IO target material suitable for RPD, preparation method and application of IO target material, and heterojunction battery

Abstract

The invention belongs to the technical field of photovoltaic cells, and provides an IO target material suitable for RPD, a preparation method and application of the IO target material, and a heterojunction cell. The preparation method comprises the following steps: taking indium oxide powder, carrying out first grinding, and then adding a first binder to prepare first mixed powder; the preparation method comprises the following steps: carrying out primary molding and static pressing to prepare a first target material biscuit, degreasing and presintering at 1400-1500 DEG C for 8-10 hours to obtain a presintered IO blank, crushing, grinding, adding a second binder, drying to obtain second mixed powder, molding again and carrying out static pressing to obtain a second target material biscuit, and finally degreasing and staged vacuum hot pressed sintering to obtain the target material. And preparing the IO target material. The relative density of the prepared pure IO target material is about 60%, the pure IO target material can be directly used for an RPD coating film and a deposited TCO thin film, the carrier concentration is low, the migration rate is high, the light transmittance is high, the pure IO target material is used for a heterojunction cell device, and the photoelectric conversion efficiency of a cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and more specifically, to an IO target material suitable for RPD, a preparation method and application thereof, and a heterojunction cell. Background Art

[0002] Heterojunction cells, that is, depositing intrinsic amorphous silicon thin films and doped amorphous (micro)crystalline silicon thin films on both sides of N-type silicon to form a heterojunction structure with a crystalline silicon substrate, have excellent passivation effects and high cell conversion efficiency. However, due to the poor lateral conductivity of amorphous silicon thin films, a layer of transparent conductive oxide thin film (TCO thin film for short) needs to be deposited on the outside of the film as a conductive and light-transmitting layer. The preparation methods of TCO thin films include magnetron sputtering (PVD for short), reactive plasma deposition (RPD for short), etc.

[0003] The basic principle of PVD is: under the action of electric and magnetic fields, the process gas Ar is ionized into Ar + Ions, accelerated high-energy particles (Ar + ) obtains high energy and bombards the target material, the atoms on the surface of the target material break away from the original lattice and escape, the sputtered particles are deposited on the substrate surface and react with oxygen atoms to form oxides. RPD is a process method in which an electron gun emits an electron beam to evaporate the target material under vacuum conditions, and the evaporated particles fly to the substrate surface and condense into a film.

[0004] When magnetron sputtering (PVD) is used to deposit TCO thin films, high-energy particles will bombard the surface of the substrate, causing performance damage and affecting the performance of the film layer. Compared with the PVD method, RPD causes less damage to the surface of the substrate and has a low film forming process temperature, so the deposited TCO thin film has better performance. The raw materials commonly used in existing RPD coatings are cerium oxide doped indium oxide (ICO) and tungsten oxide doped indium oxide (IWO). Both materials are doped on the basis of indium oxide, and the prepared thin films have a higher mobility (100-120cm 2 / VS), but the mobility still has room for improvement. Moreover, after indium oxide is doped, if the doped elements are not integrated into the lattice when forming a film, it is easy to become a recombination center and affect the grain boundary scattering of carriers. The parasitic absorption of light by doped particles will reduce the light transmittance of the film layer, making it impossible to take into account both high conductivity and high transmittance. For example, a Chinese patent (publication number CN114242805A) discloses a laminated TCO film, a silicon heterojunction battery and a preparation method thereof, which uses an ICO or IWO film deposited by RPD with a mobility of 80-100cm 2 / VS, but this method uses a multi-doped oxide target material, which needs to be micro-doped based on indium oxide. If the mixing is not uniform, it is likely to cause fluctuations in material properties.

[0005] Therefore, there is an urgent need to develop a target material with lower or even no doping concentration and higher mobility, which can be used for RPD deposition to obtain a TCO film with both high conductivity and high transmittance, and further used to prepare heterojunction batteries. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes an IO target material suitable for RPD, a preparation method and application thereof, and a heterojunction battery. The IO target material prepared by the present invention has a relative density of 55-65% and can be directly used for RPD coating. During coating, the optimal process window is obtained by adjusting the ratio of H2 atmosphere and O2 atmosphere (O2 / Ar is 11-15%, H2 / Ar is 1.5-1.8%). The deposited TCO film has a film mobility of 153-165m / Vs and a low carrier concentration (1.1-1.3E+20 / cm 3 ), high transmittance (89.5-90.6%), low sheet resistance (25-28Ω / □), can be used in heterojunction battery devices, helping to improve the photoelectric conversion efficiency of the battery.

[0007] A first aspect of the present invention provides a method for preparing an IO target material suitable for RPD.

[0008] Specifically, a method for preparing an IO target suitable for RPD comprises the following steps:

[0009] (1) taking indium oxide powder;

[0010] (2) performing a first grinding on the indium oxide powder, adding a first binder, filtering, and drying to obtain a first mixed powder;

[0011] (3) performing a first molding on the first mixed powder to obtain a first target material blank;

[0012] (4) performing a first degreasing process on the first target material blank and then pre-sintering the blank to obtain the pre-sintered IO blank;

[0013] (5) crushing the pre-sintered 10 green body into powder, performing a second grinding, adding a second binder, filtering, and then drying to obtain the second mixed powder;

[0014] (6) performing a second molding on the second mixed powder to obtain the second target material embryo;

[0015] (7) performing a second degreasing on the second target material blank, and then performing vacuum hot pressing sintering in stages to obtain the IO target material;

[0016] In step (4), the pre-sintering temperature is 1400-1500° C., and / or the pre-sintering time is 8-10 h;

[0017] In step (6), the second molding pressure is 280-320 MPa.

[0018] The present invention is pre-sintered (including a series of processes of grinding, re-molding, and degreasing) to promote the crystallization of the sintered body, reduce the sintering activity of the components, ensure that the sintered body does not shrink during the second vacuum hot pressing sintering, and form a porous medium. If pre-sintering is not performed, the sintered body is more active and shrinks more, forming a dense structure that cannot meet the requirements of the RPD equipment for the target material. Then the present invention is also combined with the vacuum hot pressing sintering method, and the heat is kept in stages, so that the sintered body is heated evenly and the relative density meets the RPD coating requirements. The IO target material provided by the present invention can be used to prepare TCO thin films, and is particularly suitable for preparing TCO thin films by evaporation using the RPD method.

[0019] Preferably, the mass proportion of In2O3 in the IO target is 100%. The present invention provides a target material prepared by using only In2O3 as a metal oxide as a raw material, without doping.

[0020] Preferably, in step (1), the purity of the indium oxide powder is ≥5N, and / or the specific surface area of ​​the indium oxide powder is ≥10m 2 / g, and / or, the particle size D of the indium oxide powder 50 ≤0.2μm, and / or, the D max ≤1μm.

[0021] D max : It indicates the maximum particle size of the powder.

[0022] Preferably, the method for preparing the indium oxide powder comprises first mixing metallic indium, nitric acid and a precipitant, preparing an indium hydroxide precipitate by an aqueous solution co-precipitation method, and then calcining the indium hydroxide precipitate to prepare the indium oxide powder.

[0023] Preferably, the precipitant is aqueous ammonia or ammonium carbonate.

[0024] Preferably, the calcination temperature is 1100-1300° C., and / or the calcination time is 12-18 h.

[0025] Preferably, in step (2), the first grinding adopts specifications of The zirconium bead combination, The mass ratio of the zirconium beads is 3-4:5-6:2-3, and / or the rotation speed of the first grinding is 700-900rpm, and / or the time of the first grinding is 10-20h.

[0026] Preferably, in step (2), the first binder is polyvinyl alcohol and / or polyethylene glycol.

[0027] Preferably, in step (2), the mass of the first binder accounts for 0.4-2.5% of the mass of the indium oxide powder.

[0028] Preferably, in step (2), the drying is spray drying.

[0029] Preferably, in step (2), the specific surface area of ​​the first mixed powder is 15-20 m 2 / g, and / or, the particle size D of the first mixed powder 50 ≤0.1 μm, and / or, D of the first mixed powder max ≤0.5μm, and / or the bulk density of the first mixed powder is 1.80-2.20g / cm 3 , and / or, the moisture content of the first mixed powder is ≤1%.

[0030] Preferably, in step (3), the first molding is wet cold isostatic pressing (WCIP) molding, and / or, in step (6), the second molding is wet cold isostatic pressing (WCIP) molding.

[0031] Preferably, in step (3), the first molding pressure is 100-200 MPa.

[0032] Preferably, in step (4), the temperature of the first degreasing is 600-650° C., and / or the time of the first degreasing is 2-3 h.

[0033] Preferably, in step (4), the heating rate of the pre-sintering is 1°C / min.

[0034] Preferably, in step (4), after the pre-sintering, the temperature is lowered to room temperature at a rate of 2-4°C / min to obtain a pre-sintered IO green body.

[0035] Preferably, in step (5), the powder has a D max ≤20μm.

[0036] Preferably, in step (5), the second grinding adopts specifications of The zirconium bead combination, The mass ratio of the zirconium beads is 3-4:5-6:2-3, and / or the rotation speed of the second grinding is 700-900rpm, and / or the time of the second grinding is 10-20h.

[0037] Preferably, in step (5), the mass of the second binder accounts for 0.4-2.5% of the mass of the powder.

[0038] Preferably, in step (5), the second binder is polyethylene glycol.

[0039] Preferably, in step (5), the drying is spray drying.

[0040] Preferably, in step (5), the specific surface area of ​​the second mixed powder is 20-25 m 2 / g, and / or, the particle size D of the second mixed powder 50 ≤0.2μm, and / or, D of the second mixed powder max ≤1μm, and / or the bulk density of the second mixed powder is 1.80-2.20g / cm 3 , and / or, the moisture content of the second mixed powder is ≤1%.

[0041] Preferably, in step (6), the second molding pressure is 300-320 MPa.

[0042] Preferably, in step (6), the second forming is cold isostatic pressing.

[0043] Preferably, in step (7), the second degreasing step comprises: first evacuating to -80 to -100 Pa, then introducing oxygen until the pressure is 0 Pa, heating the temperature to 600-650°C at a heating rate of 1-3°C / min for degreasing, and keeping the temperature for 2-3h.

[0044] Preferably, in step (7), the staged vacuum hot pressing sintering step comprises:

[0045] First, evacuate to -80-100Pa, and heat up to 900-1000°C at a heating rate of 1°C / min-3°C / min, and keep warm for 7-9h. After the insulation is completed, start pressurizing, the pressure is 5-10Mpa, and heat up to 1100-1300°C at a heating rate of 0.5-2°C / min, and keep warm for 6-8h. After the insulation is completed, heat up to 1500-1550°C at a heating rate of 0.3-1°C / min, and keep warm for 10-12h. After the insulation is completed, cool to room temperature at a rate of 1-3°C / min, and return to normal pressure to obtain the IO target.

[0046] A second aspect of the present invention provides an IO target suitable for RPD.

[0047] An IO target material suitable for RPD, wherein the relative density of the IO target material is 55-65%.

[0048] Preferably, the relative density of the IO target is 58-63%.

[0049] A third aspect of the present invention provides a TCO thin film.

[0050] A TCO film is prepared by using the IO target material.

[0051] A fourth aspect of the present invention provides a method for preparing a TCO thin film.

[0052] A method for preparing a TCO film comprises the following steps:

[0053] The IO target is subjected to reactive plasma deposition to obtain the TCO film, wherein the coating atmosphere includes O2, Ar and H2, the volume ratio of O2 / Ar is 10-16%, and / or the volume ratio of H2 / Ar is 1.3-2.0%.

[0054] Preferably, the volume ratio of O2 / Ar is 11-15%, and / or the volume ratio of H2 / Ar is 1.5-1.8%.

[0055] A fifth aspect of the present invention provides a heterojunction battery.

[0056] A heterojunction battery is made by using the TCO film.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] The present invention first takes indium oxide powder and performs a first grinding, then adds a first binder, filters and dries to obtain a first mixed powder; after a first molding, a first target blank is obtained, and then a first degreasing and pre-sintering at 1400-1500°C for 8-10h are performed to obtain a pre-sintered IO blank, and after crushing, a second grinding is performed again, a second binder is added, and a second mixed powder is obtained after drying, and after a second molding again, a second target blank is obtained, and finally a second degreasing and vacuum hot pressing sintering in stages are performed to obtain an IO target, wherein the pressure of the second molding is 300-350MPa. The present invention promotes the crystallization of the sintered body through pre-sintering, reduces the sintering activity of the components, ensures that the sintered body does not shrink during the second vacuum hot pressing sintering, and forms a porous medium. In addition, the present invention also combines the vacuum hot pressing sintering method, and heat preservation in stages, so that the sintered body is heated evenly, and the relative density meets the RPD coating requirements. The pure IO target prepared by the present invention has a relative density of 55-65% and a suitable density, and can be directly used for RPD coating. During coating, the ratio of H2 atmosphere to O2 atmosphere is adjusted to control O2 / Ar to 11-15% and H2 / Ar to 1.5-1.8%, thereby obtaining an optimal process window. The film mobility of the deposited TCO film reaches 153-165m / Vs, and the carrier concentration is low (1.1-1.3E+20 / cm 3 ), high transmittance (89.5-90.6%), low sheet resistance (25-28Ω / □), can be used in heterojunction battery devices, helping to improve the photoelectric conversion efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the structure of a heterojunction battery prepared using TCO thin film. DETAILED DESCRIPTION

[0060] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0061] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0062] Universal ICO target: wherein the mass ratio of In2O3:CeO2 is 97:3. The preparation method of the universal ICO target is the same as that of Example 2 of the present invention, the only difference being that cerium oxide is also doped into indium oxide.

[0063] Example 1

[0064] A method for preparing an IO target suitable for RPD comprises the following steps:

[0065] (1) Preparation of IO powder:

[0066] The aqueous solution co-precipitation method was used to precipitate indium hydroxide using 5N metallic indium as the raw material, nitric acid, and ammonia water as the precipitant. The precipitated indium hydroxide was calcined at a high temperature of 1250°C for 16 hours to generate high-purity indium oxide powder. The purity of the indium oxide powder was measured to be 5N, and the specific surface area was 15.6m 2 / g, particle size D 50 0.14μm, D max It is 0.8μm.

[0067] (2) First grinding and granulation:

[0068] The indium oxide powder prepared above was ball-milled and ground for use The zirconium beads of three specifications were matched, the mass ratio of zirconium beads was 3:5:2, the rotation speed was 800rpm, the grinding time was 15h, and polyvinyl alcohol (binder) was added and stirred and filtered. The mass of the binder accounted for 2.2% of the total mass of indium oxide powder. Then, the mixed powder was obtained after spray drying, and the specific surface area of ​​the mixed powder was measured to be 18.5m 2 / g, particle size D 50 0.08μm, D max The diameter is 0.35 μm and the bulk density is 2.15 g / cm 3 , moisture content 0.35%.

[0069] (3) First embryo forming:

[0070] The mixed powder prepared above was injected into a mold and molded using WCIP at a molding pressure of 180 MPa to obtain a first target material blank.

[0071] (4) First degreasing and pre-sintering:

[0072] The first target blank was degreased at a temperature of 650°C for 2 hours. After degreasing, the temperature was raised to 1450°C at a rate of 1°C / min for pre-sintering, and the temperature was kept at that temperature for 8 hours. After the temperature was kept at that temperature, the temperature was lowered to room temperature at a rate of 3°C / min to obtain a pre-sintered IO blank.

[0073] (5) Crushing and secondary grinding:

[0074] The pre-sintered 10 green body is put into a crusher and crushed into powder with a particle size of D max The crushed powder is ground twice and then used for grinding. The zirconium beads of the three specifications were matched, the mass ratio of the three specifications of zirconium beads was 3:5:2, the rotation speed was 800rpm, the grinding time was 15h, and IO powder was obtained. After adding polyethylene glycol (binder), it was stirred and filtered, wherein the mass of the binder accounted for 0.5% of the total mass of the IO powder. After spray drying, the second mixed powder was obtained, and the specific surface area value of the second mixed powder was measured to be 23.5m 2 / g, particle size D 50 0.1μm, D max The particle size is 0.8 μm and the bulk density is 2.06 g / cm 3 , moisture content 0.30%.

[0075] (6) Second blank forming:

[0076] The second mixed powder is placed in a specific graphite mold with the following specifications: The second target blank was obtained by WCIP molding with a molding pressure of 300 MPa and cold isostatic pressing strengthening.

[0077] (7) Vacuum hot pressing sintering in stages:

[0078] Place the second target blank into the hot pressing sintering furnace and evacuate to -90Pa. After the pressure stabilizes, introduce oxygen to a pressure of 0Pa. Degrease at a heating rate of 1.5℃ / min to 650℃, and keep warm for 2.5h. After degreasing, evacuate to -90Pa in vacuum, and heat up to 950℃ at a heating rate of 1.5℃ / min, and keep warm for 8h. After the insulation is completed, start pressurization, the pressure is 10Mpa, and the heating rate is increased to 1200℃ at a heating rate of 0.5℃ / min, and the insulation time is 6h. After the insulation is completed, heat up to 1500℃ at a heating rate of 0.3℃ / min, and the insulation time is 10h. After the insulation is completed, cool to room temperature at a rate of 3℃ / min, and return to normal pressure to obtain an IO target.

[0079] Example 2

[0080] A method for preparing an IO target material suitable for RPD, which differs from Example 1 in that the second molding pressure is 320 MPa.

[0081] Example 3

[0082] A method for preparing an IO target suitable for RPD, which differs from Example 2 in that in step (4), the pre-sintering temperature is 1480°C.

[0083] Example 4

[0084] A method for preparing an IO target suitable for RPD, which differs from Example 2 in that in step (4), the pre-sintering temperature is 1420°C.

[0085] Comparative Example 1

[0086] A method for preparing an IO target material, which differs from Example 1 in that the pressure of the second molding is increased to 350°C.

[0087] Comparative Example 2

[0088] A method for preparing an IO target material, which differs from Example 2 in that the pre-sintering temperature is increased to 1550°C.

[0089] Comparative Example 3

[0090] A method for preparing an IO target material, which differs from Example 2 in that the pre-sintering temperature is reduced to 1380°C.

[0091] Comparative Example 4

[0092] A method for preparing an IO target material, which differs from Example 1 in that no pre-sintering is performed in step (4).

[0093] Comparative Example 5

[0094] A method for preparing an IO target material, which differs from Example 2 in that the vacuum hot pressing sintering in step (7) is not carried out in stages, but is directly raised to 1450° C., as follows:

[0095] Place the second target blank into a hot pressing sintering furnace and evacuate to -90Pa. After the pressure stabilizes, introduce oxygen to 0Pa. Heat up to 650℃ at a rate of 1.5℃ / min for degreasing, and keep warm for 2.5h. After degreasing, evacuate to -90Pa, directly increase to 1450℃, and keep warm for 26.5h. Cool down to room temperature and return to normal pressure to obtain IO target.

[0096] Product effect testing

[0097] 1. Performance of IO target

[0098] (1) Test method

[0099] Relative density: First measure the density of the sintered body, and then calculate it according to the following formula ①:

[0100] The density of sintered bodies is measured by the wax sealing method, which is based on Archimedes' principle. Specifically, the sintered body is immersed in melted paraffin wax to form a wax shell on the surface of the sample. The mass of the sintered body with the wax shell in air and water is measured respectively. The volume of the sample is calculated based on the buoyancy principle, and then the density of the sintered body is calculated.

[0101] Relative density = sintered body test density / indium oxide theoretical density × 100% formula ①.

[0102] (2) Test results

[0103] The relative density test results of the IO targets prepared in the above embodiments and comparative examples are shown in the following table.

[0104] Table 1 Key process parameters of each embodiment and comparative example and performance test results of IO target

[0105] Second molding pressure (MPa) Pre-sintering temperature (℃) Relative density (%) Example 1 300 1450 60.50％ Example 2 320 1450 60.00％ Example 3 320 1480 60.30％ Example 4 320 1420 59.80％ Comparative Example 1 350 - Body cracking Comparative Example 2 300 1550 75.60％ Comparative Example 3 300 1380 45.80％ Comparative Example 4 320 - 90.42％ Comparative Example 5 320 1450 46.50％

[0106] It can be seen from the above table that the relative density of the IO target materials prepared in Examples 1-4 of the present invention is 59.80-60.50%, and the density is appropriate, neither too dense nor too loose, and can be well used for subsequent RPD coating.

[0107] However, in Comparative Example 1, the second molding pressure is too high, and the blank cracks directly. The pre-sintering temperature of Comparative Example 2 is too high, resulting in a high relative density of the target material obtained, which is too dense and difficult to sublimate, and cannot be used for RPD coating. The pre-sintering temperature of Comparative Example 3 is too low, resulting in a low relative density of the target material obtained, which is too loose, resulting in serious surface powder loss. When further used for coating deposition, it is very easy to generate dust under the influence of the gas field and heating, which pollutes the reaction chamber and the target material chamber, seriously affecting the normal operation of the coating process. Comparative Example 4 did not undergo pre-sintering, resulting in excessive sintering activity of the sintered body, large shrinkage, and a high relative density of the target material, which cannot meet the RPD coating requirements. Comparative Example 5 was directly heated to 1450°C without staged insulation, resulting in uneven heating of the sintered body and a low relative density, which did not meet the RPD coating requirements.

[0108] The IO targets prepared in Examples 1-4 of the present invention were further used to prepare TCO thin films by RPD coating. However, the targets prepared in Comparative Examples 1-5 had poor performance and were difficult to be used for RPD coating.

[0109] 2. RPD coating test

[0110] (1) Test method

[0111] RPD coating was performed using the target materials of Examples 1-4 and IO respectively, and the coating atmosphere was changed to obtain a TCO film. The specific method is as follows:

[0112] The IO target prepared in the above embodiments is placed in the RPD coating equipment to deposit a TCO film on a glass sheet, wherein the coating atmosphere contains three gases: Ar, O2, and H2 (during coating, three pipelines are respectively pure Ar gas, pure O2 gas, and H2 / Ar mixed gas, which are respectively passed through a flow meter, mixed, and introduced into the reaction chamber together. Among them, H2 is flammable and explosive, so it is often mixed with Ar to dilute the concentration and used as a mixed gas), the electron gun current intensity is 150A, the deposition temperature is 100°C, and the film thickness is 100nm. Then use a Hall effect tester to test the film mobility and carrier concentration, use an ultraviolet spectrophotometer to test the film transmittance, and use a four-probe to test the film square resistance. Use different atmospheres for coating to test the effect of the coating atmosphere on the photoelectric properties of the TCO film.

[0113] The relationship between film resistivity, free carrier concentration and mobility is ρ = 1 / qNμ, where ρ is resistivity, q is the electron charge, N is the free carrier concentration, and μ is the carrier mobility. It can be seen from the above formula that increasing the carrier concentration and improving the mobility can achieve low resistivity.

[0114] (2) Test results

[0115] Table 2 Performance test results of TCO films obtained by RPD coating using various embodiments and IO targets

[0116]

[0117] Note: In the table, O2 / Ar represents the ratio of O2 flow rate to Ar flow rate during coating, and H2 / Ar represents the ratio of H2 flow rate to Ar flow rate during coating. Thin film sheet resistance, unit is ohm / square, i.e. Ω / □.

[0118] As can be seen from the table above, the IO targets provided in Examples 1-4 of the present invention adopt RPD and change different coating atmospheres to prepare TCO films 1-8 with film mobility of 153-165 m / Vs and carrier concentration of 1.1-1.3E+20 / cm 3 , the sheet resistance is 25-28Ω / □, and the transmittance is 89.5-90.6%. It has the advantages of high film mobility, low carrier concentration, low sheet resistance and high transmittance.

[0119] The TCO film 9 uses a general ICO target material. The results show that its film mobility is lower than that of the TCO film 2, and the carrier concentration is high, and the comprehensive photoelectric performance of the film is poor.

[0120] The TCO film 10 was prepared without hydrogen flow, so the film crystallization effect was poor, the mobility was low, and the sheet resistance was high.

[0121] The hydrogen ratio during the preparation of the TCO film 11 is too low, which also cannot significantly improve the conductivity of the film.

[0122] When the TCO film 12 is prepared, the amount of hydrogen is too much, resulting in more oxygen defects inside the film and too high carrier concentration, which affects the transmittance of the film.

[0123] When the TCO film 13 is prepared, the oxygen ratio is too low, resulting in low film mobility and excessively high carrier concentration, which affects the transmittance of the film.

[0124] Based on the above results, it is shown that when the IO targets of Examples 1-4 are RPD coated, when the coating atmosphere O2 / Ar is 11-15% and H2 / Ar is 1.5-1.8%, the mobility, carrier concentration and transmittance of the prepared TCO films 1-8 are significantly improved.

[0125] 3. Efficiency test of heterojunction cells

[0126] (1) Test method

[0127] The IO targets of Examples 1-3 and Comparative Example 1 were deposited using RPD coating equipment for coating tests. First, a TCO film was deposited on a double-sided microcrystalline film silicon wafer, and a low-temperature silver paste was screen-printed. After curing at a temperature of 200° C. for 30 minutes, a heterojunction cell was made (the schematic diagram of the heterojunction cell structure is shown in FIG. Figure 1 As shown in the figure, they are TCO film, n-type doped amorphous silicon, n-type intrinsic amorphous silicon, N-type monocrystalline silicon, p-type intrinsic amorphous silicon, p-type doped amorphous silicon, and TCO film, respectively). Then, the photoelectric conversion efficiency of the heterojunction cell was tested using a Halm tester under standard light intensity.

[0128] (2) Test results

[0129] Table 3 Performance test results of heterojunction cells made from TCO films made from Examples 1-3 and general ICO targets (O2 / Ar=12%, H2 / Ar=1.5%)

[0130]

[0131] Note: In the table, Eta, Voc, Isc, FF, Rs, and Rsh are the cell conversion efficiency, open circuit voltage, short circuit current, fill factor, series resistance, and parallel resistance, respectively. The TCO film prepared by the general ICO and then the heterojunction cell further prepared are used as the benchmark (so the value is 0), and the difference between the test values ​​of various parameters of Examples 1-3 and the test values ​​of various parameters of the general ICO is calculated and recorded in Table 3 (positive values ​​are higher than the benchmark, and negative values ​​are lower than the benchmark).

[0132] It can be seen from the above table that for the TCO thin films made from the IO target materials of Examples 1-3 of the present invention, after the film mobility increases, the battery fill factor increases, and the carrier concentration decreases, which can improve the transmittance of the film, increase the short-circuit current of the battery cell by 18-25mA, and improve the overall photoelectric conversion efficiency by about 0.05%.

Claims

1. A method for preparing an IO target, characterized in that: The steps include: (1) taking indium oxide powder; (2) performing a first grinding on the indium oxide powder, adding a first binder, filtering, and drying to obtain a first mixed powder; (3) performing a first molding on the first mixed powder to obtain a first target material blank; (4) performing a first degreasing process on the first target material blank and then pre-sintering the blank to obtain the pre-sintered IO blank; (5) crushing the pre-sintered 10 green body into powder, performing a second grinding, adding a second binder, filtering, and then drying to obtain the second mixed powder; (6) performing a second molding on the second mixed powder to obtain the second target material embryo; (7) performing a second degreasing on the second target material blank, and then performing vacuum hot pressing sintering in stages to obtain the IO target material; In step (4), the pre-sintering temperature is 1400-1500° C., and / or the pre-sintering time is 8-10 h; In step (6), the second molding pressure is 280-320 MPa.

2. The preparation method according to claim 1, characterized in that: In step (3), the first molding pressure is 100-200 MPa.

3. The preparation method according to claim 1, characterized in that: In step (3), the first forming is wet cold isostatic pressing, and / or, in step (6), the second forming is wet cold isostatic pressing.

4. The preparation method according to claim 1, characterized in that: In step (4), the temperature of the first degreasing is 600-650° C., and / or the time of the first degreasing is 2-3 hours.

5. The preparation method according to claim 1, characterized in that: In step (7), the second degreasing step includes: first evacuating to -80 to -100 Pa, then introducing oxygen until the pressure is 0 Pa, heating the temperature to 600-650°C at a heating rate of 1-3°C / min for degreasing, and keeping the temperature for 2-3h.

6. The preparation method according to claim 1, characterized in that: In step (7), the staged vacuum hot pressing sintering steps include: First, evacuate to -80-100Pa, and heat up to 900-1000°C at a heating rate of 1-3°C / min, and keep warm for 7-9h. After the insulation is completed, start pressurizing, the pressure is 5-10Mpa, and heat up to 1100-1300°C at a heating rate of 0.5-2°C / min, and keep warm for 6-8h. After the insulation is completed, heat up to 1500-1550°C at a heating rate of 0.3-1°C / min, and keep warm for 10-12h. After the insulation is completed, cool to room temperature at a rate of 1-3°C / min, and return to normal pressure to obtain the IO target.

7. An IO target material, characterized in that: The IO target is prepared by the preparation method according to any one of claims 1 to 6, and has a relative density of 55-65%.

8. A TCO film, characterized in that: It is made by using the IO target material described in claim 7.

9. The method for preparing the TCO thin film according to claim 8, characterized in that: The steps include: The IO target is subjected to reactive plasma deposition to obtain the TCO film, wherein the coating atmosphere includes O2, Ar and H2, the volume ratio of O2 / Ar is 10-16%, and / or the volume ratio of H2 / Ar is 1.3-2.0%.

10. A heterojunction battery, characterized in that: It is prepared by using the TCO film described in claim 8.

Images