Target material for thin-film solar cell as well as preparation method and application of target material

Abstract

The invention discloses a target material for a thin-film solar cell and a preparation method and application thereof, and the preparation method comprises the following steps: weighing a binary copper-selenium compound as a raw material according to the stoichiometric value of Cu < 2 + > aSe < 3 + > b (-1 < = a < = 0.5,-2 < = b < = 0.5); performing pretreatment to obtain pretreated powder; the pretreated powder is subjected to hot pressing sintering treatment under the inert atmosphere, the sintering temperature of hot pressing sintering treatment ranges from 600 DEG C to 850 DEG C, the sintering pressure ranges from 20 MPa to 50 MPa, the sintering time ranges from 1 h to 5 h, and the copper-selenium target material is obtained; the binary copper selenium compound is selected from one or more of cuprous selenide, tricopper diselenide, copper selenide and copper diselenide. By accurately controlling the stoichiometric ratio of the elements, the copper-selenium target material with controllable components can be prepared, meanwhile, the preparation process is simple, the preparation cost is low, large-scale process production is facilitated, in addition, the density of the obtained copper-selenium target material is larger than 95%, and high uniformity and high density of the copper-selenium target material can be achieved at the same time.

Description

Technical Field

[0001] This application belongs to the field of thin-film solar cell technology, specifically relating to a target material for thin-film solar cells, its preparation method, and its application. Background Technology

[0002] Copper indium gallium selenide (CuInGaSe-CIGS) thin-film solar cells, as a type of high-efficiency photovoltaic device, have become a focus of research and industrialization both domestically and internationally due to their advantages such as high photoelectric conversion efficiency, low degradation rate, good performance in low-light conditions, and high cost potential. In the tandem structure of CIGS cells, the CIGS absorber layer is the core region for generating photogenerated carriers, and its crystal quality, elemental composition, and surface morphology directly determine the final photoelectric conversion efficiency of the cell. Therefore, achieving high-performance, low-cost, and mass-producible CIGS absorber layer fabrication technology is crucial for promoting the development of the entire CIGS photovoltaic industry.

[0003] Currently, CIGS absorber layer preparation methods are mainly divided into two categories: multi-element co-evaporation and sputtering. While multi-element co-evaporation can prepare high-efficiency batteries, it is difficult to precisely control the stoichiometry of elements during large-area deposition, and the process is complex and has a long production cycle, hindering large-scale industrial production. In contrast, sputtering has become the mainstream production process due to its simple process flow, high deposition rate, and ease of achieving large-area uniform preparation. Sputtering mainly includes two technical paths: one is to first sputter a Cu-In-Ga metal pre-film followed by selenization, but this process suffers from problems such as intense selenization reaction, easy phase separation, and rough absorber layer surface, affecting subsequent interface quality and battery performance; the other is to directly sputter CIGS quaternary targets, however, due to significant differences in the sputtering yields of Cu, In, Ga, and Se, the composition of the deposited film deviates severely from the target design composition, resulting in Cu enrichment and Ga depletion, which also restricts the improvement of battery efficiency.

[0004] Despite the significant advantages of sputtering, its implementation heavily relies on high-performance sputtering targets. Currently, the preparation of Cu-Se targets, the primary source of this technology, faces severe challenges: First, the system contains numerous mesophases with vastly different properties, making it difficult to simultaneously achieve high density and high uniformity during sintering, leading to increased defects in the sputtered film. Second, when Ag or other elements are introduced to optimize performance, the significant differences in melting points between different raw materials (such as Cu-Se and Ag₂Se) make densification difficult under conventional sintering conditions, resulting in low target density and affecting the stability of the sputtering process and the quality of the film. Summary of the Invention

[0005] This application aims to provide a target material for thin-film solar cells, its preparation method, and its application, in order to solve the problems of high preparation cost, uneven composition, and low density of copper selenide targets for thin-film solar cells, thereby improving the efficiency of thin-film solar cells.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application propose a method for preparing a target material for thin-film solar cells, the method comprising the following steps: S1. Using a binary copper selenium compound as raw material, according to Cu 2+a Se 3+b Weigh the raw materials according to the stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5); perform pretreatment to obtain pretreated powder; S2. The pretreated powder is subjected to hot pressing sintering under an inert atmosphere. The sintering temperature of the hot pressing sintering is 600~850℃, the sintering pressure is 20~50MPa, and the sintering time is 1~5h to obtain copper selenium target material. The binary copper selenide is selected from one or more of copper(II) selenide, copper(III) diselenide, copper(II) selenide, and copper(II) diselenide.

[0007] Optionally, the raw material further includes a binary silver-selenium compound. Based on the atomic percentage of the copper-selenium target material, the amount of silver added in the binary silver-selenium compound is 0.05~10%; The binary silver selenide compound is selected from silver selenide.

[0008] Optionally, the preprocessing includes: After the weighed raw materials are pressed into a blank, they are subjected to high-temperature vacuum or inert gas protection treatment, and then ball milled to obtain pretreated powder.

[0009] Optionally, the temperature of the high-temperature vacuum or inert gas protective treatment is 300~750℃, and the vacuum degree is less than 10. - 2 Pa, the protection treatment time is 1~4h.

[0010] Optionally, the ball milling process includes: After the sintered green body is crushed, it is subjected to a first ball milling process to obtain the first ball milled powder and the remaining powder; The remaining powder is subjected to a second ball milling process to obtain the second ball-milled powder; The first ball-milled powder and the second ball-milled powder are mixed to obtain a pretreated powder; The second ball-milled powder accounts for 0-20 wt% of the pretreated powder. The ball milling process is carried out under a vacuum or inert gas atmosphere.

[0011] Optionally, the ball-to-material mass ratio of the first ball milling process is (3~5):1, the ball milling speed is 100~500 rpm, and the ball milling time is 4~12 h.

[0012] Optionally, the ball-to-material mass ratio in the second ball milling process is (1~3):1, the ball milling speed is 100~500 rpm, and the ball milling time is 2~12 h.

[0013] Optionally, the D50 of the first ball-milled powder is 1 to 50 micrometers, and the D90 is less than 70 micrometers; The D90 of the second ball-milled powder is less than 100 micrometers.

[0014] Secondly, embodiments of this application provide a target material for thin-film solar cells, wherein the copper selenide target material is obtained according to the above-described preparation method; The density of the copper-selenium sputtering target is greater than 95%.

[0015] Thirdly, embodiments of this application propose an application of a target material for thin-film solar cells, in which the aforementioned copper selenide target material is used in thin-film solar cells.

[0016] Compared with the prior art, this application has at least the following advantages: In the embodiments of this application, a binary copper selenium compound is used as a raw material, according to Cu 2+a Se 3+b Weigh the raw materials according to the stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5); perform pretreatment to obtain pretreated powder; subject the pretreated powder to hot pressing sintering under an inert atmosphere, with a sintering temperature of 600~850℃, a sintering pressure of 20~50MPa, and a sintering time of 1~5h to obtain copper selenide target material; the binary copper selenide compound is selected from one or more of copper(II) selenide, copper(III) diselenide, copper(II) selenide, and copper(III) diselenide.

[0017] Using binary copper selenium compounds as raw materials, according to Cu 2+a Se 3+b By weighing stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5) and precisely controlling the stoichiometric ratio of elements, it is possible to prepare copper selenide targets with controllable composition. The obtained copper selenide targets have uniform composition. At the same time, the formation of an intermediate phase through pretreatment improves the sintering activity of the powder, which is convenient for low-temperature sintering (600~850℃). The preparation process is simple, the production cycle is short, and the preparation cost is effectively reduced, which is conducive to large-scale process production. In addition, the copper selenide targets obtained by the preparation method of this application have a density greater than 95%, which can simultaneously achieve high uniformity and high density of copper selenide targets.

[0018] In summary, the preparation method of this application can solve the problems of high preparation cost, uneven composition, and low density of copper selenide target material for thin-film solar cells, thereby improving the efficiency of thin-film solar cells.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic flowchart of the preparation method of the copper selenium target provided in the embodiments of this application is shown. Detailed Implementation

[0021] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] The applicant discovered that by controlling the powder pretreatment process, powder composition ratio, and target sintering process, costs can be effectively reduced, the composition of the prepared material can be made more uniform, and the density of the target material can be improved.

[0023] In view of the above findings, this application aims to solve the problems of high preparation cost, uneven composition, and low density of copper selenide (CGS) solar cell targets. Therefore, in a first aspect, embodiments of this application provide a method for preparing a target material for thin-film solar cells, the method comprising the following steps: S1. Using a binary copper selenium compound as raw material, according to Cu 2+a Se 3+b Weigh the raw materials according to the stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5); perform pretreatment to obtain pretreated powder; S2. The pretreated powder is subjected to hot pressing sintering under an inert atmosphere. The sintering temperature of the hot pressing sintering is 600~850℃, the sintering pressure is 20~50MPa, and the sintering time is 1~5h to obtain copper selenium target material. The binary copper selenide compound is selected from one or more of copper(II) selenide (Cu2Se), copper(III) diselenide (Cu3Se2), copper(II) selenide (CuSe), and copper(II) diselenide (CuSe2).

[0024] It should be noted that a binary copper selenium compound is used as raw material, and the mixed powder is obtained by dry ball milling. The ball-to-material mass ratio during ball milling is (3~5):1, the ball ratio is 25mm:15mm:8mm (2:3:5), the ball milling speed is 100~500rpm, and the milling time is 4~12h. The ball milling process uses a vacuum nylon tank and agate balls. Before milling, the tank is evacuated to -0.1 MPa or filled with an inert atmosphere for protection. After milling, the mixed powder is sieved to obtain a mixed powder with a particle size of less than 125 micrometers. Then, the mixed powder undergoes pretreatment to obtain pretreated powder.

[0025] It should be noted that -1≤a≤0.5. For example, a can be a range of one or any two of the following: -1, -0.8, -0.5, -0.3, -0.1, 0, 0.1, 0.2, 0.3, 0.5.

[0026] It should be noted that -2≤b≤0.5. For example, b can be a range of one or any two of the following: -2, -1.8, -1.5, -1.3, -1.1, -1.0, -0.9, -0.7, -0.5, -0.3, -0.1, 0, 0.1, 0.2, 0.4, and 0.5.

[0027] It should be noted that the sintering temperature for hot pressing sintering is 600~850℃. For example, the sintering temperature can be any one or a combination of 600℃, 620℃, 650℃, 680℃, 700℃, 720℃, 750℃, 770℃, 790℃, 800℃, 810℃, 830℃, and 850℃. The temperature range of 600~850℃ can reduce the melting differences between different phases.

[0028] It should be noted that the sintering pressure is 20~50MPa. For example, the sintering pressure can be any one or any two of 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, and 50 MPa. The high pressure of 20~50MPa forces the particles of each phase to mix uniformly, avoiding premature melting and agglomeration of low-melting-point phases and compositional segregation caused by the residue of high-melting-point phases.

[0029] It should be noted that the sintering time is 1 to 5 hours. For example, the sintering time can be one or any two of the following: 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 4 hours, and 5 hours.

[0030] The combination of sintering temperature of 600~850℃, sintering pressure of 20~50MPa and sintering time of 1~5h synergistically achieves high density, compositional uniformity and high sintering activity of copper selenide (Cu-Se) targets, while avoiding the risks of intermediate phase separation and element volatilization.

[0031] It should be noted that the inert atmosphere can be either an argon atmosphere or a nitrogen atmosphere, and this application prefers an argon atmosphere.

[0032] In this embodiment, a binary copper selenium compound is used as the raw material, according to Cu 2+a Se 3+b By weighing stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5) and precisely controlling the stoichiometric ratio of elements, it is possible to prepare copper selenide targets with controllable composition. The obtained copper selenide targets have uniform composition. At the same time, the formation of an intermediate phase through pretreatment improves the sintering activity of the powder, which is convenient for low-temperature sintering (600~850℃). The preparation process is simple, the production cycle is short, and no special high-temperature and high-pressure equipment is required, which reduces the equipment investment cost. It is conducive to large-scale process production. In addition, the copper selenide targets obtained by the preparation method of this application have a density greater than 95%, which can simultaneously achieve high uniformity and high density of copper selenide targets.

[0033] In summary, the preparation method of this application can solve the problems of high preparation cost, uneven composition, and low density of copper selenide target material for thin-film solar cells, thereby improving the efficiency of thin-film solar cells.

[0034] Optionally, in one embodiment, the raw material further includes a binary silver-selenium compound. Based on the atomic percentage (at%) of the copper-selenium target material, the amount of silver added in the binary silver-selenium compound is 0.05~10%; The binary silver selenide compound is selected from silver selenide (Ag2Se).

[0035] It should be noted that the amount of silver added is 0.05% to 10%; for example, the amount of silver added can be one or any two of the following: 0.05%, 0.08%, 0.10%, 0.20%, 0.30%, 0.4%, 0.5%, 0.8%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10%.

[0036] It should be noted that in this embodiment, the raw materials include binary copper selenide compounds and binary silver selenide compounds. The copper selenide target material obtained from these raw materials can also be called a copper selenide-doped silver target material. In traditional preparation methods, both Cu-Se and Ag₂Se₃ undergo phase transformations during sintering, and the melting points of different raw materials differ significantly (Ag₂Se 900℃, CuSe 400℃, Cu₂Se 1100℃). This application uses pretreatment to form an intermediate phase, thereby improving the sintering activity of the powder.

[0037] In this embodiment, silver's strong atomic diffusion ability allows it to fill the interstitial spaces of the copper selenide lattice or form a solid solution, suppressing selective aggregation of the intermediate phase, reducing phase separation and component segregation, and improving the uniformity of the target's microstructure. Simultaneously, the composite phase structure formed by silver and copper selenide exhibits higher strength, making the target more resistant to ion bombardment during sputtering, less prone to peeling and cracking, thus extending the lifespan of the copper selenide target and improving its utilization rate. Furthermore, in CIGS thin films, silver can increase carrier concentration and mobility, reduce carrier recombination within the film, and improve the efficiency of thin-film solar cells.

[0038] Optionally, in one embodiment, the preprocessing includes: After the weighed raw materials are pressed into a blank, they are subjected to high-temperature vacuum or inert gas protection treatment, and then ball milled to obtain pretreated powder.

[0039] It should be noted that the raw material is pressed into a green body using a uniaxial pressure greater than 40 MPa. The green body is then placed in a vacuum carbon tube furnace for high-temperature vacuum or inert gas protection treatment. After the protection treatment, a sintered green body is obtained. The sintered green body is then crushed by a hydraulic press and then ball-milled to obtain pretreated powder.

[0040] Without pretreatment of the raw materials, the sintering temperature of copper selenide / copper selenide-doped silver targets can be reduced to 400~550℃. However, at this temperature, the diameter / longest side of the sintered target does not exceed 100mm (i.e., a smaller target size is obtained), the sintering mold wall thickness is greater than 200mm, the sintering pressure needs to be increased to 100~150MPa, and the target density can reach over 90%, meeting the requirements for sputtering applications. This application prioritizes pretreatment, which allows for unrestricted target diameter and lower sintering pressure, thus reducing preparation costs.

[0041] In this embodiment, the protective treatment promotes the diffusion of copper, selenium, and silver elements to form a stable intermediate phase, while the ball milling process refines the particles, breaks microscopic segregation, and achieves homogenization. In other words, the pretreatment improves the compositional uniformity and sintering activity of the copper-selenium / copper-selenium-doped silver target material, laying a crucial foundation for achieving a density of over 95% during subsequent high-pressure sintering. Simultaneously, it inhibits phase separation in the system, ensuring the consistency of the target material's microstructure.

[0042] Optionally, in one embodiment, the high-temperature vacuum or inert gas protective treatment is carried out at a temperature of 300~750°C, and the vacuum degree is less than 10. -2 Pa, the protection treatment time is 1~4h.

[0043] It should be noted that the temperature for the protective treatment is 300~750℃. For example, the temperature for the protective treatment can be one or any two of the following: 300℃, 350℃, 400℃, 450℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 600℃, 650℃, 700℃, and 750℃.

[0044] It should be noted that the protection processing time is 1 to 4 hours. For example, the time can be one of 1 hour, 2 hours, 3 hours, 4 hours, or any two of them.

[0045] In this embodiment, the vacuum level is lower than 10. -2 Pa can completely remove adsorbed water vapor, residual air and organic impurities from the powder, preventing impurities from forming a diffusion barrier on the particle surface and ensuring the free diffusion of Cu, Se and Ag elements; at the same time, it isolates oxygen to prevent Cu and Ag from oxidizing and forming oxide inclusions, thus avoiding local compositional imbalance.

[0046] A protective treatment temperature of 300~750℃ and a protective treatment time of 1~4h can improve the bonding force between different phases by allowing the low-melting-point phase to melt and diffuse in the micro-area, suppress the phase separation of different phases, avoid sintering cracking caused by local enrichment of the target material, and at the same time improve the mixing uniformity of Cu and Se elements, ensuring the stability of the film composition during sputtering.

[0047] In addition, when the target material contains silver, the protective treatment additionally forms a CuAgSe intermediate phase by introducing Ag, which not only enhances the uniformity of composition, but also further improves the sintering activity with a low melting point phase. This can reduce the temperature or pressure of subsequent high-pressure sintering, while avoiding local segregation of Ag elements.

[0048] Optionally, in one embodiment, the ball milling process includes: After the sintered green body is crushed, it is subjected to a first ball milling process to obtain the first ball milled powder and the remaining powder; The remaining powder is subjected to a second ball milling process to obtain the second ball-milled powder; The first ball-milled powder and the second ball-milled powder are mixed to obtain a pretreated powder; The second ball-milled powder accounts for 0-20 wt% of the pretreated powder. The ball milling process is carried out under a vacuum or inert gas atmosphere.

[0049] It should be noted that the first and second ball milling processes use a vacuum nylon tank and agate balls. Before ball milling, the tank is evacuated to -0.1 MPa or filled with an inert gas, such as Ar or He.

[0050] It should be noted that the first ball-milled powder and the second ball-milled powder are mixed using a mixer. The second ball-milled powder accounts for 0-20 wt% of the pretreated powder. For example, the second ball-milled powder accounts for one or any two of the following: 0 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, and 20 wt% of the pretreated powder. It is understood that the remaining powder after the first ball milling process needs to meet certain particle size requirements. A second ball milling process can be selected based on actual needs. If not required, there is no second ball-milled powder, meaning the second ball-milled powder accounts for 0% of the pretreated powder's mass fraction. If required, the remaining powder undergoes a second ball milling process, meaning the second ball-milled powder accounts for 0.01-20% of the pretreated powder's mass fraction.

[0051] In this embodiment, the pain points of easy segregation of Cu, Se, and Ag elements and easy separation of mesophase are solved by graded ball milling. By controlling the proportion of mixing to balance the requirements of uniformity and sintering activity, the pretreated powder with uniform composition, dense packing and sintering activity is finally achieved. The uniformly dispersed CuAgSe phase can alleviate the structural stress caused by the melting difference of different phases, reduce the risk of sintering cracking, and ensure the overall density of the target material is consistent.

[0052] Optionally, in one embodiment, the ball-to-material mass ratio of the first ball milling process is (3~5):1, the ball milling speed is 100~500 rpm, and the ball milling time is 4~12 h.

[0053] It should be noted that the ball-to-material mass ratio for the first ball milling process is (3~5):1. For example, the ball-to-material mass ratio for the first ball milling process can be one of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any two of these ranges.

[0054] It should be noted that the grinding ball ratio is 30mm:20mm:10mm in a ratio of 2:3:5. This ratio is mainly for fine grinding, supplemented by impact crushing. The large and medium-sized balls ensure crushing efficiency, while the high proportion of small balls ensures uniform powder particle size.

[0055] It should be noted that the ball mill speed is 100~500 rpm; for example, the ball mill speed can be 100 rpm. The range of values ​​is one or both of the following: 200 rpm, 300 rpm, 400 rpm, and 500 rpm.

[0056] It should be noted that the ball milling time is 4 to 12 hours. For example, the ball milling time can be one or any two of the following: 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, and 12 hours.

[0057] In this embodiment, the ball-to-particle ratio of (3~5):1 provides sufficient but not excessive energy input. Combined with the ball-to-particle ratio of 30mm:20mm:10mm in a ratio of 2:3:5, it can precisely control the particle size of the powder (avoiding excessive coarseness or fineness) and maximize the uniformity of the composition. Finally, it obtains the first ball-milled powder with concentrated particle size, good dispersibility, and qualified activity, which lays a key foundation for the subsequent second ball milling treatment of coarse particles and the optimization of the packing characteristics.

[0058] Optionally, in one embodiment, the ball-to-material mass ratio of the second ball milling process is (1~3):1, the ball milling speed is 100~500 rpm, and the ball milling time is 2~12 h.

[0059] It should be noted that the ball-to-material mass ratio for the second ball milling process is (1~3):1. For example, the ball-to-material mass ratio for the second ball milling process can be one of 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any two of these ranges.

[0060] It should be noted that the grinding ball ratio is 25mm:8mm:5mm in a 3:3:4 ratio. This ratio is primarily for transitional crushing and fine grinding, with a higher proportion of large balls than in the first grinding and a slightly lower proportion of small balls, but with a finer particle size. This effectively crushes larger particles while also grinding intermediate powder more efficiently. It avoids the problem of insufficient fine powder particle size or agglomeration caused by an excessive proportion of small balls, thus preventing unevenness caused by differences between the first and second grinding processes.

[0061] It should be noted that the ball mill speed is 100~500 rpm; for example, the ball mill speed can be 100 rpm. The range of values ​​is one or both of the following: 200 rpm, 300 rpm, 400 rpm, and 500 rpm.

[0062] It should be noted that the ball milling time is 2 to 12 hours. For example, the ball milling time can be one or any two of the following: 2 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, and 12 hours.

[0063] In this embodiment, a low ball-to-particle ratio (1-3):1) synergizes with the graded grinding balls (using a 25mm:8mm:5mm ratio of 3:3:4). The gentle energy prevents over-grinding and agglomeration. The graded grinding balls achieve a step-by-step process of secondary crushing, gradual refinement, and precise grinding, ultimately yielding a second ball-milled powder with a concentrated distribution and good dispersion. This powder, as a fine powder additive, not only fills the interparticle gaps of the first ball-milled powder, optimizing packing density, but also enhances subsequent sintering activity. Furthermore, because it does not agglomerate, it does not affect the overall flowability of the pretreated powder.

[0064] Optionally, in one embodiment, the D50 of the first ball-milled powder is 1 to 50 micrometers, and the D90 is less than 70 micrometers; The D90 of the second ball-milled powder is less than 100 micrometers.

[0065] It should be noted that the D50 of the first ball-milled powder is 1~50 micrometers. For example, the D50 of the first ball-milled powder can be one or any two of the following: 1 micrometer, 3 micrometer, 5 micrometer, 7 micrometer, 9 micrometer, 10 micrometer, 20 micrometer, 25 micrometer, 30 micrometer, 35 micrometer, 40 micrometer, 45 micrometer, and 50 micrometer. The D50 of the first ball-milled powder is 1~50 micrometers to ensure that the powder has sufficient specific surface area (to improve sintering activity and help with subsequent high-pressure sintering densification) without causing agglomeration due to excessively fine particle size, which would affect the powder's flowability and mold uniformity.

[0066] In this embodiment, the D50 of the first ball-milled powder is 1~50μm. This main particle size can avoid local enrichment of Ag or agglomeration of Cu-Se intermediate phase caused by excessively coarse particles. The D90 < 70 micrometers strictly controls the upper limit of coarse particles, reducing the compositional unevenness caused by large particles encapsulating elements (such as Ag encapsulating CuSe to form local high Ag regions). This particle size range allows Cu, Se, and Ag elements to fully contact at the particle level, ensuring that the key proportions of the target material (Ag / (Cu+Se), Cu / Se) are uniformly distributed in the main powder.

[0067] The second ball-milled powder has a D90 of less than 100 micrometers, which can deeply fill the gaps between the main powder and further disperse residual micro-segregation areas (such as segregation inside mixed Cu2Se and CuAgSe particles). At the same time, it can also reduce the migration resistance of Ag atoms, avoid Ag from forming secondary agglomeration due to excessive diffusion, and ensure that the low-melting-point mesophase of CuAgSe is uniformly dispersed in the powder.

[0068] Secondly, embodiments of this application provide a target material for thin-film solar cells, wherein the copper selenide target material is obtained according to the above-described preparation method; The density of the copper-selenium sputtering target is greater than 95%.

[0069] When silver is doped into copper selenide targets, the density of the silver-doped copper selenide targets is greater than 90%, which meets the requirements for sputtering applications.

[0070] In this embodiment, the copper selenide (CGS) target has a density greater than 95%, which prevents residual gas from escaping instantaneously during sputtering or the formation of target particles due to the shedding of loose structures. This reduces defects such as particle inclusions and pinholes on the CIGS film surface, improves the film's light absorption coefficient, and reduces recombination losses of photogenerated carriers. The high uniformity of the target density ensures uniform surface wear during sputtering, preventing selective wear caused by localized porosity. This ensures consistent CIGS film thickness, avoids performance dispersion caused by thickness variations, and further improves the photoelectric conversion efficiency of the battery.

[0071] Thirdly, embodiments of this application provide an application of a target material for thin-film solar cells, wherein the aforementioned copper selenide target material is used in thin-film solar cells.

[0072] In practical implementation, by stacking and sputtering two types of targets—copper selenide (CGS) or copper selenide-doped silver (GS)—with an indium gallium selenide (IGGS) target, a CIGS film with relatively uniform composition can be obtained. Furthermore, the annealing time and temperature can be reduced during annealing, shortening the time required for film composition homogenization and resulting in a lower film surface roughness. Moreover, when discrepancies between the film composition and the target composition occur, such as Cu enrichment or Ga depletion, the sputtering time of the two targets can be adjusted to ensure stable film composition after annealing, improving target utilization and reducing production costs.

[0073] In summary, the copper selenide target provided in this application can overcome the defects of high preparation cost, uneven composition, and low density when used to prepare thin-film solar cells, thereby improving the efficiency of thin-film solar cells.

[0074] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the application is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0075] The present application will be described in detail below through embodiments.

[0076] Example 1 S11. Using binary copper selenide and binary silver selenide as raw materials, wherein cuprous selenide (Cu2Se) and copper diselenide (CuSe2) are used as the binary copper selenide compounds, and silver diselenide (Ag2Se) is used as the binary silver selenide compound, the raw materials are weighed according to the stoichiometric ratio of Cu2Se3 (Ag3at%). A mixed powder is obtained by dry ball milling, with a ball-to-material mass ratio of 3:1, a ball-to-material ratio of 25mm:15mm:8mm of 2:3:5, a ball milling speed of 150 rpm, and a ball milling time of 8 hours. The ball milling process uses a vacuum nylon tank and agate balls; the tank is evacuated to below 0.1 MPa before ball milling. The mixed powder is sieved to obtain a mixed powder with a particle size of less than 125 micrometers.

[0077] S12. The above-mentioned mixed powder is pressed into a preform using a uniaxial pressure of 80 MPa, and then placed in a vacuum carbon tube furnace for protective treatment. The protective treatment temperature is 520℃, and the vacuum degree is less than 1*10. -2 The protective treatment was carried out at Pa for 4 hours to obtain a sintered green body. The sintered green body was then crushed using a hydraulic press and subjected to a first ball milling process. The ball-to-material mass ratio was 5:1, the ball ratio was 30mm:20mm:10mm (2:3:5), the milling speed was 120 rpm, and the milling time was 8 hours. A polyethylene milling jar and agate balls were used for the milling process. Before milling, the jar was evacuated to below 0.1 MPa. After sieving, the first milled powder and the remaining powder were obtained. The particle size of the first milled powder should meet the requirements of D50 of 1~50 micrometers and D90 of less than 70 micrometers. The remaining powder after sieving was subjected to a second ball milling process. The ball-to-material mass ratio was 3:1, the ball ratio was 25mm:8mm:5mm (3:3:4), the milling speed was 100 rpm, and the milling time was 6 hours to obtain the second milled powder. The particle size of the second milled powder should meet the requirement of D90 of less than 100 micrometers. The first ball mill powder and the second ball mill powder are mixed by a mixer to obtain a pretreated powder, wherein the second ball mill powder accounts for 5 wt% of the pretreated powder.

[0078] S2. The pretreated powder is loaded into 4 target materials and hot-pressed under Ar atmosphere. The hot-pressing sintering temperature is 750℃, the sintering pressure is 20MPa, and the sintering time is 2h to obtain 4 copper selenide target materials.

[0079] The density of the four copper selenide sputtering targets were 99.12%, 98.97%, 97.83%, and 98.16%, respectively.

[0080] Example 2 The difference between Example 2 and Example 1 is as follows: Example 2 adjusts the stoichiometric value in step S11 to Cu2Se (Ag 3at%).

[0081] The remaining steps and dosages are the same as in Example 1, and copper selenium targets are obtained.

[0082] The density of the four copper selenide sputtering targets were 98.46%, 96.06%, 96.50%, and 96.90%, respectively.

[0083] Example 3 The difference between Example 3 and Example 1 is as follows: In Example 3, the sintering temperature and sintering pressure in step S2 were adjusted to 600℃ and 50MPa, respectively.

[0084] The remaining steps and dosages are the same as in Example 1, and copper selenium targets are obtained.

[0085] The density of the four copper selenide sputtering targets were 96.41%, 95.84%, 96.07%, and 95.42%, respectively.

[0086] Example 4 The difference between Example 4 and Example 1 is as follows: Example 4 removes the binary silver selenium compound from step S11.

[0087] The remaining steps and dosages are the same as in Example 1, and copper selenium targets are obtained.

[0088] The density of the four copper selenide sputtering targets were 97.30%, 98.79%, 98.41%, and 97.24%, respectively.

[0089] Example 5 The difference between Example 5 and Example 1 is as follows: In Example 5, the amount of silver added in step S11 was adjusted to 0.10%.

[0090] The remaining steps and dosages are the same as in Example 1, and copper selenium targets are obtained.

[0091] The density of the four copper selenide sputtering targets were 96.27%, 98.15%, 97.83%, and 96.05%, respectively.

[0092] According to the results obtained from the various embodiments, by precisely controlling the stoichiometric ratio of elements, it is possible to prepare copper selenide targets with controllable composition. The obtained copper selenide targets have uniform composition. At the same time, the formation of an intermediate phase through pretreatment improves the sintering activity of the powder, which is convenient for low-temperature sintering. The preparation process is simple, the production cycle is short, and the preparation cost is effectively reduced, which is conducive to large-scale process production. In addition, the copper selenide targets obtained by the preparation method of this application have a density greater than 95%, which can simultaneously achieve high uniformity and high density of copper selenide targets.

[0093] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0094] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a target material for thin-film solar cells, characterized in that, The preparation method includes the following steps: S1. Using a binary copper selenium compound as raw material, according to Cu 2+a Se 3+b Weigh the raw materials according to the stoichiometric values ​​of (-1≤a≤0.5, -2≤b≤0.5); perform pretreatment to obtain pretreated powder; S2. The pretreated powder is subjected to hot pressing sintering under an inert atmosphere. The sintering temperature of the hot pressing sintering is 600~850℃, the sintering pressure is 20~50MPa, and the sintering time is 1~5h to obtain copper selenium target material. The binary copper selenide is selected from one or more of copper(II) selenide, copper(III) diselenide, copper(II) selenide, and copper(II) diselenide.

2. The preparation method according to claim 1, characterized in that, The raw materials also include binary silver selenium compounds. Based on the atomic percentage of the copper-selenium target material, the amount of silver added in the binary silver-selenium compound is 0.05~10%; The binary silver selenide compound is selected from silver selenide.

3. The preparation method according to any one of claims 1-2, characterized in that, The preprocessing includes: After the weighed raw materials are pressed into a blank, they are subjected to high-temperature vacuum or inert gas protection treatment, and then ball milled to obtain pretreated powder.

4. The preparation method according to claim 3, characterized in that, The high-temperature vacuum or inert gas protection treatment is carried out at a temperature of 300~750℃, with a vacuum degree below 10. -2 Pa, the protection treatment time is 1~4h.

5. The preparation method according to claim 3, characterized in that, The ball milling process includes: After the sintered green body is crushed, it is subjected to a first ball milling process to obtain the first ball milled powder and the remaining powder; The remaining powder is subjected to a second ball milling process to obtain the second ball-milled powder; The first ball-milled powder and the second ball-milled powder are mixed to obtain a pretreated powder; The second ball-milled powder accounts for 0-20 wt% of the pretreated powder. The ball milling process is carried out under a vacuum or inert gas atmosphere.

6. The preparation method according to claim 5, characterized in that, The ball-to-material mass ratio for the first ball milling process is (3~5):1, the ball milling speed is 100~500 rpm, and the ball milling time is 4~12 h.

7. The preparation method according to claim 5, characterized in that, The ball-to-material mass ratio for the second ball milling process is (1~3):1, the ball milling speed is 100~500 rpm, and the ball milling time is 2~12 h.

8. The preparation method according to any one of claims 5-7, characterized in that, The first ball-milled powder has a D50 of 1 to 50 micrometers and a D90 of less than 70 micrometers; The D90 of the second ball-milled powder is less than 100 micrometers.

9. A target material for thin-film solar cells, characterized in that, The copper-selenium target material is obtained by the preparation method according to any one of claims 1-8; The density of the copper-selenium sputtering target is greater than 95%.

10. An application of a target material for thin-film solar cells, characterized in that, The copper selenide target material of claim 9 is used in thin-film solar cells.

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