Tungsten-doped indium oxide evaporation target material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of metal oxide target materials, and particularly discloses a tungsten-doped indium oxide evaporation target material and a preparation method and application thereof. The preparation raw materials of the tungsten-doped indium oxide target material comprise indium oxide and tungsten oxide; wherein the indium oxide is micron-sized indium oxide powder, and the D50 of the indium oxide powder is 10 to 200 [mu] m; the tungsten oxide is nanoscale tungsten oxide powder, and the D50 of the tungsten oxide powder is 10-100 nm. The tungsten-doped indium oxide target material has the relative density suitable for RPD process film coating and has good conductivity, and an oxide film obtained by using the IWO target material for RPD film coating has high light transmittance performance and is suitable for being applied to preparation of photovoltaic solar cells. The invention also provides a preparation method and application of the IWO target material.

Description

Technical Field

[0001] The present invention relates to the technical field of metal oxide target materials, and in particular to a tungsten-doped indium oxide evaporation target material and a preparation method and application thereof. Background Art

[0002] At present, transparent conductive oxide (TCO) films have become the key materials in the field of photovoltaic solar cells, especially in the production of high-efficiency solar cells. These TCO films have attracted widespread attention because of their characteristics of allowing sunlight to pass through while effectively collecting light-generated charges, thereby improving the efficiency of solar energy conversion. TCO films are usually prepared by reactive plasma deposition (RPD), chemical vapor deposition (CVD), physical vapor deposition (PCD), electrochemical deposition and inkjet printing. Among them, the RPD method has received special attention due to its unique advantages such as high deposition rate, better film quality, and higher target material utilization. In the field of photovoltaic solar cells, TCO films prepared by RPD can not only improve the photoelectric conversion efficiency of solar cells, but also reduce production costs, which is of great significance for achieving cost-effective solar cell products. Therefore, RPD technology shows broad application prospects in solar cell manufacturing and is one of the important directions for current and future research and development of solar cell technology. Different from PVD magnetron sputtering, the RPD process generally uses a porous target material with a relative density of about 60%. This is because during the RPD coating process, a target material with too high a density is prone to cracking, while a target material with too low a density is prone to splashing dust or structural collapse, making it impossible to obtain high-quality films.

[0003] Thin films coated with indium tin oxide (ITO) targets are widely used because of their high transmittance, good electrical conductivity, and stability in a variety of environments. In addition, the processing technology of ITO thin films is mature and can achieve uniform deposition on large-area substrates. However, the high cost of ITO targets, sensitivity to water vapor, and rigidity in flexible solar cells limit their scope of application. Therefore, researchers are looking for other TCO materials to replace ITO targets, among which tungsten-doped indium oxide (IWO) targets have become the focus of research due to their potential advantages in chemical stability, environmental stability, and suitability for flexible battery processes. The advantages of IWO targets, such as high mobility and high transmittance in the full band of sunlight, also make them more advantageous than ITO in the application of photovoltaic cells. However, IWO films face certain challenges in terms of electrical conductivity and coating process complexity. Currently, the high-temperature sintering effect of the IWO target preparation process is not ideal. Tungsten oxide easily sublimates above 850°C and evaporates particularly severely above 1250°C. Therefore, tungsten oxide will evaporate during the sintering process and its composition is unstable. This is especially true for porous target materials used in RPD coating processes, as their composition content and uniformity are more difficult to control.

[0004] Therefore, there is an urgent need to improve and optimize the existing IWO target material and its preparation method to improve the doping uniformity and the photoelectric effect of the prepared oxide film. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a tungsten-doped indium oxide target (IWO). The tungsten-doped indium oxide target of the present invention has a relative density between 55% and 63%, is very suitable for coating in the RPD process, and has a low resistivity and good electrical conductivity. The oxide film obtained by RPD coating using the IWO target of the present invention has high light transmittance performance and is suitable for use in the preparation of photovoltaic solar cells.

[0006] The invention also provides a method for preparing a tungsten-doped indium oxide target material.

[0007] The invention also provides a TCO film.

[0008] The present invention also proposes the application of the above-mentioned IWO target material and TCO film.

[0009] In a first aspect of the present invention, a tungsten-doped indium oxide target is provided, wherein the raw materials for preparing the target include indium oxide and tungsten oxide;

[0010] Wherein, the indium oxide is a micron-sized indium oxide powder, and the D50 of the indium oxide powder is 10 to 200 μm;

[0011] The tungsten oxide is nano-scale tungsten oxide powder, and the D50 of the tungsten oxide powder is 10-100 nm.

[0012] According to a specific embodiment of the present invention, the IWO target material provided by the present invention has at least the following beneficial effects:

[0013] The relative density of the IWO target material of the present invention is between 55% and 63%, which is very suitable for coating in the RPD process. The resistivity of the target material is between 2 and 6×10 -2 The IWO target material of the present invention has a low resistivity and good electrical conductivity. The oxide film obtained by RPD coating has high light transmittance and is suitable for preparing photovoltaic solar cells.

[0014] According to some embodiments of the present invention, the preparation raw materials include 92 to 98 parts of indium oxide and 2 to 8 parts of tungsten oxide by mass.

[0015] According to some embodiments of the present invention, D50 of the indium oxide powder is 20-100 μm.

[0016] According to some embodiments of the present invention, D50 of the tungsten oxide powder is 20-50 nm.

[0017] A second aspect of the present invention provides a method for preparing a tungsten-doped indium oxide target as described in the first aspect of the present invention, comprising the following steps:

[0018] S1. Dispersing indium oxide and tungsten oxide in organic solutions respectively, mixing the dispersions, irradiating with ultraviolet light, and annealing to obtain powders;

[0019] S2, molding the powder, and sintering to obtain an IWO precursor;

[0020] S3, crushing the IWO precursor, sieving, grinding, and spray granulating to obtain IWO powder;

[0021] S4, pressing the IWO powder into a mold, and sintering to obtain an IWO target.

[0022] According to a specific embodiment of the present invention, the preparation method of the IWO target provided by the present invention makes the tungsten oxide nanoparticles fully and evenly attached to the surface of the indium oxide particles in the liquid environment by fully and evenly dispersing in a liquid environment and combining with ultraviolet light irradiation. The surface modification method makes the doped oxide and the matrix particles fully premixed, so that the target material has a high uniformity, and then the oxide film obtained by coating the target material has high light transmittance; and the preparation method of the IWO target material of the present invention does not require the traditional high-temperature sintering, and the volatility of the tungsten oxide that is easily volatile by high-temperature sintering can be significantly reduced, so that the component content of the target material is more controllable; and the IWO target material prepared by the method of the present invention has a target material relative density suitable for RPD process coating, which is conducive to obtaining a higher deposition rate, a better film quality and a higher target material utilization rate.

[0023] According to some embodiments of the present invention, the organic solution in step S1 includes at least one of methanol, ethanol, isopropanol or polyvinyl pyrrolidone.

[0024] According to some embodiments of the present invention, the dispersion method in step S1 is ultrasonic dispersion.

[0025] According to some embodiments of the present invention, the frequency of the ultrasonic dispersion is 20 to 60 kHz.

[0026] According to some embodiments of the present invention, the parameters of the ultraviolet light irradiation in step S1 are: wavelength 100-400nm, intensity 30-150μW / cm 2 , time 7 to 13 hours.

[0027] The present invention finds that irradiating indium oxide micron particles and tungsten oxide nanoparticles in a liquid phase dispersion environment with ultraviolet light of appropriate intensity helps the tungsten oxide nanoparticles to fully and evenly adhere to the indium oxide micron particles and avoid agglomeration of tungsten oxide particles, thereby improving the doping uniformity of the subsequently prepared target material and helping to prevent cracking of the sintered body. The prepared target material is more suitable for coating in the RPD process.

[0028] According to some embodiments of the present invention, the parameters of the ultraviolet light irradiation in step S1 are: wavelength 200-300nm, intensity 60-120μW / cm 2 , time 8 to 12 hours.

[0029] According to some embodiments of the present invention, the annealing method in step S1 is to anneal in an annealing furnace at 300-500° C. under an argon atmosphere for 0.5-2 h.

[0030] According to some embodiments of the present invention, the pressure of the compression molding in step S2 is 1-2 MPa.

[0031] According to some embodiments of the present invention, the sintering method in step S2 is to increase the temperature to 800-850° C. at a heating rate of 1-3° C. / min in an oxygen atmosphere or an air atmosphere, and keep the temperature for 2-3 hours.

[0032] According to some embodiments of the present invention, the screening in step S3 is through a sieve of 60-200 mesh.

[0033] According to some embodiments of the present invention, the screening in step S3 is through a sieve with a mesh size of 80 to 160.

[0034] According to some embodiments of the present invention, the grinding method described in step S3 is to add zirconium oxide balls, pure water and a dispersant to the sieved IWO precursor powder, and ball mill for 12 to 18 hours.

[0035] According to some embodiments of the present invention, the compression molding pressure in step S4 is 20-30 MPa.

[0036] According to some embodiments of the present invention, the sintering described in step S4 is: in an oxygen sintering furnace, the temperature is increased to 600-650°C at a heating rate of 1-3°C / min for debinding, and the heat preservation time is 2-3 hours, and then the temperature is increased to 850-900°C at a heating rate of 0.5-2°C / min, and the heat preservation time is 3-4 hours, and then the temperature is increased to 1050-1150°C at a heating rate of 0.5-1°C / min, and the heat preservation time is 2-3 hours, and then cooled to room temperature.

[0037] The sintering of the target material in the scheme of the present invention does not require the use of traditional high temperatures above 1200°C, and the maximum sintering temperature is only 1150°C, which can effectively avoid the volatilization of tungsten oxide, control the most suitable relative density of the target material, improve the uniformity of the target material and ensure the stability of the target material component content, thereby improving the quality of the target material and the oxide film prepared therefrom.

[0038] A third aspect of the present invention provides a TCO film, wherein the raw material for preparing the TCO film is the tungsten-doped indium oxide target material described in the first aspect of the present invention.

[0039] The preparation method of the TCO film is as follows:

[0040] According to some embodiments of the present invention, the tungsten-doped indium oxide target material described in the first aspect of the present invention is coated by a reactive plasma deposition method (RPD method) to obtain a TCO thin film.

[0041] The fourth aspect of the present invention provides the use of the tungsten-doped indium oxide target described in the first aspect of the present invention and the TCO film described in the third aspect of the present invention in a solar cell.

[0042] The tungsten-doped indium oxide target material of the present invention has a suitable relative density and good electrical conductivity, and the component content is controllable and the doping uniformity is high. The oxide film obtained by RPD process coating has a high light transmittance, which can effectively improve the photoelectric conversion efficiency of solar cells, and can also reduce production costs to achieve cost-effective solar cell products.

[0043] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0045] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0046] Example 1

[0047] This embodiment provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0048] The raw materials for preparing the IWO target material of this embodiment are 92 parts by mass of indium oxide and 8 parts by mass of tungsten oxide;

[0049] The indium oxide is a micron-sized indium oxide powder with a D50 of 20 to 100 μm, and the tungsten oxide is a nano-sized tungsten oxide powder with a D50 of 20 to 50 nm.

[0050] The preparation method of the IWO target material in this embodiment is as follows:

[0051] 1) Take the above-mentioned nano-scale tungsten oxide powder and micron-scale indium oxide powder, disperse them in 99.9% ethanol, and ultrasonically treat (40kHz) until the particles are evenly dispersed as observed by naked eyes. Then mix the two dispersions, and then use ultraviolet lamp to irradiate the mixed dispersion. The irradiation parameters are: ultraviolet light wavelength 254nm, intensity 90μW / cm 2 , irradiation time 12h; after the ultraviolet light irradiation is completed, the mixed dispersion is placed in an annealing furnace at 400°C under an argon atmosphere for 1h, and indium oxide powder with surface modified tungsten oxide nanoparticles is collected;

[0052] 2) The powder obtained in step 1) is subjected to a compression molding process at a molding pressure of 2 MPa, and the green body obtained by the compression molding is placed in an oxygen atmosphere (or an air atmosphere) for calcination at a heating rate of 1.5° C. / min to 800° C., and kept at this temperature for 2 h to obtain an IWO precursor;

[0053] 3) crushing the precursor obtained in step 2), collecting the IWO precursor powder after passing through a 160-mesh sieve, adding 60 wt% of zirconium oxide balls, 150 wt% of pure water and 2 wt% of a dispersant, mixing, and fully grinding for 12 h. The ground powder is spray-dried to obtain IWO powder;

[0054] 4) The IWO powder obtained in step 3) is molded into a green embryo at a molding pressure of 20 MPa, and then placed in an oxygen sintering furnace, heated to 600° C. at a heating rate of 2° C. / min for degreasing, and kept warm for 2 hours; after degreasing, heated to 850° C. at a heating rate of 1° C. / min, and kept warm for 3.5 hours; then heated to 1050° C. at a heating rate of 0.5° C. / min, and kept warm for 2.5 hours; cooled to room temperature to obtain a high-uniform IWO evaporation target embryo; the sintered embryo is cut and surface-polished to obtain an IWO evaporation target block with a diameter of 30 mm and a height of 40 mm.

[0055] Example 2

[0056] This embodiment provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0057] The difference between this embodiment and embodiment 1 is that the raw materials for preparing the IWO target material in this embodiment are 93.5 parts by mass of indium oxide and 6.5 parts by mass of tungsten oxide, and the ultraviolet irradiation time in step 1) is 11 hours.

[0058] Example 3

[0059] This embodiment provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0060] The difference between this embodiment and embodiment 1 is that the raw materials for preparing the IWO target material in this embodiment are 95 parts by mass of indium oxide and 5 parts by mass of tungsten oxide, the ultraviolet irradiation time in step 1) is 10.5 hours; the molding pressure in step 2) is 1.5 MPa, and the temperature is raised to 850°C; in step 3), the grinding time is 14 hours after passing through an 80-mesh sieve; in step 4), the temperature is raised to 650°C for degreasing, the heat preservation time is 2.5 hours, and then the temperature is raised to 850°C, the heat preservation time is 3.5 hours, and finally the temperature is raised to 1150°C.

[0061] Example 4

[0062] This embodiment provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0063] The difference between this embodiment and embodiment 3 is that the raw materials for preparing the IWO target material in this embodiment are 96.5 parts by mass of indium oxide and 3.5 parts by mass of tungsten oxide, and the ultraviolet irradiation time in step 1) is 9 hours.

[0064] Example 5

[0065] This embodiment provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0066] The difference between this embodiment and embodiment 3 is that the raw materials for preparing the IWO target material in this embodiment are 98 parts by mass of indium oxide and 2 parts by mass of tungsten oxide, the ultraviolet irradiation time in step 1) is 8 hours; the molding pressure in step 2) is 1 MPa; in step 3), the grinding time is 18 hours through an 80-mesh sieve; in step 4), the temperature is raised to 650°C for degreasing, the heat preservation time is 3 hours, and then the temperature is raised to 900°C, the heat preservation time is 3.5 hours, and finally the temperature is raised to 1150°C.

[0067] Comparative Example 1

[0068] This comparative example provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0069] The difference between this comparative example and Example 3 is that the ultraviolet irradiation time in step 1) of this comparative example is 5 hours.

[0070] Comparative Example 2

[0071] This comparative example provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0072] The difference between this comparative example and Example 3 is that the ultraviolet irradiation time in step 1) of this comparative example is 15 h.

[0073] Comparative Example 3

[0074] This comparative example provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0075] The difference between this comparative example and Example 3 is that the maximum sintering temperature in step 4) of this comparative example is 1350°C.

[0076] Comparative Example 4

[0077] This comparative example provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0078] The difference between this comparative example and Example 3 is that in step 1) of this comparative example, the ultraviolet irradiation step is eliminated and the two oxide powders are mixed by dry method.

[0079] Comparative Example 5

[0080] This comparative example provides an IWO evaporation target material with high uniformity and provides a preparation method thereof.

[0081] The difference between this comparative example and Example 1 is that the raw materials for preparing the IWO target material in this comparative example are 90 parts by mass of indium oxide and 10 parts by mass of tungsten oxide.

[0082] This comparative example exhibited cracking during sintering in step 4) of the preparation process.

[0083] Test Case

[0084] The IWO targets prepared in the embodiments and comparative examples were subjected to performance tests of target volatilization rate, relative density and target resistivity, and the average light transmittance of the thin films obtained by RPD coating of the IWO targets was tested. The doping ratios, partial preparation processes and test results of the embodiments and comparative examples are shown in Table 1.

[0085] Testing methods for various indicators:

[0086] 1) Target material volatility: measure the target material mass difference before and after sintering / target material mass before sintering;

[0087] 2) Relative density: wax seal test;

[0088] 3) Target resistivity: resistivity meter test;

[0089] 4) Average light transmittance: tested by UV-visible spectrophotometer;

[0090] The RPD coating method for preparing oxide thin films is as follows: placing the IWO target materials of each embodiment and comparative example in a water-cooled crucible of an RPD device, using white glass as a sample substrate, and pumping the vacuum pressure to 0.4×10 -3 Pa, introduce argon-oxygen mixed gas, in which the oxygen content is 20% to 30%, the oxygen flow rate is 80sccm, the chamber pressure after inflation is 0.3Pa, the DCG current is 120 to 180A, adjust the rotation angle and inclination angle of the electron gun, focus the plasma beam spot to the target surface for stable ignition and then start coating, the thin film obtained after deposition is annealed in air atmosphere to obtain an IWO transparent conductive film with a film thickness of 100 to 110nm.

[0091] Table 1 Doping ratio, preparation process and test results of each embodiment and comparative example

[0092]

[0093] From the above test results, it can be seen that the target material volatilization rate is low in the process of preparing IWO target material by using the scheme of the present invention, which is less than 5%. The relative density of the prepared target material is between 55% and 63%, which is very suitable for coating in RPD process. The resistivity of IWO target material prepared by the scheme of the present invention is between 2 and 6×10 -2 Ω·cm, the resistivity is low, and it has good conductivity; in addition, the oxide film obtained by RPD coating using the IWO target material of the present invention has high light transmittance performance, and the average light transmittance of the film reaches more than 88%, which is suitable for the preparation of photovoltaic solar cells. Examples 1 to 5 of the present invention control the oxide doping ratio and the ultraviolet light irradiation time to obtain an IWO target material with suitable density and uniform doping without cracking the sintered body. The sintered target material is excellent in resistivity and density. The processed evaporation target material can be stably used for RPD coating, and the average transmittance of the obtained film is significantly improved.

[0094] During the preparation of Comparative Example 1, when the ultraviolet irradiation time was insufficient, the tungsten oxide nanoparticles failed to fully and evenly adhere to the surface of the indium oxide particles in the liquid environment, and the prepared IWO target had a low relative density of only 40%. In addition, due to the uneven doping of tungsten oxide, the resistivity of the IWO target was too high and the average light transmittance of the obtained film was reduced, thereby greatly reducing the performance of the oxide film. The IWO target prepared in this comparative example was also not suitable for the RPD coating process. Correspondingly, during the preparation of Comparative Example 2, the ultraviolet irradiation time was extended, which may have caused the tungsten oxide nanoparticles to further agglomerate and grow after being attached to the surface of the indium oxide micron particles, thereby making the gaps between the powders too large, and thus causing the density of the obtained target to be low, which was not suitable for RPD coating, and the average light transmittance of the oxide film obtained by coating was also reduced.

[0095] During the preparation process of Comparative Example 3, the sintering temperature of the target material is too high, which makes it easier to cause the volatilization of tungsten oxide during the sintering process, which in turn leads to too low a relative density of the target material, resulting in too high a resistivity of the target material and a decrease in the average light transmittance of the oxide film obtained by coating. In Comparative Example 4, a dry mixing method is used. The uniformity of the two oxide powders mixed by this conventional method is poor, and it is difficult to achieve a high uniformity doping effect in the preparation of tungsten-doped indium oxide target materials, which also causes the resistivity of the target material to be too high and the average transmittance of the film to be reduced. Therefore, it is not suitable for RPD process coating. In Comparative Example 5, since the doping amount of tungsten oxide is too high, reaching 10wt%, too many tungsten oxide nanoparticles easily cause excessive lattice distortion of the target material, resulting in cracking during the sintering process of the target material.

[0096] Compared with the existing ITO target material for heterojunction and perovskite solar cells, the target material prepared by the present invention has a relative density of 55% to 63% by doping with tungsten. At the same time, the doped oxide and the matrix particles are fully premixed by surface modification in the liquid phase environment, and the target material obtained is highly uniform by controlling the ultraviolet light irradiation time. The oxide film prepared by RPD has excellent uniformity and a high average light transmittance. This target material is applied to photovoltaic heterojunction cells and perovskite cells, has good light transmittance, is suitable for the target material purpose of RPD coating, and improves the battery conversion efficiency.

[0097] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A tungsten-doped indium oxide target, characterized in that: The preparation raw materials include indium oxide and tungsten oxide; Wherein, the indium oxide is a micron-sized indium oxide powder, and the D50 of the indium oxide powder is 10 to 200 μm; The tungsten oxide is nano-scale tungsten oxide powder, and the D50 of the tungsten oxide powder is 10-100 nm.

2. The tungsten-doped indium oxide target according to claim 1, characterized in that: The raw materials for preparation include 92-98 parts of indium oxide and 2-8 parts of tungsten oxide by mass.

3. The method for preparing a tungsten-doped indium oxide target according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Dispersing indium oxide and tungsten oxide in organic solutions respectively, mixing the dispersions, irradiating with ultraviolet light, and annealing to obtain powders; S2, molding the powder, and sintering to obtain an IWO precursor; S3, crushing the IWO precursor, sieving, grinding, and spray granulating to obtain IWO powder; S4, pressing the IWO powder into a mold, and sintering to obtain an IWO target.

4. The preparation method according to claim 3, characterized in that: The parameters of the ultraviolet light irradiation in step S1 are: wavelength 100-400nm, intensity 30-150μW / cm 2 , time 7 to 13 hours.

5. The preparation method according to claim 3, characterized in that: The screening in step S3 is through a sieve of 60 to 200 meshes.

6. The preparation method according to claim 3, characterized in that: The compression molding pressure in step S2 is 1-2 MPa, and / or the compression molding pressure in step S4 is 20-30 MPa.

7. The preparation method according to claim 3, characterized in that: The sintering described in step S4 is as follows: in an oxygen sintering furnace, the temperature is increased to 600-650°C at a heating rate of 1-3°C / min for debinding, the heat preservation time is 2-3h, and then the temperature is increased to 850-900°C at a heating rate of 0.5-2°C / min, and the heat preservation time is 3-4h, and then the temperature is increased to 1050-1150°C at a heating rate of 0.5-1°C / min, and the heat preservation time is 2-3h, and then cooled to room temperature.

8. A TCO film, characterized in that: The raw material for preparing the TCO film is the tungsten-doped indium oxide target material as described in any one of claims 1 to 2.

9. The TCO film according to claim 8, characterized in that: The preparation method of the TCO film is as follows: The tungsten-doped indium oxide target material according to any one of claims 1 to 2 is coated by a reactive plasma deposition method to obtain a TCO film.

10. Use of the tungsten-doped indium oxide target according to any one of claims 1 to 2 or the TCO film according to any one of claims 8 to 9 in a solar cell.

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