A solar cell and a method of manufacturing the same

Abstract

The application relates to the technical field of solar cells, and provides a solar cell and a preparation method thereof. The solar cell comprises, in sequence, a molybdenum metal layer, a molybdenum germanium alloy layer and a silver copper zinc tin sulfur selenium absorption layer. The preparation method comprises the following steps: obtaining a substrate containing a molybdenum metal layer; performing magnetron sputtering on the molybdenum metal layer by using a Mo-Ge alloy target to form a molybdenum germanium alloy layer; coating a precursor film containing Ag source, Cu source, Zn source, Sn source and S source on the molybdenum germanium alloy layer; and annealing the precursor film in a selenium-containing atmosphere to form a silver copper zinc tin sulfur selenium absorption layer. By constructing the molybdenum germanium alloy intermediate layer on the glass substrate containing the molybdenum metal layer, the molybdenum metal layer is effectively prevented from being selenized in the selenization process, the carrier transport capacity of the device is improved, the series resistance is reduced, Sn-related defects and defect clusters can be effectively improved, non-radiative recombination is improved, and the comprehensive performance of the device is improved.

Description

Technical Field

[0001] This invention relates to the field of technology, and more particularly to a solar cell and its preparation method. Background Technology

[0002] Today's heavy reliance on fossil fuels has brought severe challenges such as environmental pollution, climate change, and resource depletion. In contrast, solar energy, as a clean, renewable, and widely distributed energy source, is considered a key solution for achieving energy transition. Cu2ZnSn(S,Se)4 has a high light absorption coefficient, with a theoretical limit of 32.2%, and is abundant and non-toxic, making it a promising photovoltaic absorption material. However, the severe open-circuit voltage loss of CZTSSe solar cells remains a key issue limiting the improvement of device performance.

[0003] Numerous studies have shown that molybdenum selenide has poor interlayer conductivity, and excessively thick MoSe2 layers can easily lead to increased series resistance, thereby hindering carrier transport efficiency, increasing carrier recombination, and reducing Vt. OC While the presence of open-circuit voltage (FF) limits the improvement of device performance, in traditional battery manufacturing processes, it is difficult to avoid the reaction between the molybdenum substrate and selenium during selenization to form a thick MoSe2 layer, which exacerbates open-circuit voltage loss and severely limits the improvement of device efficiency. Summary of the Invention

[0004] To partially address the aforementioned technical problems, this invention provides a solar cell and its fabrication method. By employing magnetron sputtering technology to construct a molybdenum-germanium alloy interlayer on a glass substrate containing a molybdenum metal layer, the molybdenum metal layer is effectively prevented from being selenized during the selenization process, ultimately eliminating the molybdenum selenide layer. Devices fabricated in this manner not only completely eliminate molybdenum selenide at the back interface, improving carrier transport capability and reducing series resistance, but also, due to the upward diffusion of Ge from the molybdenum-germanium alloy into the absorber layer during selenization, partially replacing Sn, effectively improve Sn-related defects and defect clusters, thereby improving non-radiative recombination and ultimately enhancing device performance.

[0005] Specifically, in a first aspect, the present invention provides a method for optimizing the performance of a solar cell, wherein the solar cell includes a molybdenum metal layer; The performance optimization method includes: after depositing a molybdenum-germanium alloy layer on the molybdenum metal layer, coating a precursor film containing Ag source, Cu source, Zn source, Sn source and S source, and annealing the precursor film in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorption layer.

[0006] According to the performance optimization method of the solar cell provided by the present invention, the performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2; According to the performance optimization method of the solar cell provided by the present invention, the performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2 at the back interface.

[0007] According to the performance optimization method of the solar cell provided by the present invention, the performance optimization method includes: the back interface does not contain MoSe2 after the annealing is completed.

[0008] According to the solar cell performance optimization method provided by the present invention, the annealing temperature is 500~550℃ and the time is 10~30min.

[0009] According to the performance optimization method for solar cells provided by the present invention, the thickness of the molybdenum metal layer is 600~1000nm.

[0010] According to the performance optimization method for solar cells provided by the present invention, the thickness of the molybdenum-germanium alloy layer is 3~260nm.

[0011] According to the performance optimization method for solar cells provided by the present invention, the thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer is 2000~3000nm.

[0012] Secondly, the present invention also provides a solar cell comprising, in sequence, a molybdenum metal layer, a molybdenum-germanium alloy layer, and a silver-copper-zinc-tin-sulfur-selenium absorber layer.

[0013] In the solar cell provided by the present invention, the thickness of the molybdenum metal layer is 600~1000 nm.

[0014] In the solar cell provided by the present invention, the thickness of the molybdenum-germanium alloy layer is 20~260 nm.

[0015] According to the solar cell provided by the present invention, the thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer is 2000~3000nm.

[0016] According to the solar cell provided by the present invention, the V of the solar cell OC ≥400mV; FF ≥50%; R S Less than or equal to 3Ω·cm 2 ;R SH ≥180Ω·cm 2 .

[0017] According to the solar cell provided by the present invention, the solar cell comprises: The substrate, preferably, is selected from a soda-lime glass substrate; A back electrode disposed on the glass substrate, the back electrode comprising the molybdenum metal layer; The molybdenum-germanium alloy layer disposed on the molybdenum metal layer; The silver-copper-zinc-tin-sulfur-selenium absorber layer disposed on the molybdenum-germanium alloy layer; A buffer layer disposed on the silver-copper-zinc-tin-sulfur-selenium absorption layer, preferably, the buffer layer is selected from a CdS layer; A window layer disposed on the buffer layer, preferably, the window layer is selected from an intrinsic zinc oxide layer; A transparent conductive oxide layer disposed on the window layer, preferably, the transparent conductive oxide layer is selected from indium tin oxide layer; And an electrode disposed on the transparent conductive oxide layer, wherein the electrode is selected from Al electrodes.

[0018] Thirdly, the present invention also provides a method for preparing a solar cell as described above, comprising: A substrate containing a molybdenum metal layer was obtained; A molybdenum-germanium alloy layer was formed by magnetron sputtering on the molybdenum metal layer using a Mo-Ge alloy target. A precursor film containing Ag, Cu, Zn, Sn and S sources is coated on the molybdenum-germanium alloy layer, and the precursor film is annealed in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorber layer.

[0019] According to the method for preparing the solar cell provided by the present invention, the molar ratio of Ge to Mo in the Mo-Ge alloy target is 1:(3~5). And / or, the thickness of the precursor film is 0.5~1.5μm.

[0020] This invention provides... Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a structural diagram of the solar cell of Embodiment A1 provided by the present invention.

[0023] Figure 2 These are the XRD patterns of the absorption layers in Examples A1-A3 and Comparative Examples A1-A4 provided by the present invention.

[0024] Figure 3 These are magnified spectra of the MoSe2 diffraction peaks of the absorption layers in Examples A1-A3 and Comparative Examples A1-A4 provided by this invention.

[0025] Figure 4 These are magnified diffraction peak patterns of the absorption layers (112) of Examples A1-A3 and Comparative Examples A1-A4 provided by the present invention.

[0026] Figure 5 These are SEM cross-sectional images of the absorption layers in embodiments A1-A3 and comparative examples A1-A4 provided by the present invention.

[0027] Figure 6 These are the XRD patterns of the absorption layers in Examples A1 and A4-A7 provided by this invention.

[0028] Figure 7 These are the Raman spectra of the absorption layers in Examples A1 and A4-A7 provided by this invention.

[0029] Figure 8 These are the XRD patterns of the absorption layers in Examples A8-A9 and Comparative Examples A5-A7 provided by this invention.

[0030] Figure 9 These are magnified diffraction peak spectra of the absorption layers (112) of embodiments A8~A9 and comparative examples A5~A7 provided by the present invention.

[0031] Figure 10 These are the magnified XRD patterns of the MoSe2 absorption layers in Examples A8-A9 and Comparative Examples A5-A7 provided by this invention.

[0032] Figure 11 These are the JV curves of solar cells in Examples B1-B2 and Comparative Examples B1-B3 provided by this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] In a specific embodiment of the present invention, a method for optimizing the performance of a solar cell is first provided, wherein the solar cell includes a molybdenum metal layer; The performance optimization method includes: after depositing a molybdenum-germanium alloy layer on the molybdenum metal layer, coating a precursor film containing Ag source, Cu source, Zn source, Sn source and S source, and annealing the precursor film in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorption layer.

[0035] In some specific embodiments of the invention, the performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2; In some specific embodiments of the invention, the performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2 at the back interface.

[0036] In some specific embodiments of the invention, the performance optimization method includes: the back interface does not contain MoSe2 after the annealing is completed.

[0037] The annealing process design of this invention mainly considers the high-temperature resistance of the substrate material and the volatilization temperature of the absorber elements. If the annealing temperature is too high, it will cause the glass substrate to soften and deform, and at the same time lead to an imbalance in the proportion of absorber elements, affecting product performance; if the annealing temperature is too low, it will result in small grain size, insufficient crystallinity, and the reaction cannot proceed fully, thus forming binary and ternary secondary phases, which will damage the sample quality. In some specific embodiments of the invention, the performance optimization method includes: the annealing temperature is 500~550℃, for example, it can be any value or a range of values ​​formed by any of 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, and 550℃; the annealing time is 10~30 min, for example, it can be any value or a range of values ​​formed by any of 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, and 30 min. To achieve a better performance optimization effect, the thickness of the molybdenum-germanium alloy layer needs to be increased as the annealing time is extended.

[0038] In some specific embodiments of the invention, the performance optimization method includes: the thickness of the molybdenum metal layer is 600~1000nm, for example, it can be any value or a numerical range composed of any values ​​among 600nm, 640nm, 680nm, 720nm, 760nm, 800nm, 840nm, 880nm, 920nm, 960nm, and 1000nm.

[0039] In some specific embodiments of the invention, the performance optimization method includes: the thickness of the molybdenum-germanium alloy layer is 3~260nm, for example, it can be any value or a numerical range composed of any values ​​among 3nm, 30nm, 60nm, 90nm, 120nm, 150nm, 180nm, 210nm, 240nm, and 260nm.

[0040] In some specific embodiments of the invention, the performance optimization method includes: the thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer is 2000~3000nm, for example, it can be any value or a numerical range composed of any values ​​among 2000nm, 2100nm, 2200nm, 2300nm, 2400nm, 2500nm, 2600nm, 2700nm, 2800nm, 2900nm, and 3000nm.

[0041] To achieve better performance optimization, the thickness of the molybdenum-germanium alloy layer needs to be increased as the thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer decreases.

[0042] In some specific embodiments of the present invention, the method for optimizing the performance of the solar cell includes: forming the molybdenum-germanium alloy layer by magnetron sputtering on the molybdenum metal layer using a Mo-Ge alloy target.

[0043] In some specific embodiments of the present invention, the performance optimization method of the solar cell includes: the molar ratio of Ge to Mo in the Mo-Ge alloy target is 1:(3~5), more preferably 1:4.

[0044] In some specific embodiments of the present invention, the performance optimization method of the solar cell includes: the thickness of the precursor film is 0.5~1.5μm, for example, it can be any value or a numerical range composed of any values ​​among 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, and 1.5μm.

[0045] In a specific embodiment of the present invention, a solar cell is also provided, comprising, in sequence, a molybdenum metal layer, a molybdenum-germanium alloy layer, and a silver-copper-zinc-tin-sulfur-selenium absorber layer.

[0046] In some specific embodiments of the invention, the thickness of the molybdenum metal layer in the solar cell is 600~1000nm, for example, it can be any value or a numerical range composed of any values ​​among 600nm, 640nm, 680nm, 720nm, 760nm, 800nm, 840nm, 880nm, 920nm, 960nm, and 1000nm.

[0047] In some specific embodiments of the invention, the thickness of the molybdenum-germanium alloy layer in the solar cell is 20~260nm, for example, it can be any value or a numerical range composed of any values ​​among 20nm, 30nm, 60nm, 90nm, 120nm, 150nm, 180nm, 210nm, 240nm, and 260nm.

[0048] In some specific embodiments of the invention, the thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer in the solar cell is 2000~3000nm, for example, it can be any value or a numerical range composed of any values ​​among 2000nm, 2100nm, 2200nm, 2300nm, 2400nm, 2500nm, 2600nm, 2700nm, 2800nm, 2900nm, and 3000nm.

[0049] In some specific embodiments of the invention, the V of the solar cell OC ≥400mV; FF ≥50%; R S Less than or equal to 3Ω·cm 2 ;R SH ≥180Ω·cm 2 .

[0050] In some specific embodiments of the invention, the solar cell includes: The substrate, preferably, is selected from a soda-lime glass substrate; during high-temperature processes, sodium ions in the soda-lime glass substrate diffuse into the absorption layer above it, which helps to passivate grain boundary defects and increase carrier concentration, thereby improving the efficiency of the battery.

[0051] A back electrode is disposed on the glass substrate, the back electrode comprising the molybdenum metal layer; molybdenum has good conductivity and is relatively stable during high-temperature sulfidation / selenization. Its work function is well matched with the p-type ACZTSSe absorber layer, enabling it to collect holes (positive charges) generated by the absorber layer and transfer them to external circuits.

[0052] The molybdenum-germanium alloy layer disposed on the molybdenum metal layer; The silver-copper-zinc-tin-sulfur-selenium (CZTSSe) absorber layer is disposed on the molybdenum-germanium alloy layer; this absorber layer, also known as the ACZTSSe absorber layer, is the core of the photoelectric conversion of the battery, responsible for absorbing photons and generating electron-hole pairs. Compared to the traditional CZTSSe, the introduction of Ag (silver) to replace part of the Cu (copper) can widen the band gap, promote grain growth, and, most importantly, significantly suppress harmful copper-zinc antisite defects. When sunlight shines on this layer, photon energy excites electrons in the valence band to jump to the conduction band, generating free electrons and holes.

[0053] A buffer layer disposed on the silver-copper-zinc-tin-sulfur-selenium (CDS) absorption layer is preferably selected from a CdS layer. CdS is an n-type semiconductor. When it comes into contact with a p-type ACZTSSe, a space charge region (i.e., the built-in electric field of the pn junction) is formed at the interface due to the difference in carrier concentration. This built-in electric field is the fundamental driving force for separating electrons and holes. CdS has a relatively wide band gap (approximately 2.4 eV), allowing most visible light to penetrate to the absorption layer. More preferably, the thickness of the buffer layer is 30~60 nm, for example, it can be any value or a range of values ​​among 30 nm, 45 nm, 50 nm, 55 nm, and 60 nm.

[0054] A window layer disposed on the buffer layer is preferably selected from an intrinsic zinc oxide layer; the intrinsic zinc oxide layer can also be called an i-ZnO layer. The i-ZnO layer can prevent the upper conductive layer (ITO) from directly contacting the lower absorption layer and causing a local short circuit. At the same time, it can also reduce the plasma bombardment damage to the buffer layer during subsequent ITO sputtering. More preferably, the thickness of the window layer is 40~70nm, for example, it can be any value or a range of values ​​from 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, and 70nm.

[0055] The transparent conductive oxide layer disposed on the window layer is preferably selected from indium tin oxide (ITO) layer. The ITO layer allows sunlight to enter the battery while simultaneously collecting electrons (negative charges) separated from the pn junction and laterally conducting them to the top metal electrode. More preferably, the thickness of the transparent conductive oxide layer is 150-220 nm, for example, any value or a range of values ​​from 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, and 220 nm.

[0056] And an electrode disposed on the transparent conductive oxide layer, wherein the electrode is selected from Al electrodes.

[0057] In a specific embodiment of the present invention, a method for preparing the solar cell as described above is also provided, comprising: A substrate containing a molybdenum metal layer was obtained; A molybdenum-germanium alloy layer was formed by magnetron sputtering on the molybdenum metal layer using a Mo-Ge alloy target. A precursor film containing Ag, Cu, Zn, Sn and S sources is coated on the molybdenum-germanium alloy layer, and the precursor film is annealed in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorber layer.

[0058] In some specific embodiments of the invention, the method for preparing the solar cell includes: the molar ratio of Ge to Mo in the Mo-Ge alloy target is 1:(3~5), preferably 1:4. If the molar ratio of Ge to Mo in the Mo-Ge alloy target is too large, it will lead to an increase in the back electrode resistance and the formation of Ge-related impurity phases at the back interface; if it is too small, it will lead to an inability to effectively hinder the diffusion of Se to the back electrode.

[0059] In some specific embodiments of the invention, the method for preparing the solar cell includes: the thickness of the precursor film is 0.5~1.5μm, for example, it can be any value or a numerical range composed of any values ​​among 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, and 1.5μm.

[0060] In some specific embodiments of the present invention, the method for preparing the solar cell includes: the annealing temperature is 500~550℃, for example, it can be any value or a range of values ​​composed of any values ​​among 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, and 550℃; the time is 10~30min, for example, it can be any value or a range of values ​​composed of any values ​​among 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min, and 30min.

[0061] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0062] Example A1: This embodiment provides a method for preparing an intermediate containing a silver, copper, zinc, tin, sulfur, and selenium absorber layer, the steps of which are as follows: (1) The soda-lime glass substrate containing the Mo metal layer was ultrasonically cleaned in sequence with detergent, isopropanol, acetone and anhydrous ethanol, then rinsed with deionized water and dried with nitrogen. The thickness of the Mo metal layer was 800 nm.

[0063] (2) Place the Mo glass obtained by blowing it dry in step (1) into a plasma cleaner and treat it at 60W for 10 minutes.

[0064] (3) Using magnetron sputtering technology, a molybdenum-germanium alloy layer is deposited on the Mo glass obtained in step (2) to obtain a Mo glass substrate containing a molybdenum-germanium alloy layer. The target material used for magnetron sputtering is a Mo-Ge alloy target with a molar ratio of Ge to Mo of 1:4. The deposition time is 600s, and the thickness of the formed molybdenum-germanium alloy layer is 170nm.

[0065] (4) Silver chloride as the Ag source, cuprous chloride as the Cu source, zinc acetate as the Zn source, tin tetrachloride pentahydrate as the Sn source, and thiourea as the S source were mixed with ethylene glycol methyl ether (MOE), stirred in a water bath at 60°C for 2 hours, and filtered through a 0.45 μm filter to obtain a pale yellow precursor solution. The amounts of silver chloride, cuprous chloride, zinc acetate, tin tetrachloride pentahydrate, and thiourea added met the following requirements: Based on the molar amounts of each element, Zn / Sn=1.2, Ag / (Cu+Ag)=0.1, (Ag+Cu) / (Zn+Sn)=0.75, Tu / (Ag+Cu+Zn+Sn)=1.5.

[0066] (5) The precursor solution obtained in step (4) is spin-coated onto the Mo glass substrate containing the molybdenum-germanium alloy layer obtained in step (3) at 3000 rpm for 20 s. The substrate is then annealed on a heating plate at 280°C for 2 min and cycled 10 times to obtain a dense precursor film with a coating thickness of about 1 μm.

[0067] (6) The precursor film and selenium particles obtained in step (5) are placed in a graphite box, the graphite box is placed in a rapid annealing furnace, and kept at 520°C for 20 minutes under nitrogen atmosphere, and then naturally cooled to room temperature to obtain an intermediate containing a silver, copper, zinc, tin, sulfur and selenium absorption layer, wherein the thickness of the silver, copper, zinc, tin, sulfur and selenium absorption layer is 3000 nm.

[0068] Examples A2~A3~Comparative Examples A1~A4: It is basically the same as Example A1, except that the deposition time in step (2) is adjusted. The specific correspondence is shown in Table 1 below.

[0069] Table 1: ; Examples A4~A7: It is basically the same as Example A1, except that the annealing time in step (6) is adjusted. The specific correspondence is shown in Table 2 below.

[0070] Table 2: ; Example A8: This embodiment provides a method for preparing an intermediate containing a silver, copper, zinc, tin, sulfur, and selenium absorber layer, the steps of which are as follows: (1) Same as Example A1.

[0071] (2) Same as Example A1.

[0072] (3) Using magnetron sputtering technology, a molybdenum-germanium alloy layer is deposited on the Mo glass obtained in step (2) to obtain a Mo glass substrate containing a molybdenum-germanium alloy layer. The deposition time is 360s.

[0073] (4) Same as Example A1.

[0074] (5) Same as Example A1.

[0075] (6) The precursor film and selenium particles obtained in step (5) are placed in a graphite box, the graphite box is placed in a rapid annealing furnace, and kept at 520°C for 30 minutes under nitrogen atmosphere, and then naturally cooled to room temperature to obtain a silver-copper-zinc-tin-sulfur-selenium absorption layer, wherein the thickness of the silver-copper-zinc-tin-sulfur-selenium absorption layer is 2730 nm.

[0076] Example A9 and Comparative Examples A5-A7: It is basically the same as Example A8, except that the deposition time in step (3) is adjusted. The specific correspondence is shown in Table 3 below.

[0077] Table 3: ; Example B1 Solar Cell: This embodiment provides a method for preparing a solar cell, the steps of which are as follows: (1) A CdS film was deposited on the absorber layer film of the intermediate obtained in Example A1 by chemical bath deposition technology.

[0078] (2) Deposit i-ZnO and ITO window layers on CdS thin films by magnetron sputtering.

[0079] (3) Al electrodes were deposited by thermal evaporation technology to finally obtain a silver-copper-zinc-tin-sulfur-selenium solar cell, the structure of which is as follows: Figure 1 As shown.

[0080] Example B2 and Comparative Examples B1-B3: It is basically the same as Example B1, except that the intermediate in step (1) is adjusted. The specific correspondence is shown in Table 4 below.

[0081] Table 4: ; Test Example 1: The absorption layer samples obtained in Examples A1-A3 and Comparative Examples A1-A4 were characterized by XRD patterns, as follows: Figures 2-5 As shown. The deposition time of each embodiment and comparative example is used as a marker for the corresponding test samples to distinguish different curves. Figures 2-4 The magnified images of the corresponding XRD patterns, (112) diffraction peak, and MoSe2 diffraction peak are shown respectively. Figure 5 This shows the cross-sectional morphology of the absorption layer.

[0082] from Figure 2 As can be seen, the XRD diffraction peaks of the sample are consistent with the standard card JCPDS# 52-0868 of CZTSe.

[0083] from Figure 3 As can be seen, when the sputtering time of the Mo-Ge alloy exceeds 60s, the MoSe2 diffraction peak in the XRD basically disappears. Even after further increasing the thickness of the molybdenum-germanium alloy layer, no obvious MoSe2 diffraction peak was detected.

[0084] from Figure 4 It can be seen that, compared with the reference sample without the MoGe layer, as the sputtering time of the molybdenum-germanium alloy layer gradually increases from 10s to 600s, the diffraction peak position of the ACZTSSe(112) crystal plane exhibits a regular shift, with a slight movement towards the higher 2θ angle direction. According to the Bragg equation (2dsinθ=nλ), this peak position shift corresponds to a decrease in the interplanar spacing d.

[0085] Therefore, tests show that introducing the Mo-Ge alloy thin film does not change the phase composition of the absorber layer.

[0086] from Figure 5 As can be seen, the Mo-Ge alloy film can effectively protect the Mo substrate and inhibit the formation of MoSe2 during the selenization process, which is consistent with the reaction results of the XRD pattern.

[0087] Test Example 2: The absorption layer samples obtained in Examples A1 and A4-A7 were characterized by XRD patterns and Raman spectra, and the results are as follows: Figures 6-7 As shown.

[0088] from Figure 6 It can be seen that the MoSe2 peaks at 32° and 56.5° have disappeared, and the diffraction peaks of all samples are consistent with the standard card JCPDS# 52-0868 of CZTSe.

[0089] from Figure 7 It can be seen that it is located at 174cm -1 and 197cm -1 The two vibrational peaks belong to the A1 vibrational mode in Cu₂ZnSnSe₄, located at 234 cm⁻¹.-1 and 244cm -1 The vibrational peak is attributed to CZTSe and is located at 330 cm⁻¹. -1 The vibration peak at that location is attributed to CZTS.

[0090] XRD and Raman spectroscopy results both indicate the absence of significant impurity phases in the absorber layer, suggesting that the introduction of the Mo-Ge alloy did not alter the phase composition of CZTSSe. During high-temperature selenization, a relatively long selenization reaction time is typically required to promote grain growth and improve crystal quality in the absorber layer. However, prolonged selenization time often leads to the reaction of Mo and Se at the back electrode, forming a thick MoSe2 layer. This creates a potential barrier at the back interface, increasing interfacial resistance and hindering carrier transport and collection. Our results show that no significant MoSe2 formation occurred even under prolonged annealing conditions, indicating that the Mo-Ge alloy interlayer effectively suppresses the reaction between Mo and Se. Preventing the formation of a thick MoSe2 layer helps reduce the series resistance at the back interface, improving carrier extraction efficiency. Weakening the back interface barrier reduces carrier recombination losses. Maintaining good back contact while ensuring long-term annealing promotes grain growth contributes to obtaining both a high-quality absorber layer and excellent interfacial electrical properties, thereby improving the overall photoelectric conversion performance of the device.

[0091] Test Example 3: The absorption layer samples obtained in Examples A8-A9 and Comparative Examples A5-A7 were characterized by XRD patterns, and the results are as follows: Figures 8-10 As shown, the deposition time of each embodiment and comparative example is used as a marker for the corresponding test samples to distinguish different curves. Figures 8-10 The magnified images of the XRD pattern, (112) diffraction peak and MoSe2 diffraction peak are respectively.

[0092] from Figure 8 It can be seen that when the sputtering time of the Mo-Ge alloy exceeds 60s, the MoSe2 diffraction peak in the XRD basically disappears.

[0093] from Figure 9 It can be seen that as the Mo-Ge alloy film thickens, the (112) diffraction peak gradually shifts to a larger angle, indicating that the Ge element in the Mo-Ge alloy film will diffuse upward during the selenization process and replace the Sn element. Due to the smaller atomic radius of Ge, the lattice constant decreases, and the XRD diffraction peak shifts to a larger angle.

[0094] from Figure 10 It can be seen that as sputtering time increases, the MoSe2 layer on the back interface disappears after selenization.

[0095] Based on the data from Examples A1-A3, Comparative Examples A1-A4, Examples A8-A9, and Comparative Examples A5-A7, it can be seen that the two sets of experiments exhibit similar phenomena. However, due to the extended selenization time and reduced thickness of the absorber film, a thicker molybdenum-germanium alloy layer is required to protect the Mo substrate from selenization.

[0096] Test Example 4: The JV curves were obtained by testing the devices obtained in Examples B1-B2 and Comparative Examples B1-B3, and the specific data are shown in Table 5. OC Indicates open-circuit voltage; J SC Represents short-circuit current density; FF represents fill factor; PCE represents photoelectric conversion efficiency; R S R represents the series resistance; SH This indicates parallel resistance.

[0097] The specific testing method is as follows: AM1.5G illumination was simulated using a Keithley 2400 source meter and a Newport-94023A illuminometer, with standard test conditions of 100 mW·cm⁻¹. -2 Test range: -0.6~0.6V.

[0098] Table 5: ; As shown in Table 5, with the extension of sputtering time, the thickness of the Mo-Ge alloy film increases, the series resistance of the device decreases, and the open-circuit voltage and fill factor both increase, which is consistent with the thickness variation of MoSe2. The increase in its parallel resistance also indicates that the incorporation of Ge during selenization can improve the crystallinity of the absorber layer film, which is consistent with the reaction law of XRD.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing the performance of a solar cell, characterized in that, The solar cell includes a molybdenum metal layer; The performance optimization method includes: after depositing a molybdenum-germanium alloy layer on the molybdenum metal layer, coating a precursor film containing Ag source, Cu source, Zn source, Sn source and S source, and annealing the precursor film in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorption layer.

2. The method for optimizing the performance of a solar cell according to claim 1, characterized in that, The performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2; Preferably, the performance optimization method includes: increasing the thickness of the molybdenum-germanium alloy layer to reduce the formation of MoSe2 at the back interface; More preferably, the performance optimization method includes: the back interface does not contain MoSe2 after the annealing is completed.

3. The method for optimizing the performance of a solar cell according to claim 1 or 2, characterized in that, The annealing temperature is 500~550℃, and the time is 10~30min.

4. The method for optimizing the performance of a solar cell according to any one of claims 1 to 3, characterized in that, The thickness of the molybdenum metal layer is 600~1000 nm; and / or, The thickness of the molybdenum-germanium alloy layer is 3~260 nm; and / or, The thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer is 2000~3000 nm.

5. A solar cell, characterized in that, It consists of, in sequence, a molybdenum metal layer, a molybdenum-germanium alloy layer, and a silver-copper-zinc-tin-sulfur-selenium absorber layer.

6. The solar cell according to claim 5, characterized in that, The thickness of the molybdenum metal layer is 600~1000 nm; and / or, The thickness of the molybdenum-germanium alloy layer is 20~260 nm; and / or, The thickness of the silver-copper-zinc-tin-sulfur-selenium absorber layer is 2000~3000 nm.

7. The solar cell according to claim 5 or 6, characterized in that, The V of the solar cell OC ≥400mV; FF ≥50%; R S Less than or equal to 3Ω·cm 2 ;R SH ≥180Ω·cm 2 .

8. The solar cell according to any one of claims 5 to 6, characterized in that, The solar cell includes: The substrate, preferably, is selected from a soda-lime glass substrate; A back electrode disposed on the glass substrate, the back electrode comprising the molybdenum metal layer; The molybdenum-germanium alloy layer disposed on the molybdenum metal layer; The silver-copper-zinc-tin-sulfur-selenium absorber layer disposed on the molybdenum-germanium alloy layer; A buffer layer disposed on the silver-copper-zinc-tin-sulfur-selenium absorption layer, preferably, the buffer layer is selected from a CdS layer; A window layer disposed on the buffer layer, preferably, the window layer is selected from an intrinsic zinc oxide layer; A transparent conductive oxide layer disposed on the window layer, preferably, the transparent conductive oxide layer is selected from indium tin oxide layer; And an electrode disposed on the transparent conductive oxide layer, wherein the electrode is selected from Al electrodes.

9. A method for preparing a solar cell according to any one of claims 5 to 8, characterized in that, include: A substrate containing a molybdenum metal layer was obtained; A molybdenum-germanium alloy layer was formed by magnetron sputtering on the molybdenum metal layer using a Mo-Ge alloy target. A precursor film containing Ag, Cu, Zn, Sn and S sources is coated on the molybdenum-germanium alloy layer, and the precursor film is annealed in a selenium-containing atmosphere to form a silver-copper-zinc-tin-sulfur-selenium absorber layer.

10. The method for preparing a solar cell according to claim 9, characterized in that, The molar ratio of Ge to Mo in the Mo-Ge alloy target is 1:(3~5). And / or, the thickness of the precursor film is 0.5~1.5μm.

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