Passivating additive for improving perovskite defects, perovskite thin film and preparation method of perovskite thin film

Abstract

The invention discloses a passivation additive for improving perovskite defects, a perovskite thin film and a preparation method of the perovskite thin film. The passivation additive is moroxydine hydrochloride. By adding moroxydine hydrochloride into the perovskite precursor solution, the crystallization process of the perovskite thin film can be regulated and controlled, defects can be passivated, the obtained perovskite thin film is large and uniform in grain size, few in gaps among grains, high in density and few in non-radiative composite defects, the survival life of carriers is greatly prolonged, and the performance of the perovskite thin film is improved. Moreover, the non-radiative recombination loss of carriers is greatly reduced, and the photoelectric performance of the wide-band-gap perovskite is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of passivation technology for structural components of organic solid-state devices, specifically relating to a passivation additive for improving perovskite defects, a perovskite thin film, and a method for preparing the same. Background Technology

[0002] Solar energy is considered the most promising new energy source of the 21st century. Perovskite, as a light-absorbing material for next-generation photovoltaic devices, has attracted much attention due to its high efficiency. After more than a decade of development, the internationally certified efficiency of single-junction perovskite solar cells has approached that of crystalline silicon solar cells.

[0003] However, the poor long-term stability of perovskite photovoltaic cells has become a key obstacle restricting their commercial application. The core problem lies mainly in the following aspects: firstly, the organic cations at the A-site in the perovskite crystal structure (such as formamidinium ions, FA...) + methylammonium ion MA + The thermal stability of inorganic Pb-I is relatively weak, and its volatility leads to the collapse of the inorganic Pb-I octahedral framework, thereby promoting the decomposition of the photoactive phase. On the other hand, during crystallization, numerous intrinsic defects such as vacancies and interstitial atoms easily form within the crystal lattice. These defects not only induce nonradiative recombination of charge carriers, significantly reducing the open-circuit voltage of the device, but also act as channels for ion migration. Especially under external conditions such as light, thermal fields, and water vapor, halide ions (I₂)... - ,Br - Cl - It is highly susceptible to migration and component segregation, leading to a rapid decline in the photoelectric properties of the material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a passivation additive for improving perovskite defects, a perovskite thin film and a method for preparing the same. By introducing the passivation additive into the perovskite precursor solution, crystal nucleation and growth can be regulated, crystal quality can be improved, and its molecular structure characteristics can be used to passivate defects and inhibit ion migration, thereby improving the photoelectric conversion efficiency and stability of the device.

[0005] The first aspect of the present invention provides a passivating additive for improving perovskite defects, wherein the passivating additive is morpholine guanidine hydrochloride.

[0006] A second aspect of the present invention provides a perovskite thin film containing the above-described passivating additive. The grain boundaries of the perovskite thin film contain morpholine guanidine hydrochloride molecules, which interact with the perovskite crystals through their functional groups.

[0007] The third aspect of the present invention provides a method for preparing the above-mentioned perovskite thin film, the specific steps of which are: adding morpholine guanidine hydrochloride to a perovskite precursor solution, shaking it evenly, then spin-coating it onto a substrate, adding an anti-solvent in the later stage of spin-coating, and then annealing the substrate to obtain a perovskite thin film with high crystallinity on the substrate surface.

[0008] According to the above scheme, the solute in the perovskite precursor solution is a perovskite material precursor with an ABX3 structure, wherein A is CH3NH3. + (abbreviated as MA) + ), HC(NH2)2 + (abbreviated as FA) + ), Cs + or Rb + One or more of them; B is selected from Pb 2+ Sn 2+ At least one of them; X is I - ,Br - Cl - At least one of them.

[0009] Preferably, the perovskite precursor solution is composed of methylammonium chloride (MACl), formamidinium iodide (FAI), cesium iodide (CsI), lead chloride (PbCl2), lead bromide (PbBr2), and lead iodide (PbI2) in a (Cs) ratio. 0.21 FA 0.76 MA 0.03 Pb(Cl) 0.06 Br 0.14 I 0.80 The chemical ratio of 3 is dissolved in a mixed solvent to obtain the product.

[0010] According to the above scheme, the mixed solvent is a mixture of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 3-4:1.

[0011] According to the above scheme, the concentration of methylammonium chloride in the perovskite precursor solution is 2.7-3.0 g / L.

[0012] According to the above scheme, the mass-to-volume ratio of morpholine guanidine hydrochloride to the perovskite precursor solution is 0.5-5 mg / mL.

[0013] According to the above scheme, the shaking process conditions are: shaking at a frequency of 1000-3000 times / minute for 1-5 hours until the solute is completely dissolved.

[0014] According to the above scheme, the anti-solvent is added dropwise in the later stage of spin coating. The specific process conditions are: spin coating at a speed of 3000-6000 rpm for 20-60 seconds, and the anti-solvent is added dropwise 3-10 seconds before the end of spin coating.

[0015] According to the above scheme, the antisolvent is ethyl acetate, chlorobenzene, or toluene.

[0016] According to the above scheme, the annealing process conditions are as follows: under the protection of an inert atmosphere, hold at 80-150℃ for 10-60 minutes, and then cool to room temperature in the furnace.

[0017] The fourth aspect of the present invention provides a perovskite solar cell, comprising a transparent conductive substrate, a hole transport layer, a perovskite thin film as described in the second aspect above, a perovskite upper surface passivation layer, an electron transport layer, a buffer layer, and an electrode layer stacked sequentially.

[0018] According to the above scheme, the hole transport layer is [4-(7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphonic acid (CAS: 2882156-63-8, abbreviated as 4PADCB) or (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (CAS: 2747959-96-0, abbreviated as Me-4PACz).

[0019] According to the above scheme, the method for preparing the passivation layer on the upper surface of the perovskite is as follows: spin-coating a solution of piperazine hydroiodide in isopropanol (IPA) onto the surface of the perovskite film, and then annealing it.

[0020] This invention, by adding morpholine guanidine hydrochloride to the perovskite precursor solution, can increase the migration barrier of halide ions, making it more difficult for halide ions to move within the perovskite lattice, thereby effectively suppressing perovskite phase separation. Furthermore, this additive can regulate the nucleation and crystal growth process of perovskite, significantly increasing the size and more uniform distribution of perovskite grains, reducing the grain boundary density of the perovskite film, and improving the overall quality of the perovskite film. Moreover, the morpholine guanidine hydrochloride molecule has a large dipole moment, and positive and negative charge centers can be formed at different sites of its guanidine group, which can selectively passivate defects with different charges, ultimately forming a high-crystallinity, low-defect-state-density, high-quality perovskite thin film.

[0021] The beneficial effects of this invention are as follows: By adding morpholine guanidine hydrochloride to the perovskite precursor solution, this invention can regulate the crystallization process of the perovskite film and passivate defects. The resulting perovskite film has large and uniform grain size, few intergranular voids, high film density, and few non-radiative recombination defects, which greatly prolongs the carrier lifetime and significantly reduces the non-radiative recombination loss of carriers, effectively improving the photoelectric properties of wide-bandgap perovskite. Attached Figure Description

[0022] Figure 1 The XRD comparison images show the modified perovskite film prepared in Example 1 of the present invention and the perovskite film prepared in Comparative Example 1. Figure 2SEM images of the modified perovskite film prepared in Example 1 (left) and the perovskite film prepared in Comparative Example 1 (right); Figure 3 SEM images of the modified perovskite film (left) prepared in Example 1 and the perovskite film (right) prepared in Comparative Example 1 after aging treatment. Figure 4 PL images of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1. Figure 5 TRPL images of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1. Figure 6 PLQY diagrams of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1. Figure 7 The image shows a comparison of the JV curves of the modified perovskite solar cell prepared in Example 1 and the perovskite solar cell prepared in Comparative Example 1. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] The method for preparing the conductive substrate with hole transport layer used in the embodiments and comparative examples of the present invention is as follows: 80 μL of 0.6 mg / mL 4PADCB ethanol solution was statically dropped onto a clean ITO glass substrate (2.5 cm × 2.5 cm), and spin-coated at 4000 rpm for 20 seconds. Then, it was annealed at 100 °C for 10 min under nitrogen protection to obtain a conductive substrate with a 4PADCB hole transport layer on its surface, which was then set aside for use.

[0025] Example 1 A modified perovskite thin film, the specific steps of which are as follows: 1) Press (Cs) 0.21 FA 0.76 MA 0.03 Pb(Cl) 0.06 Br 0.14 I 0.80The chemical composition of the perovskite raw materials was as follows: 2.84 mg MACl, 187.79 mg FAI, 80.02 mg CsI, 31.65 mg PbCl2, 115.61 mg PbBr2, 500.02 mg PbI2 and 1 mg morpholine guanidine hydrochloride were dissolved in 1 mL of a mixed solvent, which was obtained by mixing DMF and DMSO in a volume ratio of 3:1. The solution was then placed in a shaker and shaken at a frequency of 2000 times / minute for 3 hours until the solid was completely dissolved, thus obtaining the modified perovskite precursor solution. 2) Take 75 μL of the modified perovskite precursor solution obtained in step 1) and spread it onto a conductive substrate with a hole transport layer. Immediately spin-coat it at 5000 rpm for 30 seconds. Add 175 μL of antisolvent (ethyl acetate) in the last 5 seconds of the spin-coating process. Finally, anneal it at 100°C for 30 minutes under nitrogen protection to obtain the modified perovskite film.

[0026] After the modified perovskite film cooled to room temperature, 60 μL of a 0.3 mg / mL isopropanol solution of piperazine hydroiodide was added dropwise to the surface of the modified perovskite film. The film was then spin-coated at 5000 rpm for 30 seconds and annealed at 100 °C for 10 minutes under nitrogen protection to obtain a perovskite upper surface passivation layer (PAI).

[0027] C is further deposited sequentially on the surface of the passivation layer by thermal evaporation. 60 (Electron transport layer, 25 nm thick), BCP (buffer layer, 7 nm thick), and silver electrode (100 nm thick) yielded a structure of ITO / 4PADCB / modified perovskite / PAI / C. 60 / BCP / Ag modified perovskite solar cells.

[0028] Comparative Example 1 This comparative example provides a perovskite film without the addition of morpholine guanidine hydrochloride. Its preparation method is similar to that of Example 1, except that morpholine guanidine hydrochloride is not added during the preparation of the perovskite precursor solution in step 1).

[0029] Using the method of Example 1, a perovskite upper surface passivation layer, an electron transport layer, a buffer layer, and a silver electrode were sequentially prepared on the surface of the perovskite thin film prepared in this comparative example to obtain a perovskite solar cell.

[0030] Figure 1The XRD patterns of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1 are shown. It can be seen that the peak positions of the perovskite films prepared in Example 1 and Comparative Example 1 are consistent, indicating that the addition of morpholine guanidine hydrochloride did not affect the crystal structure and orientation of the perovskite, indicating that morpholine guanidine hydrochloride did not enter the perovskite lattice. Moreover, the intensity of the characteristic diffraction peak of PbI2 at 12.68° in Example 1 was significantly reduced, indicating that the additive improved the crystallization process of the perovskite, with less residual PbI2 in the film, more complete precursor reaction, and purer perovskite mineral phase.

[0031] Figure 2 The images show SEM images of the modified perovskite film prepared in Example 1 (left) and the perovskite film prepared in Comparative Example 1 (right). The comparison shows that the perovskite grains of the film sample in Example 1 are larger and more uniform in size, with significantly reduced intergranular voids and higher film density. This indicates that the crystallization process is more uniform and that grain boundary and pore defects are effectively suppressed, proving that morpholine guanidine hydrochloride has a regulatory effect on the perovskite crystallization process.

[0032] Figure 3 The SEM images of the modified perovskite film prepared in Example 1 (left) and the perovskite film prepared in Comparative Example 1 (right) after aging treatment under nitrogen atmosphere and 85°C for 120 hours under twice the intensity of sunlight show that, in comparison, white areas appear at the grain boundaries of the perovskite in Comparative Example 1, which may be the PbI2 phase obtained after phase separation. In contrast, the perovskite grain shape of the film sample in Example 1 is almost unchanged, indicating that morpholine guanidine hydrochloride can effectively inhibit phase separation.

[0033] The photoluminescence (PL) spectra of the modified perovskite films prepared in Example 1 and the perovskite films prepared in Comparative Example 1 were tested using an FLS980 fluorescence spectrometer equipped with a 485nm laser diode. The test results are shown in the figure. Figure 4 As shown, it can be seen that after adding morpholine guanidine hydrochloride, the main peak intensity of the modified perovskite film obtained in Example 1 is significantly greater than that of the perovskite film in Comparative Example 1, indicating that the modification with morpholine guanidine hydrochloride effectively reduces non-radiative recombination defects.

[0034] Figure 5 The images show the time-resolved photoluminescence (TRPL) spectra of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1. The comparison shows that the luminescence intensity of the modified perovskite film in Example 1 decays significantly more slowly and maintains a high intensity over a long period, indicating that the addition of morpholine guanidine hydrochloride effectively suppresses nonradiative recombination and significantly extends carrier lifetime.

[0035] The photoluminescence quantum yield (PLQY) of the modified perovskite film prepared in Example 1 and the perovskite film prepared in Comparative Example 1 was tested using the LQ-100X-PL photoluminescence quantum efficiency testing system (excitation wavelength 405 nm). The test results are shown in the figure. Figure 6 As shown, compared with Comparative Example 1, the PLQY peak value of the modified perovskite film in Example 1 was increased to 1.663%, indicating that the introduction of morpholine guanidine hydrochloride can significantly reduce its carrier nonradiative recombination loss and effectively improve the photoelectric performance of wide-bandgap perovskite.

[0036] Figure 7 The image shows a comparison of the JV curves of the modified perovskite solar cell prepared in Example 1 and the perovskite solar cell prepared in Comparative Example 1. The current density-voltage (JV) characteristic curves of the device were recorded using a Keithley 2400 digital source meter. Simulated sunlight was provided by a 300W solar simulator (Oriel 94023A) equipped with an AM1.5G filter, with a light intensity calibrated to 100 mW cm⁻¹ using a standard silicon reference cell. -2 During testing, an opaque metal mask was used to precisely define the effective active area of ​​the device as 0.148 cm². 2 The JV scan rate is set to 100 mV / s. -1 The scan step size was 10mV, the delay time was 100ms, the scan voltage range was -0.1V to 1.2V, and a forward scan mode was used. It can be seen that the performance of the modified perovskite solar cell obtained after adding morpholine guanidine hydrochloride is significantly improved: the open-circuit voltage (V... OC The voltage was increased from 1.195V to 1.222V. Furthermore, the current density (J / L) was also increased. SC With the addition of fill factor (FF), the photoelectric conversion efficiency (PCE) of perovskite solar cells is also improved. The photoelectric conversion efficiency of the modified perovskite solar device with the addition of morpholine guanidine hydrochloride is increased from 19.13% to 21.63%.

[0037] In summary, the embodiments of the present invention use morpholine guanidine hydrochloride to regulate perovskite crystallization. Without changing the crystal structure and orientation of the perovskite, the crystallization process is controlled to increase the grain size and reduce the number of grain boundaries, significantly suppressing the generation of internal defects in the perovskite crystal, reducing nonradiative recombination of charge carriers, significantly enhancing stability, and greatly improving the efficiency of photovoltaic devices. This provides an effective method for the commercial application of perovskite solar cells.

[0038] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A passivating additive for improving perovskite defects, characterized in that, The passivating additive is morpholine guanidine hydrochloride.

2. A perovskite thin film containing the passivating additive of claim 1.

3. A method for preparing a perovskite thin film according to claim 2, characterized in that, The specific steps are as follows: Morpholine guanidine hydrochloride is added to the perovskite precursor solution, shaken to mix, and then spin-coated onto the substrate. In the later stage of spin-coating, an antisolvent is added dropwise, and then the substrate is annealed to obtain a perovskite film with high crystallinity on the substrate surface.

4. The method for preparing perovskite thin films according to claim 3, characterized in that, The solute in the perovskite precursor solution is a perovskite material precursor with an ABX3 structure, where A is CH3NH3. + HC(NH2)2 + Cs + or Rb + One or more of them; B is selected from Pb 2+ Sn 2+ At least one of them; X is I - ,Br - Cl - At least one of them.

5. The method for preparing perovskite thin films according to claim 4, characterized in that, The perovskite precursor solution is composed of methylammonium chloride, formamidinium iodide, cesium iodide, lead chloride, lead bromide, and lead iodide in a mixture of (Cs) 0.21 FA 0.76 MA 0.03 Pb(Cl) 0.06 Br 0.14 I 0.80 The chemical formula of 3 is obtained by dissolving it in a mixed solvent; the mixed solvent is a mixture of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3-4:

1.

6. The method for preparing perovskite thin films according to claim 5, characterized in that, The concentration of methylammonium chloride in the perovskite precursor solution is 2.7-3.0 g / L.

7. The method for preparing perovskite thin films according to claim 3, characterized in that, The mass-to-volume ratio of the morpholine guanidine hydrochloride to the perovskite precursor solution is 0.5-5 mg / mL; the shaking process conditions are: shaking at a frequency of 1000-3000 times / minute for 1-5 hours until the solute is completely dissolved.

8. The method for preparing perovskite thin films according to claim 3, characterized in that, Add the anti-solvent in the later stage of spin coating. The specific process conditions are: spin coating at a speed of 3000-6000 rpm for 20-60 seconds, and add the anti-solvent 3-10 seconds before the end of spin coating.

9. The method for preparing perovskite thin films according to claim 3, characterized in that, The annealing process conditions are as follows: under an inert atmosphere, hold at 80-150℃ for 10-60 minutes, and then cool to room temperature in the furnace.

10. A perovskite solar cell, characterized in that, It includes a transparent conductive substrate, a hole transport layer, the perovskite thin film as described in claim 2, a perovskite upper surface passivation layer, an electron transport layer, a buffer layer, and an electrode layer, which are stacked sequentially.

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