Narrow band gap tin lead perovskite absorption layer and solar cell and preparation method thereof

Abstract

This application discloses a narrow bandgap tin-lead perovskite absorber layer and a solar cell, as well as a method for fabricating the same, relating to the field of solar cell technology. A source solution is formed by dissolving glutamate hydrochloride in isopropanol, and a FA is then formed on the hole transport layer. 0.7 MA 0.3 Sn 0.5 Pb 0.5 An I3 wet film is pre-annealed; 60-100 μL of source solution is applied to an absorbent carrier, spaced apart from the pre-annealed perovskite film on the heating support surface, and a confined annealing space is formed by the enclosure and the heating support surface; a secondary annealing is performed within the confined annealing space for 12-18 minutes, allowing the gaseous components released from the source solution to act on the perovskite film in a non-contact manner. This method can extend the grain growth window, promote grain growth, and suppress tin ion oxidation and passivation defects in the film layer, thereby improving the crystallinity quality of the absorber layer.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a narrow bandgap tin-lead perovskite absorber layer and solar cells, and their fabrication methods. Background Technology

[0002] Perovskite solar cells are characterized by high absorption coefficients, tunable band gaps, and low fabrication temperatures. Among them, narrow-bandgap tin-lead perovskite materials, by adjusting the tin-lead ratio, can extend the absorption of near-infrared light in solar cells. They can be used to fabricate narrow-bandgap single-junction solar cells or as the bottom sub-cell in all-perovskite tandem solar cells. The quality of the narrow-bandgap tin-lead perovskite absorber layer directly affects the generation, transport, and collection of photogenerated carriers, thus influencing the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the solar cell.

[0003] Narrow bandgap tin-lead perovskite absorber layers are typically prepared using solution methods. For example, a perovskite precursor containing lead, tin, formamidinium, and methylamine salts is dissolved in organic solvents such as N,N-dimethylformamide and dimethyl sulfoxide. The resulting perovskite precursor solution is then coated onto a hole transport layer to form a wet perovskite film. Annealing is then performed to allow the solvent to escape, completing the nucleation and growth of perovskite crystals. During this process, the solvent escape rate from the wet film affects the nucleation density, grain growth time, and final film morphology of the perovskite crystals.

[0004] When perovskite wet films are annealed directly in an open environment, N,N-dimethylformamide and dimethyl sulfoxide readily escape from the film surface, causing the perovskite precursor to reach a supersaturated state quickly and form numerous crystal nuclei. This limits the time available for grain growth and fusion, resulting in perovskite absorber layers with problems such as small grain size, numerous grain boundaries, localized porosity, and residual lattice strain. Defects such as uncoordinated metal ions and halogen vacancies easily form at grain boundaries and pores, leading to nonradiative recombination of charge carriers.

[0005] In addition, Sn in tin-lead perovskite materials 2+ It is easily oxidized to Sn during film formation and annealing. 4+ Sn 4+ The formation of tin oxide can cause self-doping in the perovskite absorber layer and increase the defect state density, which is detrimental to carrier lifetime and transport. Existing technologies can suppress tin oxidation or passivate defects by directly adding reducing or passivating additives to the perovskite precursor solution, or by directly coating the treatment solution onto the perovskite film surface after film formation. However, directly adding additives to the precursor solution may alter the coordination state, solvent system, and crystallization process of the precursor; directly applying the treatment solution to the perovskite film surface may result in excessively high local concentrations of treated species, film component migration, or changes in surface morphology.

[0006] Therefore, existing methods for preparing narrow-bandgap tin-lead perovskite absorber layers still struggle to suppress Sn while simultaneously regulating solvent escape from the wet film and grain growth. 2+ To address the oxidation and passivation of defects in the film, it is necessary to provide a method for preparing a narrow-bandgap tin-lead perovskite absorber layer that can simultaneously achieve dynamic crystallization control of perovskite, suppression of tin oxidation, and passivation of defects. Summary of the Invention

[0007] A first aspect of this invention aims to provide a method for preparing a narrow bandgap tin-lead perovskite absorber layer, solving the problems in the prior art where rapid solvent evaporation during the preparation of narrow bandgap tin-lead perovskite absorber layers leads to small grain size, numerous grain boundaries and pores, and Sn... 2+ The device is prone to oxidation and has a high defect state density, which leads to increased nonradiative recombination and limited photoelectric conversion performance.

[0008] Another objective of the first aspect of the present invention is to enable the perovskite wet film to form a preliminary crystalline phase and structural strength while retaining an appropriate amount of residual solvent, thereby balancing the stability of the film layer and the grain growth space during the secondary annealing stage.

[0009] The second aspect of this invention aims to provide a method for fabricating narrow bandgap tin-lead perovskite solar cells.

[0010] The third aspect of this invention aims to provide a narrow bandgap tin-lead perovskite solar cell prepared according to the preparation method of any one of the preceding claims.

[0011] According to a first aspect of the present invention, the present invention provides a method for preparing a narrow bandgap tin-lead perovskite absorber layer, comprising the following steps: Glutamate hydrochloride was dissolved in isopropanol to obtain a glutamate hydrochloride / isopropanol source solution; A narrow bandgap tin-lead perovskite wet film is formed on the hole transport layer, wherein the material of the narrow bandgap tin-lead perovskite wet film is FA. 0.7 MA 0.3 Sn 0.5 Pb 0.5 I3; The narrow bandgap tin-lead perovskite wet film is placed on a heated bearing surface for pre-annealing treatment to obtain a pre-annealed perovskite film. A 60 μL-100 μL solution of the glutamate hydrochloride / isopropanol source is applied to the liquid-absorbing carrier, and the liquid-absorbing carrier and the pre-annealed perovskite film are disposed alternately on the heating support surface. An open cover is placed over the liquid-absorbing carrier and the pre-annealed perovskite film, and the opening edge of the cover is supported on the heating support surface, so that the cover and the heating support surface enclose a confined annealing space that restricts the outward escape of gaseous components. The pre-annealed perovskite film is subjected to a second annealing treatment for 12-18 minutes within the confined annealing space, so that the gas phase components released from the glutamate hydrochloride / isopropanol source solution come into contact with the pre-annealed perovskite film, while the glutamate hydrochloride / isopropanol source solution does not directly contact the pre-annealed perovskite film, thus obtaining the narrow bandgap tin-lead perovskite absorber layer.

[0012] Optionally, the pre-annealing time can be any value between 2 min and 8 min.

[0013] Optionally, the concentration of the glutamate hydrochloride / isopropanol source solution is any value between 5 mg / mL and 6 mg / mL.

[0014] Optionally, after the secondary annealing process within the confined annealing space, the process further includes: An isopropanol solution of ethylenediammonium diiodide was spin-coated onto the surface of the annealed perovskite film, followed by surface passivation annealing. The concentration of the isopropanol solution of the ethylenediamine diiodide is any value between 0.5 mg / mL and 1.5 mg / mL.

[0015] Optionally, the perovskite precursor solution used to form the narrow bandgap tin-lead perovskite wet film includes PbI2, SnI2, FAI, and MAI, and the solvent of the perovskite precursor solution is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide.

[0016] Optionally, the narrow bandgap tin-lead perovskite wet film is formed by a two-step spin coating method, the two-step spin coating method comprising: The first spin coating step is performed at the first rotation speed for the first preset time. The second spin coating is performed at the second rotation speed for the second preset time, and 500μL-700μL of chlorobenzene is added as an anti-solvent during the 28s-32s of the second spin coating.

[0017] According to a second aspect of the present invention, the present invention also provides a method for fabricating a narrow bandgap tin-lead perovskite solar cell, comprising the following steps: A PEDOT:PSS hole transport layer is formed on an ITO / glass transparent conductive substrate; Using the above preparation method, a narrow bandgap tin-lead perovskite absorber layer is formed on the PEDOT:PSS hole transport layer; C is sequentially formed on the narrow bandgap tin-lead perovskite absorber layer60 The narrow bandgap tin-lead perovskite solar cell is prepared by comprising an electron transport layer, a hole blocking layer, and a copper electrode layer.

[0018] Optionally, the thickness of the PEDOT:PSS hole transport layer is 30nm-50nm, the thickness of the narrow bandgap tin-lead perovskite absorber layer is 1000nm-1200nm, and the C 60 The electron transport layer has a thickness of 20nm-30nm, the hole blocking layer has a thickness of 6nm-8nm, and the copper electrode layer has a thickness of 100nm-200nm.

[0019] According to a third aspect of the present invention, the present invention also provides a narrow bandgap tin-lead perovskite solar cell prepared according to the preparation method of any one of the preceding claims.

[0020] This invention, through a combination of pre-annealing, non-contact liquid source supply, and confined space secondary annealing, allows the gaseous components released from the glutamate hydrochloride / isopropanol source solution to act on the pre-annealed perovskite membrane in a relatively mild and uniform manner. This avoids direct contact between the source solution and the perovskite membrane, which could lead to excessively high local concentrations, membrane dissolution, or contamination, while simultaneously suppressing Sn concentration in the perovskite membrane. 2+ To Sn 4+ The oxidation process passes off defects such as uncoordinated metal ions and halogen vacancies on the film surface and at grain boundaries. Simultaneously, the confined annealing space slows the outward escape of gaseous components and residual solvents within the film, maintaining a suitable crystal growth environment for the perovskite film during secondary annealing. This promotes continued grain growth and reduces grain boundaries and porosity, thereby reducing non-radiative recombination of charge carriers within the film and at interfaces. This improves the crystal quality and carrier transport performance of the narrow-bandgap tin-lead perovskite absorber layer, and ultimately enhances the open-circuit voltage, fill factor, photoelectric conversion efficiency, and operational stability of the solar cell.

[0021] Furthermore, the pre-annealing time of the present invention is any value between 2 min and 8 min, which allows some N,N-dimethylformamide and dimethyl sulfoxide in the perovskite wet film to escape and form a pre-annealed perovskite film with preliminary crystal phase and structural strength, while retaining residual solvent for continued grain growth. This avoids both film flow, deformation or excessive crystal nuclei caused by too short a pre-annealing time, and premature crystallization of the perovskite film caused by too long a pre-annealing time, thus shortening the grain growth window of the secondary annealing stage.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0023] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing a narrow bandgap tin-lead perovskite absorber layer according to an embodiment of the present invention; Figure 2 This is a comparative schematic diagram of the perovskite film crystallization process corresponding to open annealing and confined atmosphere secondary annealing. Figure 3 This is a schematic diagram illustrating the mechanism of perovskite grain growth through Ostwald ripening during secondary annealing in a confined atmosphere. Figure 4 This is a negative secondary ion time-of-flight secondary ion mass spectrum depth distribution diagram of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1; Figure 5 This is a depth distribution map of positive secondary ion time-of-flight secondary ion mass spectrometry of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1; Figure 6 This is a schematic diagram of the stacked structure of the narrow bandgap tin-lead perovskite solar cell obtained in Example 1; Figure 7 This is a current density-voltage curve of the narrow bandgap tin-lead perovskite solar cell obtained in Comparative Example 1 under forward and reverse scanning conditions. Figure 8 This is a current density-voltage curve of the narrow bandgap tin-lead perovskite solar cell obtained in Example 1 under forward and reverse scanning conditions; Figure 9 These are the external quantum efficiency curves of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1 and Comparative Example 1; Figure 10 This is a statistical distribution diagram of the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1 and Comparative Example 1. Figure 11 These are scanning electron microscope images of the surface and cross-section of the narrow bandgap tin-lead perovskite absorber layers obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 12 These are X-ray diffraction patterns of the narrow bandgap tin-lead perovskite absorbing layers obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 13 These are X-ray diffraction patterns of the narrow bandgap tin-lead-perovskite absorbing layer obtained in Example 1 at different tilt angles; Figure 14The X-ray diffraction patterns of the narrow bandgap tin-lead perovskite absorption layer obtained in Comparative Example 1 at different tilt angles are shown. Figure 15 This is a fitting curve of the diffraction angle and the square of the tilt angle of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1 and Comparative Example 1; Figure 16 This is the X-ray photoelectron spectroscopy peak fitting diagram of the Sn 3d5 / 2 energy level of the narrow bandgap tin-lead perovskite absorption layer obtained in Comparative Example 1; Figure 17 This is a fitting diagram of the X-ray photoelectron spectroscopy peaks of the Sn 3d5 / 2 energy level of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1; Figure 18 This is a graph showing the open-circuit voltage of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1, Comparative Example 1, and Comparative Example 2 as a function of incident light intensity. Figure 19 This is a statistical distribution diagram of the performance parameters of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1, Comparative Example 6, and Comparative Example 7. Figure 20 This is a statistical distribution diagram of the performance parameters of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1, Comparative Example 8, and Comparative Example 9; Figure 21 This is the current density-voltage curve of the rigid two-terminal all-perovskite tandem solar cell obtained in Example 2; Figure 22 This is an external quantum efficiency curve of the wide bandgap top sub-cell and the narrow bandgap bottom sub-cell obtained in Example 2.

[0024] Figure label: 100 - Narrow bandgap tin-lead perovskite solar cell, 10 - substrate, 20 - transparent conductive layer, 30 - hole transport layer, 40 - narrow bandgap tin-lead perovskite absorber layer, 50 - electron transport layer, 60 - hole blocking layer, 70 - copper electrode layer. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0027] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Figure 1 This is a flowchart of a method for preparing a narrow bandgap tin-lead perovskite absorber layer according to an embodiment of the present invention. Figure 2 This is a comparative schematic diagram of the perovskite film crystallization process corresponding to open annealing and confined atmosphere secondary annealing. Figure 3 This is a schematic diagram illustrating the mechanism of perovskite grain growth through Ostwald ripening during confined atmosphere secondary annealing. Figure 4 This is a negative secondary ion time-of-flight mass spectrometry depth distribution map of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1. Figure 5 This is a depth distribution map of the positive secondary ion time-of-flight mass spectrometry of the narrow bandgap tin-lead perovskite absorption layer obtained in Example 1. Figure 6 This is a schematic diagram of the stacked structure of the rigid two-end all-perovskite tandem solar cell obtained in Example 2.

[0030] like Figure 1 and Figure 2 As shown, the present invention provides a method for preparing a narrow bandgap tin-lead perovskite absorber layer 40, comprising the following steps: Step S100: Dissolve glutamate hydrochloride in isopropanol to obtain a glutamate hydrochloride / isopropanol source solution; Step S200: A narrow bandgap tin-lead perovskite wet film is formed on the hole transport layer 30. The material of the narrow bandgap tin-lead perovskite wet film is FA. 0.7 MA 0.3 Sn 0.5 Pb 0.5 I3; Step S300: Place the narrow bandgap tin-lead perovskite wet film on the heated support surface for pre-annealing treatment to obtain a pre-annealed perovskite film; Step S400: Apply 60 μL-100 μL of glutamate hydrochloride / isopropanol source solution to the liquid-absorbing carrier, and place the liquid-absorbing carrier and the pre-annealed perovskite film alternately on the heating support surface. The volume of the glutamate hydrochloride / isopropanol source solution can be 60 μL, 70 μL, 80 μL, 90 μL or 100 μL, or any other value between 60 μL and 100 μL. Step S500: Cover the liquid-absorbing liquid carrier and the pre-annealed perovskite film with an open cover, and support the opening edge of the cover on the heating support surface, so that the cover and the heating support surface enclose a confined annealing space that restricts the outward escape of gaseous components. Step S600: The pre-annealed perovskite film undergoes a secondary annealing treatment for 12-18 minutes within a confined annealing space. This allows the gaseous components released from the glutamate hydrochloride / isopropanol source solution to contact the pre-annealed perovskite film, while ensuring that the glutamate hydrochloride / isopropanol source solution does not directly contact the pre-annealed perovskite film. This yields a narrow bandgap tin-lead perovskite absorber layer 40. The secondary annealing time can be 12, 13, 14, 15, 16, 17, or 18 minutes, or any other value within the 12-18 minute range. Here, the solvent for the narrow bandgap tin-lead perovskite wet film is N,N-dimethylformamide and dimethyl sulfoxide.

[0031] In this embodiment, the combination of pre-annealing, non-contact liquid source supply, and confined space secondary annealing allows the gaseous components released from the glutamate hydrochloride / isopropanol source solution to act on the pre-annealed perovskite membrane in a relatively mild and uniform manner. This avoids direct contact between the source solution and the perovskite membrane, which could lead to excessively high local concentrations, membrane dissolution, or contamination, while simultaneously suppressing Sn concentration in the perovskite membrane. 2+ To Sn 4+The oxidation of the perovskite film is reduced, and defects such as uncoordinated metal ions and halogen vacancies on the film surface and at grain boundaries are passivated. Simultaneously, the confined annealing space slows the outward escape of gaseous components and residual solvent within the film, maintaining a suitable crystal growth environment during the secondary annealing process. This promotes continued grain growth and reduces grain boundaries and porosity, thereby reducing non-radiative recombination of charge carriers within the film and at the interface. This improves the crystal quality and carrier transport performance of the narrow-bandgap tin-lead perovskite absorber layer 40, and also helps improve the open-circuit voltage, fill factor, photoelectric conversion efficiency, and operational stability of the solar cell. Specifically, limiting the source solution volume to 60μL-100μL and the secondary annealing time to 12min-18min balances the supply of gaseous components and the treatment time, avoiding insufficient passivation and anti-oxidation effects due to insufficient supply or treatment time, and also avoiding adverse effects on the compositional uniformity and interface state of the perovskite film due to excessive supply or treatment time.

[0032] In this embodiment, the pre-annealing treatment first causes some organic solvents to escape from the narrow-bandgap tin-lead perovskite wet film, and allows the perovskite crystals to form a preliminary crystal phase and film framework. This reduces the possibility of film disturbance caused by the gaseous components released from the source solution acting on the unformed wet film, while reserving some controllable space for subsequent grain growth. During the secondary annealing process, isopropanol volatilizes upon heating, promoting the entry of chlorine- and carboxyl-containing treatment species derived from glutamate hydrochloride into the confined annealing space. The liquid-absorbing carrier absorbs and stores the source solution, allowing the source solution to gradually release gaseous components and reducing the instantaneous evaporation rate. Because the liquid-absorbing carrier is spaced apart from the pre-annealed perovskite film, the source solution does not directly wet the perovskite film, but acts on the film surface through gas-phase mass transfer, making the treatment species more uniformly distributed on the perovskite film. The confined annealing space formed by the enclosure and the heating support surface restricts the rapid outward escape of gaseous components, allowing the treatment species to maintain a certain concentration and residence time around the pre-annealed perovskite film.

[0033] Furthermore, the above-mentioned processing environment can reduce Sn 2+ It is oxidized to Sn during the heating process. 4+ This process reduces self-doping and defect state density caused by tin oxidation. Furthermore, chloride ions and carboxyl-containing species derived from glutamate hydrochloride can interact with uncoordinated Sn / Pb ions on the film surface or at grain boundaries, passivating defects such as halogen vacancies. Simultaneously, the confined annealing space modulates the residual solvent escape rate, allowing already formed perovskite nuclei to continue growing and fusing during the secondary annealing stage, resulting in larger grains and a reduced number of grain boundaries.

[0034] like Figure 3As shown, within the confined annealing space, the rate of outward escape of N,N-dimethylformamide and dimethyl sulfoxide in the perovskite wet film is limited, maintaining a certain solvent content in the film during the secondary annealing process. This slows down the nucleation rate of the perovskite crystals and extends the crystal growth window. During this process, smaller grains with higher surface energy gradually dissolve, and their constituent ions migrate through the mass transfer channels provided by the residual solvent and redeposit towards larger grains with lower surface energy. This allows the smaller grains to gradually incorporate into the larger grains through Ostwald ripening, ultimately forming a narrow-bandgap tin-lead perovskite absorber layer 40 with larger grain size, fewer grain boundaries, and a relatively dense film.

[0035] like Figure 4 and Figure 5 As shown, the yellow area corresponds to the narrow bandgap tin-lead perovskite absorber layer 40, and the blue area includes the PEDOT:PSS hole transport layer 30 and the ITO transparent conductive layer 20 located below the narrow bandgap tin-lead perovskite absorber layer 40. SO3H - InO2 is a characteristic ion of the PEDOT:PSS hole transport layer 30. - These are characteristic ions of the ITO transparent conductive layer 20.

[0036] like Figure 4 As shown, I - The signal maintains a high intensity within the perovskite absorption layer and gradually decreases in the PEDOT:PSS / ITO region; InO2 - and SO3H - The signal is weaker within the perovskite absorption layer and increases near the PEDOT:PSS / ITO region. - and COOH - The signal is mainly distributed in the region near the surface of the perovskite absorber layer and gradually attenuates from the surface inwards. This indicates that during secondary annealing within a confined annealing space, the chlorine- and carboxyl-containing gaseous components released from the glutamate hydrochloride / isopropanol source solution can contact the pre-annealed perovskite film and migrate from the surface inwards. Carboxyl-containing species can coordinate with uncoordinated Sn / Pb ions on the film surface and at grain boundaries, while chlorine-containing species can act on halogen vacancies, thereby reducing defect sites in the perovskite absorber layer.

[0037] like Figure 5 As shown, Pb 2+ Sn 2+ And CH5N2 corresponding to the FA and MA components respectively + CH6N + The signal is continuously distributed within the perovskite absorption layer and decreases near the PEDOT:PSS / ITO region; In3 +The signal is weak within the perovskite absorber layer and increases after entering the ITO region. The above ion distribution can define the interface between the perovskite absorber layer and the PEDOT:PSS / ITO region, and indicates that after secondary annealing in a confined space, the tin, lead, FA, and MA components remain within the perovskite absorber layer, without film dissolution or large-scale component migration due to gas phase treatment. This allows the gas phase components derived from glutamate hydrochloride to maintain the main composition and layered structure of the narrow bandgap tin-lead perovskite absorber layer 40 while simultaneously modifying the surface and passivating defects in the film.

[0038] In a further embodiment, the pre-annealing time is any value between 2 min and 8 min, for example, 2 min, 3 min, 4 min, 5 min, 6 min, or 8 min, or any other value within the above range. This allows some of the N,N-dimethylformamide and dimethyl sulfoxide in the perovskite wet film to escape and form a pre-annealed perovskite film with preliminary crystalline phase and structural strength, while retaining residual solvent for continued grain growth. This avoids both excessively short pre-annealing time leading to film flow, deformation, or excessive crystal nuclei, and excessively long pre-annealing time leading to premature crystallization of the perovskite film and shortening the grain growth window of the secondary annealing stage.

[0039] In a further embodiment, the concentration of the glutamate hydrochloride / isopropanol source solution is any value between 5 mg / mL and 6 mg / mL, for example, 5 mg / mL, 5.2 mg / mL, 5.4 mg / mL, 5.5 mg / mL, 5.8 mg / mL, or 6 mg / mL, or any other value within the above range. This allows the absorbent carrier to continuously release an appropriate amount of the glutamate hydrochloride-derived treatment species during the secondary annealing process and maintain the corresponding treatment species concentration within the confined annealing space, thereby reducing Sn. 2+ It is oxidized to Sn during the annealing process. 4+ It also passivates defects on the surface and grain boundaries of the perovskite film, while avoiding insufficient treatment due to too low a concentration of the source solution or excessive accumulation of treated species on the film surface due to too high a concentration.

[0040] In a further embodiment, after the secondary annealing process within the confined annealing space, the process further includes: An isopropanol solution of ethylenediammonium diiodide was spin-coated onto the surface of the annealed perovskite film, followed by surface passivation annealing. The concentration of the isopropanol solution of ethylenediamine diiodide is any value between 0.5 mg / mL and 1.5 mg / mL, for example, it can be 0.5 mg / mL, 0.7 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.2 mg / mL or 1.5 mg / mL, or any other value within the above range.

[0041] In this embodiment, an isopropanol solution of ethylenediammonium diiodide at a concentration of 0.5 mg / mL to 1.5 mg / mL is spin-coated onto the surface of the perovskite film after secondary annealing. This allows the ethylenediammonium cations and iodide ions to interact with uncoordinated metal ions and iodine vacancies on the film surface, reducing defect states on the perovskite absorber layer surface and improving the interfacial contact between the perovskite absorber layer and the subsequently formed electron transport layer 50. Controlling the concentration of ethylenediammonium diiodide within the aforementioned range avoids insufficient surface passivation due to excessively low concentrations and the formation of an excessively thick capping layer that hinders carrier transport due to excessively high concentrations.

[0042] In a further embodiment, the perovskite precursor solution used to form a narrow bandgap tin-lead perovskite wet film includes PbI2, SnI2, FAI, and MAI, and the solvent of the perovskite precursor solution is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide. PbI2 and SnI2 provide lead and tin sources, respectively, and FAI and MAI provide formamidin and methylamine components, respectively, to form FA. 0.7 MA 0.3 Sn 0.5 Pb 0.5 I3 is a narrow bandgap tin-lead perovskite material. N,N-dimethylformamide is used to dissolve the perovskite precursor. Dimethyl sulfoxide can coordinate with lead and tin ions to form intermediate complexes. The mixed solvent formed by the two can regulate the solubility, viscosity, coordination state, and evaporation rate of the perovskite precursor solution, so that the perovskite precursor solution forms a uniformly composed wet film on the hole transport layer 30, and provides conditions for crystal nucleation and grain growth in the subsequent pre-annealing and confined space secondary annealing processes.

[0043] In a preferred embodiment, the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 3:1, and the concentration of the perovskite precursor solution is 2.2 mol / L. This ensures that the wet film retains an appropriate amount of coordination solvent after pre-annealing, providing conditions for ion migration, Ostwald ripening, and continued grain growth during the confined space secondary annealing process.

[0044] In a further embodiment, the narrow bandgap tin-lead perovskite wet film is formed by a two-step spin coating process, which includes: The first spin coating step is performed at the first rotation speed for the first preset time. The second spin coating is performed at a second rotation speed for a second preset time. During the 28th to 32nd second of the second spin coating, 500 μL to 700 μL of chlorobenzene is added as an anti-solvent. That is, the chlorobenzene can be added at the 28th, 29th, 30th, 31st, or 32nd second of the second spin coating, or at any other time between the 28th and 32nd. The amount of chlorobenzene added can be 500 μL, 550 μL, 600 μL, 650 μL, or 700 μL, or at any other value between 500 μL and 700 μL.

[0045] In this embodiment, the first spin coating step is used to spread the perovskite precursor solution on the surface of the hole transport layer 30 to form a liquid film with complete coverage and uniform composition distribution. The second spin coating step is used to remove some solvent and adjust the wet film thickness and surface smoothness. During the 28s-32s of the second spin coating step, 500μL-700μL of chlorobenzene is added dropwise. This utilizes the extraction effect of chlorobenzene on N,N-dimethylformamide and dimethyl sulfoxide to quickly bring the perovskite precursor to a supersaturated state and form uniformly distributed initial crystal nuclei. At the same time, it avoids the liquid film shrinkage or local crystallization caused by adding antisolvent too early, and the uneven distribution of precursor components caused by adding it too late. This forms a narrow-bandgap tin-lead perovskite wet film with suitable thickness, initial nucleation state and residual solvent content, providing conditions for the continued growth of grains in the subsequent pre-annealing and confined space secondary annealing processes.

[0046] The present invention also provides a method for fabricating a narrow bandgap tin-lead perovskite solar cell 100, comprising the following steps: A PEDOT:PSS hole transport layer 30 is formed on an ITO / glass transparent conductive substrate 10; Using the above preparation method, a narrow bandgap tin-lead perovskite absorber layer 40 is formed on the PEDOT:PSS hole transport layer 30; C is sequentially formed on the narrow bandgap tin-lead-perovskite absorber layer 40. 60 A narrow bandgap tin-lead perovskite solar cell 100 is prepared by comprising an electron transport layer 50, a hole blocking layer 60, and a copper electrode layer 70.

[0047] In this embodiment, the ITO / glass transparent conductive substrate 10 is used to allow incident light to enter the device and transmit external current; the PEDOT:PSS hole transport layer 30 is used to selectively extract holes generated by the narrow bandgap tin-lead perovskite absorber layer 40 and block electrons from transporting to the ITO transparent conductive layer 20; the narrow bandgap tin-lead perovskite absorber layer 40 is used to absorb incident light and generate electron-hole pairs; C 60 Electron transport layer 50 is used to extract and transport electrons and block holes from transporting to copper electrode layer 70; hole blocking layer 60 is used to further limit holes from reaching copper electrode layer 70 and reduce C 60Carrier recombination occurs at the interface between the electron transport layer 50 and the copper electrode layer 70; the copper electrode layer 70 is used to collect and output electrons. The above functional layers are stacked sequentially to form an inverted narrow bandgap tin-lead perovskite solar cell 100 to achieve light absorption, carrier separation, selective transport, and charge collection.

[0048] In a further embodiment, the thickness of the PEDOT:PSS hole transport layer 30 is 30nm-50nm, for example, it can be 30nm, 35nm, 40nm, 45nm or 50nm, or any other value among 30nm-50nm; the thickness of the narrow bandgap tin-lead perovskite absorber layer 40 is 1000nm-1200nm, for example, it can be 1000nm, 1050nm, 1100nm, 1150nm or 1200nm, or any other value among 1000nm-1200nm. 60 The electron transport layer 50 has a thickness of 20nm-30nm, for example, it can be 20nm, 22nm, 25nm, 28nm, or 30nm, or any other value within the 20nm-30nm range. The hole blocking layer 60 has a thickness of 6nm-8nm, for example, it can be 6nm, 6.5nm, 7nm, 7.5nm, or 8nm, or any other value within the 6nm-8nm range. The copper electrode layer 70 has a thickness of 100nm-200nm, for example, it can be 100nm, 120nm, 140nm, 160nm, 180nm, or 200nm, or any other value within the 100nm-200nm range. In this embodiment, the thicknesses of the above-mentioned film layers are coordinated to reduce interface defects and carrier recombination losses, and improve the open-circuit voltage, short-circuit current density, and fill factor of the device.

[0049] like Figure 6 As shown, the present invention also provides a narrow bandgap tin-lead perovskite solar cell 100 prepared according to the above-described preparation method. Here, the narrow bandgap tin-lead perovskite solar cell 100 includes, from bottom to top, a glass substrate 10, an ITO transparent conductive layer 20, a PEDOT:PSS hole transport layer 30, a narrow bandgap tin-lead perovskite absorber layer 40, and a C... 60 The solar cell comprises an electron transport layer 50, a hole blocking layer 60, and a copper electrode layer 70. In this embodiment, the functional layers are stacked in the order described above, so that electrons and holes generated by the narrow bandgap tin-lead perovskite absorber layer 40 are transported and collected in opposite directions. Combined with the larger grain size, fewer grain boundaries, and suppressed tin oxidation of the narrow bandgap tin-lead perovskite absorber layer 40, recombination losses during carrier transport are reduced, thereby improving the photoelectric conversion performance and operational stability of the solar cell.

[0050] The technical solution of this application will be further described below with reference to specific embodiments.

[0051] Example 1 This embodiment provides a method for fabricating a narrow bandgap tin-lead perovskite solar cell 100, comprising the following steps: An ITO / glass rigid conductive substrate with a sheet resistance of 15Ω, an average transmittance of more than 80%, and a thickness of 120nm was selected as the substrate material. After the protective film covering the surface was peeled off, it was subjected to ultraviolet ozone treatment for 25 minutes to remove surface organic matter and obtain a clean glass rigid transparent conductive substrate 10. The PEDOT:PSS aqueous dispersion was filtered through a 0.22 μm polytetrafluoroethylene filter membrane. The solution was then spin-coated onto a rigid substrate 10 in two steps. The first spin-coating speed was 500 rpm and the spin-coating time was 2 s. The second spin-coating speed was 6000 rpm and the spin-coating time was 40 s. After spin-coating, the solution was annealed at 150 °C for 20 min to obtain a hole transport layer 30 with a thickness of 40 nm. 2.2 mmol lead iodide, 2.2 mmol stannous iodide, 3.08 mmol formamidine iodide, 1.32 mmol methyl iodide, 5 mmol% stannous fluoride, and 3.5 mmol% lead thiocyanate were dissolved in 2 mL of a 3:1 mixture of DMF and DMSO to obtain FA. 0.7 MA 0.3 Sn 0.5 Pb 0.5 The I3 precursor solution was allowed to stand at room temperature for 6 hours, and then filtered twice through a 0.22 μm polytetrafluoroethylene filter membrane to obtain the perovskite precursor solution. Take 70 μL of perovskite precursor solution and perform two-step spin coating. The first spin coating speed is 1000 rpm and the spin coating time is 10 s. The second spin coating speed is 4000 rpm and the spin coating time is 50 s. In the second spin coating, 600 μL of chlorobenzene antisolvent is added to the rigid substrate at the 30th second.

[0052] The freshly spin-coated perovskite wet film was pre-annealed on a 100°C hot plate for 5 min. Then, 80 μL of 5.5 mg / mL glutamate hydrochloride / isopropanol source solution was dropped onto filter paper. The filter paper was placed next to the perovskite film. The petri dish was inverted and sealed to ensure that both the filter paper and the perovskite film were completely covered by the petri dish. The second annealing treatment was continued for 15 min to form the perovskite film. Ethylenediamium diiodide was dissolved in isopropanol solution to obtain a back passivation solution with a concentration of 1 mg / mL. 70 μL of the back passivation solution was dropped onto the prepared perovskite film, rotated at 4000 rpm for 20 s, and then immediately annealed at 100 °C for 5 min. The annealed product was placed in a hot evaporation chamber at 5 × 10⁻⁶ ℃. -4Under high vacuum, 25nm C atoms were sequentially deposited. 60 Using materials as the electron transport layer 50, evaporating 6nm BCP as the hole blocking layer 60, and evaporating 140nm copper as the metal electrode layer, a narrow bandgap tin-lead perovskite solar cell 100 is obtained.

[0053] Example 2 The narrow bandgap tin-lead perovskite solar cell 100 prepared in Example 1 was used as the bottom sub-cell and stacked with the 1.77eV wide bandgap perovskite top sub-cell to prepare a rigid two-end all-perovskite tandem solar cell.

[0054] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the culture dish and filter paper are removed during the secondary annealing process.

[0055] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the culture dish is retained and the filter paper is removed during the secondary annealing process.

[0056] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that pure IPA solution was added only to filter paper.

[0057] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the pre-annealing time is 0 min.

[0058] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the pre-annealing time is 10 min.

[0059] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the annealing time for the secondary annealing process is 10 minutes.

[0060] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the annealing time for the secondary annealing process is 20 minutes.

[0061] Comparative Example 8 The only difference between Comparative Example 8 and Example 1 is that the volume of the glutamate hydrochloride / isopropanol source solution is 40 μL.

[0062] Comparative Example 9 The only difference between Comparative Example 9 and Example 1 is that the volume of the glutamate hydrochloride / isopropanol source solution is 120 μL.

[0063] Figure 7 This is a current density-voltage curve of the narrow bandgap tin-lead perovskite solar cell obtained in Comparative Example 1 under forward and reverse scanning conditions. Figure 8This is a current density-voltage curve of the narrow bandgap tin-lead perovskite solar cell obtained in Example 1 under forward and reverse scanning conditions. Figure 9 These are the external quantum efficiency curves of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1 and Comparative Example 1. Figure 10 This is a statistical distribution diagram of the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1 and Comparative Example 1. Figure 11 These are scanning electron microscope images of the surface and cross-section of the narrow bandgap tin-lead perovskite absorber layers obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 12 These are X-ray diffraction patterns of the narrow bandgap tin-lead perovskite absorbing layers obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 13 These are X-ray diffraction patterns of the narrow bandgap tin-lead perovskite absorbing layer obtained in Example 1 at different tilt angles. Figure 14 The images show the X-ray diffraction patterns of the narrow bandgap tin-lead perovskite absorbing layer 40 obtained in Comparative Example 1 at different tilt angles. Figure 15 This is a fitted curve of the diffraction angle versus the square of the tilt angle for the narrow bandgap tin-lead perovskite absorber layer 40 obtained in Example 1 and Comparative Example 1. Figure 16 This is the X-ray photoelectron spectroscopy peak fitting diagram of the Sn 3d5 / 2 energy level of the narrow bandgap tin-lead perovskite absorbing layer obtained in Comparative Example 1. Figure 17 This is a fitting diagram of the X-ray photoelectron spectroscopy peaks of the Sn 3d5 / 2 energy level of the narrow bandgap tin-lead perovskite absorber layer obtained in Example 1. Figure 18 This is a graph showing the open-circuit voltage of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1, Comparative Example 1, and Comparative Example 2 as a function of incident light intensity. Figure 19 This is a statistical distribution diagram of the performance parameters of the narrow bandgap tin-lead perovskite solar cells 100 obtained in Example 1, Comparative Example 6, and Comparative Example 7. Figure 20 This is a statistical distribution chart of the performance parameters of the narrow bandgap tin-lead perovskite solar cells obtained in Example 1, Comparative Example 8, and Comparative Example 9. Figure 21 This is the current density-voltage curve of the rigid two-terminal all-perovskite tandem solar cell obtained in Example 2. Figure 22 This is an external quantum efficiency curve of the wide bandgap top sub-cell and the narrow bandgap bottom sub-cell obtained in Example 2.

[0064] Current density-voltage measurement, external quantum efficiency measurement, and device performance parameter statistics were performed on the solar cells obtained in Example 1 and Comparative Examples 1-5. The photoelectric conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, and forward and reverse scanning characteristics of each solar cell were obtained. The test results are shown in Tables 1 and 2. Figures 7-10 As shown.

[0065] Table 1. Performance test results of solar cells prepared in Example 1 and Comparative Examples 1-5

[0066] As shown in Table 1, the solar cell obtained in Example 1 has a photoelectric conversion efficiency of 23.26%, an open-circuit voltage of 0.886V, a fill factor of 80.5%, and a short-circuit current density of 32.63mA / cm². 2 Comparative Example 1, without a petri dish and filter paper, used open-type secondary annealing. Its photoelectric conversion efficiency was 21.70%, open-circuit voltage was 0.872V, fill factor was 78.5%, and short-circuit current density was 31.71 mA / cm². 2 Compared with Comparative Example 1, Example 1 showed an improvement in photoelectric conversion efficiency of 1.56 percentage points, an increase in open-circuit voltage of 14 mV, an increase in fill factor of 2.0 percentage points, and an increase in short-circuit current density of 0.92 mA / cm². 2 The above results indicate that using filter paper loaded with glutamate hydrochloride / isopropanol source solution and performing secondary annealing within a confined annealing space can simultaneously improve the device's voltage output, current output, and carrier transport performance.

[0067] Comparative Example 2, with the culture dish retained but the filter paper removed, achieved a photoelectric conversion efficiency of 22.58%, higher than Comparative Example 1's 21.70%. This indicates that the confined annealing space can extend grain growth time and improve film quality by slowing down the escape rate of DMF and DMSO in the perovskite wet film. However, the photoelectric conversion efficiency, open-circuit voltage, and fill factor of Comparative Example 2 are still lower than those of Example 1, indicating that simply restricting solvent escape is insufficient to achieve the device performance of Example 1.

[0068] Comparative Example 3, which only had isopropanol added to the filter paper, showed a photoelectric conversion efficiency of 22.42% and an open-circuit voltage of 0.874V, both lower than those of Example 1. Since both Comparative Example 3 and Example 1 used petri dishes and filter paper, the main difference being the presence or absence of glutamate hydrochloride on the filter paper, this result indicates that the performance improvement in Example 1 was not solely due to isopropanol volatilization or confined space; the glutamate hydrochloride-derived species participated in the crystallization regulation, tin oxidation inhibition, and defect passivation processes of the perovskite film.

[0069] Comparative Example 4, without pre-annealing, has a photoelectric conversion efficiency of 21.30%, an open-circuit voltage of 0.870V, a fill factor of 78.5%, and a short-circuit current density of 31.19mA / cm². 2 The values ​​were all lower than in Example 1. Without pre-annealing, the perovskite wet film contained more DMF and DMSO, and the film layer had not yet formed a stable initial crystalline phase and structural framework. When annealing continued in a confined space, film flow, uneven nucleation distribution, or local component migration were likely to occur.

[0070] Comparative Example 5, with a pre-annealing time of 10 min, achieved a photoelectric conversion efficiency of 22.62%, lower than that of Example 1, which had a pre-annealing time of 5 min. When the pre-annealing time is too long, the perovskite film undergoes significant crystallization before entering the confined annealing space, reducing the residual solvent content and limiting the space for further grain growth through solvent-mediated ion migration. Example 1, using a 5-min pre-annealing, allows the film to form a preliminary crystalline phase while retaining a suitable amount of residual solvent, thus balancing film structural stability with the requirements for subsequent grain growth.

[0071] Table 2. Performance test results of solar cells prepared in Example 1 and Comparative Example 1

[0072] From Table 2 and in combination Figure 7 and Figure 8 It can be seen that the photoelectric conversion efficiency, open-circuit voltage, fill factor, and short-circuit current density of the solar cell obtained in Comparative Example 1 under reverse scanning conditions are 21.70%, 0.872V, 78.5%, and 31.71mA / cm², respectively. 2 Under forward scanning conditions, the values ​​were 21.27%, 0.868V, 77.3%, and 31.67mA / cm, respectively. 2 The parameters of the solar cell obtained in Example 1 under reverse scanning conditions were 23.26%, 0.886V, 80.5%, and 32.63mA / cm, respectively. 2 Under forward scanning conditions, the values ​​were 22.65%, 0.882V, 79.5%, and 32.30mA / cm, respectively. 2 The forward and reverse scan curves of Comparative Example 1 and Example 1 are quite similar, and the differences in various performance parameters under the two scanning methods are small, indicating that the obtained devices do not exhibit significant scan hysteresis. Meanwhile, Example 1 shows higher photoelectric conversion efficiency, open-circuit voltage, fill factor, and short-circuit current density under both forward and reverse scan conditions than Comparative Example 1. This indicates that the combination of confined space secondary annealing and glutamate hydrochloride-derived treatment species can improve the carrier generation, transport, and collection performance of the device, and maintain these performance improvements under different scan directions.

[0073] like Figure 9 As shown, the external quantum efficiency of Example 1 is generally higher than that of Comparative Example 1 in the wavelength range of approximately 500 nm to 900 nm. Based on the short-circuit current density obtained by integrating the external quantum efficiency curve, Example 1 has a short-circuit current density of 32.61 mA / cm². 2 Comparative Example 1 has an efficiency of 32.11 mA / cm². 2This result shows the same trend as the short-circuit current density obtained from the current density-voltage test. The high external quantum efficiency of Example 1 indicates that, with a reduction in the number of grain boundaries and defects, photogenerated carriers generated in the perovskite absorber layer can be transported to the corresponding transport layer with lower recombination losses.

[0074] like Figure 10 As shown, the box-shaped distributions of open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of multiple devices in Example 1 are all higher than those in Comparative Example 1, and the test data of each parameter are concentrated in a relatively stable range.

[0075] The narrow bandgap tin-lead perovskite absorber layers 40 obtained in Examples 1, 1, and 2 were subjected to surface and cross-sectional scanning electron microscopy, X-ray diffraction, and X-ray diffraction at different tilt angles. The results showed that the microstructure, crystal orientation, and diffraction peak positions of each perovskite absorber layer varied with the tilt angle. Figures 11-15 As shown.

[0076] like Figure 11 As shown, the perovskite film surface of Comparative Example 1 consists of numerous small and unevenly distributed grains, with pores and discontinuous regions in the cross-section; the grain size of Comparative Example 2 is increased, and the film density is correspondingly improved; the grain size of Example 1 is further increased, the number of grain boundaries is reduced, and the grain continuity and film density in the cross-sectional direction are improved. These results indicate that the confined annealing space can promote continued grain growth by slowing the escape of DMF and DMSO, and the glutamate hydrochloride-derived treatment species can further regulate the grain boundary state, thereby forming a perovskite absorber layer with larger grain size and fewer pores.

[0077] like Figure 12 As shown, Example 1, Comparative Example 1, and Comparative Example 2 all exhibit characteristic diffraction peaks of the perovskite material's crystal planes (100), (110), (111), (200), (210), (220), and (300) at similar diffraction angle positions, indicating that the three annealing conditions did not change the main crystal phase of the perovskite absorber layer. The intensity of the main characteristic diffraction peak in Example 1 is higher than that in Comparative Example 1 and Comparative Example 2, indicating that the perovskite absorber layer obtained in Example 1 has a higher degree of crystallinity and more sufficient grain growth.

[0078] like Figure 13 and Figure 14 As shown, as the tilt angle ψ increases from 5° to 45°, the position of the diffraction peak corresponding to Example 1 changes little, while the position of the diffraction peak corresponding to Comparative Example 1 changes much more with the tilt angle.

[0079] like Figure 15 As shown, in Example 1, 2θ and sin 2The absolute value of the slope of the ψ-fit curve is less than that of Comparative Example 1, indicating that the interplanar spacing of the perovskite absorber layer obtained in Example 1 changes less with the test direction, and the residual lattice strain in the film is reduced. Lower residual lattice strain is beneficial for reducing strain-induced defect formation and maintaining the stability of the tin-lead perovskite lattice structure. The results show that the confined annealing space, combined with glutamate hydrochloride-derived treatment species, can regulate the crystal growth process of the perovskite film and reduce residual lattice strain, thereby forming a narrow-bandgap tin-lead perovskite absorber layer 40 with larger grain size, fewer grain boundaries and pores, and a higher degree of crystallinity.

[0080] Next, X-ray photoelectron spectroscopy was performed on the narrow bandgap tin-lead perovskite absorber layer 40 obtained in Example 1 and Comparative Example 1, and the open-circuit voltage of the solar cells obtained in Example 1, Comparative Example 1, and Comparative Example 2 under different incident light intensities was measured to obtain Sn 2+ and Sn 4+ The test results of relative content and open-circuit voltage as a function of incident light intensity, such as Figures 16-18 As shown.

[0081] like Figure 16 As shown, Sn in Comparative Example 1 2+ The relative content is 68.53%, Sn 4+ The relative content is 31.47%.

[0082] like Figure 17 As shown, Sn in Example 1 2+ The relative content increased to 84.58%, Sn 4+ The relative content decreased to 15.42%. Compared with Comparative Example 1, the Sn content in Example 1... 4+ The relative content decreased by 16.05 percentage points, indicating that the glutamate hydrochloride-derived species could reduce Sn content during secondary annealing. 2+ To Sn 4+ Oxidation of Sn. 4+ Reducing the content can decrease self-doping and defect states caused by tin oxidation, thereby improving the carrier transport performance of the perovskite absorber layer.

[0083] like Figure 18 As shown, the fitting slopes of the open-circuit voltage as a function of incident light intensity for Comparative Example 1, Comparative Example 2, and Example 1 are 1.43 kT / q, 1.34 kT / q, and 1.25 kT / q, respectively. The fitting slope of Comparative Example 2 is lower than that of Comparative Example 1, indicating that the confined annealing space reduces some trap-assisted recombination by improving the crystallization process. The fitting slope of Example 1 is further reduced, indicating that the passivation of surface and grain boundary defects by glutamate hydrochloride-derived treatment species further reduces trap-assisted non-radiative recombination. This change corresponds to the increase in open-circuit voltage and fill factor in Example 1.

[0084] Furthermore, the photoelectric performance of the solar cells obtained in Example 1, Comparative Example 6, and Comparative Example 7, as well as the solar cells obtained in Example 1, Comparative Example 8, and Comparative Example 9, was tested. The statistical distribution results of the device performance parameters under different secondary annealing times and different amounts of source solution were obtained, as follows: Figure 19 and Figure 20 As shown.

[0085] like Figure 19 As shown, Example 1, with a secondary annealing time of 15 min, outperformed Comparative Example 6 (with a secondary annealing time of 10 min) and Comparative Example 7 (with a secondary annealing time of 20 min) in terms of open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency. The statistical values ​​of photoelectric conversion efficiency were mainly distributed between approximately 22.6% and 23.2%. When the secondary annealing time was 10 min, the continued growth of grains and the passivation of film defects by glutamate-derived treatment species may not have been sufficient. When the secondary annealing time was extended to 20 min, the performance parameters decreased significantly, possibly due to excessive escape of volatile components from the perovskite film or excessive accumulation of treatment species on the film surface. Therefore, appropriately controlling the secondary annealing time is beneficial for balancing grain growth, defect passivation, and film composition stability. The solar cell obtained under the 15 min condition exhibited superior overall photoelectric performance.

[0086] like Figure 20 As shown, Example 1, with a source solution volume of 80 μL, exhibits higher open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency, and the distribution of various performance parameters is relatively concentrated. Comparative Example 8, with a source solution volume of 40 μL, shows lower performance parameters than Example 1, indicating that a smaller source solution volume may result in insufficient supply of processed species within the confined annealing space, making it difficult to adequately promote grain growth and passivate film defects. Comparative Example 9, with a source solution volume of 120 μL, also shows lower performance parameters than Example 1, and its short-circuit current density, fill factor, and photoelectric conversion efficiency exhibit greater dispersion, indicating that excessive source solution volume may lead to excessively high or unevenly distributed processed species concentrations, which is detrimental to device performance improvement and repeatability. Therefore, controlling the source solution volume within a suitable range allows the supply of processed species to match the confined annealing space and the secondary annealing process, with the solar cell obtained under the 80 μL condition exhibiting superior and more stable photoelectric performance.

[0087] Finally, the rigid two-terminal all-perovskite tandem solar cell obtained in Example 2 was subjected to current density-voltage tests, and the external quantum efficiency of the wide-bandgap top sub-cell and the narrow-bandgap bottom sub-cell were tested respectively. The photoelectric performance of the tandem solar cell and the spectral response and integrated short-circuit current density of the two sub-cells were obtained. The test results are shown in Table 3. Figure 21 and Figure 22 As shown.

[0088] Table 3. Performance test results of the all-perovskite tandem solar cells prepared in Example 2

[0089] From Table 3 and Figure 21 It can be seen that, by using the narrow bandgap tin-lead perovskite solar cell 100 obtained in Example 1 as the bottom sub-cell, and integrating it with a wide bandgap perovskite top sub-cell with a bandgap of 1.77 eV, the resulting rigid two-terminal all-perovskite tandem solar cell has a photoelectric conversion efficiency of 29.68%, an open-circuit voltage of 2.178 V, a fill factor of 86.2%, and a short-circuit current density of 15.81 mA / cm². 2 The above results demonstrate that the narrow bandgap tin-lead perovskite solar cell 100 obtained in Example 1 can be used as the bottom sub-cell of an all-perovskite tandem solar cell.

[0090] like Figure 22 As shown, the wide-bandgap top sub-cell and the narrow-bandgap bottom sub-cell absorb short-wavelength and long-wavelength incident light, respectively, forming complementary spectral responses. Based on the short-circuit current density obtained by integrating the external quantum efficiency curve, the wide-bandgap top sub-cell has a current density of 15.62 mA / cm². 2 The narrow bandgap bottom sub-cell has an A / cm value of 15.41 mA / cm. 2 The difference between the two is 0.21 mA / cm. 2 This indicates that the two sub-cells have a good current matching relationship, which is beneficial to reducing the current mismatch loss in the stacked structure at both ends.

[0091] In summary, this application, through a combination of pre-annealing, non-contact liquid supply, and confined space secondary annealing, slows down the escape rate of N,N-dimethylformamide and dimethyl sulfoxide in the perovskite wet film, extends the crystal growth window, and allows small grains to transform into large grains through Ostwald ripening. Simultaneously, it facilitates the migration of chlorine- and carboxyl-containing treated species derived from glutamate hydrochloride from the film surface to the interior, thereby inhibiting the growth of Sn. 2+ Oxidation and passivation of surface and grain boundary defects result in a narrow-bandgap tin-lead perovskite absorber layer 40 with larger grain size, fewer grain boundaries and pores, higher crystallinity, and lower residual lattice strain. This reduces trap-assisted nonradiative recombination, improves carrier generation, transport, and collection performance, and enables the resulting single-junction solar cell to achieve a photoelectric conversion efficiency of 23.26%. Furthermore, it enables the all-perovskite tandem solar cell using this solar cell as the bottom sub-cell to achieve a photoelectric conversion efficiency of 29.68%.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a narrow bandgap tin-lead perovskite absorber layer, characterized in that, Includes the following steps: Glutamate hydrochloride was dissolved in isopropanol to obtain a glutamate hydrochloride / isopropanol source solution; A narrow bandgap tin-lead perovskite wet film is formed on the hole transport layer, wherein the material of the narrow bandgap tin-lead perovskite wet film is FA. 0.7 MA 0.3 Sn 0.5 Pb 0.5 I3; The narrow bandgap tin-lead perovskite wet film is placed on a heated bearing surface for pre-annealing treatment to obtain a pre-annealed perovskite film. A 60 μL-100 μL solution of the glutamate hydrochloride / isopropanol source is applied to the liquid-absorbing carrier, and the liquid-absorbing carrier and the pre-annealed perovskite film are disposed alternately on the heating support surface. An open cover is placed over the liquid-absorbing carrier and the pre-annealed perovskite film, and the opening edge of the cover is supported on the heating support surface, so that the cover and the heating support surface enclose a confined annealing space that restricts the outward escape of gaseous components. The pre-annealed perovskite film is subjected to a second annealing treatment for 12-18 minutes within the confined annealing space, so that the gas phase components released from the glutamate hydrochloride / isopropanol source solution come into contact with the pre-annealed perovskite film, while the glutamate hydrochloride / isopropanol source solution does not directly contact the pre-annealed perovskite film, thus obtaining the narrow bandgap tin-lead perovskite absorber layer.

2. The method for preparing a narrow bandgap tin-lead perovskite absorber layer according to claim 1, characterized in that, The pre-annealing time is any value between 2 min and 8 min.

3. The method for preparing a narrow bandgap tin-lead perovskite absorber layer according to claim 1, characterized in that, The concentration of the glutamate hydrochloride / isopropanol source solution is any value between 5 mg / mL and 6 mg / mL.

4. The method for preparing a narrow bandgap tin-lead perovskite absorber layer according to claim 1, characterized in that, Following the secondary annealing process within the confined annealing space, the process further includes: An isopropanol solution of ethylenediammonium diiodide was spin-coated onto the surface of the annealed perovskite film, followed by surface passivation annealing. The concentration of the isopropanol solution of the ethylenediamine diiodide is any value between 0.5 mg / mL and 1.5 mg / mL.

5. The method for preparing a narrow bandgap tin-lead perovskite absorber layer according to any one of claims 1-4, characterized in that, The perovskite precursor solution used to form the narrow bandgap tin-lead perovskite wet film includes PbI2, SnI2, FAI and MAI, and the solvent of the perovskite precursor solution is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide.

6. The method for preparing a narrow bandgap tin-lead perovskite absorber layer according to claim 1, characterized in that, The narrow bandgap tin-lead perovskite wet film is formed by a two-step spin coating method, which includes: The first spin coating step is performed at the first rotation speed for the first preset time. The second spin coating is performed at the second rotation speed for the second preset time, and 500μL-700μL of chlorobenzene is added as an anti-solvent during the 28s-32s of the second spin coating.

7. A method for fabricating a narrow bandgap tin-lead perovskite solar cell, characterized in that, Includes the following steps: A PEDOT:PSS hole transport layer is formed on an ITO / glass transparent conductive substrate; A narrow bandgap tin-lead perovskite absorber layer is formed on the PEDOT:PSS hole transport layer using the preparation method described in any one of claims 1-6. C is sequentially formed on the narrow bandgap tin-lead perovskite absorber layer 60 The narrow bandgap tin-lead perovskite solar cell is prepared by comprising an electron transport layer, a hole blocking layer, and a copper electrode layer.

8. The method for fabricating a narrow bandgap tin-lead perovskite solar cell according to claim 7, characterized in that, The thickness of the PEDOT:PSS hole transport layer is 30nm-50nm, the thickness of the narrow bandgap tin-lead perovskite absorber layer is 1000nm-1200nm, and the C... 60 The electron transport layer has a thickness of 20nm-30nm, the hole blocking layer has a thickness of 6nm-8nm, and the copper electrode layer has a thickness of 100nm-200nm.

9. A narrow bandgap tin-lead perovskite solar cell prepared by the method according to any one of claims 7-8.

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