Preparation method of pure iodine broadband gap perovskite solar cell based on difluorophthalonitrile passivation

Abstract

The invention discloses a preparation method of a pure iodine broadband gap perovskite solar cell based on difluorophthalonitrile passivation, and relates to the technical field of solar cells. According to the cell, the surface of perovskite is treated through difluorophthalonitrile, on one hand, fluorine atoms and cyano groups have strong electronegativity, so that the center of a benzene ring is positively charged, charged iodine defects can be attracted through anion-pi interaction, further diffusion of the iodine defects is prevented, and ion migration is inhibited; on the other hand, fluorine atoms can interact with hydrogen atoms on organic cations in perovskite through hydrogen bonds, organic components are stabilized, and volatilization or decomposition of the organic components is inhibited. And fluorine can also form a hydrophobic protection layer on the surface of the perovskite, so that the environmental stability of the perovskite cell is improved. On the basis, the surface and interface defects of the perovskite are obviously reduced, and ion migration and non-radiative recombination are inhibited, so that the photoelectric conversion efficiency of the perovskite solar cell is improved, and the hysteresis effect of the device is reduced.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell technology, specifically relating to a method for preparing a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation. Background Technology

[0002] Perovskite solar cells (PSCs), as a revolutionary photovoltaic technology, have made remarkable progress over the past decade thanks to their excellent photoelectric conversion efficiency, low manufacturing cost, and outstanding photoelectric performance. Currently, the certified efficiency of single-junction perovskite cells has exceeded 27%, reaching a level comparable to mainstream crystalline silicon cells, demonstrating enormous commercial application potential. Especially in the wave of research and development of tandem solar cells (such as perovskite / crystalline silicon and perovskite / perovskite tandem), wide-bandgap perovskite cells (bandgap > 1.65 eV) as the top cell have become key components for breaking through the theoretical efficiency limit. To date, the efficiency of perovskite / crystalline silicon tandem solar cells has exceeded 34.9%. While cell efficiency continues to rise, device operational stability is also a crucial factor. Organic-inorganic hybrid pure iodine wide-bandgap perovskite exhibits excellent photostability due to the absence of halide segregation, making it one of the ideal choices for perovskite / crystalline silicon tandem solar cells.

[0003] However, pure iodine-based wide-bandgap perovskites face several challenges in practical applications, limiting their performance ceiling and operational stability. The perovskite / electron transport layer interface is a weak point for defect accumulation and moisture / oxygen erosion, and iodine-related defects readily diffuse into the electron transport layer and metal electrodes, seriously threatening the durability of perovskite solar cells. Iodine-related charged defects are among the most common defects in perovskites; these defects have low formation energies and readily promote defect diffusion through vacancy mediation, leading to ion migration, phase separation, and hysteresis effects.

[0004] In summary, surface passivation engineering is one of the most effective strategies for improving the performance of wide-bandgap perovskite solar cells. Developing a novel, efficient, and multifunctional passivation material and process can synergistically achieve deep passivation of various defects on the surface of wide-bandgap perovskites, precise control of interface energy levels, and effective blocking of ion migration channels. This will enable the fabrication of high-efficiency, high-stability, and low-hysteresis pure iodine wide-bandgap perovskite solar cells, laying a key material foundation for the realization of high-performance tandem photovoltaic devices. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned shortcomings of existing technologies and propose a method for fabricating a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation. Difluorophthalonitrile passivates uncoordinated Pb defects on the perovskite surface while simultaneously adsorbing charged iodine defects, preventing further diffusion of iodine defects, inhibiting ion migration, reducing the defect density on the perovskite film surface, and improving interface stability. This enhances the photoelectric conversion efficiency and operational stability of the perovskite solar cell, while suppressing device hysteresis. Furthermore, its passivation effect is independent of its concentration. This makes it possible to achieve high-concentration passivation without compromising device performance, thereby significantly improving passivation durability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for fabricating a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation. The perovskite solar cell structure, from bottom to top, is stacked as follows: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode; comprising the following steps:

[0008] Step 1: Treatment of transparent conductive substrate;

[0009] Step 2: Spin-coating a hole transport layer onto a transparent conductive substrate;

[0010] Step 3: Spin-coat the prepared hole transport layer with perovskite precursor solution, induce crystallization using antisolvent, and then anneal to obtain the perovskite light-absorbing layer.

[0011] Step 4: Spin-coat difluorophthalonitrile solution onto the perovskite light-absorbing layer, and then anneal to obtain an interface passivation layer;

[0012] Step 5: Fabricate an electron transport layer on the interface passivation layer;

[0013] Step 6: Prepare a buffer layer on the electron transport layer;

[0014] Step 7: Evaporate and deposit a metal electrode on the buffer layer;

[0015] The interface passivation layer is obtained by spin-coating a difluorophthalonitrile isopropanol solution onto a perovskite light-absorbing layer followed by annealing. The structural formula of the interface passivation material difluorophthalonitrile is:

[0016] .

[0017] Furthermore, the transparent conductive substrate in step 1 of this invention is selected from either FTO conductive glass or ITO conductive glass.

[0018] Furthermore, the hole transport layer in step 2 of this invention is any one or more of the following materials: nickel oxide, [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphoric acid, [2-[9H-carbazole-9-yl]ethyl]phosphonic acid, and [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid; the preparation method of the hole transport layer material solution is as follows: when the selected hole transport layer material is an organic monolayer, the hole transport layer material is dissolved in an alcohol solvent to obtain a solution with a concentration of 0.3-1.0 mg / mL; the spin coating parameters are 3000-5000 rpm, the spin coating time is 20-30 s, the annealing temperature is 90-100℃, and the annealing time is 5-10 min.

[0019] Furthermore, the perovskite in step 3 of this invention is a pure iodine wide-bandgap perovskite with an organic-inorganic hybrid structure, having a bandgap of 1.65-1.7 eV. The perovskite material is selected from CsI, MAI, FAI, DMAI, RbI, and PbI2. The antisolvent is any one or more of ethyl acetate, methyl acetate, chlorobenzene, anisole, or diethyl ether.

[0020] Furthermore, the preparation method of the perovskite precursor solution of the present invention is as follows: in an inert atmosphere, a wide-bandgap perovskite light-absorbing layer material is dissolved in a mixed solvent of DMF and NMP (in a ratio of 4:1) to obtain a perovskite precursor solution with a concentration of 1.0-1.5M; the spin-coating parameters are 2000-4000 rpm and the spin-coating time is 20-40 s; the annealing temperature is 90-110℃ and the annealing time is 5-20 min.

[0021] Furthermore, in step 4 of this invention, the concentration of the difluorophthalonitrile interface passivation material is 2-20 mg / ml, and the solvent is an alcohol, including one or more of isopropanol and methanol. The interface passivation layer is prepared by a solution spin-coating method, wherein the spin-coating parameters are 3000-5000 rpm, spin-coating time 20-40 s, annealing temperature 80-100℃, and annealing time 5-10 min.

[0022] Furthermore, the electron transport layer material in step 5 of this invention is selected from PCBM and C60.

[0023] Furthermore, the buffer layer material in step 6 of this invention is selected from BCP and SnOx.

[0024] Furthermore, the metal electrode material in step 7 of this invention is selected from any one of Au, Ag, and Cu, and is prepared by thermal evaporation with a thickness of 80-120 nm.

[0025] Secondly, the present invention provides a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation prepared by the above method.

[0026] Thirdly, the present invention provides an application of difluorophthalonitrile passivating molecules in perovskite solar cells, suitable for perovskite-based tandem solar cells, comprising at least the following structural devices:

[0027] (1) Organic-inorganic hybrid pure iodine perovskite / crystalline silicon tandem solar cell;

[0028] (2) Organic-inorganic hybrid pure iodine perovskite / copper indium gallium selenide tandem solar cell;

[0029] (3) Organic-inorganic hybrid pure iodine perovskite / organic tandem solar cell;

[0030] (4) Organic-inorganic hybrid pure iodine perovskite / perovskite tandem solar cell;

[0031] The difluorophthalonitrile serves as the interface passivation layer for the perovskite solar cell.

[0032] This invention has at least the following technical effects:

[0033] 1. This invention proposes a method for preparing a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation. By passivating the perovskite surface with a difluorophthalonitrile isopropanol solution, the defects on the surface and grain boundaries of the pure iodine wide-bandgap perovskite film are effectively reduced, thereby improving the quality and interface stability of the perovskite film.

[0034] 2. The cyano group in difluorophthalonitrile can bind to uncoordinated Pb defects on the perovskite surface. The strong electronegativity of fluorine atoms and cyano groups gives the benzene ring a positive charge, which can adsorb charged iodine defects through anion-π interactions, preventing further diffusion of iodine defects and inhibiting ion migration. On the other hand, fluorine atoms can also interact with hydrogen atoms on organic cations (such as formamidinium (FA⁺) and methylamine (MA⁺) in the perovskite through hydrogen bonds, stabilizing organic components and inhibiting their volatilization or decomposition. Fluorine can also form a hydrophobic protective layer on the perovskite surface, improving the environmental stability of perovskite solar cells. Ultimately, this achieves a simultaneous improvement in efficiency and stability. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the perovskite solar cell described in an embodiment of the present invention;

[0036] Figure 2 The JV curve of the perovskite solar cell described in Example 1;

[0037] Figure 3 The JV curve of the perovskite solar cell described in Example 2;

[0038] Figure 4 The JV curve of the perovskite solar cell described in Example 3;

[0039] Figure 5 The JV curve of the perovskite solar cell described in Example 4;

[0040] Figure 6 The JV curve is shown for the perovskite solar cell described in Comparative Example 1. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] This invention proposes a method for fabricating a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation. The cell has the following structure, from bottom to top: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface modification layer, an electron transport layer, a buffer layer, and a metal electrode. The perovskite light-absorbing layer is an organic-inorganic hybrid pure iodine wide-bandgap perovskite. The interface passivation layer is obtained by spin-coating a difluorophthalonitrile isopropanol solution onto the perovskite surface, followed by annealing.

[0043] Example 1:

[0044] This embodiment provides a pure iodine wide-bandgap perovskite solar cell with a bandgap of approximately 1.667 eV. See attached diagram. Figure 1 From bottom to top, it includes: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode.

[0045] The preparation method includes the following steps:

[0046] Step 1: Place the ITO conductive glass in glass cleaning agent, deionized water and isopropanol in sequence for ultrasonic cleaning for 15 minutes, blow it dry with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0047] Step 2: Spin-coat the ethanol solution of Me-4PACz onto the ITO substrate as a hole transport layer, and anneal at 100°C for 10 min.

[0048] Step 3: Prepare 1.2M Cs 0.3 DMA 0.2 MA 0.3 FA 0.2 PbI3 perovskite precursor solution was spin-coated onto the hole transport layer and annealed at 100°C for 10 min to obtain the perovskite light-absorbing layer.

[0049] Step 4: Spin-coat a difluorophthalonitrile isopropanol solution (2 mg / ml) onto the surface of the perovskite light-absorbing layer, and anneal at 100°C for 6 min to obtain an interface passivation layer.

[0050] Step 5: Spin-coat a chlorobenzene solution (20 mg / ml) of PCBM onto the surface of the interface passivation layer as an electron transport layer at a spin-coating speed of 2000 r / min.

[0051] Step 6: Spin-coat a BCP isopropanol solution (0.5 mg / ml) as a buffer layer on the surface of the electron transport layer at a spin-coating speed of 5000 r / min.

[0052] Step 7: Thermally evaporate 80 nm of Ag to serve as a metal electrode.

[0053] Experimental Results: Performance testing of solar cells was conducted, such as... Figure 2 As shown, at AM1.5G, 100mW / cm 2 Under standard light intensity irradiation, the open-circuit voltage of the solar power prepared in this embodiment is 1.157V and the short-circuit current density is 21.76mA cm⁻¹. -2 The fill factor is 84.68%, and the efficiency is 21.31%. Under forward scanning, the open-circuit voltage is 1.149 V, and the short-circuit current density is 21.74 mA cm⁻¹. -2 The fill factor is 82.00%, the efficiency is 20.48%, and the hysteresis factor is 3.9%.

[0054] Example 2:

[0055] This embodiment provides a pure iodine wide-bandgap perovskite solar cell with a bandgap of approximately 1.667 eV. See attached diagram. Figure 1 From bottom to top, it includes: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode.

[0056] The preparation method includes the following steps:

[0057] Step 1: Place the ITO conductive glass in glass cleaning agent, deionized water and isopropanol in sequence for ultrasonic cleaning for 15 minutes, blow it dry with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0058] Step 2: Spin-coat the ethanol solution of Me-4PACz onto the ITO substrate as a hole transport layer, and anneal at 100°C for 10 min.

[0059] Step 3: Prepare 1.2M Cs 0.3 DMA 0.2 MA 0.3 FA 0.2 PbI3 perovskite precursor solution was spin-coated onto the hole transport layer and annealed at 100°C for 10 min to obtain the perovskite light-absorbing layer.

[0060] Step 4: Spin-coat a difluorophthalonitrile isopropanol solution (4 mg / ml) onto the surface of the perovskite light-absorbing layer, and anneal at 100°C for 6 min to obtain an interface passivation layer.

[0061] Step 5: Spin-coat a chlorobenzene solution (20 mg / ml) of PCBM onto the surface of the interface passivation layer as an electron transport layer at a spin-coating speed of 2000 r / min.

[0062] Step 6: Spin-coat a BCP isopropanol solution (0.5 mg / ml) as a buffer layer on the surface of the electron transport layer at a spin-coating speed of 5000 r / min.

[0063] Step 7: Thermally evaporate 80 nm of Ag to serve as a metal electrode.

[0064] Experimental Results: Performance testing of solar cells was conducted, such as... Figure 3 As shown, at AM1.5G, 100mW / cm 2 Under standard light intensity irradiation, the solar power prepared in this embodiment has an open-circuit voltage of 1.170V and a short-circuit current density of 21.55mA / cm² under reverse scanning. -2 The fill factor is 85.71%, and the efficiency is 21.60%. Under forward scanning, the open-circuit voltage is 1.171 V, and the short-circuit current density is 21.52 mA cm⁻¹. -2 The fill factor is 83.02%, the efficiency is 20.91%, and the hysteresis factor is 3.2%.

[0065] Example 3:

[0066] This embodiment provides a pure iodine wide-bandgap perovskite solar cell with a bandgap of approximately 1.667 eV. See attached diagram. Figure 1 From bottom to top, it includes: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode.

[0067] The preparation method includes the following steps:

[0068] Step 1: Place the ITO conductive glass in glass cleaning agent, deionized water and isopropanol in sequence for ultrasonic cleaning for 15 minutes, blow it dry with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0069] Step 2: Spin-coat the ethanol solution of Me-4PACz onto the ITO substrate as a hole transport layer, and anneal at 100°C for 10 min.

[0070] Step 3: Prepare 1.2M Cs 0.3 DMA 0.2 MA 0.3 FA 0.2PbI3 perovskite precursor solution was spin-coated onto the hole transport layer and annealed at 100°C for 10 min to obtain the perovskite light-absorbing layer.

[0071] Step 4: Spin-coat the isopropanol solution (8 mg / ml) of difluorophthalonitrile onto the surface of the perovskite light-absorbing layer, and anneal at 100°C for 6 min to obtain the interface passivation layer.

[0072] Step 5: Spin-coat a chlorobenzene solution (20 mg / ml) of PCBM onto the surface of the interface passivation layer as an electron transport layer at a spin-coating speed of 2000 r / min.

[0073] Step 6: Spin-coat a BCP isopropanol solution (0.5 mg / ml) as a buffer layer on the surface of the electron transport layer at a spin-coating speed of 5000 r / min.

[0074] Step 7: Thermally evaporate 80 nm of Ag to serve as a metal electrode.

[0075] Experimental Results: Performance testing of solar cells was conducted, such as... Figure 4 As shown, at AM1.5G, 100mW / cm 2 Under standard light intensity irradiation, the open-circuit voltage of the solar power prepared in this embodiment is 1.173V and the short-circuit current density is 21.45mA cm⁻¹. -2 The fill factor is 84.91%, and the efficiency is 21.36%. Under forward scanning, the open-circuit voltage is 1.180 V, and the short-circuit current density is 21.43 mA cm⁻¹. -2 The fill factor was 81.44%, the efficiency was 20.58%, and the hysteresis factor was 3.7%.

[0076] Example 4:

[0077] This embodiment provides a pure iodine wide-bandgap perovskite solar cell with a bandgap of approximately 1.667 eV. See attached diagram. Figure 1 From bottom to top, it includes: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode.

[0078] The preparation method includes the following steps:

[0079] Step 1: Place the ITO conductive glass in glass cleaning agent, deionized water and isopropanol in sequence for ultrasonic cleaning for 15 minutes, blow it dry with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0080] Step 2: Spin-coat the ethanol solution of Me-4PACz onto the ITO substrate as a hole transport layer, and anneal at 100°C for 10 min.

[0081] Step 3: Prepare 1.2M Cs 0.3 DMA0.2 MA 0.3 FA 0.2 PbI3 perovskite precursor solution was spin-coated onto the hole transport layer and annealed at 100°C for 10 min to obtain the perovskite light-absorbing layer.

[0082] Step 4: Spin-coat a difluorophthalonitrile isopropanol solution (20 mg / ml) onto the surface of the perovskite light-absorbing layer, and anneal at 100°C for 6 min to obtain an interface passivation layer.

[0083] Step 5: Spin-coat a chlorobenzene solution (20 mg / ml) of PCBM onto the surface of the interface passivation layer as an electron transport layer at a spin-coating speed of 2000 r / min.

[0084] Step 6: Spin-coat a BCP isopropanol solution (0.5 mg / ml) as a buffer layer on the surface of the electron transport layer at a spin-coating speed of 5000 r / min.

[0085] Step 7: Thermally evaporate 80 nm of Ag to serve as a metal electrode.

[0086] Experimental Results: Performance testing of solar cells was conducted, such as... Figure 5 As shown, at AM1.5G, 100mW / cm 2 Under standard light intensity irradiation, the open-circuit voltage of the solar power prepared in this embodiment is 1.158V and the short-circuit current density is 21.53mA cm⁻¹. -2 The fill factor is 84.83%, and the efficiency is 21.15%. Under forward scanning, the open-circuit voltage is 1.150V, and the short-circuit current density is 21.52 mA cm⁻¹. -2 The fill factor is 81.52%, the efficiency is 20.15%, and the hysteresis factor is 4.7%.

[0087] Comparative Example 1:

[0088] This embodiment provides a pure iodine wide-bandgap perovskite solar cell with a bandgap of approximately 1.667 eV. See attached diagram. Figure 1 From bottom to top, it includes: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode.

[0089] The preparation method includes the following steps:

[0090] Step 1: Place the ITO conductive glass in glass cleaning agent, deionized water and isopropanol in sequence for ultrasonic cleaning for 15 minutes, blow it dry with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0091] Step 2: Spin-coat the ethanol solution of Me-4PACz onto the ITO substrate as a hole transport layer, and anneal at 100°C for 10 min.

[0092] Step 3: Prepare 1.2M Cs 0.3 DMA 0.2 MA 0.3 FA 0.2 PbI3 perovskite precursor solution was spin-coated onto the hole transport layer and annealed at 100°C for 10 min to obtain the perovskite light-absorbing layer.

[0093] Step 4: Spin-coat a chlorobenzene solution (20 mg / ml) of PCBM onto the surface of the perovskite light-absorbing layer as an electron transport layer at a spin-coating speed of 2000 r / min.

[0094] Step 5: Spin-coat a BCP isopropanol solution (0.5 mg / ml) as a buffer layer on the surface of the electron transport layer at a spin-coating speed of 5000 r / min.

[0095] Step 6: Thermally evaporate 80 nm of Ag to serve as a metal electrode.

[0096] Experimental Results: Performance testing of solar cells was conducted, such as... Figure 6 As shown, at AM1.5G, 100mW / cm 2 Under standard light intensity irradiation, the open-circuit voltage of the solar power prepared in this embodiment is 1.123V and the short-circuit current density is 21.45mA cm⁻¹. -2 The fill factor is 83.21%, and the efficiency is 20.04%. Under forward scanning, the open-circuit voltage is 1.114 V, and the short-circuit current density is 21.33 mA cm⁻¹. -2 The fill factor is 76.63%, the efficiency is 18.20%, and the hysteresis factor is 9.2%.

[0097] In summary, a method for fabricating a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation involves passivating the perovskite surface with an isopropanol solution of difluorophthalonitrile. The cyano groups in difluorophthalonitrile can bind to uncoordinated Pb defects on the perovskite surface. The strong electronegativity of fluorine atoms and cyano groups gives the benzene ring a positive charge, which can adsorb charged iodine defects through anion-π interactions, preventing further diffusion of iodine defects, inhibiting ion migration, and alleviating device hysteresis. On the other hand, fluorine atoms can also interact with hydrogen atoms on organic cations (such as formamidinium (FA⁺) and methylamine (MA⁺) in the perovskite through hydrogen bonds, stabilizing organic components and inhibiting their volatilization or decomposition. Fluorine can also form a hydrophobic protective layer on the perovskite surface, improving the environmental stability of the perovskite solar cell. Ultimately, this method achieves a simultaneous improvement in efficiency and stability.

[0098] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The transparent conductive substrate, hole transport layer, perovskite light-absorbing layer, interface passivation layer, electron transport layer, buffer layer, and metal electrode material in the embodiments can be selected within the scope defined by the technical solution of the present invention. Furthermore, the specific conditions in the ultrasonication, spin-coating, annealing, and other steps involved in the preparation method can also be selected within the scope defined by the technical solution of the present invention, all of which can achieve the expected effects of the present invention. It should be clearly stated that any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for fabricating a pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation, characterized in that, The perovskite solar cell structure, stacked from bottom to top, comprises: a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an interface passivation layer, an electron transport layer, a buffer layer, and a metal electrode; and includes the following steps: Step 1: Treatment of transparent conductive substrate; Step 2: Spin-coating a hole transport layer onto a transparent conductive substrate; Step 3: Spin-coat the prepared hole transport layer with perovskite precursor solution, induce crystallization using antisolvent, and then anneal to obtain the perovskite light-absorbing layer. Step 4: Spin-coat difluorophthalonitrile solution onto the perovskite light-absorbing layer, and then anneal to obtain an interface passivation layer; Step 5: Fabricate an electron transport layer on the interface passivation layer; Step 6: Prepare a buffer layer on the electron transport layer; Step 7: Evaporate and deposit a metal electrode on the buffer layer; The interface passivation layer is obtained by spin-coating a difluorophthalonitrile isopropanol solution onto a perovskite light-absorbing layer followed by annealing. The structural formula of the interface passivation material difluorophthalonitrile is: 。 2. The preparation method according to claim 1, characterized in that, The transparent conductive substrate in step 1 is selected from either FTO conductive glass or ITO conductive glass.

3. The preparation method according to claim 1, characterized in that, The hole transport layer in step 2 is any one or more of the following materials: nickel oxide, [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphoric acid, [2-[9H-carbazole-9-yl]ethyl]phosphonic acid, and [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid; The hole transport layer solution is prepared as follows: when the selected hole transport layer material is an organic monolayer, the hole transport layer material is dissolved in an alcohol solvent to obtain a solution with a concentration of 0.3-1.0 mg / mL; the spin coating parameters are 3000-5000 rpm, spin coating time is 20-30 s, annealing temperature is 90-100℃, and annealing time is 5-10 min.

4. The preparation method according to claim 1, characterized in that, The perovskite in step 3 is a pure iodine wide-bandgap perovskite with an organic-inorganic hybrid structure, with a bandgap of 1.65-1.7 eV; the perovskite material is selected from one of CsI, MAI, FAI, DMAI, RbI, or PbI2; the antisolvent is any one or more of ethyl acetate, methyl acetate, chlorobenzene, anisole, or diethyl ether. The perovskite precursor solution is prepared by dissolving a wide-bandgap perovskite light-absorbing layer material in a mixed solvent of DMF and NMP under an inert atmosphere, with a concentration of 1.0-1.5M; the spin-coating parameters are 2000-4000 rpm and the spin-coating time is 20-40 s; the annealing temperature is 90-110℃ and the annealing time is 5-20 min.

5. The preparation method according to claim 1, characterized in that, In step 4, the concentration of the interfacial passivation material difluorophthalonitrile is 2-20 mg / ml, and the solvent is one or more of isopropanol and methanol; the annealing temperature is 80-100℃, the annealing time is 5-10 min, and the spin coating parameters are 3000-5000 rpm and the spin coating time is 20-40 s.

6. The preparation method according to claim 1, characterized in that, The electron transport layer in step 5 is any one or two of PC61BM and C60 materials.

7. The preparation method according to claim 1, characterized in that, The buffer layer in step 6 can be either BCP or SnOx.

8. The preparation method according to claim 1, characterized in that, The metal electrode in step 7 is made of any one of Au, Ag, or Cu, and has a thickness of 80-120 nm.

9. A pure iodine wide-bandgap perovskite solar cell based on difluorophthalonitrile passivation, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of a difluorophthalonitrile passivating molecule in perovskite solar cells, characterized in that, Suitable for perovskite-based tandem solar cells, including at least the following structural components: (1) Organic-inorganic hybrid pure iodine perovskite / crystalline silicon tandem solar cell; (2) Organic-inorganic hybrid pure iodine perovskite / copper indium gallium selenide tandem solar cell; (3) Organic-inorganic hybrid pure iodine perovskite / organic tandem solar cell; (4) Organic-inorganic hybrid pure iodine perovskite / perovskite tandem solar cell; The difluorophthalonitrile serves as the interface passivation layer for the perovskite solar cell.

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