Perovskite solar cell with inverted structure and preparation method thereof

Abstract

This invention belongs to the field of perovskite solar cells, and specifically relates to an inverted perovskite solar cell and its fabrication method. The inverted perovskite solar cell comprises a transparent conductive substrate and, sequentially stacked on the transparent conductive substrate, a hole transport layer, a self-assembled monolayer, a light-emitting single-crystal interlayer, a perovskite light-absorbing layer, a PDI passivation layer, an electron transport layer, a tunneling layer, and a metal electrode layer; wherein, the light-emitting single-crystal interlayer is composed of a green single-crystal [(CH3)3NC3H7][(C2H5)4N][MnBr4] layer with a thickness of 10-20 nm. This invention uses [(CH3)3NC3H7][(C2H5)4N][MnBr4] as a light-emitting single-crystal interlayer. Without changing the optical bandgap of the perovskite or affecting its surface morphology, placing it between the self-assembled monolayer and the perovskite light-absorbing layer can improve the light absorption of the perovskite solar cell, allowing light to be absorbed secondary by the perovskite and increasing hole mobility. This optimizes the interface contact between the perovskite and the hole transport layer, thereby improving device performance and effectively increasing the utilization rate of sunlight.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cells, and specifically relates to an inverted pin perovskite solar cell and its fabrication method. Background Technology

[0002] Perovskite solar cells (PSCs) have become a research hotspot in the photovoltaic field due to their high power conversion efficiency (PCE) and low manufacturing cost. In recent years, inverted perovskite solar cells have achieved breakthroughs in high PCE, exhibiting good stability, negligible hysteresis, and wide applications. However, their performance remains limited by insufficient light absorption efficiency and interface defects. Therefore, further optimization and development of inverted perovskite solar cells are currently a key research focus.

[0003] In existing technologies, to improve the light utilization efficiency and device performance of inverted perovskite solar cells, some researchers have attempted to introduce materials with luminescent properties between the charge transport layer and the perovskite light-absorbing layer. The initial design aim is to recover unused photons through the photoluminescence effect of single crystals, converting them into green light that is more easily absorbed by the perovskite layer, thereby improving light absorption efficiency. However, directly applying existing single-crystal materials to the interface of inverted perovskite solar cells presents many insurmountable defects and shortcomings. Firstly, coarse grains disrupt the interface morphology, forming a charge transport barrier. Conventionally synthesized luminescent single-crystal materials in existing technologies often have large grain sizes and poor film-forming properties, making it difficult to form uniform, continuous, ultrathin films at the interface. This rough physical morphology not only disrupts the crystallization kinetics of the upper perovskite film, leading to increased porosity and grain boundaries in the perovskite layer, but these single-crystal materials also generally possess strong intrinsic electrical insulation properties. Large grains form a severe electrical barrier layer at the interface, significantly increasing charge transfer resistance and hindering effective carrier extraction. This negative electrical impact often far outweighs the gains from optical conversion. Secondly, poor energy level matching and inadequate passivation of interface defects are significant issues. Existing single-crystal materials typically exhibit poor energy level matching with inverted structure devices (especially between the hole transport layer and the perovskite layer), and they cannot effectively interact with uncoordinated lead ions (Pb) on the perovskite surface. 2+ Chemical coordination occurs between these components. Therefore, they only serve a passive optical conversion function, failing to provide excellent defect passivation to block leakage paths. Instead, poor physical contact induces numerous deep-level defects at the interface, exacerbating non-radiative recombination losses and ultimately leading to a decrease in the device's open-circuit voltage. V oc ) and fill factor ( FF Severe attenuation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an inverted perovskite solar cell that addresses the shortcomings of the prior art by using [(CH3)3NC3H7][(C2H5)4N][MnBr4] green single crystal as a light supplement source for the perovskite layer, thereby enhancing the light utilization of the device and the contact between the perovskite and the hole transport layer, thus improving the device performance.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: An inverted perovskite solar cell includes a transparent conductive substrate and a hole transport layer (NiO) sequentially stacked on the transparent conductive substrate. x The structure consists of a single layer, a self-assembled monolayer (SAM layer), a luminescent single-crystal interlayer, a perovskite light-absorbing layer, a PDI passivation layer, an electron transport layer and a tunneling layer (PCBM layer), and a metal electrode layer; wherein the luminescent single-crystal interlayer is composed of a green single-crystal [(CH3)3NC3H7][(C2H5)4N][MnBr4] layer with a thickness of 10-20 nm.

[0006] According to the above scheme, the light-emitting single crystal interlayer is made by dissolving green single crystal powder [(CH3)3NC3H7][(C2H5)4N][MnBr4] in the solvent isopropanol, and then spin-coating it onto the SAM layer.

[0007] According to the above scheme, [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystals are prepared by solution evaporation method. They are green particles with a size of 30-50 nm and an absorption wavelength in the range of 300-450 nm.

[0008] Further, the preparation method of the luminescent single-crystal interlayer is as follows: trimethylpropylammonium bromide, manganese bromide tetrahydrate, and tetraethylammonium bromide are used as raw materials, dissolved in water, stirred until clear, and then ethanol is added. The evaporation is carried out by solvent evaporation, controlling the evaporation temperature at 65-75 ℃, and allowed to stand at a constant temperature for slow evaporation for 4-5 days, ultimately generating bulk green single crystals. The bulk green single crystals are ground into powder and dissolved in isopropanol to prepare a solution with a concentration of 0.1-0.3 mg / mL. This solution is then spin-coated onto the surface of the SAM layer and annealed at 90-110 ℃ for 5-15 minutes to form the luminescent single-crystal interlayer. The molar ratio of trimethylpropylammonium bromide, manganese bromide tetrahydrate, and tetraethylammonium bromide is 2:1:1, the concentration of trimethylpropylammonium bromide in water is 1-2 mmol / mL, and the volume of ethanol is 40%-60% of the water volume.

[0009] According to the above scheme, the hole transport layer (NiO) x The thickness of the layer is 15-25 nm.

[0010] According to the above scheme, the self-assembled monolayer (SAM layer) is formed by [4-(3,6-diphenyl-9H-carbazole-9-yl)butyl]phosphonic acid (Ph-4PACz) with a thickness of 5-10 nm.

[0011] According to the above scheme, the composition of the perovskite light-absorbing layer is Cs 0.05 MA 0.0475 FA 0.9025 PbI 2.85 Br 0.15 Perovskite, with a thickness of 400-600 nm.

[0012] According to the above scheme, the thickness of the PDI passivation layer is 5-10 nm. Wherein, PDI is piperazine dihydroiodide.

[0013] According to the above scheme, the tunneling layer is made of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) with a thickness of 8-12 nm.

[0014] According to the above scheme, the electron transport layer adopts [6,6]-phenyl-C 61 1-Methyl butyrate (PCBM), with a thickness of 60-70 nm.

[0015] According to the above scheme, the thickness of the metal electrode layer is in the range of 150-200 nm. The metal electrode layer can be selected from gold (Au), silver (Ag), copper (Cu), etc. The present invention uses Ag, which is currently the most commonly used electrode material.

[0016] The present invention also provides a method for fabricating the above-mentioned inverted perovskite solar cell, comprising the following steps: (1) Preparation of crystalline NiO on the surface of a transparent conductive substrate x The thin film is the hole transport layer; (2) Spin-coating Ph-4PACz solution onto the surface of the hole transport layer and annealing to obtain the SAM layer; (3) Spin-coating a green single crystal solution of [(CH3)3NC3H7][(C2H5)4N][MnBr4] onto the surface of the SAM layer, and annealing to obtain a single crystal luminescent interlayer; (4) Spin-coat the perovskite precursor solution onto the surface of the light-emitting single crystal interlayer. Before the spin coating is finished, add the anti-solvent chlorobenzene for deposition, and then anneal to obtain the perovskite light-absorbing layer. (5) A PDI passivation layer, an electron transport layer, a tunneling layer and a metal electrode layer are sequentially prepared on the surface of the perovskite absorber layer to obtain the inverted perovskite solar cell of the present invention.

[0017] According to the above scheme, in step (2), the concentration of Ph-4PACz solution is 0.4-0.6 mg / mL, rotate at 3000-5000 rpm for 30-40 seconds, and anneal at 90-110 ℃ for 5-15 minutes to obtain the SAM layer.

[0018] According to the above scheme, in step (3), the concentration of the green single crystal solution [(CH3)3NC3H7][(C2H5)4N][MnBr4] is 0.1-0.3 mg / mL, and the spin-coating volume is 50-150 μL / cm. 2 .

[0019] According to the above scheme, in step (3), the green single crystal solution is spin-coated at a speed of 4000-6000 rpm for 20-40 seconds and annealed at 90-110 ℃ for 5-15 minutes to obtain the luminescent single crystal interlayer.

[0020] According to the above scheme, in step (4), the concentration of the perovskite precursor solution is 1.5 M (calculated based on the effective Pb content); the spin-coating amount is 20-40 μL / cm. 2 The spin coating is performed in two steps: first, spin at 800-1200 rpm for 5-15 seconds, then continue spin coating at 4000-6000 rpm for 30-40 seconds. Ten to fifteen seconds before the end of the second spin coating, the anti-solvent chlorobenzene is added dropwise at a rate of 50-150 μL / cm³. 2 Annealing temperature: 90-110 ℃, annealing time: 20-40 minutes.

[0021] According to the above scheme, in step (5), the preparation process of the PDI passivation layer is as follows: A PDI isopropanol solution (PDI dissolved in isopropanol, concentration 0.1-0.2 mg / mL) is dropped onto the surface of the perovskite absorber layer (dropping amount 20-50 μL / cm). 2 Spin coat at 4000-6000 rpm for 20-40 seconds, and then anneal at 90-110 ℃ for 5-15 minutes.

[0022] According to the above scheme, in step (5), the electron transport layer is prepared by: using a chlorobenzene solution of PCBM (dissolving PCBM in chlorobenzene at a concentration of 15-25 mg / mL), which is dropped onto the surface of the PDI passivation layer (the amount of dropping is 10-30 μL / cm). 2 Spin coat at 1200-1600 rpm for 20-40 seconds until the coating is complete.

[0023] According to the above scheme, in step (5), the preparation process of the tunneling layer is as follows: A solution of BCP in isopropanol (BCP dissolved in chlorobenzene at a concentration of 0.4-0.6 mg / mL) is dropped onto the surface of the electron transport layer (dropping volume is 40-60 μL / cm). 2 Spin coat at 5000-7000 rpm for 10-20 seconds until the coating is complete.

[0024] According to the above scheme, in step (5), the metal electrode layer is preferably formed by thermal evaporation deposition.

[0025] Compared with the prior art, the beneficial effects of the present invention are: First, this invention uses [(CH3)3NC3H7][(C2H5)4N][MnBr4] as a luminescent monocrystalline interlayer. By controlling its monocrystalline size and interlayer thickness, and without altering the optical bandgap of the perovskite or affecting its surface morphology, it is positioned between the self-assembled monolayer and the perovskite light-absorbing layer, thereby improving the light absorption of the perovskite solar cell. Specifically, [(CH3)3NC3H7][(C2H5)4N][MnBr4] allows light to be absorbed a second time by the perovskite and increases hole mobility, optimizing the interface between the perovskite and hole transport layer, reducing porosity, and increasing hole mobility, thus improving device performance and effectively increasing solar energy utilization.

[0026] Second, by using [(CH3)3NC3H7][(C2H5)4N][MnBr4] as a light-emitting single crystal interlayer, the present invention achieves selective filtering and efficient reuse of sunlight in the optical path design of solar cell devices, and optimizes the energy level arrangement of the perovskite and hole transport layer interface or passivates surface defects, thereby improving the energy conversion efficiency of inverted PSCs. Attached Figure Description

[0027] Figure 1 The images show the particle size distribution statistics and scanning electron microscope images of the green single crystal powder obtained in the embodiments of the present invention.

[0028] Figure 2 The figures show the ultraviolet-visible absorption spectrum and photoluminescence emission spectrum of the green single crystal obtained in the embodiments of the present invention. Figure a shows the ultraviolet-visible absorption spectrum, and Figure b shows the photoluminescence emission spectrum.

[0029] Figure 3 The JV curves are for the solar cells of Examples 1-3 and Comparative Examples 1-2.

[0030] Figure 4Box plots comparing the photoelectric performance parameters of solar cells in Examples 1-3 and Comparative Examples 1-2 are shown. In Figure a, the open-circuit voltage is shown; in Figure b, the short-circuit current is shown; in Figure c, the fill factor is shown; and in Figure d, the efficiency is shown.

[0031] Figure 5 This is a schematic diagram of the spectral selective filtering optical path for solar cells using luminescent monocrystalline interlayers and solar cells without luminescent monocrystalline interlayers, according to the present invention.

[0032] Figure 6 The samples (NiO) used in Examples 1-3 and Comparative Examples 1-2 x Cross-sectional image of a single-crystal perovskite layer (SAM-Single-crystal-perovskite layer) obtained by field emission scanning electron microscopy (SEM).

[0033] Figure 7 The images show the XRD patterns of the solar cells in Examples 1-3 and Comparative Examples 1-2.

[0034] Figure 8 The dark current density test graphs are for the solar cells of Examples 1-3 and Comparative Examples 1-2.

[0035] Figure 9 The hole mobility spectra are for the solar cells of Examples 1-3 and Comparative Examples 1-2.

[0036] Figure 10 The ultraviolet-visible absorption spectra of the solar cells of Examples 1-3 and Comparative Examples 1-2 are shown.

[0037] Figure 11 The steady-state photoluminescence (PL) spectra of the solar cells of Examples 1-3 and Comparative Examples 1-2 are shown.

[0038] Figure 12 The time-resolved (TR-PL) spectra of the solar cells of Examples 1-3 and Comparative Examples 1-2 are shown. Detailed Implementation

[0039] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0040] In the following examples, the specific preparation steps of the green single crystal solution are as follows: (1) Dissolve trimethylpropylammonium bromide (0.7284 g, 4 mmol), manganese bromide tetrahydrate (0.5736 g, 2 mmol) and tetraethylammonium bromide (0.4203 g, 2 mmol) in 2 mL of deionized water and stir until clear; (2) Add ethanol (1 mL) to the solution obtained in step (1), and then place it in an oven (70 °C) and let it stand in the oven for 4-5 days to generate blocky green crystals by solvent evaporation. (3) The bulk green crystals obtained in step (2) were ground into powder, i.e., green single crystal powder [(CH3)3NC3H7][(C2H5)4N][MnBr4], and dispersed in isopropanol to prepare a green single crystal solution with a concentration of 0.2 mg / mL. The obtained green single crystal powder was subjected to scanning electron microscopy and particle size distribution statistical testing, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the ground and dispersed green single-crystal powder has a granular morphology, with the particle size mainly concentrated in the range of 30-50 nm. This indicates that the green single-crystal powder can form nanoscale particles, which is beneficial for the subsequent formation of a uniform and ultrathin luminescent single-crystal interlayer on the surface of the self-assembled monolayer. Further UV-Vis absorption spectroscopy and photoluminescence emission spectroscopy of the obtained green single crystal were tested, and the results are as follows... Figure 2 As shown. By Figure 2 (a) It can be seen that green single crystals exhibit significant absorption in the 300-450 nm range; from Figure 2 (b) It can be seen that the green single crystal exhibits a significant emission peak near 514 nm, indicating that it can absorb ultraviolet / blue light and emit green light, thereby providing a secondary absorption light supplement for the perovskite light-absorbing layer. In the above-mentioned preparation process of green single crystal, ethanol is added to the solvent. Taking advantage of the fact that ethanol's boiling point (78℃) is lower than that of water and that it is easily displaced and removed, the capillary stress during the drying process of the single crystal is greatly reduced, effectively preventing single crystal cracking and ensuring the structural integrity of the single crystal.

[0041] In the following embodiments, NiO x The solution preparation process is as follows: 1) Dissolve Ni(NO3)2·6H2O (20 mmol) in deionized water (20 mL), and add NaOH aqueous solution (4 mL, 10 mol / L) while stirring slowly. Stir for 20 min to obtain colloidal precipitate; 2) The colloidal precipitate was washed with deionized water and then placed in a drying oven and dried at 80 °C for 6 hours to obtain a green powder; 3) The green powder was placed in a muffle furnace and calcined at 270 °C for 2 h to obtain a black powder, which is NiO. x Nanoparticles; 4) NiO x Nanoparticles were dispersed in a mixed solvent of deionized water and isopropanol (3:1, v / v) at a concentration of 10 mg / mL and stirred overnight to obtain NiO. x Solution.

[0042] In the following examples, the Ph-4PACz solution was prepared by dissolving Ph-4PACz in ethanol at a concentration of 0.5 mg / mL.

[0043] In the following examples, the perovskite precursor solution was prepared as follows: CsI (0.01949 g), FAI (0.23280 g), MABr (0.00798 g), PbI2 (0.75375 g), and PbBr2 (0.02821 g) were dissolved in a mixed solvent (v / v, DMF:DMSO = 4:1, DMF = 0.8 mL, DMSO = 0.2 mL) to obtain 1.5 M Cs 0.05 MA 0.0475 FA 0.9025 PbI 2.85 Br 0.15 The perovskite solution was then filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane.

[0044] In the following examples, the PDI-isopropanol solution was prepared as follows: 0.0008 g of PDI powder was dissolved in 4 mL of isopropanol, and the mixture was heated and stirred overnight to ensure complete dissolution of PDI, resulting in a PDI-isopropanol solution with a concentration of 0.2 mg / mL.

[0045] In the following examples, the PCBM solution was prepared by dissolving PCBM in chlorobenzene at a concentration of 20 mg / mL.

[0046] In the following examples, the BCP solution was prepared by dissolving the BCP solution in isopropanol at a concentration of 0.5 mg / mL.

[0047] Example 1 The specific fabrication steps of an inverted perovskite solar cell are as follows: (1) The ITO glass substrate (1.5×2 cm) was ultrasonically cleaned for 30 min in sequence with detergent, deionized water, acetone and ethanol. (2) Place the cleaned ITO glass substrate into an ultraviolet ozone cleaner and irradiate for 15 minutes to remove NiO. x The solution was spin-coated onto an ITO glass substrate at 2000 rpm for 30 s, followed by annealing at 120 °C for 30 min to obtain NiO. x Hole transport layer, 20 nm thick; (3) Place the Ph-4PACz solution in NiO x The hole transport layer was spin-coated on the surface, rotated at 4000 rpm for 30 s, and then annealed at 100℃ for 10 min to obtain a SAM layer with a thickness of 8 nm. (4) Add 50 μL / cm to the SAM layer 2 A green single crystal solution with a concentration of 0.2 mg / mL was spin-coated at 5000 rpm for 30 s, and then annealed at 100 ℃ for 5 min on an annealing stage to obtain a luminescent single crystal interlayer with a thickness of 15 nm. (5) The perovskite precursor solution was prepared at a concentration of 20 μL / cm³. 2 The amount of material was spin-coated onto the luminescent single-crystal interlayer at 1000 rpm for 10 s, then at 5000 rpm for 40 s. Ten seconds before the end of the spin-coating process, 66.7 μL / cm³ of the material was transferred. 2 Chlorobenzene was dropped onto the membrane as an antisolvent, and then immediately placed on an annealing table at 100°C for 30 min to obtain a perovskite light-absorbing layer with a thickness of 550 nm. (6) PDI-isopropanol solution was prepared at 33.3 μL / cm 2 The amount of material was dropped onto the surface of the perovskite light-absorbing layer and spin-coated at 5000 rpm for 30 s. After spin-coating, the material was annealed at 100℃ for 10 min to obtain a PDI passivation layer with a thickness of 8 nm. (7) Dissolve the PCBM solution at 30 μL / cm 2 The amount of the solution was dropped onto the PDI passivation layer and spin-coated at 1400 rpm for 30 s to prepare an ETL layer with a thickness of 65 nm. (8) Dissolve the BCP solution at 50 μL / cm 2 The amount of material was dropped onto the ETL layer and spin-coated at 6000 rpm for 15 s to prepare a tunneling layer with a thickness of 10 nm. (9) Using vacuum (2×10 -5 A silver electrode with a thickness of approximately 150 nm was deposited on the surface of the tunneling layer using a thermal evaporation process.

[0048] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the green single crystal solution was replaced with an equal volume of isopropanol, while the remaining steps were the same as in Example 1.

[0049] Example 2 The difference between Example 2 and Example 1 is that the concentration of the green single crystal solution is 0.1 mg / mL, while the rest of the steps are the same as in Example 1.

[0050] Example 3 The difference between Example 3 and Example 1 is that the concentration of the green single crystal solution is 0.3 mg / mL, while the rest of the steps are the same as in Example 1.

[0051] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the green single crystal solution is replaced by ((CH3)4N)2(C2H5)4N·MnBr4 single crystal, and the remaining steps are the same as in Example 1.

[0052] like Figure 3 As shown, this figure represents Examples 1-3 and Comparative Examples 1-2. JV The graph and Table 1 show the data obtained from this test. V oc Open circuit voltage, J sc For current density, FF As the fill factor, PCE For photoelectric conversion efficiency, PCE = V oc × J sc × FF Based on the photoelectric performance parameters in Table 1, the optimal result is achieved by the blank control group (Comparative Example 1) without the addition of luminescent single crystals. PCE The efficiency was 19.74%. When the [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystal of the present invention was added, the photovoltaic performance of the device was significantly improved. Specifically, when the concentration of this luminescent single crystal was 0.2 mg / mL (Example 1), the device achieved its optimal energy conversion efficiency of 22.32%. However, when the single crystal of the present invention was replaced with the existing ((CH3)4N)2(C2H5)4N·MnBr4 luminescent single crystal (Comparative Example 2), the photovoltaic performance of the device decreased sharply, and its optimal efficiency was reduced. PCE The efficiency plummeted to 17.42%, even significantly lower than the blank control group (Comparative Example 1) without any added single crystal. A comprehensive comparison of the above data demonstrates that although the existing luminescent single crystal in Comparative Example 2 is similar in material composition to the single crystal of this invention, directly introducing it into the interface of the inverted perovskite solar cell of this invention not only fails to achieve performance gains but also leads to a severe deterioration in the overall device efficiency. This confirms that the use of [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystal in this invention is specific and irreplaceable in improving the photovoltaic performance of the device, and its application effect surpasses the expectations of existing technologies, achieving unexpected technical results.

[0053] Table 1. Photovoltaic performance parameters of the solar cells in the examples and comparative examples.

[0054] like Figure 4As shown in the figure, this is a comparison of the photoelectric performance parameters of Examples 1-3 and Comparative Examples 1-2. With the introduction and increase of the concentration of the [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystal in Examples 1-3, the photoelectric conversion efficiency of the solar cell devices is superior to that of the comparative examples. Among them, the device of Example 1 (corresponding to the optimal concentration of 0.2 mg / mL) has the best performance in all aspects, and the parameters are also relatively concentrated, indicating that it has good preparation stability and reproducibility. Secondly, from the comparison results of material substitution, when the ((CH3)4N)2(C2H5)4N·MnBr4 single crystal in the prior art is used for substitution (Comparative Example 2), not only are the photoelectric parameters of the device (especially...) significantly improved, but also... V oc and FF The data showed a sharp drop, and its distribution was not concentrated. This further confirms that manganese-based single crystals in the prior art are not suitable for the inverted perovskite solar cell interface of this invention.

[0055] Interface optimization analysis: like Figure 5 As shown in the figure, this is a schematic diagram of the optical path optimization of manganese-based luminescent single crystal. The [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystal can absorb light that is not absorbed by the perovskite and emit green light. This green light will be absorbed again by the perovskite, so that the entire device is supplemented with light, thereby improving photovoltaic performance.

[0056] like Figure 6 As shown, this figure is a field emission scanning electron microscope (SEM) cross-sectional view of the samples from Examples 1-3 and Comparative Examples 1-2. Observation Figure 6 As can be seen from this, in Comparative Example 1 (blank control group) without any added luminescent single crystal, the perovskite film has relatively small grains, numerous transverse grain boundaries, and a loose contact observed at the interface between the perovskite and the bottom charge transport layer. Examples 1-3, based on Comparative Example 1, introduce [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystals, effectively improving the crystallinity of the perovskite film. Specifically, the grain size increases and grows vertically, almost eliminating transverse grain boundaries, and a tight physical contact is formed between the bottom of the perovskite and the single crystal interlayer, reducing energy loss caused by non-radiative recombination. Comparative Example 2 and Examples (…) use existing technology ((CH3)4N)2(C2H5)4N·MnBr4 single crystals instead of… Figure 6c) In stark contrast, the crystallinity of this group of perovskite films has severely degraded. Because the single-crystal materials in the prior art have relatively large grains and are prone to aggregation at the interface, they not only fail to form a smooth template to guide growth but also severely damage the uniformity of the interface. Affected by this rough substrate, the perovskite film in Comparative Example 2 exhibits a fragmented and fine-grained state with numerous and disordered grain boundaries. More critically, obvious pores appear at its bottom interface.

[0057] like Figure 7 As shown, this figure contains the XRD patterns of Examples 1-3 and Comparative Examples 1-2. The XRD patterns of Examples 1-3 and Comparative Example 1 show no significant changes in shape, indicating that spin-coating the [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystal does not affect the formation of the perovskite layer. However, the intensity of the characteristic diffraction peaks of the perovskite film is improved, especially in the example with the optimal addition amount, where the diffraction peak intensity of the (100) crystal plane is the highest. This indicates that the crystallization of the perovskite film is effectively promoted, and the perovskite grains are induced to grow with a highly preferred orientation along the direction perpendicular to the substrate. Simultaneously, the lead iodide peak decreases after passivation, reducing deep-level defects. When the existing ((CH3)4N)2(C2H5)4N·MnBr4 single crystal was used as a substitute (Comparative Example 2), the XRD diffraction peak intensity of the perovskite film decreased, especially on the (100) crystal plane, which was not only much lower than that of the example, but also significantly weaker than the blank control group without any single crystal added (Comparative Example 1). Furthermore, the lead iodide peak was enhanced. This indicates that the existing single crystal material, due to its coarse and uneven grain distribution, severely disrupts the film-forming kinetic environment at the bottom of the perovskite, hinders the orderly crystallization of the perovskite, and leads to an increase in internal defects and low crystallization quality in the film.

[0058] like Figure 8 The diagram shows the dark current density test results for Examples 1-3 and Comparative Examples 1-2. The dark current of Examples 1-3 is significantly lower than that of Comparative Example 1, indicating that the leakage current of the device is not significant. This fully demonstrates that the [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystal used in this invention plays an excellent role in defect passivation at the interface, effectively blocking the interface leakage current channel, which is beneficial to improving the photovoltaic performance of IPSCs. However, when Comparative Example 2 introduced the existing ((CH3)4N)2(C2H5)4N·MnBr4 single crystal into the interface, it not only failed to achieve the passivation effect, but also destroyed the original interface electrical contact, induced a large number of deep-level defects, and formed a serious short-circuit leakage current channel.

[0059] like Figure 9As shown in the figure, this is a hole mobility curve of pure hole devices corresponding to Examples 1-3 and Comparative Examples 1-2, obtained based on the space charge-limited current (SCLC) model. According to the Mott-Gurney law, the larger the slope of the curve in the SCLC region at the tail end, the higher the carrier mobility inside the material and at the interface. From the linear fitting results in the figure, it can be seen that the slope of Comparative Example 1 without the addition of luminescent single crystal is relatively low, indicating that its intrinsic carrier mobility is limited. However, after introducing [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystal in the examples, the slope of the device curves is significantly improved. In particular, Example 1, which reaches the optimal concentration, has the largest curve slope and the highest carrier mobility. This fully demonstrates that the [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystal used in this invention not only does not hinder charge movement at the interface, but also constructs an extremely smooth charge transport channel by optimizing the interface energy level arrangement and improving the crystal quality of the perovskite bottom, significantly reducing the transport barrier. However, when the existing ((CH3)4N)2(C2H5)4N·MnBr4 single crystal is introduced at the lower interface of the device (Comparative Example 2), the slope of its curve is lower than that of Comparative Example 1 without the addition of a light-emitting single crystal. This electrical phenomenon further confirms that the existing manganese-based single crystal material, due to its strong intrinsic electrical insulation properties and rough grain morphology, will produce severe electrical physical barriers when directly introduced into the interface, greatly deteriorating the charge extraction and transport process.

[0060] Optical path optimization analysis: like Figure 10 As shown in the figure, this is the UV-Vis absorption spectrum of Examples 1-3 and Comparative Examples 1-2. It can be seen from the figure that Examples 2-3, which introduced [(CH3)3NC3H7][(C2H5)4N][MnBr4] luminescent single crystals, have higher absorption intensities at around 500 nm (green light band) than Comparative Example 1, which did not add luminescent single crystals. This indicates that the green single crystals absorb light in different spectral bands that are not utilized by the perovskite and convert them into green visible light that the perovskite can absorb, forming secondary light absorption. This optical path design makes the light absorption range of the perovskite layer wider, thereby improving the light utilization rate of the entire device and enhancing the photovoltaic performance of the device. The absorption intensity is highest when the single crystal concentration is 0.2 mg / mL. However, the absorption intensity of the ((CH3)4N)2(C2H5)4N·MnBr4 single crystal introduced from the existing technology (Comparative Example 2) is lower than that of Comparative Example 1 without the addition of a luminescent single crystal. This phenomenon indicates that the existing single crystal material, due to its large grain size and extremely uneven distribution, is not conducive to the formation of the upper perovskite layer when used as an interlayer. This results in a decrease in the density and increase in porosity of the formed perovskite light-absorbing layer. This deteriorated physical morphology leads to severe interfacial light scattering and leakage loss, completely offsetting any potential weak luminescence gain.

[0061] like Figures 11-12 As shown in the figure, the steady-state photoluminescence (PL) and time-resolved (TR-PL) spectra of Examples 1-3 and Comparative Examples 1-2 are presented. Compared with Comparative Example 1, Examples 1-3 exhibit stronger fluorescence intensity and longer carrier lifetime. This indicates that the re-emission light of the [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystal is absorbed twice by the perovskite, increasing the number of photogenerated carriers. At the same time, the optimized perovskite film has less non-radiative recombination loss, stronger radiative recombination, and fewer defects. Among them, Example 1 has the highest fluorescence intensity and the longest carrier lifetime. However, when the existing ((CH3)4N)2(C2H5)4N·MnBr4 single crystal (Comparative Example 2) is introduced, the PL peak intensity of the film shows a sharp quenching. The PL peak intensity and carrier lifetime are both lower than those of the blank control group (Comparative Example 1). This indicates that the existing single crystal material, due to its coarse grains and uneven film formation, severely damages the crystal quality of the perovskite, inducing a large number of deep-level defect states at the interface. These surging defects act as nonradiative recombination centers, consuming large amounts of photogenerated carriers, leading to quenching of PL intensity and reduced carrier lifetime.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An inverted perovskite solar cell, characterized in that, It includes a transparent conductive substrate and a hole transport layer, a self-assembled monolayer, a light-emitting single-crystal interlayer, a perovskite light-absorbing layer, a PDI passivation layer, an electron transport layer, a tunneling layer, and a metal electrode layer, which are sequentially stacked on the transparent conductive substrate; wherein, the light-emitting single-crystal interlayer is composed of a green single-crystal [(CH3)3NC3H7][(C2H5)4N][MnBr4] layer with a thickness of 10-20 nm.

2. The inverted perovskite solar cell according to claim 1, characterized in that, The method for preparing the luminescent single-crystal interlayer is as follows: trimethylpropylammonium bromide, manganese bromide tetrahydrate and tetraethylammonium bromide are used as raw materials, dissolved in water, stirred until clear, and then ethanol is added to generate bulk green single crystals by solvent evaporation; the bulk green single crystals are ground into powder and dissolved in isopropanol to prepare a green single crystal solution, which is then spin-coated onto the surface of a self-assembled monolayer and annealed to form a luminescent single-crystal interlayer.

3. The inverted perovskite solar cell according to claim 2, characterized in that, In the preparation of the luminescent single-crystal interlayer, the molar ratio of trimethylpropylammonium bromide, manganese bromide tetrahydrate, and tetraethylammonium bromide is 2:1:1; the concentration of trimethylpropylammonium bromide in water is 1-2 mmol / mL; the amount of ethanol used is 40%-60% of the water volume; the evaporation temperature of the solvent evaporation method is 65-75℃, and the evaporation time is 4-5 days; the concentration of the green single-crystal solution is 0.1-0.3 mg / mL; the annealing temperature is 90-110℃, and the annealing time is 5-15 minutes.

4. The inverted perovskite solar cell according to claim 1, characterized in that, The luminescent single-crystal interlayer is composed of [(CH3)3NC3H7][(C2H5)4N][MnBr4] single crystals, with a morphology of green particles, a size of 30-50 nm, and an absorption wavelength in the range of 300-450 nm.

5. The inverted perovskite solar cell according to claim 1, characterized in that, The hole transport layer has a thickness of 15-25 nm; the self-assembled monolayer is formed of [4-(3,6-diphenyl-9H-carbazole-9-yl)butyl]phosphonic acid, with a thickness of 5-10 nm; the perovskite light-absorbing layer is composed of Cs. 0.05 MA 0.0475 FA 0.9025 PbI 2.85 Br 0.15 The perovskite layer has a thickness of 400-600 nm; the PDI passivation layer has a thickness of 5-10 nm; the tunneling layer is made of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with a thickness of 8-12 nm; the electron transport layer is made of [6,6]-phenyl-C 61 1-Methyl butyrate, with a thickness of 60-70 nm; the thickness of the metal electrode layer is in the range of 150-200 nm.

6. A method for fabricating an inverted perovskite solar cell according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Preparation of crystalline NiO on the surface of a transparent conductive substrate x The thin film is the hole transport layer; (2) Spin-coating Ph-4PACz solution onto the surface of the hole transport layer and annealing to obtain a self-assembled monolayer; (3) Spin-coating a green single crystal solution of [(CH3)3NC3H7][(C2H5)4N][MnBr4] onto the surface of the self-assembled monolayer, and annealing to obtain a single crystal luminescent interlayer; (4) Spin-coat the perovskite precursor solution onto the surface of the light-emitting single crystal interlayer. Before the spin coating is finished, add the anti-solvent chlorobenzene for deposition, and then anneal to obtain the perovskite light-absorbing layer. (5) A PDI passivation layer, an electron transport layer, a tunneling layer and a metal electrode layer are sequentially prepared on the surface of the perovskite absorber layer to obtain the inverted perovskite solar cell of the present invention.

7. The method for fabricating an inverted perovskite solar cell according to claim 6, characterized in that, In step (3), the concentration of the green single crystal solution [(CH3)3NC3H7][(C2H5)4N][MnBr4] is 0.1-0.3 mg / mL, and the spin-coating volume is 50-150 μL / cm. 2 .

8. The method for fabricating an inverted perovskite solar cell according to claim 6, characterized in that, In step (3), the green single crystal solution is spin-coated at a speed of 4000-6000 rpm for 20-40 seconds and annealed at 90-110℃ for 5-15 minutes to obtain the luminescent single crystal interlayer.

9. The method for fabricating an inverted perovskite solar cell according to claim 5, characterized in that, In step (2), the concentration of Ph-4PACz solution is 0.4-0.6 mg / mL. It is rotated at 3000-5000 rpm for 20-40 seconds and annealed at 90-110℃ for 5-15 minutes to obtain a self-assembled monolayer. In step (4), the concentration of the perovskite precursor solution is 1.5 M; the spin-coating amount is 20-40 μL / cm. 2 The spin coating is performed in two steps: first, spin at 800-1200 rpm for 5-15 seconds, then continue spin coating at 4000-6000 rpm for 30-40 seconds; 10-15 seconds before the end of the second spin coating, the anti-solvent chlorobenzene is added dropwise at a rate of 50-150 μL / cm. 2 Annealing temperature: 90-110 ℃, annealing time: 20-40 minutes.

10. The method for fabricating an inverted perovskite solar cell according to claim 5, characterized in that, In step (5), the PDI passivation layer is prepared by dissolving PDI in isopropanol at a concentration of 0.1-0.2 mg / mL and adding it dropwise onto the surface of the perovskite absorber layer at a rate of 20-50 μL / cm. 2 Spin coat at 4000-6000 rpm for 20-40 seconds, and anneal at 90-110℃ for 5-15 minutes after spin coating. Preparation of the electron transport layer: PCBM is dissolved in chlorobenzene at a concentration of 15-25 mg / mL, and then dropped onto the surface of the PDI passivation layer at a rate of 10-30 μL / cm. 2 Spin coat at 1200-1600 rpm for 20-40 seconds until the coating is complete. Preparation of the tunneling layer: BCP is dissolved in chlorobenzene at a concentration of 0.4-0.6 mg / mL, and then dropped onto the surface of the electron transport layer at a rate of 40-60 μL / cm. 2 Spin coat at 5000-7000 rpm for 10-20 seconds until the coating is complete.

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