Patent Application
20120174972
1. Field of the Invention
The present invention relates to a transparent conductive film and a device with the same.
2. Description of Related Art
Transparent conductive films have been conventionally used in various devices such as display devices like liquid display devices, organic electroluminescence devices, solar cell devices like thin film solar cells, dye-sensitized solar cells, and electronic components.
It is preferable that the resistance of such a transparent conductive film is small. Conventionally, a transparent conductive film made from indium oxide containing tin (ITO) and a transparent conductive film made from zinc oxide (ZnO) and the like are known. Other than the transparent conductive film containing tin (ITO), a transparent conductive film made of indium oxide containing cerium added by a spattering method is disclosed as a transparent conductive film made from indium oxide, for instance. See Japanese Patent Publication Laid-open No. Hei 8-260134 for example.
However, there has been a problem in making a transparent conductive film made of indium oxide containing cerium due to the difficulty in making the film absorb less light on the long-wavelength side, while having good carrier mobility and low electric resistance.
Embodiments according to the present invention consider the above-identified problem and provide a transparent conductive film that is capable of absorbing less light on the long-wavelength side, has good carrier mobility and low electric resistance.
An aspect of the present invention is a transparent conductive film includes indium oxide containing hydrogen and cerium and having a substantially polycrystalline structure. Specific resistance of the transparent conductive film is no greater than 3.4×10−4Ω·cm and carrier mobility is no less than 70 cm2/Vs.
Another aspect of the present invention is a solar cell including a glass substrate, a textured transparent conductive film, a first-type amorphous silicon layer formed on the transparent conductive film, a substantially intrinsic i-type amorphous silicon layer formed on the first-type amorphous silicon layer, a second-type amorphous silicon layer formed on the i-type amorphous silicon layer, and another transparent conductive film formed on the second-type amorphous silicon layer, in which the transparent conductive film comprises indium oxide containing hydrogen and cerium and having a substantially polycrystalline structure, in which specific resistance of the transparent conductive film is no greater than 3.4×10−4Ω·cm and carrier mobility is no less than 70 cm2/Vs.
Yet another aspect of the present invention is a display apparatus including a transparent conductive film, in which the transparent conductive film comprises indium oxide containing hydrogen and cerium and having a substantially polycrystalline structure, and in which specific resistance of the transparent conductive film is no greater than 3.4×10−4Ω·cm and carrier mobility is no less than 70 cm2/Vs.
According to the embodiments of the present invention, the transparent conductive film is capable of absorbing less light on the long-wavelength side, having good carrier mobility and lowering electric resistance because the transparent conductive film includes indium oxide containing hydrogen and cerium and comprises substantially polycrystalline structure, wherein specific resistance is not greater than 3.4×10−4Ω·cm.
Accordingly, when the embodiment of the present invention is applied in devices such as display devices like liquid display devices, organic electroluminescence devices, solar cell devices like crystalline solar cells, thin film solar cells, dye-sensitized solar cells, and electronic components, the performance of these devices can be improved.
The embodiments of the present invention provides a transparent conductive film capable of absorbing less light on the long-wavelength side, having good carrier mobility and lowering electric resistance, and a device with the same.
Embodiments of the invention are explained with reference to the drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted. All of the drawings are provided to illustrate the respective examples only. No dimensional proportions in the drawings shall impose a restriction on the embodiments. For this reason, specific dimensions and the like should be interpreted with the following descriptions taken into consideration. In addition, the drawings include parts whose dimensional relationship and ratios are different from one drawing to another.
Prepositions, such as “on”, “over” and “above” may be defined with respect to a surface, for example a layer surface, regardless of that surface's orientation in space. The preposition “above” may be used in the specification and claims even if a layer is in contact with another layer. The preposition “on” may be used in the specification and claims when a layer is not in contact with another layer, for example, when there is an intervening layer between them.
A transparent conductive film according to an embodiment is explained below by referring to the figures.
In
Transparent conductive film 2 is a film that includes indium oxide as an essential ingredient and also contains cerium (Ce) and hydrogen (H). Namely, transparent conductive film 2 includes hydrogen (H), cerium (Ce), indium (In), and oxygen (O), and contains indium oxide(In2O3) doped with hydrogen (H) and cerium (Ce) as impurities.
Transparent conductive film 2 includes substantially polycrystalline structure and contains numerous pillar-like structures bristled up to cover the substrate body. Further, transparent conductive film 2 contains a very little amorphous portion.
A hydrogen (H) content in transparent conductive film 2 is preferably 1.0×1021 atoms/cm3 and more preferably is in the order of 1021 atoms/cm3. The hydrogen content here refers to an amount of hydrogen contained in the middle of transparent conductive film 2 in its thickness direction and is substantially the same as the average content in the film other than in the vicinities of both surfaces of transparent conductive film 2. The hydrogen content concentration is preferably greater in the substrate body 1 side than in the film surface side, and more preferably, the concentration increases gradually toward the substrate body 1 side.
The specific resistance of transparent conductive film 2 is not greater than 3.4×10−4Ω·cm. The smaller the specific resistance of transparent conductive film 2, the more preferable. However, the specific resistance may be between not greater than 3.4×10−4Ω·cm and not less than 1.0×10−4Ω·cm.
A cerium (Ce) content in transparent conductive film 2 is preferably between 1.0×1020 atoms/cm3 or more and 1.4×1021 atoms/cm3 or less, and more preferably is between 2.4×1020 atoms/cm3 or more and 1.2×1021 atoms/cm3 or less, and further more preferably is between 4.8×1020 atoms/cm3 or more and 1.1×1021 atoms/cm3 or less, and still further more preferably is between 7.5×1020 atoms/cm3 or more, and 1.0×1021 atoms/cm3 or less, and yet further more preferably is between 7.5×1020 atoms/cm3 or more, and 8.5×1020 atoms/cm3 or less.
Hereinafter, a method of manufacturing a transparent conductive film according to the embodiment is explained.
First, substrate body 1 is prepared by removing impurities on the surface by cleaning.
Note that in the case where substrate body 1 is a body including a substantially intrinsic i-type amorphous silicon layer and a p-type amorphous silicon layer formed on an n-type monocrystalline silicon substrate in this order, substrate body 1 is formed as follows: upon removing impurities by cleaning the n-type monocrystalline silicon substrate, a substantially intrinsic i-type amorphous silicon layer and a p-type amorphous silicon layer are formed in this order on n-type monocrystalline silicon substrate by using the RF plasma CVD method. The conditions of the RF plasma CVD method may be at a frequency of about 13.56 MHz, a formation temperature of approximately 100° C.-300° C., a reaction pressure of about 5 Pa-100 Pa, and an RF power of about 1 mW/cm2-500 mW/cm2. Subsequently, substrate body 1 is cleaned again.
Next, the transparent conductive film including indium oxide containing hydrogen (H) and cerium (Ce) as impurities, is formed on substrate body 1 by using the ion plating method in an atmosphere of Ar/O2 gas mixture and steam at a room temperature. A sintered body of In2O3 powder that contains a predetermined amount of cerium oxide (CeO2) powder as a dopant is used for ingredients. In this case, the amount of cerium (Ce) contained in the transparent conductive film can be changed by using the sintered body with varied contents of cerium oxide (CeO2).
Next, the crystallization of the above-mentioned transparent conductive film is preferably proceeded by annealing at approximately 200° C. for about 1 hour, thereby transparent conductive film 2 is prepared. In manufacturing various devices, a separate annealing process may not be required in case the annealing treatment is combined with other manufacturing processes.
From the measurement results of electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and x-ray diffraction (XRD), transparent conductive film 2 according to the embodiment is found to include pillar-like structures and that contains substantially polycrystalline structures, and a very little amorphous portion.
The indication of “large” in the column for “hydrogen content” refers to the content of hydrogen in a transparent conductive film being approximately 2.0×1021 atoms/cm3, and the indication of “small” refers to the content of hydrogen being approximately 9.0×1020 atoms/cm3. “(111)Si substrate” refers to a substrate body including an i-type amorphous silicon layer that is substantially intrinsic and has a layer thickness of approximately 5 nm and a p-type amorphous silicon layer that is substantially intrinsic and has a layer thickness of approximately 5 nm formed on an n-type monocrystalline silicon substrate in this order.
Comparative examples 1-10 are manufactured using the same manufacturing method as in the embodiment except for sintered bodies and the amount of steam. Note that transparent conductive films in comparative examples 1-7 include indium oxide as an essential ingredient and also contains hydrogen (H) and cerium (Ce), and transparent conductive films in comparative examples 8-10 include indium oxide as an essential ingredient and also contains hydrogen (H) and tin (Sn).
Further, when the hydrogen (H) content in the transparent conductive film is in the order of 1021 atoms/cm3 such as 2.0×1021 atoms/cm3, cerium (Ce) content in the transparent conductive film is preferably between 2.4×1020 atoms/cm3 or more and 1.2×1021 atoms/cm3 or less and the specific resistance is not greater than 2.5×10−4Ω·cm, and more preferably is between 4.8×1020 atoms/cm3 or more and 1.1×1021 atoms/cm3 or less and the specific resistance is not greater than 2.2×10−4Ω·cm, and further more preferably is between 7.5×1020 atoms/cm3 or more and 1.0×1021 atoms/cm3 or less, and still further more preferably is between 7.5×1020 atoms/cm3 or more and 8.5×1020 atoms/cm3 or less.
A device performs better as an electrode when the carrier mobility value is greater because the specific resistance decreases. Therefore, it is preferable that the carrier mobility value is great.
When the amount of hydrogen (H) in the transparent conductive film is in the order of 1021 atoms/cm3, such as 2.0×1021 atoms/cm3, and the cerium (Ce) content in the transparent conductive film is between 1.0×1020 atoms/cm3 or more and 1.2×1021 atoms/cm3 or less, the carrier mobility becomes greater than approximately 90 cm2/Vs which is preferable. It is more preferable that the cerium (Ce) content in the transparent conductive film be between 2.4×1020 atoms/cm3 or more and 1.1×1021 atoms/cm3 or less, and further more preferable that it be between 4.8×1020 atoms/cm3 or more and 1.0×1021 atoms/cm3 or less, and yet further more preferable that the cerium content be between 7.5×1020 atoms/cm3 or more, and 8.5×1020 atoms/cm3 or less.
In view of the specific resistance and the carrier mobility in the above-mentioned transparent conductive films, the content of cerium (Ce) in the transparent conductive film is preferably between 1.0×1020 atoms/cm3 or more and 1.4×1021 atoms/cm3 or less, and more preferably is between 2.4×1020 atoms/cm3 or more and 1.1×1021 atoms/cm3 or less, and further more preferably between 4.8×1020 atoms/cm3 or more and 1.0×1021 atoms/cm3 or less, and still further more preferably, between 7.5×1020 atoms/cm3 or more, and 8.5×1020 atoms/cm3 or less.
As to the carrier density, when a value of the carrier density is higher, the light with a longer wavelength is absorbed. Also, carriers themselves cause scattering. As a result, the carrier mobility is decreased. Therefore, when the specific resistance has the same value, it is preferable that the carrier density be lower. However, when the carrier density is too low, the grain boundary scattering within the film increases which results in the decrease of the carrier mobility. Therefore, it is preferable that the carrier density be within a predetermined range.
Note that
The transparent conductive film according to the embodiment can be properly used in display devices such as liquid display devices, organic electroluminescence devices, solar cell devices such as crystalline solar cells, thin film solar cells, dye-sensitized solar cells, and electronic components.
For example, the transparent conductive film including a transparent conductive film having a texture structure, a first type amorphous silicon layer, a substantially intrinsic i-type amorphous silicon layer, and another amorphous silicon layer having an opposite type to the first type, and a transparent conductive film formed on a glass substrate, in this order, may be used in a thin film solar cell.
The embodiment can be used in the fields of display devices such as liquid display devices, organic electroluminescence devices, solar cell devices such as crystalline solar cells, thin film solar cells, dye-sensitized solar cells, and electronic components, because the embodiment provides a transparent conductive film capable of absorbing less light on the long-wavelength side, having good carrier mobility and lowering electric resistance, and a device with the same.
The embodiment includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the embodiment is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-216259 | Sep 2009 | JP | national |
This application is a continuation application of International Application No. PCT/JP2010/066077, filed on Sep. 16, 2010, entitled “TRANSPARENT CONDUCTIVE FILM AND A DEVICE WITH THE SAME,” which claims priority based on Article 8 of Patent Cooperation Treaty from prior Japanese Patent Applications No. 2009-216259, filed on Sep. 17, 2009, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2010/066077 | Sep 2010 | US |
| Child | 13421512 | US |
