Double-spacer cation formal structure quasi-two-dimensional perovskite solar cell and method

Abstract

The invention provides a quasi-two-dimensional perovskite solar cell with a double-spacer cation formal structure and a method. Double spacer cations are adopted for co-nucleation to form a mixed 2D phase containing two spacer cations. The special low-dimensional perovskite has the remarkable advantages that firstly, rigid thiophene ring positive ions and flexible alkyl positive ions are mixed, and a large amount of residual strain in the thin film is successfully released, so that the surface appearance of the thin film is obviously improved; secondly, the distribution of the n phase of perovskite is optimized, and reverse ordered phase distribution which is most beneficial to exciton dissociation and carrier transportation is successfully established through p-n junctions formed in the thin film from top to bottom; and thirdly, more matched energy level alignment between the perovskite layer and the transmission layer is realized by adjusting the perovskite energy level distribution. The above factors finally cause the photoelectric conversion efficiency (PCE) of the double-spacer cation RP PSCs to reach 18.67%, and the problems existing in the single-spacer cation perovskite are successfully solved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and particularly to a double-spaced cation formal structure quasi-two-dimensional perovskite solar cell and method. Background Art

[0002] Perovskite solar cells (PSCs) have attracted extensive attention due to their high-efficiency optoelectronic conversion performance. On the basis of the perovskite structure, the introduction of the RP phase has injected new vitality into the development of solar cells. RP-phase perovskite solar cells have become one of the research hotspots in recent years due to their superior optoelectronic properties and structural design. The chemical formula of Q-2D RP perovskite is generally (R-NH 3 ) 2 A n-1 MnX 3n+1 (n = 1, 2, 3,...), where R-NH 3 is a bulky amino spacer cation, A, M, and X are small-valence organic cations, divalent metal cations, and halide anions respectively, and n is the number of layers of corner-sharing octahedra [MX6] 4- . The superior stability of RPPs mainly stems from the hydrophobic organic spacer layer, which can protect the inorganic layer [MX6] 4- from water molecule penetration. Therefore, the smaller the n value, the higher the humidity stability. At the same time, the bulky spacer layer forms a quantum well structure, and the resulting quantum confinement effect leads to a large exciton binding energy and poor transport of photo-generated carriers, which greatly limits the power conversion efficiency (PCE) of photovoltaic cells. At the same time, the quantum confinement effect can expand the optical bandgap, and the optical bandgaps corresponding to 2D with different n values are different: the smaller the n value, the greater the quantum confinement effect and the larger the optical bandgap. The 2D phase in the perovskite thin film is not composed of a single n value, but a coexistence of low-n and high-n phases. Therefore, in order to extend the absorption spectrum, obtain efficient two-dimensional PSCs, it is crucial to expand the diversity of spacer cations and regulate the influence of the distribution of different n values of the perovskite phase 2D on the thin film and device performance.

[0003] In the initial research of Q-2D RPPs, researchers mainly focused on the layered structure with large organic spacer cations, such as butylammonium (BA + ) and phenethylammonium (PEA + ), and the corresponding solar cells showed impressive water stability, but had low PCEs due to the intrinsically insulating organic spacer layer. To improve charge transport and enhance performance, researchers reduced the size of the organic spacer cation, such as using isobutylammonium (iso-BA + ) and propylammonium (PA +), can improve the transport efficiency of electrons and holes and reduce the quantum well barrier. Further research shows that introducing novel organic spacer cations, such as 3-bromobenzylammonium (3-BBA + ), and 2-thiophenemethylammonium (ThMA + ), can generate high-quality RPP films. The introduction of these organic cations brings obvious performance improvements, enabling further enhancement of the PCE of RPPs. However, current research has focused on preparing quasi-two-dimensional perovskites using a single type of spacer cation, and the distribution of the perovskite n-phase has not been significantly optimized.

[0004] Traditional Q-2D perovskites usually use a single type of spacer cation, and its chemical formula is generally (R-NH 3 ) 2 A n- 1 M n X 3n+1 (n = 1, 2, 3,...), where R-NH 3 is a bulky amino spacer cation, A, M, and X are small-valence organic cations, divalent metal cations, and halide anions respectively, and n is the number of layers of corner-sharing octahedra [MX 6 4- . So far, most efficient Q-2D PSCs have been prepared by the thermal spin-coating method. First, the perovskite precursor material is fully dissolved in a polar solvent to form a homogeneous perovskite precursor solution. Subsequently, the precursor solution is uniformly coated on the substrate through the spin-coating technique. Finally, through thermal annealing treatment, the residual solvent in the perovskite film evaporates, thus forming a high-quality perovskite film.

[0005] In this case, the low n-value phase is enriched at the bottom of the perovskite film, while the top of the film is enriched with a three-dimensional-like phase, that is, the n-value of the two-dimensional perovskite gradually increases from the bottom to the surface of the film in the vertical direction. We call this n-value distribution a forward-ordered phase distribution. However, the three-dimensional-like phase aggregated at the top of the film is susceptible to humidity, and the stability of the Q-2D perovskite film with a forward gradient phase distribution will be significantly affected. Summary of the Invention

[0006] Traditional Q-2D perovskites usually use a single type of spacer cation. Thiophene-based organic amine spacer cations (such as TMA + ) belong to aromatic compounds and have rigid characteristics, which easily cause residual strain inside the perovskite film, microscopically affecting the film morphology, crystal crystallinity, and crystallization orientation; macroscopically, it will cause cracks on the surface of the perovskite film, thereby affecting the film stability and device performance. Therefore, releasing the internal residual strain of the film with TMA as the spacer cation is the key problem to be solved in this invention. ​

[0007] So far, most efficient Q-2D PSCs have been prepared by thermal spin coating. In this case, the bottom of the perovskite film is enriched with a low-n phase, while the top of the film is enriched with a three-dimensional-like phase, that is, the n value of the two-dimensional perovskite gradually increases from the bottom to the surface of the film in the vertical direction. We call this n-value distribution a forward-ordered phase distribution. However, the three-dimensional-like phase aggregated at the top of the film is vulnerable to humidity, and the stability of the Q-2D perovskite film with a forward gradient phase distribution will be significantly affected. For the reverse-ordered phase distribution, the small-n phase at the top of the film can effectively hinder the intrusion of water and oxygen into the perovskite interior, which is more conducive to improving the device stability. In addition, for the reverse phase distribution, the p-n junction formed from top to bottom in the film, under the action of the built-in electric field, electrons are transported from the small-n phase at the top to the large-n phase at the bottom, and then collected by the ITO / electron transport layer, which matches the planar normal device structure and is beneficial to improving charge transport and extraction in Q-2D PSCs. Therefore, preparing a reverse-ordered phase distribution is crucial for the normal structure and is the key problem to be solved in the present invention.

[0008] In view of the above problems in the prior art, the present application proposes a dual-spacer cation normal structure quasi-two-dimensional perovskite solar cell, where the bottom of the perovskite film is enriched with a three-dimensional-like phase, the top of the perovskite film is enriched with a low-n phase, and a p-n junction is formed from top to bottom in the film. Under the action of the built-in electric field, electrons are transported from the low-n phase at the top to the high-n phase at the bottom, and then collected by the electron transport layer.

[0009] In one embodiment, the molecular formula of the dual-spacer cation normal structure quasi-two-dimensional perovskite is (TMA 1-x AA x ) 2 FA 4 Pb 5 I 16 , where TMA + represents a rigid thiophene ring cation, AA + represents a flexible alkyl cation, FA represents a formamidinium cation, x represents the proportion of the second spacer cation, and 1 > x > 0. In one embodiment, x = 20%.

[0010] The present application also relates to a method for preparing a dual-spacer cation normal structure quasi-two-dimensional perovskite solar cell, including the following steps:

[0011] Step S1, prepare (TMA 0.8 AA 0.2 ) 2 FA 4 Pb 5 I 16The precursor perovskite, where TMA is 2-thiophenemethylammonium and AA is pentylamine; the prepared precursor perovskite is dissolved in the mixed solvent DMF:DMSO to obtain a perovskite precursor solution; the perovskite precursor solution is heated, stirred and then filtered;

[0012] Step S2, dilute the SnO 2 nanoparticle colloid and spin-coat it on an ITO glass substrate; after spin-coating, perform thermal annealing to obtain ITO / SnO 2 electron transport layer;

[0013] Step S3, spin-coat the perovskite precursor solution on the ITO / SnO 2 electron transport layer to obtain an ITO / SnO 2 / perovskite substrate;

[0014] Step S4, spin-coat the Spiro-OMeTAD solution on the ITO / SnO 2 / perovskite substrate to obtain a perovskite thin film;

[0015] Step S5, scrape a blank strip about 1-2 mm wide perpendicular to the ITO direction at the edge of the perovskite thin film, and fabricate an Ag electrode by vacuum evaporation.

[0016] In one embodiment, prepare the (TMA 2 AA 0.8 ) 0.2 FA 2 Pb 4 I 5 I 16 precursor perovskite according to the ratio of PbI

[0017] :FAI:TMAI:AAI = 5:4:1.6:0.4.

[0018] In one embodiment, in step S2, the pretreatment of the ITO glass substrate includes:

[0019] a) Use a lint-free cloth dipped in dishwashing detergent water to scrub the ITO glass; ITO: indium tin oxide;

[0020] b) Immerse the cleaned ITO glass in dishwashing detergent water, absolute ethanol, acetone solution, and absolute ethanol successively and perform ultrasonic treatment;

[0021] c) Immerse it in absolute ethanol and soak for later use;

[0022] d) Before use, dry the surface with clean air and place it in an ultraviolet ozone instrument for hydrophobicity improvement treatment.

[0023] In one embodiment, ITO / SnO2 The preparation method of the electron transport layer includes:

[0024] a) Dilute the SnO2 nanoparticle colloid with deionized water to 2.5%;

[0025] b) Place ITO on a spin coater and drop 30 μL of SnO 2 colloid;

[0026] c) Set the spin coater to a rotation speed of 4000 rpm and a spin coating time of 30 s for spin coating;

[0027] d) After spin coating, place it on a hot plate at 180 °C for thermal annealing for 5 min.

[0028] In one embodiment, the preparation method of the ITO / SnO 2 / perovskite substrate includes:

[0029] a) Place the ITO / SnO 2 substrate on a spin coater and drop 30 μL of the perovskite precursor solution;

[0030] b) Perform spin coating through a two-step spin coating process, including 1000 rpm for 5 s and 4000 rpm for 20 s; and at the 10th second of the second step, slowly and evenly drop 130 μL of IPA on the rotating substrate, where IPA is the antisolvent isopropyl alcohol;

[0031] c) After spin coating, place it on a hot plate at 105 °C for thermal annealing for 30 min.

[0032] In one embodiment, the preparation method of the perovskite thin film includes:

[0033] a) Prepare a Spiro-OMeTAD solution by mixing 72 mg of Spiro-OMeTAD, 17.5 μL of a Li-TFSI / ACN solution with a concentration of 520 mg / 1 mL, 19 μL of a FK209 / ACN solution with a concentration of 200 mg / 1 mL, and 29 μL of tBP in 1 mL of chlorobenzene;

[0034] b) Place the ITO / SnO 2 / perovskite substrate on a spin coater and drop 30 μL of the Spiro-OMeTAD solution;

[0035] c) Set the spin coater to a rotation speed of 4000 rpm and a spin coating time of 30 s for spin coating.

[0036] The present invention introduces the concept of organic spacer cation engineering, and introduces pentylamine (AA + ) as the second spacer cation, in the standard piece (TMA) 2FA 4 Pb 5 I 16 Based on quasi-two-dimensional perovskites, double-spacing cation quasi-two-dimensional perovskites (TMA 1-x AA x ) with improved efficiency were prepared. 2 FA 4 Pb 5 I 16 (x = 20%) solar cells. Due to the mixing of rigid thiophene ring cations (TMA + ) and flexible alkyl cations (AA + ), a large amount of residual strain inside the thin film was successfully released, thus significantly improving the surface morphology of the thin film. Moreover, the distribution of the perovskite n-phase was optimized, and an inverse-ordered phase distribution that is most favorable for exciton dissociation and carrier transport was successfully established, which is more conducive to the improvement of device stability. The p-n junction formed from top to bottom in the thin film adjusts the energy level distribution of the perovskite, achieving a more matched energy level alignment between the perovskite layer and the transport layer. The above factors ultimately led to a power conversion efficiency (PCE) of 18.67% for the double-spacing cation RP PSCs, which is higher than that of the corresponding devices with traditional single-spacing cations (17.15%).

[0037] To optimize the distribution of the Q-2D perovskite n-phase, the present invention uses the "antisolvent method" to prepare perovskite. First, the perovskite precursor material is fully dissolved in a polar solvent to form a uniform perovskite precursor solution. Subsequently, through the antisolvent spin-coating technique, the precursor solution is uniformly coated on the substrate. During the spin-coating of perovskite, the antisolvent is added dropwise at a constant speed. The antisolvent method is a preparation method that uses the principle of mass transfer to transfer the perovskite precursor from the organic phase to the inorganic phase by adding two immiscible solvents. Among them, the perovskite precursor in the organic phase will precipitate out crystals due to supersaturation to form a thin film. The basic process of the antisolvent method can be divided into three stages: adding a large amount of organic solvent, that is, the organic phase of the solution. At this time, the perovskite precursor will dissolve in the organic solvent and reach a fully saturated state; the next step is to suddenly add the antisolvent, and the antisolvent will displace the organic solvent in the organic phase, causing the precursor to precipitate due to supersaturation to form a perovskite crystal thin film. Finally, after thermal annealing treatment, the residual solvent in the perovskite thin film volatilizes, thus preparing a quasi-2D perovskite thin film with large grains, high density, and few defects.

[0038] The above technical features can be combined in various suitable ways or replaced by equivalent technical features as long as the purpose of the present invention can be achieved.

[0039] A double-spacing cation formal structure quasi-two-dimensional perovskite solar cell and method provided by the present invention have at least the following beneficial effects compared with the prior art:

[0040] The double-spaced cationic Q-2D perovskite prepared by the present invention successfully releases a large amount of residual strain inside the thin film, obtaining a dense, uniform, and pinhole-free Q-2D perovskite thin film; at the same time, a reverse-ordered phase distribution that is most conducive to exciton dissociation and carrier transport is successfully established, which matches the planar formal device structure, is beneficial to improving charge transport and extraction in Q-2D PSCs, and realizes the improvement of the photovoltaic performance of the device. The open-circuit voltage is increased from 1.12 V to 1.17 V, and the short-circuit current density is increased from 21.12 mA / cm 2 to 22.41 mA / cm 2 , and the power conversion efficiency is increased from 17.15% to 18.67%. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be described in more detail below based on embodiments and with reference to the drawings. Among them:

[0042] Figure 1 are the device structure diagrams of Embodiment 1 and Embodiment 2

[0043] Figure 2 are the current density-voltage (J-V) curve graphs of Embodiment 1 and Embodiment 2

[0044] Figure 3 are the scanning electron microscope (SEM) graphs of Embodiment 1 and Embodiment 2

[0045] Figure 4 are the atomic force microscope (AFM) height graphs of Embodiment 1 and Embodiment 2

[0046] Figure 5 are the grazing incidence wide-angle X-ray scattering (GIWAXS) graphs of Embodiment 1 and Embodiment 2

[0047] Figure 6 are the GIXRD patterns of Embodiment 1 and Embodiment 2 at different instrument tilt angles.

[0048] Figure 7 are the linear fitting curves of 2θ-sin 2 (Ψ) of Embodiment 1 and Embodiment 2. DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention will be further described below with reference to the drawings.

[0050] Embodiment 1:

[0051] (1) Preparation of Q-2D perovskite precursor solution

[0052] The concentration of the Q-2D perovskite precursor solution used in the present invention is 1 mmol / mL.

[0053] a) Prepare (TMA) perovskite with a ratio of PbI 2 : FAI: TMAI = 5:4:2 (TMA) 2 FA 4 Pb 5 I 16 -based perovskite,

[0054] where TMA is 2-thienylmethylammonium;

[0055] b) Dissolve the prepared perovskite in a mixed solvent of DMF: DMSO = 8:2;

[0056] c) Stir the perovskite precursor solution overnight on a magnetic stirring hot plate (60 °C);

[0057] d) Filter using a PTFE membrane (0.2 μm);

[0058] (2) Pretreatment of ITO glass substrate

[0059] a) Rub the ITO glass with a lint-free cloth dipped in dishwashing detergent water; ITO: indium tin oxide;

[0060] b) Immerse the cleaned ITO glass in dishwashing detergent water, absolute ethanol, acetone solution, and absolute ethanol successively and ultrasonicate for 15 minutes each step;

[0061] c) Immerse in absolute ethanol for standby;

[0062] d) Before use, dry the surface with clean air and place it in a UV ozone (UVO) instrument for hydrophobicity improvement treatment for 20 minutes.

[0063] (3) Preparation of electron transport layer

[0064] a) Dilute the SnO 2 nanoparticle colloid to 2.5% with deionized water;

[0065] b) Place the ITO on a spin coater and drop 30 μL of SnO 2 colloid;

[0066] c) Set the spin coater to a rotation speed of 4000 rpm and a spin coating time of 30 s for spin coating;

[0067] d) After spin coating, perform thermal annealing on a hot plate at 180 °C for 5 minutes.

[0068] (4) Preparation of quasi-2D perovskite film

[0069] a) Place the ITO / SnO 2The substrate is placed on a spin coater, and 30 μL of the perovskite precursor solution is dropped;

[0070] b) Spin coating is carried out through a two-step spin coating process, including 5 s at 1000 rpm and 20 s at 4000 rpm. And at the 10th second of the second step, 130 μL of IPA is slowly and evenly dropped onto the rotating substrate. IPA is the antisolvent isopropyl alcohol;

[0071] c) After spin coating, it is placed on a hot plate at 105 °C for thermal annealing for 30 min.

[0072] (5) Preparation of the hole transport layer

[0073] a) 72 mg of Spiro-OMeTAD, 17.5 μL of Li-TFSI / ACN solution (520 mg / 1 mL),

[0074] 19 μL of FK209 / ACN solution (200 mg / 1 mL) and 29 μL of tBP are mixed in 1 mL of chlorobenzene to prepare the Spiro-OMeTAD solution;

[0075] b) The ITO / SnO 2 / perovskite substrate is placed on a spin coater, and 30 μL of the Spiro-OMeTAD solution is dropped;

[0076] c) The spin coater is set at a rotation speed of 4000 rpm and a spin coating time of 30 s for spin coating.

[0077] (6) Preparation of the Ag electrode

[0078] a) A blank strip about 1 - 2 mm wide is scraped perpendicular to the ITO direction at the edge of the perovskite film;

[0079] b) The Ag electrode is prepared by vacuum evaporation at a speed of 100 nm.

[0080] Example 2:

[0081] (1) Preparation of the Q-2D perovskite precursor solution

[0082] According to the ratio of PbI 2 : FAI: TMAI: AAI = 5:4:1.6:0.4 to prepare the (TMA 0.8 AA 0.2 ) 2 FA 4 Pb 5 I 16 -based perovskite, and the remaining operations are the same as in Example 1.

[0083] (2) Pretreatment of the ITO glass substrate

[0084] Same as Example 1.

[0085] (3) Preparation of the electron transport layer

[0086] Same as Example 1.

[0087] (4) Preparation of the Q-2D perovskite film

[0088] Same as Example 1.

[0089] (5) Preparation of the hole transport layer

[0090] Same as Example 1.

[0091] (6) Preparation of the Ag electrode

[0092] Same as Example 1.

[0093] The structures of the Q-2D PSCs fabricated in these two examples are both as Figure 1 shown, except that the perovskite films are different. Example 1 is a traditional single-spacer cation-based perovskite, and Example 2 is a double-spacer cation-based perovskite. The current density-voltage (J-V) tests were performed on the devices fabricated in this example, and the test results are as Figure 2 shown. The open-circuit voltage (V oc ), short-circuit current density (J sc ), fill factor (FF), and power conversion efficiency (PCE) of the device in Example 1 were 1.12 V, 21.12 mA / cm 2 , 72.5%, and 17.15%, respectively. The V oc , J sc , FF, and PCE of the device in Example 2 were improved to 1.17 V, 22.41 mA / cm 2 , 71.2%, and 18.67%, respectively. Figure 3 Fig. 47 is the scanning electron microscope (SEM) images of the films in Example 1 and Example 2. The surface of the film in Example 1 presents micron-sized large grains and many large pores. In contrast, the surface of the film in Example 2 shows a dense, uniform, and pinhole-free surface morphology, and there are white rod-like small particles at the grain boundaries. Figure 4 Fig. 48 is the corresponding AFM height image. Compared with the root mean square (RMS) roughness of the film in Example 1 (45.5 nm), the RMS roughness of the film in Example 2 is much smaller, being 13.4 nm, which is beneficial to the interfacial contact between the perovskite and the hole transport layer (HTL).

[0094] To further evaluate the crystal growth orientation of the quasi-2D perovskite with different spacer cations, grazing incidence wide-angle X-ray scattering (GIWAXS) measurements were performed on the quasi-2D perovskite films fabricated in this example ( Figure 5), in Example 1 and Example 2, the thin films showed sharp and discrete Bragg spots, indicating that these films had a high degree of crystal orientation. However, through careful analysis of the diffraction rings at , in Example 1, the thin film showed many discrete Bragg spots, which meant the multi-directional growth of perovskite crystals, while in Example 2, the thin film showed only one discrete Bragg spot along the q z direction, indicating that the crystals had good vertical growth on the substrate, thus forming an effective charge transport channel in the quasi-2D PSCs.

[0095] Since the single-spacer cation TMA + is rigid and easily causes lattice strain inside the thin film, resulting in the generation of holes in the perovskite thin film. After introducing the flexible chain-like AA + , it is very likely to release the lattice stress, reduce the generation of holes, and make the thin film denser and flatter. Therefore, we studied the effect of the introduction of AA + on the lattice strain of the perovskite thin film. We used grazing incidence X-ray diffraction (GIXRD) technology to estimate the residual strain of the Q-2D perovskite thin film. Specifically, we analyzed the (111) characteristic peak of the perovskite. Figure 6 shows the GIXRD spectra of the thin films of Example 1 and Example 2 at different instrument tilt angles Ψ. For the thin film of Example 1, as Ψ increased from 0° to 50°, the position of the characteristic peak gradually shifted to a larger angle, indicating that the interplanar distance d (111) gradually decreased, indicating that the single-spacer cation-based thin film was under greater compressive strain. For the thin film of Example 2, as the Ψ angle increased, the position of the characteristic peak remained almost unchanged, indicating that its residual stress was negligible. Figure 7 shows the linear fitting of 2θ-sin 2 (Ψ) of the two thin films. The positive slope of the fitting line indicates the presence of compressive stress in the perovskite thin film. Based on the thin film of Example 2 (slope

[0096] = 0.00513) showing a significantly smaller slope than the thin film of Example 1 (slope = 0.23677), it indicates that the internal residual stress in the thin film was significantly reduced after introducing the second spacer cation.

[0097] The traditional single-spacer cation perovskite (TMA) 2 FA 4 Pb 5 I 16 , the single-spacer cation used is a thiophene-based organic amine spacer cation, which has a rigid characteristic and is easily prone to generating residual strain inside the perovskite thin film, microscopically affecting the morphology of the thin film, the crystallinity and crystallization orientation of the crystals; and (TMA) 2 FA 4 Pb5 I 16 The bottom of the perovskite film is enriched with a low-n phase, while the top of the film is enriched with a quasi-three-dimensional phase. This n-value distribution is a positively ordered phase distribution. However, the quasi-3D phase aggregated at the top of the film is vulnerable to humidity, and the stability of the Q-2D perovskite film with a positive gradient phase distribution will be significantly affected.

[0098] The present invention uses dual-spacer cations to co-nucleate to form a hybrid 2D phase containing two spacer cations. This special low-dimensional perovskite brings some significant advantages: First, by mixing rigid thiophene ring cations and flexible alkyl cations, a large amount of residual strain inside the film is successfully released, thus significantly improving the film surface morphology. Second, the distribution of the perovskite n-phase is optimized, and a p-n junction formed from top to bottom in the film successfully establishes an inversely ordered phase distribution that is most conducive to exciton dissociation and carrier transport. Third, by adjusting the perovskite energy level distribution, a more matched energy level alignment between the perovskite layer and the transport layer is achieved. The above factors ultimately lead to a power conversion efficiency (PCE) of 18.67% for the dual-spacer cation RP PSCs, successfully solving the problems existing in single-spacer cation perovskites.

[0099] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A quasi-two-dimensional perovskite solar cell with a double-spacer cation formal structure, characterized in that: The bottom of the perovskite film is enriched with a 3D-like phase, and the top of the perovskite film is enriched with a low-n-value phase. Under the action of the built-in electric field, the pn junction formed from top to bottom in the film transmits electrons from the low-n-value phase at the top to the high-n-value phase at the bottom, and then is collected by the electron transport layer.

2. The double-spacer cation formal structure quasi-two-dimensional perovskite solar cell according to claim 1, characterized in that: The molecular formula of the double-spaced cation formal structure quasi-two-dimensional perovskite is (TMA 1-x AA x )2FA4Pb5I 16 , where TMA + Represents a rigid thiophene ring cation, AA + represents a flexible alkyl cation, FA + represents the carboxamidinium cation, x represents the proportion of the second-position intervening cation, 1>x>0.

3. The double-spacer cation formal structure quasi-two-dimensional perovskite solar cell according to claim 2, characterized in that: x＝20％。 4. A method for preparing the double-spacer cation formal structure quasi-two-dimensional perovskite solar cell according to claim 1, characterized in that: The following steps are involved: Step S1, configuration (TMA 0.8 AA 0.2 )2FA4Pb5I 16 The base perovskite, TMA is 2-thienylmethylammonium, and AA is amylamine; the prepared base perovskite is dissolved in a mixed solvent DMF:DMSO to obtain a perovskite precursor solution; the perovskite precursor solution is heated and stirred and then filtered; Step S2, diluting the SnO2 nanoparticle colloid and spin coating it on the ITO glass substrate; after the spin coating is completed, performing thermal annealing to obtain an ITO / SnO2 electron transport layer; Step S3, spin coating the perovskite precursor solution on the ITO / SnO2 electron transport layer to obtain an ITO / SnO2 / perovskite substrate; Step S4, spin-coating the Spiro-OMeTAD solution on the ITO / SnO2 / perovskite substrate to obtain a perovskite film; Step S5, scraping a blank strip about 1-2 mm wide at the edge of the perovskite film perpendicular to the ITO direction, and preparing an Ag electrode by vacuum evaporation.

5. The method according to claim 4, characterized in that According to the ratio of PbI2:FAI:TMAI:AAI=5:4:1.6:0.4 (TMA 0.8 AA 0.2 )2FA4Pb5I 16 Based perovskite.

6. The method according to claim 4, characterized in that Mixed solvent: DMF:DMSO=8:

2.

7. The method according to claim 4, characterized in that In step S2, the pretreatment of the ITO glass substrate includes: a) Use a dust-free cloth dipped in detergent water to scrub the ITO glass; ITO: indium tin oxide; b) soaking the cleaned ITO glass in detergent water, anhydrous ethanol, acetone solution, and anhydrous ethanol in sequence and performing ultrasonic treatment; c) soaking in anhydrous ethanol for later use; d) Before use, dry the surface with clean air and place it in a UV ozone analyzer for hydrophobicity improvement treatment.

8. The method according to claim 4, characterized in that The preparation method of the ITO / SnO2 electron transport layer comprises: a) diluting SnO2 nanoparticle colloid to 2.5% with deionized water; b) Place ITO on a spin coater and drop 30 μL of SnO2 colloid; c) setting the spin coater to a speed of 4000 rpm and a spin coating time of 30 s for spin coating; d) After spin coating, the film was placed on a hot plate at 180° C. for thermal annealing for 5 min.

9. The method according to claim 4, characterized in that The preparation method of ITO / SnO2 / perovskite substrate includes: a) Place the ITO / SnO2 substrate on a spin coater and drop 30 μL of the perovskite precursor solution; b) performing spin coating by a two-step spin coating process, including 1000 rpm for 5 s and 4000 rpm for 20 s; and at 10 seconds in the second step, slowly and evenly dropping 130 μL of IPA on the rotating substrate, where IPA is the anti-solvent isopropanol; c) After spin coating, the plate was placed on a hot plate at 105° C. for thermal annealing for 30 min.

10. The method according to claim 4, characterized in that The method for preparing the perovskite film includes: a) 72 mg of Spiro-OMeTAD, 17.5 μL of a 520 mg / 1 mL Li-TFSI / ACN solution, 19 μL of a 200 mg / 1 mL FK209 / ACN solution, and 29 μL of tBP were mixed in 1 mL of chlorobenzene to prepare a Spiro-OMeTAD solution; b) Place the ITO / SnO2 / perovskite substrate on a spin coater and drop 30 μL of Spiro-OMeTAD solution; c) The spin coater was set to a rotation speed of 4000 rpm and a spin coating time of 30 s for spin coating.

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