Method for regulating wide-band gap perovskite crystallization through CsPb2Br5 and laminated photovoltaic application thereof

Abstract

The invention discloses a method for regulating wide-band gap perovskite crystallization through CsPb2Br5 and laminated photovoltaic application thereof, and particularly relates to the field of photoelectric materials and devices. Comprising the following steps: preparing a CsPb2Br5 nanosheet; the preparation method comprises the following steps: dissolving cesium iodide, formamidine hydriodate, lead iodide, lead bromide and CsPb2Br5 nanosheets in a solvent to obtain a perovskite precursor solution; wherein the perovskite precursor solution comprises two phases, namely a Cs0.2 FA < 0.8 > PbI < 1.8 > Br < 1.2 > perovskite precursor complex and a CsPb2Br < 5 >; and preparing the perovskite precursor solution into a perovskite thin film of the solar cell to obtain the solar cell. The crystal can be guided to uniformly grow along the vertical direction, the crystal boundary and defects are reduced, the crystal structure is optimized, and the stability and uniformity of the film are enhanced; and photo-induced halogen phase separation and defect formation can be inhibited, so that the photoelectric property and long-term stability of the perovskite thin film are improved.

Description

Technical Field

[0001] This application relates to the field of optoelectronic materials and devices, and particularly to a method for regulating the crystallization of wide-bandgap perovskite by CsPb 2 Br 5 and its application in tandem photovoltaics. Background Art

[0002] Wide-bandgap perovskite has lower cost-effectiveness and unique optoelectronic properties compared with traditional wide-bandgap semiconductors, and can be used as a potential substitute for traditional wide-bandgap inorganic semiconductors to solve the problems they face and achieve disruptive breakthroughs in related applications. Since wide-bandgap perovskite has a strong absorption ability for high-energy photons, making it transparent to some visible light and all infrared light, single-junction solar cells based on wide-bandgap perovskite can be used in special applications such as building-integrated photovoltaics and underwater photovoltaic power generation. In addition, due to the high absorption coefficient of perovskite, photodetectors based on wide-bandgap perovskite show high responsiveness to visible light and high-energy photons, making them applicable to highly sensitive visible light and X-ray detection. For visible light detectors based on wide-bandgap perovskite, they can be used as optoelectronic synapses to mimic the functions of biological neural synapses, showing potential in information storage and neural network simulation (such as artificial retina). For high-energy detectors based on wide-bandgap perovskite, such as X-ray detectors, they can be applied to functional systems related to X-ray imaging, including security monitoring, healthcare, and environmental sensing. Moreover, wide-bandgap perovskite emits light in the blue and near-ultraviolet regions of the wavelength, making perovskite light-emitting diode devices important in white light illumination, display applications, and visible light communication technology.

[0003] Despite remarkable research progress, excessive Br elements disrupt the crystallization process of the thin film, making it difficult to effectively control crystal growth during film formation, thereby introducing bulk and interface defects, leading to energy level mismatch in the charge transport layer and triggering non-radiative recombination losses. In addition, wide-bandgap perovskite based on a mixture of I and Br faces a serious problem of photoinduced phase separation, that is, halogen ions separate into Br-rich regions and I-rich regions under light illumination, resulting in a decrease in charge mobility and a shortening of carrier lifetime, ultimately affecting device performance and stability. Summary of the Invention

[0004] The main purpose of this application is to provide a method for regulating the crystallization of wide-bandgap perovskite by CsPb 2 Br 5 and its application in tandem photovoltaics, aiming to solve the problems of poor performance and stability of existing wide-bandgap perovskite devices.

[0005] To achieve the above purpose, this application provides a method for regulating the crystallization of wide-bandgap perovskite by CsPb 2 Br 5Method for regulating crystallization of wide-bandgap perovskite and its application in tandem photovoltaics, including: preparing CsPb 2 Br 5 nanosheets; dissolving cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide and CsPb 2 Br 5 nanosheets in a solvent to obtain a perovskite precursor solution; wherein, the perovskite precursor solution includes Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite precursor complex and CsPb 2 Br 5 two phases; coating the perovskite precursor solution on a substrate to form a perovskite thin film on the substrate.

[0006] Optionally, the molar ratio of cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide and CsPb 2 Br 5 nanosheets is 0.2:0.8:(0.8 - 0.2):(0.2 - 0.8):(0.005 - 0.02); the concentration of the perovskite precursor solution is 1.0 - 1.4 mmol / mL.

[0007] Optionally, the preparation method of CsPb 2 Br 5 nanosheets includes solvothermal method, mechanical exfoliation method or liquid-phase exfoliation method.

[0008] Optionally, the preparation method of CsPb 2 Br 5 nanosheets includes: dissolving cesium bromide in water to obtain a cesium bromide solution; dissolving lead bromide in hydrobromic acid solution to obtain a lead bromide solution; adding the lead bromide solution to the cesium bromide solution to obtain CsPb 2 Br 5 .

[0009] To achieve the above object, the present application also provides a perovskite thin film for regulating crystallization of wide-bandgap perovskite by CsPb 2 Br 5 , and the perovskite thin film is obtained by the above method.

[0010] To achieve the above object, the present application also provides an application of a perovskite thin film for regulating crystallization of wide-bandgap perovskite by CsPb 2 Br 5 in the optoelectronic field.

[0011] To achieve the above object, the present application also provides a tandem photovoltaic device including the perovskite thin film for regulating crystallization of wide-bandgap perovskite by CsPb 2 Br 5A solar cell for regulating the crystallization of wide-bandgap perovskite, comprising a substrate, a hole transport layer, a perovskite thin film, an interface passivation layer, an electron transport layer, an interface modification layer and a metal electrode which are stacked in sequence from bottom to top; wherein, the perovskite thin film is the above-mentioned perovskite thin film.

[0012] Optionally, the hole transport material layer includes a nickel oxide layer and a 4-(3,6-dimethyl-9H-carbazol-9-yl)butylphosphonic acid layer from bottom to top; the material of the interface passivation layer is 1,3-propanediamine dihydroiodide; the material of the electron transport layer is a PCBM thin film; the material of the interface modification layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; the material of the metal electrode is Ag.

[0013] To achieve the above object, the present application also provides a method for preparing the above-mentioned solar cell for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 , comprising: coating a hole transport material on a substrate to obtain a hole transport layer; preparing a perovskite thin film on the surface of the hole transport layer; coating an interface passivation material on the Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite thin film to obtain an interface passivation layer; coating an electron transport material on the interface passivation layer to obtain an electron transport layer; sequentially depositing an interface modification layer and a metal electrode on the electron transport layer to obtain a solar cell.

[0014] To achieve the above object, the present application also provides an application of the above-mentioned solar cell for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 in tandem photovoltaics.

[0015] Compared with the prior art, the beneficial effects of the present application are as follows:

[0016] In the present invention, through the method of regulating the crystallization of wide-bandgap perovskite by CsPb 2 Br 5 , CsPb 2 Br 5 is introduced into the perovskite precursor solution. CsPb 2 Br 5 reduces the nucleation energy barrier by providing adsorption sites, promotes the heterogeneous nucleation of perovskite, and then guides the crystals to grow uniformly in the vertical direction; the steric hindrance effect of its nanosheets limits the disordered expansion of the crystals, reduces grain boundaries and defects, optimizes the crystal structure, and enhances the stability and uniformity of the thin film; CsPb 2 Br 5Form chemical bonds with halide ions in the perovskite, stabilizing the lattice structure and suppressing the formation of photoinduced halide phase separation and defects, thereby improving the optoelectronic properties and long-term stability of the perovskite thin film;

[0017] After being modified by CsPb 2 Br 5 The stability of the wide-bandgap perovskite thin film and the efficiency of its solar cells are significantly improved. The photoelectric conversion efficiency is increased from 18.99% without optimization to 20.14%. The efficiency of the unencapsulated device remains 90% of the initial efficiency after 1000 hours in an N 2 atmosphere;

[0018] By introducing an appropriate proportion of CsPb 2 Br 5 into the perovskite precursor solution, high-quality wide-bandgap perovskite thin films can be obtained by a one-step method, which is easy to meet the requirements of large-scale production and manufacturing. Brief Description of the Drawings

[0019] Figure 1 FIG. is a schematic structural diagram of a solar cell obtained by a method for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 in this application;

[0020] Figure 2 XRD pattern of the CsPb 2 Br 5 crystal obtained in Example 1;

[0021] Figure 3 Schematic structural diagram and SEM morphology map of the CsPb 2 Br 5 crystal obtained in Example 1;

[0022] Figure 4 TEM morphology map of the CsPb 2 Br 5 crystal obtained in Example 1 and the EDX energy spectrum maps of the corresponding elements Cs, Pb, and Br;

[0023] Figure 5 J-V curves of the wide-bandgap perovskite solar cell devices obtained in Example 1 and Comparative Example 1;

[0024] Figure 6 Dynamic light scattering (DLS) maps of the wide-bandgap perovskite precursor solutions obtained in Example 1 and Comparative Example 1;

[0025] Figure 7 Optical microscopy images of the perovskite precursor solutions in Example 1 and Comparative Example 1 heated for different times;

[0026] Figure 8 Scanning electron microscope (SEM) planar and grain size distribution diagrams of the wide-bandgap perovskite films obtained in Example 1 and Comparative Example 1;

[0027] Figure 9 X-ray diffractometer (XRD) patterns of the wide-bandgap perovskite films obtained in Example 1 and Comparative Example 1;

[0028] Figure 10 PL spectra of the wide-bandgap perovskite films obtained in Example 1 and Comparative Example 1 under one sun illumination for 0–20 min;

[0029] Figure 11 Variation curve of the photoelectric conversion efficiency of the wide-bandgap perovskite solar cell devices obtained in Example 1 and Comparative Example 1 with time in an N2 glove box atmosphere environment for unencapsulated devices;

[0030] Figure 12 For the perovskite film before and after adding CsPb 2 Br 5 UPS spectra;

[0031] Figure 13 For the perovskite film after adding CsPb 2 Br 5 Energy level diagram of the perovskite solar cell;

[0032] Figure 14 J-V curve of the perovskite solar cell device with a bandgap of 1.68 eV in Example 2;

[0033] Figure 15 For the perovskite solar cell device after adding different concentrations of CsPb 2 Br 5 in Example 3; J-V curve;

[0034] Figure 16 For the perovskite solar cell device passivated with different concentrations of PDAI 2 in Example 4; J-V curve;

[0035] Figure 17 Device structure of the 4-T tandem solar cell composed of the perovskite cell in Example 1 and the BC cell, and J-V curves of the semi-transparent wide-bandgap top device and the BC cell bottom device with and without the wide-bandgap device filter.

[0036] The realization, functional features and advantages of the objectives of this application will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0037] To make the objectives, technical solutions and advantages of this application more clear, the following will, in combination with the accompanying drawings in this application, clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are some, rather than all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts fall within the scope of protection of this application.

[0038] The first embodiment of the present invention provides a method for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 , which specifically includes the following steps:

[0039] Step S1: Mix cesium bromide and lead bromide to obtain CsPb 2 Br 5 nanosheets; specifically, the preparation method of CsPb 2 Br 5 nanosheets includes:

[0040] Step S11: Dissolve cesium bromide in water to obtain a cesium bromide solution;

[0041] Step S12: Dissolve lead bromide in a hydrobromic acid solution to obtain a lead bromide solution; the molar ratio of lead bromide to hydrobromic acid is 1:8 to 12; the volume concentration of the hydrobromic acid solution is 30%-50%.

[0042] Step S13: Add the lead bromide solution to the cesium bromide solution to obtain CsPb 2 Br 5 white precipitate; the molar ratio of cesium bromide to lead bromide is 1:1.8 to 2.2. After obtaining CsPb 2 Br 5 white precipitate, it needs to be treated to obtain pure CsPb 2 Br 5 nanosheets, specifically: CsPb 2 Br 5 white precipitate is washed three times with ethanol, centrifuged at 3000 rpm for 3 min, and then dried in a vacuum oven for 12 h to obtain white CsPb 2 Br 5 nanosheets. In this reaction, hydrobromic acid not only acts as a solvent, but also maintains the acidic environment of the reaction system by providing Br - ions, inhibits side reactions from occurring, and ensures the formation of high-purity precipitate of CsPb 2 Br 5 nanosheets. The mechanism of the above reaction is as follows:

[0043] 2CsBr + 2PbBr 2 + HBr → CsPb2 Br 5 ↓ + HBr 2

[0044] During the reaction, CsBr and PbBr 2 react in an HBr solution to form CsPb 2 Br 5 precipitate. Through the cooling precipitation method, CsPb 2 Br 5 precipitates out of the solution to form a white powder.

[0045] In addition, CsPb 2 Br 5 nanosheets can also be prepared by other methods, such as solvothermal method, mechanical exfoliation method, and liquid-phase exfoliation method. Specifically, the solvothermal method requires CsBr and PbBr 2 as precursors; the mechanical exfoliation and liquid-phase exfoliation methods require pre-synthesized CsPb 2 Br 5 bulk materials. However, the cooling precipitation method adopted in this example has the advantages of simple operation, mild reaction conditions, high product purity, etc., and is particularly suitable for large-scale preparation of CsPb 2 Br 5 nanosheets.

[0046] Step S2: Dissolve cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide, and CsPb 2 Br 5 nanosheets in a solvent, and stir at 60 °C for 1 h to form a homogeneous colloidal solution, that is, a perovskite precursor solution; wherein, the solvent can be a mixture of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the perovskite precursor solution includes Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite precursor complex (Perovskite) and CsPb 2 Br 5 two phases.

[0047] Among them, the molar ratio of cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide, and CsPb2Br5 nanosheets is 0.2:0.8:(0.8 - 0.2):(0.2 - 0.8):(0.005 - 0.02). The concentration of the perovskite precursor solution is 1.0 - 1.4 mmol / mL;

[0048] Step S3: Coat the perovskite precursor solution on a substrate to form a perovskite thin film.

[0049] In this example, CsPb 2Br 5 Reduces the nucleation energy barrier by providing adsorption sites, promotes the heterogeneous nucleation of perovskite, and then guides the crystals to grow uniformly in the vertical direction. The steric hindrance effect of its nanosheets limits the disordered expansion of the crystals, reduces grain boundaries and defects, optimizes the crystal structure, and enhances the stability and uniformity of the thin film. CsPb 2 Br 5 Forms chemical bonds with the halogen ions in the perovskite, stabilizes the lattice structure, and inhibits the formation of photoinduced halogen phase separation and defects, thereby improving the optoelectronic properties and long-term stability of the perovskite thin film. In addition, CsPb 2 Br 5 The vertically guided growth effectively releases the residual strain in the thin film, optimizes the crystal arrangement, improves the charge transport efficiency, and further increases the optoelectronic conversion efficiency (PCE) and fill factor (FF).

[0050] The second embodiment of the present invention provides a perovskite thin film for regulating the crystallization of wide-bandgap perovskite obtained by the above method through CsPb 2 Br 5 .

[0051] The third embodiment of the present invention provides an application of a perovskite thin film for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 in the optoelectronic field.

[0052] The fourth embodiment of the present invention provides a solar cell for regulating the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 , as shown in Figure 1 , including a substrate (ITO), a hole transport layer (NiO x / Me-4PACz), a perovskite thin film (Perovskite+CsPb 2 Br 5 ), an interface passivation layer (PDAI 2 ), an electron transport layer (PC 61 BM), an interface modification layer (BCP), and a metal electrode (Ag) stacked in sequence from bottom to top; wherein, the perovskite thin film is the above perovskite thin film.

[0053] The hole transport material layer includes a nickel oxide layer and a 4-(3,6-dimethyl-9H-carbazol-9-yl) butylphosphonic acid layer from bottom to top; the material of the interface passivation layer is 1,3-propanediamine dihydroiodide; the material of the electron transport layer is a PCBM thin film; the material of the interface modification layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; the metal electrode is Ag.

[0054] The fifth embodiment of the present invention provides a method for preparing a solar cell that controls the crystallization of wide-bandgap perovskite through CsPb 2 Br 5 , comprising:

[0055] Step S4, coating a hole transport material on a substrate to obtain a hole transport layer;

[0056] Using ITO conductive glass as the substrate, cleaning the ITO conductive glass and performing ultraviolet-ozone surface treatment in advance before preparing the hole transport layer; preparing a nickel oxide solution with a concentration of 10 mg / mL from nickel oxide and a solution, where the solution includes water and isopropanol with a volume ratio of 3:1; then spin-coating the nickel oxide solution (NiO x ) on the ITO conductive glass, with the spin-coating condition being 3000 r / min for 30 s, and the thin film annealing condition being 100 °C for 10 min; subsequently, spin-coating an ethanol solution of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with a concentration of 0.3 mg / mL, with the spin-coating condition being 3000 r / min for 30 s, and the thin film annealing condition being 100 °C for 10 min, to obtain the hole transport layer.

[0057] Step S5, preparing a perovskite thin film on the surface of the hole transport layer;

[0058] Specifically, the perovskite thin film in this embodiment is obtained by spin-coating, and the method is a one-step anti-solvent spin-coating method. Specifically, spin-coating a perovskite precursor solution on the hole transport layer to form a film, dropping the anti-solvent anisole, and performing annealing treatment on a hot stage to obtain a Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 wide-bandgap perovskite thin film; the spin-coating condition is 5000 - 8000 r / min for 25 - 30 s, the anti-solvent is anisole, the dropping time is the 24th - 28th s after the start of spin-coating, and the thin film annealing condition is 90 - 110 °C for 10 - 15 min.

[0059] Step S6, coating an interface passivation material on the perovskite thin film to obtain an interface passivation layer;

[0060] Specifically, spin-coating a PDAI 0.2 FA 0.8 PbI 1.8 Br 1.2 solution placed in an N 2 glove box on the Cs 2 perovskite thin film, with the spin-coating condition being 3000 r / min for 25 s, and annealing on a hot stage at 100 °C for 5 min after spin-coating.

[0061] Step S7: Coat an electron transport material on the interface passivation layer to obtain an electron transport layer;

[0062] Spin-coat the PCBM solution placed in the glove box on the interface passivation layer. The spin-coating conditions are 2000 r / min for 30 s. After spin-coating, anneal on a hot plate at 100 °C for 10 min. 2 Spin-coat the PCBM solution placed in the glove box on the interface passivation layer. The spin-coating conditions are 2000 r / min for 30 s. After spin-coating, anneal on a hot plate at 100 °C for 10 min.

[0063] Step S8: Deposit an interface modification layer with a thickness of 4 - 8 nm and a metal electrode with a thickness of 95 - 105 nm on the electron transport layer in sequence to obtain a solar cell;

[0064] Adopt the vacuum thermal evaporation method to deposit 6 nm of BCP and 100 nm of metal electrode Ag on the electron transport layer in sequence to obtain a solar cell.

[0065] Example 1: Two-dimensional material Cs 2 Br 5 As an additive to prepare Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 Perovskite thin film and its solar cell

[0066] Step S1: Dissolve 42.6 mg (0.2 mmol) of cesium bromide in 2 mL of water to obtain a cesium bromide solution; dissolve 146.8 mg (0.4 mmol) of lead bromide in 4 mL of hydrobromic acid solution to obtain a lead bromide solution; add 2 mL of the lead bromide solution to 4 mL of the cesium bromide solution to obtain a CsPb 2 Br 5 White precipitate; wash the CsPb 2 Br 5 White precipitate three times with ethanol, centrifuge at 3000 rpm for 3 min, and then dry in a vacuum oven for 12 h to obtain white CsPb 2 Br 5 Nanosheets;

[0067] To verify that the phase of the synthesized product is CsPb 2 Br 5 Crystal, X-ray diffraction (XRD) characterization was performed on the obtained product. By comparing the test results with the XRD standard PDF card CsPb 2 Br 5 (PDF#22 - 0553), it was found that the characteristic diffraction peaks of the synthesized product were completely matched with the standard card, as Figure 2 Shown. This result clearly proves that the synthesized product is CsPb 2 Br 5 Crystal, laying a phase foundation for subsequent research.

[0068] The CsPb 2 Br 5 obtained in this embodiment has a structure as shown in Figure 3 . As can be seen from Figure 3 a, CsPb 2 Br 5 crystals were successfully synthesized in the early stage of the experiment, and their appearance is white flash flaky powder. To further analyze its morphological characteristics, the CsPb 2 Br 5 crystal powder was characterized by scanning electron microscopy (SEM), and the results are as shown in Figure 3 b. The SEM image shows that the CsPb 2 Br 5 crystal powder mainly exists in an irregular continuous flaky structure, and the flaky morphology is evenly distributed.

[0069] To further study the morphological and elemental distribution characteristics of the CsPb 2 Br 5 crystal powder, the prepared CsPb 2 Br 5 crystal powder was characterized by TEM. The results are as shown in Figure 4 . The lattice fringe spacings of CsPb 2 Br 5 are 0.27 nm and 0.31 nm respectively, corresponding to the (210) and (005) crystal planes of CsPb 2 Br 5 , which is highly consistent with the XRD test results, as shown in Figure 4 a. In addition, the elemental distribution of CsPb 2 Br 5 was analyzed by energy dispersive X-ray spectroscopy (EDX), and the results show that Cs, Pb, and Br elements are evenly distributed on the surface of the CsPb 2 Br 5 crystal powder, as shown in Figure 4 b. These results further verify the high crystal quality and uniform elemental distribution of the CsPb 2 Br 5 crystal.

[0070] Step S2: Dissolve cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide, and CsPb2Br5 nanosheets in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) according to a molar ratio of 0.2:0.8:0.4:0.6:0.02, and stir at 60 °C for 1 h to form a perovskite precursor solution with a concentration of 1.2 mmol / mL;

[0071] Step S3: Perform ultrasonic cleaning using the process of ethanol (30 min) - ultrapure water plus cleaning agent (30 min) - ultrapure water (30 min) - acetone (30 min) - ethanol (30 min). After drying with a nitrogen gun, place it in an oven for drying to obtain a clean ITO substrate; perform ultraviolet-ozone surface treatment on the clean ITO substrate for 20 min;

[0072] Step S4: Use a pipette to aspirate 40 μL of nickel oxide solution with a concentration of 10 mg / mL and evenly coat it on the ITO substrate. The spin-coating conditions are 3000 r / min for 30 s, and the thin-film annealing conditions are annealing at 100 °C for 10 min. Then transfer the ITO into the 2 glove box; again, use a pipette to aspirate 40 μL of ethanol solution of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with a concentration of 0.3 mg / mL and coat it on the ITO substrate spin-coated with nickel oxide. The spin-coating conditions are 3000 r / min for 30 s, and the thin-film annealing conditions are annealing at 100 °C for 10 min to obtain a hole transport layer.

[0073] Step S4: Use a pipette to aspirate 50 μL of perovskite precursor solution and evenly coat it on the hole transport layer. The spin-coating conditions are 5000 r / min for 32 s. At the 24th s of the start of spin-coating, quickly add 100 μL of anisole antisolvent. After spin-coating, anneal on a hot plate at 100 °C for 15 min to obtain 0.2 Cs 0.8 FA 1.8 PbI 1.2 Br

[0074] Step S5: Use a pipette to aspirate 40 μL of the prepared PDAI 2 solution placed in the 2 glove box and evenly coat it on the 0.2 Cs 0.8 FA 1.8 PbI 1.2 Br

[0075] perovskite film. The spin-coating conditions are 3000 r / min for 25 s. After spin-coating, anneal on a hot plate at 100 °C for 5 min to obtain an interfacial passivation layer; 2 Step S6: Use a pipette to aspirate 35 μL of the prepared PCBM solution placed in the glove box and spin-coat it on the interfacial passivation layer. The spin-coating conditions are 2000 r / min for 30 s. After spin-coating, anneal on a hot plate at 100 °C for 10 min to obtain an electron transport layer;

[0076] Step S7: Using the vacuum thermal evaporation method, deposit 6 nm of BCP and 100 nm of metal electrode Ag successively on the electron transport layer to obtain a solar cell.

[0077] In this embodiment, the performance of the obtained solar cell is tested as follows:

[0078] Under the test conditions of standard simulated sunlight (AM 1.5G illumination, 100 mW·cm -2 ), the J-V curve of the Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite solar cell prepared in this Example 1 (Target) is Figure 5 . It can be seen from the figure that its photoelectric conversion efficiency is 20.14%, the open circuit voltage is 1.28 V, the short circuit current is 18.36 mA·cm -2 , and the fill factor is 85.39%.

[0079] Dynamic light scattering (DLS) measurements show that as Figure 6 , the presence of CsPb 2 Br 5 can interact with the Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 precursor solution. By promoting heterogeneous nucleation and providing uniform nucleation sites, the colloidal clusters in the precursor solution are reduced from 5518 nm to 825 nm, forming smaller clusters. Optical microscope observations ( Figure 7 ) show that the target solution Target (containing CsPb 2 Br 5 ) exhibits rapid and uniform nucleation and balanced and uniform nuclear growth, and the nucleation rate is significantly higher than that of the control group Control (without CsPb 2 Br 5 ). The nucleation mechanism guided by CsPb 2 Br 5 not only reduces the nucleation energy barrier but also promotes the vertical growth of crystals through physical adsorption, improves the crystal arrangement, and reduces the formation of grain boundaries. By means of scanning electron microscopy (SEM), the morphology of the wide-bandgap perovskite film before and after the introduction of CsPb 2 Br 5 is characterized and analyzed ( Figure 8 ). From the scanning electron microscopy (SEM) plane and interface maps of the wide-bandgap perovskite film obtained in Comparative Example 1 ( Figure 8 a and Figure 8c), Planar and interfacial spectra of the wide-bandgap perovskite thin film obtained in Example 1 by scanning electron microscopy (SEM) Figure 8 As can be seen from 2 Br 5 introducing 2 Br 5 , the grain size becomes more uniform, the thin film is flatter, and the grain size increases at the same time. After statistics, the average grain size increases from 239.9 ± 52.0 nm to 286.2 ± 51.4 nm; then, with the help of an X-ray diffractometer (XRD), the crystallinity of the wide-bandgap perovskite thin film before and after Figure 9 CsPb 2 Br 5 modification was investigated. The results show that the film without 2 CsPb 2 Br 5 shows a diffraction peak of the 2 PbI 2 phase at 12°, while the film with 5 CsPb 2 Br 2 does not show the

[0080] PbI 2 Br 5 peak, and the intensities of other perovskite phase peaks are enhanced. Specifically, Figure 10 CsPb Figure 10 Br 2 preferentially adsorbs on the (011) plane of the perovskite crystal, changing the crystallization direction of the perovskite, and suppressing the side reaction of 5 PbI Figure 10 This indicates that the formation of 2 Br 5 is inhibited and the crystallinity of the film is better. 2 Br 5 To study the role of 2 Br 5 in suppressing the halogen phase separation of the wide-bandgap perovskite thin film, the evolution of the photoluminescence (PL) spectrum under continuous one-sunlight illumination intensity was measured, as Figure 10 shown. As Figure 10 a, for the control sample without 2 Br 5 , with the prolongation of the illumination time, the PL emission peak shows an obvious red shift, and the emission peak position shifts from 692 nm to 715 nm. This indicates that halogen phase separation occurs and a iodine-rich phase domain with a narrower bandgap is formed. This phenomenon is caused by the migration of halogen ions and the accumulation of defects, resulting in a decrease in the stability of the perovskite lattice and the deterioration of optical properties. In contrast, as Figure 10 b, the perovskite thin film with 2 Br 5 shows almost no red shift during illumination, and the emission peak position shifts from 684 nm to 694 nm, and the PL peak position remains relatively stable. This stabilization effect is attributed to 2 Br 5It can interact with halogen ions and defect sites, effectively blocking the ion migration path and inhibiting phase separation.

[0081] For the perovskite solar cells placed under N 2 storage conditions, CsPb 2 Br 5 was introduced before and after, and the stability of the perovskite solar cells was tested to explore its effect on the stability of perovskite. The results are as Figure 11 shown. It can be clearly seen from the figure that after being placed for 200 hours, the device efficiency without the introduction of CsPb 2 Br 5 began to decay significantly. After being placed for 500 hours, only 80% of the initial efficiency was maintained; while the device with the introduction of CsPb 2 Br 5 could still maintain 90% of the initial efficiency after being placed for 700 hours.

[0082] In this example, UPS was also used to study the influence of CsPb 2 Br 5 on the energy band electronic structure of the wide-bandgap perovskite thin film. The results are as Figure 12 shown. Comparing before the addition of CsPb 2 Br 5 ( Figure 12 a-b), after the addition of CsPb 2 Br 5 ( Figure 12 c-d), the work function of the wide-bandgap perovskite thin film increased from about -4.78 eV to -4.77 eV with little change, and at the same time, the VBM increased from -5.81 eV to -5.68 eV. This change indicates that the introduction of CsPb 2 Br 5 creates a more favorable surface energy environment for hole extraction and electron blocking by adjusting the energy band structure. The CBM of the passivated perovskite thin film and the work function of the electron transport layer PC 61 BM achieved better energy level alignment. Good energy level matching can not only effectively promote the transport of carriers, but also significantly reduce the loss of the open-circuit voltage . This energy level regulation effect ultimately improves the photovoltaic performance of the device and provides an important design basis for further optimizing wide-bandgap perovskite photovoltaic devices.

[0083] Figure 13 is the device energy level diagram drawn based on the analysis results of UPS. It can be seen from the figure that CsPb 2 Br 5 forms an effective energy level regulation effect on the perovskite surface. Compared with the perovskite without the addition of CsPb 2 Br 5 , for the perovskite with the addition of CsPb2 Br 5 The resulting device has better energy level matching, which can effectively promote the extraction of holes and electrons and reduce non-radiative recombination losses.

[0084] Example 2

[0085] Two-dimensional material CsPb 2 Br 5 As an additive to prepare Cs 0.2 FA 0.8 PbI 2.4 Br 0.6 Perovskite thin film and its solar cell

[0086] The method of this example is the same as that of Example 1, except that the molar ratios of cesium iodide, formamidinium hydroiodide, lead iodide, lead bromide, and CsPb 2 Br 5 nanosheets in the precursor solution are 0.2:0.8:0.8:0.2:0.02, and the molar ratios of the remaining components added remain unchanged. The band gap of the prepared perovskite thin film is measured to be 1.68 eV. After adding CsPb 2 Br 5 nanosheets, the film morphology is improved and the device efficiency is increased. The device structure diagram of the wide-bandgap perovskite solar cell prepared in this Example 2 is as Figure 1 shown, Figure 14 Under the test conditions of standard simulated sunlight (AM 1.5G illumination, 100 mW·cm -2 -2), the J-V curve of the wide-bandgap perovskite solar cell device prepared in this Example 2 has a photoelectric conversion efficiency of 21.09%, an open-circuit voltage of 1.24 V, a short-circuit current of 20.38 mA / cm 2 2, and a fill factor of 84.75%.

[0087] Example 3

[0088] Different concentrations of two-dimensional material CsPb 2 Br 5 As an additive to prepare Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 Perovskite thin film and its solar cell

[0089] The method of this example is the same as that of Example 1, except that the molar concentrations of CsPb 2 Br 5 nanosheets in the precursor solution are 0 mmol, 0.5 mmol, 1 mmol, 2 mmol, 4 mmol, respectively, and the molar ratios of the remaining components added remain unchanged. Example 3 is to explore the addition of CsPb2 Br 5 Optimal addition concentration of nanosheets. Figure 15 Under the test conditions of standard simulated sunlight (AM1.5G illumination, 100 mW·cm -2 ), the J-V curves of the broadband gap perovskite solar cell devices prepared in Example 3 with different concentrations of CsPb 2 Br 5 are shown. The optimal concentration is 2 mmol. Its photoelectric conversion efficiency is 20.14%, the open circuit voltage is 1.28 V, the short circuit current is 18.36 mA·cm -2 , and the fill factor is 85.39%.

[0090] Example 4

[0091] Upper interface solution PDAI with different concentrations 2 solution passivates Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite thin films and their solar cells

[0092] The method of this example is the same as that of Example 1, except that the concentrations of PDAI in the upper interface solution are 0 mg / mL, 0.5 mg / mL, 1.0 mg / mL, and 1.5 mg / mL respectively. Example 4 is to explore the optimal passivation concentration of PDAI in the upper interface solution. 2 concentrations are 0 mg / mL, 0.5 mg / mL, 1.0 mg / mL, and 1.5 mg / mL respectively. Example 4 is to explore the optimal passivation concentration of PDAI in the upper interface solution. 2 Optimal passivation concentration. Figure 16 Under the test conditions of standard simulated sunlight (AM 1.5G illumination, 100 mW·cm -2 ), the J-V curves of the broadband gap perovskite solar cell devices passivated by PDAI with different concentrations in the upper interface solution prepared in Example 4 are shown. The optimal concentration is 0.5 mg / mL. Its photoelectric conversion efficiency is 18.99%, the open circuit voltage is 1.25 V, the short circuit current is 17.93 mA·cm 2 , and the fill factor is 84.65%. -2 Fill factor is 84.65%.

[0093] Comparative Example 1 does not add CsPb 2 Br 5 solution to prepare Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 perovskite thin films and their solar cells

[0094] The method of this comparative example is the same as that of Example 1, except that CsPb 2 Br 5 is not added to the precursor solution. Figure 5The Control curve in -2 standard test conditions (AM1.5 G illumination, 100 mW·cm -2 ), the photoelectric conversion efficiency of the wide-bandgap perovskite solar cell device prepared in this comparative example is 18.99%, the open-circuit voltage is 1.25 V, and the short-circuit current is 17.93 mA·cm

[0095] The sixth embodiment of the present invention provides an application of the above-mentioned solar cell that regulates the crystallization of wide-bandgap perovskite in tandem photovoltaics through CsPb 2 Br 5 .

[0096] As Figure 17 shown, the solar cell obtained in Example 1 and the back-contact cell (BC cell) were used to construct a four-terminal (4T) perovskite and silicon tandem solar cell, and the structure is as Figure 17 shown in a, and its structure is ITO / NiO x / Me-4PACz / Perovskite / PDAI 2 / PC 61 BM / BCP / SnO 2 / ITO / HBC Si Cell structure; the PCE of this 4T perovskite and silicon tandem solar cell is 19.3%. Using the semi-transparent WBG device made of the solar cell obtained in Example 1 as a filter, the PCE of the BC cell device with 24.2% PCE after filtering is 11.3%, and finally a 4T tandem solar cell with a PCE of 30.6% is produced, as Figure 17 shown in b.

[0097] The above are only the preferred embodiments of this application, and do not limit the patent scope of this application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of this application.

Claims

1. A method for regulating the crystallization of wide-bandgap perovskite by CsPb2Br5, characterized in that: include: Mix cesium bromide with lead bromide to obtain CsPb2Br5 nanosheets; Dissolving cesium iodide, formamidine hydroiodide, lead iodide, lead bromide and the CsPb2Br5 nanosheets in a solvent to obtain a perovskite precursor solution; Wherein, the perovskite precursor solution includes Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 Perovskite precursor complex and CsPb2Br5 two phases; The perovskite precursor solution is coated on a substrate to form a perovskite film on the substrate.

2. The method for regulating the crystallization of wide bandgap perovskite by CsPb2Br5 according to claim 1, characterized in that: The molar ratio of the cesium iodide, the formamidine hydroiodide, the lead iodide, the lead bromide and the CsPb2Br5 nanosheets is 0.2:0.8:(0.8-0.2):(0.2-0.8):(0.005-0.02); The concentration of the perovskite precursor solution is 1.0-1.4 mmol / mL.

3. The method for regulating the crystallization of wide bandgap perovskite by CsPb2Br5 according to claim 1, characterized in that: The preparation method of the CsPb2Br5 nanosheets includes a solvent thermal method, a mechanical exfoliation method or a liquid phase exfoliation method.

4. The method for regulating the crystallization of wide bandgap perovskite by CsPb2Br5 according to claim 3, characterized in that: The preparation method of the CsPb2Br5 nanosheets comprises: dissolving cesium bromide in water to obtain a cesium bromide solution; Dissolving lead bromide in a hydrobromic acid solution to obtain a lead bromide solution; Lead bromide solution is added to cesium bromide solution to obtain CsPb2Br5.

5. A perovskite film that regulates the crystallization of wide-bandgap perovskite by CsPb2Br5, characterized in that: The perovskite film is obtained by the method according to any one of claims 1 to 4.

6. Application of the perovskite film in the optoelectronic field in which the wide bandgap perovskite crystallization is regulated by CsPb2Br5 according to claim 5.

7. A solar cell that regulates the crystallization of wide-bandgap perovskite by CsPb2Br5, characterized in that: It includes a substrate, a hole transport layer, a perovskite film, an interface passivation layer, an electron transport layer, an interface modification layer and a metal electrode which are stacked in sequence from bottom to top; Wherein, the perovskite film is the perovskite film according to claim 5.

8. The solar cell of claim 7 wherein the wide bandgap perovskite crystallization is regulated by CsPb2Br5, The hole transport material layer includes a nickel oxide layer and a 4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid layer from bottom to top; The material of the interface passivation layer is 1,3-propylenediamine dihydroiodide; The material of the electron transport layer is a PCBM film; The material of the interface modification layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; The metal electrode is Ag.

9. A method for preparing a solar cell by regulating the crystallization of wide-bandgap perovskite by CsPb2Br5 according to claim 7 or 8, characterized in that: include: coating a hole transport material on a substrate to obtain a hole transport layer; Prepare a perovskite film covering the surface of the hole transport layer; coating an interface passivation material on the perovskite film to obtain an interface passivation layer; coating an electron transport material on the interface passivation layer to obtain an electron transport layer; An interface modification layer and a metal electrode are sequentially deposited on the electron transport layer to obtain a solar cell.

10. Use of a solar cell in which wide bandgap perovskite crystallization is regulated by CsPb2Br5 as claimed in claim 7 or 8 in stacked photovoltaics.

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