Preparation device and preparation method of CIGS (Copper Indium Gallium Selenide) absorption layer with U-shaped gradient band gap structure

Abstract

The invention discloses a preparation device and a preparation method of a CIGS absorption layer with a U-shaped gradient band gap structure, and belongs to the technical field of solar cells, the device mainly comprises a plurality of sputtering cavities, a plurality of evaporation cavities, a vulcanization cavity and a cooling cavity which are continuously arranged, a copper gallium sputtering target and an indium sputtering target are arranged in each sputtering cavity, a selenium evaporation nozzle and an artificial lightning generator are arranged in the evaporation cavity, the selenium evaporation nozzle is communicated with a Se evaporation source, the sputtering cavity is communicated with a sputtering gas inlet system, and the vulcanization cavity is communicated with an H2Se / H2S gas inlet system. According to the preparation method, a plurality of sub prefabricated layers containing four elements of Cu, In, Ga and Se are respectively formed in a plurality of sputtering cavities and vacuum cavities, the Ga content in each sub prefabricated layer is respectively controlled, curing treatment is carried out once by using artificial lightning when each sub prefabricated layer is deposited, so that a sub absorption layer with the controllable Ga content is formed, and finally, the CIGS absorption layer with the U-shaped gradient band gap is formed. And electron transmission is enhanced, so that the photoelectric conversion efficiency of the CIGS battery is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and specifically discloses a preparation device and a preparation method for a CIGS absorption layer with a "U"-shaped gradient band gap structure. Background Art

[0002] CIGS solar cells are chalcopyrite crystalline thin-film solar cells composed of four elements: Cu (copper), In (indium), Ga (gallium), and Se (selenium). They have the advantages of strong light absorption, good power generation stability, and high conversion efficiency, and are considered to be the most promising thin-film solar cells. The cell structure is mainly composed of soda-lime glass / back electrode layer / absorption layer / buffer layer / window layer / transparent conductive layer. At present, industrial and large-scale production mainly adopts the sputtering post-selenization method. When preparing the CIGS absorption layer, high-temperature rapid heat treatment is generally required, which consumes a lot of energy and has a high cost. The most important thing is that due to the downward migration of Ga atoms during the reaction, more Ga is gathered on the back of the absorption layer, resulting in uneven distribution of film atoms, which seriously affects the performance parameters of the battery. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the prior art and provide a preparation device and method for a CIGS absorption layer with a "U"-shaped gradient band gap structure. The method increases the S content on the surface of the absorption layer, and at the same time, Ga forms a "U"-shaped gradient band gap during the entire evaporation process, which effectively improves the collection capacity of photogenerated carriers and greatly increases the conversion efficiency of the battery.

[0004] In order to solve the above technical problems, the present invention provides a preparation device of a CIGS absorption layer having a "U"-shaped gradient band gap structure, comprising:

[0005] A sputtering chamber, an evaporation chamber, a sulfurization chamber and a cooling chamber are arranged in succession, a copper-gallium sputtering target and an indium sputtering target are arranged in the sputtering chamber, a selenium evaporation nozzle and an artificial lightning generator are arranged in the evaporation chamber, and a cooling fan is arranged in the cooling chamber, the sputtering chamber at least includes a first sputtering chamber, a second sputtering chamber and a third sputtering chamber, the evaporation chamber at least includes a first evaporation chamber, a second evaporation chamber and a third evaporation chamber, and the first sputtering chamber, the first evaporation chamber, the second sputtering chamber, the second evaporation chamber, the third sputtering chamber and the third evaporation chamber are arranged in succession in sequence;

[0006] A transmission system, arranged in the sputtering chamber, the evaporation chamber, the sulfurization chamber and the cooling chamber, for transmitting the substrate;

[0007] A vacuum system, which is connected to the sputtering chamber, the evaporation chamber, the sulfurization chamber and the cooling chamber, and is used to provide vacuum;

[0008] The cavity heating resistance wire is arranged in the evaporation cavity and the vulcanization cavity and is used for heating the evaporation cavity and the vulcanization cavity;

[0009] A Se evaporation source is connected to the selenium evaporation nozzle through a connecting pipe;

[0010] A sputtering gas inlet system, which is in communication with the sputtering chamber and is used to charge the sputtering chamber with sputtering gas;

[0011] The H2Se / H2S air intake system is connected to the vulcanization chamber.

[0012] As a further description of the present invention, a temperature control system is also included. The temperature control system is arranged in the evaporation chamber and the cooling chamber for performing precise temperature control.

[0013] As a further description of the present invention, an inlet door is provided at the entrance of the sputtering chamber, an outlet door is provided at the outlet of the cooling chamber, and isolation doors are provided between the sputtering chamber and the evaporation chamber, between the evaporation chamber and the vulcanization chamber, and between the vulcanization chamber and the cooling chamber.

[0014] As a further description of the present invention, an evaporation source heating resistance wire is provided in the Se evaporation source.

[0015] As a further description of the present invention, a control valve is provided on the connecting pipeline.

[0016] As a further description of the present invention, the connecting pipe is provided with a pipe heating device to maintain the activity of Se and prevent the material from sticking to the pipe wall.

[0017] In order to solve the above technical problems, the present invention also provides a method for preparing a CIGS absorption layer having a "U"-shaped gradient band gap structure, comprising the following steps:

[0018] (1) Turn on the vacuum system and evacuate the sputtering chamber, evaporation chamber, sulfurization chamber and cooling chamber to a vacuum degree of 3.0×10 -6 mbar; turn on the chamber heating resistor to heat the temperature in each evaporation chamber to 360-380°C; turn on the sputtering gas inlet system to fill all sputtering chambers with sputtering gas, so that the vacuum degree of all sputtering chambers is 3.0×10 -3 mbar;

[0019] (2) The substrate is sequentially transferred to each sputtering chamber and each evaporation chamber, and three elements Cu, In, and Ga are deposited by DC magnetron sputtering in the sputtering chamber, and Se is thermally evaporated in the evaporation chamber to form a multi-layer sub-prefabricated layer, and each sub-prefabricated layer is solidified by artificial lightning to form a multi-layer sub-absorption layer;

[0020] (3) Transfer to the sulfurization chamber, control the temperature of the sulfurization chamber at 380-420°C, turn on the H2Se / H2S air intake system, and perform annealing and sulfurization treatment on the surface of the absorption layer for 0.5-1 min. The sulfurization treatment eliminates the Cu-Se phase on the surface of the absorption layer and increases the S content on the surface of the absorption layer. At the same time, Ga forms a "U"-shaped gradient band gap in the entire process, which effectively improves the collection capacity of photogenerated carriers and greatly increases the conversion efficiency of the battery.

[0021] (4) The substrate is transferred to a cooling chamber and a cooling fan is turned on for rapid cooling, thereby eventually forming a CIGS absorption layer having a "U"-shaped gradient band gap structure and a surface sulfurized treatment.

[0022] As a further description of the present invention, the sub-prefabricated layer described in step (2) includes a first sub-prefabricated layer, a second sub-prefabricated layer and a third sub-prefabricated layer. The first sub-prefabricated layer is formed in the first sputtering chamber and the first evaporation chamber, and the first sub-prefabricated layer is artificially flash-cured to form a first sub-absorption layer with a high gallium content. The second sub-prefabricated layer is formed in the second sputtering chamber and the second evaporation chamber, and the second prefabricated layer is artificially flash-cured to form a second sub-absorption layer with a low gallium content. The third sub-prefabricated layer is formed in the third sputtering chamber and the third evaporation chamber, and the third prefabricated layer is artificially flash-cured to form a third sub-absorption layer with a high gallium content. The above sub-absorption layers can be repeatedly stacked multiple times.

[0023] As a further description of the present invention, the sputtering gas in step (1) is argon.

[0024] The method of the present invention adopts a preparation device of a CIGS absorption layer with a "U"-shaped gradient band gap structure, and deposits multiple Cu, In, Ga, and Se sub-prefabricated layers according to a certain process flow. First, the first sub-prefabricated layer is deposited, and the Ga / (In+Ga) range of the first sub-prefabricated layer is 0.35-0.40, and the Cu / (In+Ga) range is 0.94-0.95. After the deposition is completed, it is solidified by artificial lightning; then the second sub-prefabricated layer is deposited, and the Ga / (In+Ga) range of the second sub-prefabricated layer is 0.25-0.3, and the Cu / (In+Ga) range is 0.95-0.98. After the deposition is completed, it is solidified by artificial lightning. ; Then deposit the third sub-prefabricated layer, in which Ga / (In+Ga) ranges from 0.35 to 0.40, and Cu / (In+Ga) ranges from 0.94 to 0.95. After the deposition is completed, it is solidified by artificial lightning. More and finer sub-prefabricated layers can be deposited and solidified. Finally, introduce H2S or H2Se into the sulfurization chamber to perform surface sulfurization on the absorption layer to ensure that Ga in the absorption layer is distributed in a "U" shape while improving the degree of surface sulfurization. The above sub-absorption layers are not limited to three layers and can be any structure greater than or equal to three layers. The junction of the evaporation source system and the process chamber is heated by a resistance wire to ensure that the activity of the evaporated atoms is not reduced.

[0025] The method of the present invention forms a plurality of sub-prefabricated layers containing four elements of Cu, In, Ga and Se in a plurality of vacuum chambers, the Ga content in each sub-prefabricated layer is controlled, and each time a sub-prefabricated layer is deposited, a curing treatment is performed using artificial lightning to form a sub-absorption layer with controllable Ga content. In this way, after multiple depositions and multiple lightning treatments, a high-efficiency CIGS solar cell with a "U"-shaped gradient band gap can be formed, which enhances electron transmission, improves open circuit voltage and fill factor, and thus improves the photoelectric conversion efficiency of the CIGS cell. In addition, the present invention does not require long-term high-temperature treatment, can save a lot of energy, and is also conducive to application on low-temperature substrates such as flexible polyimide (PI) substrates. Moreover, the method is a physical method with stable process, controllable process and no pollution.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] (1) By dividing the original absorption layer into several sub-absorption layers and then reacting each layer separately by artificial lightning, the distribution of Ga in the absorption layer can be designed to form a "U"-shaped gradient band gap with high sides and low middle. This can greatly improve the spectral response of solar cells and significantly increase the battery power. It can be applied to low-temperature flexible substrates, achieving the goal of low temperature and high efficiency.

[0028] (2) Using artificial lightning to replace high-temperature post-selenization treatment can greatly save energy costs and greatly reduce battery production costs; introducing the S element in the final stage of the reaction increases the S content on the film surface, effectively improving the collection capacity of photogenerated carriers and greatly increasing the conversion efficiency of the battery;

[0029] (3) The continuous and rapid preparation method of the absorption layer can be applied to large-scale, large-size and continuous production, broadening the production methods of solar cells.

[0030] (4) Through the PID temperature control system combined with effective process design, the thickness, number of layers and performance of the absorption layer can be optimized in real time, the performance of the absorption layer can be continuously improved, and then the various performances of CIGS solar cells can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a preparation device for a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to Example 1;

[0032] Figure 2 This is a schematic structural diagram of a CIGS solar cell with a “U”-shaped gradient bandgap structure prepared in Example 3. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0034] Embodiment 1:

[0035] This embodiment provides a preparation device for a CIGS absorber layer having a "U"-shaped gradient bandgap structure, such as Figure 1 As shown, including:

[0036] The sputtering chamber and the evaporation chamber are arranged at intervals, the sputtering chamber is provided with a copper gallium sputtering target 160 and an indium sputtering target 170, the evaporation chamber is provided with a selenium evaporation nozzle 520 and an artificial lightning generator 600, the sputtering chamber includes a first sputtering chamber 111, a second sputtering chamber 112 and a third sputtering chamber 113, the evaporation chamber includes a first evaporation chamber 121, a second evaporation chamber 122 and a third evaporation chamber 123, the first sputtering chamber 111, the first evaporation chamber 121, the second sputtering chamber 112 and the third evaporation chamber 113 2. The second evaporation chamber 122, the third sputtering chamber 113 and the third evaporation chamber 123 are arranged in sequence, and a chamber door 151 is provided at the entrance of the first sputtering chamber 111, and isolation doors 152 are provided between the first sputtering chamber 111 and the first evaporation chamber 121, the first evaporation chamber 121 and the second sputtering chamber 112, the second sputtering chamber 112 and the second evaporation chamber 122, the second evaporation chamber 122 and the third sputtering chamber 113, and the third sputtering chamber 113 and the third evaporation chamber 123;

[0037] The vulcanization chamber 130 is disposed behind the third evaporation chamber 123 and an isolation door 152 is also disposed between the third evaporation chamber 123;

[0038] The cooling chamber 140 is arranged behind the vulcanization chamber 130, and an isolation door 152 is arranged between the cooling chamber 140 and the vulcanization chamber 130. A cooling fan 141 is arranged in the cooling chamber 140, and an outlet door 153 is arranged at the outlet of the cooling chamber 140;

[0039] The transmission system 200 is disposed at the bottom of the sputtering chamber, the evaporation chamber, the sulfurization chamber 130 and the cooling chamber 140 and is used to transmit the substrate;

[0040] The vacuum system 300 is connected to the sputtering chamber, the evaporation chamber, the sulfurization chamber 130 and the cooling chamber 140 to provide vacuum;

[0041] The cavity heating resistance wire 400 is arranged in the evaporation cavity and the vulcanization cavity 130 and is used to heat the evaporation cavity and the vulcanization cavity 130;

[0042] The Se evaporation system comprises a Se evaporation source 510, wherein the selenium evaporation source 510 is provided with an evaporation source heating resistor 511, and the selenium evaporation source 510 is connected to a selenium evaporation nozzle 520 disposed in the evaporation chamber through a connecting pipe, and a control valve 530 and a pipe heating device 540 are provided on the connecting pipe;

[0043] A sputtering gas inlet system 700 is connected to the three sputtering chambers and is used to charge the sputtering chambers with sputtering gas;

[0044] H2Se / H2S air intake system 800, connected to the curing chamber 130;

[0045] The PID temperature control system 900 is disposed in the evaporation chamber and the cooling chamber 140 , and is used to accurately control the temperature of the evaporation chamber and the cooling chamber 140 .

[0046] Embodiment 2:

[0047] This embodiment provides a method for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure, using the device of the first embodiment, comprising the following steps:

[0048] (1) Cleaning the substrate glass with the molybdenum back electrode;

[0049] (2) Turn on the vacuum system 300 and evacuate all sputtering chambers, evaporation chambers, vulcanization chambers 130, and cooling chambers 140 to a vacuum degree of 3.0×10 -6 mbar; turn on the chamber heating resistor 400 and the PID temperature control system 900 to control the temperature in each evaporation chamber at 360-380°C; turn on the sputtering gas inlet system 700 to fill argon gas into all sputtering chambers to make the vacuum degree of all sputtering chambers 3.0×10 -3 mbar;

[0050] (3) Turn on the copper-gallium sputtering target 160 and the indium sputtering target 170 in the first sputtering chamber 111, adjust the power of the copper-gallium sputtering target to 12.2-12.5 kW, and the power of the indium sputtering target to 10 kW, open the chamber door 151 and the transmission system 200, transfer the substrate to the first sputtering chamber 111, and sputter-deposit the three elements of Cu, In, and Ga at a deposition rate of 50-80 nm / min and a deposition time of 3-5 min;

[0051] (4) Opening the isolation door 152 between the first sputtering chamber 111 and the first evaporation chamber 121, transferring the substrate to the first evaporation chamber 121 to evaporate and deposit Se, with a deposition rate of 60 to 100 nm / min and a deposition time of 3 to 5 min, to form a first sub-prefabricated layer, wherein the Ga / (In+Ga) of the first sub-prefabricated layer is in the range of 0.35 to 0.40, the Cu / (In+Ga) is in the range of 0.94 to 0.95, the Se / (Cu+In+Ga) is in the range of 1.3 to 1.4, and the thickness is 0.4 to 0.5 μm, and the artificial lightning generator 600 is turned on to perform a rapid lightning treatment on the first sub-prefabricated layer to form a first sub-absorption layer with a high gallium content;

[0052] (5) Open the isolation door 152 between the first evaporation chamber 121 and the second sputtering chamber 112, transfer the substrate to the second sputtering chamber 112, adjust the copper gallium sputtering target power to 9.2-9.5 kW, and the indium sputtering target power to 10 kW, and sputter-deposit the three elements of Cu, In, and Ga at a deposition rate of 50-80 nm / min and a deposition time of 3-5 min;

[0053] (6) Open the isolation door 152 between the second sputtering chamber 112 and the second evaporation chamber 122, transfer the substrate to the second evaporation chamber 122 to evaporate and deposit Se, the deposition rate is 60-100 nm / min, the deposition time is 3-5 min, and the second sub-prefabricated layer has a Ga / (In+Ga) range of 0.25-0.30, a Cu / (In+Ga) range of 0.95-0.98, a Se / (Cu+In+Ga) range of 1.3-1.4, and a thickness of 0.4-0.5 μm. Turn on the artificial lightning generator 600, perform rapid lightning treatment on the second sub-prefabricated layer, and form a second sub-absorption layer with a low gallium content;

[0054] (7) Open the isolation door 152 between the second evaporation chamber 122 and the third sputtering chamber 113, transfer the substrate to the third sputtering chamber 113, adjust the copper gallium sputtering target power to 12.2-12.5 kW, and the indium sputtering target power to 10 kW, and sputter-deposit the three elements of Cu, In, and Ga at a deposition rate of 50-80 nm / min and a deposition time of 3-5 min;

[0055] (8) opening the isolation door 152 between the third sputtering chamber 113 and the third evaporation chamber 123, transferring the substrate to the third evaporation chamber 122 to evaporate and deposit Se, with a deposition rate of 60 to 100 nm / min and a deposition time of 3 to 5 min to form a third sub-prefabricated layer, and turning on the artificial lightning generator 600 to perform a rapid lightning treatment on the third sub-prefabricated layer to form a third sub-absorption layer with a high gallium content;

[0056] (9) Open the isolation door 152 between the third evaporation chamber 123 and the sulfurization chamber 130, transfer the substrate to the sulfurization chamber 130, control the temperature of the sulfurization chamber 130 at 380-420°C, start the H2Se / H2S air intake system, anneal and sulfurize the surface of the absorption layer for 0.5-1 min. After the treatment, the atomic fraction ratio of Cu:In:Ga:Se in the absorption layer is (28-35):(8-15):(4-7):(40-55); the sulfurization treatment eliminates the Cu-Se phase on the surface of the absorption layer while increasing the S content on the surface of the absorption layer. At the same time, Ga forms a "U"-shaped gradient band gap in the entire process, which effectively improves the collection capacity of photogenerated carriers and greatly increases the conversion efficiency of the battery;

[0057] (10) The isolation door 152 between the sulfurization chamber 130 and the cooling chamber 140 is opened, the substrate is transferred to the cooling chamber 140, and the cooling fan 141 is turned on for rapid cooling, which is conducive to the formation of a chalcopyrite structure in the absorption layer, and finally forms a CIGS absorption layer with Ga in a "U"-shaped gradient distribution and a sulfurized surface.

[0058] Embodiment three:

[0059] This embodiment provides a method for a CIGS solar cell having a "U"-shaped gradient bandgap structure, such as Figure 2 As shown, the following steps are included:

[0060] (1) A Mo film, a SiN layer and a Mo film are sequentially deposited on a glass substrate 10 by magnetron sputtering to form a back electrode 20;

[0061] (2) cleaning the substrate glass 10 with the molybdenum back electrode 20 to remove dirt;

[0062] (3) A CIGS absorption layer 30 having a U-shaped gradient band gap structure is evaporated and deposited on a molybdenum electrode by the method of Example 2. The CIGS absorption layer 30 includes a first sub-absorption layer 31 with a high Ga content, a second sub-absorption layer 32 with a low Ga content, and a third sub-absorption layer 33 with a high Ga content.

[0063] (4) On the CIGS absorption layer 30, a 50 nm thick InS buffer layer 40 is prepared by thermal evaporation;

[0064] (5) using magnetron sputtering to prepare an 80 nm intrinsic ZnO and a low-resistance ZnO:Al window layer 50 of about 800 nm;

[0065] (6) A 900 nm AZO transparent conductive layer 60 is prepared on the window layer 50 by using a DC magnetron sputtering method, and finally a CIGS solar cell is formed.

[0066] The absorption layer surface of the CIGS solar cell of this embodiment has a higher S content, and Ga forms a "U"-shaped gradient band gap during the entire evaporation process, which effectively improves the collection capacity of photogenerated carriers and greatly increases the conversion efficiency of the cell.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. A person skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure, characterized in that: include: A sputtering chamber, an evaporation chamber, a sulfurization chamber and a cooling chamber are arranged in succession, a copper-gallium sputtering target and an indium sputtering target are arranged in the sputtering chamber, a selenium evaporation nozzle and an artificial lightning generator are arranged in the evaporation chamber, and a cooling fan is arranged in the cooling chamber, the sputtering chamber at least includes a first sputtering chamber, a second sputtering chamber and a third sputtering chamber, the evaporation chamber at least includes a first evaporation chamber, a second evaporation chamber and a third evaporation chamber, and the first sputtering chamber, the first evaporation chamber, the second sputtering chamber, the second evaporation chamber, the third sputtering chamber and the third evaporation chamber are arranged in succession in sequence; A transmission system, arranged in the sputtering chamber, the evaporation chamber, the sulfurization chamber and the cooling chamber, for transmitting the substrate; A vacuum system, which is connected to the sputtering chamber, the evaporation chamber, the sulfurization chamber and the cooling chamber, and is used to provide vacuum; The cavity heating resistance wire is arranged in the evaporation cavity and the vulcanization cavity and is used for heating the evaporation cavity and the vulcanization cavity; A Se evaporation source is connected to the selenium evaporation nozzle through a connecting pipe; A sputtering gas inlet system, which is in communication with the sputtering chamber and is used to charge the sputtering chamber with sputtering gas; The H2Se / H2S air intake system is connected to the vulcanization chamber.

2. The device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 1, characterized in that: It also includes a temperature control system, which is arranged in the evaporation chamber and the cooling chamber.

3. The device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 1, characterized in that: An inlet door is arranged at the entrance of the sputtering chamber, an outlet door is arranged at the outlet of the cooling chamber, and isolation doors are arranged between the sputtering chamber and the evaporation chamber, between the evaporation chamber and the vulcanization chamber, and between the vulcanization chamber and the cooling chamber.

4. The device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 1, characterized in that: The Se evaporation source is provided with an evaporation source heating resistance wire.

5. The device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 1, characterized in that: The communicating pipeline is provided with a control valve.

6. The device for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 5, characterized in that: The communicating pipe is provided with a pipe heating device.

7. A method for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure, characterized in that: Utilizing the device according to any one of claims 1 to 6, comprising the following steps: (1) Turn on the vacuum system and evacuate the sputtering chamber, evaporation chamber, sulfurization chamber and cooling chamber to a vacuum degree of 3.0×10 - 6 mbar; turn on the chamber heating resistor to heat the temperature in each evaporation chamber to 360-380°C; turn on the sputtering gas inlet system to fill the sputtering chamber with sputtering gas, and adjust the vacuum degree of all sputtering chambers to 3.0×10 -3 mbar; (2) The substrate is sequentially transferred to each sputtering chamber and each evaporation chamber, and three elements Cu, In, and Ga are deposited by DC magnetron sputtering in the sputtering chamber, and Se is thermally evaporated in the evaporation chamber to form a multi-layer sub-prefabricated layer, and each sub-prefabricated layer is solidified by artificial lightning to form a multi-layer sub-absorption layer; (3) Transferring to the vulcanization chamber, controlling the temperature of the vulcanization chamber at 380-420°C, opening the H2Se / H2S air intake system, and performing annealing and vulcanization treatment on the surface of the absorption layer for 0.5-1 min; (4) The substrate is transferred to a cooling chamber and a cooling fan is turned on for rapid cooling, thereby eventually forming a CIGS absorption layer having a "U"-shaped gradient band gap structure and a surface sulfurized treatment.

8. The method for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 7, characterized in that: The sub-prefabricated layers described in step (2) include a first sub-prefabricated layer, a second sub-prefabricated layer and a third sub-prefabricated layer. The first sub-prefabricated layer is formed in a first sputtering chamber and a first evaporation chamber, and the first sub-prefabricated layer is artificially flash-cured to form a first sub-absorption layer with a high gallium content. The second sub-prefabricated layer is formed in a second sputtering chamber and a second evaporation chamber, and the second prefabricated layer is artificially flash-cured to form a second sub-absorption layer with a low gallium content. The third sub-prefabricated layer is formed in a third sputtering chamber and a third evaporation chamber, and the third prefabricated layer is artificially flash-cured to form a third sub-absorption layer with a high gallium content.

9. The method for preparing a CIGS absorber layer having a "U"-shaped gradient bandgap structure according to claim 7 or 8, characterized in that: The sputtering gas in step (1) is argon.

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