Thus, it was confirmed that the photovoltaic devices (device No. Examples 
2-1 to 2-5) using the transparent electrode containing carbon atoms 
according to the present invention have excellent characteristics in 
comparison with the conventional photovoltaic device (device No. 
Comparative Example 1) and therefore an advantageous effect of the present 
invention was confirmed. 
Example 3 
The transparent electrode, the p-, i-, and n-type layers and the backside 
electrode were formed under conditions similar to those for manufacturing 
the photovoltaic device according to Example 1. Specific conditions for 
the formation of the n-, i-, and p-type layers are shown in Table 3, 
whereby another photovoltaic device was manufactured (device No. Example 
3). 
TABLE 3 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
n-type 
SiH.sub.4 
10 350 15 350 Excluded 
5 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
8 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
p-type 
SiH.sub.4 
30 50 10 300 Excluded 
15 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
3 
(diluted to 10%) 
__________________________________________________________________________ 
Comparative Example 2 
The transparent electrode, the n-, i-, and p-type layers and the backside 
electrode were formed under conditions similar to those for manufacturing 
the photovoltaic device according to Example 1 except the transparent 
electrode was formed on the substrate under the same manufacturing 
conditions according to Comparative Example 1, whereby another comparative 
photovoltaic device was manufactured (device No. Comparative Example 2). 
The initial characteristics and the durability characteristics of the 
photovoltaic device according to Example 3 (device No. Example 3) and 
Comparative Example 2 (device No. Comparative Example 2) were measured by 
a method similar to that according to Example 1. As a result, the 
photovoltaic device according to Example 3 (device No. Example 3) 
exhibited a 1.05 times greater short-circuit current, an excellent series 
resistance 1.32 times greater, and an excellent durability characteristic 
1.09 times that of the photovoltaic device according to Comparative 
Example 2 (device No. Comparative Example 2). Therefore, it was confirmed 
that the photovoltaic device (device No. Example 3) using the transparent 
electrode containing carbon atoms according to the present invention has 
excellent characteristics in comparison with those of the conventional 
photovoltaic device (device No. Comparative Example 2), and therefore a 
beneficial effect of the present invention was confirmed. 
Example 4 
The transparent electrode containing carbon atoms was formed on the 
substrate under the manufacturing conditions according to Example 1, and 
p-, i-, n-, p-, i-, and n-type layers were sequentially formed on the 
aforementioned transparent electrode by using CH.sub.4 gas and GeH.sub.4 
gas under the manufacturing conditions shown in Tables 4-1 and 4-2. Then, 
a ZnO thin film of 1 .mu.m thickness was evaporated on the n-type layer by 
the DC magnetron sputtering method to serve as a reflection enhancing 
layer. Furthermore, a silver thin film of 300 nm thickness was deposited 
thereon by the DC magnetron sputtering method to serve as a light 
reflective layer, and then the backside electrode was formed on the silver 
thin film, whereby yet another photovoltaic device was manufactured 
(device No. Example 4). 
TABLE 4-1 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
10 500 20 350 RF 5 
layer 
CH.sub.4 
2 60 mW/cm.sup.3 
H.sub.2 
400 DC 90 V 
B.sub.2 H.sub.6 /H.sub.2 
10 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 50 3 350 RF 200 
layer 
H.sub.2 
200 120 mW/cm.sup.3 
DC 80 V 
n-type 
SiH.sub.4 
15 50 15 300 Excluded 
5 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
TABLE 4-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
15 50 15 300 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
3 
(diluted to 10%) 
i-type 
SiH.sub.4 
70 150 5 300 RF 150 
layer 
GeH.sub.4 
30 25 mW/cm.sup.3 
H.sub.2 
200 DC 100 V 
n-type 
SiH.sub.4 
15 50 10 300 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
Comparative Example 3 
The transparent electrode, the p-, i-, n-, p-, i-, and n-type layers, a 
reflection enhancing layer, a light reflective layer, and a backside 
electrode were formed on the substrate under the same manufacturing 
conditions as those according to Example 4 except for an arrangement in 
which the transparent electrode was formed on the substrate under the same 
conditions as those according to Comparative Example 1, so that a 
photovoltaic device was manufactured (device No. Comparative Example 3). 
The initial characteristics and the durability characteristics of the 
photovoltaic device (device No. Example 4) according to Example 4 and 
those according to Comparative Example 3 (device No. Comparative Example 
3) were measured by methods similar to those according to Example 1. As a 
result, the photovoltaic device according to Example 4 (device No. Example 
4) exhibited a 1.07 times larger short-circuit current, an excellent 
series resistance 1.40 times greater, and an excellent durability 
characteristic 1.09 times that of the photovoltaic device according to 
Comparative Example 3 (device No. Comparative Example 3). Therefore, it 
was confirmed that the photovoltaic device (device No. Example 4) using 
the transparent electrode containing carbon atoms according to the present 
invention has excellent characteristics in comparison with those of the 
conventional photovoltaic device (device No. Comparative Example 3), and 
therefore a desirable effect of the present invention was confirmed. 
Example 5 
A photovoltaic device according to the present invention was manufactured 
by the vacuum evaporation method and the glow discharge decomposition 
method using microwaves (hereinafter abbreviated to ".mu.W"). 
First, a transparent electrode, which contained carbon atoms, was formed on 
a substrate by using the manufacturing apparatus 500 shown in FIG. 5 and 
adapted to perform the vacuum evaporation method. Referring to FIG. 5, 
reference numeral 502 represents a 50 mm .times.50 mm square substrate 
which was 1 mm thick and made of barium borosilicate ("7059" manufactured 
by Corning K.K.). 
Referring to FIG. 5, reference numeral 504 represents an evaporation source 
composed of indium (In) and tin (Sn) contained in a molar ratio of 1:1. 
Reference numeral 510 represents a gas introduction valve which is 
connected to a CO.sub.2 gas (CO.sub.2 /O.sub.2) cylinder (not shown) 
diluted with O.sub.2 gas to 50 ppm. Reference numeral 512 represents a gas 
introduction valve connected to an O.sub.2 gas cylinder (not shown). 
First, the substrate 502 was heated to 350.degree. C. by a heater 503 and 
the inside of the deposition chamber 501 was exhausted by a vacuum pump 
(not shown) until a vacuum gauge 508 indicated a pressure of about 
1.times.10.sup.-5 Torr. At this time, the gas introduction valves 510 and 
512 were gradually opened to introduce the CO.sub.2 /O.sub.2 gas and the 
O.sub.2 gas into the deposition chamber 501. In order to set the flow rate 
of the CO.sub.2 /O.sub.2 gas at 3 sccm and the O.sub.2 gas at 7 sccm at 
this time, corresponding mass-flow controllers 511 and 513 were used to 
control them. Furthermore, the opening of a (butterfly type) conductance 
valve 509 was adjusted while observing the vacuum gauge 508 to set the 
pressure in the deposition chamber 501 at 0.3 mTorr. Then, electric power 
was supplied from an AC power source 506 to a heater 505 to heat the 
evaporation source 504. Then, a shutter 507 was opened so the process of 
manufacturing the transparent electrode on the substrate was commenced. 
Simultaneously, the corresponding mass-flow controllers 511 and 513 were 
used to change the flow rate of the CO.sub.2 /O.sub.2 gas from 3 sccm to 7 
sccm and the O.sub.2 gas from 7 sccm to 3 sccm at a predetermined rate. 
When a transparent electrode which was 70 nm thick was formed, the shutter 
507 was closed and the output from the AC power source 506 was turned off. 
Furthermore, the gas introduction valves 510 and 512 were closed to stop 
the gas introduction into the deposition chamber 501. Thus, the process of 
manufacturing the transparent electrode containing carbon atoms was 
completed. 
Then, the p-, i-, and n-type layers and the backside electrode were formed 
on the transparent electrode under the same manufacturing conditions as 
those according to Example 1, so that a photovoltaic device was 
manufactured (device No. Example 5). 
Comparative Example 4 
A conventional photovoltaic device was manufactured by a method similar to 
that according to Example 5. 
First, a transparent electrode was formed on the substrate by use of the 
manufacturing apparatus 500 shown in FIG. 5 and adapted to perform the 
vacuum evaporation method. 
Similarly to Example 5, the substrate 502 was heated to 350.degree. C. by 
the heater 503, and the gas introduction valve 512 was gradually opened to 
introduce the O.sub.2 gas into the deposition chamber 501 at a flow rate 
of 7 sccm. Then, the internal pressure of the deposition chamber 501 was 
adjusted to 0.3 mTorr. Then, electric power was supplied from the AC power 
source 506 to the heater 505 to heat the deposition source 504. Then, the 
shutter 507 was opened so that the process of manufacturing the 
transparent electrode on the substrate 502 was commenced. When a 
transparent electrode which was 70 nm thick was obtained, the shutter 507 
was closed, the output from the AC power source 506 was turned off, and 
the gas introduction valve 512 was closed so as to stop the introduction 
of the gas into the deposition chamber 501. Thus, the process of 
manufacturing the transparent electrode was completed. Furthermore, the 
p-, i-, and n-type layers and the backside electrode were formed on the 
transparent electrode under the same manufacturing conditions as those 
according to Example 1, whereby a photovoltaic device was manufactured. 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 5 (device No. Example 5) and 
Comparative Example 4 (device No. Comparative Example 4) were measured by 
a method similar to that according to Example 1. As a result, the 
photovoltaic device according to Example 5 (device No. Example 5) 
exhibited a 1.05 times larger short-circuit current, an excellent series 
resistance 1.40 times larger, and excellent durability characteristics 
1.08 times those of the photovoltaic device according to Comparative 
Example 4 (device No. Comparative Example 4). Therefore, it was confirmed 
that the photovoltaic device (device No. Example 5) using the transparent 
electrode containing carbon atoms according to the present invention has 
excellent characteristics in comparison with those of the conventional 
photovoltaic device (device No. Comparative Example 4), and therefore a 
beneficial effect of the present invention was confirmed. 
Furthermore, the distribution of the carbon atoms in the transparent 
electrode according to Example 5 (device No. Example 5) was analyzed by 
using a secondary ionization mass analyzer ("IMS-3F" manufactured by 
CAMECA), which indicated the quantity of carbon atoms was apparently 
reduced from the portion adjacent to the p-type layer toward the 
substrate. 
Example 6 
A 50 mm .times.50 mm square conductive substrate which was 1 mm thick, made 
of stainless steel (SUS430BA), and having mirror surfaces was used. A 
silver thin film serving as a light reflective layer and having a 
thickness of 300 nm and a ZnO thin film serving as a reflection enhancing 
layer and having a thickness of 1 .mu.m were deposited by the DC magnetron 
sputtering method. Then, the n-, i-, and p-type layers were formed on the 
conductive substrate under the manufacturing conditions shown in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
n-type 
SiH.sub.4 
30 50 10 350 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
10 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
p-type 
SiH.sub.4 
15 400 20 300 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
Then, the transparent electrode was formed on the p-type layer by a similar 
method to that according to Example 5. The temperature of the substrate 
was set at 200.degree. C., the flow rate of the CO.sub.2 /O.sub.2 gas was 
set at 7 sccm, the flow rate of the O.sub.2 gas was set at 3 sccm and the 
internal pressure of the deposition chamber 501 was set at 0.3 mTorr. 
Then, electric power was supplied from the AC power source 506 to the 
heater 505 to heat the evaporation source 504, and the shutter 507 was 
opened so that the process of manufacturing the transparent electrode on 
the substrate 502 was commenced. Simultaneously, the corresponding mass 
flow controllers 511 and 513 were used to change the flow rate of the 
CO.sub.2 /O.sub.2 gas from 7 sccm to 3 sccm and to change that of the 
O.sub.2 gas from 3 sccm to 7 sccm at a predetermined rate. When a 
transparent electrode which was 70 nm thick was manufactured, the shutter 
507 was closed, the output from the AC power source 506 was turned off, 
and the gas introduction valves 510 and 512 were closed to stop the 
introduction of the gases into the deposition chamber 501. Thus, the 
transparent electrode containing carbon atoms was formed on the p-type 
layer. Furthermore, Al was evaporated on the transparent electrode to a 
thickness of 2 .mu.m to serve as a collecting electrode by vacuum 
evaporation, whereby a photovoltaic device was manufactured (device No. 
Example 6). 
Comparative Example 5 
A transparent electrode was formed on the p-type layer under the same 
conditions as those according to Comparative Example 4 except for the 
light reflective layer, the reflection enhancing layer, the n-, i-, and 
p-type layers being formed on the conductive substrate under the same 
conditions as those according to Example 6 and the temperature of the 
substrate being 200.degree. C. Furthermore, a collecting electrode was 
formed similarly to Example 6, whereby another photovoltaic device was 
manufactured (device No. Comparative Example 5). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 6 (device No. Example 6) and 
Comparative Example 5 (device No. Comparative Example 5) were measured by 
a method similar to that according to Example 1. As a result, the 
photovoltaic device according to Example 6 (device No. Example 6) 
exhibited a 1.06 times larger short-circuit current, an excellent series 
resistance 1.41 times greater, and excellent durability characteristics 
1.08 times those of the photovoltaic device according to Comparative 
Example 5 (device No. Comparative Example 5). Therefore, it was confirmed 
that the photovoltaic device (device No. Example 6) using the transparent 
electrode containing carbon atoms according to the present invention has 
excellent characteristics in comparison with those of the conventional 
photovoltaic device (device No. Comparative Example 5), and therefore a 
beneficial effect of the present invention was confirmed. 
Furthermore, the distribution of the carbon atoms in the transparent 
electrode according to Example 6 (device No. Example 6) was analyzed by 
using a secondary ionization mass analyzer ("IMS-3F" manufactured by 
CAMECA), which indicated the quantity of carbon atoms was apparently 
reduced from the portion adjacent to the p-type layer toward the 
substrate. 
Example 7 
A photovoltaic device according to the present invention was manufactured 
by the DC magnetron sputtering method and the radio frequency (hereinafter 
abbreviated to "RF") glow discharge and decomposition method. 
First, the transparent electrode containing carbon atoms was formed on the 
substrate under the same forming conditions as those according to Example 
1. 
Then, a manufacturing apparatus 600, composed of a raw material gas supply 
device section 1020 and a deposition device section 1100, as shown in FIG. 
6 and adapted to perform the RF glow discharge and decomposition method, 
was used to form a non-single-crystal silicon semiconductor layer on the 
transparent electrode. 
Referring to FIG. 6, reference numeral 1104 represents a substrate on which 
the aforementioned transparent electrode was formed. 
Gas cylinders 1071 to 1076 were filled with raw material gases which were 
the same as those according to Example 1, and the gases were introduced 
into the mass-flow controllers 1021 to 1026 in a similar manner to that 
according to Example 1. 
After preparations for forming the layers had been completed as described 
above, the p-, i, and n-type layers were formed on the substrate 1104. 
The p-type layer was formed in such a manner that the substrate 1104 was 
heated to 300.degree. C. by the heater 1105, and the discharge valves 1041 
to 1043 and the auxiliary valve 1008 were gradually opened to introduce 
the SiH.sub.4 gas, the H.sub.2 gas, and the B.sub.2 H.sub.6 /H.sub.2 gas 
into the deposition chamber 1101 via introduction pipe 1103. The 
corresponding mass flow controllers 1021 to 1023 were actuated to set the 
flow rate of the SiH.sub.4 gas at 2 sccm, the H.sub.2 gas at 50 sccm and 
the B.sub.2 H.sub.6 /H.sub.2 gas at 1 sccm. The internal pressure of the 
deposition chamber 1101 was set to 1 Torr by adjusting the opening of the 
conductance valve 1107 while observing the vacuum gauge 1106. Then, the 
power output of the RF power source (not shown) was set to 200 mW/cm.sup.3 
and the RF power was supplied to a cathode 1102 via an RF matching box 
1112 so that RF glow discharge was generated and the process of 
manufacturing the p-type layer on the transparent electrode was commenced. 
When a p-type layer which was 5 nm thick was formed, the RF glow discharge 
was stopped, and the discharge valves 1041 to 1043 and the auxiliary valve 
1108 were closed to stop the gas introduction into the deposition chamber 
1101. Thus, the process of forming the p-type layer was completed. 
Then, the i-type layer was formed in such a manner that the substrate 1104 
was heated to 300.degree. C. by the heater 1105. Then, the discharge 
valves 1041 and 1042 and the auxiliary valve 1108 were gradually opened to 
introduce the SiH.sub.4 gas and the H.sub.2 gas into the deposition 
chamber 1101 via the gas introduction pipe 1103. In order to set the flow 
rate of the SiH.sub.4 gas at 2 sccm and the H.sub.2 gas at 20 sccm at this 
time, the corresponding mass-flow controllers 1021 and 1022 were used to 
adjust them. The internal pressure of the deposition chamber 1101 was set 
at 1 Torr by adjusting the opening of the conductance valve 1107 while 
observing the vacuum gauge 1106. Then, the power output of the RF power 
source (not shown) was set to 5 mW/cm.sup.2 and the RF power was supplied 
to the cathode 1102 via the RF matching box 1112 to generate the RF glow 
discharge and to commence the process of forming the i-type layer on the 
p-type layer. When an i-type layer which was 400 nm thick was formed, the 
RF glow discharge was stopped and the process of forming the i-type layer 
was completed. 
The n-type layer was formed in such a manner that the substrate 1104 was 
heated to 250.degree. C. by the heater 1105 and the discharge valve 1044 
was gradually opened to introduce the SiH.sub.4 gas, the H.sub.2 gas, and 
the PH.sub.3 /H.sub.2 gas into the deposition chamber 1101 via the gas 
introduction pipe 1103. In order to set the gas flow rate of the SiH.sub.4 
gas at 2 sccm, the H.sub.2 gas at 20 sccm and the PH.sub.3 /H.sub.2 gas at 
1 sccm at this time, the corresponding mass-flow controllers 1021, 1022, 
and 1024 were adjusted. The internal pressure of the deposition chamber 
1101 was set at 1 Torr by adjusting the opening of the conductance valve 
1107 while observing the vacuum meter 1106. Then, the power output of the 
RF power source (not shown) was set to 5 mW/cm.sup.2 and the RF power was 
supplied to the cathode 1102 via the RF matching box 1112 to generate the 
RF glow discharge. Thus, the process of forming the n-type layer on the 
i-type later was commenced. When an n-type layer of 10 nm thickness was 
formed, the RF glow discharge was stopped and the discharge valves 1041, 
1042, and 1044 and the auxiliary valve 1108 were closed to stop the gas 
introduction into the deposition chamber 1101. Thus, the process of 
forming the n-type layer was completed. 
When each of the aforementioned layers is formed, the discharge valves 1041 
to 1046 must, of course, be closed completely except for the valves for 
the required gases. Furthermore, the undesirable retention of the gases in 
the deposition chamber 1101 and the pipes arranged from the discharge 
valves 1041 to 1046 to the deposition chamber 1101 is prevented by closing 
the discharge valves 1041 to 1046, by opening the auxiliary valve 1108 and 
by fully opening the conductance valve 1107 to temporarily exhaust the 
inside portion of the system to a high degree of vacuum if necessary. 
Then, the backside electrode was formed on the n-type layer by evaporation 
similarly to Example 1 so that the photovoltaic device was manufactured 
(device No. Example 7). 
The conditions for manufacturing the photovoltaic device are shown in 
Tables 6-1 and 6-2. 
TABLE 6-1 
______________________________________ 
Barium borosilicate glass 
Substrate 
50 mm .times. 50 mm thickness 1 mm 
______________________________________ 
Transparent 
Conditions for manufacturing by DC magnetron 
Electrode 
sputtering 
Flow rate of O.sub.2 gas 
20 sccm 
Flow rate of Ar gas 
20 sccm 
Temperature of substrate 
350.degree. C. 
Internal pressure 
2 mTorr 
Thickness of layer 
70 nm 
Composition of target 
(molar ratio) DV voltage 
In 85 -400 V 
Sn 15 
C 0.005 
In 85 -450 V .fwdarw. -350 V 
Sn 15 (changed at a 
predetermined rate 
______________________________________ 
TABLE 6-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate 
of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
(nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
2 200 1 300 5 
layer 
H.sub.2 
50 
B.sub.2 H.sub.6 /H.sub.2 
1 
(diluted to 10%) 
i-type 
SiH.sub.4 
2 5 1 300 400 
layer 
H.sub.2 
20 
n-type 
SiH.sub.4 
2 5 1 250 10 
layer 
H.sub.2 
20 
PH.sub.3 /H.sub.2 
1 
(diluted to 10%) 
Backside 
Al 2 .mu.m 
Electrode 
__________________________________________________________________________ 
Comparative Example 6 
The p-, i-, and n-type layers and the backside electrode were formed on the 
transparent electrode under the same conditions as those according to 
Example 7 except for the transparent electrode, which was the same as that 
according to Comparative Example 1, whereby the photovoltaic device was 
manufactured (device No. Comparative Example 6). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 7 (device No. Example 7) and 
Comparative Example 6 (device No. Comparative Example 6) were measured by 
a similar method to that according to Example 1. As a result, the 
photovoltaic device according to Example 7 (device No. Example 7) 
exhibited a 1.06 times larger short-circuit current, an excellent series 
resistance 1.39 times larger, and excellent durability characteristics 
1.09 times larger than those of the photovoltaic device according to 
Comparative Example 6 (device No. Comparative Example 6). Therefore, it 
was confirmed that the photovoltaic device (device No. Example 7) using 
the transparent electrode containing carbon atoms according to the present 
invention has excellent characteristics in comparison with those of the 
conventional photovoltaic device (device No. Comparative Example 6), and 
therefore a beneficial effect of the present invention was confirmed. 
Example 8 
A photovoltaic device according to the present invention was manufactured 
by the DC magnetron sputtering method and the microwave (hereinafter 
abbreviated to ".mu.W") glow discharge and decomposition method. 
First, the transparent electrode containing nitrogen atoms was formed on 
the substrate by the manufacturing apparatus 300 shown in FIG. 3 and 
adapted to perform the DC magnetron sputtering method. 
Referring to FIG. 3, reference numeral 302 represents a substrate in the 
form of a 50 mm .times.50 mm square, which was 1 mm thick and made of 
barium borosilicate glass ("7059" manufactured by Corning K.K.). 
In FIG. 3, reference numeral 304 represents a target made of indium (In) 
and tin (Sn) contained in a molar ratio of 85:15, the target 304 being 
insulated from the deposition chamber 301 by the insulating supporting 
member 305. 
Reference numerals 314 to 316 represent gas introduction valves which were 
respectively connected to an oxygen (O.sub.2) gas cylinder, an argon (Ar) 
gas cylinder, and a cylinder for nitrogen (N.sub.2) gas (hereinafter 
abbreviated to "N.sub.2 /O.sub.2 ") diluted with oxygen (O.sub.2) gas to 
50 ppm. 
First, the substrate 302 was heated to 350.degree. C. by the heater 303, 
and the deposition chamber 301 was exhausted by a vacuum pump (not shown). 
When the pressure reading of the vacuum gauge 312 indicated about 
1.times.10.sup.-5 Torr, the gas introduction valves 314 to 316 were 
gradually opened so as to introduce the O.sub.2 gas, the Ar gas, and the 
N.sub.2 /O.sub.2 gas into the deposition chamber 301. In order to set the 
flow rate of the O.sub.2 gas at 15 sccm, the Ar gas at 20 sccm and the 
N.sub.2 /O.sub.2 gas at 5 sccm at this time, the corresponding mass-flow 
controllers 317 to 319 were operated. In order to set the internal 
pressure of the deposition chamber 301 at 2 mTorr, the opening of the 
(butterfly type) conductance valve 313 was adjusted while observing the 
vacuum gauge 312. Then, the voltage of the DC power source 306 was set at 
-400 V and the DC power was supplied to the target 304 to generate a DC 
glow discharge. Then, the shutter 307 was opened so that the process for 
forming the transparent electrode on the substrate 302 was commenced. 
Simultaneously, in order to cause the flow rate of the O.sub.2 gas to be 
gradually changed from 15 sccm to 5 sccm at a predetermined rate, and to 
cause the flow rate of the N.sub.2 /O.sub.2 gas to be also gradually 
changed from 5 sccm to 15 sccm at a predetermined rate, the corresponding 
mass-flow controllers 517 and 519 were operated. When a transparent 
electrode having a thickness of 70 nm was formed, the shutter 307 was 
closed, and the output from the DC power source 306 was turned off so that 
the DC glow discharge was stopped. Then, the gas introduction valves 315 
and 316 were closed to stop the introduction of the Ar gas and the N.sub.2 
/O.sub.2 gas into the deposition chamber 301. Furthermore, the internal 
pressure of the deposition chamber 301 was set at 1 Torr by adjusting the 
opening of the conductance valve 313. Then, the transparent electrode was 
subjected to a heat treatment for one hour whereby the process of 
manufacturing the transparent electrode containing nitrogen atoms was 
completed. Then, the semiconductor layer was manufactured by a method 
similar to that according to Example 1. 
Then, Al was formed by vacuum evaporation on the n-type layer to a 
thickness of 2 .mu.m to serve as the backside electrode whereby a 
photovoltaic device was manufactured (device No. Example 8). 
The above-mentioned conditions for manufacturing the photovoltaic device 
are shown in Tables 7-1 and 7-2. 
TABLE 7-1 
__________________________________________________________________________ 
Substrate 
Barium borosilicate glass 50 mm .times. 50 mm thickness 1 
__________________________________________________________________________ 
mm 
Transparent 
Conditions for manufacturing by DC magnetron sputtering 
Electrode 
Gas and Flow Rate 
Target In:Sn = 85:15 
(sccm) Temperature of substrate 
350.degree. 
O.sub.2 15 .fwdarw. 5 
Internal pressure 
2 mTorr 
(changed at a DC voltage -400 V 
predetermined rate) 
Thickness of the layer 
70 nm 
Ar 20 
N.sub.2 /O.sub.2 
5 .fwdarw. 15 
(changed at a 
predetermined rate) 
__________________________________________________________________________ 
TABLE 7-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
10 400 20 350 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
5 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
n-type 
SiH.sub.4 
30 50 10 250 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
6 
(diluted to 10%) 
Backside 
Al 2 .mu.m 
Electrode 
__________________________________________________________________________ 
Comparative Example 7 
A conventional photovoltaic device was manufactured by a method similar to 
that according to Example 8. 
First, the transparent electrode was formed on the substrate by the 
manufacturing apparatus 300 shown in FIG. 3 and adapted to perform the DC 
magnetron sputtering method. 
Similarly to Example 8, the substrate 302 was heated to 350.degree. C., and 
the O.sub.2 gas was introduced into the deposition chamber 301 at 20 sccm 
and the argon gas was introduced at 20 sccm. Then, the internal pressure 
of the deposition chamber 301 was adjusted to 2 mTorr. Then, the voltage 
of the DC power source 310 was set to -400 V and the DC power was supplied 
to the target 304 to generate a DC glow discharge. Then, the shutter 307 
was opened so that the process for manufacturing the transparent electrode 
on the substrate 302 was commenced. When a transparent electrode which was 
70 nm thick was formed, the shutter 307 was turned off so that the DC glow 
discharge was stopped. Then, the gas introduction valve 315 was closed to 
stop the introduction of the Ar gas into the deposition chamber 301. 
Furthermore, the opening of the conductance valve 313 was adjusted to set 
the internal pressure of the deposition chamber 301 at 1 Torr. Then, the 
transparent electrode was subjected to a heat treatment for one hour, and 
thus the process for manufacturing the transparent electrode was 
completed. 
Then, the p-, i-, and n-type layers and the backside electrode were formed 
on the transparent electrode under the same conditions as those according 
to Example 8, so that a photovoltaic device was manufactured (device No. 
Comparative Example 7). 
Then, the initial characteristics and the durability of the photovoltaic 
devices according to Example 8 (device No. Example 8) and Comparative 
Example 7 (device No. Comparative Example 7) were measured. 
The initial characteristics were measured in such a manner that 
short-circuit currents and series resistances were measured by measuring 
the V-I characteristics while irradiating the photovoltaic devices 
according to Example 8 (device No. Example 8) and Comparative Example 7 
(device No. Comparative Example 7) with AM-1.5 light (10 mW/cm.sup.2). As 
a result, the photovoltaic device according to Example 8 (device No. 
Example 8) exhibited an excellent short-circuit current 1.05 times that of 
the photovoltaic device according to Comparative Example 7 (device No. 
Comparative Example 7) and an excellent series resistance 1.40 times the 
same. 
The durability was measured in such a manner that the changes in the 
photoelectric conversion efficiencies were evaluated after performing the 
following process: the photovoltaic devices according to Example 8 (device 
No. Example 8) and Comparative Example 7 (device No. Comparative Example 
7) were allowed to stand in the dark in an atmosphere the humidity of 
which was 85% and subjected to 30 heat cycles each consisting of standing 
at a temperature of 85.degree. C. for four hours and at a temperature of 
-40.degree. C. for 30 minutes. As a result, the photovoltaic device 
according to Example 8 (device No. Example 8) exhibited an excellent 
photoelectric conversion efficiency 1.10 times that of the photovoltaic 
device according to Comparative Example 7 (device No. Comparative Example 
7). 
Furthermore, the distribution of the nitrogen atoms in the transparent 
electrode of the photovoltaic device according to Example 8 (device No. 
Example 8) was analyzed by using a secondary ionization mass analyzer 
("IMS-3F" manufactured by CAMECA), resulting in the quantity of nitrogen 
atoms apparently being reduced from the portion adjacent to the p-type 
layer toward the substrate. 
As a result, it was confirmed that the photovoltaic device (device No. 
Example 8) according to the present invention which used the transparent 
electrode containing nitrogen atoms has excellent characteristics in 
comparison with the conventional photovoltaic device (device No. 
Comparative Example 7) and therefore a beneficial effect of the present 
invention was confirmed. 
Example 9 
The transparent electrode, the p-, i-, and n-type layers and the backside 
electrode were formed on the substrate under the same conditions as those 
according to Example 8 except that the alloys shown in Table 8 were used 
as the material of the target 304, whereby several photovoltaic devices 
were manufactured (device No. Examples 9-1 to 9-9). 
The initial characteristics and the durability of the manufactured 
photovoltaic devices (device No. Examples 9-1 to 9-9) were measured by 
similar methods to those according to Example 8. The results are shown in 
Table 8. 
TABLE 8 
______________________________________ 
Short- Series 
Device Composition of target 
circuit resis- 
Durability 
No. (mole ratio) current tance characteristic 
______________________________________ 
Example 
only In 1.06 1.33 1.08 
9-1 
Example 
only Sn 1.06 1.32 1.07 
9-2 
Example 
In:Sn = 4:1 1.07 1.39 1.08 
9-3 
Example 
In:Sn = 9:1 1.07 1.38 1.09 
9-4 
Example 
In:C = 100:0.001 
1.07 1.36 1.09 
9-5 
Example 
Sn:C = 100:0.005 
1.07 1.37 1.08 
9-6 
Example 
In:Sn:C = 80:20:0.007 
1.08 1.40 1.09 
9-7 
Example 
In:Sn:C = 85:15:0.01 
1.08 1.42 1.09 
9-8 
Example 
In:Sn:C = 90:10:0.003 
1.07 1.41 1.10 
9-9 
______________________________________ 
*results of measurements were relative values with respect to Comparative 
Example 7 (device No. Comparative Example 7) 
As can be understood from Table 8, it was confirmed that the photovoltaic 
devices (device No. Examples 9-1 to 9-9), containing nitrogen atoms 
according to the present invention have excellent characteristics in 
comparison with the conventional photovoltaic devices (device No. 
Comparative Example 7) and therefore a beneficial effect of the present 
invention was confirmed. 
Example 10 
The transparent electrode, the n-, i-, and p-type layers and the backside 
electrode were formed on the substrate under the same conditions as those 
according to Example 8 except the n-, i-, and p-type layers were formed 
under conditions shown in Table 9, whereby a photovoltaic device was 
manufactured (device No. Example 10). 
TABLE 9 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
n-type 
SiH.sub.4 
10 350 15 350 Excluded 
5 
layer 
H.sub.2 
100 
PH.sub.3 H.sub.2 
8 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
p-type 
SiH.sub.4 
30 50 10 300 Excluded 
15 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
3 
(diluted to 10%) 
__________________________________________________________________________ 
Comparative Example 8 
The transparent electrode, the n-, i-, and p-type layers and the backside 
electrode were formed on the substrate under the same conditions as those 
according to Example 10 except the transparent electrode was formed on the 
substrate under the same conditions as those according to Comparative 
Example 7, so that a photovoltaic device was manufactured (device No. 
Comparative Example 8). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 10 (device No. Example 10) and 
Comparative Example 8 (device No. Comparative Example 8) were measured by 
a method similar to that according to Example 8. As a result, the 
photovoltaic device according to Example 10 (device No. example 10) 
exhibited a 1.06 times larger short-circuit current, an excellent series 
resistance 1.37 times larger, and excellent durability characteristics 
1.10 times those of the photovoltaic device according to Comparative 
Example 8 (device No. Comparative Example 8). Therefore, it was confirmed 
that the photovoltaic device (device No. Example 10) using the transparent 
electrode containing nitrogen atoms according to the present invention has 
excellent characteristics in comparison with those of the conventional 
photovoltaic device (device No. Comparative Example 8), and therefore a 
beneficial effect of the present invention was confirmed. 
Example 11 
The transparent electrode containing nitrogen atoms was formed on the 
substrate under the same conditions as those according to Example 8, and 
the p-, i-, n-, p-, i-, and n-type layers were formed on the aforesaid 
transparent electrode by using the CH.sub.4 gas and the GeH.sub.4 gas 
under the conditions shown in Tables 10-1 and 10-2. Then, a ZnO thin film 
was formed by evaporation on the n-type layer to serve as a reflection 
enhancing layer by the DC magnetron sputtering method to a thickness of 1 
.mu.m. Furthermore, a silver thin film was formed to serve as a light 
reflective layer by the DC magnetron sputtering method to a thickness of 
300 nm, and the backside electrode was formed on the silver thin film 
similar to Example 10, whereby a photovoltaic device was manufactured 
(device No. Example 11). 
TABLE 10-1 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
10 500 20 350 RF 5 
layer 
CH.sub.4 
2 60 mW/cm.sup.3 
H.sub.2 
400 DC 90 V 
B.sub.2 H.sub.6 /H.sub.2 
10 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 50 1 350 RF 200 
layer 
H.sub.2 
200 120 mW/cm.sup.3 
DC 80 V 
n-type 
SiH.sub.4 
15 50 15 100 Excluded 
5 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
TABLE 10-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
15 50 15 300 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
3 
(diluted to 10%) 
i-type 
SiH.sub.4 
70 150 5 300 RF 150 
layer 
GeH.sub.4 
30 25 mW/cm.sup.3 
H.sub.2 
200 DC 100 V 
n-type 
SiH.sub.4 
15 50 15 300 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
Comparative Example 9 
The transparent electrode, the p-, i-, n-, p-, i-, and n-type layers, the 
reflection enhancing layer, the light reflective layer, and a backside 
electrode were formed on a substrate under the same conditions as those 
according to Example 11 except the transparent electrode was formed on the 
substrate under the same conditions as those according to Comparative 
Example 7, whereby a photovoltaic device was manufactured (device No. 
Comparative Example 9). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 11 (device No. Example 11) and 
Comparative Example 9 (device No. Comparative Example 9) were measured by 
a method similar to that according to Example 8. As a result, the 
photovoltaic device according to Example 11 (device No. Example 11) 
exhibited a 1.08 times larger short-circuit current, an excellent series 
resistance 1.41 times larger, and excellent durability characteristics 
1.10 times those of the photovoltaic device according to Comparative 
Example 9 (device No. Comparative Example 9). Therefore, it was confirmed 
that the photovoltaic device (device No. Example 11) using the transparent 
electrode containing nitrogen atoms according to the present invention has 
excellent characteristics in comparison with those of the conventional 
photovoltaic device (device No. Comparative Example 9), and therefore a 
beneficial effect of the present invention was confirmed. 
Example 12 
The photovoltaic device according to the present invention was manufactured 
by the vacuum evaporation method and the microwave (hereinafter 
abbreviated to ".mu.W") and the glow discharge and decomposition method. 
First, a transparent electrode containing nitrogen atoms was formed on the 
substrate by the manufacturing apparatus 500 shown in FIG. 5 and adapted 
to perform the vacuum evaporation method. 
Referring to FIG. 5, reference numeral 502 represents a substrate in the 
form of a 50 mm .times.50 mm square which was 1 mm thick and which was 
made of barium borosilicate glass ("7059" manufactured by Corning). 
Reference numeral 504 represents an evaporation source composed of indium 
(In) and tin (Sn) in a molar ratio of 1:1. 
Reference numeral 510 represents a gas introduction valve which was 
connected to a cylinder (not shown) for N.sub.2 /O.sub.2 gas obtained by 
diluting N.sub.2 gas with O.sub.2 gas to 50 ppm. 
Reference numeral 512 represents a gas introduction valve which was 
connected to an O.sub.2 gas cylinder (not shown). 
First, the substrate 502 was heated to 350.degree. C. by the heater 503, 
and the inside of the deposition chamber 501 was exhausted by a vacuum 
pump (not shown). When the pressure reading of the vacuum gauge 508 had 
become about 1.times.10.sup.-5 Torr, the gas introduction valves 510 and 
512 were gradually opened to introduce the N.sub.2 /O.sub.2 gas and the 
O.sub.2 gas into the deposition chamber 501. In order to set the 
introduction flow rate of the N.sub.2 /O.sub.2 gas at 3 sccm and the 
O.sub.2 gas at 7 sccm at this time, the corresponding mass-flow 
controllers 511 and 513 were operated. Furthermore, the internal pressure 
of the deposition chamber 501 was set at 0.3 mTorr by adjusting the 
opening of the (butterfly type) conductance valve 509 while observing the 
vacuum gauge 508. Then, electric power was supplied from the AC power 
source 506 to the heater 505 to heat the evaporation source 504. Then, the 
shutter 507 was opened to commence the process for manufacturing the 
transparent electrode on the substrate 502. Simultaneously, the 
introduction of the N.sub.2 /O.sub.2 gas was changed from 3 sccm to 7 sccm 
at a predetermined rate and the O.sub.2 gas was changed from 7 sccm to 3 
sccm at a predetermined rate by operating the corresponding mass-flow 
controllers 511 and 513. When a transparent electrode which was 70 nm 
thick was formed, the shutter 507 was closed, the output from the AC power 
source 506 was turned off and the gas introduction valves 510 and 512 were 
closed, whereby the gas introduction into the deposition chamber 501 was 
stopped. Thus, a transparent electrode containing nitrogen atoms was 
manufactured. 
Then, the p-, i-, and n-type layers and the backside electrode were formed 
on the transparent electrode under the same conditions as those according 
to Example 8, whereby a photovoltaic device was manufactured (device No. 
Example 12). 
Comparative Example 10 
A conventional photovoltaic device was manufactured by a method similar to 
that according to Example 12. 
First, the transparent electrode was formed on the substrate by the 
manufacturing apparatus 500 shown in FIG. 5 and adapted to perform the 
vacuum evaporation method. 
Similarly to Example 5, the substrate 502 was heated to 350.degree. C. by 
the heater 503, and the gas introduction valve 512 was gradually opened to 
introduce the O.sub.2 gas into the deposition chamber 501 at 10 sccm. 
Furthermore, the internal pressure of the deposition chamber 501 was set 
at 0.3 mTorr. Then, electric power was supplied from the AC power source 
506 to the heater 505 to heat the evaporation source 504. Then, the 
shutter 507 was opened so that the process for manufacturing the 
transparent electrode on the substrate 502 was commenced. When a 
transparent electrode which was 70 nm thick was formed, the shutter 507 
was closed and the output from the AC power source 506 was turned off. 
Furthermore, the gas introduction valve 512 was closed to stop the gas 
introduction into the deposition chamber 501. Thus, the process for 
manufacturing the transparent electrode was completed. Furthermore, the 
p-, i-, and n-type layer and the backside electrode were formed on the 
transparent electrode under the same conditions as those according to 
Example 1, whereby a photovoltaic device was manufactured (device No. 
Comparative Example 10). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 12 (device No. Example 12) and 
Comparative Example 10 (device No. Comparative Example 10) were measured 
by a method similar to that according to Example 8. As a result, the 
photovoltaic device according to Example 12 (device No. Example 12) 
exhibited a 1.07 times larger short-circuit current, an excellent series 
resistance 1.42 times larger, and excellent durability characteristics 
1.10 times those of the photovoltaic device according to Comparative 
Example 10 (device No. Comparative Example 10). Therefore, it was 
confirmed that the photovoltaic device (device No. Example 5) using the 
transparent electrode containing nitrogen atoms according to the present 
invention has excellent characteristics in comparison with those of the 
conventional photovoltaic device (device No. Comparative Example 4), and 
therefore a beneficial effect of the present invention was confirmed. 
Furthermore, the distribution of the nitrogen atoms in the transparent 
electrode of the photovoltaic device according to Example 12 (device No. 
Example 12) was analyzed by using a secondary ionization mass analyzer 
("IMS-3F" manufactured by CAMECA), resulting in the quantity of nitrogen 
atoms apparently being reduced from the portion adjacent to the p-type 
layer toward the substrate. 
Example 13 
A 50 mm .times.50 mm square conductive substrate which was 1 mm thick, made 
of stainless steel (SUS430BA) and having mirror surfaces was used. A 
silver thin film serving as a light reflective layer and having a 
thickness of 300 nm and a ZnO thin film serving as a reflection enhancing 
layer and having a thickness of 1 .mu.m were sequentially formed thereon 
by the DC magnetron sputtering method. Then, the n-, i-, and p-type layers 
were formed on the conductive substrate under the manufacturing conditions 
shown in Table 11. 
TABLE 11 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
Bias (nm) 
__________________________________________________________________________ 
n-type 
SiH.sub.4 
30 50 10 350 Excluded 
10 
layer 
H.sub.2 
100 
PH.sub.3 H.sub.2 
10 
(diluted to 10%) 
i-type 
SiH.sub.4 
100 100 5 350 RF 400 
layer 
H.sub.2 
200 100 mW/cm.sup.3 
DC 75 V 
p-type 
SiH.sub.4 
10 400 20 300 Excluded 
5 
layer 
H.sub.2 
100 
B.sub.2 H.sub.6 /H.sub.2 
5 
(diluted to 10%) 
__________________________________________________________________________ 
Then, the transparent electrode was formed on the p-type layer by a method 
similar to that according to Example 12. The temperature of the substrate 
was set at 200.degree. C., the flow rate of the N.sub.2 /O.sub.2 gas was 
set at 7 sccm, the flow rate of the O.sub.2 gas was set at 3 sccm and the 
internal pressure of the deposition chamber 501 was set at 0.3 mTorr. 
Then, electric power was supplied from the AC power source 506 to the 
heater 505 to heat the evaporation source 504, and the shutter 507 was 
opened so that the process of manufacturing the transparent electrode on 
the substrate 502 was commenced. Simultaneously, the corresponding 
mass-flow controllers 511 and 513 were used to change the rate of the 
N.sub.2 /O.sub.2 gas from 7 sccm to 3 sccm at a predetermined rate and to 
change that of the O.sub.2 gas from 3 sccm to 7 sccm at a predetermined 
rate. When a transparent electrode which was 70 nm thick was formed, the 
shutter 507 was closed, the output from the AC power source 506 was turned 
off, and the gas introduction valves 510 and 512 were closed to stop the 
introduction of the gases into the deposition chamber 501. Thus, a 
transparent electrode containing nitrogen atoms was formed on the p-type 
layer. Furthermore, Al was evaporated on the transparent electrode to a 
thickness of 2 .mu.m to serve as a collecting electrode by vacuum 
evaporation, whereby a photovoltaic device was manufactured (device No. 
Example 13). 
Comparative Example 11 
A transparent electrode was formed on a p-type layer under the same 
conditions as those according to Comparative Example 10 except that the 
light reflective layer, the reflection enhancing layer, the n-, i-, and 
p-type layers were formed on the conductive substrate under the same 
manufacturing conditions as those according to Example 13 and the 
temperature of the substrate was made to be 200.degree. C. Furthermore, 
the collecting electrode was formed similarly to Example 13, whereby a 
photovoltaic device was manufactured (device No. Comparative Example 11). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 13 (device No. Example 13) and 
Comparative Example 11 (device No. Comparative Example 11) were measured 
by a similar method to that according to Example 8. As a result, the 
photovoltaic device according to Example 13 (device No. Example 13) 
exhibited a 1.07 times larger short-circuit current, an excellent series 
resistance 1.44 times larger, and excellent durability characteristics 
1.11 times those of the photovoltaic device according to Comparative 
Example 11 (device No. Comparative Example 11). Therefore, it was 
confirmed that the photovoltaic device (device No. Example 13) using the 
transparent electrode containing nitrogen atoms according to the present 
invention has excellent characteristics in comparison with those of the 
conventional photovoltaic device (device No. Comparative Example 11), and 
therefore a beneficial effect of the present invention was confirmed. 
Furthermore, the distribution of the nitrogen atoms in the transparent 
electrode of the photovoltaic device according to Example 13 (device No. 
Example 13) was analyzed by using a secondary ionization mass analyzer 
("IMS-3F" manufactured by CAMECA), resulting in the quantity of nitrogen 
atoms being considerably reduced from the portion adjacent to the p-type 
layer toward the substrate. 
Example 14 
The photovoltaic device according to the present invention was manufactured 
by the DC magnetron sputtering method and the radio frequency (hereinafter 
abbreviated to "RF") glow discharge and decomposition method. 
First, a transparent electrode containing nitrogen atoms was formed on the 
substrate under the same manufacturing conditions as those according to 
Example 8. 
Then, the manufacturing apparatus 600, composed of the raw material gas 
supply device portion 1020 and the deposition device portion 1100, as 
shown in FIG. 6 and adapted to perform the RF glow discharge and 
decomposition method, was used to manufacture the non-single-crystal 
silicon semiconductor layer on the transparent electrode. 
Referring to FIG. 6, reference numeral 1104 represents a substrate on which 
the aforementioned transparent electrode was formed. 
The gas cylinders 1071 to 1076 respectively were filled with the raw 
material gases which are the same as those according to Example 8, and the 
aforementioned gases were introduced into the mass-flow controllers 1021 
to 1026 in a similar operation manner to that according to Example 8. 
After the preparations for forming the layers had been completed as 
described above, the p-, i-, and n-type layers were formed on the 
substrate 1104. 
The p-type layer was manufactured in such a manner that the substrate 1104 
was heated to 300.degree. C. by the heater 1105, and the discharge valves 
1041 to 1043 and the auxiliary valve 1108 were gradually opened, so that 
the SiH.sub.4 gas, the H.sub.2 gas and the B.sub.2 H.sub.6 /H.sub.2 gas 
were introduced into the deposition chamber 1101 via the gas introduction 
pipe 1103. In order to set the introduction flow rate of the SiH.sub.4 gas 
at 2 sccm, the H.sub.2 gas at 50 sccm and that of the B.sub.2 H.sub.6 
/H.sub.2 gas at 1 sccm at this time, the corresponding mass-flow 
controllers 1021 to 1023 were operated. The internal pressure of the 
deposition chamber 1101 was set at 1 Torr by adjusting the opening of the 
conductance valve 1107 while observing the vacuum gauge 1106. Then, the 
output power of the RF power source (not shown) was set to 200 
mW/cm.sup.3, and the RF power was supplied to the cathode 1102 via the RF 
matching box 1112 to generate the RF glow discharge. Thus, the process of 
forming the p-type layer on the transparent electrode was commenced. When 
a p-type layer which was 5 nm thick was formed, the RF glow discharge was 
stopped and the discharge valves 1041 to 1043 and the auxiliary valve 1108 
were closed to stop the introduction of gas into the deposition chamber 
1101. Thus, the process of forming the p-type layer was completed. 
Then, the i-type layer was formed in such a manner that the substrate 1104 
was heated to 300.degree. C. by the heater 1105, and the discharge valves 
1041 and 1042 and the auxiliary valve 1108 were gradually opened to 
introduce the SiH.sub.4 gas and the H.sub.2 gas into the deposition 
chamber 1101 via the gas introduction pipe 1103. In order to set the flow 
rate of the SiH.sub.4 gas at 2 sccm and the H.sub.2 gas at 20 sccm at this 
time, the corresponding mass-flow controllers 1021 and 1022 were operated. 
In order to set the internal pressure of the deposition chamber 1101 at 1 
Torr, the opening of the conductance valve 1107 was adjusted while 
observing the vacuum gauge 1106. Then, the output power of an RF power 
source (not shown) was set to 5 mW/cm.sup.3, and the RF power was supplied 
to the cathode 1102 via the RF matching box 1112 to generate the RF glow 
discharge. As a result, the process of forming the i-type layer on the 
p-type layer was commenced. When an i-type layer which was 400 nm thick 
was formed, the RF glow discharge was stopped and the process of forming 
the i-type layer was completed. 
Then, the n-type layer was formed in such a manner that the substrate 1104 
was heated to 250.degree. C. by the heater 1105, and the discharge valve 
1044 was gradually opened so as to introduce the SiH.sub.4 gas, the 
H.sub.2 gas and the PH.sub.3 /H.sub.2 gas into the deposition chamber 1101 
via gas introduction pipe 1103. In order to set the flow rate of the 
Si.sub.4 gas at 2 sccm, the H.sub.2 gas at 20 sccm and the PH.sub.3 
/H.sub.2 gas at 1 sccm at this time, the corresponding mass-flow 
controllers 1021, 1022 and 1024 were operated. The internal pressure of 
the deposition chamber 1101 was set at 1 Torr by adjusting the opening of 
the conductance valve 1107 while observing the vacuum gauge 1106. Then, 
the output power of an RF power source (not shown) was set to 5 
mW/cm.sup.3, and the RF power was supplied to the cathode 1102 via the RF 
matching box 1112 to generate the RF glow discharge. Thus, the process of 
forming the n-type layer on the i-type layer was commenced. When an n-type 
layer which was 10 nm thick was formed, the RF glow discharge was stopped 
and the discharge valves 1041, 1042, and 1044 and the auxiliary valve 1108 
were closed to stop the introduction of gas into the deposition chamber 
1101. Thus, the process of manufacturing the n-type layer was completed. 
When each of the aforementioned layers was formed, the discharge valves 
1041 to 1046 must, of course, be closed completely except for the valves 
for the required gases. Furthermore, the undesirable retention of the 
gases in the deposition chamber 1101 and the pipes arranged from the 
discharge valves 1041 to 1046 to the deposition chamber 1101 is prevented 
by closing the discharge valves 1041 to 1046, by opening the auxiliary 
valve 1108, and by fully opening the conductance valve 1107 to temporarily 
exhaust the inside portion of the system to a high degree of vacuum if 
necessary. 
Then, the backside electrode was formed on the n-type layer by evaporation, 
similarly to Example 1, so that a photovoltaic device was manufactured 
(device No. Example 14). 
The conditions for manufacturing the photovoltaic device are shown in 
Tables 12-1 and 12-2. 
TABLE 12-1 
__________________________________________________________________________ 
Substrate 
Barium borosilicate glass 50 mm .times. 50 mm thickness 1 
__________________________________________________________________________ 
mm 
Transparent 
Conditions for manufacturing by DC magnetron sputtering 
Electrode 
Gas and Flow Rate 
Target In:Sn = 85:15 
(sccm) Temperature of substrate 
350.degree. 
O.sub.2 15 .fwdarw. 5 
Internal pressure 
2 mTorr 
(changed at a DC voltage -400 V 
predetermined rate) 
Thickness of the layer 
70 nm 
Ar 20 
N.sub.2 /O.sub.2 
5 .fwdarw. 15 
(changed at a 
predetermined rate) 
__________________________________________________________________________ 
TABLE 12-2 
__________________________________________________________________________ 
Conditions for manufacturing layers 
Temperature 
Name Internal 
of Thickness 
of Gas and flow rate 
.mu.W power 
pressure 
substrate 
of layer 
layer 
(sccm) (mW/cm.sup.3) 
(mTorr) 
(.degree.C.) 
(nm) 
__________________________________________________________________________ 
p-type 
SiH.sub.4 
2 200 1 300 5 
layer 
H.sub.2 
50 
B.sub.2 H.sub.6 /H.sub.2 
1 
(diluted to 10%) 
i-type 
SiH.sub.4 
2 5 1 300 400 
layer 
H.sub.2 
20 
n-type 
SiH.sub.4 
2 5 1 250 10 
layer 
H.sub.2 
20 
PH.sub.3 /H.sub.2 
1 
(diluted to 10%) 
Backside 
Al 2 .mu.m 
Electrode 
__________________________________________________________________________ 
Comparative Example 12 
The p-, i-, and n-type layers and the backside electrode were formed on a 
transparent electrode under the same conditions as those according to 
Example 14 except that a transparent electrode which was the same as that 
according to Comparative Example 7 was used, whereby a photovoltaic device 
was manufactured (device No. Comparative Example 12). 
The initial characteristics and the durability characteristics of the 
photovoltaic devices according to Example 14 (device No. Example 14) and 
Comparative Example 12 (device No. Comparative Example 12) were measured 
by a method similar to that according to Example 8. As a result, the 
photovoltaic device according to Example 14 (device No. Example 14) 
exhibited a 1.07 times larger short-circuit current, an excellent series 
resistance 1.41 times larger, and excellent durability characteristics 
1.10 times those of the photovoltaic device according to Comparative 
Example 12 (device No. Comparative Example 12). Therefore, it was 
confirmed that the photovoltaic device (device No. Example 14) using the 
transparent electrode containing nitrogen atoms according to the present 
invention has excellent characteristics in comparison with those of the 
conventional photovoltaic device (device No. Comparative Example 12), and 
therefore a beneficial effect of the present invention was confirmed. 
In the transparent electrodes according to the aforementioned examples, 
nitrogen atoms were distributed in an exponential manner in a region of 30 
to 500 .ANG. in the direction of the thickness, and the maximum density 
was 5 to 1000 ppm. 
The photovoltaic device, composed of a non-single-crystal silicon 
semiconductor layer and having a transparent electrode containing carbon 
atoms or nitrogen atoms or both carbon atoms and nitrogen atoms, exhibited 
beneficial effects in that the series resistance relating to the 
transparent electrode was reduced and the transmissivity was improved. 
Furthermore, the adhesion between the semiconductor layer and the 
transparent electrode was improved, causing leakage to be prevented even 
if it is used for a long time. As a result, the durability characteristics 
of the photovoltaic device were improved. 
In addition, since a large quantity of carbon atoms, nitrogen atoms, or 
both carbon atoms and nitrogen atoms is distributed in the transparent 
electrode in the portion adjacent to the semiconductor layer, the 
structural distortion which normally takes place due to the difference in 
the materials between the transparent electrode and the semiconductor 
layer can be satisfactorily prevented. 
Although the present invention has been described with reference to the 
specific examples, it should be understood that various modifications and 
variations can be easily made by those skilled in the art without 
departing from the spirit of the invention. Accordingly, the foregoing 
disclosure should be interpreted as illustrative only and not in a 
limiting sense. The present invention is limited only by the scope of the 
following claims.