CIGS solar cell surface modification method, device and CIGS solar cell

Abstract

The present application provides a method and apparatus for surface modification of a CIGS solar cell. The microwave power source is turned on to ionize the inert gas in the microwave plasma generation chamber and generate microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generation chamber into the vacuum chamber, whereupon the CIGS thin film in the vacuum chamber is subjected to surface modification. This not only removes the Cu-Se phase on the surface but also reduces Ga inhomogeneities in the CIGS thin film, preventing the film from shielding solar energy. This achieves the purpose of surface modification and results in higher photoelectric conversion efficiency. Furthermore, the present application provides a CIGS solar cell.

Description

Technical Field

[0001] The present application relates to the technical field of thin-film solar cells, and in particular to a surface modification method and device for a CIGS solar cell, and a CIGS solar cell. Background Art

[0002] CIGS solar cells are one of the most promising solar cells, offering advantages such as a short energy payback period, high power generation, excellent power generation stability, strong light absorption capacity, high conversion efficiency, and long daytime power generation. However, high-efficiency CIGS solar cell surface modification devices are typically fabricated at high substrate temperatures above 550°C. Fabricating CIGS solar cell surface modification devices at temperatures below 500°C offers significant advantages, reducing the energy consumption and equipment requirements required under high-temperature conditions, thereby lowering the cost of CIGS solar cell surface modification devices and modules. Furthermore, low-temperature CIGS fabrication processes can be applied to certain substrates, such as flexible polyimide (PI) substrates, to obtain lightweight CIGS solar cell surface modification devices for constructing integrated photovoltaic and space applications. Previous studies have shown that the efficiency of CIGS deposited at temperatures below 450°C is comparable to that of CIGS deposited at high temperatures above 550°C. Recently, Tiwari and colleagues reported a new record efficiency of 20.8% on a polyimide substrate deposited at 450°C, attributed to their careful strategy for incorporating alkali elements into CIGS.

[0003] CIGS thin films are produced using a three-step co-evaporation process of copper, indium, gallium, and selenium, allowing for excellent control of sample composition. However, during the second copper growth step, if the copper growth rate is not controlled, a Cu-Se phase can easily form on the surface, resulting in an incomplete reaction and the formation of impurity energy levels, which can affect cell efficiency. Furthermore, this can lead to a high Ga content near the Mo back electrode and a low Ga content near the surface, resulting in a large band gap at the bottom and a small band gap at the top, causing the surface to shield certain frequencies of solar energy. Furthermore, exposure to air and moisture during vacuum processing can also cause surface contamination. Summary of the Invention

[0004] In view of this, it is necessary to provide a CIGS solar cell surface modification device and a preparation method thereof that can modify the surface of a CIGS solar cell in order to address the defects in the prior art.

[0005] To solve the above problems, this application adopts the following technical solutions:

[0006] One of the purposes of this application is to provide a method for modifying a CIGS solar cell surface modification device, comprising the following steps:

[0007] depositing the Mo back electrode on the soda-lime glass substrate;

[0008] Depositing the CIGS absorption layer on the Mo back electrode;

[0009] The CIGS thin film is prepared on the CIGS absorber layer, comprising: a first step of evaporating approximately 85-90% of In and Ga on the surface of the CIGS absorber layer at a substrate temperature of 360-390° C. to form an (In,Ga)2Se3 pre-layer; a second step of opening a baffle of a Cu source to evaporate only Cu to form CIGS crystals; and maintaining the substrate temperature the same as in the second step, evaporating the remaining 10% of In and Ga for 15-20 minutes to allow the In and Ga to react with the excess Cu in the second step, ultimately forming a slightly Cu-depleted CIGS thin film.

[0010] The microwave power source is turned on to ionize the inert gas in the microwave plasma generating chamber and generate microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generating chamber into the vacuum chamber. The microwave plasma also performs surface modification on the CIGS thin film in the vacuum chamber. The microwave plasma removes CuSe from the surface of the CIGS thin film. 2) Free Se absorbs electrons in the microwave plasma and converts into Se ions.

[0011] preparing the i-ZnO and AZO window layers on the surface-modified CIGS thin film;

[0012] A Ni / Al / Ni gate electrode is deposited on the i-ZnO and AZO window layers.

[0013] In some embodiments, the method further includes the following steps: turning on a high-voltage power supply between the microwave plasma generating chamber and the sample holder, and applying high voltage between the microwave plasma generating chamber and the sample holder.

[0014] In the first step, NaF or KF may be evaporated on the surface of the CIGS absorber layer at a substrate temperature of 360-390° C., or after the third step, another layer of NaF or KF may be evaporated at a temperature of 300° C.

[0015] A second object of the present application is to provide a modification device for the CIGS solar cell surface modification method, comprising a vacuum chamber, a deflection coil disposed inside and outside the vacuum chamber, and a microwave plasma unit connected to the vacuum chamber, wherein the microwave plasma unit comprises a microwave power source, a microwave plasma generating chamber connected to the microwave power source, and a magnetic field coil disposed around the microwave plasma generating chamber, the microwave plasma generating chamber being connected to the vacuum chamber, and the CIGS thin film being further disposed within the vacuum chamber.

[0016] The microwave power source is turned on to ionize the inert gas in the microwave plasma generating chamber and generate microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generating chamber to the vacuum chamber. The microwave plasma performs surface modification on the CIGS thin film. The microwave plasma removes CuSe on the surface of the CIGS thin film. The free Se absorbs electrons in the microwave plasma and is converted into Se ions.

[0017] In some embodiments, a sample holder is further provided at the bottom of the vacuum chamber, and the CIGS film is fixed on the sample holder.

[0018] In some embodiments, the magnetic field of the magnetic field coil is adjustable, and the magnetic field generated by adjusting the magnetic field coil is matched with the microwave frequency of the microwave plasma.

[0019] In some embodiments, a high-voltage power supply is further loaded between the microwave plasma generating chamber and the sample holder, and the high-voltage power supply can enhance the beam intensity of the microwave plasma with high voltage.

[0020] In some embodiments, the magnetic field intensity B generated by the magnetic field coil and the microwave frequency f of the microwave plasma satisfy the relationship 2πf=eB / m.

[0021] In some embodiments, the voltage of the high voltage power supply loaded between the microwave plasma generating chamber and the sample holder is between 200V and 1000V, the microwave power of the microwave plasma is 45W, the gas flow rate is 5sccm, and the working pressure is 2×10 -3 p.

[0022] In some embodiments, the vacuum chamber is further connected to a mechanical pump, and the mechanical pump can evacuate the vacuum chamber.

[0023] The third object of the present application is to provide a CIGS solar cell, comprising a soda-lime glass substrate, a Mo back electrode, a CIGS thin film, a CdS buffer layer, i-ZnO and AZO window layers, and a Ni-Al-Ni gate electrode stacked in sequence, wherein the surface of the CIGS thin film is modified by microwave plasma.

[0024] This application adopts the above technical solution, and its beneficial effects are as follows:

[0025] The present application provides a method and apparatus for surface modification of CIGS solar cells. The microwave power source is turned on to ionize the inert gas in the microwave plasma generation chamber and generate microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generation chamber into the vacuum chamber. The microwave plasma performs surface modification on the CIGS film in the vacuum chamber, removing CuSe from the surface of the CIGS film. The free Se absorbs electrons from the microwave plasma and converts into Se ions, which not only removes the Cu-Se phase on the surface but also reduces the unevenness of Ga in the CIGS film, preventing the film from shielding solar energy, thereby achieving the purpose of material surface modification and obtaining higher photoelectric conversion efficiency. Furthermore, the above-mentioned modification method and apparatus are both sealed and non-vacuumed to avoid surface contamination caused by moisture. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 This is a flow chart of the steps of the CIGS solar cell surface modification method provided in an embodiment of the present application.

[0028] Figure 2 This is a schematic diagram of the structure of the CIGS solar cell surface modification device provided in an embodiment of the present application.

[0029] Figure 3 This is a schematic structural diagram of a CIGS solar cell provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0031] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0033] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0034] See also Figure 1 , is a flow chart of the steps of a CIGS solar cell surface modification method provided in one embodiment of the present application, comprising the following steps:

[0035] Step S110: depositing the Mo back electrode on the soda-lime glass substrate.

[0036] Step S120: depositing the CIGS absorption layer on the Mo back electrode.

[0037] Step S130: Preparing the CIGS thin film on the CIGS absorber layer, including: a first step, evaporating about 85-90% of In and Ga on the surface of the CIGS absorber layer at a substrate temperature of 360-390°C to form an (In,Ga)2Se3 prefabricated layer; a second step, opening the baffle of the Cu source to evaporate only Cu to form CIGS crystals; maintaining the substrate temperature the same as in the second step, evaporating the remaining 10% of In and Ga, and maintaining the evaporation time at 15-20 minutes to allow them to react with the excess Cu in the second step, ultimately generating a slightly Cu-poor CIGS thin film.

[0038] In this embodiment, the CIGS film provided in the present application is prepared by an improved three-step co-evaporation method, including: the first step, at a substrate temperature of 360-390°C, evaporating about 85-90% of In and Ga on the surface of the CIGS absorption layer to form an (In, Ga)2Se3 prefabricated layer; the second step, opening the baffle of the Cu source and evaporating only Cu to form CIGS crystals; the third step, maintaining the substrate temperature the same as in the second step, evaporating the remaining 10% of In and Ga, and maintaining the evaporation time at 15-20 minutes, so that it reacts with the excess Cu in the second step, and finally generating a slightly Cu-poor CIGS film.

[0039] Furthermore, in the first step, NaF or KF may be evaporated on the surface of the CIGS absorber layer at a substrate temperature of 360-390°C, or after completing the third step, another layer of NaF or KF may be evaporated at a temperature of about 300°C.

[0040] It can be understood that at the beginning of the first step and after the end of the third step, alkali metal fluorides NaF and KF can be used for treatment to reduce the band gap, reduce crystal interface and crystal internal defects, and improve photoelectric conversion efficiency.

[0041] The entire experimental process was carried out in an atmosphere with sufficient Se. The CIGS film was plasma annealed and back-sputtered on the surface using ionized H2S plasma to avoid surface oxidation. The surface passivation effect reduced grain boundary recombination and increased the p-type concentration in the CIGS film.

[0042] CIGS thin films are deposited using a modified three-step co-evaporation process that incorporates an additional copper-rich phase after the second step. This process enables low-temperature growth of large CIGS grains with excellent crystallinity, even without post-deposition alkali metal treatment. CIGS solar cells deposited at 460°C achieve efficiencies comparable to those deposited at 540°C. This overcomes the issues of poor crystallinity of CIGS films caused by low substrate temperatures, resulting in smaller grains and an increased probability of photogenerated carrier recombination, which in turn reduces the cell's photoelectric conversion efficiency.

[0043] However, CIGS thin films prepared using a three-step co-evaporation process of copper, indium, gallium, and selenium can effectively control the sample composition. However, if the copper growth rate during the second step is not controlled, a Cu-Se phase can easily form on the surface, resulting in an incomplete reaction and the appearance of impurity energy levels, which affects the efficiency of the cell. Furthermore, the Ga content is high near the Mo back electrode and low near the surface, resulting in a large band gap at the bottom and a small band gap at the top, causing the surface to shield certain frequencies of solar energy.

[0044] Step S140: Turn on the microwave power source to ionize the inert gas in the microwave plasma generating chamber and generate microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generating chamber to the vacuum chamber. The microwave plasma also performs surface modification on the CIGS film in the vacuum chamber. The microwave plasma removes CuSe on the surface of the CIGS film. 2) Free Se absorbs electrons in the microwave plasma and converts into Se ions.

[0045] The surface treatment of the CIGS film by microwave plasma in this application has the following effects: 1) the microwave plasma produces an anti-sputtering effect on the surface of the CIGS film, which can remove CuSe on the surface of the CIGS film; 2) the free Se absorbs electrons in the microwave plasma and is converted into Se ions, the equation is as follows: Se+2e - =Se2 - ; 3) Due to the action of microwave plasma on the surface of CIGS solar cell, the surface temperature of CIGS solar cell rises.

[0046] Step S150: preparing the i-ZnO and AZO window layers on the surface-modified CIGS thin film.

[0047] Step S160: depositing a Ni / Al / Ni gate electrode on the i-ZnO and AZO window layers.

[0048] In some embodiments, the following steps are further included: turning on a high-voltage power supply between the microwave plasma generating chamber and the sample holder, and loading a high voltage between the microwave plasma generating chamber and the sample holder, wherein the high-voltage power supply can enhance the beam intensity of the microwave plasma with high voltage.

[0049] The CIGS solar cell surface modification method provided herein utilizes microwave plasma to modify the CIGS thin film. The microwave plasma removes CuSe from the CIGS thin film surface. Free Se absorbs electrons from the microwave plasma and converts into Se ions. This not only removes the Cu-Se phase on the surface but also reduces Ga inhomogeneities within the CIGS thin film, preventing the film from shielding solar energy. This achieves the purpose of surface modification and achieves higher photoelectric conversion efficiency. Furthermore, the modification method avoids surface contamination caused by moisture during a sealed, non-vacuum process.

[0050] See also Figure 2, is a schematic structural diagram of a CIGS solar cell surface modification device provided in one embodiment of the present application, comprising: a vacuum chamber 110, a deflection coil 120 disposed inside and outside the vacuum chamber 110, and a microwave plasma unit 130 connected to the vacuum chamber 110. The microwave plasma unit 130 includes a microwave power source 131, a microwave plasma generating chamber 132 connected to the microwave power source 131, and a magnetic field coil 133 disposed around the microwave plasma generating chamber 132. The microwave plasma generating chamber 132 is connected to the vacuum chamber 110. A CIGS thin film is also disposed in the vacuum chamber.

[0051] In this embodiment, there is one deflection coil 120 which surrounds the inside and outside of the vacuum chamber; or deflection coils are provided on both the inside and outside of the vacuum chamber.

[0052] The CIGS solar cell surface modification device provided in the above embodiment of the present application works as follows:

[0053] The microwave power source 131 is turned on to ionize the inert gas in the microwave plasma generating chamber 132 and generate microwave plasma. The magnetic field generated by the deflection coil 120 draws the microwave plasma from the microwave plasma generating chamber 132 to the vacuum chamber 110. The microwave plasma performs surface modification on the CIGS film 100 in the vacuum chamber 110. The microwave plasma generates a reverse sputtering effect on the film surface, which can remove CuSe on the surface of the CIGS film. The free Se absorbs electrons in the microwave plasma and is converted into Se ions. The microwave plasma acts on the surface of the CIGS film, causing the CIGS film to heat up.

[0054] In some embodiments, a sample holder 140 is further provided at the bottom of the vacuum chamber 110 , and the CIGS film 100 is fixed on the sample holder.

[0055] In some embodiments, the magnetic field of the magnetic field coil 133 is adjustable, and the magnetic field generated by the magnetic field coil 133 is adjusted to match the microwave frequency of the microwave plasma.

[0056] In some embodiments, a high-voltage power supply (not shown) is further installed between the microwave plasma generating chamber 132 and the sample holder 140 . The high-voltage power supply can enhance the beam intensity of the microwave plasma.

[0057] In some embodiments, the magnetic field intensity B generated by the magnetic field coil 133 and the microwave frequency f of the microwave plasma satisfy the relationship 2πf=eB / m.

[0058] In some embodiments, the voltage of the high voltage power supply loaded between the microwave plasma generating chamber and the sample holder is between 200V and 1000V, the microwave power of the microwave plasma is 45W, the gas flow rate is 5sccm, and the working pressure is 2×10 -3 p.

[0059] In some embodiments, the vacuum chamber 110 is further connected to a mechanical pump 150 , and the mechanical pump 150 can evacuate the vacuum chamber.

[0060] The CIGS solar cell surface modification device provided herein utilizes microwave plasma to modify the CIGS thin film. The microwave plasma removes CuSe from the CIGS thin film surface. Free Se absorbs electrons from the microwave plasma and converts into Se ions, which not only removes the Cu-Se phase on the surface but also reduces Ga inhomogeneities within the CIGS thin film, preventing the film from shielding solar energy. This achieves the purpose of surface modification and achieves higher photoelectric conversion efficiency. Furthermore, the modification device prevents surface contamination caused by moisture during sealed, non-vacuum processes.

[0061] See also Figure 3 The CIGS solar cell provided in the above embodiment of the present application includes a soda-lime glass substrate 11, a Mo back electrode 12, a CIGS thin film 13, a CdS buffer layer 14, an i-ZnO and AZO window layer 15 and a Ni-Al-Ni gate electrode 16 which are stacked in sequence.

[0062] In some embodiments, the Mo back electrode 120 includes a double-layer Mo film, the double-layer Mo film includes a loose layer and a dense layer, and the thickness of the double-layer Mo film is 500-1000 nm.

[0063] In some embodiments, the CIGS film 13 includes 88 at. % of GGI (Ga / ([Ga]+[In])) and 35 at. % of CIG (Cu / ([Ga]+[In])), and the thickness of the CIGS film 13 is 1.8-3 μm.

[0064] In some embodiments, the CdS buffer layer is an n-type CdS buffer layer with a thickness of 30-80 nm.

[0065] In some embodiments, in the i-ZnO and AZO window layers, the thickness of i-ZnO is 50-100 nm, and the thickness of ZnO:Al is 100-300 nm.

[0066] In some embodiments, the Ni-Al-Ni gate electrode includes a first layer of Ni electrode, an Al electrode evaporated on the first layer of Ni electrode, and a second layer of Ni electrode covering the Al electrode, wherein the thickness of the first layer of Ni electrode is The thickness of the Al electrode is 5-10 μm, and the thickness of the second layer of Ni electrode is

[0067] The CIGS solar cell provided in the above embodiment of the present application generates plasma by ionizing an inert gas and acts on the surface of the CIGS thin film of copper indium gallium selenide, and performs plasma annealing and reverse sputtering on the CIGS thin film. This not only removes the Cu-Se phase on the surface, but also further anneals the film to reduce the unevenness of Ga, thereby achieving the purpose of material surface modification.

[0068] The above technical solutions of the present application are described in detail below with reference to specific embodiments.

[0069] Example 1

[0070] 1) Use a cleaning machine to clean the substrate surface for a total of 4 times, each time for 1 hour and 20 minutes. Rotate the substrate between each cleaning to remove surface contaminants and dust. After cleaning, seal the substrate with deionized water to avoid contamination.

[0071] 2) Depositing a Mo metal film on the substrate as an impurity element barrier layer and back electrode using DC radio frequency magnetron sputtering, and achieving good contact between the Mo layer and the substrate;

[0072] 3) CIGS thin films are grown on Mo thin films using a three-step molecular beam epitaxy co-evaporation method. In addition to the conventional three-step co-evaporation process, treatment with alkali metal fluorides (NaF or KF) can be performed simultaneously at the beginning of the first step and after the completion of the third step to reduce the band gap, minimize defects at the crystal interface and within the crystal, and improve photoelectric conversion efficiency.

[0073] 4) Turn on the magnetic field coil and adjust the current so that the magnetic field generated by the magnetic field coil matches the frequency of the microwave, providing a magnetic field basis for the generation of microwave plasma;

[0074] 5) H2S is introduced into the microwave plasma generation chamber at a gas flow rate of 5 sccm. The power supply of the deflection coil is turned on at a power of 45 W and an operating pressure of 2*10 -3 Pa, the magnetic field generated by the deflection coil draws the microwave plasma from the generation chamber to the sample holder to treat the CIGS film for 30 min;

[0075] 6) Turn on the high-voltage power supply and apply high voltage between the microwave plasma generating chamber and the sample holder to enhance the plasma beam intensity;

[0076] 7) After surface modification, a CdS buffer layer and PN junction formation layer are deposited on the CIGS film surface. Using CdSO₄ as the cadmium source, thiourea as the sulfur precursor, and NH₃·H₂O as the buffer, the CdS film is deposited on the CIGS film surface in a water bath. After the reaction, the film is annealed at 160°C.

[0077] 8) Intrinsic zinc oxide (I-ZnO) and aluminum-doped zinc oxide (AZO) thin films were deposited on the surface using magnetron sputtering. The reactant gases used for I-ZnO were Ar and O2, with an Ar flow rate of 200 sccm and an O2 flow rate of 2 sccm. The initial sputtering power was 120 W and subsequently increased to 220 W. The reactant gases used for AZO were Ar and H2, with an Ar flow rate of 200 sccm and an H2 flow rate of 2 sccm. The temperature was maintained at 160°C for 15 minutes, and the sputtering power was 750 W.

[0078] 9) The gate is prepared by electron beam evaporation. The target materials used are Ni and Al, and the thickness of the Ni layer is The thickness of Al is The gate is obtained, completing the CIGS solar cell preparation process.

[0079] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A method for surface modification of a CIGS solar cell, characterized in that: The steps include: Depositing a Mo back electrode on a soda-lime glass substrate; Depositing a CIGS thin film on the Mo back electrode; Depositing a CIGS thin film on the Mo back electrode comprises: first, evaporating about 85-90% of In and Ga on the surface of the Mo back electrode at a substrate temperature of 360-390° C. to form an (In, Ga)2Se3 prefabricated layer; second, opening a baffle of a Cu source to evaporate only Cu to form CIGS crystals; and third, evaporating the remaining 10% of In and Ga while maintaining the substrate temperature the same as in the second step, maintaining the evaporation time at 15-20 minutes, to allow the remaining 10% of In and Ga to react with the excess Cu in the second step, ultimately forming a slightly Cu-depleted CIGS thin film; The CIGS thin film is subjected to surface modification treatment using a modification device, the modification device comprising a vacuum chamber, a deflection coil disposed inside and outside the vacuum chamber, and a microwave plasma unit connected to the vacuum chamber, the microwave plasma unit comprising a microwave power source, a microwave plasma generating chamber connected to the microwave power source, and a magnetic field coil disposed around the microwave plasma generating chamber, the microwave plasma generating chamber being connected to the vacuum chamber, and the CIGS thin film being disposed within the vacuum chamber; Turning on the microwave power source ionizes the inert gas in the microwave plasma generating chamber and generates microwave plasma. The magnetic field generated by the deflection coil draws the microwave plasma from the microwave plasma generating chamber into the vacuum chamber. The microwave plasma also performs surface modification on the CIGS thin film in the vacuum chamber. The microwave plasma removes CuSe from the surface of the CIGS thin film. The free Se absorbs electrons in the microwave plasma and is converted into Se ions. preparing i-ZnO and AZO window layers on the surface-modified CIGS film; Depositing a Ni / Al / Ni gate electrode on the i-ZnO and AZO window layers; In the first step, NaF or KF is evaporated on the surface of the Mo back electrode at a substrate temperature of 360-390°C, or after completing the third step, a layer of NaF or KF is evaporated at a temperature of 300°C; Turning on a high-voltage power supply between the microwave plasma generating chamber and the sample holder to apply high voltage between the microwave plasma generating chamber and the sample holder; The voltage of the high-voltage power supply loaded between the microwave plasma generating chamber and the sample holder is between 200V and 1000V, the microwave power of the microwave plasma is 45W, the gas flow rate is 5sccm, and the working pressure is 2×10 -3 p.

2. The CIGS solar cell surface modification method according to claim 1, wherein: The magnetic field of the magnetic field coil is adjustable, and the magnetic field generated by adjusting the magnetic field coil is matched with the microwave frequency of the microwave plasma.

3. The CIGS solar cell surface modification method according to claim 1, wherein: The high-voltage power supply can enhance the beam intensity of the microwave plasma with high voltage.

4. The method for surface modification of a CIGS solar cell according to claim 3, wherein: The magnetic field intensity B generated by the magnetic field coil and the microwave frequency f of the microwave plasma satisfy the relationship 2πf=eB / m.

5. The CIGS solar cell surface modification method according to claim 1, wherein: The vacuum chamber is further connected to a mechanical pump, which can evacuate the vacuum chamber.

6. A CIGS solar cell, characterized in that: The CIGS solar cell surface modification method according to any one of claims 1 to 5 comprises a soda-lime glass substrate, a Mo back electrode, a CIGS film, a CdS buffer layer, i-ZnO and AZO window layers, and a Ni-Al-Ni gate electrode stacked in sequence, wherein the surface of the CIGS film is modified by microwave plasma.

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