Superlens-based CZTS-based single crystal solar cell and preparation method and application thereof

Abstract

The invention relates to the technical field of micro-nano structure processing and solar cells, in particular to a super-lens-based CZTS-based single-crystal solar cell and a preparation method and application of the super-lens-based CZTS-based single-crystal solar cell. Large-size CZTS-based single crystal particles are closely and uniformly arranged according to an array and then bonded into a layer through transparent glue such as epoxy resin, the two faces are ground and polished, all single crystal faces are exposed, then a CZTS-based light absorption layer is formed, and then a Mo film is prepared on one face of the CZTS-based light absorption layer through a sputtering method to serve as a back electrode. And preparing a buffer layer CdS, a window layer i-ZnO and the like on the other surface of the single crystal CZTS-based light absorption layer by using a CBD method and a sputtering method respectively. According to the CZTS-based single-crystal solar cell, incident light is more efficiently focused on the crystal face of the CZTS-based single-crystal particles through the super-lens array, the efficiency of the CZTS-based single-crystal solar cell is improved, and a design method is provided for preparing the high-efficiency CZTS-based single-crystal solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nanostructure processing and solar cell technology, and in particular to a CZTS-based single-crystal solar cell based on a superlens, and a preparation method and application thereof. Background Art

[0002] Cu2ZnSnS4 (CZTS) materials hold broad application prospects in photocatalysis, photodetection, and thin-film solar cells due to their tunable direct band gap, nontoxicity, abundance, and high absorptivity. However, the actual photoelectric conversion efficiency (PCE) of CZTS materials is often lower than theoretically predicted. This is primarily due to the presence of numerous bulk defects, defect clusters, and surface defects, which limit the harvesting of solar light and the transport of photogenerated electrons. Therefore, element substitution—replacing atoms in the original absorber with atoms of other elements—is being explored to adjust the defect density and improve application performance. For example, Ag substitution can significantly reduce Cu-Zn antisite defects in CZTS, thereby increasing the open-circuit voltage of thin-film solar cells. However, current element substitution methods offer only limited improvements in the performance of CZTS material systems, with actual PCEs remaining far below theoretical values. A key reason for this is that the CZTS structures used for research into improved performance are typically thin films composed of tiny grains, which are difficult to grow. The photogenerated carriers between these tiny grains are strongly influenced by longitudinal interface scattering, surface defects, and defect clusters. Therefore, using large-sized CZTS single crystals to create fully vertically monocrystalline solar cells can reduce interfacial effects and thus improve solar cell efficiency. However, due to the large number of intergranular gaps in the arrangement of large CZTS single crystals, incident light energy is wasted when it is directed to these gaps. New strategies are urgently needed to avoid this waste of incident light energy and further increase photoelectric conversion efficiency.

[0003] Metalens are artificial micro-nano optical antennas with unique electromagnetic properties arranged in a specific pattern to form a quasi-two-dimensional planar lens structure. They can flexibly control parameters such as the phase, polarization, and amplitude of incident light, and have important applications in super-resolution imaging, achromatic lenses, and holographic optics. Planar metalens not only break through the diffraction limit of traditional optical lenses, but also facilitate integration due to their quasi-two-dimensional structure, providing a solution for the miniaturization and integration of optical lenses. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a CZTS-based single-crystal solar cell based on a superlens, and a preparation method and application thereof, which overcomes the problem that the incident light in the gaps between the grains of the single-crystal CZTS-based cell cannot be utilized.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a CZTS-based single-crystal solar cell based on a superlens, comprising the following steps:

[0007] 1) Arranging CZTS-based single crystal particles tightly and evenly in a periodic array and bonding them into a layer with transparent glue, and polishing both sides to expose all single crystal faces to obtain a CZTS-based light absorption layer;

[0008] 2) preparing a Mo thin film on one side of the CZTS-based light absorption layer obtained in step 1) as a back electrode, and sequentially preparing a buffer layer CdS and a window layer i-ZnO on the other side;

[0009] 3) preparing a superlens array on the i-ZnO window layer by a micro-nanostructure processing method according to the size and array of the CZTS-based single crystal particles in step 1);

[0010] 4) sequentially preparing an AZO film and a metal gate electrode on the superlens array obtained in step 3) to obtain a CZTS-based single crystal solar cell based on a superlens.

[0011] Preferably, the size of the CZTS-based single crystal particles in step 1) is 0.1 mm to 2 cm;

[0012] The thickness of the CZTS-based light absorption layer is 100 μm to 3 mm.

[0013] Preferably, the thickness of the Mo film in step 2) is 2 μm.

[0014] Preferably, the thickness of the buffer layer CdS in step 2) is 80 nm.

[0015] Preferably, the thickness of the i-ZnO window layer in step 2) is 400 nm.

[0016] Preferably, the superlens in the superlens array of step 3) is composed of structural units consisting of metal nanorods and dielectric nanorods with a high dielectric constant arranged in a ring structure, with the metal nanorods on the outside and the dielectric nanorods with a high dielectric constant on the inside;

[0017] The material of the metal nanorods includes one or more of gold, silver, aluminum and copper, and the high dielectric constant dielectric nanorods include one or more of silicon, silicon oxide, aluminum oxide and titanium oxide;

[0018] The length of the metal nanorod and the medium nanorod with a high dielectric constant are both 40 to 500 nm, the width is both 30 to 500 nm, and the height is both 30 to 100 nm.

[0019] Preferably, the superlens in the superlens array of step 3) is a dielectric superlens with focusing ability formed by an arrangement and combination of high dielectric constant dielectric nanorod unit structures, wherein the high dielectric constant dielectric nanorods include one or more of silicon, silicon oxide, aluminum oxide and titanium oxide; the unit structure has a length of 80 to 150 nm, a width of 40 to 80 nm, and a height of 500 nm, and the unit structure is arranged in a periodic manner with a period of 200 to 600 nm, and has a certain rotation, and the rotation angle range is 10-180°.

[0020] Preferably, the thickness of the AZO film in step 4) is 1 μm.

[0021] The present invention also provides a CZTS-based single crystal solar cell based on a superlens prepared by the preparation method described in the above technical solution.

[0022] The present invention also provides the application of the CZTS-based single crystal solar cell based on the super lens described in the above technical solution in improving the efficiency of the CZTS-based single crystal solar cell.

[0023] Combining an optical metalens with single-crystal solar cells is an effective method for further improving single-crystal solar cells. The optical metalens can focus incident light that would otherwise fall between the interstices of the single-crystal particles and be wasted onto the crystal surfaces of the single-crystal particles, allowing all incident light to participate in the photoelectric conversion process. The metalens improves the photoelectric conversion performance of the cell by increasing the utilization of incident light, while the single-crystal particles improve the photoelectric conversion efficiency of the cell by reducing interface scattering, surface defects, and defect clusters.

[0024] This invention utilizes the focusing power of a superlens to improve the efficiency of CZTS-based single-crystal solar cells. Large-sized CZTS-based single-crystal particles are tightly and evenly arranged in an array using a transparent adhesive such as epoxy resin to form a single-crystal solar light absorption layer with no grain boundaries in the longitudinal direction. A structural unit composed of metal nanorods and high-dielectric-constant dielectric nanorods is arranged in a ring configuration to form a superlens with a focusing function. The metal nanorods are positioned on the outside of the structural unit and the dielectric nanorods on the inside. The combination of these two forms a high-efficiency CZTS-based single-crystal solar cell that efficiently utilizes incident light without the influence of grain boundary transmission recombination.

[0025] Beneficial effects of the present invention:

[0026] 1. The present invention is based on large-sized CZTS-based single crystal particles, which greatly avoids the loss of carriers transmitted between tiny grains.

[0027] 2. The superlens described in the present invention can be jointly adjusted using metal nanorods and high-dielectric-constant dielectric nanorods. The metal nanorods themselves have the ability to focus light, and the high-dielectric-constant dielectric nanorods can adjust the scattering angle of the metal nanorods to the incident light, providing greater control and design freedom.

[0028] 3. The superlens described in the present invention can focus all incident light on the absorption surface of the CZTS-based single crystal particles, maximizing the utilization of incident sunlight. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0030] Figure 1 A CZTS-based single-crystal solar cell based on a superlens designed for the method of the present invention;

[0031] Figure 2 Large-sized CZTS-based single crystal particles arranged in a periodic array designed for the method of the present invention;

[0032] Figure 3 A periodic array of superlenses designed for the method of the present invention;

[0033] Figure 4 The metal / dielectric super lens units designed for the method of the present invention are arranged to rotate around concentric circles at a certain angle, with a rotation angle range of 10-180°;

[0034] Figure 5 Demonstration of the light-gathering function of the metal / dielectric superlens unit designed for the method of the present invention;

[0035] Among them: 1. Mo electrode, 2. Single crystal CZTS-based light absorption layer, 3. CdS buffer layer, 4. i-ZnO window layer, 5. AZO thin film, 6. CZTS-based single crystal particles, 7. Super lens, 8. Metal nanorods, 9. Dielectric nanorods. DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing a CZTS-based single-crystal solar cell based on a superlens, comprising the following steps:

[0037] 1) Arranging CZTS-based single crystal particles tightly and evenly in a periodic array and bonding them into a layer with transparent glue, and polishing both sides to expose all single crystal faces to obtain a CZTS-based light absorption layer;

[0038] 2) preparing a Mo thin film on one side of the CZTS-based light absorption layer obtained in step 1) as a back electrode, and sequentially preparing a buffer layer CdS and a window layer i-ZnO on the other side;

[0039] 3) preparing a superlens array on the i-ZnO window layer by a micro-nanostructure processing method according to the size and array of the CZTS-based single crystal particles in step 1);

[0040] 4) sequentially preparing an AZO film and a metal gate electrode on the superlens array obtained in step 3) to obtain a CZTS-based single crystal solar cell based on a superlens.

[0041] The present invention arranges CZTS-based single crystal particles tightly and evenly in an array (two-dimensional rectangular periodic structure) and then bonds them into a layer with transparent glue. After grinding and polishing both sides to expose all single crystal faces, a CZTS-based light absorption layer is obtained. In the present invention, the CZTS-based single crystal particles preferably include all I2-II-IV-VI4 type compound semiconductors such as CZTS, CZTSe, CZTSSe, ACZTS, and CZTGS. In the present invention, the size of the CZTS-based single crystal particles is preferably 0.1 mm to 2 cm. In the present invention, the thickness of the CZTS-based light absorption layer is preferably 100 μm to 3 mm. In the present invention, the transparent glue is preferably epoxy resin transparent glue.

[0042] The present invention prepares a Mo film on one side of the obtained CZTS-based light absorption layer as a back electrode, and sequentially prepares a buffer layer CdS and a window layer i-ZnO on the other side. The present invention does not specifically limit the method for preparing the Mo film, and those skilled in the art can use conventional methods, such as sputtering. In the present invention, the thickness of the Mo film is preferably 2μm. The present invention preferably adopts the CBD method to prepare the buffer layer CdS. In the present invention, the thickness of the window layer i-ZnO is preferably 400nm. The present invention preferably adopts the sputtering method to prepare the window layer i-ZnO.

[0043] The present invention designs and processes a layout based on the size and array of CZTS-based single crystal particles directly from a distribution photograph. A superlens array is then fabricated on the i-ZnO window layer using micro-nanostructural processing methods, typically electron beam lithography. In the present invention, the superlenses in the superlens array have a focal length of 5 to 500 μm, with a focal spot characteristic of 0.3 to 2 μm. In the present invention, the superlenses in the superlens array are preferably composed of structural units consisting of metal nanorods and high-dielectric-constant dielectric nanorods arranged in a ring configuration, with the metal nanorods on the outside and the high-dielectric-constant dielectric nanorods on the inside. In the present invention, the metal nanorods are preferably made of one or more of gold, silver, aluminum, and copper, and the high-dielectric-constant dielectric nanorods are preferably made of one or more of silicon, silicon oxide, aluminum oxide, and titanium oxide. In the present invention, the metal nanorods and high-dielectric-constant dielectric nanorods are preferably both 40 to 500 nm in length, 30 to 500 nm in width, and 30 to 100 nm in height. In the present invention, the metalens in the metalens array are preferably composed of a high-dielectric-constant dielectric nanorod unit structure, each having light-concentrating properties. The high-dielectric-constant dielectric nanorods preferably comprise one or more of silicon, silicon oxide, aluminum oxide, and titanium oxide. The unit structures are preferably 80 to 150 nm long, 40 to 80 nm wide, and 500 nm high. The unit structures are arranged in a periodic pattern, preferably 200 to 600 nm, and exhibit a certain degree of rotation, with a rotation angle ranging from 10 to 180°.

[0044] The present invention sequentially deposits an AZO film and a metal gate electrode on the obtained superlens array using conventional techniques in the field of CZTS cells, thereby obtaining a CZTS-based single-crystal solar cell based on a superlens. In the present invention, the thickness of the AZO film is preferably 1 μm. In the present invention, the AZO film is preferably prepared by magnetron sputtering, sol-gel deposition, chemical vapor deposition, or the like.

[0045] The present invention also provides a CZTS-based single crystal solar cell based on a superlens prepared by the preparation method described in the above technical solution.

[0046] The present invention also provides the application of the CZTS-based single crystal solar cell based on the super lens described in the above technical solution in improving the efficiency of the CZTS-based single crystal solar cell.

[0047] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] like Figure 1-Figure 5As shown in the figure, a design method of CZTS-based single crystal solar cell based on super lens is shown in the figure:

[0050] S1. Approximately 0.4 cm long pure-phase CZTS single crystals were tightly and evenly arranged in a periodic array (a two-dimensional rectangular periodic structure) and bonded to a layer using an amine curing agent (m-phenylenediamine) and epoxy resin. Both sides were then polished to expose all single crystal faces to form a CZTS-based light absorption layer with a thickness of approximately 1 mm.

[0051] S2. A 2-μm Mo film was deposited as a back electrode on one side of the CZTS-based light-absorbing layer using conventional magnetron sputtering. An 80-nm buffer layer of CdS and a 400-nm window layer of i-ZnO were deposited on the other side of the single-crystal CZTS-based light-absorbing layer using conventional chemical bath deposition and magnetron sputtering, respectively.

[0052] S3. Based on the single crystal geometry and array, a processing layout was designed directly on the distribution photograph. Then, using micro-nanostructural fabrication methods such as electron beam lithography, a light-concentrating superlens array composed of gold and silicon nanorods was fabricated on the i-ZnO layer. The gold and silicon nanorods were both 100 nm long, 40 nm wide, and 30 nm high. The superlens had a focal length of 5 μm and a focal spot size of 1 μm.

[0053] S4. Finally, a 1 μm AZO film and a metal gate electrode are prepared on the superlens array described in S3 using conventional methods in the field to form a CZTS-based single-crystal solar cell based on a superlens.

[0054] The SCAPS-1D battery simulation tool calculates that the single-crystal solar cell obtained in this embodiment has a fill factor FF≈75%, an open circuit voltage Voc≈730mV, and a short circuit current Jsc≈35mA·cm-1 using non-polarized sunlight incident under the standard AM1.5 spectrum as the light source. -2 , the conversion efficiency η≈14%. The simulation results show that the surface superlens can effectively focus the incident light onto the single crystal particles, avoiding the waste of sunlight in the gaps between the grains, thereby improving the efficiency of the battery.

[0055] Example 2

[0056] A design method for CZTS-based single-crystal solar cells based on superlens:

[0057] S1. CZTS single crystal particles approximately 0.5 cm in length are tightly and evenly arranged in an array and bonded to a layer using an epoxy resin containing an amine curing agent (e.g., ethylenediamine, diethylenetriamine, triethylenetetramine, m-phenylenediamine, etc.). Both sides are then polished to expose all single crystal faces to form a CZTS-based light absorption layer with a thickness of approximately 1.2 mm.

[0058] S2. A 2-μm Mo film was deposited as a back electrode on one side of the CZTS-based light-absorbing layer using conventional magnetron sputtering. An 80-nm CdS buffer layer and a 400-nm i-ZnO window layer were deposited on the other side of the single-crystal CZTS-based light-absorbing layer using a chemical bath method and magnetron sputtering, respectively.

[0059] S3. Based on the single crystal geometry and array, a processing layout was designed directly on its distribution photograph. Then, a pure silicon oxide dielectric lens array was fabricated on the i-ZnO layer using micro-nanostructural processing methods, such as electron beam lithography. The unit structures were 120 nm long, 40 nm wide, and 500 nm high. The units were arranged in a periodic pattern with a period of 200 nm. Each unit structure could provide a phase variation of 0 to 2π, a focal length of 5 μm, and a focal spot size of 500 nm.

[0060] S4. Finally, a 1 μm AZO film and a metal gate electrode are prepared on the superlens array described in S3 using conventional methods in the field to form a CZTS-based single-crystal solar cell based on a superlens.

[0061] The SCAPS-1D battery simulation tool was used to calculate the fill factor FF≈70%, the open circuit voltage Voc≈700mV, and the short circuit current Jsc≈35mA·cm-1 of the single crystal solar cell obtained in this embodiment using non-polarized sunlight incident under the standard AM1.5 spectrum as the light source. -2 , conversion efficiency η≈13%.

[0062] Comparative Example 1

[0063] The experimental method is the same as that of Example 1, except that the metalens is not prepared on the i-ZnO layer. The simulation results show that the single crystal solar cell obtained in this comparative example has a fill factor FF≈25%, an open circuit voltage Voc≈150mV, and a short circuit current Jsc≈5mA·cm -2 , conversion efficiency η≈1.5%.

[0064] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a CZTS-based single crystal solar cell based on a superlens, characterized in that: The following steps are involved: 1) Arranging CZTS-based single crystal particles tightly and evenly in a periodic array and bonding them into a layer with transparent glue, and polishing both sides to expose all single crystal faces to obtain a CZTS-based light absorption layer; 2) preparing a Mo thin film on one side of the CZTS-based light absorption layer obtained in step 1) as a back electrode, and sequentially preparing a buffer layer CdS and a window layer i-ZnO on the other side; 3) preparing a superlens array on the i-ZnO window layer by a micro-nanostructure processing method according to the size and array of the CZTS-based single crystal particles in step 1); 4) sequentially preparing an AZO film and a metal gate electrode on the superlens array obtained in step 3) to obtain a CZTS-based single crystal solar cell based on a superlens.

2. The preparation method according to claim 1, characterized in that In the step 1), the size of the CZTS-based single crystal particles is 0.1 mm to 2 cm; The thickness of the CZTS-based light absorption layer is 100 μm to 3 mm.

3. The preparation method according to claim 1, characterized in that The thickness of the Mo film in step 2) is 2 μm.

4. The preparation method according to claim 1, characterized in that The thickness of the buffer layer CdS in step 2) is 80 nm.

5. The preparation method according to claim 1, characterized in that In the step 2), the thickness of the i-ZnO window layer is 400 nm.

6. The preparation method according to claim 1, characterized in that The superlens in the superlens array of step 3) is composed of structural units consisting of metal nanorods and high dielectric constant dielectric nanorods arranged in a ring structure, with the metal nanorods on the outside and the high dielectric constant dielectric nanorods on the inside; The material of the metal nanorods includes one or more of gold, silver, aluminum and copper, and the high dielectric constant dielectric nanorods include one or more of silicon, silicon oxide, aluminum oxide and titanium oxide; The length of the metal nanorod and the medium nanorod with a high dielectric constant are both 40 to 500 nm, the width is both 30 to 500 nm, and the height is both 30 to 100 nm.

7. The preparation method according to claim 1, characterized in that The superlens in the superlens array of step 3) is a dielectric superlens with focusing ability, which is composed of a high dielectric constant dielectric nanorod unit structure arranged and combined, and the high dielectric constant dielectric nanorods include one or more of silicon, silicon oxide, aluminum oxide and titanium oxide; the unit structure has a length of 80 to 150 nm, a width of 40 to 80 nm, and a height of 500 nm. The unit structure is arranged in a periodic manner with a period of 200 to 600 nm and has a certain rotation, and the rotation angle range is 10-180°.

8. The preparation method according to claim 1, characterized in that The thickness of the AZO film in step 4) is 1 μm.

9. A CZTS-based single crystal solar cell based on a superlens prepared by the preparation method according to any one of claims 1 to 8.

10. The CZTS-based single crystal solar cell based on the super lens according to claim 9 is used to improve the efficiency of the CZTS-based single crystal solar cell.

Images