Flexible tin-lead perovskite solar cells based on regulation of hole transport layer interface by rhodamine b and preparation method thereof

Abstract

The present application relates to the technical field of flexible perovskite solar cell, and discloses a flexible tin-lead perovskite solar cell based on luring red regulation of hole transport layer interface and a preparation method thereof.The cell comprises a transparent flexible conductive substrate, a hole transport layer, a luring red interface modification layer, a tin-lead mixed narrow-bandgap perovskite light absorption layer, an electron transport layer, a buffer layer and a metal electrode layer which are sequentially stacked; the luring red interface modification layer is formed by spin coating a luring red aqueous solution on the surface of the hole transport layer and then heat treatment.The sulfonate group in the luring red molecule is conducive to adjusting the interface potential and energy level matching, the azo group and phenolic hydroxyl group can passivate buried interface defects, reduce non-radiative recombination, and improve the wet spreading and film uniformity of the precursor solution, thereby improving the photoelectric conversion efficiency, moisture resistance and cycle bending stability of the device.

Description

Technical Field

[0001] This invention relates to the field of flexible perovskite solar cell technology, and in particular to a flexible tin-lead perovskite solar cell based on allura red modulation of the hole transport layer interface and its fabrication method. Background Technology

[0002] Flexible perovskite solar cells typically use polymer films such as PEN and PET, along with transparent conductive layers like ITO on their surface, as substrates. They are characterized by their light weight, thinness, flexibility, ability to be bonded to curved surfaces, and suitability for roll-to-roll continuous processing, making them promising for applications in portable power supply, wearable electronics, and curved photovoltaics. Tin-lead hybrid narrow-bandgap perovskite solar cells are a key component in constructing all-perovskite tandem solar cells. Their narrow bandgap characteristics can expand the absorption range of the solar spectrum and help improve the theoretical photoelectric conversion efficiency of the tandem cell. Therefore, combining tin-lead hybrid narrow-bandgap perovskite with a transparent flexible conductive substrate holds promise for achieving a balance between high photoelectric conversion efficiency and lightweight, flexible characteristics.

[0003] However, compared to rigid glass substrates, flexible polymer substrates have lower heat resistance temperatures, and the devices are subjected to alternating tensile and compressive stresses during bending, making them more sensitive to low-temperature film formation, interlayer adhesion, film uniformity, and control of buried interface defects. Microscopic undulations on the surface of flexible substrates and transparent conductive layers can easily cause localized thickness unevenness in the upper functional film, leading to stress concentration during repeated bending. This can induce cracks, interface delamination, damage to conductive channels, or increased carrier recombination, affecting the photovoltaic performance, fabrication repeatability, and mechanical stability of flexible devices.

[0004] Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) possesses advantages such as high visible light transmittance, good low-temperature solution processing and film formation properties, suitable hole transport performance, and low-cost spin-coating preparation, making it suitable as a hole transport layer on transparent flexible conductive substrates such as PEN / ITO. However, PEDOT:PSS still presents the following problems when used in tin-lead mixed narrow bandgap perovskite flexible devices: First, the PSS component has strong acidity and hygroscopicity, which may corrode the transparent conductive layer and induce hydrolysis and ion migration at the buried interface; Second, the work function of PEDOT:PSS is typically 5.0–5.2 eV, which is mismatched with the deeper valence band top level of tin-lead mixed narrow bandgap perovskites, potentially forming a hole extraction barrier and exacerbating nonradiative recombination; Third, the uneven surface roughness and surface energy distribution of PEDOT:PSS can reduce the spreading and coverage uniformity of the perovskite precursor solution on the flexible substrate, forming grain boundary defects and potential stress concentration points. In addition, Sn in tin-lead perovskite 2+ Easily oxidized to Sn 4+ , generating defective states and pSelf-doping further affects the carrier transport and stability of flexible devices.

[0005] Therefore, for flexible tin-lead perovskite solar cells, there is an urgent need to develop an ultrathin interface treatment material that is compatible with polymer flexible substrates and low-temperature solution processes. This material should achieve interface energy level adjustment, defect passivation, wettability improvement, and interface corrosion mitigation without significantly increasing device rigidity and optical loss, thereby balancing the photovoltaic performance, moisture resistance, and cyclic bending stability of flexible devices. Summary of the Invention

[0006] In view of this, the present invention proposes a flexible tin-lead perovskite solar cell based on the interface of the hole transport layer regulated by the allure red and its preparation method, so as to solve the problem of interface characteristics of tin-lead mixed perovskite solar cells, thereby improving the photovoltaic performance of the device and improving its moisture resistance and cyclic bending stability.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a flexible tin-lead perovskite solar cell, comprising a conductive substrate, a hole transport layer, an Allura Red interface modification layer, a tin-lead mixed narrow bandgap perovskite light absorption layer, an electron transport layer, a buffer layer, and a metal electrode layer stacked sequentially; the formation of the Allura Red interface modification layer includes the step of spin-coating an Allura Red aqueous solution onto the surface of the hole transport layer.

[0008] Preferably, the mass concentration of the allura red aqueous solution is 0.2–2.0 mg / mL.

[0009] More preferably, the mass concentration of the Allura Red aqueous solution is 0.5–1.0 mg / mL; even more preferably, the mass concentration of the Allura Red aqueous solution is 1.0 mg / mL.

[0010] Preferably, the spin coating speed of the allure red aqueous solution is 3000-6000 rpm, and the spin coating time is 20-40 s.

[0011] More preferably, the spin coating speed is 4000 rpm and the spin coating time is 30 s.

[0012] Preferably, the conductive substrate is a transparent flexible conductive substrate; the raw material of the hole transport layer includes PEDOT:PSS; the raw material of the tin-lead mixed narrow bandgap perovskite light absorption layer includes materials with the chemical formula A(Sn) x Pb 1-x B3 is a perovskite material, where A is selected from FA. + MA + 、Rb + and Cs + One or more of them, B is selected from Cl -,Br - and I - One or more of them, 0 < x <1; The electron transport layer includes C 60 The buffer layer includes a BCP.

[0013] More preferably, the transparent flexible conductive substrate is a PEN / ITO transparent flexible conductive substrate; x =0.5, the chemical formula of the tin-lead mixed narrow bandgap perovskite light-absorbing layer is FA. 0.75 Cs 0.25 Pb 0.5 Sn 0.5 I3; The metal electrode layer is an Ag electrode layer.

[0014] Preferably, the hole transport layer has a thickness of 20–50 nm; the tin-lead mixed narrow bandgap perovskite light absorption layer has a thickness of 500–1000 nm; the electron transport layer has a thickness of 25–35 nm; the buffer layer has a thickness of 5–10 nm; and the metal electrode layer has a thickness of 100–120 nm.

[0015] More preferably, the hole transport layer has a thickness of 30 nm; the tin-lead mixed narrow bandgap perovskite light absorption layer has a thickness of 800 nm; the electron transport layer has a thickness of 25 nm; the buffer layer has a thickness of 7 nm; and the metal electrode layer has a thickness of 100 nm.

[0016] Secondly, the present invention provides a method for fabricating a flexible tin-lead perovskite solar cell as described above, comprising the following steps: S1, a hole transport layer is spin-coated onto a conductive substrate and then subjected to thermal annealing. S2, Allura Red aqueous solution is spin-coated onto the surface of the hole transport layer and then heat-treated to form an Allura Red interface modification layer; S3, a tin-lead mixed narrow bandgap perovskite precursor solution is spin-coated onto the alluring red interface modification layer, and an anti-solvent is added dropwise during the spin-coating process. Then, a tin-lead mixed narrow bandgap perovskite light-absorbing layer is formed by thermal annealing. S4. An electron transport layer, a buffer layer, and a metal electrode layer are sequentially vacuum-deposited onto a tin-lead mixed narrow bandgap perovskite light-absorbing layer to obtain a flexible tin-lead perovskite solar cell.

[0017] Based on the above technical solutions, preferably, in step S1, the transparent flexible conductive substrate is pre-cleaned and treated with ultraviolet ozone.

[0018] More preferably, the ultraviolet ozone treatment time is 15 to 40 minutes; even more preferably, the ultraviolet ozone treatment time is 30 minutes.

[0019] Based on the above technical solutions, preferably, in step S1, the spin coating speed is 3000-5000 rpm and the spin coating time is 20-60 s; the heat annealing temperature is 120-150 ℃ and the heat annealing time is 10-30 min.

[0020] More preferably, in step S1, the spin coating speed is 4000 rpm and the spin coating time is 40 s; the heat annealing temperature is 130 ℃ and the heat annealing time is 20 min.

[0021] Based on the above technical solution, preferably, in step S2, the heat treatment temperature is 80-110 ℃ and the heat treatment time is 5-15 min.

[0022] More preferably, in step S2, the heat treatment temperature is 100 ℃ and the heat treatment time is 10 min.

[0023] Based on the above technical solution, preferably, in step S3, the preparation method of the perovskite precursor solution includes: mixing raw materials such as CsI, FAI, SnI2, PbI2 and SnF2 in a solvent, and obtaining the perovskite precursor solution after filtration through a filter membrane; the solvent is... N,N - A mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), with a volume ratio of DMF to DMSO of (2-4):1.

[0024] Based on the above technical solution, preferably, in step S3, the concentration of the perovskite precursor solution is 1.8–2.4 mol / L; the antisolvent is selected from one or more of chlorobenzene, diethyl ether, acetone, toluene, ethyl acetate, and chloroform; the thermal annealing temperature is 80–120 °C, and the thermal annealing time is 10–30 min.

[0025] More preferably, the concentration of the tin-lead mixed narrow bandgap perovskite precursor solution is 2.0 mol / L, the antisolvent is chlorobenzene, and the thermal annealing temperature is 120 ℃ for 20 min.

[0026] Based on the above technical solution, and further preferably, in step S3, the spin coating includes two spin coating steps: the first spin coating is spin coating at 500-2000 rpm for 10-30 s; the second spin coating is spin coating at 3000-5000 rpm for 50-80 s; the antisolvent is added dropwise 20-40 s before the end of the second spin coating step.

[0027] More preferably, in step S3, the spin coating includes two spin coating steps: the first spin coating is spin coating at 1000 rpm for 20 s; the second spin coating is spin coating at 5000 rpm for 60 s; the antisolvent is added dropwise 30 s before the end of the second spin coating step.

[0028] Based on the above technical solution, preferably, in step S4, the vacuum degree of vacuum evaporation is 4×10⁻⁶. -4 ~9×10 -4 Pa, deposition rate is 0.1–0.5 Å / s.

[0029] More preferably, in step S4, the vacuum degree of vacuum evaporation is 4 × 10⁻⁶. -4 Pa, deposition rate is 0.1 Å / s.

[0030] The flexible tin-lead-perovskite solar cell based on allura red modulation of the hole transport layer interface and its fabrication method of the present invention have the following advantages over the prior art: 1. Improved interface potential and energy level matching: Allura Red molecules contain polar sulfonate groups, which, after forming an interface modification layer, help to adjust the local potential and energy level matching of the hole transport layer / perovskite interface, reduce the hole extraction barrier and transport loss, thereby helping to improve the device's fill factor.

[0031] 2. Coordination and Interfacial Defect Passivation: The azo and phenolic hydroxyl groups in the Allura Red molecule can provide Lewis basic coordination sites, which can interact with uncoordinated Sn on the perovskite surface. 2+ and Pb 2+ The interaction reduces buried interface defects and nonradiative recombination, which helps to improve the open-circuit voltage of the device.

[0032] 3. Improved interface wettability and film quality: Allura Red modification reduces the contact angle of the perovskite precursor solution on the hole transport layer surface, which is beneficial for the uniform spreading of the precursor solution and the growth of perovskite grains. At the same time, the water contact angle of the modified perovskite film increases, which helps to slow down water vapor intrusion, thereby improving the device's moisture resistance and providing favorable conditions for improving environmental stability.

[0033] 4. Improved adaptability and mechanical stability of flexible devices: The Allure Red interface modification layer is formed by aqueous spin coating and mild heat treatment, and the process is compatible with transparent flexible conductive substrates such as PEN / ITO. Its ultra-thin interface control method does not introduce an additional rigid support layer, and by improving the uniformity of the film layer and reducing grain boundary and buried interface defects, it reduces the risk of local stress concentration and crack propagation in flexible multilayer structures, thereby improving the cyclic bending stability of the device. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention are briefly described below. Except... Figure 2 Besides the Allura Red molecular structure diagram shown, the device structure, thin film characterization, spectroscopic testing, photovoltaic performance, and bending stability testing of this invention all revolve around flexible tin-lead perovskite solar cells on a PEN / ITO transparent flexible conductive substrate. Obviously, the accompanying drawings described below are only some embodiments of this invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the flexible tin-lead perovskite solar cell structure of the present invention. The curved layered structure is used to characterize the flexible device morphology composed of the PEN / ITO flexible substrate and its functional layers. The allure red interface modification layer is located between the hole transport layer and the tin-lead mixed narrow bandgap perovskite light absorption layer. Because it is an ultrathin interface layer, it is not separately labeled according to the actual thickness ratio in the figure. Figure 2 This is a structural diagram of the alluring red molecule of the present invention; Figure 3 The UV-Vis absorption spectra of the perovskite films of Comparative Example 1 (Control) and Example 1 (Target) prepared on PEN / ITO flexible substrates according to the present invention are shown. Figure 4 The images show the contact angle test results of perovskite precursor solution before and after the application of alluring red treatment to the hole transport layer on a PEN / ITO flexible substrate / PEDOT:PSS substrate. Figures (a) and (b) show the results before and after the treatment, respectively. Figure 5 The images show the water contact angle test results of the perovskite films prepared on the PEN / ITO flexible substrate in Comparative Example 1 and Example 1, respectively. (a) and (b) represent Comparative Example 1 and Example 1, respectively. Figure 6 These are time-resolved photoluminescence (TRPL) images of the flexible comparative example 1 (Control) and flexible example 1 (Target) perovskite thin films of the present invention; Figure 7 This is a comparison of steady-state photoluminescence (PL) of the perovskite thin films of the flexible comparative example 1 (Control) and the flexible example 1 (Target) of the present invention; Figure 8 The images show a comparison of scanning electron microscope (SEM) images of the perovskite films prepared on PEN / ITO flexible substrates in Comparative Example 1 and Example 1, respectively. (a) and (b) represent Comparative Example 1 and Example 1, respectively. Figure 9The graphs show the photoelectric conversion efficiency and fill factor distribution of the flexible comparative example 1 (Control) and flexible example 1 (Target) tin-lead hybrid narrow bandgap perovskite solar cells of the present invention. Figure 10 The diagram shows the open-circuit voltage and short-circuit current density distribution of the tin-lead hybrid narrow bandgap perovskite solar cells of the flexible comparative example 1 (Control) and flexible example 1 (Target) of the present invention. Figure 11 The graph shows the photoelectric conversion efficiency distribution of the flexible perovskite solar cells prepared on PEN / ITO flexible substrates of Comparative Example 1 (0 mg / mL), Example 4 (0.2 mg / mL), Example 5 (0.5 mg / mL), Example 1 (1.0 mg / mL), Example 6 (1.5 mg / mL), Example 7 (2.0 mg / mL), and Comparative Example 2 (3.0 mg / mL).

[0036] Figure 12 This is a graph showing the normalized photoelectric conversion efficiency changes of the flexible comparative example 1 (Control) and flexible example 1 (Target) perovskite solar cells during cyclic bending. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] The cesium iodide (CsI, 99.99%), formamidine iodide (FAI, 99.5%), and C used in this invention 60 99% and BCP (99.5%) were purchased from Xi'an Yulu Solar Energy; lead iodide (PbI2, 99.99%) was purchased from TCI; stannous iodide (SnI2, 99.99%) was purchased from a commercial supplier; Allura Red (98%) was purchased from Aladdin; other chemical reagents not separately specified were purchased from Sigma-Aldrich. Unless otherwise stated, all reagents were used directly without further purification.

[0039] Example 1 (1) Clean the PEN / ITO flexible substrate with cleaning agent, isopropanol and deionized water for 15 min each, then dry it with nitrogen; then place the substrate in an ultraviolet ozone environment for about 30 min.

[0040] (2) PEDOT:PSS was spin-coated on the treated substrate at a speed of 4000 rpm for 40 s, and then annealed at 130 ℃ for 20 min to obtain the hole transport layer.

[0041] (3) Prepare a 1.0 mg / mL Allura Red aqueous solution and spin-coat it onto the substrate with hole transport layer obtained in step (2) at a speed of 4000 rpm for 30 s. Then anneal at 100 °C for 10 min.

[0042] (4) Transfer the substrate obtained in the previous step to a nitrogen glove box and spin-coat the perovskite precursor solution. The perovskite composition corresponding to the precursor solution is FA. 0.75 Cs 0.25 Pb 0.5 Sn 0.5 The precursor solution, containing 2.0 mol / L I3 and a DMF to DMSO volume ratio of 4:1, was filtered through a 0.22 μm PTFE membrane before use. The precursor solution was first spin-coated onto the substrate at 1000 rpm for 20 s, then at 5000 rpm for 60 s, with 250 μL of chlorobenzene anti-solvent added dropwise 30 s before the end of the second spin-coating step. After spin-coating, the film was annealed at 120 °C for 20 min under a nitrogen atmosphere to obtain a tin-lead mixed narrow bandgap perovskite film.

[0043] (5) Transfer the thin film to the vapor deposition apparatus and deposit it under a vacuum of 4×10⁻⁶. -4 Under conditions of Pa and a deposition rate of 0.1 Å / s, 25 nm thick C layers were sequentially deposited. 60 A complete flexible tin-lead perovskite solar cell was obtained by combining a 7 nm thick BCP layer and a 100 nm thick silver electrode.

[0044] Example 2 (1) Clean the PEN / ITO flexible substrate with cleaning agent, isopropanol and deionized water for 15 min each, then dry it with nitrogen; then place the substrate in an ultraviolet ozone environment for about 15 min.

[0045] (2) PEDOT:PSS was spin-coated on the treated substrate at a speed of 3000 rpm for 60 s, and then annealed at 120 ℃ for 10 min to obtain the hole transport layer.

[0046] (3) Prepare a 0.2 mg / mL Allura Red aqueous solution and spin-coat it onto the substrate with hole transport layer obtained in step (2) at a speed of 3000 rpm for 40 s. Then anneal at 80 °C for 5 min.

[0047] (4) Transfer the substrate obtained in the previous step to a nitrogen glove box and spin-coat the perovskite precursor solution. The perovskite composition corresponding to the precursor solution is FA. 0.75 Cs 0.25 Pb 0.5 Sn 0.5 The precursor solution, prepared with I3 at a concentration of 1.8 mol / L and a DMF to DMSO volume ratio of 2:1, was filtered through a 0.22 μm PTFE membrane before use. The precursor solution was first spin-coated onto the substrate at 500 rpm for 30 s, then at 3000 rpm for 80 s. 250 μL of chlorobenzene anti-solvent was added dropwise 20 s before the end of the second spin-coating step. After spin-coating, the substrate was annealed at 80 °C for 10 min under a nitrogen atmosphere to obtain a tin-lead mixed narrow bandgap perovskite film.

[0048] (5) Transfer the thin film to the vapor deposition apparatus and deposit it under a vacuum of 4×10⁻⁶. -4 Under conditions of Pa and a deposition rate of 0.1 Å / s, 25 nm thick C layers were sequentially deposited. 60 A complete flexible tin-lead perovskite solar cell was obtained by combining a 5 nm thick BCP layer and a 100 nm thick silver electrode.

[0049] Example 3 (1) Clean the PEN / ITO flexible substrate with cleaning agent, isopropanol and deionized water for 15 min each, then dry it with nitrogen; then place the substrate in an ultraviolet ozone environment for about 40 min.

[0050] (2) PEDOT:PSS was spin-coated on the treated substrate at a speed of 5000 rpm for 20 s, and then annealed at 150 ℃ for 30 min to obtain the hole transport layer.

[0051] (3) Prepare a 2.0 mg / mL Allura Red aqueous solution and spin-coat it onto the substrate with hole transport layer obtained in step (2) at a speed of 6000 rpm for 20 s. Then anneal at 110 °C for 15 min.

[0052] (4) Transfer the substrate obtained in the previous step to a nitrogen glove box and spin-coat the perovskite precursor solution. The perovskite composition corresponding to the precursor solution is FA. 0.75 Cs 0.25 Pb 0.5 Sn 0.5The precursor solution, containing 2.4 mol / L I3 and a DMF to DMSO volume ratio of 4:1, was filtered through a 0.22 μm PTFE membrane before use. The precursor solution was first spin-coated onto the substrate at 2000 rpm for 10 s, then at 5000 rpm for 50 s. 250 μL of chlorobenzene anti-solvent was added dropwise 40 s before the end of the second spin-coating step. After spin-coating, the film was annealed at 120 °C for 30 min under a nitrogen atmosphere to obtain a tin-lead mixed narrow bandgap perovskite film.

[0053] (5) Transfer the thin film to the vapor deposition apparatus and deposit it under a vacuum of 9×10⁻⁶. -4 Under conditions of Pa and a deposition rate of 0.5 Å / s, C layers with a thickness of 35 nm were sequentially deposited. 60 A complete flexible tin-lead perovskite solar cell was obtained by adding a 10 nm thick BCP layer and a 120 nm thick silver electrode.

[0054] Example 4 The preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the mass concentration of the Allura Red aqueous solution is 0.2 mg / mL.

[0055] Example 5 The preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the mass concentration of the Allura Red aqueous solution is 0.5 mg / mL.

[0056] Example 6 The preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the mass concentration of the Allura Red aqueous solution is 1.5 mg / mL.

[0057] Example 7 The preparation method of this embodiment is basically the same as that of Example 1, except that in step (3), the mass concentration of the Allura Red aqueous solution is 2.0 mg / mL.

[0058] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that the alluring red interface treatment described in step (3) was not performed.

[0059] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that in step (3), the mass concentration of the Allura Red aqueous solution is 3.0 mg / mL.

[0060] Optical, morphological, interface, and photovoltaic performance tests were performed on the tin-lead hybrid narrow bandgap perovskite thin films and flexible solar cells of Example 1 (Target) and Comparative Example 1 (Control) prepared on PEN / ITO transparent flexible conductive substrates. The results are as follows: Figures 3 to 12 As shown.

[0061] Unless otherwise stated, all comparative tests were performed at room temperature. Example 1 and Comparative Example 1 used the same PEN / ITO flexible substrate, the same batch of samples, the same testing instruments, and the same testing parameters. The UV-Vis absorption spectroscopy scan range was 600–1100 nm; contact angle measurements were performed using equal-volume droplets, with readings taken at the same time after addition; steady-state photoluminescence and time-resolved photoluminescence measurements used an excitation wavelength of 405 nm; the scanning electron microscope tests used an accelerating voltage of 5.00 kV and a magnification of 20,000x. Using standardized flexible substrates and testing conditions helps reduce the impact of batch-to-batch substrate variations on thin film formation and device performance.

[0062] The device's photovoltaic performance under AM 1.5G standard simulated sunlight with an incident light intensity of 100 mW / cm² 2 Under the specified conditions, the solar simulator was calibrated using a standard silicon cell before testing; during the test, a cell with an area of ​​0.058 cm² was used. 2 The mask template was used to obtain the current density-voltage (J–V) curves under the same scanning direction and scanning rate. Figure 9 and Figure 10 The statistical results shown all use the same number of independent flexible device samples.

[0063] To evaluate the flexible mechanical stability of the devices, cyclic bending tests were conducted on the devices of Example 1 and Comparative Example 1 under a bending radius of 10 mm, and the photoelectric conversion efficiency was measured after the same number of bending cycles. The results were normalized to the initial photoelectric conversion efficiency before bending as 1, and the results are as follows: Figure 12 As shown.

[0064] Figure 3 The results show that, on a PEN / ITO flexible substrate, the absorption curves of the sample treated with the Allura Red interface essentially overlap with those of the control group in the 600–1100 nm range, with no significant shift in the absorption edge position. These results demonstrate that, at the modification concentration and film thickness used in this invention, ultrathin Allura Red interface modification does not significantly weaken the broad-spectrum absorption, nor does it introduce any discernible additional optical losses.

[0065] Figure 4The results show that in Comparative Example 1, the contact angle of the PEDOT:PSS surface on the PEN / ITO flexible substrate with the perovskite precursor solution was 11.27°, which decreased to 5.64° after treatment with 1.0 mg / mL Allura Red aqueous solution. This reduction in contact angle indicates that the Allura Red interface modification improved the wettability of the flexible hole transport layer surface with the precursor solution, making it easier for the precursor to spread uniformly and continuously cover the flexible substrate, which may have micro-undulations, thereby reducing local thin areas, pinholes, and potential stress concentration sites.

[0066] Figure 5 The results show that the water contact angle of the flexible perovskite film in Comparative Example 1 is 55.75°, while that in Example 1 is 64.91°. The increased water contact angle indicates enhanced hydrophobicity of the perovskite film surface after Allura Red interface modification, which helps to mitigate the penetration of external moisture into the flexible multilayer device. This improvement contributes to enhancing the device's moisture resistance and provides favorable conditions for improving environmental stability.

[0067] Figure 6 The results show that, under the same testing and fitting conditions, the TRPL decay characteristic lifetimes of the flexible sample in Comparative Example 1 and the flexible sample in Example 1 are 239 ns and 1495 ns, respectively. The significantly prolonged decay characteristic lifetime indicates that defect-related nonradiative recombination is suppressed after the delusion red interface modification. This result is consistent with the lower buried interface defect density; improvements in carrier extraction and transport need to be comprehensively judged in conjunction with the device photovoltaic performance results.

[0068] Figure 7 The steady-state photoluminescence (PL) results show that, under the same excitation and acquisition conditions, the PL intensity of the flexible perovskite film in Example 1 is higher than that in Comparative Example 1, and the emission peak position shows no significant shift. The increase in PL intensity is related to... Figure 6 The increased TRPL lifetime shown corroborates each other, indicating that the alluring red interface modification reduces defect-related nonradiative recombination at the flexible substrate / hole transport layer / perovskite buried interface, without significantly altering the band gap of the perovskite material.

[0069] Figure 8 The scanning electron microscope (SEM) images shown at 20,000x magnification demonstrate that, compared to Comparative Example 1, the perovskite thin film formed on the PEN / ITO flexible substrate in Example 1 exhibits more uniform grain size and distribution, fewer pinholes and local defects, and a denser film. This uniform and dense flexible functional layer helps reduce stress concentration caused by pinholes, rough grain boundaries, and abrupt changes in local thickness during bending, thereby reducing the risk of crack initiation and propagation and maintaining continuous carrier transport channels.

[0070] Figure 9The results show that, on the same PEN / ITO flexible device platform, the photoelectric conversion efficiency and fill factor of the device in Example 1 are higher than those in Comparative Example 1, and the performance distribution is more concentrated. This indicates that the allure red interface modification not only improves the photovoltaic performance of the flexible device, but also improves the repeatability and consistency of multilayer thin film preparation on the flexible substrate.

[0071] Figure 10 The results show that the open-circuit voltage and short-circuit current density of the flexible device in Example 1 are both higher than those in Comparative Example 1. Combined with... Figure 6 and Figure 7 The photoluminescence results show that the increase in open-circuit voltage is consistent with the reduction in non-radiative recombination at the buried interface of the flexible device; the improvement in fill factor and short-circuit current density is consistent with more effective hole extraction and more continuous carrier transport.

[0072] The photovoltaic performance of tin-lead hybrid narrow bandgap perovskite solar cells prepared on PEN / ITO flexible substrates in Examples 1, 4-7, and Comparative Examples 1-2 was tested, and the results are as follows: Figure 11 As shown. Flexible devices in each concentration group were tested under the same AM 1.5G illumination conditions and J-V test method as described above, and the same number of independent device samples were used for statistical analysis.

[0073] Figure 11 The photoelectric conversion efficiency distribution of flexible devices was compared when the mass concentrations of Allura Red aqueous solution were 0, 0.2, 0.5, 1.0, 1.5, 2.0, and 3.0 mg / mL. The results showed that the average photoelectric conversion efficiency of the flexible devices gradually increased as the mass concentration of Allura Red aqueous solution increased from 0 to 1.0 mg / mL; when the mass concentration exceeded 1.0 mg / mL, the device efficiency began to decrease; and when the mass concentration was 3.0 mg / mL, the device efficiency was lower than that of Comparative Example 1 without Allura Red interface treatment. This indicates that an appropriate amount of Allura Red can form an effective and ultrathin interface control layer, while excessively high concentrations may lead to molecular stacking, increased interfacial charge transport resistance, or decreased film uniformity. Under the process conditions of this embodiment, 1.0 mg / mL is the preferred interface modification concentration.

[0074] Figure 12The results show that after 5000 bending cycles, the normalized photoelectric conversion efficiency of the flexible device in Comparative Example 1 decreased to less than 50% of its initial value, while the flexible device in Example 1 still maintained above 99%. After the device in Example 1 was bent for another 10,000 cycles, the normalized photoelectric conversion efficiency remained above 98%. At the same number of cycles, the performance retention rate of Example 1 was significantly higher than that of Comparative Example 1. This result indicates that Allura Red interface modification can significantly improve the cyclic bending stability of PEN / ITO-based flexible tin-lead perovskite solar cells. Based on the aforementioned film morphology and interface characterization results, this improvement is speculated to be related to improved film uniformity, reduced buried interface defects and non-radiative recombination, and relief of local stress concentration.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible tin-lead perovskite solar cell, characterized in that: The material comprises a conductive substrate, a hole transport layer, an Allura Red interface modification layer, a tin-lead mixed narrow bandgap perovskite light absorption layer, an electron transport layer, a buffer layer, and a metal electrode layer stacked sequentially; the formation of the Allura Red interface modification layer includes the step of spin-coating an Allura Red aqueous solution onto the surface of the hole transport layer.

2. The flexible tin-lead perovskite solar cell as described in claim 1, characterized in that: The mass concentration of the Allura Red aqueous solution is 0.2–2.0 mg / mL.

3. The flexible tin-lead perovskite solar cell as described in claim 2, characterized in that: The spin coating speed of the Allure Red aqueous solution is 3000-6000 rpm, and the spin coating time is 20-40 s.

4. The flexible tin-lead perovskite solar cell as described in claim 1, characterized in that: The conductive substrate is a transparent, flexible conductive substrate; the raw material of the hole transport layer includes PEDOT:PSS; the raw material of the tin-lead mixed narrow bandgap perovskite light absorption layer includes materials with the general chemical formula A(Sn) x Pb 1-x B3 is a perovskite material, where A is selected from FA. + MA + 、Rb + and Cs + One or more of them, B is selected from Cl - ,Br - and I - One or more of them, 0 < x <1; The electron transport layer includes C 60 The buffer layer includes a BCP.

5. The flexible tin-lead perovskite solar cell as described in claim 4, characterized in that: The hole transport layer has a thickness of 20–50 nm; the tin-lead mixed narrow bandgap perovskite light absorption layer has a thickness of 500–1000 nm; the electron transport layer has a thickness of 25–35 nm; the buffer layer has a thickness of 5–10 nm; and the metal electrode layer has a thickness of 100–120 nm.

6. A method for preparing a flexible tin-lead perovskite solar cell as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1, a hole transport layer is spin-coated onto a conductive substrate and then subjected to thermal annealing. S2, Allura Red aqueous solution is spin-coated onto the surface of the hole transport layer and then heat-treated to form an Allura Red interface modification layer; S3, a tin-lead mixed narrow bandgap perovskite precursor solution is spin-coated onto the alluring red interface modification layer, and an anti-solvent is added dropwise during the spin-coating process. Then, a tin-lead mixed narrow bandgap perovskite light-absorbing layer is formed by thermal annealing. S4. An electron transport layer, a buffer layer, and a metal electrode layer are sequentially vacuum-deposited onto a tin-lead mixed narrow bandgap perovskite light-absorbing layer to obtain a flexible tin-lead perovskite solar cell.

7. The method for preparing a flexible tin-lead perovskite solar cell as described in claim 6, characterized in that: In step S1, the spin coating speed is 3000-5000 rpm and the spin coating time is 20-60 s; the heat annealing temperature is 120-150℃ and the heat annealing time is 10-30 min.

8. The method for preparing a flexible tin-lead perovskite solar cell as described in claim 6, characterized in that: In step S2, the heat treatment temperature is 80–110 °C, and the heat treatment time is 5–15 min.

9. The method for preparing a flexible tin-lead perovskite solar cell as described in claim 6, characterized in that: In step S3, the concentration of the tin-lead mixed narrow bandgap perovskite precursor solution is 1.8–2.4 mol / L; the antisolvent is selected from one or more of chlorobenzene, diethyl ether, acetone, toluene, ethyl acetate, and chloroform; the thermal annealing temperature is 80–120°C, and the thermal annealing time is 10–30 min.

10. The method for preparing a flexible tin-lead perovskite solar cell as described in claim 9, characterized in that: The spin coating comprises two steps: the first step is spin coating at 500–2000 rpm for 10–30 s, and the second step is spin coating at 3000–5000 rpm for 50–80 s; the antisolvent is added dropwise 20–40 s before the end of the second spin coating step.

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