IO target material suitable for RPD, and preparation method and application thereof, and heterojunction cell

Abstract

This invention belongs to the field of photovoltaic cell technology, and provides an IO target material suitable for RPD, its preparation method and application, and heterojunction cells. The invention first grinds indium oxide powder, then adds a first binder to obtain a first mixed powder. After a first molding and static pressing, a first target material preform is obtained. This preform is then degreased and pre-sintered at 1400-1500℃ for 8-10 hours to obtain a pre-sintered IO preform. After pulverization, it is ground again, a second binder is added, and after drying, a second mixed powder is obtained. This preform is then shaped and statically pressed again to obtain a second target material preform. Finally, it undergoes degreasing and staged vacuum hot pressing sintering to obtain the IO target material. The pure IO target material obtained by this invention has a relative density of about 60% and can be directly used for RPD coating. The deposited TCO thin film has low carrier concentration, high mobility, and high transmittance, which helps improve the photoelectric conversion efficiency of the cell when used in heterojunction cell devices.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and more specifically, to an IO target material suitable for RPD, its preparation method and application, and heterojunction cells. Background Technology

[0002] Heterojunction solar cells, formed by depositing intrinsic amorphous silicon thin films and doped amorphous (micro)crystalline silicon thin films on both sides of an N-type silicon substrate, exhibit excellent passivation and high cell conversion efficiency. However, due to the poor lateral conductivity of amorphous silicon thin films, a transparent conductive oxide thin film (TCO film) needs to be deposited on the outer side of the film as a conductive and light-transmitting layer. Methods for preparing TCO films include magnetron sputtering (PVD) and reactive plasma deposition (RPD).

[0003] The basic principle of PVD is: under the influence of electric and magnetic fields, the process gas Ar is ionized into Ar. + Ions, accelerated high-energy particles (Ar) + High-energy electron beams are used to bombard a target, causing atoms on the target surface to escape from the original crystal lattice. The sputtered particles are deposited on the substrate surface and react with oxygen atoms to form oxides. In contrast, RPD (Reactive Particle Deposition) is a process that uses an electron gun to emit an electron beam to vaporize the target under vacuum conditions. The vaporized particles then fly to the substrate surface and condense to form a film.

[0004] Magnetron sputtering (PVD) deposition of TCO thin films suffers from high-energy particle bombardment of the substrate surface, causing performance damage and affecting film properties. Compared to PVD, reverse polarization (RPD) causes less surface damage to the substrate and operates at a lower deposition temperature, resulting in TCO films with superior performance. Commonly used raw materials for RPD deposition are cerium oxide-doped indium oxide (ICO) and tungsten oxide-doped indium oxide (IWO). Both materials are based on indium oxide and produce films with high mobility (100-120 cm⁻¹). 2 While the conductivity is high ( / VS), there is still room for improvement in mobility. Furthermore, after indium oxide is doped, if the dopant elements do not integrate into the crystal lattice during film formation, they easily become recombination centers, affecting grain boundary scattering of charge carriers. Parasitic absorption of light by the dopant particles reduces the film's transmittance, thus making it impossible to simultaneously achieve high conductivity and high transmittance. For example, Chinese patent (publication number CN114242805A) discloses a stacked TCO thin film, a silicon heterojunction solar cell, and its fabrication method, which uses RPD to deposit ICO or IWO thin films with a mobility of 80-100 cm⁻¹. 2 / VS, but this method uses multi-doped oxide targets, which require micro-doping based on indium oxide. If the mixing is not uniform, it may lead to 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 TCO thin films with both high conductivity and high transmittance, and further used to prepare heterojunction solar cells. Summary of the Invention

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

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

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

[0009] (1) Take indium oxide powder;

[0010] (2) The indium oxide powder is first ground, then a first binder is added, filtered, and then dried to obtain a first mixed powder;

[0011] (3) The first mixed powder is subjected to a first molding process to obtain a first target material preform;

[0012] (4) The first target material blank is first degreased and then pre-sintered to obtain the pre-sintered IO blank;

[0013] (5) The pre-fired IO blank is crushed into powder, then subjected to a second grinding, then a second binder is added, filtered, and then dried to obtain the second mixed powder;

[0014] (6) The second mixed powder is subjected to a second molding process to obtain the second target material preform;

[0015] (7) The second target material blank is subjected to a second degreasing, and then subjected to staged vacuum hot pressing sintering to obtain the IO target material;

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

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

[0018] This invention employs pre-sintering (including a series of processes such as grinding, shaping, and degreasing) to promote crystallization of the sintered body, reduce the sintering activity of components, ensure that the sintered body does not shrink during the second vacuum hot pressing sintering, and form a porous medium. Without pre-sintering, the sintered body has high activity, shrinks significantly, and forms a dense structure, which cannot meet the target material requirements of RPD equipment. Furthermore, this invention combines vacuum hot pressing sintering with staged heat preservation to ensure uniform heating of the sintered body and achieve the relative density required for RPD coating. The IO target material provided by this invention can be used to prepare TCO thin films, and is particularly suitable for preparing TCO thin films using RPD evaporation.

[0019] Preferably, the In2O3 content in the IO target is 100% by mass. This invention provides a target material made solely using In2O3 as a metal oxide as a raw material, without any 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 ≥10m². 2 / g, and / or, the particle size D of the indium oxide powder 50 ≤0.2μm, and / or, the D of the indium oxide powder max ≤1μm.

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

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

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

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

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

[0026] Preferably, in step (2), the first adhesive 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 m². 2 / g, and / or, the particle size D of the first mixed powder 50 ≤0.1μm, and / or, the D of the first mixed powder max ≤0.5μm, and / or, the loose packing density of the first mixed powder is 1.80-2.20 g / cm³. 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 pressure of the first molding is 100-200 MPa.

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

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

[0034] Preferably, in step (4), after the pre-sintering, the temperature is reduced to room temperature at a rate of 2-4℃ / min to obtain a pre-sintered IO blank.

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

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

[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 adhesive 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 m². 2 / g, and / or, the particle size D of the second mixed powder 50 ≤0.2μm, and / or, the D of the second mixed powder max ≤1μm, and / or, the loose packing density of the second mixed powder is 1.80-2.20 g / cm³. 3 And / or, the moisture content of the second mixed powder is ≤1%.

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

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

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

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

[0045] First, evacuate to -80 to -100 Pa, then raise the temperature to 900-1000℃ at a rate of 1℃ / min to 3℃ / min and hold for 7-9 hours. After holding, pressurize to 5-10 MPa and raise the temperature to 1100-1300℃ at a rate of 0.5-2℃ / min, holding for 6-8 hours. After holding, raise the temperature to 1500-1550℃ at a rate of 0.3-1℃ / min and hold for 10-12 hours. After holding, cool to room temperature at a rate of 1-3℃ / min and restore to atmospheric pressure to obtain the IO target material.

[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 IO target material has a relative density of 55-65%.

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

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

[0050] A TCO thin film is prepared using the aforementioned 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 thin film includes the following steps:

[0053] The TCO thin film is prepared by reactive plasma deposition of the IO target, wherein the deposition 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 fabricated using the aforementioned TCO thin film.

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

[0058] This invention first grinds indium oxide powder, then adds a first binder, filters, and dries to obtain a first mixed powder. After a first molding process, a first target blank is obtained. This blank is then degreased and pre-sintered at 1400-1500℃ for 8-10 hours to obtain a pre-sintered IO blank. After pulverization, it undergoes a second grinding process, adds a second binder, and dries to obtain a second mixed powder. This is followed by a second molding process to obtain a second target blank. Finally, a second degreasing and staged vacuum hot pressing sintering are performed to obtain the IO target. The pressure of the second molding is 300-350 MPa. Pre-sintering promotes crystallization of the sintered body, 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. Furthermore, this invention combines vacuum hot pressing sintering with staged heat preservation, ensuring uniform heating of the sintered body and achieving the relative density required for RPD coating. The pure IO target material prepared by this invention has a relative density of 55-65%, which is suitable for direct use in RPD coating. During coating, by adjusting the ratio of H2 atmosphere to O2 atmosphere, controlling O2 / Ar to 11-15% and H2 / Ar to 1.5-1.8%, the optimal process window is obtained. The deposited TCO film achieves a film mobility of 153-165 m / Vs and a low carrier concentration (1.1-1.3E+20 / cm). 3 It has high light transmittance (89.5-90.6%) and low sheet resistance (25-28Ω / □), and can be used in heterojunction solar cell devices to help improve the photoelectric conversion efficiency of the cells. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of a heterojunction solar cell fabricated using a TCO thin film. Detailed Implementation

[0060] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

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

[0062] General ICO target material: The mass ratio of In2O3 to CeO2 is 97:3. The preparation method of the general ICO target material is the same as that in Example 2 of this invention, except that cerium oxide is also doped into indium oxide.

[0063] Example 1

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

[0065] (1) Preparation of IO powder:

[0066] Indium hydroxide was precipitated using an aqueous co-precipitation method with 5N metallic indium as the raw material. Nitric acid was added, and ammonia was used as the precipitant. The precipitated indium hydroxide was then calcined at 1250℃ for 16 hours to produce high-purity indium oxide powder. The purity of the indium oxide powder was measured to be 5N, and its specific surface area was 15.6 m² / s. 2 / g, particle size D 50 It is 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 used. Zirconium beads of three different sizes were used in a mass ratio of 3:5:2. The grinding process was carried out at 800 rpm for 15 hours, followed by the addition of polyvinyl alcohol (a binder) and subsequent stirring and filtration. The binder accounted for 2.2% of the total mass of the indium oxide powder. The mixture was then spray-dried to obtain a mixed powder, with a measured specific surface area of ​​18.5 m². 2 / g, particle size D 50 It is 0.08μm, D max Its particle size is 0.35 μm, and its loose packing density is 2.15 g / cm³. 3 Moisture content: 0.35%.

[0069] (3) First embryo formation:

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

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

[0072] The first target material blank was degreased at 650℃ for 2 hours. After degreasing, the temperature was increased to 1450℃ at a rate of 1℃ / min for pre-sintering for 8 hours. After pre-sintering, the temperature was reduced to room temperature at a rate of 3℃ / min to obtain the pre-sintered IO blank.

[0073] (5) Crushing and secondary grinding:

[0074] The pre-fired IO blank is placed in a crusher and crushed into powder with a particle size D. max The particle size is 18.5 μm. The crushed powder is then subjected to secondary grinding, using grinding... Zirconium beads of three different sizes were mixed in a mass ratio of 3:5:2, ground at 800 rpm for 15 hours to obtain IO powder. Polyethylene glycol (a binder) was added, and the mixture was stirred and filtered. The binder accounted for 0.5% of the total mass of the IO powder. After spray drying, a second mixed powder was obtained, with a measured specific surface area of ​​23.5 m². 2 / g, particle size D 50 0.1μm, D max Its thickness is 0.8 μm, and its loose packing density is 2.06 g / cm³. 3 Moisture content: 0.30%.

[0075] (6) Forming the second green blank:

[0076] The second mixed powder is placed into a specific graphite mold, the mold specifications being... The second target blank was obtained by WCIP molding at a molding pressure of 300 MPa and cold isostatic pressing.

[0077] (7) Staged vacuum hot pressing sintering:

[0078] The second target blank was placed in a hot-pressing sintering furnace and evacuated to -90 Pa. After the pressure stabilized, oxygen was introduced until the pressure reached 0 Pa. The temperature was raised to 650 °C at a rate of 1.5 °C / min for degreasing, and held for 2.5 h. After degreasing, the temperature was evacuated to -90 Pa, and the temperature was raised to 950 °C at a rate of 1.5 °C / min, and held for 8 h. After holding, the temperature was increased to 10 MPa, and the temperature was raised to 1200 °C at a rate of 0.5 °C / min, and held for 6 h. After holding, the temperature was raised to 1500 °C at a rate of 0.3 °C / min, and held for 10 h. After holding, the temperature was lowered to room temperature at a rate of 3 °C / min and then restored to atmospheric pressure to obtain the IO target.

[0079] Example 2

[0080] A method for preparing an IO target suitable for RPD 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 differs from Example 2 in that, in step (4), the pre-sintering temperature is 1480℃.

[0083] Example 4

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

[0085] Comparative Example 1

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

[0087] Comparative Example 2

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

[0089] Comparative Example 3

[0090] The method for preparing an IO target 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 differs from Example 1 in that step (4) does not involve pre-sintering.

[0093] Comparative Example 5

[0094] A method for preparing an IO target material differs from Example 2 in that the vacuum hot pressing sintering in step (7) does not involve staged heat preservation, but instead directly raises the temperature to 1450°C, as detailed below:

[0095] The second target blank was placed in a hot-pressing sintering furnace and evacuated to -90 Pa. After the pressure stabilized, oxygen was introduced until the pressure reached 0 Pa. The temperature was increased to 650 °C at a rate of 1.5 °C / min for degreasing, and held at that temperature for 2.5 h. After degreasing, the temperature was evacuated to -90 Pa, and the temperature was directly increased to 1450 °C and held for 26.5 h. The temperature was then reduced to room temperature and restored to atmospheric pressure to obtain the IO target material.

[0096] Product effectiveness test

[0097] 1. Performance of IO sputtering targets

[0098] (1) Test method

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

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

[0101] Relative density = (tested density of sintered body / theoretical density of indium oxide) × 100% Equation 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 table below.

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

[0105] Second molding pressure (MPa) Pre-sintering temperature (°C) 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 - billet 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] As shown in the table above, the relative density of the IO target material prepared in Examples 1-4 of the present invention is 59.80-60.50%, which is a suitable density, neither too dense nor too loose, and can be well used for subsequent RPD coating.

[0107] In Comparative Example 1, the second forming pressure was too high, causing the preform to crack directly. In Comparative Example 2, the pre-sintering temperature was too high, resulting in a target material with a high relative density, making it too dense and difficult to sublimate, thus unsuitable for RPD coating. In Comparative Example 3, the pre-sintering temperature was too low, resulting in a target material with a low relative density, making it too porous and causing severe surface powder shedding. During further coating deposition, under the influence of the gas field and heating, dust was easily generated, contaminating the reaction chamber and target chamber, severely affecting the normal operation of the coating process. In Comparative Example 4, no pre-sintering was performed, resulting in a sintered body with excessive sintering activity, large shrinkage, and a high target material relative density, failing to meet the requirements for RPD coating. In Comparative Example 5, the temperature was directly raised to 1450℃ without staged heat preservation, resulting in uneven heating of the sintered body, a low relative density, and failure to meet the requirements for RPD coating.

[0108] Furthermore, the IO targets obtained in Examples 1-4 of this invention were used to prepare TCO thin films via RPD deposition. However, the targets obtained in Comparative Examples 1-5 had poor performance and were difficult to use for RPD deposition.

[0109] 2. RPD coating test

[0110] (1) Test method

[0111] RPD deposition was performed using targets from Examples 1-4 and IO, respectively, with variations in the deposition atmosphere, to obtain TCO thin films. The specific methods are as follows:

[0112] The IO targets prepared in the above embodiments were placed in an RPD coating apparatus to deposit TCO thin films on a glass slide. The coating atmosphere contained three gases: Ar, O2, and H2 (during coating, three pipelines respectively provided pure Ar, pure O2, and an H2 / Ar mixture, which were then mixed and introduced into the reaction chamber after passing through flow meters. H2, being flammable and explosive, was often diluted with Ar to create a mixed gas). The electron gun current intensity was 150 A, the deposition temperature was 100 °C, and the film thickness was 100 nm. The film mobility and carrier concentration were then measured using a Hall effect meter, the transmittance was measured using a UV spectrophotometer, and the sheet resistance was measured using a four-probe method. Different atmospheres were used for coating to test the effect of the coating atmosphere on the photoelectric properties of the TCO thin film.

[0113] The relationship between thin film resistivity, free carrier concentration, and mobility is given by ρ = 1 / qNμ, where ρ is resistivity, q is electron charge, N is free carrier concentration, and μ is carrier mobility. It can be seen from this equation that increasing carrier concentration and improving mobility can result in lower resistivity.

[0114] (2) Test Results

[0115] Table 2. Performance test results of TCO thin films prepared by RPD deposition 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 is expressed in ohms per square, i.e., Ω / □.

[0118] As shown in the table above, the IO targets provided in Examples 1-4 of this invention, using RPD, and by changing different coating atmospheres, resulted in TCO films 1-8 with film mobilities of 153-165 m / Vs and carrier concentrations of 1.1-1.3E+20 / cm². 3 With a sheet resistance of 25-28 Ω / □ and a transmittance of 89.5-90.6%, it has the advantages of high film mobility, low carrier concentration, low sheet resistance, and high transmittance.

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

[0120] During the preparation of TCO thin film 10, no hydrogen gas was introduced, resulting in poor film crystallization, low mobility, and high sheet resistance.

[0121] The low hydrogen content during the preparation of TCO film 11 also prevents a significant improvement in the film's conductivity.

[0122] Excessive hydrogen content during the preparation of TCO film 12 resulted in numerous oxygen defects inside the film, leading to an excessively high carrier concentration and affecting the film's transmittance.

[0123] The low oxygen ratio during the preparation of TCO film 13 resulted in low film mobility and excessively high carrier concentration, which affected the film's transmittance.

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

[0125] 3. Efficiency testing of heterojunction solar cells

[0126] (1) Test method

[0127] The IO targets of Examples 1-3 and Comparative Example 1 were deposited using an RPD coating equipment for coating tests. First, a TCO film was deposited on a double-sided microcrystalline thin film silicon wafer, and a low-temperature silver paste was screen-printed. After curing at 200°C for 30 minutes, a heterojunction solar cell was fabricated (the schematic diagram of the fabricated heterojunction solar cell structure is shown in Figure 1). Figure 1 As shown, the structures are, in order: TCO thin 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 thin film. The photoelectric conversion efficiency of the heterojunction solar cell was then tested using a Halmmeter under standard light intensity.

[0128] (2) Test Results

[0129] Table 3 shows the performance test results of heterojunction solar cells prepared using TCO thin films 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 represent, in order, the battery conversion efficiency, open-circuit voltage, short-circuit current, fill factor, series resistance, and parallel resistance. Using the heterojunction solar cell further prepared from the TCO thin film obtained by the general ICO as a baseline (hence the value is 0), the differences between the test values ​​of each parameter in Examples 1-3 and the test values ​​of each parameter in the general ICO are calculated and recorded in Table 3 (positive values ​​indicate higher values ​​than the baseline, negative values ​​indicate lower values ​​than the baseline).

[0132] As shown in the table above, the TCO films prepared by the IO target materials in Examples 1-3 of this invention have increased cell fill factor and decreased carrier concentration after the film mobility increases, which can improve the film transmittance, increase the cell short-circuit current 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, Includes the following steps: (1) Take indium oxide powder; (2) The indium oxide powder is first ground, then a first binder is added, filtered, and then dried to obtain a first mixed powder; (3) The first mixed powder is subjected to a first molding process to obtain a first target blank; (4) The first target material blank is first degreased and then pre-sintered to obtain the pre-sintered IO blank; (5) The pre-fired IO blank is crushed into powder, then subjected to a second grinding, then a second binder is added, filtered, and then dried to obtain the second mixed powder; (6) The second mixed powder is subjected to a second molding process to obtain the second target material blank; (7) The second target material blank is subjected to a second degreasing, and then subjected to staged vacuum hot pressing sintering to obtain the IO target material; The staged vacuum hot pressing sintering steps include: First, evacuate to -80~-100Pa, then raise the temperature to 900-1000℃ at a rate of 1-3℃ / min and hold for 7-9 hours. After holding, pressurize to 5-10 MPa and raise the temperature to 1100-1300℃ at a rate of 0.5-2℃ / min, holding for 6-8 hours. After holding, raise the temperature to 1500-1550℃ at a rate of 0.3-1℃ / min, holding for 10-12 hours. After holding, cool to room temperature at a rate of 1-3℃ / min and restore to atmospheric pressure to obtain the IO target material. The In2O3 content in the IO target is 100% by mass; In step (4), the pre-sintering temperature is 1400-1500℃, and / or the pre-sintering time is 8-10h; In step (6), the pressure of the second molding is 280-320 MPa.

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

3. The preparation method according to claim 1, characterized in that, In step (3), the first molding is wet cold isostatic pressing, and / or, in step (6), the second molding 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℃, and / or the time of the first degreasing is 2-3h.

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

6. An Io target, characterized in that, The IO target is prepared by the preparation method according to any one of claims 1-5, wherein the IO target has a relative density of 55-65%.

7. A TCO thin film, characterized in that, It is prepared using the IO target material described in claim 6.

8. The method for preparing the TCO thin film according to claim 7, characterized in that, Includes the following steps: The TCO thin film is prepared by reactive plasma deposition of the IO target material, wherein the deposition 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%.

9. A heterojunction battery, characterized in that, The TCO film described in claim 7 was used to prepare the film.

Images