Perovskite thin film based on gas-phase inorganic matter passivator and preparation and application thereof

Abstract

The invention discloses a perovskite thin film based on a gas phase inorganic matter passivator and preparation and application thereof. The perovskite thin film comprises a perovskite layer and a divalent metal halide passivation layer deposited on the perovskite layer in a vapor phase mode. According to the method, the divalent metal halide is used for gas-phase inorganic matter passivation, and the passivation layer can well reduce perovskite interface defects and improve the interface stability by controlling the substrate temperature, the substrate rotation speed, the evaporation rate of a divalent metal halide evaporation source and the film deposition thickness of the gas-phase inorganic matter passivation layer in the passivation process; therefore, the photoelectric conversion efficiency and the stability of the solar cell are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular, to a perovskite film based on a gas-phase inorganic passivator, its preparation and application. Background Art

[0002] Perovskite solar cells have become a research hotspot in the field of solar cells due to their excellent optoelectronic properties and relatively simple manufacturing process. Perovskite materials have excellent light absorption properties, high electron mobility, and long carrier diffusion lengths. Currently, the efficiency of perovskite solar cells is increasing rapidly and gradually approaching that of silicon cells, showing great potential in the photovoltaic field. The high efficiency and stability of perovskite solar cells are closely related to the quality of the perovskite film. However, the films of perovskite materials often have surface defects, grain boundary problems, and unstable interfacial properties, which limit the optoelectronic properties of the perovskite film and the long-term stability of the solar cell. Surface defects not only reduce the light absorption and carrier collection efficiency but also may cause recombination losses, thus affecting the photoelectric conversion efficiency of the cell.

[0003] To overcome this problem, it is necessary to passivate the surface of the perovskite film, repair and suppress surface defects, thereby reducing the defect density at the surface and interface and improving the quality of the film. Currently, most passivation methods use liquid-phase treatment, which uses toxic solvents, is prone to introducing other impurities, and the liquid-phase method will cause a certain degree of damage to the interface of the humidity-sensitive perovskite film, affecting the cell performance. At the same time, it is difficult for the liquid-phase passivation method to ensure the coating uniformity of the passivation layer, and the repeatability is poor. The use of gas-phase passivation technology can stably achieve surface uniform passivation, and has the advantages of being able to precisely control the thickness, composition, and uniformity of the passivation layer, but the passivation effect is poor, thus affecting the optoelectronic properties of the perovskite film.

[0004] Therefore, it is necessary to provide a gas-phase passivation perovskite film solution to improve the optoelectronic properties of the perovskite film. Summary of the Invention

[0005] In view of this, the present application provides a perovskite film based on a gas-phase inorganic passivator, its preparation and application, to solve the problem of how to improve the surface defects of the perovskite film to enhance its optoelectronic properties.

[0006] To achieve the above technical purpose, the present application adopts the following technical solutions: In the first aspect, the present application provides a perovskite film based on a gas-phase inorganic passivator, including a perovskite layer and a divalent metal halide passivation layer deposited on the perovskite layer by gas-phase deposition.

[0007] Preferably, the chemical formula of the divalent metal halide is AX2; wherein, A is a divalent metal cation selected from the metal elements beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb); X is an anion selected from the halogen elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I).

[0008] Preferably, the thickness of the divalent metal halide passivation layer is 1-100 Å.

[0009] In a second aspect, the present application provides a method for preparing a perovskite film based on a vapor-phase inorganic passivating agent, comprising the following steps: S1. Obtain a perovskite layer; S2. Using the divalent metal halide as an evaporation source and the annealed perovskite layer as a substrate, perform vacuum thermal evaporation passivation to obtain the perovskite film based on the vapor-phase inorganic passivating agent.

[0010] Preferably, the vacuum thermal evaporation method includes single-source inorganic evaporation passivation, multi-source inorganic co-evaporation passivation, and multi-source inorganic layer-by-layer alternating evaporation passivation.

[0011] Preferably, the method for obtaining the perovskite layer includes one of two-source co-evaporation, three-source co-evaporation, and the solution method.

[0012] Preferably, the evaporation sources in the two-source co-evaporation are cesium iodide (CsI) and lead iodide (PbI2); the evaporation sources in the three-source co-evaporation are cesium iodide (CsI), lead iodide (PbI2), and organic ammonium salt.

[0013] Preferably, the temperature of the substrate is 20-80 °C, and the rotation speed of the substrate is 2-15 rpm.

[0014] Preferably, the annealing temperature is 50-100 °C, and the annealing time is 5-15 min.

[0015] In a third aspect, the present application provides a perovskite solar cell comprising a perovskite film based on a vapor-phase inorganic passivating agent.

[0016] The beneficial effects of the present application are as follows: The present application uses the vacuum thermal evaporation method to passivate the perovskite film with the vapor-phase inorganic material divalent metal halide, significantly reducing defects, effectively improving the quality and stability of the perovskite film, and significantly enhancing the efficiency of the prepared solar cell; The method of the present application uses gaseous inorganic substances to replace the traditional liquid-phase passivation process. On the one hand, it can solve the problems of using toxic organic solvents in the liquid-phase passivation of perovskite films and being prone to introducing impurities. On the other hand, it provides an alternative solution for the preparation of humidity-sensitive inorganic perovskite films, while improving the process operability and repeatability. The present application uses divalent metal halides for gaseous inorganic passivation. By controlling the substrate temperature, substrate rotation speed, evaporation rate of the divalent metal halide evaporation source, film deposition thickness of the gaseous inorganic passivation layer, annealing time and temperature after passivation, the passivation layer can better reduce the perovskite interface defects and improve the interface stability, thereby significantly improving the photoelectric conversion efficiency and stability of the solar cell. Description of the Drawings

[0017] Figure 1 It is the evaporation schematic diagram of the passivated perovskite film of the present application; wherein, 1 is the perovskite layer substrate after annealing, and 2 and 5 are the divalent metal halide AX2 evaporation sources. Figure 2 It is the evaporation schematic diagram of the perovskite film prepared by the present application; wherein, 1 is the conductive substrate for depositing the hole transport layer; 3 is the CsI evaporation source, and 4 is the PbI2 evaporation source. Figure 3 It is the top view of the evaporation chamber for preparing the perovskite film of the present application; wherein, 1 is the conductive substrate for depositing the hole transport layer, 2 is the divalent metal halide AX2 evaporation source; 3 is the CsI evaporation source, 4 is the PbI2 evaporation source, and 5 is the divalent metal halide AX2 evaporation source. Figure 4 It is the device structure schematic diagram of the perovskite solar cell of the present application; wherein, 102 is the transparent conductive electrode substrate, 104 is the hole transport layer, 106 is the perovskite absorption layer, 108 is the gaseous inorganic passivation layer, 110 is the electron transport layer, and 112 is the metal electrode layer. Figure 5 The voltage-current density test results of the perovskite solar cell of Example 8. Figure 6 It is the wavelength-fluorescence intensity test results of the perovskite solar cells of Example 8 and Comparative Example 4. Figure 7 It is the stability test results of the perovskite film obtained in Example 1. Detailed Description of the Invention

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Organic passivators usually rely on weak van der Waals forces or hydrogen bonds to bind to the surface of perovskite films, and are easily damaged by environmental factors such as light, heat, and humidity, resulting in the degradation of the passivation effect; the formed organic passivation layer is prone to volatilization or decomposition at high temperatures; and there are often micropores and hygroscopicity, and it is prone to failure when exposed to a humid and hot environment for a long time. How to overcome the defects of organic passivators is the primary problem in solving perovskite films.

[0020] Based on this, this application was created.

[0021] This application provides a perovskite film based on a gas-phase inorganic passivator, including a perovskite layer and a divalent metal halide passivation layer deposited on the perovskite layer by vapor deposition.

[0022] The divalent metal halide of this application forms a stable coordination with the lead vacancies or halogen vacancies on the surface of perovskite through its high charge density and strong chemical bonds (such as ionic bonds and covalent bonds), and can preferentially occupy the deep energy level trap sites to reduce non-radiative recombination losses; at the same time, it reduces the interface barrier through energy band regulation, making the energy levels of the perovskite layer and the electron transport layer (ETL) more matched, and improving the carrier extraction efficiency; the formed inorganic passivation layer is continuous and dense, which can physically isolate the penetration of water and oxygen; it has a stable structure at high temperatures, is not prone to volatilization or decomposition, and the passivation effect is stable for a long time, effectively improving the surface defects of the perovskite film and enhancing the film quality, thus significantly improving the photoelectric conversion efficiency and stability of solar cells.

[0023] In some embodiments, the chemical formula of the divalent metal halide is AX2; wherein, A is a divalent metal cation, selected from the metal elements Be, Mg, Ca, Sr, Ba, Zn, Cd, Sn, Pb; X is an anion, selected from the halogen elements F, Cl, Br, I. The divalent metal halide includes but is not limited to barium iodide (BaI2), magnesium fluoride (MgF2), calcium fluoride (CaF2), barium bromide (BaBr2), lead iodide (PbI2), zinc iodide (ZnI2).

[0024] In some embodiments, the thickness of the divalent metal halide passivation layer is 1-100 Å.

[0025] In this embodiment, the thickness of the divalent metal halide passivation layer within the limited range is beneficial to improving the passivation effect and further enhancing the optoelectronic properties of the perovskite film.

[0026] As Figures 1-3 shown, this application provides a method for preparing a perovskite film, including the following steps: S1. Obtain a perovskite layer; S2. Using the divalent metal halide as an evaporation source and the annealed perovskite layer as a substrate, perform vacuum thermal evaporation passivation to obtain the perovskite film based on the gas-phase inorganic passivator.

[0027] Under vacuum conditions, this application uses thermal evaporation to passivate perovskite thin films with gaseous inorganic substances. The gaseous inorganic substance is a divalent metal halide. By controlling the substrate temperature, substrate rotation speed, evaporation rate of the divalent metal halide evaporation source, and film deposition thickness of the gaseous inorganic substance passivation layer during the passivation process, the passivation layer can better reduce perovskite interface defects and improve interface stability. The preparation method of this application does not require the participation of toxic solvents, is green and environmentally friendly. There are few environmental impurities in a high-vacuum environment, and the self-purification effect during evaporation can be utilized to avoid introducing other impurities, which is beneficial to the passivation of humidity-sensitive perovskite materials. The process is stable and has good repeatability. The passivation is uniform, the thickness is precisely controllable, effectively reducing the surface defects of the perovskite thin film and significantly improving the photoelectric conversion efficiency and stability of the solar cell.

[0028] In some embodiments, the vacuum thermal evaporation methods include single-source inorganic substance evaporation passivation, multi-source inorganic substance co-evaporation passivation, and multi-source inorganic substance layer-by-layer alternating evaporation passivation.

[0029] In some embodiments, the method for obtaining the perovskite layer includes two-source co-evaporation and three-source co-evaporation. The evaporation sources for the two-source co-evaporation are cesium iodide and lead iodide; the evaporation sources for the three-source co-evaporation are cesium iodide, lead iodide, and organic ammonium salt.

[0030] In some embodiments, the temperature of the substrate is 20 - 80 °C, and the rotation speed of the substrate is 2 - 15 rpm.

[0031] In this embodiment, the temperature of the substrate within the defined range is beneficial to controlling the formation of a dense and stable passivation layer.

[0032] In some embodiments, the annealing temperature is 50 - 100 °C, and the annealing time is 5 - 15 min.

[0033] This application provides a perovskite solar cell comprising a perovskite thin film based on a gaseous inorganic substance passivator.

[0034] As Figure 4 shown, to prepare an inorganic perovskite thin film and the corresponding solar cell, ITO conductive glass or FTO conductive glass can be used as the transparent conductive electrode, and a hole transport layer, such as nickel oxide (NiO x), Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) (PEDOT:PSS), [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz). Subsequently, using the transparent conductive glass deposited with the hole transport layer as the substrate, an inorganic perovskite absorption layer is prepared by vacuum multi-source co-evaporation method or solution method, and then a divalent metal halide passivation layer and an electron transport layer (C 60 / BCP) and a metal electrode layer, such as silver (Ag), gold (Au) or copper (Cu), are prepared by vacuum thermal evaporation process to complete the preparation of the perovskite solar cell. Specifically, the steps are as follows: The transparent conductive electrode substrate is pre-cleaned and dried, and a hole transport layer is prepared on the transparent conductive electrode substrate by magnetron sputtering process or solution spin-coating method. The hole transport layer is selected from NiO x , PTAA, PEDOT:PSS, Me-4PACz; A perovskite layer is prepared on the hole transport layer by vacuum thermal evaporation process or spin-coating process, and then annealed; A passivation layer is prepared on the annealed perovskite layer: passivation is carried out using gaseous inorganic substances under vacuum conditions. The passivation methods include single-source inorganic substance evaporation passivation, multi-source inorganic substance co-evaporation passivation, and multi-source inorganic substance layer-by-layer alternating evaporation passivation. The gaseous inorganic substance is a divalent metal halide AX2, where A is a divalent metal cation, selected from metal elements Be, Mg, Ca, Sr, Ba, Zn, Cd, Sn, Pb; X is an anion, selected from halogen elements F, Cl, Br, I; control the substrate temperature, substrate rotation speed, evaporation rate of the divalent metal halide evaporation source, and film deposition thickness of the gaseous inorganic substance passivation layer during the passivation process, so that the passivation layer can better reduce the perovskite interface defects and improve the interface stability; An electron transport layer is prepared on the passivation layer by vacuum thermal evaporation process. The electron transport layer is C 60 / BCP; A metal electrode layer is prepared on the electron transport layer by vacuum thermal evaporation process. The metal electrode layer is selected from Au, Ag or Cu.

[0035] The following further illustrates this solution through specific examples.

[0036] Example 1 A preparation method of a perovskite thin film based on a gaseous inorganic substance passivator includes the following steps: S1. Transfer the ITO substrate spin-coated with PTAA into the vacuum chamber, and evacuate to 3×10 -4Below Pa and preheat the substrate to 40 °C; by adjusting the current value applied to both ends of the evaporation source, adjust the evaporation rates of CsI and PbI2 to 0.96 Å / s and 0.75 Å / s respectively. After the rates are stable, open the substrate baffle to start evaporation; until the total thickness shown by the CsI and PbI2 evaporation sources is 300 nm, close the substrate baffle to end the evaporation of the perovskite layer and obtain the perovskite layer. S2. Take out the perovskite layer, anneal it at 80 °C for 15 min, then put it into the vacuum chamber. Wait until the vacuum is pumped to 3×10 -4 Below Pa, after preheating the substrate to 30 °C, prepare the BaI2 passivation layer by single-source inorganic evaporation passivation process. Adjust the evaporation rate to 0.05 Å / s. After the rate is stable, open the substrate baffle to start evaporation; until the thickness shown by the BaI2 evaporation source is 10 Å, close the substrate baffle to end passivation.

[0037] Example 2-3 A method for preparing a perovskite thin film based on a gaseous inorganic passivator, other contents are the same as in Example 1. The difference is that until the thickness shown by the BaI2 evaporation source is 10 Å, it is adjusted to 1 Å and 30 Å in turn.

[0038] Example 4 A method for preparing a perovskite thin film based on a gaseous inorganic passivator, other contents are the same as in Example 1. The difference is that BaI2 is replaced by ZnI2.

[0039] Example 5 A method for preparing a perovskite thin film based on a gaseous inorganic passivator, other contents are the same as in Example 1. The difference is that BaI2 is replaced by BaBr2.

[0040] Example 6 A method for preparing a perovskite thin film based on a gaseous inorganic passivator, other contents are the same as in Example 1. The difference is that in step S2, a BaBr2 and BaI2 co-evaporation passivation layer is prepared by a multi-source inorganic co-evaporation passivation process: adjust the evaporation rates of the two sources to 0.05 Å / s respectively. After the rates are stable, open the substrate baffle to start evaporation; until the total thickness shown by the two evaporation sources is 10 Å, close the substrate baffle to end passivation.

[0041] Example 7 A method for preparing a perovskite thin film based on a gas-phase inorganic passivator, the other contents are the same as those in Example 1. The difference is that in step S2, a BaBr2 and PbI2 layer-by-layer alternating evaporation passivation process is used to prepare a BaBr2 and PbI2 layer-by-layer alternating evaporation passivation layer: the evaporation rates of the two sources are respectively adjusted to 0.05 Å / s. After the rates are stable, the PbI2 source baffle is closed, the substrate baffle is opened, and BaBr2 is evaporated. After 2 Å, the BaBr2 source baffle is closed and the PbI2 source baffle is opened; 2 Å of PbI2 is evaporated, and the evaporation is alternately carried out until the total thickness reaches 10 Å, and then the substrate baffle is closed to end the passivation.

[0042] Examples 8-14 A perovskite solar cell is prepared as follows: Prepare a transparent ITO conductive electrode substrate, soak it successively in diluted conductive glass cleaning agent, deionized water, ethanol, acetone, and ethanol for ultrasonic treatment for 10 minutes each time, then dry it with a nitrogen gun, and then place it in an oven and dry it for 1 hour for standby. The dried ITO glass is treated with oxygen plasma for 10 minutes; a 4 mg / mL PTAA chlorobenzene solution is prepared, and the spin coating speed and time are 4000 rpm / 30 s. After spin coating, annealing is carried out at a temperature of 100°C for 10 minutes to obtain an ITO substrate spin-coated with PTAA; The perovskite thin films of Examples 1-7 are successively prepared on the ITO substrate spin-coated with PTAA; Then, C 60 and BCP are successively deposited on the passivation layer of the perovskite thin film by vacuum thermal evaporation process. Among them, the evaporation rate of C 60 is 0.3 Å / s and the thickness is 20 nm; the evaporation rate of BCP is 0.2 Å / s and the thickness is 3 nm; silver is evaporated on the electron transport layer as a metal electrode layer, and the evaporation rate is 0.3 Å / s and the thickness is 100 nm, thus obtaining the perovskite solar cell.

[0043] Comparative Example 1 A method for preparing a perovskite thin film based on a gas-phase inorganic passivator, the other contents are the same as those in Example 1. The difference is that the step of preparing the BaI2 passivation layer is not included.

[0044] Comparative Example 2 A method for preparing a perovskite thin film based on a gas-phase inorganic passivator, the other contents are the same as those in Example 1. The difference is that the BaI2 passivation layer is replaced with a PEAI organic passivation layer.

[0045] Comparative Example 3 A perovskite solar cell, the other contents are the same as those in Example 8. The difference is that the perovskite thin film in Example 1 is replaced with a perovskite thin film that has been placed in a nitrogen environment for 1 month.

[0046] Comparative Examples 4 - 5 A perovskite solar cell, with other contents being the same as those in Example 8, except that the perovskite thin film in Example 1 was successively replaced with the perovskite thin films in Comparative Examples 1 - 2.

[0047] Testing and Evaluation The performance of the perovskite solar cells in Examples 8 - 14 and Comparative Examples 3 - 5 was tested, and the results are shown in Table 1.

[0048] Table 1 Performance Test Results of Different Perovskite Solar Cells

[0049] As can be seen from the above results, in the examples of the present application, divalent metal halides were used for gas - phase inorganic passivation. By controlling the substrate temperature, substrate rotation speed, evaporation rate of the divalent metal halide evaporation source, film deposition thickness of the gas - phase inorganic passivation layer, annealing time and temperature after passivation, the passivation layer can better reduce the perovskite interface defects, improve the interface stability, and thus significantly improve the photoelectric conversion efficiency and stability of the solar cell.

[0050] The voltage - current density of the perovskite solar cell in Example 8 was tested, and the results are as Figure 5 shown; the wavelength - fluorescence intensity of the perovskite solar cells in Example 8 and Comparative Example 4 was tested, and the results are as Figure 6 shown. It shows that the perovskite solar cell prepared by passivation in the present application has good electrochemical performance.

[0051] The perovskite thin film obtained in Example 1 was placed in a nitrogen box for 1 month, and the results are as Figure 7 shown, Figure 7 a is before being placed in the nitrogen box, Figure 7 b is after being placed in the nitrogen box, indicating that the black phase can be stably maintained for one month, and the perovskite thin film has strong stability.

[0052] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A perovskite thin film based on a gas-phase inorganic passivator, characterized in that, It includes a perovskite layer and a divalent metal halide passivation layer deposited by vapor deposition on the perovskite layer.

2. The perovskite thin film based on the gas-phase inorganic passivator according to claim 1, characterized in that, The chemical formula of the divalent metal halide is AX2; wherein, A is a divalent metal cation selected from the metal elements beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb); X is an anion selected from the halogen elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I).

3. The perovskite film based on the gas-phase inorganic passivator according to claim 1, wherein The thickness of the divalent metal halide passivation layer is 1 - 100 Å.

4. A method for preparing a perovskite thin film based on a gas-phase inorganic passivator as described in any one of claims 1-3, characterized in that, It includes the following steps: Obtain a perovskite layer; Using the divalent metal halide as an evaporation source and the annealed perovskite layer as a substrate, perform vacuum thermal evaporation passivation to obtain the perovskite thin film based on the vapor-phase inorganic passivator.

5. The preparation method according to claim 4, characterized in that, The ways of the vacuum thermal evaporation passivation include single-source inorganic evaporation passivation, multi-source inorganic co-evaporation passivation, and multi-source inorganic layer-by-layer alternating evaporation passivation.

6. The preparation method according to claim 4, wherein The method for obtaining the perovskite layer includes one of two-source co-evaporation, three-source co-evaporation, and solution method.

7. The preparation method according to claim 6, characterized in that, The evaporation sources in the two-source co-evaporation are cesium iodide (CsI) and lead iodide (PbI2); the evaporation sources in the three-source co-evaporation are cesium iodide (CsI), lead iodide (PbI2), and organic ammonium salt.

8. The preparation method according to claim 4, characterized in that, The temperature of the substrate is 20 - 80 °C, and the rotation speed of the substrate is 2 - 15 rpm.

9. The preparation method according to claim 4, characterized in that The temperature of the annealing is 50 - 100 °C, and the annealing time is 5 - 15 min.

10. A perovskite solar cell comprising the perovskite thin film based on the vapor-phase inorganic passivator according to any one of claims 1 - 3.

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