Perovskite heterojunction and preparation method and application thereof

Abstract

The application provides a perovskite heterojunction and a preparation method and application thereof. The perovskite heterojunction comprises a three-dimensional perovskite layer, a two-dimensional perovskite layer covering at least a part of the three-dimensional perovskite layer, a reaction-inert spacer layer and a two-dimensional molecular passivation layer interposed between the three-dimensional perovskite layer and the two-dimensional perovskite layer. In the perovskite heterojunction of the application, the reaction-inert spacer layer alleviates the problem of grain boundary etching in a traditional structure, and realizes molecular passivation directly on the surface of the perovskite.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a perovskite heterostructure, its preparation method, and its application. Background Technology

[0002] Perovskite solar cells (PSCs) have become a promising photovoltaic technology due to their potential for low cost and low carbon footprint in industrial manufacturing. Based on the deposition order of the device layers, perovskite solar cells can be divided into two categories: upright (nip structure) and inverted (pin structure). Although both types of devices have made some progress, upright perovskite solar cells face more severe stability challenges in practical applications, mainly due to their use of lithium-doped Spiro-OMeTAD as the hole transport layer. Therefore, inverted perovskite solar cells have received widespread attention in recent years and have achieved the highest photoelectric conversion efficiency. In state-of-the-art inverted perovskite solar cells, a self-assembled monolayer is used as the hole transport layer on the p-side, forming a tight interfacial contact and achieving passivation, thus achieving photoelectric conversion efficiency and stability superior to upright devices. However, in inverted devices, the perovskite heterointerface on the n-side remains less than ideal due to the limited molecular interaction between the fullerene-based electron transport layer (ETL) and the perovskite surface.

[0003] Two-dimensional (2D) perovskites or related organic molecules have been used as effective top-surface passivators, not only reducing non-radiative recombination centers but also acting as a structural capping layer to protect the film from environmental factors such as moisture intrusion. Researchers have made significant efforts to customize the molecular structure of 2D perovskite passivators using various organic cations, and these attempts have been shown to improve the photoelectric conversion efficiency and stability of perovskite solar cells. However, detailed studies of the heterostructure microstructure of 2D perovskite passivators remain scarce to date; such research may offer new opportunities for improving device performance and elucidating the passivation mechanism. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a perovskite heterojunction, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a perovskite heterostructure comprising a three-dimensional perovskite layer, a two-dimensional perovskite layer covering at least a portion of the three-dimensional perovskite layer, a reactive inert spacer layer and a two-dimensional molecular passivation layer interposed between the three-dimensional perovskite layer and the two-dimensional perovskite layer.

[0006] In this invention, the reactive inert spacer layer acts as an inert "molecular sieve," allowing controlled ion permeation and exchange between the three-dimensional perovskite surface and the molecular salt of the two-dimensional molecular passivation layer. The interfacial reaction rate of the reactive inert spacer layer is significantly reduced, enabling the formation of a uniform layered surface microstructure.

[0007] In some embodiments, the perovskite heterostructure comprises a three-dimensional perovskite layer, a two-dimensional molecular passivation layer, a reactive inert spacer layer, and a two-dimensional perovskite layer stacked sequentially.

[0008] In some implementations, the terms "covering at least a portion" and "overlapping" refer to an area of ​​at least 50% overlap between two layers, such as 50%-100%, 60%, 70%, 80%, 90%, 95%, or 99%.

[0009] In some embodiments, the reactive inert spacer layer has nanochannels with an average size of 0.5-1.5 nm.

[0010] In some embodiments, the two-dimensional perovskite layer comprises one or more perovskite layers, each perovskite layer having a width n of 1 and / or 2.

[0011] In some embodiments, the orientation of the two-dimensional perovskite layer is substantially parallel to the surface of the three-dimensional perovskite layer.

[0012] In some embodiments, the average thickness of the three-dimensional perovskite layer is 5-1000 nm; such as 20-800 nm, 50-700 nm, 100-500 nm, etc.

[0013] In some embodiments, the average thickness of the two-dimensional perovskite layer is 1-30 nm; such as 3-25 nm, 4 nm-23 nm, 5-20 nm, 5-15 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, etc.

[0014] In some embodiments, the average thickness of the reactive inert spacer layer is 1-150 nm; such as 1-80 nm, 2-70 nm, 3-60 nm, 3-50 nm, 3-40 nm, 4-30 nm, 5-20 nm, 5-15 nm, etc.

[0015] In some embodiments, the average thickness of the two-dimensional molecular passivation layer is 0.5-2.0 nm, such as 0.7-1.8 nm, 0.8-1.8 nm, 1.0-1.5 nm, etc. In this invention, the two-dimensional molecular passivation layer is formed by the direct adsorption of two-dimensional molecules onto the surface of a three-dimensional perovskite layer. Theoretically and experimentally, it tends to form a monolayer with an extremely thin thickness. This thickness is determined by the following factors: 1) The size of the molecules themselves: Two-dimensional molecular ions have a certain length. When these molecules "stand" on the surface of the three-dimensional perovskite at a near-vertical or tilted angle, the thickness of the layer formed is limited by the size of a single molecule; 2) The formation mechanism of self-assembly: The formation of this passivation layer is a typical self-assembly process. Two-dimensional molecular ions are positively charged and generate strong electrostatic interactions or ionic bonds with the negatively charged octahedral framework exposed on the surface of the three-dimensional perovskite. This strong adsorption drives the molecules to form a dense, ordered thin layer on the surface. Once the surface of a three-dimensional perovskite is completely covered by this monolayer, it becomes very difficult for subsequent two-dimensional molecular ions to find active sites for adsorption, thus naturally terminating the growth process.

[0016] In some embodiments, the three-dimensional or two-dimensional perovskite layer comprises ABX3 type perovskite, wherein the A-site is a cesium ion (Cs). + ), Methylamine cation (MA) + ), formamidinium cation (FA) + One or more of the following; the B site is a lead ion (Pb). 2 + ), tin ions (Sn) 2+ ), copper ions (Cu) 2+ The X-position is a fluoride ion (F). - ), chloride ions (Cl) - ), bromide ions (Br) - ), iodide ions (I) - One or more of the following.

[0017] Perovskite compounds with the following formulas: CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbF3, CH3NH3PbBr x I 3-x CH3NH3PbBr x Cl 3-x CH3NH3PbI x Cl 3-x CH3NH3PbI 3-x Cl x , CH3NH3SnI3, CH3NH3SnBr3, CH3NH3SnCl3, CH3NH3SnF3, CH3NH3SnBrI2, CH3NH3SnBrx I 3-x CH3NH3SnBr x Cl 3-x CH3NH3SnF 3-x Br x CH3NH3SnI x Br 3-x CH3NH3SnI x Cl 3-x CH3NH3SnF 3-x I x CH3NH3SnCl x Br 3-x CH3NH3SnI 3-x Cl x and CH3NH3SnF 3-x Cl x , CH3NH3CuI3, CH3NH3CuBr3, CH3NH3CuCl3, CH3NH3CuF3, CH3NH3CuBrI2, CH3NH3CuBr x I 3-x CH3NH3CuBr x Cl 3-x CH3NH3CuF 3-x Br x CH3NH3CuI x Br 3-x CH3NH3CuI x Cl 3-x CH3NH3CuF 3-x I x CH3NH3CuCl x Br 3-x CH3NH3CuI 3-x Cl x or CH3NH3CuF 3-x Cl x Where x is between 0 and 3; The following perovskite compounds are listed: (H2N–C(H)=NH2)PbI3, (H2N–C(H)=NH2)PbBr3, (H2N–C(H)=NH2)(H2N–C(H)=NH2)PbCl3, (H2N–C(H)=NH2)PbF3, (H2N–C(H)=NH2)PbBr x I 3-x (H2N–C(H)=NH2)PbBr x Cl 3-x (H2N–C(H)=NH2)PbI x Br 3-x(H2N–C(H)=NH2)PbI x Cl 3-x (H2N–C(H)=NH2)PbCl x Br 3-x (H2N–C(H)=NH2)PbI 3-x Cl x 、(H2N–C(H)=NH2)SnI3、(H2N–C(H)=NH2)SnBr3、(H2N–C(H)=NH2)SnCl3 、(H2N–C(H)=NH2)SnF3、(H2N–C(H)=NH2)SnBrI2、(H2N–C(H)=NH2)SnBr x I 3-x (H2N–C(H)=NH2)SnBr x Cl 3-x (H2N–C(H)=NH2)SnF 3-x Br x (H2N–C(H)=NH2)SnI x Br 3-x (H2N–C(H)=NH2)SnI x Cl 3-x (H2N–C(H)=NH2)SnF 3-x I x (H2N–C(H)=NH2)SnCl x Br 3-x (H2N–C(H)=NH2)SnI 3-x Cl x (H2N–C(H)=NH2)SnF 3-x Cl x 、(H2N–C(H)=NH2)CuI3、(H2N–C(H)=NH2)CuBr3、(H2N–C(H)=NH2)CuCl3 、(H2N–C(H)=NH2)CuF3、(H2N–C(H)=NH2)CuBrI2、(H2N–C(H)=NH2)CuBr x I 3-x (H2N–C(H)=NH2)CuBr x Cl 3-x (H2N–C(H)=NH2)CuF 3-x Br x (H2N–C(H)=NH2)CuI x Br 3-x (H2N–C(H)=NH2)CuI x Cl 3-x (H2N–C(H)=NH2)CuF3-x I x (H2N–C(H)=NH2)CuCl x Br 3-x (H2N–C(H)=NH2)CuI 3-x Cl x Or (H2N–C(H)=NH2)CuF 3-x Cl x Where x is between 0 and 3; or Perovskite compounds with the following formula: (H2N–C(H)=NH2) y Cs 1-y PbI3, (H2N–C(H)=NH2) y Cs 1-y PbBr3, (H2N–C(H)=NH2) y Cs 1-y PbCl3, (H2N–C(H)=NH2) y Cs 1-y PbF3, (H2N–C(H)=NH2) y Cs 1-y PbBr x I 3-x (H2N–C(H)=NH2) y Cs 1-y PbBr x Cl 3-x (H2N–C(H)=NH2) y Cs 1-y PbI x Br 3-x (H2N–C(H)=NH2) y Cs 1- y PbI x Cl 3-x (H2N–C(H)=NH2) y Cs 1-y PbCl x Br 3-x (H2N–C(H)=NH2) y Cs 1-y PbI 3-x Cl x (H2N–C(H)=NH2) y Cs 1-y SnI3、(H2N–C(H)=NH2) y Cs 1-y SnBr3, (H2N–C(H)=NH2) y Cs 1-ySnCl3、(H2N–C(H)=NH2) y Cs 1-y SnF3、(H2N–C(H)=NH2) y Cs 1-y SnBrI2、(H2N–C(H)=NH2) y Cs 1-y SnBr x I 3-x 、(H2N–C(H)=NH2) y Cs 1-y SnBr x Cl 3-x 、(H2N–C(H)=NH2) y Cs 1-y SnF 3-x Br x 、(H2N–C(H)=NH2) y Cs 1-y SnI x Br 3-x 、(H2N–C(H)=NH2) y Cs 1-y SnI x Cl 3-x 、(H2N–C(H)=NH2) y Cs 1-y SnF 3-x I x 、(H2N–C(H)=NH2) y Cs 1- y SnCl x Br 3-x 、(H2N–C(H)=NH2) y Cs 1-y SnI 3-x Cl x 、(H2N–C(H)=NH2) y Cs 1-y SnF 3-x Cl x 、(H2N–C(H)=NH2) y Cs 1-y CuI3、(H2N–C(H)=NH2) y Cs 1-y CuBr3、(H2N–C(H)=NH2) y Cs 1-y CuCl3、(H2N–C(H)=NH2) y Cs 1-y CuF3、(H2N–C(H)=NH2) y Cs1-y CuBrI2, (H2N–C(H)=NH2) y Cs 1-y CuBr x I 3-x (H2N–C(H)=NH2) y Cs 1-y CuBr x Cl 3-x (H2N–C(H)=NH2) y Cs 1-y CuF 3-x Br x (H2N–C(H)=NH2) y Cs 1-y CuI x Br 3-x (H2N–C(H)=NH2) y Cs 1-y CuI x Cl 3-x (H2N–C(H)=NH2) y Cs 1-y CuF 3-x I x (H2N–C(H)=NH2) y Cs 1- y CuCl x Br 3-x (H2N–C(H)=NH2) y Cs 1-y CuI 3-x Cl x Or (H2N–C(H)=NH2) y Cs 1-y CuF 3-x Cl x , where x is from 0 to 3 and y is from 0.1 to 0.9.

[0018] In some embodiments, the reactive inert spacer layer comprises at least one of a fullerene or a derivative thereof, a non-fullerene acceptor material, or a non-conjugated polymer, such as C60, methyl phenyl-C61-butyrate (PCBM), methyl [6,6]-phenyl-C71-butyrate (PC70BM), indene-C60 diadduct (ICBA), ITIC ([2,2'-((1,3-benzo[e]indoline-2,5-dionitrile)[2,2'-((1,3-benzo[e]dithiophene-2,6-diyl)bis(methylene))bis(3-fluoro-6-oxo-6H-benzo[e]indoline-2,5-dionitrile)), Y6 (IT-4F) and its derivatives, polymethyl methacrylate, or polystyrene.

[0019] In some embodiments, the two-dimensional molecular passivation layer comprises at least one organic ammonium salt, such as phenethylammonium, 4-fluorophenethylammonium, 3-fluorophenethylammonium, 2-fluorophenethylammonium, butylammonium, hexylammonium, octylammonium, or 1-naphthylmethylammonium organic ligand; the two-dimensional molecular passivation material comprises at least one of phenylethylammonium iodide (PEAI), butylammonium iodide (BAI), hexylammonium iodide (HAI), octylammonium iodide (OAI), benzoylammonium iodide (PMAI), naphthylethylammonium iodide (NEAI), thiophene methylammonium iodide, adamantane ammonium iodide (ADAI), aminovaloric acid iodide (AVAI), sulfonylammonium salt, 1,4-butanediammonium iodide (BDAI2), 1,6-hexammonium diammonium iodide (HDAI2), terephthalic diethylammonium iodide (PDEAI2), biphenyl diammonium salt, phenylethylammonium bromide (PEABr), and phenylethylammonium chloride (PEACI).

[0020] A second aspect of the present invention provides a method for preparing the perovskite heterojunction described above, comprising the following steps: A reactive inert spacer material solution is coated onto the surface of a three-dimensional perovskite layer, followed by a two-dimensional molecular passivation material solution, and then annealed to obtain the perovskite heterojunction.

[0021] In this invention, during the annealing process, the reactive inert spacer material acts as a "molecular sieve," enabling interlayer transport between the three-dimensional perovskite surface and the two-dimensional molecular passivation material, and regulating the reaction between the two, thereby forming a uniform two-dimensional perovskite layer.

[0022] In some embodiments, the concentration of the reactive inert spacer material solution is 0.5-20 mg / mL, such as 0.5-15 mg / mL, 1-10 mg / mL, etc.

[0023] In some embodiments, the concentration of the two-dimensional molecular passivation material solution is 0.5-30 mg / mL, such as 0.5-20 mg / mL, 0.5-15 mg / mL, etc.

[0024] In some embodiments, the solvent used in the reactive inert spacer material solution includes at least one of chlorobenzene, dichlorobenzene (DCB), particularly o-dichlorobenzene (o-DCB), toluene, and xylene.

[0025] In some embodiments, the solvent used in the two-dimensional molecular passivation material solution includes at least one of isopropanol, ethanol, and n-butanol.

[0026] In some embodiments, the annealing temperature is 50-200℃, such as 70-160℃, 80-150℃, etc.; the annealing time is 1-60min, such as 5-30min, 5-20min, etc.

[0027] A third aspect of the present invention provides a perovskite solar cell, comprising the aforementioned perovskite heterojunction.

[0028] In some embodiments, the perovskite solar cell includes a conductive substrate, a first transport layer, a perovskite heterojunction, a second transport layer, and a metal electrode stacked sequentially; one of the first transport layer and the other of the second transport layer is a hole transport layer and the other is an electron transport layer.

[0029] In some embodiments, the conductive substrate comprises ITO conductive glass, FTO conductive glass, or aluminum-doped zinc oxide (AZO) conductive glass. The conductive glass needs to be cleaned before use, for example, by ultrasonic cleaning with a cleaning agent (including but not limited to surfactants), ethanol, acetone, isopropanol, and deionized water.

[0030] In some implementations, when the first transport layer is an electron transport layer (ETL) and the second transport layer is a hole transport layer (HTL), the perovskite solar cell containing these layers is a positive device.

[0031] In some implementations, when the first transport layer is a hole transport layer (HTL) and the second transport layer is an electron transport layer (ETL), the perovskite solar cell containing both is an inversion device.

[0032] In some embodiments, the thickness of the hole transport layer can be in the range of 5-300 nm, or optionally 100-200 nm.

[0033] In some embodiments, the hole transport layer (HTL) includes at least one of CuSCN, NiOx, CuI, MoOx, WO3, ZnO, TiO2, SnO2, poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, polyethoxyethyleneimine, polyethyleneimine, and isomethyl [6,6]-phenyl-C61-butyrate.

[0034] In some embodiments, the thickness of the electron transport layer may be in the range of 5-200 nm, or optionally 20-100 nm.

[0035] In some embodiments, the electron transport layer (ETL) includes CuSCN, NiOx, CuI, MoOx, WO3, ZnO, TiO2, SnO2, poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, polytriarylamine, 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, polyethoxyethyleneimine, polyethyleneimine, and [6,6]-phenyl-C 61 - Isomethyl butyrate, fullerene, hole-blocking materials, or at least one of these.

[0036] In some embodiments, the hole-blocking material is BCP (Bath Copper Powder).

[0037] In some embodiments, the thickness of the metal electrode is 50–120 nm.

[0038] In some embodiments, the material of the metal electrode includes at least one of silver, gold, copper, aluminum, platinum, palladium, or tungsten.

[0039] A fourth aspect of the present invention provides an electrical device comprising the aforementioned perovskite heterojunction or the aforementioned perovskite battery.

[0040] In some implementations, the electrical equipment includes lighting elements, display elements, or automobiles.

[0041] The beneficial effects of this invention are: The reactive inert spacer layer in the perovskite heterojunction of the present invention alleviates the grain boundary etching problem that occurs in the traditional structure and realizes molecular passivation directly on the perovskite surface.

[0042] The microstructure and phases of the perovskite heterojunction of the present invention can still be well preserved after aging.

[0043] The perovskite solar cell of this invention forms a layered perovskite heterointerface on the electron extraction side. By controlling the bandgap arrangement and protecting the layered structure, charge transport characteristics and thin-film stability are improved. The device achieves a photoelectric conversion efficiency (PCE) as high as 26% and exhibits excellent stability under the standardized testing protocol of the International Organic Photovoltaic Stability Summit (ISOS): in damp heat testing (85°C, 85%RH) and maximum power point tracking testing under 1x sunlight irradiation, T... 90 The lifespan (the time required to maintain 90% efficiency) exceeds 1000 hours. Attached Figure Description

[0044] Figure 1The images show the lattice-resolved microstructure of the perovskite heterostructure interface; where a is a schematic diagram of the two-dimensional perovskite growth and distribution of the LSS sample; b, d, and e are cross-sectional high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM) images of the layered surface sample; f is the signal intensity line scan of the marked row in d; c, g, and h are cross-sectional HAADF-STEM images of the control sample; i is the signal intensity line scan of the marked row in g; the interlayer spacings for n=2, n=3, and n=5 are 2.20 nm, 2.94 nm, and 4.18 nm, respectively; j is the PEA... + It contains only CN σ bonds, while FA + It contains both CN σ bonds and π bonds; k is the NK-side signal extracted from the IV region of the LSS structure; I is the unnormalized NK-side spectrum of the IV region in k, showing that the I-IV region has obvious σ bond dominance (PEA). + The V region exhibits π-bond characteristics (FA). + The signal intensity at the N-K edge in region IV is higher than that in regions I-III. Region IV consists of the two-dimensional perovskite layer, the top region of the PCBM intermediate layer, the middle region of the PCBM intermediate layer, the PCBM / three-dimensional perovskite interface region, and the three-dimensional perovskite film bulk phase region.

[0045] Figure 2 This represents the near-surface grain boundary microstructure; where 'a' is a cross-sectional high-angle annular dark-field-scanning transmission electron microscope image of the control sample and the corresponding NBED image of the region; the scale bar is 5 nm. -1 b is a virtual DF-STEM image reconstructed based on the NBED signals in regions iii and iv of a; c is a cross-sectional HAADF-STEM image of the LSS sample and the corresponding NBED image of the region; scale bar is 5 nm. -1 ;d is a virtual DF-STEM image reconstructed based on the NBED signals in regions ii-iv of c.

[0046] Figure 3The photoelectric properties and stability of the perovskite thin film are shown in Figure 1. Here, a represents the XRD patterns of the original 3D perovskite, control sample, and LSS sample; b represents the normalized photoluminescence (PL) spectra of the original 3D perovskite, control sample, and LSS sample; c represents the photoluminescence images of the control sample and LSS sample at wavelengths of approximately 510 nm, 570 nm, and 780 nm, corresponding to n=1, n=2, and 3D layers, respectively; the scale bar is 1. μm; d and e are the steady-state PL spectra of the original three-dimensional perovskite, control sample, and LSS sample deposited on bare glass, excited from the glass side (d) and perovskite side (e), respectively; f and g are the time-resolved PL spectra of the original three-dimensional perovskite, control sample, and LSS sample deposited on bare glass, excited from the glass side (f) and perovskite side (g), respectively; the solid lines in f and g are the corresponding fitting curves of PL attenuation of LSS sample, control sample, and original three-dimensional perovskite sample; h is the two-dimensional peak evolution and three-dimensional band gap evolution of control sample and LSS sample obtained by tracking the UV-Vis spectrum at 40%RH; (LSS sample: three-dimensional perovskite sample with two-dimensional surface passivation treatment regulated by PCBM; control sample: three-dimensional perovskite sample with traditional two-dimensional surface passivation treatment; original three-dimensional perovskite sample: three-dimensional perovskite sample without two-dimensional surface passivation treatment).

[0047] Figure 4 The photovoltaic performance and long-term stability of PSCs are shown in Figure a; Figure a is a schematic diagram of the structure of an inverted perovskite solar cell device based on LSS; Figure b shows the performance of the original three-dimensional perovskite, the control sample, and the LSS perovskite solar cell. JV Curves (including reverse and forward scans); c is the energy level diagram of the original three-dimensional perovskite, control sample, and LSS perovskite solar cells obtained based on UPS data ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid, MeO-2PACz; copper phosphate, BCP); d is the maximum power point tracking stability of the control sample and LSS PSCs under continuous 1x sunlight irradiation in a nitrogen atmosphere; d is the initial PCE of devices with and without LSS, which are 21.69% and 23.72%, respectively; e is the stability of the control sample and LSS PSCs at 85%. PCE evolution under RH and 85℃ conditions (sample size n=13 for both types of samples); e represents the standard deviation of measurement for 5 test samples for each of the two types of samples; f and g are HAADF-STEM of the control sample and LSS sample after the same humid heat aging; (LSS sample: three-dimensional perovskite sample with PCBM-controlled two-dimensional surface passivation treatment; control sample: three-dimensional perovskite sample with traditional two-dimensional surface passivation treatment; original three-dimensional perovskite sample: three-dimensional perovskite sample without two-dimensional surface passivation treatment).

[0048] Figure 5FA with and without 5 mg / mL PCBM intermediate layer after PEAI treatment 0.9 Cs 0.1 Top-view SEM image of PbI3 film; a) FA treated with 5 mg / mL PCBM interlayer and 10 mg / mL PEAI isopropanol solution. 0.9 Cs 0.1 Top-view SEM image of PbI3 film; b is a magnified SEM image of the area marked by the orange box in a; c is the FA treated with 10 mg / mL PEAI isopropanol solution. 0.9 Cs 0.1 Top-view SEM image of PbI3 thin film; d is a magnified SEM image of the area marked by the orange box in c; scale bar: 1 μm.

[0049] Figure 6 FA treated with different concentrations of PEAI 0.9 Cs 0.1 Top-view SEM images of PbI3 films; where a, f, and a' represent FA films treated with 0, 1 mg / mL, 3 mg / mL, 5 mg / mL, 10 mg / mL, and 15 mg / mL PEAI isopropanol solutions, respectively. 0.9 Cs 0.1 Top-view SEM image of PbI3 thin film; scale bar: 1 μm.

[0050] Figure 7 Cs treated with different concentrations of PEAI 0.1 FA 0.9 Cross-sectional HAADF-STEM images of PbI3 films; where a, f, and a' represent three-dimensional Cs treated with PEAI isopropanol solutions at concentrations of 0, 1 mg / mL, 3 mg / mL, 5 mg / mL, 10 mg / mL, and 15 mg / mL, respectively. 0.1 FA 0.9 Cross-sectional high-angle annular dark-field scanning transmission electron microscope image of a PbI3 thin film; scale bar: 100 nm.

[0051] Figure 8 The image shows the morphology of the two-dimensional perovskite layer on the three-dimensional perovskite film prepared using a dilute PEAI solution without a PCBM interlayer; a and b are SEM and cross-sectional HAADF-STEM images of the two-dimensional perovskite layer (located on top of the three-dimensional perovskite film) prepared using 3 mg / mL PEAI, respectively; c and d are top-view SEM and cross-sectional HAADF-STEM images of the two-dimensional perovskite layer (located on top of the three-dimensional perovskite film) prepared using 5 mg / mL PEAI, respectively.

[0052] Figure 9FA with different concentrations of PCBM interlayer and treated with 10 mg / mL PEAI 0.9 Cs 0.1 Top-view SEM images of PbI3 films; where a, f, and a, respectively, are FA films treated with 10 mg / mL PEAI isopropanol solution after having PCBM interlayers with concentrations of 0, 1 mg / mL, 2 mg / mL, 3 mg / mL, 5 mg / mL, and 10 mg / mL. 0.9 Cs 0.1 Top-view SEM image of PbI3 thin film; scale bar: 1 μm.

[0053] Figure 10 For EELS STEM analysis; where a and b are FAs treated with 10 mg / mL PCBM intermediate layer and 10 mg / mL PEAI isopropanol solution. 0.9 Cs 0.1 A cross-sectional high-angle annular dark-field scanning transmission electron microscope image of PbBr3 perovskite; the green rectangular region of b represents I(M 4,5 The scanning area of ​​the EELS signal, the blue rectangular area is Br(L) 2,3 (c) is the scanning area of ​​the EELS signal; (d) are the EELS mapping images of the corresponding iodine and bromine signals; (e) and (f) are the signal intensity line profiles marked by yellow-orange arrows in (c) and (d).

[0054] Figure 11 EELS ELNES analysis of the LSS structure; a and c are the NK-side signals extracted from region IV of two different regions of the LSS structure; b and d are the unnormalized NK-side spectra of region IV in a and c, respectively, showing clear σ bond dominance in regions I-IV (PEA). + Features, and π bond features in region V (FA) + The signal intensity of the N-K edge in region IV is higher than that in regions I-III; region IV refers to the two-dimensional perovskite layer, the top region of the PCBM intermediate layer, the middle region of the PCBM intermediate layer, the PCBM / three-dimensional perovskite interface region, and the three-dimensional perovskite thin film region in sequence.

[0055] Figure 12 A is a two-dimensional perovskite monolayer on a three-dimensional perovskite grain; a and b are FAs with 2 mg / mL and 10 mg / mL PCBM intermediate layers, respectively, and both treated with 10 mg / mL PEAI isopropanol solution. 0.9 Cs 0.1 Cross-sectional HAADF-STEM images of PbI3 perovskite solar cells; c and d are signal intensity line profiles of rows marked with yellow arrows in a and b, respectively.

[0056] Figure 13 FA with different concentrations of PCBM interlayer and treated with 10 mg / mL PEAI 0.9 Cs 0.1 HAADF-STEM images of cross-sections of PbI3 thin films; af are cross-section HAADF-STEM images of perovskite solar cells with 0, 1 mg / mL, 2 mg / mL, 3 mg / mL, 5 mg / mL, and 10 mg / mL PCBM interlayers and treated with 10 mg / mL PEAI isopropanol solution, respectively; scale bar: 100 nm.

[0057] Figure 14 The control sample is a two-dimensional perovskite with different orientations; cross-sectional HAADF-STEM image of the control sample treated with 10 mg / mL PEAI; Fast Fourier Transform (FFT) of regions 1 and 2 shows that the two-dimensional n=2 perovskite on the three-dimensional perovskite surface has different orientations.

[0058] Figure 15 The n-value arrangement of two-dimensional perovskites in the control sample; cross-sectional HAADF-STEM image of the control sample treated with 10 mg / mL PEAI and line profile of the area indicated by the red arrow.

[0059] Figure 16 The distribution of two-dimensional perovskite on the surface and grain boundaries of three-dimensional perovskite grains in the control sample is shown. Among them, a is a cross-sectional HAADF-STEM image of the control sample treated with 5 mg / mL PEAI; b and c are magnified HAADF-STEM images of the selected area in a; d and e are the corresponding signal intensity line profiles of the rows marked by arrows in b and c.

[0060] Figure 17 PbI2 is the residual PbI2 in the three-dimensional perovskite of the control sample; cross-sectional HAADF-STEM image of the control sample treated with 10 mg / mL PEAI; a is PbI2 in the three-dimensional perovskite grains; b is a magnified image of the selected area in a.

[0061] Figure 18 FA lost from the three-dimensional perovskite surface in the control sample + / Cs + / I - Cross-sectional STEM images of the control sample treated with 10 mg / mL PEAI; where a is a HAADF-STEM image of the three-dimensional perovskite grains; b is a magnified image of a selected region in a; c is an atomic resolution i-DPC-STEM image of the region in a; after treatment with PEAI solution, some FA + / Cs + / I -It will be lost from the surface of the three-dimensional grains.

[0062] Figure 19 Two-dimensional perovskites parallel and non-parallel to the three-dimensional grain surface in the control sample; cross-sectional HAADF-STEM images of the control sample treated with 10 mg / mL PEAI; a) two-dimensional perovskites growing simultaneously on the three-dimensional grain surface, both parallel and non-parallel; b) high-resolution image of non-horizontal two-dimensional perovskites; c) FFT of the selected region in b.

[0063] Figure 20 The n-value arrangement of two-dimensional perovskites in the LSS sample; cross-sectional HAADF-STEM image (left) and line profile (right) of the region indicated by the yellow arrow in the LSS sample treated with 10 mg / mL PEAI (containing a 5 mg / mL PCBM intermediate layer).

[0064] Figure 21 LSS samples prepared on three-dimensional perovskites with different [PbI2] ratios are shown; where a and b are the XRD results (FAI) of three-dimensional perovskites with different PbI2 ratios and their corresponding prepared LSS samples, respectively. 0.9 ·(CsI) 0.1 ·(PbI2) 0.85 (FAI) 0.9 ·(CsI) 0.1 (PbI2)1 and (FAI) 0.9 ·(CsI) 0.1 ·(PbI2) 1.15 c is a STEM-HAADF image of the LSS-0.85PbI2 sample; d is a magnified image of the boxed area in c, showing a two-dimensional perovskite with n=2 phase; e is a STEM-HAADF image of the LSS-1.15PbI2 sample; f is a magnified image of the boxed area in e, showing a two-dimensional perovskite with n=1 and n=2 phases.

[0065] Figure 22 Dark-field STEM image reconstructed from nanobeam diffraction of a control sample; scale bar: 50 nm.

[0066] Figure 23 Dark-field STEM image reconstructed from selected nanobeam diffraction of LSS sample; scale bar: 50 nm.

[0067] Figure 24 XRD patterns of pure three-dimensional, control, and LSS thin films.

[0068] Figure 25The environmental stability test results are for the control film and the LSS film; a and b are the UV-Vis spectra of the control film and the LSS film stored at 75±10% relative humidity for 55 days, respectively; the insets in a and b show the evolution of the three-dimensional bandgap at different aging times.

[0069] Figure 26 For having Cs 0.05 (MA 0.05 FA 0.95 ) 0.95 Pb(I 0.95 Br 0.05 )3. The UV-Vis absorption spectra of pure three-dimensional perovskite composition, control and LSS film.

[0070] Figure 27 To optimize the performance of pin perovskite solar cells, the concentrations of PEAI and PCBM used to form LSS were adjusted; a and b show LSS perovskite solar cells with different PEAI and PCBM concentrations. JV Curves; and compared with pure three-dimensional devices and control devices. JV The curves were compared.

[0071] Figure 28 For different pin PSC JV Hysteresis analysis of the curves; ag represents pure three-dimensional (a), control (b), and LSS (cg) PSC with different PCBM concentrations in forward and reverse scans, respectively. JV Curve; h represents the evolution of the hysteresis index with increasing PCBM concentration; PEAI concentration is 5 mg / mL.

[0072] Figure 29 Photovoltaic parameters of pin 3D-2D devices with or without a PCBM intermediate layer ( V oc J Statistical distributions of SC, FF, and PCE (sample size n=50); three-dimensional devices were used as a reference; box plots show the mean, median line, 25-75% box limit, and dashed lines at 1.5 times the interquartile range; the concentrations of PEAI and PCBM were both 5 mg / mL; the mean PCE significantly increased from 17.27% in the pure three-dimensional device to 22.98% in the control, and further increased to 24.69% in the LSS; this improvement was attributed to V The voltage was increased from 1.054V to 1.163V and 1.192V. J sc from 22.58 mA / cm 2 Increased to 23.99 mA / cm 2 and 24.64 mA / cm 2Furthermore, the FF increased from 72.47% to 82.38% and 84.10%; in addition, it is worth noting that the LSS device exhibits a narrower distribution across all photovoltaic parameters than the pure 3D and control devices, demonstrating the excellent reproducibility of the current LSS strategy.

[0073] Figure 30 In the middle, 'a' represents the best-performing CsFAMA 3D device (22.60 mA / cm²). 2 ), control device (23.71 mA / cm) 2 ) and LSS devices (24.18 mA / cm 2 (a) shows the external quantum efficiency curve and integrated current density curve; (b) shows the external quantum efficiency curve and band gap measurement of the LSS perovskite solar cell.

[0074] Figure 31 A summary of reported open-circuit voltage values ​​for representative PSCs of different bandgap bands.

[0075] Figure 32 The images show the helium La (21.22 eV) spectra of the secondary electron cutoff edge (a) and valence band spectrum (b) of different thin films; and the helium La (21.22 eV) spectra of the secondary electron cutoff edge (c) and valence band spectrum (d) of the PCBM electron transport layer.

[0076] Figure 33 Mott-Schottky for pure three-dimensional, control, and LSS devices ( MS ) curve; through application MS Relationship, capacitance-voltage characteristics ( C - V This can reflect the interface charge density, which is related to... MS The slope of a curve is proportional to the reciprocal of the slope of a straight line; the slope of an LSS device (5.7 × 10⁻⁶) 17 ) is greater than pure three-dimensional (3.5×10) 17 ) and control (0.4×10 16 The LSS device showed less charge accumulation at the perovskite-PCBM interface; the rapid charge transfer at the interface was attributed to optimized interface band alignment induced by the PCBM intermediate layer; furthermore, compared with the pure 3D (0.66 V) and control (0.93 V) devices, the LSS device exhibited a higher built-in potential. V bi The value is 0.98 V.

[0077] Figure 34 For comparison and normalized photovoltaic parameters (PCE, ...) of LSS PSC under continuous single-sun illumination in N2 atmosphere. V OC , J SCThe evolution of (FF) (sample size n is 5 in both cases); the error bar represents the standard deviation of the measurements obtained from five samples in each of the two cases.

[0078] Figure 35 The evolution of series resistance and shunt resistance in comparison (a) and LSS PSC (b) under continuous single sunlight in N2 atmosphere is shown.

[0079] Figure 36 For comparison and LSSPSC initial PCE statistics (sample size n=13); box plots show the mean, median line, 25-75% box limit, and dashed line at 1.5 times interquartile range.

[0080] Figure 37 STEM-HAADF characterization of the control and LSS device samples before MPP stability testing; a) STEM-HAADF image of the original control device without PCBM intermediate layer; b) Enlarged STEM-HAADF image of the boxed area in a, showing the two-dimensional and three-dimensional perovskite structures; c) STEM-HAADF image of the original LSS device; d) Enlarged STEM-HAADF image of the boxed area in c, showing the LSS structure.

[0081] Figure 38 STEM-HAADF characterization of the control and LSS devices after 15 days of MPP operation; a) The grain boundary region of the control device shows severe damage; b) The enlarged STEM-HAADF image of the boxed area in a shows the presence of PbI2; c) The LSS device shows only slight damage, mainly occurring at the buried interface; d) The LSS structure remains intact.

[0082] Figure 39 SEM images of the control and LSS samples to characterize environmental degradation; a and b are SEM images of the control samples stored at 50-60% relative humidity for 0 days and 15 days, respectively; c and d are SEM images of the LSS samples stored at 50-60% relative humidity for 0 days and 15 days, respectively.

[0083] Figure 40 STEM-HAADF characterization of the control and LSS devices under environmental degradation; a) STEM-HAADF image of the control device stored at 50-60% relative humidity for 15 days; b) magnified image of the boxed area in a, showing the presence of a large amount of PbI2; c) STEM-HAADF image of the LSS device with minimal changes after environmental storage; d) magnified image of the boxed area in c, showing that the complete LSS structure is preserved.

[0084] Figure 41The effect of solvent treatment on the surface of the three-dimensional perovskite film is shown in Figures a and b. SEM images of the three-dimensional perovskite after cleaning with isopropanol are shown in Figures c and d. SEM images of the three-dimensional perovskite after cleaning with chlorobenzene are shown in Figures e. XRD results of the three-dimensional perovskite after treatment with isopropanol and chlorobenzene are shown in Figures e. Detailed Implementation

[0085] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0086] Chemicals and Materials Lead iodide and lead bromide (PbI2 and PbBr2, >99.99%) were purchased from Tokyo Chemical Industry Co., Ltd. (TCI). Formamidinium iodide (FAI) and methylamine chloride (MACl, >99.99%) were purchased from Greatcell Solar Inc. 4-tert-butylpyridine (4-TBP, 96%), lithium bis(trifluoromethane)sulfonylimide (Li-TFSI, 99.95%), N,N-dimethylaniline (DMF), dimethyl sulfoxide (DMSO), acetonitrile (ACN), chlorobenzene (CB), ethyl acetate (EA), and isopropanol (IPA) were purchased from Merck. [6,6]-phenyl-C 61 methyl butyrate (PCBM), C 60 Copper phosphate (BCP), phenylethylammonium iodide (PEAI), and phenylethylammonium bromide (PEABr) were purchased from Xi'an Baolai Optoelectronic Technology Co., Ltd. Tin oxide (15 wt% aqueous colloidal dispersion) and cesium iodide (CsI, >99.998%) were purchased from Alfa Aesar. Spiro-OMeTAD (99.8%) was purchased from Borun Chemical Co., Ltd. MeO-2PACz was purchased from Tokyo Chemical Industry Co., Ltd. All materials were used directly without further purification.

[0087] Example 1 This embodiment prepares a thin film, and the specific process is as follows: The ITO substrate was ultrasonically treated with deionized water, acetone, and isopropanol (20 min each time), followed by ultraviolet ozone treatment. The tin oxide colloid was diluted with deionized water at a volume ratio of 1:5, filtered, and then uniformly spin-coated at 3000 rpm for 30 s, followed by annealing at 180°C for 30 min.

[0088] To prepare FA 0.9 Cs 0.1PbI3 perovskite films were prepared by dissolving PbI2 (645.4 mg), FAI (216.7 mg), CsI (36.4 mg), and MACl (28.3 mg) in 1 mL of a DMF / DMSO mixed solvent (4:1, v / v) to prepare a 1.4 M precursor solution. The mixture was stirred overnight at room temperature and filtered through a 0.22 μm syringe filter before use. Perovskite films were prepared by a two-step continuous spin-coating method: spin-coating at 1000 rpm for 10 s and then at 4000 rpm for 30 s. During the second spin-coating step, 200 μL of ethyl acetate was dropped onto the substrate 20 s before the end of the program. The substrate was then placed on a hot plate and annealed at 160 °C for 10 min to form FAI. 0.9 Cs 0.1 PbI3 perovskite thin films. First, the prepared three-dimensional perovskite thin films were spin-coated with different concentrations of PCBM chlorobenzene solution at 3000 rpm for 30 s to form an intermediate layer. Then, the cooled three-dimensional perovskite thin films were spin-coated with different concentrations of PEAI isopropanol solution at 3000 rpm for 30 s. Finally, they were annealed at 100℃ for 10 min to obtain layered surface samples (LSSPSCs).

[0089] The concentrations of the PCBM solution were 1 mg / mL, 2 mg / mL, 3 mg / mL, 5 mg / mL and 10 mg / mL, and PCBM intermediate layers with a thickness of 0-60 nm were prepared.

[0090] The concentrations of PEAI isopropanol solutions were 1 mg / mL, 3 mg / mL, 5 mg / mL, 10 mg / mL, and 15 mg / mL.

[0091] Example 2 This embodiment prepares a thin film, and the specific process is as follows: Based on the thin film prepared in Example 1, a spin-coated Spiro-OMeTAD layer and a thermally evaporated gold layer were sequentially deposited on the perovskite thin film. To avoid the potential influence of the subsequently deposited PCBM layer in the pin structure on the analysis of the original state of the layered structure surface, nip structure devices instead of pin structure devices were fabricated for scanning transmission electron microscopy (STEM) samples.

[0092] Example 3 This embodiment prepares a thin film, which differs from Example 1 in that FA is used. 0.9 Cs 0.1 PbI3 perovskite film replaced with FA 0.9 Cs 0.1 PbBr3 perovskite films were subjected to the same PCBM and PEAI treatments.

[0093] Comparative Example 1 This comparative example prepared a thin film, which differed from Example 1 in that the cooled three-dimensional perovskite thin film was directly spin-coated with PEAI isopropanol solution of different concentrations at a speed of 3000 rpm for 30s, and then annealed at 100℃ for 10min without PCBM treatment, thus obtaining the control sample.

[0094] Comparative Example 2 This comparative example prepared a thin film, which differs from Example 2 only in that the thin film prepared in Example 1 is replaced with the thin film prepared in Comparative Example 1.

[0095] Example 4 This embodiment demonstrates the fabrication of an inverted perovskite solar cell, the specific process of which is as follows: In a nitrogen-filled glove box, a MeO-2PACz layer (1 mg / mL isopropanol solution) was spin-coated onto ITO glass at 3000 rpm for 30 s, followed by annealing at 100 °C for 10 min. This process was used to prepare Cs. 0.05 (MA 0.05 FA 0.95 ) 0.95 Pb(I 0.95 Br 0.05 3. For the perovskite layer, a 1.5 M precursor solution was prepared by dissolving PbI₂ (676.8 mg), FAI (232.8 mg), CsI (19.5 mg), PbBr₂ (41.3 mg), and MACl (35.2 mg) in 1 mL of a DMF / DMSO mixed solvent (volume ratio 4:1). The mixture was stirred overnight at room temperature and filtered through a 0.22 μm syringe filter before use. The resulting perovskite precursor solution was spin-coated at 4000 rpm for 40 s, and 200 μL of ethyl acetate was used as the antisolvent at the 30th s. The film was annealed at 120 °C for 20 min. For the intermediate layer, the three-dimensional perovskite film was first spin-coated with different concentrations of PCBM chlorobenzene solution at 3000 rpm for 30 s, and then spin-coated with PEAI solution (different concentrations of PEAI isopropanol solution) at 3000 rpm for 30 s, and annealed at 100 °C for 10 min. After film formation, the PCBM (20 mg / mL chlorobenzene solution) layer and the BCP (0.7 mg / mL isopropanol solution) film were spin-coated at 2000 rpm and 4000 rpm for 20 s, respectively, and then annealed at 70 °C for 10 min. Finally, the film was viewed through a mask (0.09 cm²). 2 A 100 nm thick Ag layer was evaporated and deposited on the active region to obtain a layered surface device.

[0096] Comparative Example 3 This comparative example prepared an inverted perovskite solar cell. The difference from Example 4 is that the cooled three-dimensional perovskite film was directly spin-coated with PEAI isopropanol solution of different concentrations at 3000 rpm for 30s, and then annealed at 100℃ for 10min without PCBM treatment, thus obtaining the control device.

[0097] Experimental Example 1 This experimental example demonstrates the STEM characterization of the thin films prepared in Example 2 and Comparative Example 2. The specific process is as follows: Cross-sectional TEM samples of control samples and LSS PSCs were prepared using a dual-beam focused ion beam (FIB) nanofabrication platform (Helios 5CX, Thermo Fisher Scientific). First, a 0.3 μm thick platinum (Pt) protective layer was deposited on the surface of the device's metal electrodes using electron beam deposition, followed by a 3 μm thick platinum protective layer deposited using an ion beam to further protect the sample area. The gallium ion beam operated at a voltage of 30 kV, and the working current range for wafer fabrication was 0.1–47 nA. Subsequently, the wafer was extracted from the substrate and directly transferred to the transmission electron microscope half-gate within the focused ion beam chamber. The observation area of ​​the wafer was thinned to less than 100 nm using a gallium ion beam with a current range of 40–790 pA, followed by precise grinding and polishing using an ion beam with an accelerating voltage as low as 1 kV and a working current of 72 pA. The wafer was then coated using a high-vacuum coating machine (Leica ACE 600) at a speed of 1 × 10⁻⁶. -4 Under a pressure of mbar, a 10 nm thick carbon layer was deposited on both sides of the cross-sectional sample prepared by focused ion beam for further protection. The cross-sectional sample was observed using an aberration-corrected scanning / transmission electron microscope (Spectra-300, Thermo Fisher Scientific) equipped with a field emission gun at an accelerating voltage of 300 kV. The probe convergence half-angle was 24.5 mrad, and the receiving half-angle range of the high-angle annular dark-field detector was 79.5–200 mrad. When acquiring high-angle annular dark-field scanning transmission electron microscope images, the exposure time per pixel was 6 μs. All scanning transmission electron microscope images in this experiment were 2048 × 2048 pixels in size. The frame size of the high-resolution scanning transmission electron microscope images was approximately 200 × 200 nm. 2Electron energy loss spectroscopy (EES) datasets were acquired using a Gatan K3 single-electron counting direct probe camera with an electron beam current of 25 pA. A dual-electron EES mode with a dispersion of 0.18 eV / channel, covering an energy range of 622 eV, was employed to capture NK-edge, I M-edge, and Br L-edge signals. To obtain a better signal-to-noise ratio, I and Br signals were detected at the same location with different acquisition energy ranges (I M-edge: 380 eV to 1002 eV; Br L-edge: 1200 eV to 1822 eV). For four-dimensional scanning transmission electron microscopy (STEM) measurements, an electron probe with a convergence angle of 1 mrad was used, and the beam current was reduced to below 1 pA (approximately 0.2 pA) to minimize the electron dose below the radiation damage threshold. The four-dimensional STEM datasets were acquired using a pixelated electron detector (EMPAD) with a single exposure time of 1 ms and a size of 512 × 512 pixels. Therefore, the cumulative electron dose in the 300 nm × 300 nm acquisition region was approximately 36 e·Å. 2 This is lower than the critical electron dose (50 e·Å) for beam damage in organic-inorganic hybrid perovskite samples reported in the existing literature. 2 ).

[0098] To gain a deeper understanding of perovskite heterostructures, low-dose scanning transmission electron microscopy (STEM) was used to study the cross-sectional microstructure of the thin film. Several studies have confirmed that cross-sectional STEM observation can obtain lattice-resolved information on the interfacial microstructure. For example... Figure 1 As shown in Figure a, the ultrathin PCBM interlayer sandwiched in the middle acts as an inert "molecular sieve," allowing controlled ion permeation and exchange between the three-dimensional perovskite surface and the two-dimensional molecular salt. The PCBM-regulated interfacial reaction rate is significantly reduced, enabling the formation of a uniform layered surface microstructure. Figure 1 Figures b and c show low-magnification scanning transmission electron microscope images of the layered surface sample of Example 2 and the control sample of Comparative Example 2 in high-angle annular dark field (HAADF) mode. Figure 1 Figure b shows that, compared to the control sample under the same PEAI treatment conditions, the layered surface sample retained the complete three-dimensional perovskite grain surface. Measured from high-angle annular dark-field scanning transmission electron microscopy images, the characteristic thickness of the PCBM intermediate layer (dark contrast interlayer) is approximately 10 nm, above which is a continuous, uniform two-dimensional perovskite layer (approximately 10 nm, typically 5-15 nm thick). In contrast, as... Figure 1As shown in c, in the control film, the three-dimensional perovskite grains after PEAI treatment did not retain their original surface microstructure. Instead, a discontinuous layer composed of randomly distributed two-dimensional perovskite crystals formed above the three-dimensional perovskite grains. This layer had a large thickness variation (15-50 nm), and the original three-dimensional perovskite grain surface showed partial degradation. Figure 1 (c) This surface irregularity originates from the three-dimensional perovskite surface and the two-dimensional organic spacer cation PEA. + The cation exchange reactions are uneven and intense. Notably, increasing the PEAI concentration leads to an increase in the thickness and coverage of the two-dimensional perovskite; however, when the PEAI concentration increases to 15 mg / mL, surface degradation becomes more pronounced. Figure 6 and Figure 7 Even when PEAI is diluted to 3 mg / mL or 5 mg / mL, the formation of two-dimensional perovskites still leads to significant erosion of the three-dimensional grain surface. Figure 8 ).

[0099] However, in the layered surface samples, the ultrathin PCBM intermediate layer, composed of closely packed spherical molecules, contains nanochannels that allow PEA to pass through during thermal annealing. + FA + / Cs + / I - and Pb² + Stable interlayer transport is achieved, thus slowing down the reaction process. Equally important, the chemically inert PCBM interlayer geometrically restricts the growth of the resulting two-dimensional perovskite and molecular passivation layers. These factors collectively promote lateral uniformity of the reaction front, which is crucial for controlling interface morphology and minimizing the impact on the surface microstructure of the three-dimensional perovskite grains. Figure 9 ).

[0100] In Example 3, the use of bromide samples instead of iodide samples helps distinguish between halide anions provided by PEAI during the reaction and those provided by the surface regions of the three-dimensional perovskite grains. Scanning transmission electron microscopy-electron energy loss spectroscopy (EELS) analysis revealed I... - and Br - The coexistence of these elements confirms that bidirectional ion exchange occurred between PEAI salt and the surface of the three-dimensional grains through the PCBM interlayer. Figure 10 ). To study PEA + The distribution of nitrogen (N) K-edge energy loss near-edge structures (ELNES) in the layered structure surface was analyzed. Figure 1 (jl in the middle). In the two-dimensional perovskite layer and PCBM intermediate layer ( Figure 1In the i-iv region of k in PEA, the N K-edge structure has a main peak at 408.5 eV and a small preceding peak at 400.5 eV, which is consistent with the dominant CN σ bond characteristics (π bonds around 400 eV and σ bonds around 408 eV), confirming the PEA + The existence of (Chen, J., Quan, Ultramicroscopy 215, 113006 (2020); Figure 1 j in the middle layer of the PCBM. Additionally, below the intermediate layer of the PCBM ( Figure 1 The increase in signal strength in the N K-edge region (in the j-iv region) indicates that PEA + It accumulates on the surface of three-dimensional grains. This PEA + The enrichment on the surface of three-dimensional grains is evident in multiple layered structure surface regions. Figure 11 Therefore, two-dimensional monolayers can be observed in specific regions on the surface of three-dimensional grains. Figure 12 This indicates the presence of residual PEA. + Two-dimensional molecular passivators that tend to form covering three-dimensional grains.

[0101] Based on this mechanism, it was found that the thickness of the PCBM interlayer affects the microstructure and phase composition of the two-dimensional perovskite capping layer. PCBM interlayers with thicknesses ranging from 0 to 60 nm were prepared by spin-coating PCBM solutions with concentrations of 1 mg / mL, 2 mg / mL, 3 mg / mL, 5 mg / mL, and 10 mg / mL. Figure 13 As shown, with increasing PCBM thickness, the two-dimensional perovskite capping layer tends to become smoother and more continuous. However, when the PCBM concentration reaches 10 mg / mL, the interlayer thickness can reach 60 nm. A thicker PCBM interlayer hinders ion exchange, causing the two-dimensional layer to lose its continuity and its thickness to decrease significantly. The dependence of interfacial reaction kinetics on the PCBM interlayer thickness is consistent with the previously proposed PCBM regulation mechanism.

[0102] The distribution and orientation of the n-value in two-dimensional perovskites are crucial for bandgap modulation and carrier transport, and these aspects require further investigation. For the control sample in Comparative Example 2, which lacks an intermediate layer, Figure 1High-magnification, high-angle annular dark-field-scanning transmission electron microscope images of the selected regions in c and g show that multiple layers of two-dimensional perovskites of varying thicknesses are formed on the surface of the obviously rough three-dimensional grains. Figure 1 h in Figure 1 A magnified image of the direction and region indicated by the arrow in 'g'. Figure 1 i in Figure 1 The signal strength line scan diagram for region h is shown in the figure. Figure 1 The two-dimensional perovskite structure in h and Figure 1 The interlayer spacing measured in i is highly correlated. Line scan studies show that the n-values ​​of the two-dimensional perovskites in the control sample are disordered, with the main component being n=2 (interlayer spacing d=2.20 nm), while two-dimensional perovskites with n=3 (interlayer spacing d=2.94 nm) and n=5 (interlayer spacing d=4.18 nm) also exist. Furthermore, it was noted that on the smooth surface of the three-dimensional grains, the two-dimensional perovskites with the same n-value in the control sample exhibit different orientations (…). Figure 14 At undulating grain boundaries, it is common to find high-n-value two-dimensional perovskites doped with low-n-value two-dimensional perovskites. Figure 15 and Figure 16 This can be attributed to the rapid formation of two-dimensional perovskites when the PEAI solution comes into contact with the surface of three-dimensional grains. + With residual PbI2 ( Figure 17 The interaction between ) and the abundant FA on the surface of three-dimensional grains + / Cs + / I - ( Figure 18 This increases the likelihood that some two-dimensional perovskites with non-uniform n values ​​cannot grow along in-plane orientation, and may cause greater damage to three-dimensional grains. Figure 19 ).

[0103] For the layered surface sample of Example 2, at different magnifications Figure 1 b and Figure 1 The diagram clearly illustrates the layered lattice structure of the two-dimensional perovskite. By spin-coating a PEAI solution onto the intermediate layer, rather than directly onto the three-dimensional perovskite grains, an ultrathin two-dimensional perovskite layer was formed, for example... Figure 1 The two octahedral layers of n=2 two-dimensional perovskite shown in e and f are... Figure 1 The magnified image and corresponding intensity line scan of the area indicated by the arrow in section d are shown. Due to the protective effect of the PCBM, PEA in the layered structure surface sample is... + It is difficult to bind enough A-site ions and [PbI4] 2-This makes it difficult for two-dimensional perovskites with n>2 to crystallize. Furthermore, the difficulty of forming high-n-value two-dimensional perovskites gradually increases with the increase of the distance from the surface of three-dimensional grains. This allows two-dimensional perovskites in layered structures to be arranged from n=2 to n=1 (…). Figure 20 This helps improve carrier transport efficiency in pin devices. Furthermore, the PbI2 content in three-dimensional perovskites may also affect the n-phase of two-dimensional perovskites in layered surface samples. For example... Figure 21 As shown, the lack of PbI2 may hinder the formation of n=1 phase two-dimensional perovskites, while the proportion of the n=1 phase tends to increase when PbI2 is in excess. Figure 21 (a, b) in the text. Scanning transmission electron microscopy observation also showed that using (FAI) 0.9 (CsI) 0.1 (PbI2) 1.15 In the layered surface samples prepared from three-dimensional perovskites, there were more n=1 phase two-dimensional perovskites. Figure 21 f in the middle.

[0104] The interaction between PEAI salt and three-dimensional perovskite may also affect the integrity of near-surface grain boundaries, which is crucial for the performance of the final perovskite solar cell device. Since conventional scanning transmission electron microscopy (STEM) imaging is insufficient to reveal the underlying crystal structure, a combination of four-dimensional scanning transmission electron microscopy (4D-STEM) and nanobeam electron diffraction (NBED) techniques was used to investigate the microstructure and lattice orientation distribution of control samples and layered surface samples. In the control film without an ultrathin PCBM interlayer, high-angle annular dark-scanning transmission electron microscopy revealed a dark contrast region beneath the surface of the three-dimensional grains. Figure 2 (a) in the diagram, obtained through the corresponding nanobeam electron diffraction pattern ( Figure 2 The region i of a in the equation determines that this region is a two-dimensional perovskite with n=2, which is almost perpendicular to the two-dimensional perovskite above the three-dimensional grain. Figure 2 (Region ii of a in the text). Nanobeam electron diffraction pattern of three-dimensional grains ( Figure 2 Regions iii and iv of a in the space group exhibit a typical orthogonal structure (space group) Pbnm , a =0.8646 nm, b =0.8818 nm, c =1.2520 nm), with the left and right parts exhibiting different orientations. To accurately characterize the deformation of the three-dimensional grains, virtual dark-field scanning transmission electron microscopy images were reconstructed from a four-dimensional diffraction dataset ( Figure 2 b and Figure 22 The image clearly shows that the grain boundaries and adjacent regions of the three-dimensional grains have been eroded by two-dimensional perovskite growing along the grain boundaries.

[0105] In contrast, high-angle annular dark-field-scanning transmission electron microscopy images of the layered surface sample show a clear separation between the three-dimensional grains and the two-dimensional perovskite through a thin PCBM interlayer. Figure 2 (c in the text) Figure 2 The nanobeam electron diffraction pattern (region i) of c in the image shows that the orientation of the two-dimensional perovskite layer is approximately parallel to the surface of the three-dimensional grain. In this case, three three-dimensional perovskite grains with different orientations can be distinguished from the four-dimensional diffraction dataset. Figure 2 Nanobeam electron diffraction patterns of c in regions ii-iv and Figure 23 Reconstructed dark-field scanning transmission electron microscopy image ( Figure 2 d) confirms that the surface and grain boundaries of the three-dimensional grains are well preserved, and no etching of the grain boundaries by the two-dimensional perovskite is observed, which highlights the protective role of the PCBM intermediate layer.

[0106] Experimental Example 2 The material characterization process in this experiment is as follows: Scanning electron microscopy (SEM) images were acquired using a Helios 5CX with an electron beam voltage of 3 kV and a current of 86 pA. Absorbance was characterized using a UV-Vis spectrophotometer (PerkinElmer Lambda 35 UV-Vis-NIR). Grazing-incidence X-ray diffraction analysis was performed at a 1° incident angle on a RigakuSmartLab 3kW. UV photoelectron spectroscopy was performed using a VG Scienta R4000 analyzer with a HeI (21.22 eV) emission line as the excitation source and a bias voltage of -5 V. Steady-state photoluminescence spectra were obtained using a pulsed laser as the photoexcitation source (wavelength 470 nm; Horiba Fluorolog FL-3), and time-resolved photoluminescence experiments were performed with 470 nm excitation. Mott-Schottky plots were measured using a CHI660E at a frequency of 1 kHz with a bias voltage of 0–1.4 V. Fluorescence confocal images were obtained using a laser scanning fluorescence confocal microscope (Leica TCS SP8) under 488nm laser excitation.

[0107] The surface condition of the three-dimensional perovskites prepared in Example 1 and Comparative Example 1 after treatment with isopropanol or chlorobenzene was examined by scanning electron microscopy (SEM). Figure 41 ).like Figure 41 As shown in the figure, the three-dimensional samples treated with isopropanol and chlorobenzene show very little difference in surface morphology and characteristics. Furthermore, X-ray diffraction results ( Figure 41 e) shows no significant change, indicating that isopropanol or chlorobenzene treatment has no significant effect on surface condition.

[0108] The surface morphology of the layered structure surface sample of Example 1 and the control sample of Comparative Example 1 were compared using SEM. Figure 5 As shown, when using the PCBM intermediate layer, the perovskite film after PEAI deposition exhibits uniform contrast under a scanning electron microscope, indicating that the two-dimensional perovskite coverage is uniform and retains the morphology of the original three-dimensional perovskite. Figure 5 (a, b) In contrast, the two-dimensional perovskite phase distribution of the control sample is irregular ( Figure 5 (c and d in the text).

[0109] X-ray diffraction (XRD) analysis was performed on the layered surface samples and control samples. Figure 3 (a) In both cases, passivation treatment did not significantly alter the crystallinity and grain orientation of the original three-dimensional perovskite film. Figure 24 Nevertheless, the use of the PCBM intermediate layer still affected the overall phase distribution and orientation of the formed two-dimensional perovskite capping layer. Furthermore, according to the normalized photoluminescence (PL) spectrum (… Figure 3 (b) No band gap was observed in the underlying three-dimensional perovskite. E g Significant changes occurred, further demonstrating the integrity of the bulk three-dimensional perovskite phase in both the layered surface sample and the control sample. Interestingly, the photoluminescence spectrum of the layered surface sample showed dominant emission peaks corresponding to n=1 and n=2, while the photoluminescence emission associated with n≥3 was more significant in the control sample. Figure 3 (b) This is consistent with the observations from scanning transmission electron microscopy.

[0110] like Figure 3 As shown in a, in the LSS sample, both the n=1 phase and the n=2 phase show obvious XRD diffraction peaks. Figure 3 In sample b, the LSS sample mainly exhibits PL emission peaks for the n=1 and n=2 phases. These results are consistent with STEM observations ( Figure 1 e and Figure 20 The results were completely consistent. However, in the control sample, the characteristic diffraction peaks of the n=2 phase dominated, while only trace diffraction was observed in the n=1 phase. Interestingly, the PL spectrum of the control sample showed significant emission peaks for the n=1, 2, 3, and 4 phases. This may be because the n=1, 3, and 4 phases in the control sample were nano-confined within the dominant n=2 phase. Figure 1 h and Figure 16 These phases are undetectable by XRD, but remain significant in PL emission. According to STEM observations ( Figure 13 The microstructure of the two-dimensional layers in the LSS sample is much more ordered, with most of the octahedral layers stacked perpendicular to the film plane. Therefore, the n=1 phase can still be observed in the XRD pattern of the LSS sample.

[0111] More importantly, such as Figure 3 As shown in the PL image of c, the two-dimensional perovskite (n=1 and n=2) capping layers are uniformly covered on the three-dimensional perovskite surface in the layered structure sample, indicating that the PCBM interlayer can induce uniform growth and distribution of the two-dimensional perovskite. Further monitoring of photoluminescence emission centered on the three-dimensional peak (approximately 780 nm) revealed uniform emission from the bottom three-dimensional perovskite layer over a large area of ​​15 μm × 15 μm, confirming the uniform two-dimensional passivation effect of the PCBM interlayer on the three-dimensional perovskite film.

[0112] Subsequently, the influence of the PCBM interlayer on the carrier dynamics of the perovskite heterostructure interface was investigated using steady-state and time-resolved photoluminescence spectroscopy. Figure 3 The detailed fitting parameters for the photoluminescence results are summarized in Table 1. Both the layered surface sample and the control sample were deposited on a glass substrate. When the laser was incident from the glass side (bottom direction), the photoluminescence emission of the control sample was stronger than that of the original three-dimensional perovskite film due to the suppression of nonradiative recombination associated with surface trap states, and the decay lifetime was longer. Figure 3 (d in the text). After introducing the PCBM intermediate layer, the photoluminescence emission intensity of the layered structure surface sample was significantly enhanced, and the average photoluminescence lifetime was extended from 427 ns in the control sample to 925 ns. Figure 3 (f in the figure), indicating that the unique layered structure can further enhance the photoelectric quality of the three-dimensional perovskite film. Interestingly, when the laser is incident from the perovskite side (top direction), the photoluminescence quenching of the layered surface film is more significant compared to the original three-dimensional sample and the control sample. Figure 3 (e, g in the text). This quenching originates from charge extraction at the 3D-2D interface, indicating that the intermediate layer of the PCBM facilitates more efficient charge separation. The average carrier lifetime of the layered surface film is almost one-third that of the control sample.

[0113] Table 1 Summary of TRPL spectral fitting parameters for different samples under different detection directions

[0114] Next, the stability of the layered surface samples and control samples was investigated at 75±10% RH. To quantify the film degradation, the normalized absorbance decay of the two-dimensional peak at approximately 560 nm corresponding to n=2 in the control samples and layered surface samples, as well as the bandgap evolution of the three-dimensional perovskite, were recorded during the aging test. Figure 25 ).like Figure 3As shown in h, after 55 days, the two-dimensional peak intensity and three-dimensional perovskite band gap of the control sample gradually decreased. In contrast, the layered surface sample maintained its structural integrity, with no degradation in either its two-dimensional or three-dimensional structure, exhibiting excellent chemical stability and enhanced resistance to moisture intrusion.

[0115] Experimental Example 3 In a nitrogen-filled glove box, using a xenon lamp-based solar simulator (Enlitech, IVS-KA5000), under standard AM1.5G (global solar spectrum, atmospheric mass 1.5) illumination conditions, the performance of solar cells was measured using a Keithley 2420 source meter. JV Characteristics and steady-state power output. Light intensity is calibrated using a silicon (Si) diode (Hamamatsu S1133) equipped with a Schottky visible color glass filter (KG5 color filter). Step voltage and scan speed are 20mV and 0.2V / s, respectively. JV Prior to measurement, the solar simulator was further calibrated using an Oriel reference solar cell certified by the National Institute of Standards and Technology (NIST) and conforming to ISO-17025 standards. The metal aperture used during the test had an area of ​​0.069 cm². 2 The external quantum efficiency was recorded in AC mode at a chopping frequency of 165 Hz using a solar cell quantum efficiency measurement system (QE-R3011, Enlitech). All stability tests were performed on an ITO / MeO-2PACz / perovskite / C solar cell structure. 60 / BCP / Ag pin-type perovskite solar cells. For light immersion stability testing, unencapsulated perovskite solar cells were periodically tested under continuous 1x sunlight exposure in a nitrogen atmosphere. For damp heat testing, all perovskite solar cells were encapsulated with UV-curable adhesive and cover glass, then the edges of the cover glass were further protected with epoxy resin and cured at room temperature for more than 48 hours. The encapsulated devices were placed in an environmental chamber at 85°C and 85%RH, and the photoelectric conversion efficiency was measured periodically after the devices cooled to room temperature. The efficiency was measured using a white LED lamp (100mW / cm²). 2 Maximum power point tracking and continuous light irradiation were performed to determine the long-term operational stability of the unpackaged device in a nitrogen atmosphere.

[0116] The influence of layered perovskite heterointerfaces on the photovoltaic performance of inverted perovskite solar cells was evaluated. The device structure was ITO / MeO-2PACz / perovskite / PCBM / BCP / Ag (ITO is indium tin oxide; MeO-2PACz is (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid; BCP is copper phosphate). Figure 4 (a) in the text, where the perovskite film has a composition of Cs 0.05 (MA0.05 FA 0.95 ) 0.95 Pb(I 0.95 Br 0.05 )3 (denoted as CsFAMA; MA stands for methylaminemonium; band gap 1.57 eV; Figure 25 The effects of PCBM and PEAI concentrations on photovoltaic performance were systematically studied, and it was found that the optimal concentrations for both PEAI and PCBM were 5 mg / mL. Figure 27 ).

[0117] First, the PEAI concentration was optimized for the ideal 3D-2D (control) PSC. As shown in the data ( Figure 24 (a) Increasing the PEAI concentration in the isopropanol antisolvent (C PEAI At a concentration of 1 mg / mL, PCE first increases and then decreases, at C PEAI The peak value is reached when C = 5 (see Table 3 for photovoltaic parameters). PEAI When the value increased from 0 to 5, all photovoltaic parameters improved: PCE increased from 19.46 to 24.07. V OC The voltage was increased from 1.100V to 1.178V. J SC From 23.40 mA / cm 2 Increased to 24.34 mA / cm 2 FF increased from 75.62% to 83.98%.

[0118] Subsequently, the PCBM concentration was optimized for high-efficiency LSS PSC. When the PCBM concentration in chlorobenzene ( C PCBM When the concentration (mg / mL) increased from 0 to 5, the PCE increased from 23.71% to 25.25% (as shown in the data set). Figure 27 (b) V OC The voltage was increased from 1.176V to 1.205V. J SC From 24.02 mA / cm 2 Increased to 24.80 mA / cm 2 FF increased from 82.79% to 84.48%. C PCBM With further increases, all photovoltaic parameters showed a continuous decreasing trend (Table 3). These results indicate that the optimal concentration of PCBM is 5 mg / mL.

[0119] Table 2. Photovoltaic parameters of 3D p-in structure devices under reverse scanning conditions at different PEAI concentrations.

[0120] Table 3. Photovoltaic parameters of LSS devices under reverse scanning conditions at different PCBM concentrations (PEAI concentration: 5 mg / mL)

[0121] like Figure 4 The current density of b in the equation is equal to the voltage ( ). JV As shown in the curves, the optimal control device achieved a photoelectric conversion efficiency of 24.42% under reverse scanning, higher than the original three-dimensional device (without two-dimensional surface treatment, 20.30%), thanks to the conventional passivation effect of the two-dimensional perovskite. The optimal device based on the layered surface structure further improved its efficiency to 25.97%, attributed to improvements in all photovoltaic parameters: open-circuit voltage (…). V OC The voltage was increased from 1.179V to 1.206V, and the short-circuit current density ( J SC From 24.57 mA / cm 2 Increased to 25.02 mA / cm 2 The fill factor increased from 84.31% to 86.08%. More importantly, the layered surface device exhibited negligible hysteresis (hysteresis index 0.81%) in both reverse and forward scans (Table 4), which was less than that of the original 3D device (6.75%) and the control device (3.40%). Figure 28 Different perovskite solar cells were provided JV Further lag analysis of the curve.

[0122] Table 4. Photovoltaic parameters of the optimal control device and the LSS device under forward and reverse scanning conditions.

[0123] To verify the effect of PCBM intermediate layers on pin structure devices JV The effect of hysteresis was investigated by testing a series of devices with different PCBM concentrations. Under forward scan (FS) and reverse scan (RS) conditions, corresponding data were obtained. JV curve( Figure 28(ag in the text). The PCE of different devices under RS ​​and FS are as follows: pure 3D structure devices are 18.63% and 16.73%, control samples are 23.72% and 21.90%, LSS structure devices (1 mg / mL) are 24.07% and 22.99%, LSS structure devices (3 mg / mL) are 24.17% and 23.52%, LSS structure devices (5 mg / mL) are 25.20% and 24.92%, LSS structure devices (8 mg / mL) are 23.84% and 23.14%, and LSS structure devices (10 mg / mL) are 22.59% and 21.40%. Detailed photovoltaic parameters are listed in... Figure 28 The lag effect is illustrated in the figure of ag. This lag effect can be quantitatively described by the lag index (HI), which is defined as shown in equation (1): (1) In the formula, PCE FS and PCE RS These figures represent the photoelectric conversion efficiencies of the pin PSC during forward and reverse scanning, respectively. Based on this, hysteresis index (HI) curves were plotted for different PCBM concentrations, and the results are summarized in [the table / document / reference needed]. Figure 28 h in. With the concentration of PCBM ( C PCBM As HI increases, it first increases and then decreases. C PCBM The peak value was reached at 5. At the optimal concentration, the hysteresis coefficient (HI) of the LSS-structured PSC was calculated to be 0.011, significantly lower than that of the pure 3D structure device (0.102) and the control sample (0.076), indicating that its hysteresis effect is negligible. Furthermore, as... Figure 29 Statistical results for 50 independent devices under each condition show that the devices based on the layered surface structure exhibit better reproducibility compared to the three-dimensional devices and the control devices. The average photoelectric conversion efficiency improved from 17.27% for the three-dimensional devices to 22.98% for the control devices, and then to 24.69% for the layered surface structure devices, which is attributed to a comprehensive improvement in all photovoltaic parameters.

[0124] The band gap of the layered surface device was determined by differential external quantum efficiency (EQE) spectroscopy, which showed an inflection point at 792 nm, corresponding to 1.57 eV (Almora, O., Cabrera, CI, Garcia‐Cerrillo, J., Kirchartz, T., Rau, U.&Brabec, CJJA em Quantifying the absorption onset in the quantum efficiency of emerging photovoltaic devices). Advanced Energy Materials 11, 2100022 (2021); Figure 30 Therefore, the open-circuit voltage drop of the layered surface device is calculated. E g - qV OC The voltage loss was 0.364V (q is the elementary charge) (Jeong, M., Choi, IW, Go, EM, Cho, Y., Kim,M., Lee, B., Jeong, S., Jo, Y., Choi, HW&Lee, JJS Stable perovskitesolar cells with efficiency exceeding 24.8% and 0.3-V voltage loss). Science 369, 1615-1620 (2020). This is the most reported to date. E g One of the lowest open-circuit voltage losses in perovskite solar cells, at approximately 1.57 eV. Figure 31 Furthermore, the short-circuit current density obtained by integrating the external quantum efficiency is... JV The values ​​extracted from the curve are highly consistent. Figure 30 The improvement in external quantum efficiency in the long wavelength range of 650-780 nm is mainly attributed to the optimization of the interfacial energy level arrangement between the perovskite thin film and the PCBM electron transport layer.

[0125] To evaluate the interfacial energy level arrangement, ultraviolet photoelectron spectroscopy was performed on different perovskite thin films. Figure 32 Fermi level (E) F According to formula E F = E cut-off -21.22 eV was calculated, where E cut-offThe cutoff binding energy is 21.22 eV, and the photon energy of the excitation light is 21.22 eV. Pure 3D thin films, control films, and LSS films... E cut-off The extracted values ​​were 16.55 eV, 16.83 eV, and 17.22 eV, respectively. Based on these values, E was calculated. F The values ​​were -4.67 eV, -4.39 eV, and -4.00 eV, respectively. Subsequently, the price band peaked ( E VBM ) through formula E VBM =E F - E onset (in E onset Calculations were performed using the inception potential in the valence band spectrum for the pure 3D thin film, the control film, and the LSS film. E VBM The band gaps are -5.42 eV, -5.17 eV, and -5.25 eV, respectively. (The band gaps of the three perovskite films are...) E g The value was obtained through absorption and EQE spectroscopy, and the calculated result was 1.57 eV. Therefore, the conduction band bottom ( E CBM The calculations are as follows: the conduction band bottom of the pure 3D film, the control film, and the LSS film ( E CBM The values ​​are -3.86 eV, -3.61 eV, and -3.69 eV, respectively. Similarly, the values ​​of PCBM ETL are... E CBM and E VBM The calculated results are -3.72 eV and -6.02 eV, respectively.

[0126] Figure 4 Figure c shows the energy level diagram of MeO-2PACz, perovskite, and PCBM anchored on an ITO substrate. It was observed that PEAI post-processing leads to a secondary electron cutoff energy ( ) regardless of the use of the PCBM intermediate layer. E cut-off The shift towards higher binding energies indicates that the ion exchange-induced three-dimensional to two-dimensional perovskite phase transition can reduce the Fermi level of perovskite films. E FNotably, the energy difference between the Fermi level and the valence band top of the layered surface film is greater than that of the control sample, indicating enhanced n-type characteristics of the three-dimensional perovskite film. Furthermore, at the n-type contact, the conduction band bottom of the layered surface film is closer to that of the PCBM, resulting in more efficient interfacial charge transfer between the perovskite and PCBM electron transport layers. In contrast, the conduction band bottom of the control sample is much higher than that of the PCBM electron transport layer, and its n-type characteristics are weaker, leading to lower charge transfer efficiency at the electron-selective contact. This energy level arrangement of the perovskite solar cell based on the layered surface structure is beneficial for improving the built-in electric field of the device and reducing charge accumulation at the electron-selective contact interface, thereby contributing to achieving high open-circuit voltage and fill factor, which is supported by Mott-Schottky analysis. Figure 33 ).

[0127] Subsequently, a series of durability tests were conducted on different perovskite solar cell devices under various external stress conditions. First, the evolution of photoelectric conversion efficiency was monitored under continuous irradiation with 1x sunlight in a nitrogen atmosphere. Figure 34 The layered surface device exhibits superior photostability compared to the control device, retaining 90% (T) even after 1000 hours of irradiation. 90 The initial photoelectric conversion efficiency of the control device was significantly improved, while the control device retained only 22% of its initial photoelectric conversion efficiency after 768 hours. This significant improvement is attributed to the blocking effect of the PCBM intermediate layer on ion exchange between the three-dimensional and two-dimensional perovskites, a conclusion confirmed by electronic analysis. Figure 35 Further analysis was conducted on the photovoltaic parameters of the control sample and the LSS PSC under nitrogen (N2) atmosphere and continuous sunlight irradiation. V OC , J SC The evolution of (and FF) Figure 34 Observations revealed that, with prolonged aging time, the control device's... V OC It first gradually increases, reaches its peak at 168 hours, and then gradually decreases. J SC Both FF and FF showed a gradual decreasing trend over time. In contrast, after 1000 hours of light immersion, the LSS device, except for V OC Apart from a slight decrease, its initial FF and J SC All were preserved, indicating that the pin PSC has excellent photostability after the PCBM layer is inserted. V OC The initial increase is more likely attributed to the microstructural evolution of the three-dimensional perovskite. For example... Figure 37 , Figure 38As shown, the three-dimensional perovskite structure undergoes significant changes during aging, with an excess of PbI2 secondary phase forming along the grain boundaries due to ion migration. This is consistent with previous studies (Zhao, Y., Ma, F., Qu, Z., Yu, S., Shen, T., Deng, H.-X., Chu, X., Peng, X., Yuan, Y.&Zhang, XJS). Inactive (PbI2)2RbCl stabilizes perovskite films for efficient solar cells. Science 377, 531-534 (2022).;Wang, H., Wang, Z., Yang, Z., Xu, Y., Ding,Y., Tan, L., Yi, C., Zhang, Z., Meng, K.&Chen, GJAM Ligand‐modulatedexcess PbI2nanosheets for highly efficient and stable perovskite solar cells. Advanced Materials 32, 2000865 (2020).), the formed PbI2 may produce a passivation effect, reducing carrier recombination, and thus leading to V OC Increase. However, long-term aging can cause the three-dimensional perovskite structure to collapse, making... V OC And PCE gradually declines, eventually leading to V OC The inflection point appears. (Comparison device) J SC The FF gradually decreases with aging time, due to the deterioration of thin film quality. Furthermore, the evolution of the FF of the control device is related to parasitic resistive losses (shunt resistance losses and series resistance losses). Generally, achieving high FF requires low recombination losses (high...). V OC A smooth, uniform, and dense active layer (high shunt resistance Rsh) and efficient charge extraction and transport (low series resistance) R s ).like Figure 35 As shown, Rsh gradually decreases with increasing aging time. R s The gradual increase indicates that the decrease in FF of the control device is related to resistive loss. After inserting the PCBM layer, Rsh and [other parameters] gradually increase during photoaging. R sThere were no significant changes, which means that all photovoltaic parameters of the LSS PSC were retained.

[0128] According to the ISOS-L-1I protocol of the International Organic Photovoltaic Stability Summit (ISOS), under continuous illumination (100mW / cm²), -2 Maximum power point (MPP) tracking tests were conducted. Typically, after 1100 hours, the layered surface device still maintains 95% (T0) of its performance. 95 The initial photoelectric conversion efficiency () Figure 4 (d) , while the control device's photoelectric conversion efficiency dropped to 40% of its initial value after only 450 hours. Furthermore, in accordance with the ISOS-D-3 protocol, the packaged devices were placed in a climate chamber for damp heat testing (85°C, 85% RH). Figure 4 As shown in e, under humid heat aging conditions, the layered surface device still maintained 90.7% of the initial photoelectric conversion efficiency (23.02±0.53%) after 1000 hours; Figure 36 In contrast, the control device retained only 24.6% of its initial photoelectric conversion efficiency (21.08 ± 1.19%) after 500 hours. The good preservation of the heterostructure microstructure after aging contributes to the excellent wet-heat durability of the layered surface film, while for the control film without a PCBM interlayer, neither the two-dimensional nor three-dimensional components can maintain structural integrity, especially in the grain boundary region. Figure 4 f and g in the text.

[0129] To gain a deeper understanding of the mechanism, the degradation behavior of layered surface devices and control devices was compared under maximum power point (MPP) operating conditions and environmental conditions. For example... Figure 37 As shown, both the new control device and the layered surface device exhibit three-dimensional and two-dimensional perovskite layers. After 15 days of MPP operation, the control device showed significant microstructural degradation and PbI2 formation, especially at the grain boundaries. Figure 38 (a and b in the text). Conversely, the layered surface devices showed only minor damage, mainly located at the burial interface, while the layered surface structure remained largely intact. Figure 38 (c and d in the original text). Therefore, it is inferred that the degradation of the control device under MPP conditions is mainly attributed to ion migration (which is known to tend to occur along grain boundaries), which triggers the observed microstructure changes and phase degradation. In layered surface devices, the unique combination of a uniform two-dimensional layer, a PCBM intermediate layer, and a two-dimensional molecular layer effectively blocks ion migration.

[0130] The degradation behavior of the control sample and the layered surface sample also differed significantly under environmental conditions. After being stored in an atmosphere with 50-60% relative humidity (RH) for 10 days, the surface morphology of the control sample changed drastically, with numerous pinholes appearing. Figure 39 (a, b) In contrast, the surface changes of the layered structure surface sample are extremely small ( Figure 39 c and d in the text). Scanning transmission electron microscopy revealed that a large amount of PbI2 (c, d) was formed in the three-dimensional grains of the control sample. Figure 40 (a and b in the text). Meanwhile, the layered surface sample showed almost no change, and almost no PbI2 was generated ( Figure 40 (c and d in the text). The improved stability under working and environmental conditions is mainly attributed to the ion blocking and moisture blocking effects of the PCBM intermediate layer and passivator in the layered structure surface. In particular, the good preservation of the microstructure and phases of the layered structure surface in the perovskite solar cell device enhances the interfacial reliability and chemical stability of the three-dimensional perovskite.

[0131] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A perovskite heterojunction, characterized in that: It includes a three-dimensional perovskite layer, a two-dimensional perovskite layer covering at least a portion of the three-dimensional perovskite layer, a reactive inert spacer layer and a two-dimensional molecular passivation layer interposed between the three-dimensional perovskite layer and the two-dimensional perovskite layer.

2. The perovskite heterojunction of claim 1, wherein: The perovskite heterostructure comprises a three-dimensional perovskite layer, a two-dimensional molecular passivation layer, a reactive inert spacer layer, and a two-dimensional perovskite layer stacked sequentially.

3. The perovskite heterojunction according to claim 1, characterized in that: The two-dimensional perovskite layer comprises one or more perovskite layers, each perovskite layer having a width n of 1 and / or 2.

4. The perovskite heterojunction according to claim 1, characterized in that: The average thickness of the three-dimensional perovskite layer is 5-1000 nm; and / or, the average thickness of the two-dimensional perovskite layer is 1-30 nm; and / or, the average thickness of the reactive inert spacer layer is 1-150 nm; and / or, the average thickness of the two-dimensional molecular passivation layer is 0.5-2.0 nm.

5. The perovskite heterojunction of claim 1, wherein: The three-dimensional perovskite layer or two-dimensional perovskite layer comprises an ABX3-type perovskite, wherein the A site is one or more of Cs + , MA + , FA + ; the B site is Pb 2+ , Sn 2+ , Cu 2+ ; and the X site is one or more of F - , Cl - , Br - , I - .

6. The perovskite heterojunction of claim 1, wherein: The reactive inert spacer layer comprises at least one of a fullerene or its derivative, a non-fullerene acceptor material, or a non-conjugated polymer; and / or the two-dimensional molecular passivation layer comprises at least one organic ligand of phenethylammonium, 4-fluorophenethylammonium, 3-fluorophenethylammonium, 2-fluorophenethylammonium, butylammonium, hexylammonium, octylammonium, or 1-naphthylmethylammonium.

7. A method of preparing the perovskite heterojunction of any one of claims 1-6, characterized in that: Includes the following steps: A reactive inert spacer material solution is coated onto the surface of a three-dimensional perovskite layer, followed by a two-dimensional molecular passivation material solution, and then annealed to obtain the perovskite heterojunction.

8. A perovskite cell characterized by: Includes the perovskite heterojunction as described in any one of claims 1-6.

9. The perovskite cell according to claim 8, characterized in that: The perovskite solar cell includes a conductive substrate, a first transport layer, a perovskite heterojunction, a second transport layer, and a metal electrode stacked sequentially; one of the first transport layer and the other of the second transport layer is a hole transport layer and the other is an electron transport layer.

10. An electrical device, characterized by: Includes the perovskite heterojunction as described in any one of claims 1-6 or the perovskite solar cell as described in claim 8 or 9.

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