Method for regulating and controlling lead iodide distribution in whole perovskite nucleation crystallization process and method for preparing perovskite solar cell

Abstract

The invention belongs to the technical field of perovskite solar cells, and particularly relates to a method for regulating and controlling lead iodide distribution in the whole process of perovskite nucleation crystallization and a method for preparing a perovskite solar cell. TBA (tert-butyl formamidine hydrochloride) is added in the whole nucleation and crystallization process of the perovskite layer to regulate and control the distribution of lead iodide. Through the whole process of lead iodide management, the improvement of the perovskite crystal quality, the management of the crystal boundary and the regulation and control of the residual lead iodide are realized, and finally the improvement of the efficiency and the stability of the device is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite solar cells, and in particular relates to a method for regulating the distribution of lead iodide in the whole process of perovskite nucleation and crystallization and a method for preparing a perovskite solar cell. Background Art

[0002] Organic-inorganic metal halide perovskites have been widely studied due to their excellent optoelectronic properties such as high absorption coefficient, low exciton binding energy, long carrier lifetime, and adjustable band gap. In the past decade, the photoelectric conversion efficiency has achieved rapid development from 3.8% to 26%. However, the current perovskite research is limited by the inherent limitations of polycrystalline growth, and there are a large number of defects on the surface, resulting in low carrier extraction and transmission efficiency. The negative impact of light and humidity in the external environment on the device causes the defects to cause rapid degradation, causing stability problems for the device. In addition, the random distribution of lead iodide will also lead to a large number of defects, which will cause non-radiative recombination losses during the operation of the device, reducing the efficiency and stability of the device.

[0003] At present, the main method used to solve the above problems is bulk additives to improve the crystal quality of the active layer and reduce the defect density. The existing literature also records the method of solving the distribution of lead iodide. However, the specific process and flow of lead iodide management are not recorded in the existing technical literature. Therefore, the regulation process of lead iodide and the method of improving crystal quality need further research. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for regulating the distribution of lead iodide during the whole process of perovskite nucleation and crystallization and a method for preparing a perovskite solar cell.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for regulating the distribution of lead iodide during the whole process of perovskite nucleation and crystallization, wherein the distribution of lead iodide is regulated by adding tert-butylformamidine hydrochloride (TBA) during the whole process of perovskite layer nucleation and crystallization.

[0007] Specifically, tert-butylformamidine hydrochloride (TBA) is added to the perovskite precursor solution to form a two-dimensional perovskite seed crystal, and then the distribution and orientation of lead iodide are regulated by passivating the perovskite grain boundaries during the crystallization process; wherein, the added concentration of tert-butylformamidine hydrochloride is 0.4 mg / ml.

[0008] A method for preparing a polycrystalline perovskite film is provided, wherein tert-butylformamidine hydrochloride is added to a perovskite precursor to prepare the polycrystalline perovskite film.

[0009] Tert-butylformamidine hydrochloride is dissolved in a mixed solution of DMF and DMSO, and then added into a perovskite precursor solution; the mixed solution is spin-coated on a substrate surface, and then annealed to form a perovskite polycrystalline film.

[0010] A method for preparing a perovskite solar cell using the perovskite polycrystalline film, wherein the perovskite solar cell comprises, from bottom to top, a conductive glass substrate / an electron transport layer / the perovskite polycrystalline film / a passivation layer / a hole transport layer / a metal electrode.

[0011] Specifically:

[0012] S1, clean the transparent conductive substrate and dry it with a nitrogen gun, first treat the conductive substrate with PLASMA, spin-coat an electron transport layer on the surface of the transparent substrate, and finally perform annealing;

[0013] S2, dissolving the perovskite precursor raw material in a mixed solvent, and dissolving it through a vortex oscillator until it is clear, to obtain a perovskite precursor solution;

[0014] S3, dissolving tert-butylformamidine hydrochloride in a mixed solution of DMF and DMSO, and then adding the mixture to the perovskite precursor solution of S2 to obtain a mixed solution;

[0015] S4, dripping the mixed solution of S3 onto the surface of the conductive substrate containing the electron transport layer prepared in S1 for spin coating, and dripping the anti-solvent at the 10th second before the end of the spin coating; annealing after the spin coating to form a conductive substrate of a perovskite polycrystalline thin film;

[0016] S5, cooling the conductive substrate with the perovskite polycrystalline film in S4 to room temperature, and then spreading a layer of isopropanol solution of phenylethylammonium iodide (PEAI) on the surface of the film to form a passivation layer on the surface of the perovskite;

[0017] S6, depositing another layer of hole transport material on the surface of the passivation layer of S5;

[0018] S7. Depositing the metal as an electrode on the substrate of S6 to obtain a perovskite solar cell.

[0019] The conductive substrate in S1 is FTO; the electron transport layer is SnO 2 ; Spin coating conditions: 3wt% SnO 2 The colloid was spin-coated at a speed of 3700 rpm for 30 s; the annealing conditions were annealing time of 30 min and temperature of 150°C.

[0020] The perovskite precursor raw materials in S2 are cesium iodide (CsI), methylamine chloride (MACl), methylamine iodide (MAI), methylammonium iodide (FAI), lead iodide (PbI 2) are mixed in a molar ratio of 0.05:0.20:0.10:1.40:1.68; the mixed solvent is obtained by mixing DMF and DMSO in a volume ratio of 4:1.

[0021] The added concentration of tert-butylformamidine hydrochloride in S3 is 0.4 mg / ml.

[0022] The anti-solvent in S4 is ethyl acetate, and the molar concentration of the perovskite precursor substance is 1.68M.

[0023] The concentration of the isopropanol solution of S5 phenethylammonium iodide (PEAI) is 2.0-2.5 mg / ml.

[0024] The hole transport layer in S6 is Spiro-OMeTAD, and each 1 mL of chlorobenzene contains 80-100 mg of Spiro-OMeTAD powder, 25-30 μL of tetra-tert-butylpyridine solution, 10-20 μL of acetonitrile solution containing lithium bis-trifluoromethanesulfonyl imide, and 10-20 μL of acetonitrile solution containing FK209 Co(III)TFSI.

[0025] The S7 places the aged perovskite device into a mask with suitable specifications, uses a vacuum coating machine, and coats the perovskite device with a thickness of at least 1×10 -7 Pa under high vacuum conditions. By evaporating 8nm molybdenum oxide and 100nm silver electrode at a rate of , the prepared perovskite solar cell can be obtained.

[0026] Principle of the present invention:

[0027] In order to solve the uncontrolled process of perovskite nucleation and crystallization, the present invention introduces tert-butylformamidine hydrochloride (TBA) into the perovskite precursor solution, which can achieve the regulation of the distribution of lead iodide, and then improve the crystallization quality of perovskite. In addition, during the annealing process, tert-butylformamidine or the two-dimensional perovskite composed thereof will be enriched at the grain boundary, inhibiting the decomposition of perovskite, solidifying the grain boundary, and realizing the appearance of vertically oriented lead iodide flaky crystals on the surface of perovskite grains. Therefore, since the crystallization quality of perovskite is improved, the grain boundary is passivated, and the distribution of lead iodide is regulated, the efficiency and stability of the device are effectively improved.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention successfully regulates the nucleation and crystallization process of the perovskite layer by adding tert-butylformamidine hydrochloride (TBA), realizes grain boundary passivation and the regulation of lead iodide, and proposes a specific method for the full-process regulation of lead iodide, studies the addition of TBA and the strong interaction between TBA and lead iodide, and realizes the improvement of perovskite crystallization quality, grain boundary management, and regulation of residual lead iodide through the full-process lead iodide management, and finally realizes the improvement of device efficiency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the preparation process of the perovskite polycrystalline thin film of the present invention;

[0031] Figure 2 Schematic diagram of the effect of TBA addition on the nucleation process of perovskite wet film in Example 1 of the present invention;

[0032] Figure 3 Schematic diagram of the effect of TBA addition on the perovskite crystallization process in Example 1 of the present invention;

[0033] Figure 4 This is a Kelvin probe microscope image of the perovskite film after crystallization in Example 1 of the present invention;

[0034] Figure 5 This is a grazing incidence small-angle X-ray diffraction image of the perovskite film before and after optimization in Example 1 of the present invention.

[0035] Figure 6 The distribution diagram of lead iodide in the perovskite film before and after optimization derived from grazing incidence small angle X-ray diffraction in Example 1 of the present invention;

[0036] Figure 7 The steady-state and transient fluorescence spectra of the perovskite film before and after optimization in Example 1 of the present invention;

[0037] Figure 8 The JV curves of the battery device before and after optimization of Example 1 of the present invention;

[0038] Fig. 9 This is the stability curve of the battery device before and after optimization of Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0040] Example 1

[0041] Preparation of polycrystalline perovskite thin films

[0042] Tert-butylformamidine hydrochloride was dissolved in a mixed solution of DMF and DMSO (volume ratio of 4:1), and then added to the perovskite precursor solution at 0.4 mg / ml. The mixed solution was spin-coated on the substrate surface by a spin coater, and then annealed to form a perovskite polycrystalline film Cs 0.05 MA 0.1 FA 0.85 PbI 3 , to achieve the regulation of the perovskite crystallization process ( Figure 1 ).

[0043] In order to show the effect of TBA addition on the nucleation and crystallization process of perovskite, the perovskite polycrystalline film was observed by microscope. Figure 2 ,Depend on Figure 2 It can be seen that TBA preferentially reacts with lead iodide to generate two-dimensional perovskite seed crystals, so there are more nucleation points.

[0044] Depend on Figure 3 It can be seen that through annealing, the perovskite film with TBA participating in the reaction can generate larger and more uniform grains with relatively less extrusion. In the later stage of crystallization, TBA will be enriched at the grain boundaries, reducing the decomposition of perovskite at the grain boundaries, and finally lead iodide will appear on the grain surface in a flake-like morphology.

[0045] The changes at the grain boundaries can also be confirmed by Kelvin probe microscopy. Figure 4 , obvious differences appear at the grain boundaries of the perovskite film in which TBA participates in the reaction.

[0046] Using grazing incidence small angle X-ray diffraction to monitor ( Figure 5 ), and found that the crystal quality and crystal orientation of perovskite polycrystalline films with different TBA addition concentrations were significantly optimized, and the lead iodide content at the grain boundary was reduced, while the lead iodide content on the grain surface was increased ( Figure 6), the distribution of lead iodide is significantly optimized. Through steady-state and transient fluorescence, the fluorescence intensity is significantly improved, and the fluorescence lifetime is also improved. Figure 7 .

[0047] Example 2

[0048] Preparation of perovskite solar cells

[0049] S1. Take the etched conductive substrate FTO and clean it. Soak it in the glass cleaning machine, ionized water, deionized water, isopropanol, and isopropanol in the order of 15 minutes of ultrasonic treatment, and then blow it dry with a nitrogen gun; treat it in a plasma machine (PLAMA) for 15 minutes. Spin coating at a speed of 30 seconds, and then quickly place it on a hot stage at 150℃ for annealing for 30 minutes to obtain SnO 2 Electron transport layer.

[0050] S2. According to the stoichiometric ratio, weigh a certain amount of the perovskite precursor raw materials: cesium iodide (CsI), methylamine chloride (MACl), methylamine iodide (MAI), methylammonium iodide (FAI), lead iodide (PbI 2 ) was dissolved in a mixed solvent with a ratio of 0.05:0.20:0.1:1.40:1.68, which was dissolved in a mixed solvent of DMSO and DMF (volume ratio of 4:1), and dissolved by vortexing for 1 h to obtain a 1.68 M perovskite precursor clear solution.

[0051] S3, dissolve tert-butylformamidine hydrochloride in a mixed solution of DMF and DMSO (volume ratio of 4:1), and then add 0.4 mg / ml to the precursor solution of S2 to obtain a mixed solution.

[0052] S4, the SnO 2 The FTO substrate of the electron transport layer was placed on a spin coater, 50 μL of the mixed solution of S3 was added, and the substrate was spin-coated at a speed of 5000 rpm for 40 seconds. At the 10th second, 0.5 mL of ethyl acetate anti-solvent was injected. After the spin coating was completed, the substrate was quickly transferred to a 100°C hot plate and heated for 60 minutes to obtain a conductive substrate of the perovskite polycrystalline thin film.

[0053] S5. After the conductive substrate with the perovskite polycrystalline film spun in S4 is cooled to room temperature, 60 μL of 2.5 mg / ml isopropanol solution of phenylethylammonium iodide (PEAI) is added to the surface of the wafer at a rotation speed of 4000 rpm to ensure the formation of a passivation layer.

[0054] S6, add 40 μL of the hole transport layer Spiro-OMETAD solution to the substrate after interface passivation of S5, spin-coat at 3000 rpm for 30 seconds, and age in a low humidity environment for 12 hours after spin coating. The hole transport layer is Spiro-OMeTAD, and each 1 mL of chlorobenzene contains 80-100 mg of Spiro-OMeTAD powder, 25-30 μL of tetra-tert-butylpyridine solution, 10-20 μL of acetonitrile solution containing lithium bis-trifluoromethanesulfonyl imide, and 10-20 μL of acetonitrile solution containing FK209 Co(III)TFSI.

[0055] S7, MoO 3 and silver was deposited onto the hole transport layer of S6 (using a vacuum coater at a minimum of 1 × 10 -7 Pa under high vacuum conditions. 8nm molybdenum oxide and 100nm silver electrode are evaporated at a rate of 1000nm to obtain the prepared perovskite solar cell.

[0056] Performance of perovskite solar cells Figure 8 (Battery performance), Fig. 9 (Battery Stability), by Figure 8 and Fig. 9 It can be seen that due to the optimization of crystal quality, passivation of grain boundaries and regulation of lead iodide, the device performance and stability are significantly improved.

[0057] Comparative Example 1

[0058] Compared with Example 2, tert-butylformamidine hydrochloride is not added, specifically:

[0059] S1. Take the etched conductive substrate FTO and clean it, in the order of glass cleaning machine, ionized water, deionized water, isopropanol, isopropanol, ultrasonic soaking for 15 minutes, and then blown dry with a nitrogen gun; treat it in a plasma machine (PLAMA) for 15 minutes. Take a 3wt% SnO 2 The aqueous solution was dripped onto the ITO surface, spin-coated at 3700 rpm for 30 seconds, and then quickly placed on a 150°C hot plate for annealing for 30 minutes to obtain SnO 2 Electron transport layer.

[0060] S2. According to the stoichiometric ratio, weigh a certain amount of the perovskite precursor raw materials: cesium iodide (CsI), methylamine chloride (MACl), methylamine iodide (MAI), methylammonium iodide (FAI), lead iodide (PbI 2) was dissolved in a mixed solvent in a ratio of 0.05:0.15:0.1:1.27:1.68, which was dissolved in a mixed solvent of DMSO and DMF (ratio of 4:1), and dissolved by vortexing for 2 h to obtain a 1.8 M clear solution of the perovskite precursor.

[0061] S3, S1 with SnO 2 The ITO substrate of the electron transport layer was placed on a spin coater, 50 μL of S2 perovskite precursor solution was added, and the substrate was spin-coated at 5000 rpm for 40 seconds. In the 10th second before the spin coating, 0.2 mL of ethyl acetate antisolvent was injected. After the spin coating was completed, the substrate was quickly transferred to a 100°C hot plate and heated for 60 minutes.

[0062] S4. After cooling to room temperature, the substrate with the perovskite in S3 is cooled to room temperature, and then 60 μL of 2.5 mg / ml isopropanol solution of phenylethylammonium iodide (PEAI) is added to the surface of the wafer at a rotation speed of 4000 rpm to ensure the formation of a passivation layer.

[0063] S5, add 40 μL of Spiro-OMETAD solution of hole transport layer, spin-coat at 3000 rpm for 30 s, and age in low humidity environment for 12 h (use vacuum coating machine, at least 1×10 -7 Pa under high vacuum conditions. 8nm molybdenum oxide and 100nm silver electrode are evaporated at a rate of 100nm to complete the perovskite solar cell.

[0064] Perovskite solar cell performance and device stability Figure 8 and Fig. 9 (The device containing tert-butylformamidine can obtain an open circuit voltage of 1.17V, a fill factor of 79%, and a current of 25.5mA / cm 2 The short-circuit current and photoelectric conversion efficiency of 23.5% are achieved with the standard device, while the open-circuit voltage of 1.15V, the fill factor of 75%, and the photoelectric conversion efficiency of 25.0mA / cm 2 The short-circuit current and photoelectric conversion efficiency of 21.5%. ).

[0065] From the comparison between the embodiment and the comparative example, it can be seen that the device after lead iodide management in the embodiment of the present invention can achieve a device efficiency of 23.5% (see Figure 8). The present invention utilizes the addition of tert-butylformamidine hydrochloride (TBA) to successfully regulate the nucleation and crystallization process of the perovskite layer, realizes grain boundary passivation and the regulation of lead iodide, and the present invention proposes detailed process conditions for the full regulation of lead iodide, proves the addition of TBA, and due to the strong interaction between TBA and lead iodide, through the management of lead iodide throughout the process, the improvement of the perovskite crystallization quality, the management of grain boundaries, and the regulation of residual lead iodide are achieved, and finally the improvement of device efficiency and stability is achieved. The device with global regulation of lead iodide can maintain 90% of the initial efficiency in a nitrogen atmosphere, while the original device can only maintain more than 65% of the initial efficiency (see Fig. 9 ).

Claims

1. A method for regulating the distribution of lead iodide during the whole process of perovskite nucleation and crystallization, characterized in that: The distribution of lead iodide can be regulated by adding tert-butylformamidine hydrochloride (TBA) during the entire process of perovskite layer nucleation and crystallization.

2. The method for regulating the distribution of lead iodide during the whole process of perovskite nucleation and crystallization according to claim 1, characterized in that: Tert-butylformamidine hydrochloride (TBA) is added to the perovskite precursor solution to form two-dimensional perovskite seed crystals, and then the distribution and orientation of lead iodide are regulated by passivating the perovskite grain boundaries during the crystallization process; wherein, the added concentration of tert-butylformamidine hydrochloride is 0.4 mg / ml.

3. A method for preparing a polycrystalline perovskite thin film according to claim 1, characterized in that: By the method of claim 1, tert-butylformamidine hydrochloride is added to a perovskite precursor to prepare a perovskite polycrystalline thin film.

4. The perovskite polycrystalline thin film according to claim 3, characterized in that: Tert-butylformamidine hydrochloride is dissolved in a mixed solution of DMF and DMSO, and then added into a perovskite precursor solution; the mixed solution is spin-coated on a substrate surface, and then annealed to form a perovskite polycrystalline film.

5. A method for preparing a perovskite solar cell using the perovskite polycrystalline thin film according to claim 3, characterized in that: The perovskite solar cell comprises, from bottom to top, a conductive glass substrate / an electron transport layer / the perovskite polycrystalline film as claimed in claim 3 / a passivation layer / a hole transport layer / a metal electrode.

6. The method according to claim 5, characterized in that: S1, cleaning the transparent conductive substrate and spin coating an electron transport layer on the surface of the transparent substrate, and then performing annealing treatment; S2, dissolving the perovskite precursor raw material in a mixed solvent until it is clear, to obtain a perovskite precursor solution; S3, dissolving tert-butylformamidine hydrochloride in a mixed solution of DMF and DMSO, and then adding the mixture to the perovskite precursor solution of S2 to obtain a mixed solution; S4, dripping the mixed solution of S3 onto the surface of the conductive substrate containing the electron transport layer prepared in S1, and performing spin coating, and annealing to form a conductive substrate of a perovskite polycrystalline thin film; S5, cooling the conductive substrate with the perovskite polycrystalline film in S4 to room temperature, and then spreading a layer of isopropanol solution of phenylethylammonium iodide (PEAI) on the surface of the film to form a passivation layer on the surface of the perovskite; S6, depositing another layer of hole transport material on the surface of the passivation layer of S5; S7. Depositing the metal as an electrode on the substrate of S6 to obtain a perovskite solar cell.

7. The method according to claim 6, characterized in that: The conductive substrate in S1 is FTO; the electron transport layer is SnO2; the spin coating conditions are: rotation speed 3700 rpm, spin coating time 30 s; the annealing conditions are annealing time 30 min, temperature 150°C.

8. The method according to claim 6, characterized in that: The perovskite precursor raw materials in S2 are cesium iodide (CsI), methylamine chloride (MACl), methylamine iodide (MAI), formamidine iodide (FAI), and lead iodide (PbI2) mixed in a molar ratio of 0.05:0.20:0.10:1.40:1.68; the mixed solvent is obtained by mixing DMF and DMSO in a volume ratio of 4:

1.

9. The method according to claim 6, characterized in that: The concentration of tert-butylformamidine hydrochloride added in S3 was 0.4 mg / ml.

10. The method according to claim 6, characterized in that: The hole transport layer in the S6 is Spiro-OMeTAD, and each 1 mL of chlorobenzene contains 80-100 mg of Spiro-OMeTAD powder, 25-30 μL of tetra-tert-butylpyridine solution, 10-20 μL of acetonitrile solution containing lithium bis-trifluoromethanesulfonyl imide, and 10-20 μL of acetonitrile solution containing FK209Co(III)TFSI.

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