Trans-lead-tin perovskite solar cell without hole transport layer and preparation method of trans-lead-tin perovskite solar cell

Abstract

The invention discloses a hole-transport-layer-free trans-lead-tin perovskite solar cell and a preparation method thereof. The structure of the solar cell sequentially comprises a halogen ion modified transparent ITO substrate, a lead-tin perovskite active layer, an electron transport layer, a hole blocking layer and a metal electrode from bottom to top, the halogen ion modification layer is formed by modifying the surface of the transparent ITO substrate through a halogenated hydrocarbon organic compound under the irradiation condition of an ultraviolet lamp; the chemical formula of the lead-tin perovskite active layer is CsxFA1-xPbySn1-yI3, FA is formamidine ion, x is more than or equal to 0.1 and less than or equal to 0.3, and y is more than or equal to 0.4 and less than or equal to 0.6; the electron transport layer is made of footballene C60, and the thickness of the electron transport layer is 20-50nm; the hole blocking layer is made of tin oxide SnO2, and the thickness of the hole blocking layer is 10-30 nm. The metal electrode is made of silver (Ag), and the thickness of the metal electrode is 100-150nm; through the synergistic effect of work function regulation, crystallization optimization, defect passivation and hole blocking, the bottlenecks of energy level mismatch, carrier transport blocking, poor stability and the like of an HTL-free structure are broken through, and multi-dimensional optimization of battery device structure simplification, cost reduction, efficiency improvement and stability enhancement is realized.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and more specifically, relates to an inverse lead-tin perovskite solar cell without a hole transport layer and its preparation method. Background Technology

[0002] Perovskite solar cells have become a research hotspot in the photovoltaic field due to the excellent performance of organometal halide semiconductor light-absorbing materials. Their working principle is as follows: After sunlight penetrates the transport layer and irradiates the perovskite layer, the perovskite absorbs photons with energy greater than its band gap, generating excitons. These excitons rapidly dissociate into free electrons and holes, which diffuse to the adjacent charge transport layer before recombination. Utilizing the favorable energy level alignment at the interface between the perovskite and the charge transport layer, the electron transport layer (ETL) and hole transport layer (HTL) efficiently extract electrons and holes, respectively. Finally, the charge carriers are collected by the electrodes at both ends and connected to an external circuit to form a usable photocurrent.

[0003] The current mainstream inverted perovskite solar cell structure is a conductive substrate / hole transport layer / perovskite layer / electron transport layer / metal electrode, i.e., a pin structure. However, existing hole transport layer (HTL) materials have significant defects, severely restricting industrialization. Taking the commonly used PEDOT:PSS as an example, its PSS chains are acidic and hydrophilic, which corrode the perovskite film and absorb moisture, accelerating the degradation of the perovskite layer and significantly shortening the device's lifespan. Furthermore, these HTL materials generally suffer from excessively high costs.

[0004] To address these issues, research has emerged in the field focusing on hole transport layer-free (HTL-free) solar cells. By allowing transparent electrodes to directly contact the perovskite layer, the device structure is simplified, migratable dopants and deliquescent components are reduced, thereby improving long-term stability. However, HTL-free single-junction solar cells still face several technical bottlenecks that urgently need to be overcome. (1) Sn in lead-tin perovskite thin films 2+ It is easily oxidized to Sn 4+ This disrupts the original crystal lattice structure and affects the basis of carrier transport. (2) The perovskite bulk phase and surface phase contain a large number of defects, especially surface defects, which severely hinder carrier transport and interfacial carrier transfer, resulting in a low open-circuit voltage ( ). V OC The decrease in fill factor (FF) and overall fill factor ultimately reduces the power conversion efficiency (PCE). (3) After removing the HTL between the transparent conductive oxide and the perovskite layer, the two form a direct Schottky contact. A large number of defect states are generated at the interface and Fermi level pinning is triggered, which in turn forms a depletion region and band bending. When the band bends downward, a hole transport barrier is formed at the interface, which significantly hinders hole extraction and collection. (4) The absence of HTL causes the battery to lose the key electron blocking layer, resulting in the loss of interfacial selectivity. Electrons can easily diffuse to the anode interface and recombine with holes non-radiatively, causing a large loss of photogenerated carriers. (5) The combined effects of the above-mentioned interface defects, nonradiative recombination, and quasi-Fermi level pinning inhibit the degree of quasi-Fermi level splitting, further leading to open-circuit voltage loss, making it difficult to construct a low-impedance hole extraction channel between the transparent ITO electrode and the narrow bandgap lead-tin perovskite valence band. (6) Under the HTL-free structure, the perovskite active layer needs to be deposited directly from the solution phase onto the ITO electrode. The wettability and other properties of the growth substrate determine the nucleation, growth and final morphology of the perovskite crystal. The difference in properties between the ITO substrate and the original HTL substrate will significantly change the perovskite crystallization process and affect the grain size, crystal morphology and film quality.

[0005] In summary, for narrow bandgap Pb-Sn single-junction perovskite solar cells, current research focuses on energy level matching, interface passivation, and Sn... 2+ Significant technological gaps remain in addressing the synergistic issues of oxidation suppression and long-term stability. Therefore, there is an urgent need to develop a narrow-bandgap lead-tin perovskite solar cell and its fabrication method that eliminates the need for traditional high-level tandem solar cells (HTLs) and combines high-efficiency energy level alignment, interface defect passivation, SnO2 stabilization, and long-term environmental stability, in order to advance the research and industrial application of this type of photovoltaic device. Summary of the Invention

[0006] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a hole transport layer-free inverse lead-tin perovskite solar cell and its fabrication method. By removing the traditional hole transport layer (HTL) and modifying a transparent ITO substrate with haloalkanes under UV irradiation to form a halide-ion modified layer, the acid corrosion, hygroscopic degradation, and high cost problems of traditional HTL materials (such as PEDOT:PSS) are effectively avoided. Simultaneously, the work function of the ITO substrate is precisely controlled to match the work function of the lead-tin perovskite active layer, achieving efficient hole extraction without HTL, simplifying the device structure, and reducing fabrication costs. A vacuum pump method is used to replace the traditional anti-solvent method for preparing the lead-tin perovskite active layer, improving the uniformity and density of the thin film crystallization. A dual passivation strategy combining p-FPEACl and EDAI2 synergistically passivates various defects on the perovskite surface, reducing carrier transport obstacles and non-radiative recombination, thereby increasing the cell's open-circuit voltage. V OCThe study focuses on filling factor (FF) and power conversion efficiency (PCE). A SnO2 hole-blocking layer is fabricated on top of the electron transport layer using atomic layer deposition (ALD) technology. This utilizes the energy level characteristics of SnO2 to prevent holes from diffusing into the electron transport layer, reducing non-radiative recombination. Furthermore, SnO2's excellent density isolates oxygen and water vapor, inhibiting Sn²⁺ oxidation and perovskite layer degradation, thus improving the long-term stability of the device. Through the synergistic effects of work function regulation, crystal optimization, defect passivation, and hole blocking, the study overcomes the bottlenecks of energy level mismatch, carrier transport obstruction, and poor stability in HTL-free structures. This achieves multi-dimensional optimization of the battery device structure, including structural simplification, cost reduction, efficiency improvement, and enhanced stability, providing a feasible path for the industrialization of narrow-bandgap lead-tin perovskite solar cells.

[0007] To achieve the above objectives, one aspect of the present invention provides an inverted lead-tin perovskite solar cell without a hole transport layer, wherein the solar cell structure, from bottom to top, comprises: a halide-modified transparent ITO substrate, a lead-tin perovskite active layer, an electron transport layer, a hole blocking layer, and a metal electrode. The halide-modified layer is formed by modifying the surface of a transparent ITO substrate with halide organic compounds under ultraviolet light irradiation. It is used to regulate the work function of the ITO substrate so that the work function of ITO matches that of the lead-tin perovskite active layer. The chemical formula of the lead-tin perovskite active layer is Cs. x FA 1-x Pb y Sn 1-y I3, where FA is formamidinium ion. x The value range is 0.1≤ x ≤0.3, y The value range is 0.4≤ y ≤0.6; The electron transport layer material is fullerene C. 60 The thickness is 20-50nm; The hole blocking layer is made of tin oxide (SnO2) with a thickness of 10-30 nm; the metal electrode is made of silver (Ag) with a thickness of 100-150 nm.

[0008] Furthermore, the halogenated hydrocarbon organic compound is one of chlorobenzene CB, o-dichlorobenzene o-DCB, and bromobenzene BB, with a purity ≥99.8%.

[0009] Furthermore, the ultraviolet lamp has a wavelength of 300-400nm, a power of 5-15W, and an irradiation time of 30-90min.

[0010] A second aspect of the present invention provides a method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer, comprising the following steps: S1. Cleaning and pretreatment of transparent ITO substrate: Cut the transparent glass substrate with ITO pattern retained after laser engraving, and clean it with detergent, deionized water, isopropanol and alcohol in sequence by ultrasonic cleaning. After drying with nitrogen, treat with ultraviolet ozone. S2. Preparation of ITO modified layer: In a nitrogen atmosphere glove box, the pretreated ITO substrate was placed under a UV irradiation device, o-dichlorobenzene was added dropwise to completely immerse the substrate, hydrogen peroxide solution was added dropwise, UV lamp was turned on for irradiation, and then residual o-DCB was removed by heating on a hot stage. S3, Preparation of lead-tin perovskite active layer: according to chemical formula Cs x FA 1-x Pb y Sn 1-y I3, 0.1≤ x ≤0.3, 0.4≤ y Weigh the raw materials at a stoichiometric ratio of ≤0.6, add DMF and DMSO solvents to prepare a perovskite precursor solution, shake and filter; in a nitrogen glove box, drop the precursor solution onto the modified ITO substrate, spread the precursor solution evenly on the substrate surface in a vacuum spin coater, and then obtain the lead-tin perovskite active layer by vacuuming and annealing. S4. Surface defect passivation: Prepare p-FPEACl solution and EDAI2 solution respectively. Place the annealed device in a vacuum spin coater and drop p-FPEACl solution and EDAI2 solution onto the surface of the perovskite film in sequence to obtain the passivated lead-tin perovskite active layer. S5. Preparation of electron transport layer: C60 is deposited on the surface of the passivated lead-tin perovskite active layer film using vacuum evaporation equipment to obtain electron transport layer. S6. Preparation of hole blocking layer: Using an atomic layer deposition device, water and tetramethylaminotin (TDMSn) were used as raw materials to deposit 10-30 nm SnO2 on the surface of the electron transport layer to obtain a hole blocking layer. S7. Preparation of metal electrode: The battery device after step S6 is transferred to a vacuum coating machine, and a 100-150 nm thick metal Ag is deposited on the surface of the hole blocking layer to obtain an inverted lead-tin perovskite solar cell without a hole transport layer.

[0011] Furthermore, the average water oxygen content in the nitrogen atmosphere during step S2 is ≤0.1ppm; In step S2, the wavelength of the ultraviolet lamp is 300-400nm, the power is 5-15W, and the irradiation time is 30-90min; the heating temperature of the hot table is 70-100℃, and the heating time is 5-15min.

[0012] Furthermore, the raw materials in step S3 include CsI, FAI, SnI2, PbI2, Gly•HCl, SnF2, MASCN, and tin granules.

[0013] Further, the preparation of EDAI2 solution in step S4 includes: weighing 0.5-1 mg of EDAI2, adding 500 μL each of isopropanol (IPA) and toluene, stirring under heating conditions of 70-80℃ for 6-12 h, and then filtering with a 0.22 μm polytetrafluoroethylene filter head to obtain a colorless and transparent EDAI2 solution. The preparation of p-FPEACl solution involves weighing 1.5-2 mg of p-FPEACl, adding 500 μL each of IPA and toluene, shaking for 6-12 h, and then filtering with a 0.22 μm polytetrafluoroethylene filter to obtain a colorless and transparent p-FPEACl solution.

[0014] Furthermore, the vapor deposition conditions in step S5 are: vacuum degree ≤1×10 −3 Pa; temperature 500-520℃; rate 0.1-0.2 Å / s; vapor deposition thickness 20-50 nm.

[0015] Furthermore, the vacuum degree in step S7 is ≤1×10⁻⁶. −3 Pa; voltage 1.0-1.2V; current 150-160A; speed 1.0-1.5Å / s.

[0016] Furthermore, the battery device structure is as follows: Glass / Cl-ITO / Cs x FA 1-x Pb y Sn 1-y I3 / C 60 / SnO2 / Ag; where 0.1≤ x ≤0.3, 0.4≤ y ≤0.6.

[0017] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: (1) The hole transport layer-free inverse lead-tin perovskite solar cell and its preparation method of the present invention can solve the defects of traditional hole transport layers, reduce costs and improve stability. By removing the traditional hole transport layer (HTL) and using haloalkanes to modify the transparent ITO substrate under ultraviolet light to form a halide-modified layer, the acid corrosion, hygroscopic degradation and high cost problems of traditional HTL materials (such as PEDOT:PSS) are effectively avoided. Among them, the halide-modified layer can precisely control the work function of the ITO substrate to match the work function of the lead-tin perovskite active layer, achieving efficient hole extraction without HTL. This simplifies the device structure, reduces migratable dopants and deliquescent components, significantly reduces the preparation cost, and avoids interfacial corrosion between the HTL and the perovskite layer, thus significantly extending the device lifespan.

[0018] (2) The hole transport layer-free inverse lead-tin perovskite solar cell and its preparation method of the present invention can optimize the quality of perovskite thin films and improve carrier transport efficiency. On the one hand, the vacuum pump method is used to replace the traditional anti-solvent method to prepare the lead-tin perovskite active layer. This method can control the crystallization kinetics to make the perovskite precursor solution nucleate synchronously as a whole, which can significantly improve the uniformity and density of film crystallization. At the same time, it avoids the introduction of new solvents, simplifies the interfacial chemical environment, and reduces bulk defects. On the other hand, through the dual passivation strategy of p-FPEACl and EDAI2, the strong electronegativity of fluorine atoms in p-FPEACl and the interaction between amino groups and the perovskite surface, the coordination bond between the double amino groups of EDAI2 and lead ions, and the compensation effect of iodine ions on iodine vacancies are used to synergistically passivate various defects on the perovskite surface, reduce carrier transport obstacles, reduce non-radiative recombination, and thus improve the open-circuit voltage of the cell. V OC ), fill factor (FF) and power conversion efficiency (PCE).

[0019] (3) The inverse lead-tin perovskite solar cell without a hole transport layer of the present invention and its preparation method can suppress carrier reverse diffusion and enhance device stability; in the electron transport layer (C 60 The upper layer uses atomic layer deposition (ALD) technology to prepare a 10-30 nm thick SnO2 hole-blocking layer. The conduction band bottom energy level of SnO2 is close to that of perovskite, which can ensure efficient electron transport. Its valence band top energy level is much higher than that of perovskite, which can form an effective energy barrier to prevent holes from diffusing into the electron transport layer and significantly reduce electron-hole nonradiative recombination. At the same time, the SnO2 film prepared by ALD technology has excellent density and can isolate the lower film from oxygen and water vapor in the air environment, effectively inhibiting Sn²⁺ oxidation (avoiding lattice structure destruction) and perovskite layer degradation, significantly improving the long-term environmental stability of the device.

[0020] (4) The hole transport layer-free inverse lead-tin perovskite solar cell and its preparation method of the present invention can overcome the bottleneck of HTL-free structure and achieve multi-dimensional performance synergistic improvement: In response to the problems of Fermi level pinning, hole transport barrier and quasi-Fermi level splitting suppression caused by direct Schottky contact between transparent ITO and perovskite layer in HTL-free structure, the present invention constructs a low-impedance hole extraction channel by controlling the work function of halide ion modified layer to alleviate energy level mismatch; combined with the crystallization optimization of vacuum pumping method and the defect suppression of double passivation strategy, the problems of carrier transport obstruction and open-circuit voltage loss are solved in a coordinated manner; and with the reverse diffusion suppression and environmental isolation effect of SnO2 hole blocking layer, the multi-dimensional synergistic optimization of device structure simplification, cost reduction, efficiency improvement and stability enhancement is finally achieved, providing a feasible technical path for the industrial application of narrow bandgap lead-tin perovskite solar cells. Attached Figure Description

[0021] Figure 1 A schematic diagram of a traditional inverted single-junction perovskite solar cell; Figure 2 This is a schematic diagram of the structure of an inverted lead-tin perovskite solar cell without a hole transport layer according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a solar cell fabricated using a hole transport layer-free inverted lead-tin perovskite solar cell fabrication method according to an embodiment of the present invention. Figure 4 This is a schematic diagram showing the performance test results of an inverted lead-tin perovskite solar cell device without a hole transport layer, prepared using the method of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Please refer to Figure 1 This is a schematic diagram of a traditional inverted single-junction perovskite solar cell structure; based on the technical problems existing in the background technology, such as Figure 2 As shown, one aspect of the present invention provides an inverse lead-tin perovskite solar cell without a hole transport layer, the structure of which, from bottom to top, comprises: a halide-modified transparent ITO substrate, a lead-tin perovskite active layer, an electron transport layer, a hole blocking layer, and a metal electrode; the halide-modified layer is formed by modifying the surface of the transparent ITO substrate with a halide-based organic compound under ultraviolet light irradiation; the chemical formula of the lead-tin perovskite active layer is Csx FA 1- x Pb y Sn 1-y I3, where FA is formamidinium ion (CH(NH2)2) + ), x The value range is 0.1≤ x ≤0.3, y The value range is 0.4≤ y ≤0.6; the electron transport layer material is fullerene C 60 The thickness of the hole blocking layer is 20-50 nm; the hole blocking layer material is tin oxide (SnO2) with a thickness of 10-30 nm; the metal electrode material is silver (Ag) with a thickness of 100-150 nm; the halogenated hydrocarbon organic compound is one of chlorobenzene (CB), o-dichlorobenzene (o-DCB), and bromobenzene (BB), with a purity ≥99.8%; the wavelength of the ultraviolet lamp is 300-400 nm, the power is 5-15 W, and the irradiation time is 30-90 min.

[0024] The hole-transport layer-free inverse lead-tin perovskite solar cell of this invention adopts a five-layer core structure stacked sequentially from bottom to top. Each layer has a clearly defined function and works synergistically to form a highly efficient and stable photovoltaic device system. The bottom layer is a halide-modified transparent ITO substrate. This substrate is not traditional untreated ITO, but is obtained through a specific process: one of chlorobenzene CB, o-dichlorobenzene o-DCB, and bromobenzene BB with a purity ≥99.8% is used as a halide-based organic compound modifier. The surface of the transparent ITO substrate is modified under ultraviolet lamp irradiation conditions with a wavelength of 300-400nm and a power of 5-15W, and the irradiation time is controlled at 30-90min. During this modification process, o-dichlorobenzene molecules in… Under ultraviolet light induction, partial dissociation occurs, and the chlorine atoms contained therein can form stable chemical bonds with the hydroxyl groups (-OH) on the ITO surface, ultimately constructing a dense and uniform halide-modified layer on the ITO surface. The core function of this modified layer is to precisely control the work function of the ITO substrate. Since the work function of unmodified ITO is 4.6-4.7 eV, while the valence top work function of common lead-tin perovskite active layers is 5.0-5.5 eV, there is a significant energy level difference between the two. Direct contact would form a hole transport barrier, hindering hole extraction. After halide modification, the work function of the ITO substrate can be significantly increased to a range close to that of the lead-tin perovskite active layer, thereby eliminating the energy level mismatch problem and laying the foundation for efficient hole extraction.

[0025] Located atop the halide-modified ITO substrate is a lead-tin perovskite active layer, serving as the core light-absorbing and carrier-generating layer of the battery. The chemical formula of this lead-tin perovskite active layer is strictly limited to Cs. x FA 1-x Pby Sn 1-y I3, where FA is formamidinium ion (CH(NH2)2) + ), x The value range is 0.1≤ x ≤0.3, y The value range is 0.4≤ y ≤0.6; This formulation, through the control of the cation ratio of cesium (Cs) to formamidinium (FA) and the metal cation ratio of lead (Pb) to tin (Sn), can achieve precise adjustment of the perovskite band gap width, while ensuring the crystallinity and chemical stability of the material; among which, the optimal implementation method is as follows: x The value is 0.2. y A value of 0.5 corresponds to the chemical formula Cs. 0.2 FA 0.8 Pb 0.5 Sn 0.5 I3; Under this formulation, perovskite materials not only have a narrow bandgap characteristic that is compatible with the solar spectrum, which can fully absorb photons from the visible to near-infrared region, but also have excellent carrier mobility and crystal uniformity, which can efficiently generate and transport photogenerated carriers.

[0026] Above the lead-tin perovskite active layer is an electron transport layer, using fullerene C. 60 As a transport material, the thickness is controlled at 20-50nm. Fullerene has excellent electron transport performance. Its conduction band bottom level matches the conduction band bottom level of the lead-tin perovskite active layer very well. It can quickly receive electrons transferred from the perovskite layer and efficiently transport electrons to subsequent layer structures. At the same time, it can effectively block holes from diffusing towards the metal electrode and reduce carrier recombination.

[0027] Above the electron transport layer is a hole blocking layer, made of tin oxide (SnO2) with a thickness of 10-30 nm. This layer utilizes the characteristic that the top energy level of the SnO2 valence band is much higher than that of the perovskite valence band to form a significant energy barrier, further preventing holes from diffusing across the electron transport layer to the metal electrode and avoiding nonradiative recombination of electrons and holes at the interface. On the other hand, the dense SnO2 film also acts as a physical barrier, isolating external oxygen and water vapor from eroding the underlying perovskite active layer and improving the long-term stability of the device.

[0028] The top layer is a metal electrode, with silver (Ag) selected as the electrode material and a thickness set at 100-150nm. Silver has extremely high conductivity, which can efficiently collect electrons transferred from the hole blocking layer. At the same time, it has good chemical stability and is not easily oxidized or corroded during battery operation, which can ensure the long-term conductivity of the electrode and the overall reliability of the device.

[0029] Overall, this hole-transport layer-free inverted lead-tin perovskite solar cell, through material selection, process optimization, and parameter limitation of each layer, achieves multiple goals such as energy level matching, efficient carrier separation and transport, and improved device stability while removing the traditional high-cost, low-stability hole transport layer. It is a photovoltaic device structure with simplified structure and excellent performance.

[0030] A second aspect of the present invention provides a method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer, comprising the following steps: S1. Cleaning and pretreatment of the transparent ITO substrate: The transparent glass substrate with the ITO pattern retained in the center after laser etching is cut and ultrasonically cleaned sequentially with detergent, deionized water, isopropanol, and alcohol. After drying with nitrogen, it is treated with ultraviolet ozone. Specifically, this includes: The transparent glass substrate with a 10mm×25mm ITO pattern retained in the center after laser etching was cut into 25mm×25mm sizes. It was then ultrasonically cleaned sequentially with detergent, deionized water, isopropanol, and alcohol for 20-40 minutes each time to remove oil, dust, and other impurities from the ITO surface. After cleaning, the ITO substrate was dried in a high-speed nitrogen atmosphere and then placed in an ultraviolet ozone cleaner for 10 minutes to further remove organic impurities from the ITO surface. S2. Preparation of the ITO modified layer: In a nitrogen-atmospheric glove box, the pretreated ITO substrate was placed under a UV irradiation device, and o-dichlorobenzene (o-DCB) was added dropwise to completely immerse the substrate. Hydrogen peroxide solution was then added, and the substrate was irradiated with UV light for 30-90 minutes. Subsequently, the substrate was heated on a hot table at 70-100℃ for 5-15 minutes to remove residual o-DCB. Specifically, this includes: The ITO substrate pretreated in step S1 was placed under a UV irradiation device in a glove box (nitrogen atmosphere, water and oxygen content ≤0.1ppm). o-Dichlorobenzene (o-DCB) with a purity ≥99.8% was uniformly drop-coated onto the ITO substrate surface, ensuring complete immersion in the o-DCB environment. A few drops of hydrogen peroxide solution were then added. Subsequently, a UV lamp (wavelength 300-400nm, power 5-15W) was turned on to irradiate the o-DCB solution on the ITO substrate surface for 30-90 minutes. Under UV irradiation, the o-DCB molecules partially dissociated, and their chlorine atoms chemically bonded to the hydroxyl groups (-OH) on the ITO surface, forming a dense and uniform chlorine-modified layer. After irradiation, the ITO substrate was heated on a hot stage at 70-100℃ for 5-15 minutes to remove residual o-DCB, yielding a surface-modified ITO transparent glass substrate. S3, Preparation of lead-tin perovskite active layer: according to chemical formula Cs x FA1-x Pb y Sn 1-y I3, 0.1≤ x ≤0.3, 0.4≤ y Weigh the raw materials at a stoichiometric ratio ≤0.6, add DMF and DMSO solvents to prepare a perovskite precursor solution, shake and filter; in a nitrogen glove box, drop the precursor solution onto the modified ITO substrate, and spread the precursor solution evenly onto the substrate surface in a vacuum spin coater, then sequentially pass through vacuuming and annealing to obtain a lead-tin perovskite active layer; specifically including: According to the chemical formula Cs x FA 1-x Pb y Sn 1-y I3(0.1≤ x ≤0.3, 0.4≤ y In a stoichiometric ratio ≤0.6, weigh the following reagents sequentially: 51.96-155.88 mg CsI, 240.76-309.54 mg FAI, 298.02-447.02 mg SnI2, 368.81-553.21 mg PbI2, 3-5 mg Gly•HCl, 10-20 mg SnF2, 1-5 mg MASCN, and 5-15 mg tin granules. Then add 500-1000 μL of DMF and 0-500 μL of DMSO solvent to prepare a perovskite precursor solution. After shaking for 6-18 hours, use 0... The precursor solution was filtered through a .22μm polytetrafluoroethylene filter to obtain a clear, bright yellow solution. Subsequently, in a nitrogen glove box, 30-50μL of the prepared precursor solution was added dropwise to the center of the o-DCB-modified substrate using a pipette. The solution was then evenly spread onto the substrate surface using a vacuum spin coater at 3000-4000 rpm for 8-12 seconds. The glass was then quickly transferred to a vacuum pump and rapidly pumped for 20-30 seconds. Finally, the glass containing the film was transferred to a hot plate at 110-120℃ and annealed for 60-90 seconds to obtain a lead-tin perovskite active layer. S4. Surface Defect Passivation: Prepare p-FPEACl solution and EDAI2 solution respectively. Place the annealed device in a vacuum spin coater and sequentially drop the p-FPEACl solution and EDAI2 solution onto the perovskite film surface to obtain the passivated lead-tin perovskite active layer; specifically including: Weigh 0.5-1 mg of EDAI2, add 500 μL each of isopropanol (IPA) and toluene, stir at 70-80℃ for 6-12 h, and then filter through a 0.22 μm polytetrafluoroethylene filter to obtain a colorless and transparent EDAI2 solution; weigh 1.5-2 mg of p-FPEACl, add 500 μL each of IPA and toluene, shake for 6-12 h, and then filter through a 0.22 μm polytetrafluoroethylene filter to obtain a colorless and transparent p-FPEACl solution; Take 80-100 μL of p-FPEACl solution and 40-60 μL of LEDAI2 solution in sequence with a pipette. Place the annealed device in a vacuum spin coater and rotate it at 3000-4000 rpm for 20-30 seconds. During the rotation, slowly drop the two solutions onto the surface of the perovskite film to obtain the passivated lead-tin perovskite active layer. S5. Preparation of the electron transport layer: C is deposited on the surface of the passivated lead-tin perovskite active layer film using a vacuum evaporation device. 60 An electron transport layer is obtained; specifically, the evaporation conditions in step S5 are: vacuum degree ≤1×10 −3 Pa; temperature 500-520℃; rate 0.1-0.2 Å / s; vapor deposition thickness 20-50 nm; S6. Preparation of hole blocking layer: Using an atomic layer deposition device, water and tetramethylaminotin (TDMSn) were used as raw materials to deposit 10-30 nm SnO2 on the surface of the electron transport layer to obtain a hole blocking layer. S7. Preparation of metal electrodes: The battery device processed in step S6 is transferred to a vacuum coating machine, and a 100-150 nm thick layer of metallic Ag is deposited on the surface of the hole-blocking layer to obtain an inverted lead-tin perovskite solar cell without a hole transport layer (e.g., Figure 3 (As shown); the vacuum degree in step S7 is ≤1×10⁻⁶. −3 Pa; voltage 1.0-1.2V; current 150-160A; speed 1.0-1.5Å / s; the battery device structure is Glass / Cl-ITO / Cs x FA 1-x Pb y Sn 1-y I3 / C 60 / SnO2 / Ag; where 0.1≤ x ≤0.3, 0.4≤ y ≤0.6.

[0031] The performance of the obtained inverse lead-tin perovskite solar cell device without a hole transport layer was tested, and the results were as follows: Figure 4 The results shown; Figure 4 Key parameter data: Short-circuit current density This indicates that the lead-tin perovskite active layer of the battery has excellent absorption efficiency for sunlight, can effectively convert photons into photogenerated carriers, and has less loss of carriers during transmission. This is directly related to the synergistic effect of the optimized energy level matching of the halide ion modification layer and the efficient charge transfer of the electron transport layer in the device. Open circuit voltage This indicates that the battery has a strong ability to suppress nonradiative recombination of charge carriers. This is due to the dual passivation strategy of p-FPEACl and EDAI2. By effectively passivating the defects on the perovskite surface and suppressing the reverse diffusion of holes by the SnO2 hole blocking layer, the recombination loss between the interface and the bulk phase is reduced, thereby ensuring a high voltage output. Fill factor This indicates that the battery has excellent series and parallel resistance characteristics: the halide-ion modification layer reduces the contact resistance between ITO and the perovskite layer, the reasonable design of the electron transport layer and hole blocking layer reduces the carrier transport resistance, and the high conductivity of the metal electrode also reduces the external circuit loss, which together ensures the effective matching of current and voltage. Energy conversion efficiency This indicates that the hole transport layer-free inverted lead-tin perovskite solar cell performs excellently in the entire process of light absorption, carrier generation, separation, transport and collection, successfully breaking through the bottleneck of low efficiency of traditional hole transport layer-free cell structures, and verifying the effectiveness of the technical solutions of this invention (such as halide ion modification, double passivation, SnO2 hole blocking layer, etc.). In summary, this invention successfully fabricated a high-performance, high-stability hole-transport layer-free inverse lead-tin perovskite solar cell. The core of this achievement lies in the systematic combination of interface engineering and process innovation, overcoming the key bottlenecks of the HTL-free structure: First, UV-induced halogen modification technology was used to modulate the work function of the ITO electrode, alleviating the hole blockage problem caused by energy level mismatch; second, the perovskite crystallization kinetics were optimized through vacuum pumping, combined with a bimolecular synergistic passivation strategy, significantly improving film quality and suppressing interfacial nonradiative recombination; finally, SnO2 deposited by ALD was introduced as a hole-blocking layer, effectively suppressing hole back diffusion and device aging while efficiently transporting electrons. This invention not only overcomes the shortcomings of traditional HTL-structured cells, such as high cost and poor stability, but also solves the problems of low efficiency and large carrier loss in existing HTL-free cells. It provides a practical technical solution for simplifying device structure and reducing costs, and lays a solid theoretical and experimental foundation for promoting the industrialization of narrow-bandgap perovskite solar cells.

[0032] The present invention provides a method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer. First, the surface of a transparent ITO electrode is modified with halogenated hydrocarbon organic compounds under ultraviolet light, which improves the work function of the ITO electrode and enables energy level matching with the valence band top energy level of a narrow-bandgap lead-tin perovskite. This achieves efficient hole extraction and carrier separation without introducing a traditional hole transport layer. This method effectively solves the problems of acid corrosion, hygroscopic instability, and high cost associated with traditional HTL materials.

[0033] Secondly, a vacuum pumping method was chosen to replace the common antisolvent method for fabricating the active light-absorbing layer of the battery. Compared with the traditional antisolvent drop method, this method exhibits superior film quality and device performance in the fabrication of HTL-free narrow bandgap perovskite solar cells. This is because the film is deposited directly from the solution phase onto the ITO electrode, and the vacuum pumping method enables synchronous nucleation of the perovskite precursor solution throughout the crystallization kinetics, significantly improving the uniformity and density of the film's crystallization. Simultaneously, this method avoids introducing new solvents, simplifying the chemical environment at the interface and contributing to improved intrinsic device stability.

[0034] Then, since many defects exist on the upper surface of the perovskite film, affecting charge transport, in order to reduce the defect density on the upper surface of the perovskite film and reduce the obstacle to charge transport between it and fullerene, this invention uses a dual passivation strategy of p-fluorophenylethylamine hydrochloride (p-FPEACl) and ethylenediamine hydroiodide (EDAI2). p-FPEACl can effectively passivate defects on the perovskite surface through the strong electronegativity of fluorine atoms and the interaction between amino groups and the perovskite surface; while the double amino groups of EDAI2 can form stable coordination bonds with lead ions on the perovskite surface, and its iodide ions can compensate for iodine vacancies on the perovskite surface. The two passivating agents work synergistically to passivate more types of defects.

[0035] Since HTL-free devices lack a hole transport layer, holes may diffuse towards the metal electrode. This invention introduces a 10-30 nm thick tin oxide layer as a hole-blocking layer on top of the fullerene using atomic layer deposition (ALD). Because the conduction band bottom energy level of tin oxide is close to that of perovskite, electrons can be efficiently transferred from the perovskite layer to the tin oxide layer. Its valence band top energy level is much higher than that of perovskite, forming a significant energy barrier that prevents holes from diffusing into the electron transport layer, thereby greatly reducing nonradiative recombination of electrons and holes. More importantly, the tin oxide film prepared by ALD has excellent density, effectively isolating the underlying film from oxygen and water vapor in the air environment, greatly improving the stability of the perovskite solar cell device.

[0036] Therefore, the hole transport layer-free inverse lead-tin perovskite solar cell structure and its fabrication method provided by this invention have significant advantages in terms of energy level regulation, interface passivation, process simplification and stability improvement, providing a new idea and route for the large-scale fabrication of HTL-free perovskite solar cells.

[0037] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reverse lead-tin perovskite solar cell without a hole transport layer, characterized in that, The solar cell structure, from bottom to top, consists of: a halide-modified transparent ITO substrate, a lead-tin perovskite active layer, an electron transport layer, a hole blocking layer, and a metal electrode. The halide-modified layer is formed by modifying the surface of a transparent ITO substrate with halide organic compounds under ultraviolet light irradiation. It is used to regulate the work function of the ITO substrate so that the work function of ITO matches that of the lead-tin perovskite active layer. The chemical formula of the lead-tin perovskite active layer is Cs. x FA 1-x Pb y Sn 1-y I3, where FA is formamidinium ion. x The value range is 0.1≤ x ≤0.3, y The value range is 0.4≤ y ≤0.6; The electron transport layer material is fullerene C. 60 The thickness is 20-50nm; The hole blocking layer is made of tin oxide (SnO2) with a thickness of 10-30 nm; the metal electrode is made of silver (Ag) with a thickness of 100-150 nm.

2. The inverted lead-tin perovskite solar cell without a hole transport layer according to claim 1, characterized in that, The halogenated hydrocarbon organic compound is one of chlorobenzene CB, o-dichlorobenzene o-DCB, and bromobenzene BB, with a purity ≥99.8%.

3. The inverted lead-tin perovskite solar cell without a hole transport layer according to claim 2, characterized in that, The ultraviolet lamp has a wavelength of 300-400nm, a power of 5-15W, and an irradiation time of 30-90min.

4. A method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer, characterized in that, The method for fabricating an inverse lead-tin perovskite solar cell without a hole transport layer as described in any one of claims 1-3 comprises the following steps: S1. Cleaning and pretreatment of transparent ITO substrate: Cut the transparent glass substrate with ITO pattern retained after laser engraving, and clean it with detergent, deionized water, isopropanol and alcohol in sequence by ultrasonic cleaning. After drying with nitrogen, treat with ultraviolet ozone. S2. Preparation of ITO modified layer: In a nitrogen atmosphere glove box, the pretreated ITO substrate was placed under a UV irradiation device, o-dichlorobenzene was added dropwise to completely immerse the substrate, hydrogen peroxide solution was added dropwise, UV lamp was turned on for irradiation, and then residual o-DCB was removed by heating on a hot stage. S3, Preparation of lead-tin perovskite active layer: according to chemical formula Cs x FA 1-x Pb y Sn 1-y I3, 0.1≤ x ≤0.3, 0.4≤ y Weigh the raw materials at a stoichiometric ratio of ≤0.6, add DMF and DMSO solvents to prepare a perovskite precursor solution, shake and filter; Inside a nitrogen glove box, the precursor solution was dropped onto the modified ITO substrate. The precursor solution was then evenly spread onto the substrate surface in a vacuum spin coater. The substrate was then subjected to vacuuming and annealing to obtain a lead-tin perovskite active layer. S4. Surface defect passivation: Prepare p-FPEACl solution and EDAI2 solution respectively. Place the annealed device in a vacuum spin coater and drop p-FPEACl solution and EDAI2 solution onto the surface of the perovskite film in sequence to obtain the passivated lead-tin perovskite active layer. S5. Preparation of the electron transport layer: C is deposited on the surface of the passivated lead-tin perovskite active layer film using a vacuum evaporation device. 60 Obtain the electron transport layer; S6. Preparation of hole blocking layer: Using atomic layer deposition equipment, water and tetramethylaminotin (TDMSn) were used as raw materials to deposit 10-30 nm SnO2 on the surface of electron transport layer to obtain hole blocking layer; S7. Preparation of metal electrode: The battery device after step S6 is transferred to a vacuum coating machine, and a 100-150 nm thick metal Ag is deposited on the surface of the hole blocking layer to obtain an inverted lead-tin perovskite solar cell without a hole transport layer.

5. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The average water oxygen content in the nitrogen atmosphere during step S2 is ≤0.1ppm; In step S2, the wavelength of the ultraviolet lamp is 300-400nm, the power is 5-15W, and the irradiation time is 30-90min; the heating temperature of the hot table is 70-100℃, and the heating time is 5-15min.

6. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The raw materials in step S3 include CsI, FAI, SnI2, PbI2, Gly•HCl, SnF2, MASCN and tin granules.

7. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The preparation of EDAI2 solution in step S4 includes: weighing 0.5-1 mg of EDAI2, adding 500 μL each of isopropanol IPA and toluene, stirring at 70-80℃ for 6-12 h, and then filtering with a 0.22 μm polytetrafluoroethylene filter to obtain a colorless and transparent EDAI2 solution. The preparation of p-FPEACl solution involves weighing 1.5-2 mg of p-FPEACl, adding 500 μL each of IPA and toluene, shaking for 6-12 h, and then filtering with a 0.22 μm polytetrafluoroethylene filter to obtain a colorless and transparent p-FPEACl solution.

8. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The vapor deposition conditions in step S5 are: vacuum degree ≤1×10 −3 Pa; temperature 500-520℃; rate 0.1-0.2 Å / s; vapor deposition thickness 20-50 nm.

9. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The vacuum degree in step S7 is ≤1×10 −3 Pa; voltage 1.0-1.2V; current 150-160A; speed 1.0-1.5Å / s.

10. The method for fabricating an inverted lead-tin perovskite solar cell without a hole transport layer according to claim 4, characterized in that, The battery device has a Glass / Cl-ITO / Cs structure. x FA 1-x Pb y Sn 1-y I3 / C 60 / SnO2 / Ag; where 0.1≤ x ≤0.3, 0.4≤ y ≤0.6.

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