A copper-zinc-tin-sulfur-selenium solar cell and a preparation method thereof

Abstract

The application provides a copper-zinc-tin-sulfur-selenium solar cell and a preparation method thereof. The copper-zinc-tin-sulfur-selenium solar cell comprises, from bottom to top, a substrate, a back electrode, a CZTSxSe1-x (0<=x<=1) absorption layer, a buffer layer, a ZnO window layer, a conductive window layer and a top gate electrode, wherein the ZnO window layer is prepared by a solution method. By introducing the ZnO window layer prepared by the solution method, damage of a magnetic control sputtering method to a CZTSSe / CdS substrate is avoided, a pn junction zone defect concentration is greatly reduced, carrier recombination is inhibited, and an open circuit voltage of the CZTSSe solar cell is improved. The copper-zinc-tin-sulfur-selenium solar cell can further comprise an interface modification layer between the ZnO window layer and the conductive window layer, so that the electrical performance of the ZnO window layer is improved, an energy band structure of the ZnO-R window layer and front and rear layers is optimized, and a fill factor of the CZTSSe solar cell is improved.

Description

Technical Field

[0001] This invention relates to the field of thin-film solar cell technology, and in particular to a copper-zinc-tin-sulfur-selenium solar cell and its preparation method. Background Technology

[0002] Large-scale utilization of solar energy resources is a crucial means of addressing global energy and environmental issues, with photovoltaic (PV) power generation being one of the most important methods. As a novel type of thin-film solar cell, copper-zinc-tin-sulfur-selenium (CZTSSe) solar cells possess strong competitiveness in the future PV market due to their excellent cost-effectiveness, meeting the application needs of various scenarios such as building-integrated photovoltaics (BIPV) and flexible wearable devices. In recent years, through methods such as absorber phase modulation, the efficiency of these cells has been increased to over 14%.

[0003] However, compared to novel solar cells such as perovskite cells, CZTSSe cells still have significant room for performance improvement. In particular, their open-circuit voltage only reaches 60% of the Shockley-Quiesser theoretical limit, remaining at a relatively low level. Severe interface defects in the depletion region are a major reason for the high carrier recombination rate and large open-circuit voltage loss. While research and reports on interface passivation have emerged, they only alleviate this problem to a certain extent. Therefore, a technical solution is urgently needed to reduce defect formation at its source, further reduce interface defects, increase open-circuit voltage, and improve the efficiency of CZTSSe cells. Summary of the Invention

[0004] In view of the above problems, a copper-zinc-tin-sulfur-selenium solar cell and its preparation method are proposed to overcome or at least partially solve the above problems.

[0005] One objective of this invention is to prepare a ZnO window layer using a solution-based method, thereby avoiding the bombardment damage to the CZTSSe / CdS(pn) junction region caused by magnetron sputtering, significantly reducing CZTSSe / CdS interface defects and carrier recombination rate, and improving the open-circuit voltage of CZTSSe solar cells.

[0006] A further objective of this invention is to further improve the fill factor and battery efficiency by introducing an interface modification layer.

[0007] A further objective of this invention is to improve cell repeatability and reduce operational difficulty while obtaining high-performance CZTSSe solar cells.

[0008] According to one aspect of the present invention, a copper-zinc-tin-sulfur-selenium solar cell is provided, comprising a back electrode and CZTS stacked sequentially from bottom to top. x Se 1-x(0≤x≤1) an absorption layer, a buffer layer, a ZnO window layer, a conductive window layer, and a top gate electrode, wherein the ZnO window layer is prepared by a solution method.

[0009] Optionally, the thickness of the ZnO window layer is 1–100 nm.

[0010] Optionally, the ZnO window layer is prepared from ZnO sol-gel or ZnO nanocrystal colloidal solution, wherein the concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution is 0.1–100 mg / mL.

[0011] Preferably, the concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution is 20–50 mg / mL.

[0012] Optionally, the copper-zinc-tin-sulfur-selenium solar cell further includes an interface modification layer between the ZnO window layer and the conductive window layer, the interface modification layer being prepared by a solution method.

[0013] Optionally, the thickness of the interface modification layer is 1–20 nm.

[0014] Optionally, the material of the interface modification layer is one or more of crown ethers, thiols, phosphonates, and amines;

[0015] The concentration of the solution of the material used to prepare the interface modification layer is 0.1–10 mg / mL.

[0016] Preferably, the solution concentration of the material is 0.5 to 1 mg / mL.

[0017] Optionally, the crown ethers include one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, 21-crown ether-7, and dibenzo-18-crown ether-6;

[0018] The thiols include one or more of phenylethyl mercaptan, ethylene dithiol, isobutyl mercaptan, cyclopentanethiol, and pyrimidine mercaptan;

[0019] The phosphonic acids include one or more of phosphorylacetic acid, butylphosphonic acid, p-carboxyphenylphosphonic acid, halophenylphosphonic acid and benzylphosphonic acid;

[0020] The amines include one or more of ethylenediamine, polyethyleneimine, cysteine, diethylenetriamine, and melamine.

[0021] Optionally, the solution method includes spin coating, blade coating, or spray coating.

[0022] Optionally, the material of the back electrode is molybdenum.

[0023] Optionally, the CZTSx Se 1-x (0≤x≤1) The absorber layer contains one or more of the following elements for doping or alloying: Ag, Cd, Ge and alkali metals.

[0024] Optionally, the material of the buffer layer is one or more of cadmium sulfide, zinc cadmium sulfide (Zn,Cd)S, and zinc magnesium oxide (Zn,Mg)O.

[0025] Optionally, the conductive window layer is made of indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO).

[0026] Optionally, the top gate electrode is a nickel / aluminum bilayer electrode, an aluminum electrode, or a silver electrode.

[0027] According to another aspect of the present invention, a method for fabricating the aforementioned copper-zinc-tin-sulfur-selenium solar cell is also provided, comprising: sequentially fabricating the back electrode and CZTS of the solar cell from bottom to top. x Se 1-x The invention comprises an absorber layer, a buffer layer, a ZnO window layer, a conductive window layer, and a top gate electrode, wherein the ZnO window layer is prepared in situ using a solution method.

[0028] The copper-zinc-tin-sulfur-selenium solar cell provided by this invention avoids damage to the CZTSSe / CdS substrate caused by magnetron sputtering by introducing a ZnO window layer prepared by solution method, greatly reduces the defect concentration in the pn junction region, suppresses carrier recombination, and improves the open-circuit voltage of the CZTSSe solar cell.

[0029] Furthermore, the copper-zinc-tin-sulfur-selenium solar cell of the present invention improves the electrical performance of the ZnO window layer by introducing an interface modification layer, which can optimize the band structure matching between the ZnO window layer and the preceding and following layers, thereby further improving the fill factor and cell efficiency.

[0030] Furthermore, in the method for preparing copper-zinc-tin-sulfur-selenium solar cells provided by the present invention, the ZnO window layer and interface modification layer are prepared in situ by solution method, which improves process reliability and yield while ensuring the excellent performance of CZTSSe solar cells. The method is easy to operate and has good repeatability.

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0032] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0034] Figure 1 This is a schematic diagram of the structure of a CZTSSe solar cell according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic flowchart of a method for fabricating a CZTSSe solar cell according to an embodiment of the present invention;

[0036] Figures 3a to 3c The ZnO window layer, interface modification layer, and CZTSSe solar cell according to embodiments of the present invention x Se 1-x A schematic diagram of the band structure of the absorption layer. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0038] Currently, the performance of CZTSSe solar cells still has significant room for improvement. To reduce interface defects in the depletion region and thus decrease open-circuit voltage loss, research has begun on interface passivation; however, the results have not been significant.

[0039] The inventors of this application have discovered a point overlooked by those skilled in the art: interface defects are introduced during the current process of fabricating the ZnO window layer of CZTSSe solar cells using magnetron sputtering. Typically, continuous bombardment of the CZTSSe / CdS heterojunction region with particles on the order of 100 eV reduces the crystallinity of CdS and generates numerous defects in the depletion region, forming recombination centers and affecting the open-circuit voltage. Based on these findings, this invention proposes a top-down passivation strategy that can reduce defect formation at its source, which is of great significance for further reducing interface defects, improving the on-state voltage, and enhancing the efficiency of CZTSSe solar cells.

[0040] This invention provides a copper-zinc-tin-sulfur-selenium (CZTSSe) solar cell. Figure 1A schematic diagram of the structure of a CZTSSe solar cell 100 according to an embodiment of the present invention is shown. See also Figure 1 As shown, the CZTSSe solar cell 100 provided in this embodiment of the invention includes a back electrode 110 and CZTS cells stacked sequentially from bottom to top. x Se 1-x (0≤x≤1) An absorber layer 120, a buffer layer 130, a ZnO window layer 140, a conductive window layer 160, and a top gate electrode 170 are included. The ZnO window layer 140 is prepared by a solution method. For simplicity, the solution-prepared ZnO window layer 140 will be referred to as the ZnO-R window layer 140 below. Because it is introduced via a solution method, the ZnO-R window layer 140 does not damage the pn junction substrate and can isolate the pn junction substrate from sputtering damage caused by the conductive window layer 160.

[0041] In the CZTSSe solar cell 100 of this embodiment, by introducing a ZnO-R window layer 140 prepared by solution method, the bombardment of the pn junction substrate (absorber layer 120 / buffer layer 130) by particles with kinetic energy exceeding 100eV during the preparation process by magnetron sputtering is avoided, thus protecting the integrity of the pn junction lattice, reducing defect formation, suppressing carrier recombination, and improving the open-circuit voltage of the device.

[0042] In a further embodiment, to optimize the electrical performance and band structure of the ZnO-R window layer 140, an interface modification layer 150 can be further introduced into the CZTSSe solar cell 100. That is, the CZTSSe solar cell 100 may further include the interface modification layer 150 located between the ZnO-R window layer 140 and the conductive window layer 160. The interface modification layer 150 can improve the electrical performance of the ZnO-R window layer 140 and optimize the band structure of the ZnO-R window layer 140 and the preceding and following layers, thereby further improving the fill factor and cell efficiency of the solar cell. The interface modification layer 150 can be prepared by a solution method.

[0043] In some embodiments, the material of the interface modification layer 150 may be, but is not limited to, one or more of crown ethers, thiols, phosphonates and amines.

[0044] Specifically, crown ethers may include one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, 21-crown ether-7, and dibenzo-18-crown ether-6. Thiols may include one or more of phenylethanethiol, ethylenedithiol, isobutylthiol, cyclopentanethiol, and pyrimidinethiol. Phosphonates may include one or more of phosphorylacetic acid, butylphosphonic acid, p-carboxyphenylphosphonic acid, halophenylphosphonic acid, and benzylphosphonic acid. Amines may include one or more of ethylenediamine, polyethyleneimine, cysteine, diethylenetriamine, and melamine.

[0045] In a preferred embodiment, the material of the interface modification layer 150 is a crown ether material.

[0046] In some embodiments, the thickness of the ZnO-R window layer 140 can be any value within the range of 1 to 100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, etc. This thickness allows the ZnO-R window layer 140 to achieve CZTS (Continuous ZnO-Temperature Transformation). x Se 1-x A high coverage is achieved on the substrate of the absorption layer 120 / buffer layer 130 to avoid leakage current, while enabling rapid tunneling transport of charge carriers.

[0047] In some embodiments, the ZnO-R window layer 140 may be prepared from ZnO sol-gel or ZnO nanocrystal colloidal solution.

[0048] Furthermore, to obtain a ZnO-R window layer 140 of sufficient thickness and performance, the concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution used can be 0.1–100 mg / mL, for example, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 25 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 50 mg / mL, 55 mg / mL, 60 mg / mL, 65 mg / mL, 70 mg / mL, 75 mg / mL, 80 mg / mL, 85 mg / mL, 90 mg / mL, 95 mg / mL, etc. Preferably, the concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution is 20–50 mg / mL.

[0049] In some embodiments, the thickness of the interface modification layer 150 can be any value within the range of 1 to 20 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, etc. This thickness not only allows the interface modification layer 150 to completely cover the solution-processed ZnO-R window layer 140, but also allows for continuous adjustment of the band structure of the ZnO-R window layer 140, achieving band matching between the ZnO-R window layer 140 and the buffer layer 130 and the conductive window layer 160.

[0050] In some embodiments, to obtain an interface modification layer 150 of sufficient thickness and performance, the solution concentration of the material used to prepare the interface modification layer 150 can be 0.1–10 mg / mL, for example, 0.3 mg / mL, 0.8 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, etc. Preferably, the solution concentration of the material used to prepare the interface modification layer 150 can be 0.5–1 mg / mL.

[0051] In some specific embodiments, the aforementioned solution method may include spin coating, blade coating, spray coating, etc.

[0052] In some embodiments, the back electrode 110 may be made of molybdenum. Of course, the back electrode 110 may also be made of other suitable back electrode materials, and the present invention does not impose specific limitations on the material of the back electrode 110.

[0053] Similarly, the buffer layer 130, the conductive window layer 160, and the top grid electrode 170 can also be made of materials commonly used in copper-zinc-tin-sulfur-selenium solar cells, and the present invention does not impose specific limitations on them.

[0054] In some embodiments of the present invention, the material of the buffer layer 130 may be one or more of cadmium sulfide, zinc cadmium sulfide ((Zn,Cd)S), zinc magnesium oxide ((Zn,Mg)O), etc.

[0055] In some embodiments of the present invention, the conductive window layer 160 may be one or more of indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO).

[0056] In some embodiments of the present invention, the top gate electrode 170 may be a double-layer electrode, for example, Figure 1 The diagram shows a double-layer top gate electrode. Specifically, the double-layer top gate electrode can be a nickel / aluminum double-layer electrode. In other embodiments, the top gate electrode 170 can also be a single-layer electrode, specifically, for example, an aluminum electrode or a silver electrode.

[0057] In some embodiments of the present invention, CZTS x Se 1-x (0≤x≤1) The absorption layer 120 may contain one or more elements such as Ag, Cd, Ge, and alkali metals for doping or alloying.

[0058] In some embodiments of the present invention, such as Figure 1As shown, the copper-zinc-tin-sulfur-selenium solar cell 100 may further include a substrate 180 for supporting the aforementioned layers. The substrate 180 may be an insulating substrate, such as a soda-lime glass substrate. The substrate 180 may also be a conductive substrate, such as a flexible / rigid molybdenum foil, in which case the substrate 180 can simultaneously function as a substrate and a back electrode, and the back electrode 110 layer becomes optional (e.g., it can be omitted).

[0059] Based on the same technical concept, this invention also provides a method for fabricating the aforementioned copper-zinc-tin-sulfur-selenium solar cell 100. This method mainly includes sequentially fabricating the back electrode 110 and CZTS of the solar cell 100 from bottom to top. x Se 1-x The absorption layer 120, buffer layer 130, ZnO window layer 140, conductive window layer 160 and top gate electrode 170 are provided, wherein the ZnO window layer 140 is prepared in situ by solution method.

[0060] In some embodiments, the ZnO window layer 140 is prepared by spin coating, blade coating or spray coating using ZnO sol-gel or ZnO nanocrystal colloidal solution.

[0061] In some embodiments, CZTS x Se 1-x The absorber layer 120 is prepared by solution method, vacuum method, electrochemical deposition method or nanocrystal method.

[0062] In some further embodiments, the copper-zinc-tin-sulfur-selenium solar cell 100 also includes an interface modification layer 150 located between the ZnO window layer 140 and the conductive window layer 160. Accordingly, the preparation method may further include: preparing the interface modification layer 150 in situ by solution processing.

[0063] Furthermore, solution methods include spin coating, blade coating, and spray coating.

[0064] In the preparation method of the copper-zinc-tin-sulfur-selenium solar cell 100 of this invention, a ZnO window layer 140 and an interface modification layer 150 are introduced by solution method. While ensuring the excellent performance of the prepared copper-zinc-tin-sulfur-selenium solar cell, the process has high reliability, high yield, low operation difficulty and good repeatability.

[0065] The preparation method of the copper-zinc-tin-sulfur-selenium solar cell 100 of the present invention is described in detail below by way of a specific embodiment.

[0066] Figure 2 A schematic flowchart illustrating a method for fabricating a copper-zinc-tin-sulfur-selenium solar cell 100 according to an embodiment of the present invention is shown. See also Figure 2 As shown, the preparation method includes the following steps:

[0067] Step S1: Sputter Mo back electrode 110 onto a soda-lime glass substrate 180.

[0068] In step S1, the soda-lime glass substrate 180 is sequentially cleaned with detergent, deionized water, and ethanol, and then dried with nitrogen. A 1.2 μm thick Mo film is then sputtered onto the clean soda-lime glass substrate 180 as the back electrode 110 using DC magnetron sputtering. During the sputtering process, the chamber floor vacuum is 4 × 10⁻⁶. -4 The working pressure is 0.2 Pa, the working atmosphere is argon, the substrate heating temperature is 400℃, and the sputtering time is 1 hour.

[0069] Step S2: Prepare the absorber layer precursor film.

[0070] In step S2, a precursor film for the absorber layer is prepared using spin coating. Specifically, copper acetate, zinc chloride, stannous chloride, and thiourea are dissolved in dimethyl sulfoxide to prepare a precursor solution with an elemental ratio of Cu / (Zn+Sn) = 1.12 and Zn / Sn = 0.75. The precursor solution is spin-coated onto the prepared sample in a nitrogen-filled glove box at a spin speed of 2000 r / min for 40 s, followed by annealing at 300℃ for 2 min. The spin-coating-annealing operation is repeated 7-8 times to obtain a 1 μm thick precursor film for the absorber layer.

[0071] Step S3, selenization (sulfidation) to form CZTS x Se 1-x Film 120.

[0072] In step S3, the prepared precursor film and selenium (sulfur) particles are placed in a rapid heating furnace and annealed at 550°C for 15 min under a nitrogen atmosphere to form CZTS. x Se 1-x The absorber layer 120 has a thickness of 1.2 μm. Those skilled in the art will understand that the ratio of S to Se in the final absorber layer film can be controlled by controlling the amount of thiourea and the amount of selenium or sulfur particles.

[0073] Step S4: Prepare CdS buffer layer 130.

[0074] In step S4, a 30 nm thick CdS film is prepared as a buffer layer 130 using a chemical bath deposition method.

[0075] Step S5: Prepare solution-processed ZnO-R window layer 140.

[0076] In step S5, the solution-based ZnO-R window layer 140 is prepared using either the sol-gel method or the nanocrystal method. First, a precursor solution is prepared. Specifically, for the sol-gel method, zinc acetate dihydrate and ethanolamine are dissolved in ethylene glycol methyl ether, with a Zn to amine ratio of 1:1, resulting in a ZnO concentration of 0.1–100 mg / mL. The solution is stirred at room temperature for 3 hours until completely clear and transparent, yielding the sol-gel precursor solution. For the nanocrystal method, under constant temperature stirring at 60°C, 50 mL of 40 mM KOH methanol solution is slowly added dropwise to 100 mL of 70 mM zinc acetate dihydrate methanol solution. After stirring continuously for 150 minutes, the solution is centrifuged, washed twice with methanol, and then dispersed in a mixed solution of chloroform and methanol or N,N-dimethylformamide (DMF) at a concentration of 0.1–100 mg / mL, yielding the nanocrystal precursor solution. Subsequently, the aforementioned precursor solution was spin-coated onto the buffer layer 130 at a speed of 3000 r / min for 25 s, followed by annealing on a hot plate for 10 min to obtain a ZnO-R window layer 140 of a certain thickness. The annealing temperature can be selected within the range of 150 to 200 °C without significantly affecting the device performance.

[0077] Step S6: Prepare the interface modification layer 150.

[0078] In step S6, the interface modification layer 150 is deposited on the ZnO-R window layer 140 using a solution method.

[0079] The interface decoration layer 150 is made of one or more of the following materials, but not limited to:

[0080] Crown ethers: 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, 21-crown ether-7, dibenzo-18-crown ether-6, etc.;

[0081] Thiols: phenylethyl mercaptan, ethylene dithiol, isobutyl mercaptan, cyclopentanethiol, pyrimidine mercaptan, etc.

[0082] Phosphonic acids: phosphorylated acetic acid, butylphosphonic acid, p-carboxyphenylphosphonic acid, halophenylphosphonic acid, benzylphosphonic acid, etc.;

[0083] Amines: ethylenediamine, polyethyleneimine, cysteine, diethylenetriamine, melamine, etc.

[0084] Specifically, taking 18-crown ether-6 as an example, an ethanol solution of 0.1-10 mg / mL of 18-crown ether-6 was prepared, and an appropriate amount of the solution was dropped onto the ZnO-R window layer 140. The spin-coating speed was 3000 r / min, the spin-coating time was 25 s, and the solution was annealed at 120℃ for 3 min to obtain an interface modification layer 150 of a certain thickness.

[0085] Step S7: Prepare ITO conductive window layer 160.

[0086] In step S7, a 200 nm thick ITO thin film is prepared by magnetron sputtering as a conductive window layer 160.

[0087] Step S8: Prepare Ni / Al top gate electrode 170.

[0088] In step S8, a 20 nm thick Ni and a 2 μm thick Al are sequentially prepared as the top gate electrode 170 using a vacuum thermal evaporation method in conjunction with a mask.

[0089] The specific embodiments of the preparation method of the copper-zinc-tin-sulfur-selenium solar cell 100 of the present invention have been described in detail above, but the present invention is not limited thereto. The specific embodiments of each step may vary depending on the circumstances. For example, in some embodiments, the substrate may be a flexible / rigid molybdenum foil, and the back electrode 110 layer may be omitted. In some embodiments, the absorber layer precursor film may be prepared by sputtering Cu, Zn, and Sn metal stacks. In some embodiments, the precursor film may be subjected to sulfidation treatment, where x = 1, and the resulting absorber layer is a copper-zinc-tin-sulfur (CZTS) thin film. In some embodiments, the buffer layer 130 may be a (Zn,Cd)S, (Zn,Mg)O, or other thin films. In some embodiments, the interface modification layer 150 may be selected from other crown ethers, thiols, phosphonates, or amine organic materials. In some embodiments, the conductive window layer 160 may be aluminum-doped zinc oxide (AZO).

[0090] The foregoing has described various embodiments of the copper-zinc-tin-sulfur-selenium solar cell with a ZnO-R window layer prepared by solution method and its preparation method. The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0091] The following embodiments use a copper-zinc-tin-sulfur-selenium solar cell as an example.

[0092] Examples 1 to 10

[0093] In these embodiments, the ZnO-R window layer 140 and the CZTSSe solar cell 100 are prepared by the following steps:

[0094] (1) A Mo back electrode 110 is prepared on a sodium-calcium glass substrate 180 according to the method and process parameters described in step S1 above.

[0095] (2) CZTS are sequentially prepared on the Mo back electrode 110 according to the aforementioned steps S2 to S4. x Se1-x Absorbing layer 120 and buffer layer 130.

[0096] (3) The solution ZnO-R window layer 140 is prepared according to the aforementioned step S5. The solution ZnO-R window layer 140 is prepared by sol-gel method or nanocrystal method, and the thickness of the solution ZnO-R window layer 140 is controlled by controlling the concentration of the precursor liquid. The specific process parameters of each embodiment are shown in Table 1.

[0097] (4) Prepare the interface modification layer 150 according to the aforementioned step S6. The interface modification layer is 18 crown ether 6, the precursor solution concentration is about 1 mg / mL, and the film thickness is about 5 nm. The specific differences are shown in Table 1.

[0098] (5) In accordance with the aforementioned steps S7 to S8, an ITO conductive window layer 160 and a Ni / Al top grid electrode 170 are sequentially prepared on the interface modification layer 150 to obtain a complete copper-zinc-tin-sulfur-selenium solar cell 100.

[0099] Table 1

[0100]

[0101] Comparative Examples 1 to 3

[0102] The only difference between Comparative Examples 1 to 3 and Examples 1 to 10 is that a ZnO layer was prepared by sputtering to replace the solution-processed ZnO-R window layer 140 and interface modification layer 150.

[0103] The performance parameters of the devices prepared in Examples 1-10 and Comparative Examples 1-3 are shown in Table 2.

[0104] Table 2

[0105]

[0106] Examples 11 to 22

[0107] In these embodiments, a copper-zinc-tin-sulfur-selenium solar cell 100 with a ZnO-R window layer 140 is prepared by the following steps:

[0108] (1) A Mo back electrode 110 is prepared on a sodium-calcium glass substrate 180 according to the method and process parameters described in step S1 above.

[0109] (2) CZTS are sequentially prepared on the Mo back electrode 110 according to the aforementioned steps S2 to S4. x Se 1-x Absorbing layer 120 and buffer layer 130.

[0110] (3) Prepare the solution-based ZnO-R window layer 140 according to the aforementioned step S5, using the sol-gel method, with a precursor solution concentration of approximately 20 mg / mL and a film thickness of approximately 30 nm. Specific process parameters are shown in Table 3.

[0111] (4) Prepare the interface modification layer 150 according to the aforementioned step S6. The materials selected for the interface modification layer 150 are 18 crown ether 6, phenylethyl mercaptan, phenylphosphonic acid, and polyethyleneimine, respectively. The thickness of the interface modification layer 150 is controlled by adjusting the solution concentration. Specific process parameters are shown in Table 3.

[0112] (5) In accordance with the aforementioned steps S7 to S8, an ITO conductive window layer 160 and a Ni / Al top grid electrode 170 are sequentially prepared on the interface modification layer 150 to obtain a complete copper-zinc-tin-sulfur-selenium solar cell 100.

[0113] Table 3

[0114]

[0115] Comparative Examples 4 to 6

[0116] The only difference between Comparative Examples 4 to 6 and the aforementioned Examples 11 to 22 is that no interface decoration layer 150 is added.

[0117] The performance parameters of the devices prepared in Examples 11-22 and Comparative Examples 4-6 are shown in Table 4.

[0118] Table 4

[0119]

[0120] As can be seen from Tables 1 to 4, the present invention introduces a solution-processed ZnO-R window layer 140 (sol-gel method or nanocrystalline method) and an interface modification layer 150 (crown ether, thiol, phosphonic acid or amine) between the buffer layer 130 and the conductive window layer 160 to replace the original sputtered ZnO layer, which can effectively improve the device performance of the copper-zinc-tin-sulfur-selenium solar cell 100. On the one hand, the introduction of the solution-processed ZnO-R window layer 140 to replace sputtered ZnO significantly improves the open-circuit voltage of the solar cell 100. The main reason is that the solution method can be used to prepare the ZnO-R window layer on the CZTSSe / CdS substrate without damage, completely preserving the ordered lattice interface with the absorber layer obtained during water bath deposition of the buffer layer. At the same time, it retains the high crystallinity of the CdS layer, avoids bombardment damage caused by the sputtering process, eliminates defect formation from the source, reduces carrier recombination, and thus improves the open-circuit voltage.

[0121] On the other hand, the introduction of the interface modification layer 150 can further improve the fill factor of the solar cell 100. As can be seen from the data in the table, the optimal configuration is approximately 20 mg / mL of solution-processed ZnO-R window layer 140 and approximately 1 mg / mL of 18-crown ether-6 interface modification layer 150.

[0122] The copper-zinc-tin-sulfur-selenium solar cell 100 prepared by the above steps has a work function of 4.21 eV for the CdS buffer layer 130, a work function of 4.57 eV for the solution-based ZnO-R window layer 140 (taking the sol-gel method as an example), and the work function of the solution-based ZnO-R window layer 140 can be continuously adjusted between 4.57 eV and 4.35 eV after adding the interface modification layer 150 (taking 18 crown ether 6 as an example), and the work function of the ITO conductive window layer 160 is 4.6 eV.

[0123] The band structure of the copper-zinc-tin-sulfur-selenium solar cell 100 with solution-processed ZnO-R window layer 140 prepared above was compared under different solution concentrations of interface modification layer 150. Figures 3a to 3c As shown.

[0124] Reference Figures 3a to 3c As shown, narrow potential barriers of approximately 10 nm thickness exist at both the CdS / ZnO and ZnO / ITO interfaces, collectively blocking electron transport in the conduction band. Theoretically, for narrow barriers less than 0.25 eV, electrons can tunnel through, reducing the impact on charge transport. When the work function of the solution-grown ZnO-R window layer 140 is adjusted by the interface modification layer 150 to 4.57 eV or 4.35 eV, one of the barriers significantly increases, greatly reducing the probability of electron tunneling, thus increasing series resistance and decreasing the device's fill factor. However, when the work function of the solution-grown ZnO-R window layer 140 is adjusted by the interface modification layer 150 to 4.43 eV, the two barriers are more balanced, achieving band matching between the solution-grown ZnO-R window layer 140 and the preceding and following layers, allowing electrons to pass through quickly, improving the device's fill factor, and thus increasing device efficiency.

[0125] In this embodiment of the invention, by introducing a solution-prepared ZnO-R window layer 140, the bombardment of the pn junction substrate (absorber layer 120 / buffer layer 130) by particles with kinetic energies exceeding 100 eV during magnetron sputtering is avoided, thus protecting the integrity of the pn junction lattice. This reduces interface defects in the depletion region, decreases carrier recombination, and results in a copper-zinc-tin-sulfur-selenium solar cell 100 with a high open-circuit voltage. Simultaneously, by introducing an interface modification layer 150, the electrical performance of the solution-prepared ZnO-R window layer 140 is improved, and the band structure of the solution-prepared ZnO-R window layer 140 is optimized to match the preceding and following layers, accelerating electron transport capability and thereby obtaining a copper-zinc-tin-sulfur-selenium solar cell with a high fill factor.

[0126] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0127] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A copper-zinc-tin-sulfur-selenium solar cell, comprising a back electrode and CZTS stacked sequentially from bottom to top. x Se 1-x (0≤x≤1) an absorption layer, a buffer layer, a ZnO window layer, a conductive window layer, and a top gate electrode, characterized in that, The ZnO window layer was prepared by a solution method; The copper-zinc-tin-sulfur-selenium solar cell further includes an interface modification layer located between the ZnO window layer and the conductive window layer, the interface modification layer being prepared by a solution method; The thickness of the interface modification layer is 1 ~ 20 nm, the material of the interface modification layer is 18-crown ether-6, and the solution concentration of 18-crown ether-6 is 0.1 ~ 10 mg / mL; The conductive window layer is made of indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO).

2. The copper-zinc-tin-sulfur-selenium solar cell according to claim 1, characterized in that, The thickness of the ZnO window layer is 1 ~ 100 nm.

3. The copper-zinc-tin-sulfur-selenium solar cell according to claim 1, characterized in that, The ZnO window layer is prepared from ZnO sol-gel or ZnO nanocrystal colloidal solution, wherein the concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution is 0.1 ~ 100 mg / mL.

4. The copper-zinc-tin-sulfur-selenium solar cell according to claim 3, characterized in that, The concentration of the ZnO sol-gel or ZnO nanocrystal colloidal solution is 20~50 mg / mL.

5. The copper-zinc-tin-sulfur-selenium solar cell according to claim 1, characterized in that, The concentration of the 18-crown ether-6 solution is 0.5 ~ 1 mg / mL.

6. The copper-zinc-tin-sulfur-selenium solar cell according to any one of claims 1-5, characterized in that, The solution method includes spin coating, blade coating, or spray coating.

7. The copper-zinc-tin-sulfur-selenium solar cell according to any one of claims 1-5, characterized in that, The material of the back electrode is molybdenum; The CZTS x Se 1-x (0≤x≤1) The absorption layer contains one or more of the following elements for doping or alloying: Ag, Cd, Ge and alkali metals; The material of the buffer layer is one or more of cadmium sulfide, zinc cadmium sulfide (Zn,Cd)S and zinc magnesium oxide (Zn,Mg)O. The top gate electrode is a nickel / aluminum bilayer electrode, an aluminum electrode, or a silver electrode.

8. A method for preparing a copper-zinc-tin-sulfur-selenium solar cell according to any one of claims 1-7, comprising: The back electrode and CZTS of the solar cell are fabricated sequentially from bottom to top. x Se 1-x An absorber layer, a buffer layer, a ZnO window layer, an interface modification layer, a conductive window layer, and a top gate electrode, characterized in that the ZnO window layer is prepared in situ using a solution method.

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