JP2000261011A - Silicon-based thin-film photoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon-based thin-film photoelectric transducer which shows an increased open end voltage and has improved photoelectric conversion characteristics. SOLUTION: This transducer is provided with a transparent front electrode film 12, a silicon-based thin-film photoelectric conversion unit 13 which contains are conductivity type layer 131, a photoelectric conversion layer 132 composed of crystalline silicon-based thin-film, and an opposite conductivity type layer 133, a transparent rear conducting film 14, and a rear metal electrode film 15. The transparent rear conducting film 14 contains a high resistance transparent conductive oxide layer 141, containing aluminum and/or gallium and a low resistance transparent conductive oxide layer 142, containing aluminum and/or gallium in this order from the photoelectric conversion unit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film photoelectric conversion device, and more particularly to improvement in performance such as conversion efficiency of a silicon-based thin-film photoelectric conversion device represented by a solar cell.
In the specification of the present application, the terms “crystalline” and “microcrystal” also mean those partially including amorphous.

[0002]

2. Description of the Related Art In recent years, silicon-based photoelectric conversion devices using a thin film containing crystalline silicon such as polycrystalline silicon or microcrystalline silicon as a photoelectric conversion layer have been vigorously developed. These developments are mainly aimed at achieving both low cost and high performance of the photoelectric conversion device by forming a high-quality crystalline silicon thin film on an inexpensive substrate by a low-temperature process.

[0003] Such a silicon-based photoelectric conversion device generally includes a silicon-based photoelectric conversion device including a transparent front electrode provided on the light incident side, a photoelectric conversion layer formed of a one-conductivity-type layer, a crystalline silicon-based thin film, and a reverse-conductivity-type layer. The photoelectric conversion unit includes a thin-film photoelectric conversion unit and a back electrode provided on a side opposite to the front electrode with respect to the photoelectric conversion unit. Such silicon-based photoelectric conversion devices are expected to be applied not only to solar cells but also to various uses such as optical sensors.

Incidentally, it is known that the conversion efficiency of a silicon-based photoelectric conversion device is reduced due to various factors.
For example, since the crystalline silicon-based photoelectric conversion layer has a small absorption coefficient with respect to light in a long wavelength region, when the photoelectric conversion layer is thin, it can sufficiently absorb light in a long wavelength region among incident light. And the amount of photoelectric conversion tends to decrease. In order to solve this, for example, a metal film having a high light reflectance is provided on the back side of the photoelectric conversion unit, and a surface unevenness (surface texture) structure is provided on the metal film. Light incident on the photoelectric conversion layer is irregularly reflected into the photoelectric conversion layer by the surface uneven structure, and light absorption by the photoelectric conversion layer is enhanced (light confinement effect). Such a surface uneven structure may be provided also on the front electrode.

In recent years, many photoelectric conversion devices have been proposed in which a transparent conductive oxide film such as zinc oxide (ZnO) is formed on the above-mentioned metal film and a silicon-based photoelectric conversion unit is deposited thereon. For example, Japanese Patent Application Laid-Open No. 3-9947
No. 7; Japanese Unexamined Patent Publication No. Hei 7-263731; IEEE 1st Wor
ld Conf. on Photovoltaic Energy Conversion, p. 405
(1994); Applied Physics Letters, Vol. 70, p. 2975
(1997). By interposing the transparent conductive oxide film between the metal film of the back electrode and the silicon-based photoelectric conversion unit in this manner, thermal distortion due to the difference in the coefficient of thermal expansion between them is reduced, and metal atoms are reduced. It is possible to prevent the silicon-based photoelectric conversion unit from being diffused and mixed. As a result, not only the yield and reliability of the obtained photoelectric conversion device are improved, but also the photosensitivity is improved and the photoelectric conversion characteristics are improved.

[0006]

SUMMARY OF THE INVENTION However, the present inventors have developed a back electrode including a metal film having a surface uneven structure capable of producing a preferable irregular reflection in order to increase light absorption in a silicon-based thin film photoelectric conversion layer. If used,
It has been found that mechanical and electrical defects are apt to occur in the thin conductive layer of the photoelectric conversion unit formed thereon, resulting in a decrease in open-end voltage of the obtained solar cell and a decrease in yield due to short circuit. In particular, it has been found that when the light reflecting metal film included in the back electrode is provided with a surface unevenness structure, if the pitch of the unevenness is narrow, a leak current is likely to occur, and the open-end voltage tends to decrease.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the open-circuit voltage in a silicon-based thin film photoelectric conversion device, thereby improving the photoelectric conversion characteristics.

[0008]

Means for Solving the Problems The inventors of the present invention have repeatedly studied to solve the above-mentioned problems, and as a result, aluminum and / or gallium have been added to the transparent conductive film constituting the back electrode, in particular, the zinc oxide (ZnO) film. Is added, and the transparent conductive oxide layer is formed as a two-layer structure having different resistances, that is, as a two-layer structure of a high resistance layer on the photoelectric conversion unit side and a low resistance layer on the back metal film side, It has been found that the open-circuit voltage is improved and the conversion efficiency is improved.

That is, according to the present invention, a silicon-based thin-film photoelectric conversion unit including a transparent front electrode film, a one-conductivity-type layer, a photoelectric conversion layer composed of a crystalline silicon-based thin film, and a reverse-conductivity-type layer; And a back metal electrode film, wherein the transparent back conductive film comprises, in order from the photoelectric conversion unit side, a high-resistance transparent conductive oxide layer containing aluminum and / or gallium;
Alternatively, a silicon-based thin-film photoelectric conversion device including a low-resistance transparent conductive oxide layer containing gallium is provided.

[0010] In the present invention, the high-resistance transparent conductive oxide layer contains aluminum and / or gallium in a content of 0.1%.
Preferably, the low-resistance transparent conductive oxide layer contains aluminum and / or gallium at a ratio of 6% by weight or less.

In the present invention, the high-resistance transparent conductive oxide layer preferably has a thickness of 30 nm or less, and the low-resistance transparent conductive oxide layer preferably has a thickness of 90 nm or less. .

Further, in the present invention, the high-resistance transparent conductive oxide layer and the low-resistance transparent conductive oxide layer each preferably contain zinc oxide as a main component.

In the present invention, the light incident side is called a front surface, and the opposite side is called a back surface.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. The same parts are denoted by the same reference symbols throughout the drawings.

FIG. 1 is a schematic sectional view schematically showing a silicon-based thin-film photoelectric conversion device according to a first embodiment of the present invention. The photoelectric conversion device illustrated in FIG. 1 includes a silicon-based thin film photoelectric conversion unit having a pin structure, and light is incident from the substrate side.

Referring to FIG. 1, a silicon-based thin-film photoelectric conversion device 10 includes a transparent front electrode 12
, A silicon-based thin-film photoelectric conversion unit 13, a transparent back conductive film 14, and a back metal electrode film 15.

The substrate 11 can be made of a transparent substrate material such as an organic film, ceramics or low-melting glass.

The transparent front electrode 12 is formed of a transparent conductive oxide material, and may have a single-layer structure or a multilayer structure. The transparent front electrode 12 is preferably made of indium tin oxide (ITO), tin oxide (SnO ₂ ),
It is formed of a transparent conductive oxide selected from zinc oxide (ZnO), a mixture thereof, and the like.

The transparent front electrode 12 is formed by vacuum deposition, CVD,
Alternatively, it can be formed by a known vapor deposition method such as sputtering.

The surface of the transparent conductive oxide material layer constituting the front electrode 12 may have a flat surface, but preferably has surface irregularities (texture structure) as shown in FIG. It is preferable that the height difference of the unevenness in such a surface unevenness structure is 10 to 100 nm. In addition, the pitch of the unevenness is preferably larger than the height difference of the unevenness and 25 times or less thereof, more preferably 4 times or more and 20 times or less the height difference of the unevenness. Specifically, the pitch of the unevenness is It is preferably from 300 to 1000 nm.

Here, the height difference between the irregularities is the average value of the difference between the heights of the convex portions and the concave portions, and the pitch is approximately 0.1 to 5 μm.
It represents the average value of the distances between adjacent convex portions or convex portions or concave portions and concave portions that appear in m periods. Such a surface uneven structure can be achieved by image processing of a cross-sectional TEM (transmission electron microscope) photograph of the transparent front electrode 12 or AFM (atomic force microscope)
It can also be determined by surface observation and surface shape measurement by using.

The transparent front electrode 12 having such a surface uneven structure can be formed by various methods known per se. For example, a concave-convex structure is formed on the surface of the substrate 11 by etching or the like, and a thin transparent front electrode 12 is formed thereon, so that the surface of the transparent electrode 12 can have a concave-convex structure along the concave-convex structure of the substrate 11. .

The silicon-based photoelectric conversion unit 13 formed on the transparent front electrode 12 includes a p-type layer 131, a crystalline silicon-based thin-film photoelectric conversion layer 132, and an n-type layer 133 having a conductivity type opposite to that of the p-type layer. Including. All the semiconductor layers included in the photoelectric conversion unit 13 can be deposited by a plasma CVD method under the condition of a base temperature of 400 ° C. or less. As the plasma CVD method, besides a generally well-known parallel plate type RF plasma CVD, a plasma CVD using a high-frequency power supply from an RF band having a frequency of 150 MHz or less to a VHF band can be used.

P-type layer 131 formed on front electrode 12
For example, a p-type silicon-based thin layer doped with p-type impurity atoms such as boron and aluminum can be used. The material of the p-type layer 131 is not only amorphous silicon, but also alloy materials such as amorphous silicon carbide and amorphous silicon germanium, as well as polycrystalline or microcrystalline partially containing amorphous. Of silicon or its alloy material can also be used. If desired, by irradiating such a deposited p-type layer 131 with a pulsed laser beam, the crystallization fraction and the carrier concentration due to the impurity atoms determining the conductivity type can be controlled.

As the crystalline silicon-based photoelectric conversion layer 132 formed on the p-type layer 131, a non-doped true semiconductor polycrystalline silicon thin film, a microcrystalline silicon film having a volume crystallization fraction of 80% or more, or a trace amount A silicon-based thin film material having a weak p-type or weak n-type and sufficiently having a photoelectric conversion function can be used. However, the photoelectric conversion layer 132 is not limited thereto, and may be formed using an alloy material such as silicon carbide or silicon germanium.

The thickness of the photoelectric conversion layer 132 is equal to 0.1.
The thickness is in the range of 5 to 20 μm, which is a necessary and sufficient film thickness as the crystalline silicon-based thin film photoelectric conversion layer. The crystalline silicon-based thin-film photoelectric conversion layer 132 has a thickness of 40
Since it is formed at a low temperature of 0 ° C. or less, it contains a large amount of hydrogen atoms that terminate or inactivate defects in crystal grain boundaries and grains, and its hydrogen content is preferably in the range of 1 to 30 atomic%. . Furthermore, many of the crystal grains contained in the crystalline silicon-based thin-film photoelectric conversion layer 132 extend in a columnar shape from the underlayer and grow upward, and are parallel to the film surface (110).
Of the preferred crystal orientation plane, and its (22)
The intensity ratio of the (111) diffraction peak to the 0) diffraction peak is preferably 0.4 or less.

The n formed on the crystalline photoelectric conversion layer 132
As the mold layer 133, an n-type silicon-based thin film or the like doped with n-type impurity atoms such as phosphorus and nitrogen can be used. In addition, as a material of the p-type layer 133, an alloy material such as amorphous silicon carbide or amorphous silicon germanium may be used in addition to amorphous silicon, and polycrystalline or partially amorphous is included. Microcrystalline silicon or its alloy material can also be used.

Here, the photoelectric conversion unit 13 to be deposited is
A surface texture structure including fine irregularities is formed on the upper surface 13A. This is due to the fact that the crystalline photoelectric conversion layer 132 included in the photoelectric conversion unit 13 naturally forms an uneven texture structure at the time of deposition thereof, whereby the upper surface 13A of the photoelectric conversion unit 13 has a wide wavelength range. A fine surface uneven texture structure more suitable for scattering incident light is obtained, and the light confinement effect in the photoelectric conversion device is also increased.

In the present invention, the transparent conductive film 14 formed on the photoelectric conversion unit 13
-Resistance transparent back surface conductive oxide layer 14 provided in contact with the substrate
1 and low-resistance transparent conductive oxide layer 14 provided thereon
2 and a multilayer structure including a two-layer structure. In the present invention, high resistance and low resistance are relative terms, and low resistance means having lower resistance than high resistance.

The high resistance layer 141 and the low resistance layer 142 constituting the transparent backside conductive layer 14 of the present invention are both transparent containing aluminum and / or gallium (hereinafter, aluminum and / or gallium is referred to as a dopant). It is formed of a conductive oxide. As the transparent conductive oxide, one or more transparent conductive oxides selected from ITO, SnO ₂ and ZnO can be preferably used, and those containing ZnO as a main component are particularly preferable.

The high-resistance transparent conductive oxide layer 141 contains a dopant at a ratio of preferably 0.5% by weight or less, more preferably 0.01 to 0.1% by weight.
The high resistance layer 141 preferably has a thickness of 30 nm or less, more preferably 5 nm to 15 nm.

On the other hand, the low-resistance transparent conductive oxide layer 1
No. 42 contains a dopant, preferably in a proportion of 6% by weight or less, more preferably in a proportion of 2 to 5% by weight. The low-resistance layer 142 preferably has a thickness of 90 nm or less, but the total thickness with the high-resistance layer 141 is 6 nm.
0 nm to 120 nm, more preferably 80 nm to 100 n
m is particularly preferable.

The high-resistance layer 141 and the low-resistance layer 142 that constitute the transparent back conductive film 14 of the present invention are known per se except that a transparent oxide target containing a predetermined ratio of a dopant is used. It can be suitably formed by a sputtering method. As the sputtering conditions at that time, the sputtering conditions described above for the transparent front electrode 12 can be preferably adopted.

The transparent backside conductive film 14 of the present invention has a high-resistance transparent conductive oxide layer 141 and a low-resistance transparent conductive oxide layer 142 from the photoelectric conversion unit side, so that the surface unevenness structure of the backside metal electrode film is obtained. , The open-circuit voltage can be improved, and as a result, the conversion efficiency can be increased.

The back metal electrode film 15 formed on the transparent back conductive film 14 is preferably formed of a metal having high light reflectivity, and has a 95% or more ratio to light having a wavelength in the range of 500 to 1200 nm. It is particularly preferred to have a high reflectivity. Such a back metal interelectrode film 15 is made of silver (A
g), gold (Au), aluminum (Al), copper (Cu)
And one selected from platinum and platinum (Pt) or an alloy containing the same, and can be formed as a single layer or a multilayer. Back metal electrode film 15
It is particularly preferable that at least the surface region is formed of a silver-based metal material made of silver or a silver alloy. For example, the back metal electrode film 15 is made of silver having high light reflectivity by 100%.
It can be formed by vacuum deposition at a temperature of from about 330 ° C., more preferably from 200 to 300 ° C.

As described above, the photoelectric conversion unit 1
Since the upper surface 13A of the substrate 3 has a naturally uneven structure, the transparent back conductive film 14 and the back metal electrode film 1 formed thereon are formed.
5 is also preferably provided with the surface uneven structure.

In the photoelectric conversion device 10 having the pin-type photoelectric conversion unit 13 shown in FIG. 1, light to be subjected to photoelectric conversion enters from the substrate 11 side.

FIG. 2 is a schematic sectional view schematically showing a silicon-based thin-film photoelectric conversion device according to a second embodiment of the present invention. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the detailed description thereof will be omitted from the following description.

The silicon-based thin-film photoelectric conversion device 2 shown in FIG.
Numeral 0 denotes an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device. The tandem-type photoelectric conversion device 20 shown in FIG. 2 includes a transparent front electrode 12 on a substrate 11 as in the case of the photoelectric conversion device 10 of FIG. A front photoelectric conversion unit 21 is formed on the transparent front electrode 12. The front photoelectric conversion unit 21 preferably includes a p-type microcrystalline or amorphous silicon-based thin film 211 and an amorphous silicon-based thin film photoelectric conversion layer 212 that is substantially a genuine semiconductor, which are sequentially deposited by a plasma CVD method. , And n-type microcrystalline or amorphous silicon-based thin film 213
including.

On the front photoelectric conversion unit 21, the photoelectric conversion unit 13 including the p-type layer 131, the photoelectric conversion layer 132, and the n-type layer 133 shown in FIG. This rear photoelectric conversion unit 1
3 above the high-resistance transparent conductive oxide layer 141 of the present invention.
A transparent back conductive film 14 including a low-resistance transparent conductive oxide layer 142 and a back metal electrode film 15 are formed in the same manner as in the case of the photoelectric conversion device 10 of FIG. 1, thereby forming the tandem type shown in FIG. The photoelectric conversion device 20 is completed.

Next, a silicon-based thin-film photoelectric conversion device according to a third embodiment of the present invention will be described with reference to FIG. The photoelectric conversion device 30 illustrated in FIG. 3 includes a silicon-based thin-film photoelectric conversion unit having a nip structure, and light is incident from the side opposite to the substrate.

Referring to FIG. 3, a silicon-based thin-film photoelectric conversion device 30 includes
2, a transparent back conductive film including the low-resistance back transparent conductive oxide layer 331 and the high-resistance back transparent conductive oxide layer 332, and the front electrode 35.

The substrate 31 can be formed of the same substrate material as the substrate 11 in the photoelectric conversion device 10 of FIG. However, since the substrate 31 does not need to be transparent,
It can also be formed of a metal material such as stainless steel.

Back metal electrode film 3 formed on substrate 31
Reference numeral 2 corresponds to the back metal electrode film 15 in FIG.

The back metal electrode film 32 preferably has a surface uneven structure (surface texture structure). Such a concavo-convex structure on the upper surface of the back metal electrode film 32 is formed by processing the surface of the substrate 31 into a concavo-convex structure by etching or the like in advance, and transmitting the concavo-convex structure to the upper surface of itself. It can be obtained by forming the film 32. Alternatively, after depositing a transparent conductive oxide layer (not shown) having an uneven surface on the substrate 31, a thin back metal electrode film 32 capable of transmitting the uneven structure to the upper surface thereof is formed. It can also be obtained by:

The height difference of the unevenness in the surface unevenness structure of the back metal electrode film 32 is in the range of 0.01 to 2 μm, and the pitch of the unevenness is larger than the height difference.
It is preferably 5 times or less, more preferably 4 to 20 times. By using the back metal electrode film 32 having such a surface unevenness structure, it is possible to improve the light confinement effect and obtain a high-performance photoelectric conversion device without lowering the open-circuit voltage or lowering the production yield. it can. In addition, such a surface uneven structure can be measured by a TEM (transmission electron microscope) photograph or a surface observation by an AFM (atomic force microscope) of a cross section of the back metal electrode film 32 as described above.

The transparent back conductive film 33 provided on the back metal electrode film 32 corresponds to the transparent back conductive film 14 in FIG. That is, the transparent back conductive film 33
Are a low-resistance transparent conductive oxide layer 331 corresponding to the low-resistance transparent conductive oxide layer 142 in FIG. 1 and a high-resistance transparent conductive oxide layer 331 corresponding to the high-resistance transparent conductive oxide layer 141 in FIG. And a layer 332.

The photoelectric conversion unit 34 formed on the back metal electrode film 32 is similar to the photoelectric conversion device 1 of FIG. 1 except that the arrangement of the p-type layer 131 and the n-type layer 133 in FIG.
0 has the same configuration as the photoelectric conversion unit 13. That is, the photoelectric conversion unit 33 includes, from the substrate 31 side, an n-type layer 341 corresponding to the n-type layer 133 in FIG.
The crystalline silicon-based thin film photoelectric conversion layer 342 corresponding to the crystalline silicon-based thin film photoelectric conversion layer 132 of FIG.
A p-type layer 343 corresponding to the mold layer 131 is provided.

The transparent front electrode 35 formed on the photoelectric conversion unit 33 corresponds to the transparent front electrode 12 in FIG.

Further, as a grid electrode on the transparent front electrode 35, a comb-shaped metal electrode 36 including a layer of at least one or more metals selected from Al, Ag, Au, Cu and Pt or an alloy thereof is preferably used. Are formed.

Such a silicon-based thin-film photoelectric conversion device 3
At 0, the light hν to be photoelectrically converted is emitted from the transparent front electrode 35 side.

FIG. 4 is a schematic sectional view schematically showing a silicon-based thin-film photoelectric conversion device according to a fourth embodiment of the present invention. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the detailed description thereof will be omitted from the following description.

The silicon-based thin-film photoelectric conversion device 4 shown in FIG.
Reference numeral 0 denotes an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device similar to the photoelectric conversion device shown in FIG. In the tandem-type photoelectric conversion device 40 shown in FIG.
As in the case of the photoelectric conversion device 30, the back metal electrode film 32 and the high-resistance transparent conductive oxide layer 331 are formed on the substrate 31.
In addition, a rear transparent conductive film 33 including a low-resistance transparent conductive oxide layer 332 and a photoelectric conversion unit 34 including an n-type layer 341, a photoelectric conversion layer 342, and a p-type layer 343 are formed. The photoelectric conversion unit 34 constitutes a rear photoelectric conversion unit.

A front photoelectric conversion unit 41 is further formed on the rear photoelectric conversion unit 34. This front photoelectric conversion unit 41 is provided by p
It has the same configuration as the front photoelectric conversion unit 21 in the tandem photoelectric conversion device 20 of FIG. 2 except that the arrangement of the type thin film 211 and the n-type thin film 213 is reversed. That is,
The front photoelectric conversion unit 41 includes an n-type silicon-based thin film 411 corresponding to the n-type thin film 213 in FIG. 2 and an amorphous silicon-based thin film photoelectric conversion layer substantially a genuine semiconductor corresponding to the photoelectric conversion layer 212 in FIG. 412, and the p-type thin film 2 of FIG.
11 includes a p-type silicon-based thin film 413. On the front photoelectric conversion unit 41, a front transparent electrode film 35 is provided.
And the comb-shaped metal electrode 36 is a photoelectric conversion device 30 shown in FIG.
The tandem-type photoelectric conversion device 40 as shown in FIG. 4 is thus completed.

[0055]

The present invention will be described below with reference to examples.

Example 1 In this example, a silicon-based thin-film photoelectric conversion device having the structure shown in FIG. 1 was manufactured.

That is, first, an SnO ₂ film was formed as a transparent front electrode film 12 on a glass substrate 11.

Next, on the transparent front electrode (SnO ₂ ) film 12, the p-type silicon layer 1 constituting the photoelectric conversion unit 13 is formed.
31, non-doped crystalline silicon-based photoelectric conversion layer 132
And an n-type silicon layer 133 was formed by a plasma CVD method. Non-doped crystalline silicon-based photoelectric conversion layer 1
No. 32 was formed to a thickness of 3.0 μm by RF plasma CVD at a base temperature of 300 ° C. In the crystalline photoelectric conversion layer 132, the hydrogen content determined by secondary ion mass spectrometry was 2.3 atomic%, and the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction was 0%. .2.

Next, a high-resistance transparent conductive oxide layer 141 and a low-resistance transparent conductive oxide layer 142 were sequentially deposited on the photoelectric conversion unit 13 as the transparent back conductive film 14 by RF sputtering. The sputtering conditions for the high-resistance layer 141 and the low-resistance layer 142 include a sputtering gas of Ar,
RF of 3 × 10 ⁻³ Torr, 850 mW / cm ²
The power density and the substrate temperature of 300 ° C. In forming the high resistance layer 141, a zinc oxide target containing 0.1% by weight of aluminum or gallium was used. On the other hand, when forming the low resistance layer 142,
A zinc oxide target containing 3% by weight of aluminum or gallium was used. High resistance layer 14 obtained
1 had a specific resistance of 5 × 10 ⁻² Ωcm, and the low-resistance layer 142 had a specific resistance of 6 × 10 ⁻⁴ Ωcm.

Finally, silver was deposited as a back metal electrode film 15 on the transparent back conductive film 14 by a sputtering method.

The incident light h is applied to the photoelectric conversion device thus obtained.
When the output characteristics were measured by irradiating a light of AM 1.5 with a light amount of 100 mW / cm ² as ν, the open-circuit voltage was set to 0.
52V, the short-circuit current density of 25mA / cm ^2, a fill factor is 72%, and a conversion efficiency of 9.36%.

Comparative Example 1 A photoelectric conversion device was manufactured in the same manner as in Example 1, except that a high-resistance transparent conductive film was not formed and only a low-resistance transparent conductive film was formed in forming the transparent back conductive film 14.

The output characteristics of the obtained photoelectric conversion device were measured in the same manner as in Example 1.
8 V, short circuit current density 25 mA / cm ² , fill factor 6
8% and the conversion efficiency was 8.16%.

Example 2 In this example, an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device having the structure shown in FIG. 2 was manufactured.

That is, first, according to the method of the first embodiment,
An SnO ₂ film was formed as a transparent front electrode 12 on a substrate 11.

The front photoelectric conversion unit 21 was formed on the transparent front electrode 12. This front photoelectric conversion unit 2
1 includes a p-type layer 211, an amorphous silicon-based photoelectric conversion layer 212, and an n-type layer 213 which are sequentially stacked. Note that the thickness of the amorphous photoelectric conversion layer 212 is 300
nm.

On the obtained front photoelectric conversion unit 21,
As in Example 1, a p-type silicon layer 131, a non-doped crystalline silicon-based photoelectric conversion layer 132, and an n-type silicon layer 133 were formed by a plasma CVD method. However, the thickness of the crystalline silicon-based photoelectric conversion layer 132 is 3.
It was set to 0 μm.

Finally, similarly to the first embodiment, the high-resistance transparent conductive oxide layer 141 and the low-resistance transparent conductive oxide layer 142
And a back metal electrode film 15 made of silver.

When the output characteristics of the photoelectric conversion device thus obtained were measured in the same manner as in Example 1, the open-circuit voltage was 1.42 V, the short-circuit current density was 12.3 mA / cm ² ,
The fill factor was 76% and the conversion efficiency was 13.27%.

Example 3 In this example, a silicon-based thin-film photoelectric conversion device having the structure shown in FIG. 3 was manufactured.

That is, first, a back metal electrode film 32 made of silver having a thickness of 300 nm was deposited on the glass substrate 11 by a sputtering method.

Next, the low-resistance transparent conductive oxide layer 331
And a high-resistance transparent conductive oxide layer 332 were deposited by RF sputtering according to the method of the first embodiment.

Next, on the obtained transparent conductive film 33, an n-type layer 341, a non-doped crystalline silicon-based photoelectric conversion layer 342, and a p-type layer 34 constituting the photoelectric conversion unit 34 are formed.
3 was formed by a plasma CVD method. The non-doped crystalline silicon-based photoelectric conversion layer 342 was formed to a thickness of 3.0 μm by an RF plasma CVD method at a base temperature of 300 ° C. In this crystalline photoelectric conversion layer 342, 2
The hydrogen content determined by secondary ion mass spectrometry was 2.3.
Atomic%, and the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction was 0.10.

Next, a zinc oxide film was formed as a transparent front electrode film 35 on the photoelectric conversion unit 34 in the same manner as in Example 1, and a comb-shaped silver electrode 36 for taking out current was formed thereon.

When the output characteristics of the photoelectric conversion device thus obtained were measured in the same manner as in Example 1, the open-circuit voltage was 0.55 V, the short-circuit current density was 26.5 mA / cm ² ,
The fill factor was 77% and the conversion efficiency was 11.2%.

Comparative Example 2 A photoelectric conversion device was manufactured in the same manner as in Example 3 except that a single zinc oxide layer was formed using a zinc oxide target containing no yttrium as a target when forming the transparent back conductive film 33. Produced.

The output characteristics of the obtained photoelectric conversion device were measured in the same manner as in Example 1.
The short circuit current density was 26.5 mA / cm ² , the fill factor was 73%, and the conversion efficiency was 10.05%.

Example 4 In this example, an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device having the structure shown in FIG. 4 was manufactured.

That is, according to the method of the third embodiment, the substrate 3
On 1, a back metal electrode film 32, a transparent back conductive film 33 composed of a low-resistance transparent conductive oxide layer 331 and a high-resistance transparent conductive oxide layer 332, and a photoelectric conversion unit 34 were formed. However, the thickness of the crystalline silicon-based photoelectric conversion layer 342 was set to a thickness of 3.0 μm.

Then, the obtained rear photoelectric conversion unit 3
4, a front photoelectric conversion unit 41 was further formed.
The front photoelectric conversion unit 41 includes an n-type layer 411, an amorphous silicon-based photoelectric conversion layer 412, and a p-type layer 413 that are sequentially stacked. Note that the thickness of the amorphous photoelectric conversion layer 212 was set to 300 nm.

Finally, a transparent front electrode film 35 and a comb-shaped silver electrode 36 were formed on the photoelectric conversion unit 21 in the same manner as in the first embodiment.

When the output characteristics of the photoelectric conversion device thus obtained were measured in the same manner as in Example 1, the open-circuit voltage was 1.42 V, the short-circuit current density was 12.4 mA / cm ² ,
The fill factor was 77% and the conversion efficiency was 13.55%.

[0083]

As described above, according to the present invention, there is provided a silicon-based thin-film photoelectric conversion device which exhibits an increased open-circuit voltage and thus has improved photoelectric conversion characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a crystalline silicon-based thin film photoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device according to a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view for explaining a crystalline silicon-based thin film photoelectric conversion device according to a third embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating an amorphous / crystalline tandem silicon-based thin film photoelectric conversion device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 11, 31 ... substrate 12, 35 ... transparent front electrode film 13, 21, 34, 41 ... photoelectric conversion unit 14, 33 ... transparent back electrode film 15, 32 ... back metal electrode film 36 ... comb-shaped metal electrode 131, 211, 343, 413: p-type layer 132, 212, 342, 412: photoelectric conversion layer 133, 213, 341, 411: n-type layer 141, 332: high-resistance transparent conductive oxide layer 142, 331: low-resistance transparent conductivity Oxide layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F051 AA03 AA04 AA05 BA17 CA02 CA04 CA16 DA04 DA15 FA02 FA03 FA04 FA06 FA09 FA15 FA18 FA19 FA30 GA03

Claims (4)

[Claims] 1. A transparent front electrode film, a silicon-based thin-film photoelectric conversion unit including a one-conductivity-type layer, a photoelectric conversion layer composed of a crystalline silicon-based thin film, and a reverse-conductivity-type layer, a transparent back conductive film, and a back metal electrode. A transparent high-resistance transparent conductive oxide layer containing aluminum and / or gallium and a low-resistance transparent conductive film containing aluminum and / or gallium in this order from the photoelectric conversion unit side. A silicon-based thin-film photoelectric conversion device comprising a conductive oxide layer. 2. The high-resistance transparent conductive oxide layer contains aluminum and / or gallium in a proportion of 0.5% by weight or less, and the low-resistance transparent conductive oxide layer contains aluminum and / or gallium. The silicon-based thin-film photoelectric conversion device according to claim 1, wherein the silicon-based thin film photoelectric conversion device contains 6% by weight or less. 3. The high-resistance transparent conductive oxide layer has a thickness of 30%.
3. The silicon-based thin-film photoelectric conversion device according to claim 1, wherein the low-resistance transparent conductive oxide layer has a thickness of 90 nm or less. 4. 4. The method according to claim 1, wherein the high-resistance transparent conductive oxide layer and the low-resistance transparent conductive oxide layer each contain zinc oxide as a main component. The silicon-based thin-film photoelectric conversion device as described in the above.