Perovskite solar cell based on double-molecular synergistic passivation and preparation method thereof

Abstract

The present application relates to the technical field of battery, especially to a perovskite solar cell based on double-molecule synergistic passivation and a preparation method thereof. The solar cell introduces an interface passivation layer between a perovskite thin film layer and an electron transport layer. The interface passivation layer adopts a double-molecule passivation strategy of competitive co-adsorption of PEAI and n-BABr. The two are used in a specific ratio. Through steric hindrance effect, the competitive passivation sites are formed on the surface, so as to inhibit the low-dimensional phase transition on the surface of the perovskite thin film. The experimental results show that the device efficiency is increased from 20.15% to 23.03%, and the initial efficiency of the unsealed device can still be maintained at 95.4% after 1000h storage under dark state inert condition, which is superior to the 91.4% of the single-component PEAI passivation device. The preparation method provided by the present application has mild conditions and is easy to operate, which is conducive to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to perovskite solar cells based on bimolecular synergistic passivation and their fabrication methods. Background Technology

[0002] Inverted (pin) perovskite solar cells (PSCs) represent a novel device structure with significant advantages. This type of cell is compatible with series cell structures and offers advantages such as low-temperature fabrication and good environmental stability. Despite its superior manufacturing and stability, its power conversion efficiency (PCE) is typically lower than that of traditional nip structures.

[0003] Currently, numerous defects at the perovskite / electron transport layer (ETL) interface are a key factor limiting device performance, severely impacting critical photovoltaic parameters such as open-circuit voltage (Voc), fill factor (FF), and short-circuit current density (Jsc). Therefore, the engineering of the perovskite / ETL interface is crucial for further improving the performance of inverted perovskite solar cells. Surface passivation is considered the preferred strategy for suppressing interface defects, optimizing energy level alignment, and mitigating halide migration.

[0004] Perovskite surface passivation typically involves selecting suitable materials as passivating agents and post-treating the perovskite thin film surface through physical adsorption or chemical bonding. Existing studies have systematically evaluated the passivation effects of ammonium salts, Lewis acids, bases and their complexes, as well as polymers, as interface modifiers. Among these, Lewis acid or base complexes (such as fullerene derivatives) can effectively passivate poorly coordinated Pb. 2+ / I - However, due to the weak covalent bonds, the passivation effect and stability are still somewhat limited; large-volume ammonium cations (Cs) are used. + or NH4 + Ammonium ions are a common strategy to suppress defect formation by filling missing A-site ions in perovskites. However, these ammonium ions can form two-dimensional / three-dimensional (2D / 3D) heterostructures in perovskites, thereby reconstructing the perovskite surface and having complex effects on device performance.

[0005] Therefore, how to further improve the performance of the perovskite / ETL interface through effective passivation strategies remains a technical problem that urgently needs to be solved in the field of perovskite solar cells. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the related art. Therefore, the first objective of the present invention is to provide a perovskite solar cell based on bimolecular synergistic passivation; the second objective of the present invention is to provide a method for fabricating a perovskite solar cell based on bimolecular synergistic passivation.

[0007] To achieve the first objective, the technical solution adopted by this invention is as follows:

[0008] A perovskite solar cell based on bimolecular synergistic passivation includes a conductive substrate, a hole transport layer, a perovskite thin film layer, an interface passivation layer, an electron transport layer, and an electrode layer arranged vertically in sequence.

[0009] The perovskite thin film layer is composed of FA. y Cs 1-y PbI3, y takes values ​​ranging from 0.8 to 0.9;

[0010] The interface passivation layer comprises PEAI and n-BABr, and the mass ratio of PEAI to n-BABr is 3:7 to 4:6.

[0011] PEAI is hydroxyphenylethylamine iodide, and n-BABr is n-butylamine bromide.

[0012] PEAI, as a typical bulky ammonium cationic passivating agent, contains iodide ions (I... - Phenylacetium cations can fill iodine vacancies and reduce hole traps, and their benzene ring structure provides good conductivity. However, phenylethylammonium cations (PEA) + PEA can form PEA2PbI4 with residual PbI2 on the surface of the perovskite thin film through hydrogen bonding, thereby forming a 2D / 3D heterostructure reconstruction interface. Furthermore, under high temperature or light exposure, PEA... + In FA-containing three-dimensional (3D) perovskite phases, amines readily deprotonate to form, and these amines can further react with FA. + The rapid reaction produces phenylethylaminomethylimide (PEAMA). + This accelerates phase separation, thereby affecting the high-temperature or light-induced stability of the device.

[0013] n-BABr, with its long alkyl chain structure, acts as a passivating agent, enhancing the hydrophobicity of perovskite surfaces to block environmental factors such as water and oxygen. Simultaneously, its highly electronegative bromide ions (Br₂) contribute to its effectiveness. -BA can alter the chemical environment and charge distribution on the perovskite surface, improving interfacial electrical properties. However, excessive BA... + An insulating 2D layer, BA2PbI4, will form on the film surface, hindering charge extraction and reducing flyback effect (FF). Furthermore, due to the significant steric hindrance effect of such macromolecular passivators, a single molecule often cannot simultaneously passivate adjacent defect sites to form a comprehensive and uniform passivation layer.

[0014] The perovskite solar cell based on bimolecular synergistic passivation provided by this invention comprises an interface passivation layer between the perovskite thin film layer and the electron transport layer (ETL). This interface passivation layer employs a bimolecular passivation strategy of competitive co-adsorption of PEAI and n-BABr. Used in a specific ratio, they compete for passivation sites on the surface through steric hindrance, thereby suppressing low-dimensional phase transitions on the perovskite thin film surface. Simultaneously, PEAI and n-BABr interact through complementary ion interactions (Ig). - / Br - By using hydrogen bonds, a more stable and dense passivated monolayer structure is constructed, further reducing the defect density. This bimolecular synergistic passivation strategy not only optimizes the energy level arrangement between perovskite and ETL, eliminating the electron transport barrier, but also improves the carrier extraction efficiency at the heterojunction.

[0015] Preferably, the electron transport layer consists of a PCBM layer and a BCP layer, with the BCP layer coated on top of the PCBM layer;

[0016] Among them, PCBM is methyl [6,6]-phenyl-C61-butyrate and BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.

[0017] Preferably, the components of the electrode layer are selected from Ag.

[0018] Preferably, the hole transport layer is made of nickel oxide.

[0019] Preferably, it further includes an interface modification layer disposed between the hole transport layer and the perovskite thin film layer.

[0020] Preferably, the component of the interface modification layer is selected from 2PACZ, where 2PACZ is 2-carbazole-9-ylethylphosphonic acid.

[0021] Preferably, the conductive substrate is selected from indium tin oxide (ITO) glass substrate.

[0022] To achieve the second objective, the technical solution adopted by this invention is as follows:

[0023] A method for fabricating perovskite solar cells based on bimolecular synergistic passivation, used to fabricate any of the above-mentioned perovskite solar cells based on bimolecular synergistic passivation, includes the following steps:

[0024] S100. Spin-coat the perovskite precursor solution onto the hole transport layer to obtain a perovskite thin film layer.

[0025] The perovskite precursor solution includes organic solvent I, lead iodide, formamidinium iodide, cesium iodide, and methylammonium chloride, with mass concentrations of lead iodide, formamidinium iodide, cesium iodide, and methylammonium chloride of 800 mg / ml to 810 mg / ml, 240 mg / ml to 245 mg / ml, 63 mg / ml to 68 mg / ml, and 15 mg / ml to 20 mg / ml, respectively.

[0026] S200: Dissolve n-BABr and PEAI in organic solvent II at a mass ratio of 3:7 to 4:6 to obtain a mixed solution of n-BABr and PEAI. Spin-coat the mixed solution onto the perovskite thin film to obtain an interface passivation layer.

[0027] S300: An electron transport layer is prepared on a perovskite thin film using spin coating technology.

[0028] S400. An electrode layer is prepared on the electron transport layer using a thermal evaporation method.

[0029] Preferably, the organic solvent I in step S100 is selected from dimethylformamide (DMF) and / or dimethyl sulfoxide (DMSO).

[0030] Preferably, the organic solvent II in step S200 is selected from isopropanol.

[0031] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0032] This invention provides a perovskite solar cell based on bimolecular synergistic passivation. The core of this invention lies in introducing an interfacial passivation layer between the perovskite thin film layer and the electron transport layer. This interfacial passivation layer employs a bimolecular passivation strategy of competitive co-adsorption of PEAI and n-BABr, used in combination at a specific ratio. Through steric hindrance, competition for passivation sites is formed on the surface, thereby suppressing low-dimensional phase transitions on the perovskite thin film surface. Simultaneously, PEAI and n-BABr interact through complementary ion interactions (I... - / Br -By combining hydrogen bonds, a more stable and dense passivated monolayer structure is constructed, further reducing defect density. This bimolecular synergistic passivation strategy not only optimizes the energy level arrangement between perovskite and ETL, eliminating the electron transport barrier, but also improves the carrier extraction efficiency at the heterojunction. Experimental results show that the device efficiency based on this strategy is significantly improved from 20.15% to 23.03%, and the unencapsulated device retains 95.4% of its initial efficiency after 1000 hours of storage under dark inert conditions. Compared with the 91.4% of commonly used single-component PEAI passivated devices, this demonstrates superior stability.

[0033] The preparation method provided by this invention is mild, easy to operate, and conducive to large-scale production.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell based on bimolecular synergistic passivation provided in an embodiment of the present invention.

[0036] Figure 2 These are surface electron microscope (SEM) images of different perovskite solar cell samples provided in Example 1 of this invention.

[0037] Figure 3 These are cross-sectional SEM images of different perovskite solar cell samples provided in Example 1 of this invention.

[0038] Figure 4 These are the X-ray diffraction (XRD) spectra of different perovskite solar cell samples provided in Example 1 of this invention.

[0039] Figure 5 This is a normalized XRD pattern of different perovskite solar cell samples provided in Example 1 of this invention, between 4 and 8 degrees.

[0040] Figure 6 This is a height map of the different perovskite solar cell samples provided in Example 2 of this invention, characterized by Kelvin probe force microscope (KPFM).

[0041] Figure 7 These are the potential diagrams of different perovskite solar cell samples provided in Example 2 of this invention, characterized by KPFM.

[0042] Figure 8This is the ultraviolet photoelectron spectroscopy (UPS) spectrum of different perovskite solar cell samples provided in Example 2 of this invention.

[0043] Figure 9 This is a partial enlarged view of the start and end regions of the UPS spectra of different perovskite solar cell samples provided in Example 2 of this invention.

[0044] Figure 10 This is a schematic diagram of the energy level arrangement of different perovskite solar cell samples provided in Example 2 of the present invention.

[0045] Figure 11 These are steady-state photoluminescence (PL) images and time-resolution photoluminescence (TRPL) spectra of different perovskite solar cell samples provided in Example 2 of this invention.

[0046] Figure 12 These are the ultraviolet-visible absorption spectra of different perovskite solar cell samples provided in Example 2 of this invention.

[0047] Figure 13 These are Tauc diagrams of different perovskite solar cell samples provided in Example 2 of this invention.

[0048] Figure 14 These are the femtosecond transient absorption (fs-TA) spectra of different perovskite solar cell samples provided in Example 2 of this invention.

[0049] Figure 15 This is a graph showing the wavelength-transient absorption (TA) relationship between different perovskite solar cell samples provided in Example 2 of this invention under different time delays.

[0050] Figure 16 This is a normalized curve of ground state bleaching (GSB) decay at a wavelength of 775 nm for different perovskite solar cell samples provided in Example 2 of this invention.

[0051] Figure 17 This is a space-charge-limited current (SCLC) curve of different perovskite solar cell samples provided in Test Example 3 of this invention.

[0052] Figure 18The above are electrochemical impedance spectroscopy (EIS) spectra of different perovskite solar cell samples provided in Example 3 of this invention.

[0053] Figure 19 This is a dark-state JV curve of different perovskite solar cell samples provided in Example 3 of this invention.

[0054] Figure 20 This is a graph showing the relationship between the open-circuit voltage and light intensity of different perovskite solar cell samples provided in Example 3 of this invention.

[0055] Figure 21 This is a capacitance-voltage curve of different perovskite solar cell samples provided in Example 3 of this invention.

[0056] Figure 22 This is a current density-voltage curve of different perovskite solar cell samples provided in Example 3 of the present invention.

[0057] Figure 23 This is a statistical graph showing the power conversion efficiency results of different perovskite solar cell samples provided in Example 3 of this invention.

[0058] Figure 24 The external quantum efficiency (EQE) spectra of different perovskite solar cell samples provided in Example 3 of this invention are shown.

[0059] Figure 25 This is a graph showing the steady-state power output (SPO) curves of different perovskite solar cell samples provided in Example 3 of this invention.

[0060] Figure 26 This is the result of the long-term stability test of different perovskite solar cell samples provided in Example 3 of this invention.

[0061] Figure Labels

[0062] 1. Conductive substrate; 2. Hole transport layer; 3. Perovskite thin film layer; 4. Interface passivation layer; 5. Electron transport layer; 6. Electrode layer. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0064] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0065] like Figure 1 As shown, a perovskite solar cell based on bimolecular synergistic passivation includes a conductive substrate 1, a hole transport layer 2, a perovskite thin film layer 3, an interface passivation layer 4, an electron transport layer 5, and an electrode layer 6 arranged longitudinally in sequence.

[0066] Example 1

[0067] The fabrication process of perovskite solar cells based on bimolecular synergistic passivation is as follows:

[0068] 1. The ITO / glass substrate with a sheet resistance of 10 Ohm / sq was ultrasonically cleaned sequentially using detergent, deionized water, and isopropanol. Before use, it was dried with dry nitrogen gas and treated with ultraviolet ozone for 20 minutes to obtain a clean ITO / glass substrate.

[0069] II. NiO with a concentration of 25 mg / ml x，x∈[1,2] An aqueous solution (70 μL) was spin-coated onto a clean ITO / glass substrate at 1700 rpm. After spin-coating for 30 s, the substrate was annealed on a heating plate at 150 °C for 20 min and then cooled to room temperature to obtain a conductive substrate coated with a nickel oxide hole transport layer.

[0070] 3. A 70 μL ethanol solution of (2-carbazole-9-ylethyl)phosphonic acid (2PACZ) with a concentration of 1 mg / ml was spin-coated onto the nickel oxide hole transport layer at a speed of 4000 rpm. After spin-coating for 30 s, the mixture was annealed at 100 ℃ for 10 min and cooled to room temperature to obtain the 2PACZ interface modification layer.

[0071] IV. FA at a concentration of 1.67 M 0.85 Cs 0.15PbI3 perovskite precursor solution (70 μL) was spin-coated onto the 2PACZ interface modification layer at a speed of 6000 rpm for 35 s. Methyl acetate (350 μL) was added dropwise at 15 s of spin-coating. The mixture was then immediately annealed on a 120 °C hot plate for 10 min and cooled to room temperature to obtain the perovskite coated thin film layer.

[0072] Among them, FA 0.85 Cs 0.15 The PbI3 perovskite precursor solution consists of 900 μL of a mixed solvent of DMF and DMSO (the volume ratio of DMF to DMSO is 4:1), which contains PbI2 (726.5 mg), formamidinium iodide (FAI) (219.3 mg), cesium iodide (CsI) (58.4 mg), and potassium ammonium chloride (MACl) (15 mg).

[0073] 5. Spin-coat a solution of different components (70 μL) onto the perovskite thin film at a speed of 6000 rpm for 30 s, anneal at 100 ℃ for 10 min, and cool to room temperature to obtain the interface passivation layer.

[0074] The single-component passivation process is as follows: PEAI (1 mg) and n-BABr (1 mg) are dissolved in isopropanol (1 mL) to obtain PEAI isopropanol solution and n-BABr isopropanol solution with concentrations of 1 mg / mL, respectively.

[0075] The synergistic passivation treatment of PEAI and n-BABr bimolecular components is as follows: Isopropanol solutions of n-BABr and PEAI (total amount of n-BABr and PEAI 1 mg) in different mass ratios are dissolved in isopropanol (1 ml) to obtain a PEAI / n-BABr isopropanol mixed solution. The mass ratios of PEAI and n-BAB are shown below:

[0076]

[0077] Control: No passivation treatment was performed on the perovskite thin film layer.

[0078] VI. A 20 mg / ml PCBM chlorobenzene solution (50 μL) was spin-coated onto the interface passivation layer (the blank control was spin-coated onto the perovskite thin film layer) at 2000 rpm for 30 s. Then, a 1 mg / ml BCP isopropanol solution (60 μL) was spin-coated onto the PCBM-coated interface passivation layer (the blank control was a PCBM-coated perovskite thin film layer) at 4000 rpm for another 30 s to obtain the electron transport layer. A 100 nm thick Ag electrode was then deposited on the electron transport layer using thermal evaporation to obtain perovskite solar cell samples with different passivation layers, as shown in the table below:

[0079]

[0080] The samples prepared in Example 1 were characterized, and the photovoltaic parameters J of different perovskite solar cell samples were analyzed. SC V OC The detection results for FF and PCE are shown in the table below:

[0081]

[0082] In the table above, J sc V is the short-circuit current density. oc is the open-circuit voltage, FF is the fill factor, and PCE is the power conversion efficiency.

[0083] Sample 7 (hereinafter referred to as Target), which has excellent photovoltaic parameters, sample 10 (hereinafter referred to as PEAI) and sample 11 (hereinafter referred to as n-BABr), which are passivated by a single molecule component, and sample 12 (hereinafter referred to as Control), which is not passivated, were selected for subsequent testing.

[0084] Example 1: An investigation into the optimization effect of PEAI and n-BABr bimolecular synergistic passivation on the surface morphology of perovskite thin films.

[0085] I. Scanning electron microscope (SEM) images were recorded using a field emission scanning electron microscope (Jeol JSM-6700F, Japan). The results are as follows: Figure 2 and Figure 3 As shown, from Figure 2As can be seen, the Control group perovskite films exhibit numerous small-sized dot-like particles on their surface, attributed to excessive residues from the film crystallization process. The PEAI and n-BABr monomolecular passivation group shows a significant reduction in dot-like particles, but new two-dimensional nanosheets appear. This is because PEAI and n-BABr react with residual PbI2 on the surface, ultimately forming a two-dimensional perovskite. While this low-dimensional phase transition on the surface may have some passivation effect, it negatively impacts carrier transport and collection. The Target group, characterized by bimolecular synergistic passivation of n-BABr and PEAI, shows almost complete disappearance of the two-dimensional nanosheets on the perovskite film surface, further increasing the perovskite grain size and significantly reducing the number of observed grain boundaries. The film surface is smoother, indicating the formation of a dense passivation layer rather than a two-dimensional perovskite. Figure 3 The SEM images of the sample cross-section shown further validate this conclusion. After synergistic passivation by n-BABr and PEAI bimolecules, the perovskite grains exhibit a more pronounced vertical alignment, increased grain size, and no obvious impurities were observed. This indicates that the synergistic effect of n-BABr and PEAI suppresses the formation of two-dimensional perovskite on the surface and achieves a more uniform and dense surface passivation.

[0086] II. XRD patterns of perovskite thin film layers of different types of perovskite solar cell samples were measured using a Rigaku ATX-XRD diffractometer at a 2θ range of 5° to 55° and a scan rate of 15° / min. The results are as follows: Figure 4 And as shown in the table below:

[0087] XRD diffraction parameters of perovskite thin films from different samples

[0088]

[0089] from Figure 4 The data provided in the table above shows that the perovskite (100) diffraction peak at 14 degrees did not exhibit a significant peak shift, indicating that the passivating agent only acts on the surface of the perovskite film layer and does not change the lattice parameters of the perovskite material, thus not causing significant changes in the internal structure of the material. Meanwhile, the perovskite (100) peak intensity is highest after n-BABr / PEAI treatment, indicating an increase in the crystallinity of the perovskite film layer. This can also be confirmed by semi-quantitative calculation of the perovskite grain size. The XRD test results were analyzed to determine the full width at half maximum (FWHM), in radians, using the Scherrer equation:

[0090] ;

[0091] The grain size can then be calculated, whereL For spherical crystallites, the constant K is typically taken as 0.94, and λ is the wavelength of the X-rays. The calculation results are shown in the table above. Compared to the Control perovskite film layer, the grain size increased by 2.19%, 1.86%, and 4.46% after PEAI, n-BABr, and n-BABr / PEAI treatments, respectively. Further data normalization was performed, as follows... Figure 5 As shown, passivation effectively reduced surface PbI2 residue, especially after n-BABr / PEAI bimolecular synergistic treatment, where the PbI2 peak intensity ratio at 12 degrees decreased from 7.58% in the perovskite film layer in Control to 4.24%. Furthermore, the perovskite film layer passivated by PEAI and n-BABr alone exhibited a weak diffraction peak near 4.9 degrees, indicating that residual PbI2 reacted with the passivation molecules to form a two-dimensional perovskite. However, no two-dimensional perovskite diffraction peaks were found in the n-BABr / PEAI synergistic passivation sample, suggesting that n-BABr and PEAI, as bulky ammonium cation passivators, easily compete for sites through steric hindrance, effectively inhibiting the formation of 2D perovskites. This also confirms the previous SEM test results. The results show that, compared with monomolecular passivation, bimolecular synergistic passivation can suppress PbI2 on the perovskite surface, and can achieve dense and uniform passivation of the perovskite surface by inhibiting the formation of 2D perovskite, thereby maximizing the quality of the perovskite film and its surface.

[0092] Test Example 2: The effect of bimolecular passivation strategy on the photoelectric properties of perovskite thin films.

[0093] KPFM was used to characterize the thin film surface morphology and potential distribution of different perovskite solar cell samples, such as... Figure 6 , Figure 7 And as shown in the table below:

[0094] KPFM roughness parameters of perovskite films of different samples

[0095]

[0096] In the above table, R q,Height This is the arithmetic average roughness in the height direction. Ra ,Height This refers to the root mean square roughness in the height direction. R q,Potential(mV) represents the arithmetic average roughness in potential. R a,Potential (mV): Root mean square roughness in potential.

[0097] The data provided in the table above and Figure 6 It is known that surface passivation can reduce the surface roughness of the film, especially after n-BABr / PEAI bimolecular synergistic passivation treatment, the roughness of the perovskite film layer can be reduced from 15.9 nm to 13.1 nm. A smooth perovskite surface facilitates the formation of a more uniform and continuous electron transport layer on top, thus forming a high-quality interface. The surface potential of the perovskite film layer is as follows... Figure 7 As shown, surface passivation, especially n-BABr / PEAI bimolecular passivation, can reduce the surface potential, which is attributed to the upward shift of the Fermi level in the perovskite film after passivation. Furthermore, bimolecular passivation can create a more uniform potential distribution. When PEAI or n-BABr is used alone for passivation, irregularly arranged bright spots appear on the surface potential distribution map, which is unrelated to film roughness, as the surface roughness is reduced after passivation. Therefore, it is considered that the 2D perovskite formed on the surface after monomolecular passivation causes the surface potential fluctuations. The more uniform surface potential distribution after n-BABr / PEAI bimolecular passivation can be attributed to changes in the contact potential difference. This was further confirmed. After n-BABr passivation... The voltage can be reduced from 19 mV to 15 mV in the control sample, and further reduced to 10 mV after PEAI passivation, while it can be reduced to 7 mV after n-BABr / PEAI bimolecular passivation. The reduction further illustrates that this strategy can achieve dense and uniform passivation of the perovskite surface by suppressing the formation of 2D perovskites.

[0098] The changes in surface energy levels of perovskite thin film layers from different samples were characterized using UPS, such as Figure 8 , Figure 9 (Where A is a magnified view of the starting region, and B is a magnified view of the ending region) and the table below:

[0099] UPS test results of perovskite thin films with different treatments

[0100]

[0101] In the above table, E cutoffThe cutoff energy; the work function is the minimum energy required to remove an electron from the surface of a material; E F -E V | represents the absolute value between the Fermi level and the top of the valence band. E F Represents the Fermi level. E V This indicates the top of the price band.

[0102] Figure 10 This diagram illustrates the energy level arrangement of different solar cell samples. The Fermi level on the perovskite film surface shifts upwards after surface treatment, consistent with the results obtained from KPFM, indicating that the passivated film surface tends towards n-type conductivity. This is attributed to the surface passivation strategy effectively suppressing defects and increasing the surface carrier concentration. Simultaneously, n-BABr / PEAI bimolecular synergistic passivation eliminates the potential barrier between the highest occupied molecular orbital energy levels of the perovskite and electron transport layers, achieving better energy level arrangement and promoting rapid pumping and collection of photogenerated carriers at the interface, thus improving the device's photoelectric conversion efficiency.

[0103] To investigate the effect of the n-BABr / PEAI bimolecular passivation strategy on the carrier dynamics of perovskite thin films, this invention characterized the PL and TRPL spectra of the corresponding perovskite thin films, as follows: Figure 11 Figures A and B are shown in the figure. PL and TRPL were measured using a Fluorolog-Horiba fluorescence spectrometer (FLS980, Edinburgh Instruments, UK) at room temperature with 470 nm laser excitation.

[0104] Figure 11 Figure A shows that surface passivation improves the luminescence properties of the perovskite film. Compared with the Conrtol group, the photoluminescence intensity of the film after n-BABr / PEAI bimolecular passivation is increased by more than 3 times, which confirms its excellent defect passivation properties. Figure 11 The results in Figure B show that there are significant differences in carrier lifetimes of perovskite films among different samples. The parameter results of the double exponential fitting of the TRPL spectrum are shown in the table below:

[0105]

[0106] In the table above, A1 corresponds to the initial luminescence intensity percentage of the short-lived component, and A2 corresponds to the initial luminescence intensity percentage of the long-lived component. τ 1. Short-lived component τ 2 is a long-life component. τ ave ns represents the average fluorescence lifetime, and ns represents nanoseconds.

[0107] The data provided in the table above shows that the average carrier lifetime of the film after bimolecular passivation is... τ ave The increase from 739.97 ns in the Control sample to 1132.68 ns represents an order of magnitude improvement, indicating that the strategy effectively suppresses recombination of photogenerated carriers on the surface. This helps to improve the photoelectric conversion efficiency of the device by significantly enhancing the carrier collection efficiency.

[0108] like Figure 12 As shown, the perovskite film exhibits a nearly consistent light absorption edge under different samples, and the optical band gap of the perovskite film is about 1.57 eV, indicating that the surface passivation strategy does not affect the light absorption characteristics of the film.

[0109] Taking the logarithm of the absorption coefficient yields the Urbach energy, such as... Figure 13 As shown, the Urbach energy decreases after surface passivation, and reaches its lowest point after n-BABr / PEAI bimolecular passivation, indicating that this strategy effectively suppresses the defect state density with tails and improves the quality of the perovskite film.

[0110] like Figure 14 As shown, the fs-TA spectra of the perovskite thin films reveal the internal microscopic processes and dynamic characteristics of light absorption in perovskite thin films under different passivation conditions over extremely short time periods. All samples exhibit a GSB signal originating from bandgap state filling at approximately 775 nm; Figure 15 As shown, the relationship between TA absorption and wavelength is illustrated under different time delays. The change in GSB photoinduced absorption (ΔT / T) gradually decreases with increasing delay time, indicating enhanced photoinduced recombination between electrons and holes. However, at the same delay time, the GSB peak intensity of the n-BABr / PEAI passivated film is significantly weakened, which is attributed to enhanced carrier extraction.

[0111] like Figure 16 As shown, the GSB signal attenuation observed at a wavelength of 775 nm showed that the n-BABr / PEAI passivated film had the longest attenuation time, which further confirms the reduction of trap-assisted recombination.

[0112] Example 3: Verification of the performance improvement effect of the bimolecular passivation strategy on battery performance.

[0113] like Figure 17 As shown, this figure is the SCLC curve of a perovskite solar cell device based on bimolecular synergistic passivation under dark conditions. The SCLC measurement conditions are: in the dark, with a voltage range of 0–5.0 V and a step size of 20 mV.

[0114] Based on local characteristics, the curve can be divided into the Ohmic region (low voltage), the TFL region (medium voltage), and the Child region (high voltage). The Ohmic region represents the current condition at low voltages, where the device contains native free carriers. The TFL region is where new carriers are generated after reaching a certain voltage, resulting in a steeper curve that eventually flows into the Child region, which is used to study carrier mobility. Surface passivation can reduce the defect state density of perovskite films, especially using the n-BABr / PEAI bimolecular passivation strategy, which can reduce the defect state density from 2.843 × 10⁻⁶. 15 cm -3 Significantly reduced to 1.209×10 15 cm -3 .

[0115] EIS can be used to further characterize the charge transport performance in perovskite solar cells, and the results are as follows: Figure 18 As shown, the composite resistance R extracted from the Nyquist semicircle after n-BABr / PEAI bimolecular passivation... rec The Ω could be increased from 963.9 Ω in the Control sample to 2198 Ω, which indicates that the bimolecular co-passivation strategy can effectively suppress nonradiative recombination of photogenerated carriers.

[0116] like Figure 19 The figure shows the dark-state JV curves of different perovskite solar cell samples. The dark-state saturation current ranges from 8 × 10⁻⁶ in the control group. -6 mA / cm 2 Reduced to 1×10 -6 mA / cm 2 This also indicates that bimolecular passivation effectively suppresses nonradiative recombination losses in the device.

[0117] like Figure 20 As shown, the open-circuit voltage (V) of different perovskite solar cell samples is... OC A graph showing the relationship between light intensity (P) and illuminance (V). OC The value decreased from 1.95 in the control group device to 1.67 in the n-BABr passivated device, 1.58 in the PEAI passivated device, and reached 1.36, which is relatively close to 1, in the n-BABr / PEAI bimolecular passivated device. This result indicates that on the surface, bimolecular passivation effectively suppresses trap-assisted nonradiative recombination.

[0118] like Figure 21 As shown, the capacitance-voltage (CV) curves of different perovskite solar cell samples are presented. The built-in potential V of the solar cell sample based on the n-BABr / PEAI bimolecular passivation strategy is also shown. biThe voltage can be increased significantly from 0.859V to 1.010V, which shows that the strategy significantly improves the separation and extraction efficiency of photogenerated carriers in the device.

[0119] like Figure 22 The figure shows typical current density-voltage (JV) curves for different perovskite solar cell samples. From this figure, we can see that the JV of the Control sample... SC 24.10 mA / cm 2 J of n-BABr samples SC 24.78 mA / cm 2 J of PEAI sample SC 24.88 mA / cm 2 Sample J, passedivated by n-BABr / PEAI bimolecular method SC Increased to 25.28 mA / cm 2 .

[0120] like Figure 23 As shown in the figure, the PCE results of different perovskite solar cell samples are statistically analyzed. The results indicate that n-BABr / PEAI synergistic passivation has a more significant effect on improving the PCE of perovskite solar cells than single-molecule passivation.

[0121] like Figure 24 The figure shows the EQE spectra of different perovskite solar cell samples in the range of 300 nm to 800 nm. Surface passivation treatment can improve the photoresponse of the device at both short and long wavelengths, indicating that passivation effectively improves the collection of photogenerated carriers at the interface. The integral J of the EQE curves after n-BABr passivation, PEAI passivation, and n-BABr / PEAI bimolecular passivation are also shown. SC From 22.91 mA / cm 2 The current level was increased to 23.73 mA / cm. 2 23.80 mA / cm 2 and 24.05 mA / cm 2 This is similar to the result in the JV curve.

[0122] like Figure 25 As shown, the SPO curves of different perovskite solar cell samples are displayed. After 800s, the bimolecular passivated sample device exhibits a steady-state output efficiency of 22.26%, which is significantly higher than that of other sample devices.

[0123] Unencapsulated sample devices were aged under a nitrogen atmosphere for 1000 hours to evaluate the environmental stability of different sample devices. The results are as follows: Figure 26As shown, the results indicate that the device passivated with n-BABr / PEAI still retains 95.4% of its initial efficiency, while under the same conditions, the efficiency loss of the control group exceeds 15%, and the efficiency loss of the single-molecule passivated device is also close to 10%, indicating that bimolecular passivation can provide better stability for the device.

[0124] In summary, the perovskite solar cell based on bimolecular synergistic passivation provided by this invention employs a bimolecular passivation strategy of competitive co-adsorption of PEAI and n-BABr at the interface between the perovskite thin film and the electron transport layer. Although both PEAI and n-BABr have good passivation effects, they tend to form 2D perovskites on the surface, thus affecting the efficient transport and collection of photogenerated carriers. At a specific ratio, the combined use of n-BABr and PEAI creates competition for passivation sites on the surface, suppressing low-dimensional phase transitions on the perovskite thin film surface. This allows for the formation of a stable and dense passivation monolayer on the perovskite surface, reducing defect density. Furthermore, this strategy optimizes the energy level arrangement between the perovskite and the ETL, eliminating the electron transport barrier and improving carrier extraction efficiency at the heterojunction. Ultimately, using the n-BABr / PEAI bimolecular passivation strategy, the device efficiency is significantly improved from 20.15% to 23.03%. Furthermore, the unpackaged device retains 95.4% of its initial efficiency after being stored in the dark and inert environment for 1000 hours, which is significantly better than the 91.4% of the commonly used single PEAI passivated device.

[0125] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A perovskite solar cell based on bimolecular synergistic passivation, characterized in that, It includes a conductive substrate, a hole transport layer, a perovskite thin film layer, an interface passivation layer, an electron transport layer, and an electrode layer arranged vertically in sequence; The perovskite thin film layer is composed of FA. y Cs 1-y PbI3, y takes values ​​ranging from 0.8 to 0.9; The interface passivation layer comprises PEAI and n-BABr, and the mass ratio of PEAI to n-BABr is 3:7 to 4:

6. PEAI is hydroxyphenylethylamine iodide, and n-BABr is n-butylamine bromide.

2. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 1, characterized in that, The electron transport layer is composed of a PCBM layer and a BCP layer, with the BCP layer coated on top of the PCBM layer. Among them, PCBM is methyl [6,6]-phenyl-C61-butyrate and BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.

3. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 1, characterized in that, The electrode layer is composed of Ag.

4. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 1, characterized in that, The hole transport layer is made of nickel oxide.

5. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 1, characterized in that, It also includes an interface modification layer disposed between the hole transport layer and the perovskite thin film layer.

6. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 5, characterized in that, The component of the interface modification layer is selected from 2PACZ, which is [2-(9H-carbazole-9-yl)ethyl]phosphonic acid.

7. The perovskite solar cell based on bimolecular synergistic passivation as described in claim 1, characterized in that, The conductive substrate is selected from indium tin oxide glass substrate.

8. A method for fabricating perovskite solar cells based on bimolecular synergistic passivation, characterized in that, The method for preparing a perovskite solar cell based on bimolecular synergistic passivation as described in any one of claims 1 to 7 comprises the following steps: S100. Spin-coat the perovskite precursor solution onto the hole transport layer to obtain a perovskite thin film layer. The perovskite precursor solution includes organic solvent I, lead iodide, formamidinium iodide, cesium iodide, and methylammonium chloride, with mass concentrations of 800–810 mg / ml, 240–245 mg / ml, 63–68 mg / ml, and 15–20 mg / ml, respectively. S200. Dissolve PEAI and n-BABr in organic solvent II at a mass ratio of 3:7 to 4:6 to obtain a mixed solution of n-BABr and PEAI. Spin-coat the mixed solution onto the perovskite thin film to obtain an interface passivation layer. S300: An electron transport layer is prepared on the interface passivation layer using spin coating technology; S400. An electrode layer is prepared on the electron transport layer using a thermal evaporation method.

9. The method for fabricating a perovskite solar cell based on bimolecular synergistic passivation as described in claim 8, characterized in that, The organic solvent I in step S100 is selected from dimethylformamide and / or dimethyl sulfoxide.

10. The method for fabricating a perovskite solar cell based on bimolecular synergistic passivation as described in claim 8, characterized in that, The organic solvent II in step S200 is selected from isopropanol.

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