Carbazolyl micromolecule doped perovskite active layer and preparation method and application thereof

Abstract

The invention discloses a carbazolyl micromolecule doped perovskite active layer and a preparation method and application thereof, and the preparation method comprises the steps: dissolving formamidine iodide, cesium iodide, lead iodide and methylamine iodide in an organic solvent to obtain a cesium-formamidine-methylamine lead-iodine alloy perovskite precursor solution with an ABX3 configuration; the preparation method comprises the following steps: doping a carbazolyl micromolecule dopant into a perovskite precursor solution, and preparing the perovskite active layer doped with carbazolyl micromolecules from the precursor solution in any one mode of spin coating, blade coating or spray coating. By introducing carbazolyl small molecules, the energy level of perovskite is effectively adjusted, the crystallinity of the perovskite thin film is improved, the hole transport layer-free p-i-n type perovskite solar cell is prepared, the photoelectric conversion efficiency of the cell device prepared by the method exceeds 26.6%, and the cell device shows excellent long-term operation stability.

Description

Technical Field

[0001] The present invention relates to the field of perovskite solar cells, and in particular to a perovskite active layer doped with a carbazole-based small molecule, and a preparation method and application thereof. Background Art

[0002] With the increasing global demand for renewable energy and the growing awareness of environmental protection, the future development prospects of solar cells are very broad. Solar cells are energy-saving devices that use solar radiation to directly convert into electrical energy. They have the advantages of high energy utilization efficiency, low maintenance cost, and high power stability. They are a greener and more sustainable power generation technology.

[0003] Perovskite solar cells have been considered as one of the most promising photovoltaic technologies. They have the advantages of solution preparation, low cost, high efficiency, flexible preparation, and semi-transparency. They have developed rapidly in the past decade. Among them, pin-type perovskite solar cells have attracted widespread attention due to their simple manufacturing process, potential application in flexible devices, and good compatibility with tandem devices. At present, the power conversion efficiency of single-junction pin-type devices has reached 27%. However, traditional pin-type perovskite solar cells adopt a classic multilayer heterostructure. This structure usually includes a perovskite light-absorbing layer sandwiched between a p-type carrier transport layer (HTL) and an n-type electron transport layer (ETL). Although this structure has been successful to a certain extent, it also has some limitations. First, the deposition process of the multilayer structure is time-consuming and energy-consuming, which increases the manufacturing cost. Second, common organic hole transport layers (such as PEDOT:PSS and PTAA) are prone to light, heat, and moisture-induced degradation; inorganic hole transport layers (such as nickel oxide) react with perovskites, resulting in interface decomposition. In addition, most HTLs are expensive and complex to synthesize. The combined effect of these factors has limited the widespread application and commercial development of pin-type perovskite solar cells. Therefore, molecular doping of perovskites to prepare devices without a hole transport layer is a more effective strategy. However, the performance of pin-type perovskite solar cells without a hole transport layer is currently lower than that of perovskite solar cells with a hole transport layer. This is because the strategy without a hole transport layer is prone to energy level matching problems between the perovskite and the electrode, which is mainly attributed to the difference in conductivity between the perovskite and the transport layer. It is difficult to regulate the conductive behavior of the perovskite so that it has a carrier extraction ability comparable to that of the transport layer, resulting in lower performance of pin-type perovskite solar cells without a hole transport layer.

[0004] Therefore, for PIN-type perovskite solar cells without a hole transport layer, it is an important research direction to solve the efficiency problem by regulating the band structure of the perovskite through molecular dopants to make it more matched with the energy level of the electrode, and improving the conductive behavior of the perovskite so that it has a carrier injection ability comparable to that of the transport layer. Summary of the invention

[0005] Based on this, the present invention provides a perovskite active layer doped with a carbazole small molecule and a preparation method and application thereof, so as to solve the problem that the prior art PIN-type perovskite solar cell without a hole transport layer is difficult to effectively regulate the band structure of the perovskite, resulting in an energy level mismatch between the active layer and the electrode, and further resulting in poor performance of the PIN-type perovskite solar cell without a hole transport layer.

[0006] To achieve the above object, the present invention provides a method for preparing a perovskite active layer doped with a carbazole-based small molecule, which comprises the following steps:

[0007] (1) dissolving iodoformamidine, iodomethylamine, cesium iodide and lead iodide in an organic solvent, shaking and dissolving, to obtain a perovskite precursor solution;

[0008] (2) Adding a carbazole-based small molecule dopant to the perovskite precursor solution of step (1) to prepare a precursor solution doped with a carbazole-based small molecule, wherein the carbazole-based small molecule dopant is selected from the following structures:

[0009]

[0010] Wherein, B is an alkyl group, a benzene ring or a biphenyl group; A is a phosphoric acid group, a carboxylic acid group or a boric acid group;

[0011] (3) The precursor solution doped with carbazole-based small molecules in step (2) is coated with a film-forming process to prepare a cesium-formamidine-methylamine-lead-iodine alloy perovskite film having an ABX3 configuration, i.e., a perovskite active layer doped with carbazole-based small molecules; in the ABX3 configuration, the A position is a mixture of methylamine ions, formamidine ions, and cesium ions, the B position is a lead ion, and the X position is an iodide ion.

[0012] As a further preferred technical solution of the present invention, the carbazole-based small molecule dopant is selected from one of the following structures:

[0013] .

[0014] As a further preferred technical solution of the present invention, the concentration of the carbazole-based small molecule dopant in the perovskite precursor solution is 0.05-15 mg / mL.

[0015] As a further preferred technical solution of the present invention, the organic solvent is selected from one or a mixture of DMF, DMSO, and NMP.

[0016] As a further preferred technical solution of the present invention, in step (3), the substrate used for coating the precursor solution doped with carbazole-based small molecules is ITO conductive glass or FTO conductive glass.

[0017] As a further preferred technical solution of the present invention, the thickness of the cesium-formamidine-methylamine lead iodine alloy perovskite film with ABX3 configuration prepared in step (3) is 450-850 nm.

[0018] As a further preferred technical solution of the present invention, in step (3), the precursor solution doped with carbazole small molecules is coated by any method such as spin coating, scraping or spraying, and then annealed at 90-150°C.

[0019] According to another aspect of the present invention, the present invention also provides a perovskite active layer doped with a carbazole-based small molecule.

[0020] According to another aspect of the present invention, the present invention also provides an application of a carbazole-based small molecule doped perovskite active layer as a perovskite active layer in a pin-type perovskite solar cell. The pin-type perovskite solar cell comprises a conductive glass, a carbazole-based small molecule doped perovskite active layer, an interface passivation layer, an electron transport layer and a metal electrode arranged in sequence.

[0021] Compared with the prior art, the present invention introduces carbazole-based small molecules by adding dopants, effectively regulates the energy band structure of perovskite, improves the conductive behavior of perovskite, and obtains a perovskite active layer doped with carbazole-based small molecules having a carrier injection ability comparable to that of a transport layer and high crystallinity; moreover, a PIN-type perovskite solar cell using the perovskite active layer doped with the carbazole-based small molecules greatly improves the open circuit voltage and photoelectric conversion efficiency of the device, and obtains excellent long-term operating stability.

[0022] The raw materials used in the carbazole-based small molecule doped perovskite active layer and the hole transport layer-free pin-type perovskite solar cell prepared by the present invention are low-priced and easy to obtain, and the method simplifies the device structure, has a simpler manufacturing process, and greatly reduces the production cost. In addition, the method is compatible with the preparation of large-area devices, flexible and stacked devices, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1It is a schematic flow chart of the method for preparing a perovskite film in a specific embodiment of the present invention, wherein: 1 is dripping a perovskite precursor solution containing a dopant onto an ITO substrate; 2 is depositing a perovskite film using a spin coating process; 3 is dripping an anti-solvent; and 4 is an annealing process.

[0025] Figure 2 Schematic diagram of the structure of a pin-type perovskite solar cell, where: 1 is the substrate; 2 is the perovskite active layer; 3 is the interface passivation layer; 4 is the electron transport layer; and 5 is the metal electrode.

[0026] Figure 3 1 is the XRD diagram of the perovskite film before and after doping with the dopant in Example 1.

[0027] Figure 4 This is a SEM image of the upper surface of the perovskite film before and after doping with the dopant in Example 1.

[0028] Figure 5 This is a steady-state fluorescence spectrum (PL) diagram of the perovskite film before and after doping with the dopant in Example 1.

[0029] Figure 6 This is a time-resolved fluorescence spectrum (TRPL) diagram of the perovskite film before and after doping with the dopant in Example 1.

[0030] Figure 7 The current-voltage characteristic curves of the perovskite solar cells prepared in the control example and examples 1, 2, 3 and 4.

[0031] Figure 8 This is the long-term stability curve of the PIN-type perovskite solar cell without a hole transport layer in Example 1.

[0032] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0034] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0035] At present, pin-type perovskite solar cells without a hole transport layer have huge open-circuit voltage losses at the buried interface due to the mismatch between the band structure of the perovskite active layer and the energy level of the electrode, which seriously affects the performance and stability of pin-type perovskite solar cells without a hole transport layer.

[0036] In view of the above-mentioned existing problems, the present invention adds a dopant to the precursor solution, adjusts the energy level structure of the perovskite to achieve the best energy level matching with the electrode, improves the carrier extraction ability of the perovskite, thereby reducing the energy level mismatch of the buried interface and increasing the open circuit voltage of the device. In addition, the introduction of carbazole-based small molecules effectively improves the crystallinity of the perovskite film, is conducive to the formation of large-sized grains, reduces the bulk phase grain boundaries of the perovskite film, thereby reducing the carrier transport loss of the buried interface, and further improves the photoelectric conversion efficiency of the pin-type perovskite solar cell.

[0037] The precursor solution of the present invention is prepared by dissolving iodoformamidine, iodomethylamine, cesium iodide and lead iodide in a mixed solution of an organic solvent, introducing 0.05-15 mg / mL of a carbazole-based small molecule as a dopant, and dissolving by shaking. Afterwards, the precursor solution is prepared by any one of spin coating, scraping or spraying to obtain a perovskite active layer doped with a carbazole-based small molecule having an ABX3 configuration.

[0038] The prepared carbazole-based small molecule doped perovskite active layer is applied to a pin-type perovskite solar cell, and the thickness of the perovskite active layer is generally 450-850 nm, preferably 750 nm. Figure 2 As shown, the pin-type perovskite solar cell includes a conductive glass 1, a perovskite active layer 2 doped with carbazole small molecules, an interface passivation layer 3, an electron transport layer 4 and a metal electrode 5.

[0039] The present invention effectively regulates the energy band structure of the perovskite active layer by introducing carbazole-based small molecules as dopants in the precursor solution, achieves the optimal energy level alignment between the perovskite active layer and the electrode, and further prepares a pin-type perovskite solar cell device with high photoelectric conversion efficiency. The packaged device obtains better operating stability under the conditions of humidity of 55-75% and 65°C.

[0040] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments.

[0041] Comparative Example:

[0042] The pin-type perovskite solar cell prepared based on the undoped perovskite active layer has the following specific steps:

[0043] 1. Conductive glass cleaning:

[0044] The transparent conductive glass ITO was cleaned with detergent, deionized water and ethanol ultrasonically for 45 minutes each, twice; oxygen plasma cleaning was used before use to remove surface organic matter and increase the concentration of hydroxyl groups on the ITO surface.

[0045] 2. Preparation of perovskite layer:

[0046] Combination Figure 1 As shown, 247.7 mg iodoformamide (FAI), 20.8 mg cesium iodide (CsI), 737.6 mg lead iodide (PbI2), 12.7 mg iodomethylamine (MAI), 5.4 mg chloromethylamine (MACl) and 22.3 mg lead chloride (PbCl2) were dissolved in a mixed solvent of 200 μL DMSO and 800 μL DMF, and the mixture was shaken and dissolved for 3 hours to obtain a perovskite precursor solution. 40 μL of the prepared precursor solution was added dropwise on an ITO conductive glass substrate, and a perovskite film was deposited by spin coating. The spin coating procedure was to accelerate at 2000 rpm, accelerate to 4000 rpm, and spin coat for 30 s. In the penultimate 5 s of the procedure, 160 μL of chlorobenzene was added as an anti-solvent, and then annealed by heating at 110 °C on a hot stage for 30 min.

[0047] 3.Interface passivation layer deposition:

[0048] After the perovskite film is deposited, a bimolecular ammonium salt passivation layer is coated. The specific operation is to dissolve 12 mM 3-(methylthio)propylamine hydroiodide (3MTPAI) and 6 mM propane-1,3-diammonium iodide (PDAI2) in a mixed solvent of isopropanol / chlorobenzene with a volume ratio of 1:1, and the acceleration is 4500 rpm, and the spin coating is performed at 4500 rpm for 25 s.

[0049] 4. Electron transport layer deposition:

[0050] 30 nm of C was deposited in sequence by vacuum evaporation. 60 and 5 nm BCP. The vacuum degree during evaporation is less than 7×10 -4 Pa, the evaporation rate is 0.1~0.5 angstroms / second.

[0051] 5. Metal electrode deposition:

[0052] After the electron transport layer is deposited, the same process is used to evaporate 100 nm thick silver to complete the preparation of the pin-type perovskite solar cell device.

[0053] Performance and stability test:

[0054] The circular hole area is 0.074 cm 2 The 0.1 mm thick iron sheet was used as a light shielding template, and the current-voltage characteristic curve of the pin-type perovskite solar cell device was tested under AM 1.5 G illumination. The results are shown in Figure 7 The stability test was conducted in an environmental chamber with 60% humidity and 65°C. The results are shown in Figure 8 shown.

[0055] Embodiment 1

[0056] The pin-type perovskite solar cell prepared based on the perovskite active layer doped with the carbazole-based small molecule PBA has the following specific steps:

[0057] 1. Substrate cleaning: same as the control example;

[0058] 2. Preparation of perovskite layer: 247.7 mg iodoformamide (FAI), 20.8 mg cesium iodide (CsI), 737.6 mg lead iodide (PbI2), 12.7 mg iodomethylamine (MAI), 5.4 mg chloromethylamine (MACl) and 22.3 mg lead chloride (PbCl2) were dissolved in a mixed solvent of 200 μL DMSO and 800 μL DMF, and the mixture was shaken and dissolved for 3 hours. Then 5 mg / mL of carbazole-based small molecule PBA was doped into the above solution, and the mixture was shaken and dissolved for 3 hours to obtain a perovskite precursor solution. 40 μL of the prepared precursor solution was added dropwise to the ITO conductive glass substrate, and the perovskite film was deposited by spin coating. The spin coating procedure was as follows: acceleration 2000 rpm, accelerated to 4000 rpm and spin coating for 30 s, 160 μL of chlorobenzene was added as anti-solvent in the penultimate 5 s of the procedure, and then annealed by heating at 110 °C on a hot stage for 30 min.

[0059] 3. Interface passivation layer deposition: same as the control example;

[0060] 4. Electron transport layer deposition: same as the control example;

[0061] 5. Metal electrode deposition: same as the control example;

[0062] Performance and stability test:

[0063] The same test method as the control example was adopted, and the current-voltage characteristic test results were as follows: Figure 7 As shown in FIG. 1 , it can be seen that the performance of Example 1 is significantly improved by 25.7% compared with the control example. At the same time, the stability test results of the device are shown in FIG. Figure 8As shown in the figure, the long-term stability of the device is significantly improved. After 2000 hours of aging test, the device efficiency retains more than 95% of the original. By adding dopants to the precursor solution, the optimal energy level matching between perovskite and electrode is achieved, the carrier extraction ability of perovskite is improved, and the open circuit voltage of the device is increased. At the same time, the introduction of carbazole-based small molecules effectively improves the crystallinity of perovskite film and reduces the carrier transport loss at the buried interface, thereby significantly improving the device performance and long-term operation stability.

[0064] The perovskite active layer before and after doping with carbazole-based small molecule dopants was characterized and analyzed by X-ray diffraction (XRD), such as Figure 3 Compared with undoped perovskite, PBA-doped perovskite has a narrower half-peak width and higher diffraction peak intensity, and the lead iodide signal is weakened, indicating that the quality of perovskite crystals is significantly improved after molecular doping.

[0065] The perovskite active layer before and after doping with carbazole-based small molecule dopants was characterized and analyzed by scanning electron microscopy (SEM). Figure 2 and Figure 4 The top surface and cross-sectional SEM images of the perovskite film show that the grain size increases after molecular doping, and the grain boundaries are significantly reduced in the vertical orientation.

[0066] The above perovskite film was characterized and analyzed by steady-state fluorescence spectroscopy (PL) and time-resolved fluorescence spectroscopy (TRPL), such as Figure 5 and Figure 6 The PL peak intensity and lifetime of the perovskite film doped with carbazole-based small molecule dopants are significantly enhanced, indicating that non-radiative recombination is reduced and the perovskite bulk and interface defects are effectively passivated.

[0067] Embodiment 2

[0068] 1. Substrate cleaning: same as the control example;

[0069] 2. Electron transport layer deposition: same as the control example;

[0070] 3. Preparation of perovskite layer: The specific preparation method is as described in Example 1, except that the carbazole-based small molecule dopant used in this example is Cz-PBA;

[0071] 4. Passivation layer deposition: same as the control example;

[0072] 5. Preparation of hole transport layer: same as in the control example;

[0073] 6. Metal electrode deposition: same as the control example;

[0074] The same test method as the control example was adopted, and the current-voltage characteristic test results were as follows: Figure 7 As shown in Figure 2, under AM1.5G simulated sunlight, the short-circuit current of the device during reverse scanning is 26.44 mA cm -2 , the open circuit voltage is 1.188V, the fill factor is 83.2%, and the photoelectric conversion efficiency is 26.0%.

[0075] Embodiment 3

[0076] 1. Substrate cleaning: same as the control example;

[0077] 2. Electron transport layer deposition: same as the control example;

[0078] 3. Preparation of perovskite layer: The specific preparation method is as described in Example 1, except that the carbazole-based small molecule dopant used in this example is BCz-PBA;

[0079] 4. Passivation layer deposition: same as the control example;

[0080] 5. Preparation of hole transport layer: same as in the control example;

[0081] 6. Metal electrode deposition: same as the control example;

[0082] The same test method as the control example was adopted, and the performance test results were as follows: Figure 7 As shown, it can be seen that the photoelectric performance of Example 3 is better than that of the control example, and its photoelectric conversion efficiency reaches 26.6%.

[0083] Embodiment 4:

[0084] 1. Substrate cleaning: same as the control example;

[0085] 2. Electron transport layer deposition: same as the control example;

[0086] 3. Preparation of perovskite layer: The specific preparation method is as described in Example 1, except that the carbazole-based small molecule dopant used in this example is N-ethylcarbazole;

[0087] 4. Passivation layer deposition: same as the control example;

[0088] 5. Preparation of hole transport layer: same as in the control example;

[0089] 6. Metal electrode deposition: same as the control example;

[0090] The same test method as the control example was adopted, and the performance test results were as follows: Figure 7As shown, it can be seen that the photoelectric performance of Example 4 is significantly lower than that of the control example, and its photoelectric conversion efficiency is only 20.2%. In addition, a large number of experiments were conducted by replacing the type of carbazole-based small molecule dopant, and it was found by comparison that only the carbazole-based small molecule with the following structure of the present invention has excellent photoelectric performance and operation stability. The structure of the carbazole-based small molecule is as follows:

[0091]

[0092] Wherein, B is an alkyl group, a benzene ring or a biphenyl group; A is a phosphoric acid group, a carboxylic acid group or a boric acid group.

[0093] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a perovskite active layer doped with a carbazole-based small molecule, characterized in that: The following steps are involved: (1) dissolving iodoformamidine, iodomethylamine, cesium iodide and lead iodide in an organic solvent, and shaking to dissolve, thereby obtaining a perovskite precursor solution; (2) Adding a carbazole-based small molecule dopant to the perovskite precursor solution of step (1) to prepare a precursor solution doped with a carbazole-based small molecule, wherein the carbazole-based small molecule dopant is selected from the following structures: ； Wherein, B is an alkyl group, a benzene ring or a biphenyl group; A is a phosphoric acid group, a carboxylic acid group or a boric acid group; (3) The precursor solution doped with carbazole-based small molecules in step (2) is subjected to a coating process to prepare a cesium-formamidine-methylamine-based lead-iodine alloy perovskite film having an ABX3 configuration, i.e., a perovskite active layer doped with carbazole-based small molecules; in the ABX3 configuration, the A position is a mixture of methylamine ions, formamidine ions, and cesium ions, the B position is a lead ion, and the X position is an iodine ion.

2. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: The carbazole-based small molecule dopant is selected from one of the following structures: 。 3. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: The concentration of the carbazole-based small molecule dopant in the perovskite precursor solution is 0.05-15 mg / mL.

4. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: The organic solvent is selected from one or a mixture of DMF, DMSO and NMP.

5. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: In step (3), the substrate used for coating the precursor solution doped with carbazole small molecules is ITO conductive glass or FTO conductive glass.

6. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: The thickness of the cesium-formamidine-methylamine lead iodine alloy perovskite film with ABX3 configuration prepared in step (3) is 450-850nm.

7. The method for preparing a carbazole-based small molecule doped perovskite active layer according to claim 1, characterized in that: In step (3), the precursor solution doped with carbazole small molecules is coated by spin coating, scraping coating or spraying, and then annealed at 90-150°C.

8. A carbazole-based small molecule doped perovskite active layer, characterized in that: The method is prepared by any one of claims 1 to 7.

9. Use of the carbazole-based small molecule doped perovskite active layer according to claim 8 as a perovskite active layer in a pin-type perovskite solar cell.

10. A pin-type perovskite solar cell, characterized in that: The pin-type perovskite solar cell comprises conductive glass, an interface passivation layer, an electron transport layer, a metal electrode, and the carbazole-based small molecule doped perovskite active layer according to claim 8.

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