Perovskite layer and its preparation method, solar cell, photovoltaic module

Abstract

This application relates to the field of solar cell technology, and more particularly to a perovskite layer and its preparation method, a solar cell, and a photovoltaic module. The perovskite layer comprises a 2D perovskite sublayer and a 3D perovskite sublayer stacked together. The 3D perovskite sublayer comprises a 3D perovskite material with the chemical formula ABX3 and chloride ions, while the 2D perovskite sublayer contains phenylethylammonium ions. A is an A-site cation, B is a B-site cation, and X is an X-site anion. The A-site cation includes an organic cation, specifically a FA ion; the B-site cation includes a divalent metal ion; and the X-site anion includes a halide ion. This application improves the stability and performance of the FA-based perovskite layer by adding phenylethylammonium ions, thereby enabling solar cells to achieve improved performance and stability using the FA-based perovskite layer.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a perovskite layer and its preparation method, solar cells, and photovoltaic modules. Background Technology

[0002] Although the perovskite layer of the FA (formamidinium) system has excellent performance, the perovskite layer of the FA system is prone to phase transition. These phenomena seriously affect the stability of solar cells, making it difficult to improve the performance of solar cells by utilizing the perovskite layer of the FA system. Summary of the Invention

[0003] This application discloses a perovskite layer and its preparation method, a solar cell, and a photovoltaic module, which can reduce the probability of phase transition in FA system 3D perovskite materials, thereby improving the stability of FA system perovskite.

[0004] To achieve the above objectives, in a first aspect, embodiments of this application disclose a perovskite layer, comprising a 2D perovskite sublayer and a 3D perovskite sublayer stacked together. The 3D perovskite sublayer comprises 3D perovskite material with the chemical formula ABX3 and chloride ions, and the 2D perovskite sublayer contains phenylethylammonium ions; Wherein, A is an A-position cation, B is a B-position cation, X is an X-position anion, the A-position cation includes an organic cation, and the organic cation is a FA ion, the B-position cation includes a divalent metal ion, and the X-position anion includes a halide ion.

[0005] In a possible implementation of the first aspect, the perovskite layer further includes a quasi-2D perovskite sublayer disposed between the 2D perovskite sublayer and the 3D perovskite sublayer; The general chemical formula of the 2D perovskite sublayer is (PEA). m1 (FA) n1 PbI x1 Br y1 Wherein, PEA is phenylethylammonium ion, m1, n1, x1 and y1 are all positive numbers, and satisfy the following relationship: m1+n1=2, and x1+y1=4; The chemical formula of the quasi-2D perovskite sublayer is (PEA). m2 (FA) n2 Rb k PbI x2 Br y2 Wherein, PEA is phenylethylammonium ion, m2, n2, k, x2 and y2 are all positive numbers, and satisfy the following relationship: m2+n2+k=2, x2+y2=4.

[0006] In a possible implementation of the first aspect, the perovskite layer further includes a modified interface sublayer and a transition sublayer, wherein the 2D perovskite sublayer, the quasi-2D perovskite sublayer, the modified interface sublayer, the transition sublayer, and the 3D perovskite sublayer are stacked sequentially. The modified interface sublayer includes PbS and RbBr; The chemical formula of the transition sublayer is PbI. x3 Br y3 Where x3 and y3 are both positive numbers and satisfy the following relationship: x3 + y3 = 2.

[0007] In a possible implementation of the first aspect, the A-site cation further includes at least one of Cs ions and Rb ions; and / or, The divalent metal ions include Pb ions; and / or, The halide ion includes at least one of I- ions or Br- ions; and / or The 3D perovskite sublayer also includes bis(trifluoromethyl)bromobenzene.

[0008] Secondly, embodiments of this application disclose a method for preparing a perovskite layer, comprising the following steps: Preparation of the framework layer: The framework layer is prepared on a substrate; wherein the framework layer comprises a divalent metal halide with the chemical formula BX2; wherein B is a B-position cation, X is an X-position anion, the B-position cation comprises a divalent metal ion, and the X-position anion comprises a halide ion; Coating with a first organic cation solution: The first organic cation solution is coated on the framework layer to form a first wet film; wherein, the first organic cation solution includes a first organic halide with the chemical formula AX and phenylethylammonium hydrochloride; A is an A-site cation, X is an X-site anion, the A-site cation includes an organic cation, and the organic cation is FA ion; First annealing: The substrate on which the first wet film is formed is subjected to a first annealing to form a 2D perovskite sublayer; Coating with a second organic cation solution: The second organic cation solution is coated onto the skeleton layer after the first annealing to form a second wet film; wherein, the second organic cation solution includes a second organic halide with the chemical formula AX; Second annealing: The substrate on which the second wet film is formed is subjected to a second annealing to form a 3D perovskite sublayer, thereby obtaining the perovskite layer.

[0009] In a possible implementation of the second aspect, the second organic cation solution further includes at least one of PbS quantum dots, RbBr, or bis(trifluoromethyl)bromobenzene.

[0010] In a possible implementation of the second aspect, when the second organic cation solution further includes PbS quantum dots, the concentration of the PbS quantum dots is 0.01 mg / mL to 10 mg / mL; When the second organic cation solution also includes RbBr, the concentration of RbBr is 0.01 mg / mL to 10 mg / mL; When the second organic cation solution also includes bis(trifluoromethyl)bromobenzene, the concentration of bis(trifluoromethyl)bromobenzene is 0.01 mg / mL to 10 mg / mL; In a possible implementation of the second aspect, the solvent for the second organic cation solution is ethanol; Alternatively, the solvent of the second organic cation solution includes ethanol and DMSO, and the volume percentage of ethanol is greater than or equal to 60%.

[0011] In a possible implementation of the second aspect, the step of preparing the skeleton layer includes: The framework layer was obtained by co-evaporating CsBr and PbI2 on the substrate through multi-source evaporation. And / or, the first organohalide includes a FAI, and the concentration of the FAI is 0.9 mg / mL to 1.1 mg / mL; And / or, the first annealing step includes: The substrate on which the first wet film is formed is annealed at 120°C to 160°C for 8 min to 12 min to form the 2D perovskite sublayer on the surface of the framework layer. And / or, the second organohalide includes at least one of FAI or FABr; And / or, the second annealing step includes: The substrate on which the second wet film is formed is annealed at 120°C to 160°C for 25 min to 35 min to obtain the 3D perovskite sublayer.

[0012] Thirdly, this application discloses a solar cell, including a substrate, and a first carrier transport layer, a perovskite layer and a second carrier transport layer sequentially stacked on the substrate in a direction away from the substrate. One of the two carrier transport layers is an electron transport layer and the other is a hole transport layer. Wherein, the perovskite layer is the perovskite layer described in the first aspect; Alternatively, the perovskite layer is prepared by the preparation method described in the second aspect; The 3D perovskite sublayer and the 2D perovskite sublayer are sequentially stacked on the first carrier transport layer in a direction away from the substrate.

[0013] In a possible implementation of the third aspect, when the perovskite layer further includes a quasi-2D perovskite sublayer, a modified interface sublayer, and a transition sublayer, the 2D perovskite sublayer, the quasi-2D perovskite sublayer, the modified interface sublayer, the transition sublayer, and the 3D perovskite sublayer are stacked sequentially in a direction away from the substrate.

[0014] In a possible implementation of the third aspect, the substrate is a bottom battery.

[0015] Fourthly, embodiments of this application disclose a photovoltaic module, including a plurality of electrically connected solar cells, at least one of which is the solar cell described in the third aspect.

[0016] Compared with the prior art, the beneficial effects of this application are: This application utilizes phenylethylammonium ions inserted into the perovskite interlayer to significantly increase the phase transition activation energy of 3D perovskite materials, reduce the probability of phase transition in FA system 3D perovskite materials, and thus improve the stability of FA system perovskite. Chloride ions can also reduce the metal halide residue at the bottom of the perovskite layer, thereby enabling solar cells to achieve improved performance and stability using FA system perovskite layers.

[0017] In this application, the organic cation at the A-site of the 3D perovskite material is the FA ion. That is, this 3D perovskite material is an FA-based 3D perovskite material. FA-based 3D perovskite materials have advantages such as longer carrier diffusion length, lower defect state density, and smaller voltage drop, enabling solar cells with FA-based perovskite layers to achieve improved electrical performance. Furthermore, FA-based 3D perovskite materials are also heat-resistant, which helps reduce component loss during high-temperature aging and avoids lattice collapse during high-temperature processes such as sintering, thereby reducing fill factor loss in solar cells after sintering.

[0018] To mitigate the irreversible phase transition of FA-based 3D perovskite materials, this application forms a 3D perovskite sublayer based on a 2D perovskite sublayer containing phenylethylammonium ions. The aromatic ring (benzene ring) in the phenylethylammonium ions can insert into the perovskite interlayer and form coordination bonds with divalent metal ions in the 3D perovskite material. This coordination effect restricts the displacement of divalent metal ions, thereby significantly increasing the phase transition activation energy of the 3D perovskite material, reducing the probability of phase transition, and keeping the 3D perovskite material in the photoactive α phase. This, in turn, helps reduce anomalies such as cracking and interface peeling caused by the phase transition of the 3D perovskite material. Furthermore, the aromatic ring in the phenylethylammonium ions is also hydrophobic, which helps reduce the erosion of the perovskite layer by water vapor.

[0019] Furthermore, during the fabrication of 3D perovskite sublayers, chloride ions can promote the penetration of FA ions and accelerate the reaction between FA ions and the framework layer. This solves the problem of metal halides easily remaining at the bottom of the FA system perovskite layer, which helps to reduce the carrier recombination centers in the perovskite layer and thus improves the conversion efficiency of solar cells.

[0020] In summary, this application utilizes phenylethylammonium ions inserted into the perovskite interlayer to improve the stability and performance of the FA system perovskite layer, thereby enabling solar cells to achieve improved performance and stability using the FA system perovskite layer. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a solar cell disclosed in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures: 10. Solar cell; 11. Substrate; 12. First carrier transport layer; 13. Perovskite layer; 131. 2D perovskite sublayer; 132. 3D perovskite sublayer; 133. Quasi-2D perovskite sublayer; 134. Modified interface sublayer; 135. Transition sublayer; 14. Second carrier transport layer; 15. Transparent conductive layer; 16. Transparent electrode layer; 17. Metal electrode. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In this application, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (the specific types and structures may be the same or different), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0026] By adjusting the ratio of MA and FA in the 3D perovskite material hybrid system, the band gap of the perovskite layer can be precisely controlled to the ideal range, so as to achieve better spectral and current matching between the perovskite layer and the substrate.

[0027] However, the mixed MA and FA system of 3D perovskite materials suffers from poor thermal stability, and its performance tends to deteriorate after electrode fabrication. This is because MA ions, i.e., ammonium carbamate ions, decompose at temperatures above 150°C, with the reaction: CH3NH3 + →CH3NH2(g)↑+ H + This leads to the lattice collapse of 3D perovskite materials, and at the same time, MA at high temperatures + Rapid migration along grain boundaries or defects leads to component segregation. The slurry used in perovskite solar cell electrode fabrication needs to be above 180°C to achieve complete solidification. Forcibly lowering the sintering temperature of the slurry will result in a large amount of organic matter remaining on the perovskite solar cell, leading to an increase in series resistance and a decrease in fill factor.

[0028] Compared to hybrid MA and FA 3D perovskite materials, FA-based 3D perovskite materials exhibit significant advantages in kinetics, with a longer carrier diffusion length (>5 μm), while the carrier diffusion length of hybrid MA and FA 3D perovskite materials is only 1 μm to 3 μm. Furthermore, FA-based 3D perovskite materials have a lower defect state density and lower voltage drop (VL). OC Theoretical limit > 1.3 V). FA-based 3D perovskite materials also possess low exciton binding energies (≈5 meV, hybrid systems ≈15 meV), approaching the characteristics of a perfect semiconductor. Furthermore, FA-based 3D perovskite materials exhibit excellent intrinsic thermal stability: the decomposition temperature of FA ions is >200°C, and the component loss rate under high-temperature aging can be reduced by more than 50%, thus avoiding lattice collapse problems caused by extreme high-temperature environments and helping to reduce the fill factor loss of solar cells after electrode sintering.

[0029] However, FA system 3D perovskite materials have an irreversible phase transition at room temperature. The transition barrier from the photoactive black α phase to the inactive yellow δ phase is extremely low (<0.1 eV), and can be triggered at room temperature and humidity >30%. The phase transition is accompanied by a volume expansion of >20%, which causes cracking of the perovskite layer and interface peeling, placing high demands on the encapsulation and manufacturing environment.

[0030] Due to the low activation energy, the FA system perovskite material crystallizes too quickly during formation, easily forming a porous structure with a pinhole density several times higher than that of the MA and FA mixed system perovskite material. This leads to leakage current in the perovskite layer and additional ion migration pathways. Especially when the substrate surface has a pyramidal textured surface, the excessively rapid reaction rate can prevent the organic cation solution from reaching the bottom of the pyramid, resulting in a large amount of metal halide residue and introducing more charge carrier recombination centers, thus reducing the conversion efficiency of the solar cell.

[0031] The above reasons make it difficult to improve the performance of solar cells using FA-based 3D perovskite materials.

[0032] Based on the above analysis, this application provides a perovskite layer by adding phenylethylammonium ions to improve the stability and performance of the FA system perovskite layer, thereby enabling solar cells to achieve improved performance and stability by utilizing the FA system perovskite layer.

[0033] The technical solution of the present invention will now be described in conjunction with the embodiments and accompanying drawings.

[0034] Reference Figure 1 This application discloses a perovskite layer 13, including a 2D perovskite sublayer 131 and a 3D perovskite sublayer 132 stacked together.

[0035] The 3D perovskite sublayer 132 includes a 3D perovskite material with the chemical formula ABX3 and chloride ions, while the 2D perovskite sublayer 131 contains phenylethylammonium ions.

[0036] Wherein, A is an A-position cation, B is a B-position cation, and X is an X-position anion. The A-position cation includes organic cations, and the organic cation is FA ion. The B-position cation includes divalent metal ions, and the X-position anion includes halide ions.

[0037] This application utilizes phenylethylammonium ions inserted into the perovskite interlayer to significantly increase the phase transition activation energy of 3D perovskite materials, reduce the probability of phase transition in FA system 3D perovskite materials, and thus improve the stability of FA system perovskite. Chloride ions can also reduce the metal halide residue at the bottom of the perovskite layer, thereby enabling solar cells to achieve improved performance and stability using FA system perovskite layers.

[0038] In this application, the organic cation at the A-site of the 3D perovskite material is the FA ion, and the only organic cation is the FA ion. In other words, this 3D perovskite material is an FA-based 3D perovskite material. FA-based 3D perovskite materials have advantages such as longer carrier diffusion length, lower defect state density, and smaller voltage drop, enabling solar cells with FA-based perovskite layers to achieve improved electrical performance. Furthermore, FA-based 3D perovskite materials are also heat-resistant, which helps reduce the component loss rate under high-temperature aging and avoids lattice collapse during high-temperature processes such as sintering, thereby reducing the fill factor loss of solar cells after sintering.

[0039] To mitigate the irreversible phase transition of FA-based 3D perovskite materials, this application forms a 3D perovskite sublayer based on a 2D perovskite sublayer containing phenylethylammonium ions. The aromatic ring (benzene ring) in the phenylethylammonium ions can insert into the perovskite interlayer and form coordination bonds with divalent metal ions in the 3D perovskite material. This coordination effect restricts the displacement of divalent metal ions, thereby significantly increasing the phase transition activation energy of the 3D perovskite material, reducing the probability of phase transition, and keeping the 3D perovskite material in the photoactive α phase. This, in turn, helps reduce anomalies such as cracking and interface peeling caused by the phase transition of the 3D perovskite material. Furthermore, the aromatic ring in the phenylethylammonium ions is also hydrophobic, which helps reduce the erosion of the perovskite layer by water vapor.

[0040] Furthermore, during the fabrication of 3D perovskite sublayers, chloride ions can promote the penetration of FA ions and accelerate the reaction between FA ions and the framework layer. This solves the problem of metal halides easily remaining at the bottom of the FA system perovskite layer, which helps to reduce the carrier recombination centers in the perovskite layer and thus improves the conversion efficiency of solar cells.

[0041] In summary, this application utilizes phenylethylammonium ions inserted into the perovskite interlayer to improve the stability and performance of the FA system perovskite layer, thereby enabling solar cells to achieve improved performance and stability using the FA system perovskite layer.

[0042] In some embodiments, the perovskite layer 13 further includes a quasi-2D perovskite sublayer 133, which is disposed between the 2D perovskite sublayer 131 and the 3D perovskite sublayer 132.

[0043] Optionally, the general chemical formula of the 2D perovskite sublayer 131 is (PEA). m1 (FA) n1 PbI x1 Br y1Wherein, PEA is phenylethylammonium ion, FA is formamidinium ion, Pb is lead ion, I is iodide ion, and Br is bromide ion. m1, n1, x1, and y1 are all positive numbers and satisfy the following relationships: m1 + n1 = 2, and x1 + y1 = 4.

[0044] Optionally, the chemical formula of quasi-2D perovskite sublayer 133 is (PEA). m2 (FA) n2 Rb k PbI x2 Br y2 Wherein, PEA is phenylethylammonium ion, Rb is rubidium ion, FA is formamidinium ion, Pb is lead ion, I is iodide ion, and Br is bromide ion. m2, n2, k, x2, and y2 are all positive numbers and satisfy the following relationships: m2 + n2 + k = 2, x2 + y2 = 4. It should be noted that m1, n1, x1, y1, m2, n2, k, x2, and y2 can be positive integers or decimals.

[0045] In this way, the band gaps of the 2D perovskite sublayer 131, the quasi-2D perovskite sublayer 133, and the 3D perovskite sublayer 132 decrease, thereby forming a stepped band structure. This significantly reduces deep-level traps, avoids dislocation defects caused by interface lattice mismatch, and reduces the probability of nonradiative recombination.

[0046] Furthermore, the perovskite layer 13 also includes a quasi-2D perovskite sublayer 133, a modified interface sublayer 134, and a transition sublayer 135, with the 2D perovskite sublayer 131, the quasi-2D perovskite sublayer 133, the modified interface sublayer 134, the transition sublayer 135, and the 3D perovskite sublayer 132 stacked sequentially.

[0047] Optionally, the modified interface sublayer 134 includes PbS and RbBr. PbS is lead sulfide, and RbBr is rubidium bromide. PbS in the modified interface sublayer 134 serves as a heterogeneous nucleation site, lowering the nucleation energy barrier of the 3D perovskite phase. Its surface thiol ligands can undergo coordination exchange with the perovskite lattice, promoting interface fusion. Rb... + Embedded in 2D perovskite sublayers, partially replacing phenylethylammonium ions, quasi-2D perovskites are formed to reduce interlayer spacing. Br - During the fabrication process, a PbI framework layer is incorporated. Since the Pb-I bond length is 2.98 Å and the Pb-Br bond length is 2.96 Å, the Pb-I bond length is greater than the Pb-Br bond length, which induces lattice contraction and provides a lattice-matched transition for the 3D perovskite phase.

[0048] Optionally, the chemical formula of transition sublayer 135 is PbI. x3 Br y3Where Pb is lead ion, I is iodide ion, Br is bromide ion, and x3 and y3 are both positive numbers, satisfying the following relationship: x3 + y3 = 2. - The infiltration of the PbI framework layer during fabrication induces lattice contraction, providing a lattice-matched transition for the 3D perovskite phase. This application also allows for the adjustment of the perovskite composition and band structure by controlling the bromine content of the transition sublayer 135.

[0049] Furthermore, the 2D perovskite sublayer 131, the quasi-2D perovskite sublayer 133, the modified interface sublayer 134, the transition sublayer 135, and the 3D perovskite sublayer 132 form a stepped band structure to further reduce deep-level traps, avoid dislocation defects caused by interface lattice mismatch, and reduce the probability of nonradiative recombination.

[0050] Optionally, the 3D perovskite sublayer also includes bis(trifluoromethyl)bromobenzene, whose molecules possess significant steric hindrance and strong hydrophobicity. The trifluoromethyl group tends to occupy the grain boundaries or surface of the 3D perovskite material, forming a physical water barrier to mitigate the impact of moisture on the material. Furthermore, the macromolecular structure of bis(trifluoromethyl)bromobenzene hinders the migration of FA ions, divalent metal ions, and halide ions, reducing lattice distortion and phase separation caused by ion migration, thereby suppressing the formation of the δ phase (yellow phase). Moreover, bromide ions can improve the crystallization process of the 3D perovskite material, facilitating the formation of a perovskite layer with larger grains and lower defect state density.

[0051] Optionally, in the chemical formula ABX3, the A-site cation also includes at least one of Cs ions and Rb ions.

[0052] Among them, the ionic radii of Cs ions and Rb ions are smaller than those of FA ions. When Cs ions and Rb ions are incorporated into the A-site of 3D perovskite materials, the perovskite cell parameters can be slightly contracted, which effectively offsets the lattice expansion caused by large-sized FA cations, so that the α-phase 3D perovskite materials remain stable over a wider temperature range, thereby suppressing the phase transformation of 3D perovskite materials.

[0053] Optionally, the divalent metal ion includes Pb (lead) ions. Furthermore, the halide ion includes at least one of I (iodide) ions or Br (bromine) ions.

[0054] The stability of FA-based 3D perovskite materials depends on the matching of the ionic radii of FA ions, B-site cations, and halide ions. The perfect matching of the ionic radii of Pb, I, and Br ions is beneficial for forming stable perovskite crystals and reduces the probability of phase transitions in 3D perovskite materials.

[0055] This application discloses a method for preparing a perovskite layer, including the following steps: Preparation of the framework layer: A framework layer is prepared on the substrate; wherein the framework layer comprises a divalent metal halide with the chemical formula BX2. B is a B-site cation, X is an X-site anion, the B-site cation includes a divalent metal ion, and the X-site anion includes a halide ion; Coating with a first organic cation solution: A first organic cation solution is coated onto the framework layer to form a first wet film; wherein, the first organic cation solution includes a first organic halide with the chemical formula AX and phenylethylammonium hydrochloride. A is an A-position cation, X is an X-position anion, the A-position cation includes an organic cation, and the organic cation is a FA ion; First annealing: The substrate with the first wet film is subjected to the first annealing to form a 2D perovskite sublayer; Coating with a second organic cation solution: A second organic cation solution is coated onto the skeleton layer after the first annealing to form a second wet film; wherein, the second organic cation solution includes a second organic halide with the chemical formula AX; Second annealing: The substrate with the second wet film is subjected to a second annealing to form a 3D perovskite sublayer, thus obtaining the perovskite layer.

[0056] The preparation method of this application utilizes a two-step method to prepare the FA system perovskite layer. By adding phenylethylammonium hydrochloride, the reaction of the framework layer is promoted to be complete, and the stability and performance of the FA system perovskite layer can also be improved.

[0057] In this process, the organic cation solution is coated twice. During the first coating of the organic cation solution, phenylethylammonium hydrochloride is incorporated. The chloride ions of phenylethylammonium hydrochloride can diffuse into the framework layer and replace the larger halide ions within the framework layer. The chloride ions occupy a small lattice volume, forming tiny vacancies. These tiny vacancies are interconnected, creating nanoscale pores in the framework layer. Furthermore, the aromatic ring in the phenylethylammonium ion is hydrophobic, which helps improve the humidity stability of subsequent processes.

[0058] In this way, when coating the second organic cation solution, the solution can penetrate to the bottom of the framework layer through these nanoscale pores. These nanoscale pores can increase the diffusion coefficient of FA ions during the reaction, making it easier for FA ions to penetrate to the bottom of the framework layer and react fully. This solves the problem of metal halide residues at the bottom of the FA system perovskite layer, which helps reduce carrier recombination centers in the perovskite layer and thus improves the conversion efficiency of solar cells. Especially when the substrate surface has a pyramid light-trapping structure, phenylethylammonium hydrochloride can also allow the second organic halide to penetrate to the bottom of the pyramid light-trapping structure, thereby reducing the amount of framework layer material residue at the bottom. Furthermore, due to the high volatility of chloride ions, they tend to escape in gaseous form during the annealing process, and the X-site anion further occupies the position of the chloride ion to avoid affecting the composition of the 3D perovskite material.

[0059] Furthermore, the aromatic rings of phenylethylammonium hydrochloride can be inserted into the perovskite interlayer. These aromatic rings can form coordination bonds with divalent metal ions. This coordination effect restricts the displacement of divalent metal ions, thereby significantly increasing the phase transition activation energy of 3D perovskite materials, reducing the probability of phase transition in 3D perovskite materials, and keeping 3D perovskite materials in the photoactive α phase. This, in turn, helps to reduce abnormalities such as cracking and interface peeling caused by phase transition in 3D perovskite materials.

[0060] In summary, the preparation method of this application, by incorporating phenylethylammonium hydrochloride, makes the framework layer reaction more complete and can also improve the stability and performance of the FA system perovskite layer, thereby enabling solar cells to achieve improved performance and stability by utilizing the FA system perovskite layer.

[0061] In some embodiments, the second organic cation solution further includes at least one of PbS quantum dots, RbBr, or bis(trifluoromethylbromobenzene). It is understood that PbS quantum dots and RbBr are components of the modified interface sublayer. Bis(trifluoromethylbromobenzene) is a component of the 3D perovskite sublayer.

[0062] Among them, the PbS quantum dots incorporated into the second organic cation solution serve as heterogeneous nucleation sites, reducing the nucleation energy barrier of 3D phase perovskite. Their surface thiol ligands can undergo coordination exchange with the perovskite lattice, promoting interface fusion.

[0063] RbBr can stabilize α-phase 3D perovskite materials over a wider temperature range. + Embedded in 2D perovskite sublayers, partially replacing phenylethylammonium ions, quasi-2D perovskites are formed to reduce interlayer spacing. Br - During the fabrication process, a PbI framework layer is incorporated. Since the Pb-I bond length is 2.98 Å and the Pb-Br bond length is 2.96 Å, the Pb-I bond length is greater than the Pb-Br bond length, which induces lattice contraction and provides a lattice-matched transition for the 3D perovskite phase.

[0064] The bis(trifluoromethyl)bromobenzene molecule can mitigate the impact of water vapor on 3D perovskite materials, inhibit the formation of the δ phase (yellow phase), and promote the formation of perovskite layers with larger grains and lower defect state density. The hydrophobicity of trifluoromethyl (-CF3) can passivate surface dangling bonds and reduce nonradiative recombination.

[0065] Optionally, when the second organic cation solution further includes PbS quantum dots, the concentration of the PbS quantum dots is from 0.01 mg / mL to 10 mg / mL, for example, 0.01 mg / mL, 0.5 mg / mL, 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL, 9 mg / mL, or 10 mg / mL. PbS quantum dots within this concentration range can effectively suppress ion migration and improve carrier mobility.

[0066] Optionally, when the second organic cation solution also includes RbBr, the concentration of RbBr is from 0.01 mg / mL to 10 mg / mL, for example, 0.1 mg / mL, 1 mg / mL, 2 mg / mL, 4 mg / mL, 6 mg / mL, 8 mg / mL, or 10 mg / mL. This concentration range of RbBr effectively maintains the stability of the α-phase 3D perovskite material.

[0067] Optionally, when the second organic cation solution further includes bis(trifluoromethyl)bromobenzene, the concentration of bis(trifluoromethyl)bromobenzene is 0.01 mg / mL to 10 mg / mL, for example, 0.01 mg / mL, 1 mg / mL, 2 mg / mL, 4 mg / mL, 6 mg / mL, 8 mg / mL, or 10 mg / mL. This concentration range of bis(trifluoromethyl)bromobenzene can effectively mitigate the influence of water vapor on 3D perovskite materials, suppress the formation of the δ phase (yellow phase), and promote the formation of perovskite layers with larger grains and lower defect state density.

[0068] In some embodiments, the solvent of the second organic cation solution is ethanol. Alternatively, the solvent of the second organic cation solution includes ethanol and DMSO, and the volume percentage of ethanol is greater than or equal to 60%, for example, 60%, 70%, 80%, 90%, 95%, 98.5%, or 99%. This mixed solvent can slow down the crystallization rate of the FA system 3D perovskite material, reduce porosity defect states, and allow the second organic cation solution to reach the bottom of the framework layer.

[0069] In some embodiments, the step of preparing the skeleton layer includes...

[0070] A framework layer was obtained by co-evaporating CsBr and PbI2 on a substrate using multi-source evaporation.

[0071] In this way, a framework layer with the chemical formula CsPIBr2 is prepared, and a highly stable FA system perovskite layer can be fabricated based on this framework layer.

[0072] In some embodiments, the first organohalide includes FAI, and the concentration of FAI is 0.9 mg / mL to 1.1 mg / mL.

[0073] Furthermore, the first annealing step includes: The substrate with the first wet film formed is annealed at 120°C to 160°C for 8 min to 12 min to form a 2D perovskite sublayer on the surface of the framework layer.

[0074] After the steps of coating with the first organic cation solution and the first annealing, a portion of the framework layer reacts with the first organic cation solution to form a 2D perovskite sublayer. The phenylethylammonium hydrochloride in the 2D perovskite sublayer reduces surface defects in the framework layer. Furthermore, the phenylethylammonium hydrochloride creates nanoscale pores in the remaining framework layer that are conducive to the reaction.

[0075] In some embodiments, the second organohalide includes at least one of FAI or FABr.

[0076] Furthermore, the second annealing step includes: The substrate with the second wet film formed was annealed at 120℃~160℃ for 25 min~35 min to obtain a 3D perovskite sublayer.

[0077] After the steps of coating the second organic cation solution and the second annealing, the second organic cation solution reacts fully with the remaining framework layer to obtain a 3D perovskite sublayer with good stability, few defects, and little lead iodide residue.

[0078] like Figure 1 As shown in the figure, this application discloses a solar cell 10, including a substrate 11, and a first carrier transport layer 12, a perovskite layer 13 and a second carrier transport layer 14 sequentially stacked on the substrate 11 in a direction away from the substrate 11. One of the two layers, the first carrier transport layer 12 and the second carrier transport layer 14, is an electron transport layer and the other is a hole transport layer.

[0079] Wherein, the perovskite layer 13 is the perovskite layer 13 in any of the above embodiments; Alternatively, the perovskite layer 13 is prepared by the preparation method in any of the above embodiments.

[0080] The 2D perovskite sublayer 131 and the 3D perovskite sublayer 132 are sequentially stacked on the first carrier transport layer 12 in a direction away from the substrate 11.

[0081] Because the perovskite layer 13 has advantages such as high temperature resistance, good stability and few defects, it is beneficial to improve the long-term stability and electrical performance of the solar cell 10.

[0082] In some embodiments, when the perovskite layer 13 further includes a quasi-2D perovskite sublayer 133, a modified interface sublayer 134, and a transition sublayer 135, the 2D perovskite sublayer 131, the quasi-2D perovskite sublayer 133, the modified interface sublayer 134, the transition sublayer 135, and the 3D perovskite sublayer 132 are sequentially stacked in a direction away from the substrate 11.

[0083] In this way, the 2D perovskite sublayer 131, the quasi-2D perovskite sublayer 133, the modified interface sublayer 134, the transition sublayer 135, and the 3D perovskite sublayer 132 form a stepped band structure, which further reduces deep level traps, avoids dislocation defects caused by interface lattice mismatch, and reduces the probability of nonradiative recombination.

[0084] Optionally, the substrate 11 is a bottom cell, such as a crystalline silicon bottom cell. When the substrate 11 is a bottom cell, the solar cell 10 is a perovskite tandem solar cell.

[0085] Optionally, the solar cell 10 further includes a transparent conductive layer 15 disposed between the first carrier transport layer 12 and the substrate 11.

[0086] Furthermore, the solar cell 10 also includes a transparent electrode layer 16 and a metal electrode 17 disposed on the second carrier transport layer 14 in a direction away from the substrate 11.

[0087] Since the perovskite layer 13 of this application is a FA system perovskite layer, the decomposition temperature of FA ions is relatively high and the component loss rate under high temperature aging is relatively low, thereby avoiding the lattice collapse problem caused by extreme high temperature environment, and at the same time helping to reduce the fill factor loss of perovskite tandem solar cell after sintering metal electrode 17.

[0088] Of course, the substrate 11 can also be a conductive substrate. When the substrate 11 is a conductive substrate, the solar cell 10 is a single-junction perovskite solar cell.

[0089] This application discloses a photovoltaic module, including a plurality of electrically connected solar cells, at least one of which is a solar cell as described in any of the above embodiments.

[0090] The technical solution of the present invention will be described below with reference to embodiments and comparative examples.

[0091] Example 1 The method for fabricating the solar cell in this embodiment includes the following steps: S1. Fabrication of the transparent conductive layer and hole transport layer: A transparent conductive layer and a hole transport layer are sequentially deposited on the top surface of the crystalline silicon bottom cell using physical vapor deposition (PVD). The hole transport layer is made of nickel oxide (NiO). xThe thickness is 80 nm. The transparent conductive layer is made of transparent conductive oxide and has a thickness of 100 nm.

[0092] S2. Preparation of the perovskite layer, including: S21. Preparation of the framework layer: The framework layer with a thickness of 260 nm is obtained by co-evaporation of CsBr and PbI2 on the substrate through multi-source evaporation.

[0093] S22. Coating the first organic cation solution: 10 mL of the first organic cation solution is slit-coated onto the surface of the framework layer to form a first wet film. The solutes of the first organic cation solution include FAI and phenylethylammonium hydrochloride, and the concentration of FAI is 1 mg / mL, the concentration of phenylethylammonium hydrochloride is 1.5 mg / mL, and the solvent is ethanol.

[0094] S23. First annealing step: Place the substrate with the first wet film in 150°C for annealing for 10 min to form a 2D perovskite sublayer with a thickness of 15 nm.

[0095] S24. Coating the Second Organic Cation Solution: 100 mL of the second organic cation solution is slit-coated onto the surface of the 2D perovskite sublayer to form a second wet film. The solutes in the second organic cation solution include FAI, FABr, PbS quantum dots, RbBr, and bis(trifluoromethyl)bromobenzene. The concentrations of FAI, FABr, PbS quantum dots, RbBr, and bis(trifluoromethyl)bromobenzene are 20 mg / mL, 26 mg / mL, 0.7 mg / mL, 1.2 mg / mL, and 2 mg / mL. The solvent for the second organic cation solution is a mixture of ethanol and DMSO, with ethanol comprising 98.5% by volume.

[0096] S25. Second annealing step: The substrate with the second wet film formed is annealed at 150°C for 30 min to obtain a 3D perovskite sublayer with a thickness of 370 nm.

[0097] S3. Fabrication of the electron transport layer: An electron transport layer is deposited on the side of the 3D perovskite sublayer facing away from the crystalline silicon base cell. The material is C. 60 The thickness is 50 nm.

[0098] S4. Fabrication of transparent electrode layer: A transparent electrode layer with a thickness of 150 nm is deposited on the side of the electron transport layer away from the crystalline silicon bottom cell by physical vapor deposition (PVD).

[0099] S5. Preparation of metal electrode: Print silver paste on the side of the transparent electrode layer away from the crystalline silicon bottom cell, sinter at 180°C for 30 min to obtain metal electrode, and then evaporate a layer of LiF.

[0100] Example 2 The only difference between this embodiment and Example 1 is that PbS quantum dots are not added to the second organic cation solution.

[0101] Example 3 The only difference between this embodiment and Example 1 is that RbBr is not added to the second organic cation solution.

[0102] Example 4 The only difference between this embodiment and Example 1 is that bis(trifluoromethylbromobenzene) is not added to the second organic cation solution.

[0103] Comparative Example 1 The only difference between this comparative example and Example 1 is that phenylethylammonium hydrochloride is not added to the first organic cation solution.

[0104] Solar cell performance testing: Performance tests and MPPT (Maximum PowerPoint Tracking) tests were conducted on the solar cells fabricated in each embodiment and comparative example. The MPPT test method is as follows: the temperature was 25°C, the test environment was a nitrogen (N2) atmosphere, and the light intensity was 1 sun (standard light intensity condition). The average decay T90 measured by the MPPT test refers to the cumulative operating time required for the device to decay from its initial maximum power to retaining only 90% of its initial maximum power. The test results are shown in Table 1.

[0105] Table 1: Performance Test Results of Solar Cells

[0106] The following analysis of each embodiment and comparative example is based on Table 1.

[0107] Improvement of solar cell performance by phenylethylammonium hydrochloride: In Comparative Example 1, the absence of phenylethylammonium hydrochloride resulted in the failure to form a 2D perovskite sublayer, leading to increased surface defect density in the perovskite layer and consequently, deteriorated performance and decreased solar cell conversion efficiency. In contrast, Example 1, with the addition of phenylethylammonium hydrochloride, reacted with part of the framework layer to form a 2D perovskite sublayer. The insertion of phenylethylammonium ions between the perovskite layers significantly increased the activation energy of the 3D perovskite material phase transition, reducing the probability of phase transition in the FA system and thus improving the stability of the FA system perovskite. This, in turn, enabled the solar cell to achieve improved performance and stability using the FA system perovskite layer. Furthermore, the chloride ions in phenylethylammonium hydrochloride promoted FA ion penetration and accelerated the reaction between FA ions and the framework layer, thereby addressing the issue of metal halide residues at the bottom of the FA system perovskite layer and reducing carrier recombination centers. Consequently, Example 1 showed improvements in conversion efficiency, open-circuit voltage, fill factor, and average decay T90 compared to Comparative Example 1.

[0108] In Example 2, the absence of PbS quantum dots resulted in poor energy level matching between the perovskite layer and the electron transport layer, exacerbating interface charge accumulation, increasing series resistance, and decreasing the fill factor. In contrast, Example 1, with the addition of PbS quantum dots, allowed the dots to bind to B vacancies at the perovskite grain boundaries, suppressing ion migration, increasing carrier mobility, and improving energy level matching between the perovskite layer and the electron transport layer. Consequently, Example 1 exhibited improved fill factor, conversion efficiency, and average decay T90 compared to Example 2.

[0109] In Example 3, due to the absence of RbBr, the crystallization process resulted in disordered growth, with grain size decreasing from the micrometer level to the submicrometer level. This led to increased grain boundary density, perovskite layer defects, and poor stability. In contrast, Example 1, with the addition of RbBr, allowed the α-phase 3D perovskite material to remain stable over a wider temperature range, reducing perovskite layer defects. Consequently, Example 1 exhibited improved conversion efficiency and average attenuation T90 compared to Example 3.

[0110] Example 4: Due to the absence of bis(trifluoromethyl)bromobenzene, a hydrophilic region forms at the perovskite layer interface, which easily induces ion migration and accumulation, increasing series resistance. Water molecule penetration accelerates PbI2 formation, inducing perovskite phase separation. Unpassivated Pb... 2+ Defects increase the carrier recombination rate. Compared to Example 4, the bis(trifluoromethyl)bromobenzene molecule added in Example 1 can reduce the influence of water vapor on 3D perovskite materials, suppress the formation of the δ phase (yellow phase), and promote the formation of a perovskite layer with larger grains and lower defect state density. As a result, the conversion efficiency and average attenuation T90 of Example 1 are significantly improved compared to Example 4, and the series resistance is significantly reduced.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A perovskite layer, characterized in that, It includes stacked 2D perovskite sublayers and 3D perovskite sublayers; The 3D perovskite sublayer comprises 3D perovskite material with the chemical formula ABX3 and chloride ions, and the 2D perovskite sublayer contains phenylethylammonium ions; Wherein, A is an A-position cation, B is a B-position cation, X is an X-position anion, the A-position cation includes an organic cation, and the organic cation is a FA ion, the B-position cation includes a divalent metal ion, and the X-position anion includes a halide ion.

2. The perovskite layer according to claim 1, characterized in that, The perovskite layer further includes a quasi-2D perovskite sublayer, which is disposed between the 2D perovskite sublayer and the 3D perovskite sublayer. The general chemical formula of the 2D perovskite sublayer is (PEA). m1 (FA) n1 PbI x1 Br y1 Wherein, PEA is phenylethylammonium ion, m1, n1, x1 and y1 are all positive numbers, and satisfy the following relationship: m1+n1=2, and x1+y1=4; The chemical formula of the quasi-2D perovskite sublayer is (PEA). m2 (FA) n2 Rb k PbI x2 Br y2 Wherein, PEA is phenylethylammonium ion, m2, n2, k, x2 and y2 are all positive numbers, and satisfy the following relationship: m2+n2+k=2, x2+y2=4.

3. The perovskite layer according to claim 2, characterized in that, The perovskite layer further includes a modified interface sublayer and a transition sublayer, wherein the 2D perovskite sublayer, the quasi-2D perovskite sublayer, the modified interface sublayer, the transition sublayer, and the 3D perovskite sublayer are stacked sequentially. The modified interface sublayer includes PbS and RbBr; The chemical formula of the transition sublayer is PbI. x3 Br y3 Where x3 and y3 are both positive numbers and satisfy the following relationship: x3 + y3 = 2.

4. The perovskite layer according to any one of claims 1 to 3, characterized in that, The A-site cation further includes at least one of Cs ions and Rb ions; and / or, The divalent metal ions include Pb ions; and / or, The halide ion includes at least one of I- ions or Br- ions; and / or The 3D perovskite sublayer also includes bis(trifluoromethyl)bromobenzene.

5. A method for preparing a perovskite layer, characterized in that, Includes the following steps: Preparation of the framework layer: The framework layer is prepared on a substrate; wherein the framework layer comprises a divalent metal halide with the chemical formula BX2; wherein B is a B-position cation, X is an X-position anion, the B-position cation comprises a divalent metal ion, and the X-position anion comprises a halide ion; Coating with a first organic cation solution: The first organic cation solution is coated on the framework layer to form a first wet film; wherein, the first organic cation solution includes a first organic halide with the chemical formula AX and phenylethylammonium hydrochloride; A is an A-site cation, X is an X-site anion, the A-site cation includes an organic cation, and the organic cation is FA ion; First annealing: The substrate on which the first wet film is formed is subjected to a first annealing to form a 2D perovskite sublayer; Coating with a second organic cation solution: The second organic cation solution is coated onto the skeleton layer after the first annealing to form a second wet film; wherein, the second organic cation solution includes a second organic halide with the chemical formula AX; Second annealing: The substrate on which the second wet film is formed is subjected to a second annealing to form a 3D perovskite sublayer, thereby obtaining the perovskite layer.

6. The preparation method according to claim 5, characterized in that, The second organic cation solution also includes at least one of PbS quantum dots, RbBr, or bis(trifluoromethyl)bromobenzene.

7. The preparation method according to claim 6, characterized in that, When the second organic cation solution also includes PbS quantum dots, the concentration of PbS quantum dots is 0.01 mg / mL to 10 mg / mL; When the second organic cation solution also includes RbBr, the concentration of RbBr is 0.01 mg / mL to 10 mg / mL; When the second organic cation solution also includes bis(trifluoromethyl)bromobenzene, the concentration of bis(trifluoromethyl)bromobenzene is 0.01 mg / mL to 10 mg / mL.

8. The preparation method according to claim 5, characterized in that, The solvent for the second organic cation solution is ethanol; Alternatively, the solvent of the second organic cation solution includes ethanol and DMSO, and the volume percentage of ethanol is greater than or equal to 60%.

9. The preparation method according to any one of claims 5 to 8, characterized in that, The step of preparing the skeleton layer includes: The framework layer was obtained by co-evaporating CsBr and PbI2 on the substrate through multi-source evaporation. And / or, the first organohalide includes a FAI, and the concentration of the FAI is 0.9 mg / mL to 1.1 mg / mL; And / or, the first annealing step includes: The substrate on which the first wet film is formed is annealed at 120°C to 160°C for 8 min to 12 min to form the 2D perovskite sublayer on the surface of the framework layer. And / or, the second organohalide includes at least one of FAI or FABr; And / or, the second annealing step includes: The substrate on which the second wet film is formed is annealed at 120°C to 160°C for 25 min to 35 min to obtain the 3D perovskite sublayer.

10. A solar cell, characterized in that, It includes a substrate, and a first carrier transport layer, a perovskite layer and a second carrier transport layer sequentially stacked on the substrate in a direction away from the substrate. One of the two carrier transport layers is an electron transport layer and the other is a hole transport layer. Wherein, the perovskite layer is the perovskite layer according to any one of claims 1 to 4; Alternatively, the perovskite layer is prepared by the preparation method according to any one of claims 5 to 9; The 2D perovskite sublayer and the 3D perovskite sublayer are sequentially stacked on the first carrier transport layer in a direction away from the substrate.

11. The solar cell according to claim 10, characterized in that, When the perovskite layer further includes a quasi-2D perovskite sublayer, a modified interface sublayer, and a transition sublayer, the 2D perovskite sublayer, the quasi-2D perovskite sublayer, the modified interface sublayer, the transition sublayer, and the 3D perovskite sublayer are sequentially stacked in a direction away from the substrate; and / or, The substrate is a bottom battery.

12. A photovoltaic module, characterized in that, It includes a plurality of electrically connected solar cells, at least one of which is the solar cell of claim 10 or 11.

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