Perovskite solar cell modified by inorganic passivation layer and preparation method thereof

Abstract

The application discloses a perovskite solar cell modified by an inorganic passivation layer and a preparation method, and the perovskite solar cell is prepared by oxidizing redundant lead iodide on a perovskite surface by using ammonium persulfate with strong oxidizability, and then forming a dense lead sulfate-lead oxide inorganic layer to passivate the perovskite film, so that a high-efficiency and stable perovskite cell is prepared. The perovskite film is treated by using a passivation agent solution, and the photoelectric conversion efficiency of the prepared device can reach 24.98% at most. Meanwhile, the perovskite film treated by the passivation agent has excellent photo-thermal stability. The perovskite device prepared by the application has a remarkable passivation effect, and the waterproof performance of the perovskite material is remarkably improved, which has important significance for performance improvement and commercial production of the perovskite.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cells, specifically relating to an inorganic passivation layer modified perovskite solar cell and its preparation method. Background Technology

[0002] Perovskite solar cells have attracted widespread attention in the field of solar cells due to their advantages such as high absorption coefficient, wide absorption range, and high conversion efficiency. Currently, research on perovskite solar cells mainly focuses on treating the perovskite surface with small organic molecules to passivate defects. These small organic molecules are inherently unstable, easily decomposing upon contact with water and oxygen, and also reacting with the perovskite itself. When these small molecules are introduced onto the perovskite surface after post-treatment, due to the weak interactions or relatively weak chemical bonds of the organic matter, they may desorb from the perovskite under long-term storage or operation, causing defects to re-expose; or they may migrate into the perovskite bulk phase, causing further degradation of the perovskite. Therefore, how to solve the problems caused by the passivation treatment with small organic molecules while simultaneously fabricating efficient and stable perovskite devices is a pressing technical challenge. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide an inorganic passivation layer modified perovskite solar cell and its preparation method, which is specifically achieved through the following technical solutions:

[0004] An inorganic passivation layer modified perovskite solar cell includes, from bottom to top, a positive substrate, a hole transport layer, a perovskite active layer, an active layer interface modification layer, an electron transport layer, a cathode modification layer, and a cathode. The active layer interface modification layer is an inorganic passivation layer formed by spin-coating ammonium persulfate inorganic salt onto the perovskite active layer.

[0005] Furthermore, the inorganic passivation layer is a lead sulfate-lead oxide inorganic passivation layer formed by the oxidation of ammonium sulfate.

[0006] Furthermore, the hole transport layer has a thickness of 5-15 nm, the perovskite active layer has a thickness of 600-700 nm, the active layer interface modification layer has a thickness of 5-20 nm, the electron transport layer has a thickness of 40-80 nm, the cathode modification layer has a thickness of 1-6 nm, and the cathode has a thickness of 120 nm.

[0007] Furthermore, the active layer interface modification layer is obtained by dissolving ammonium persulfate in isopropanol (IPA) and trifluoroethanol (TF-EtOH) to form a saturated solution at room temperature, which is then spin-coated onto the perovskite active layer and annealed at 100°C for 5 minutes.

[0008] A method for fabricating a perovskite solar cell modified with an inorganic passivation layer includes the following steps:

[0009] Select and clean the positive substrate, and then spin-coat the hole transport layer, perovskite active layer, active layer interface modification layer, electron transport layer, cathode modification layer, and cathode sequentially from bottom to top on the positive substrate; wherein the active layer interface modification layer is a dense inorganic passivation layer of lead sulfate and lead oxide formed by oxidizing the excess lead iodide on the perovskite surface with ammonium persulfate, a strongly oxidizing inorganic salt, spin-coated on the perovskite active layer.

[0010] The positive substrate is a flexible or rigid substrate with a uniformly deposited indium tin oxide (ITO), frosted metal oxide (FTO), silicon (Si), or zinc oxide (CIGS) layer. In a preferred embodiment of this solution, the positive substrate is selected as a flexible or rigid substrate with a deposited indium tin oxide (ITO) layer, and the thickness of the indium tin oxide (ITO) layer is 100 nm.

[0011] Further, the hole transport layer is one of 2-pyrene-ethylphosphonic acid, 2-(9H-carbazole-9-yl)ethylphosphonic acid, 2-(3,6-dimethoxy-9H-carbazole-9-yl)ethylphosphonic acid, and 4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid, spin-coated onto the anode substrate. Preferably, 2-(9H-carbazole-9-yl)ethylphosphonic acid is dissolved in ethanol to form a solution with a mass concentration of 0.6 mg / mL, and then a 2-(9H-carbazole-9-yl)ethylphosphonic acid film with a thickness of 5-15 nm is prepared by solution spin-coating.

[0012] Furthermore, the perovskite active layer is prepared by a one-step spin-coating method using a perovskite precursor solution combined with an annealing process. Specifically, after obtaining the perovskite precursor solution, a liquid-phase one-step spin-coating method is used to spin-coat it onto a flexible or rigid substrate with a charge carrier transport layer. After spin-coating, the substrate is heated at 120°C for 30 minutes.

[0013] Furthermore, the electron transport layer is a C60 thin film, a PCBM thin film, or a SnO film deposited on the interface modification layer of the active layer. x One type of thin film. In a preferred embodiment of this solution, the thickness of the electron transport layer is 45-60 nm. Additionally, the thickness of the perovskite active layer is 600-700 nm, the thickness of the active layer interface modification layer is 5-10 nm, the thickness of the hole transport layer is 10 nm, the thickness of the cathode modification layer is 6-10 nm, and the thickness of the cathode is 120 nm.

[0014] Furthermore, the negative modification layer is a BCP deposited on the electron transport layer, and the cathode is a gold or silver film vacuum thermally deposited on the hole transport layer.

[0015] The perovskite active layer is prepared by a one-step spin-coating method using a perovskite precursor solution, combined with an annealing process. In the preparation of the perovskite precursor solution, site A uses a mixed ratio of FA (formamidinium ion), MA (methylamine ion), and Cs (cesium ion); X is the same I (iodine), Br (bromine), and Cl (chlorine) ions, or different I, Br, and Cl halide ions; the precursor solution is selected from solvents capable of dissolving perovskite materials, such as DMF, DMSO, γ-butyrolactone, IPA, and CB. In this scheme, AX is selected as FAI, MACl, FABr, MABr, FACl, or MAI, with FAI and MABr being preferred.

[0016] The dense inorganic layer formed by the redox reaction of a strong oxidizing inorganic salt with excess lead iodide on the perovskite surface serves as an interface modification layer between the perovskite active layer and the electron transport layer. This approach offers several advantages: firstly, it regulates the interface energy levels and passivates surface defects in the perovskite layer, improving its photothermal stability; secondly, it addresses the problem of poor stability and easy desorption of organic small-molecule passivating agents, leading to the re-exposure of defects. In this application, an inorganic passivation layer obtained by oxidation with strong oxidizing ammonium persulfate is used as a modification layer. This layer modifies the already formed perovskite active layer for post-treatment of the perovskite film and does not affect the crystallization process of the perovskite film. Furthermore, the inorganic passivation layer in this application features N-type doping, which not only improves the stability of the perovskite solar cell but also further enhances the photoelectric conversion efficiency.

[0017] The structure of the inorganic salt of strong oxidizing ammonium persulfate is as follows:

[0018]

[0019] The above-described solution addresses the inherent instability of common small-molecule organic passivating agents while simultaneously improving device performance and stability. Compared to the 23.25% efficiency of the reference device without interface modification, the photoelectric conversion efficiency of the device modified with the inorganic passivation layer increased to 24.98%, while also improving photovoltaic performance parameters such as open-circuit voltage (Voc), short-circuit current (Jsc), and photoelectric conversion efficiency (PCE). More importantly, compared to traditional small-molecule organic passivating agents, the device treated with strongly oxidizing ammonium persulfate exhibits superior photothermal stability. The fabrication process of this invention is simple and suitable for the large-scale industrial production of perovskite devices. Attached Figure Description

[0020] Figure 1 This invention relates to the battery structure of an inorganic passivation layer modified perovskite solar cell.

[0021] Figure 2These are scanning electron micrographs (SEM) of the surface of formamidinium lead iodide perovskite films modified with and unmodified with ammonium persulfate; where a is the SEM image of the unmodified perovskite film surface and b is the SEM image of the perovskite film surface treated with saturated ammonium persulfate isopropanol solution.

[0022] Figure 3 It is a fast steady-state photoluminescence spectral imaging (PL mapping) of the surface of ammonium persulfate modified and unmodified formamidinium lead iodide perovskite thin films;

[0023] Figure 4 The changes in X-ray polycrystalline diffraction (XRD) of ammonium persulfate modified and unmodified perovskite films after heating at 85°C in a glove box for 48 hours and 96 hours and placing them in air with a relative humidity of 65% for 48 hours and 96 hours, respectively.

[0024] Figure 5 The optimal voltage-current curves and device parameters of perovskite solar cells modified with and without ammonium persulfate are presented. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] Example 1

[0027] Preparation of perovskite solar cells modified with an inorganic passivation layer by surface self-oxidation using ammonium persulfate:

[0028] A formamidinium cesium lead-iodine perovskite solar cell containing a sulfate inorganic passivation interface modification layer has the following device structure: ITO / 2PACz / FA0.95Cs0.05PbI3 / inorganic passivation layer / C60 / BCP / Ag. The ITO anode has a thickness of 100 nm and a sheet resistance of 15 Ω. Before use, the anode was ultrasonically cleaned with deionized water, acetone, and isopropanol, then dried with nitrogen and treated with a plasma cleaner for 25 min. The hole transport layer 2PACz has a thickness of 5 nm. The hole transport layer was spin-coated onto the ITO layer in a nitrogen glove box (H2O and O2 content were both less than 1 ppm), and then annealed. The spin-coating rate was 3000 rpm, the spin-coating time was 40 s, the annealing temperature was 110℃, and the annealing time was 20 min. 70 μL of FA0.95Cs0.05PbI3 precursor solution was dropped onto a 2PACz film. The film was spin-coated at 5000 rpm for 50 s. At the last 10 s, 200 μL of chlorobenzene (CB) was added dropwise at a uniform rate, followed by annealing to obtain a 700 nm thick perovskite active layer. The FA0.95Cs0.05PbI3 precursor solution had a molar concentration of 1.7 M, with an additional 5% excess of lead iodide. The volume ratio of DMF to DMSO in the mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) was 5:1. An additional 15% MACl was added as an additive to the precursor solution. The prepared mixed solution was stirred on a magnetic stirrer at room temperature until completely dissolved. The perovskite film preparation method involved spin-coating the above clarified solution onto a flexible or rigid substrate with a charge carrier transport layer using a one-step liquid-phase spin-coating method. After spin-coating, the substrate was heated at 120 °C for 30 minutes.

[0029] The inorganic passivation layer is prepared by dissolving ammonium persulfate in a mixed solution of isopropanol (IPA) and trifluoroethanol (v / v = 1:2) to form a saturated solution, filtering, and then spin-coating followed by annealing. The film thickness is 5-10 nm. The electron transport layer PC61BM in the battery structure is prepared as follows: the precursor solution solvent is CB. A 20 mg / mL PC61BM precursor solution is spin-coated onto the perovskite layer in a nitrogen-atmosphere glove box to obtain a 60 nm thick electron transport layer. Annealing is not required. The spin-coating rate is 3000 rpm, and the spin-coating time is 30 s. The cathode modification layer BCP in the battery structure is prepared by vacuum thermal evaporation, with a film thickness of 6 nm and a evaporation rate of [missing information].

[0030] The structure of the perovskite solar cell prepared above is as follows: Figure 1 As shown.

[0031] Control group 1

[0032] In control group 1, no ammonium persulfate solution oxidation modification was performed, and other conditions were the same as in Example 1.

[0033] Example 2

[0034] 1) Prepare a 1.70M concentration of FA at room temperature. 0.95 Cs 0.05 PbI3 perovskite precursor solution was stirred on a magnetic stirrer until completely dissolved;

[0035] 2) The above clear solution was spin-coated onto a quartz substrate using a one-step liquid phase spin-coating method. After spin-coating, the substrate was heated at 110°C for 30 minutes.

[0036] 3) After ammonium persulfate is dissolved in a mixed solution of isopropanol (IPA) and trifluoroethanol (v / v = 1:2) to form a saturated solution, it is filtered and then treated on a perovskite film by solution spin coating and annealed at 100°C for 5 minutes.

[0037] Control group 2

[0038] Control group 2 was not modified, and other conditions were the same as in Example 2.

[0039] Effect detection:

[0040] (1) Perovskite device performance testing

[0041] The photoelectric conversion test was conducted using an AAA-grade solar simulator, with a test step of 5ms and an effective area of ​​0.1cm². 2 The bias voltage is from -0.2 to 1.2V or from 1.2 to -0.2V.

[0042] like Figure 5 As can be seen, the perovskite device obtained in Example 1, which contains a lead sulfate-lead oxide inorganic passivation layer, has the highest photoelectric conversion efficiency of 24.98%, while the highest photoelectric conversion efficiency of the unmodified perovskite device in Control Group 1 is 23.25%. Therefore, the photoelectric conversion efficiency of the perovskite device containing the lead sulfate-lead oxide inorganic passivation layer is significantly improved.

[0043] (2) Test of calcium peptide mineral membrane morphology:

[0044] This method utilizes scanning electron microscopy (SEM) equipment to observe the perovskite films obtained in Example 2 and Control Group 2 under ultra-high vacuum. Figure 2 a and 2b are electron microscope images of the perovskite films in control group 2 and example 2, respectively.

[0045] from Figure 2 As can be seen, compared with the perovskite film of control group 2, the film of Example 2, which underwent oxidation treatment on the perovskite surface, did not show significant changes. This indicates that the strongly oxidizing ammonium persulfate solution did not damage the perovskite surface, thus ensuring the structural stability of the perovskite film.

[0046] Rapid imaging using steady-state fluorescence spectroscopy yielded PL mapping images, as shown below. Figure 3 As shown, from Figure 3 It can be seen that, compared with the perovskite film of control group 2, the film of Example 2 has a significantly stronger intensity of surface photoluminescence and a more homogeneous fluorescence spectrum, indicating that there are fewer defects on the overall surface of the film.

[0047] By combining the two surface morphology testing methods, we can conclude that after the ammonium sulfate oxidation treatment, the perovskite film of Example 2 did not undergo significant changes on the film surface, while the defects on the perovskite surface were significantly reduced.

[0048] (3) X-ray polycrystalline diffraction test:

[0049] The perovskite films obtained in Example 2 and Control Group 2 were tested using X-ray polycrystalline diffraction under the same conditions, such as... Figure 4 As shown. Figure 4 These are the thin film crystal structure diagrams obtained by X-ray polycrystalline diffraction testing after the thin films of Example 2 and Control Group 2 were subjected to humidity aging and high temperature aging, respectively.

[0050] Depend on Figure 4 As can be seen, the humidity stability comparison was conducted at 65% relative humidity for 48 and 96 hours. In the initial state, neither the films of control group 2 nor example 2 showed a peak at 12.7°, indicating that lead iodide on the perovskite surface was not extensively exposed. After 48 and 96 hours, the XRD patterns of control group 2 showed the formation of a large amount of lead iodide, with its diffraction intensity continuously increasing with moisture erosion. In contrast, the perovskite film of example 2, treated with ammonium persulfate, showed almost no peak near 12.7°, maintaining a good film condition without decomposition. Therefore, it is concluded that the film forming a lead sulfate-lead oxide inorganic passivation layer after ammonium persulfate treatment exhibits superior moisture resistance. Moisture intrusion is a significant cause of performance degradation in perovskite solar cells under operating conditions.

[0051] The thermal stability was compared in a nitrogen-atmospheric glove box under continuous heating at 85°C. Initially, neither the films of Control Group 2 nor Example 2 showed a peak at 12.7°C, indicating that lead iodide on the perovskite surface was not significantly exposed. After 48 and 96 hours of heating, the XRD patterns of Control Group 2 showed a strengthened peak at 12.7°C, representing significant lead iodide exposure. This indicates that the perovskite underwent continuous degradation during heating, leading to lead iodide formation. In contrast, the film of Example 2, which formed an inorganic passivation layer after ammonium sulfate treatment, showed a significantly improved degree of degradation.

Claims

1. A perovskite solar cell modified with an inorganic passivation layer, characterized in that... The perovskite solar cell comprises, from bottom to top, a positive substrate, a hole transport layer, a perovskite active layer, an active layer interface modification layer, an electron transport layer, a cathode modification layer, and a cathode. The active layer interface modification layer is an inorganic passivation layer formed by spin-coating ammonium persulfate inorganic salt onto the perovskite active layer. Specifically, the inorganic passivation layer is a lead sulfate-lead oxide inorganic passivation layer formed by the oxidation of ammonium sulfate. The active layer interface modification layer is obtained by dissolving ammonium persulfate in isopropanol (IPA) and trifluoroethanol (TF-EtOH) to form a saturated solution at room temperature, then spin-coating it onto the perovskite active layer, and annealing it at 100°C for 5 minutes.

2. The perovskite solar cell modified with an inorganic passivation layer as described in claim 1, characterized in that... The hole transport layer has a thickness of 5-15 nm, the perovskite active layer has a thickness of 600-700 nm, the active layer interface modification layer has a thickness of 5-20 nm, the electron transport layer has a thickness of 40-80 nm, the cathode modification layer has a thickness of 1-6 nm, and the cathode has a thickness of 120 nm.

3. A method for preparing an inorganic passivation layer modified perovskite solar cell according to any one of claims 1-2, characterized in that... Includes the following steps: Select and clean the positive substrate, and then spin-coat the hole transport layer, perovskite active layer, active layer interface modification layer, electron transport layer, cathode modification layer, and cathode sequentially from bottom to top on the positive substrate; wherein the active layer interface modification layer is a dense inorganic passivation layer of lead sulfate and lead oxide formed by oxidizing the excess lead iodide on the perovskite surface with ammonium persulfate, a strongly oxidizing inorganic salt, spin-coated on the perovskite active layer.

4. The method for preparing an inorganic passivation layer modified perovskite solar cell as described in claim 3, characterized in that... The hole transport layer is one of 2-pyrene-ethyl phosphoric acid, 2-(9H-carbazole-9-yl)ethylphosphonic acid, 2-(3,6-dimethoxy-9H-carbazole-9-yl)ethylphosphonic acid, and 4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid, spin-coated onto the anode substrate.

5. The method for preparing an inorganic passivation layer modified perovskite solar cell as described in claim 3, characterized in that... The perovskite active layer is prepared by a one-step spin-coating method using a perovskite precursor solution combined with an annealing process. Specifically, after obtaining the perovskite precursor solution, a liquid-phase one-step spin-coating method is used to spin-coat it onto a flexible or rigid substrate with a charge carrier transport layer. After spin-coating, the substrate is heated at 120°C for 30 minutes.

6. The method for preparing an inorganic passivation layer modified perovskite solar cell as described in claim 3, characterized in that... The electron transport layer is one of the following: a C60 thin film, a PCBM thin film, or a SnOx thin film deposited on the interface modification layer of the active layer.

7. The method for preparing an inorganic passivation layer modified perovskite solar cell as described in claim 3, characterized in that... The negative modification layer is a BCP deposited on the electron transport layer, and the cathode is a gold or silver film deposited on the cathode modification layer by vacuum thermal evaporation.

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