Broadband-gap perovskite thin film and preparation method and application thereof

Abstract

The invention discloses a wide-band-gap perovskite thin film and a preparation method and application thereof. The preparation method comprises the following steps: dissolving powder containing isonicotinic acid groups in an FA0. 8Cs0. 2Pb (I0. 6Br0. 4) 3 precursor solution to obtain a wide-band-gap perovskite precursor solution with the doping concentration of 0.5-1.5 mol%; the wide-band-gap perovskite thin film is obtained by performing two-step spin coating on the wide-band-gap perovskite precursor solution on a substrate and then performing two-step annealing, and when the wide-band-gap perovskite thin film is applied to a wide-band-gap perovskite solar cell or a laminated wide-band-gap perovskite solar cell, the stability and the performance of a device can be improved. The method mainly comprises the steps of enhancing interface connection, improving film uniformity, reducing non-radiative recombination, prolonging the service life of current carriers, improving filling factors and current density and improving photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of wide-bandgap perovskite solar cells, and particularly relates to a wide-bandgap perovskite thin film, a preparation method thereof, and an application thereof. Background Art

[0002] At present, the power conversion efficiency of all-perovskite tandem solar cells has exceeded that of single-junction perovskite solar cells. To further improve the efficiency, it is crucial to fabricate highly efficient and stable wide-bandgap perovskite solar cells (WBGPSCs). However, as the top cell of tandem solar cells (TSCs), wide-bandgap perovskite solar cells (PSCs) suffer from severe interfacial charge transport losses, which greatly hinder the development of TSCs. Therefore, finding an effective strategy to minimize the interfacial losses of WBGPSCs is of great significance for the development of highly efficient tandem devices.

[0003] Since PSCs are structural devices composed of a perovskite light-absorbing layer, charge transport layers, and electrodes, the multi-layer stacked structure implies various interfacial contacts. The properties of these interfaces directly affect charge transport, which is crucial for high-performance PSCs.

[0004] On the one hand, interfacial non-radiative recombination and mismatched energy levels lead to severe charge transport losses, thus limiting the efficiency of WBGPSCs. On the other hand, interfacial defects may also damage the stability of the device. Therefore, interface engineering is one of the most effective methods to achieve high-performance and long-term stable perovskite solar cells. For example, a series of fluorine-doped succinic acid derivatives are introduced into the bottom interface of perovskite. Among them, tetrafluorosuccinic acid (TFSA) has a symmetric molecular structure and strong electronegativity, and is proven to be the best interface regulator among the selected functional molecules. It regulates the morphological arrangement of MeO-2PACz, equalizes its surface contact potential, and successfully achieves a power conversion efficiency of 25.92% in an inverted device with an active area of 0.09 cm 2 ².

[0005] Although previous works have pointed out methods for optimizing interfaces, there are still problems such as poor interfacial energy level alignment between perovskite and the electron transport layer (ETL) or hole transport layer (HTL), resulting in non-radiative recombination of photo-generated carriers and reduction of the open-circuit voltage (V OC oc) and fill factor. Moreover, halogen ions (such as iodide ions) are prone to migration under light illumination and thermal stress, leading to an increase in ion vacancies and defect density at the interface, thus affecting the interface stability and device performance. Therefore, further exploring charge transport losses has a huge promoting effect on improving the efficiency of perovskite solar cells. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0007] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0008] Therefore, an object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a wide-bandgap perovskite thin film.

[0009] To solve the above technical problems, the present invention provides the following technical solutions: including,

[0010] Pyridine-based organic acids are dissolved in FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3 precursor solution to obtain a wide-bandgap perovskite precursor solution with a doping concentration of 0.5 - 1.5 mol%;

[0011] The wide-bandgap perovskite precursor solution is spin-coated on a substrate in two steps and then annealed in two steps to obtain a wide-bandgap perovskite thin film.

[0012] As a preferred embodiment of the method for preparing a wide-bandgap perovskite thin film according to the present invention, wherein: the pyridine-based organic acid includes one of 2-chloroisonicotinic acid or isonicotinic acid.

[0013] As a preferred embodiment of the method for preparing a wide-bandgap perovskite thin film according to the present invention, wherein: the rotation speed of the first spin-coating in the two-step spin-coating is 450 - 500 rpm, and the time is 2 - 3 s; the rotation speed of the second spin-coating is 4000 - 5000 rpm, and the time is 60 - 70 s.

[0014] As a preferred embodiment of the method for preparing a wide-bandgap perovskite thin film according to the present invention, wherein: at 22 - 25 s of the second spin-coating, diethyl ether is added dropwise as an antisolvent.

[0015] As a preferred embodiment of the method for preparing a wide-bandgap perovskite thin film according to the present invention, wherein: the dropwise addition amount of diethyl ether compared to the wide-bandgap perovskite precursor solution is 70 - 80:8 - 9 (μL).

[0016] As a preferred embodiment of the method for preparing a wide-bandgap perovskite thin film according to the present invention, wherein: the first annealing in the two-step annealing is at 60 - 65 °C for 2 - 3 min, and the second annealing is at 100 - 105 °C for 8 - 10 min.

[0017] Another object of the present invention is to provide a wide-bandgap perovskite thin film.

[0018] Another object of the present invention is to provide an application of a wide-bandgap perovskite thin film in the preparation of a wide-bandgap perovskite solar cell.

[0019] Another object of the present invention is to provide a wide-bandgap perovskite solar cell, the structure of which from bottom to top sequentially includes

[0020] an ITO substrate layer with a thickness of 0.6 - 0.8 mm and the material being ITO conductive glass;

[0021] a self-assembled molecular layer with a thickness of 0.1 - 1.5 nm and the material being 4PADCB;

[0022] a wide-bandgap perovskite light-absorbing layer with a thickness of 400 - 500 nm and the material being the wide-bandgap perovskite thin film described in claim 6;

[0023] an electron transport layer with a thickness of 10 - 30 nm and the material being C 60 ;

[0024] a hole blocking layer with a thickness of 6 - 8 nm or 10 - 20 nm and the material being 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or atomic layer deposited SnO2;

[0025] a metal electrode layer with a thickness of 100 - 200 nm and the material being silver or copper.

[0026] Another object of the present invention is to provide a tandem wide-bandgap perovskite solar cell, the structure of which from bottom to top sequentially includes

[0027] an ITO substrate layer with a thickness of 0.6 - 0.8 mm and the material being ITO conductive glass;

[0028] a self-assembled molecular layer with a thickness of 0.1 - 1.5 nm and the material being 4PADCB;

[0029] a wide-bandgap perovskite light-absorbing layer with a thickness of 400 - 500 nm and the material being the wide-bandgap perovskite thin film described in claim 6;

[0030] an electron transport layer with a thickness of 10 - 30 nm and the material being C 60 ;

[0031] an intermediate connection layer with a thickness of 80 - 90 nm and the material being SnO2 and IZO, wherein the thickness of SnO2 is 15 - 20 nm and the thickness of IZO is 65 - 70 nm;

[0032] a hole transport layer with a thickness of 20 - 25 nm and the material being PEDOT:PSS;

[0033] A narrow-bandgap perovskite absorption layer with a thickness of 800 - 900 nm and a material of (FASnI3) 0.6 (MAPbI3) 0.4 ;

[0034] An electron transport layer with a thickness of 10 - 30 nm and a material of C 60 ;

[0035] A hole blocking layer with a thickness of 6 - 8 nm or 10 - 20 nm and a material of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or atomic layer deposited SnO2;

[0036] A metal electrode layer with a thickness of 100 - 200 nm and a material of silver or copper.

[0037] Advantages of the present invention:

[0038] (1) For the first time in the present invention, INA / 2-CNA is incorporated into the wide-bandgap perovskite precursor solution, and then the perovskite solution is spin-coated to obtain a doped wide-bandgap perovskite light-absorbing layer film. When the precursor liquid contacts the SAM, the carboxyl groups of INA / 2-CNA will be attracted to the front interface, connect with SAM molecules, form a carboxyl skeleton, promote the connection of the buried interface. Secondly, chloride ions can be incorporated into the lattice to stabilize the perovskite phase and improve the device stability.

[0039] (2) The multi-functional group action of INA / 2-CNA in the present invention promotes the passivation of perovskite defects, improves the device stability and performance. It is mainly manifested as enhancing the interface connection, improving the film uniformity, reducing the non-radiative recombination, increasing the carrier lifetime, increasing the fill factor and current density, and improving the photoelectric conversion efficiency.

[0040] (3) Applying the wide-bandgap perovskite prepared by the present invention to a tandem cell can improve the open-circuit voltage and efficiency of the tandem device and enhance the stability. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0042] Figure 1 It is a structural diagram of a wide-bandgap perovskite solar cell doped with 2-chloroisonicotinic acid (2-CNA) in Embodiment 1 of the present invention.

[0043] Figure 2It is the scanning electron microscope image of the surface of the perovskite thin films prepared in Example 2 and Example 4 of the present invention.

[0044] Figure 3 It is the X-ray photoelectron spectroscopy image of the perovskite thin films obtained in Example 1, Example 3 and Comparative Example 1.

[0045] Figure 4 It is the X-ray diffraction pattern of the perovskite thin films obtained in Example 2, Example 4 and Comparative Example 1.

[0046] Figure 5 It is the time-resolved photoluminescence image of the perovskite thin films prepared in Example 1, Example 3 and Comparative Example 1.

[0047] Figure 6 It is the statistical comparison chart of the photovoltaic performance of the wide-bandgap perovskite solar cells prepared in Example 2 and Comparative Example 1.

[0048] Figure 7 It is the statistical comparison chart of the photovoltaic performance of the wide-bandgap perovskite solar cells prepared in Example 4 and Comparative Example 1.

[0049] Figure 8 It is the EQE spectrum and J-V curve of the wide-bandgap perovskite solar cells prepared in Example 2 and Comparative Example 1.

[0050] Figure 9 It is the EQE spectrum and J-V curve of the wide-bandgap perovskite solar cells prepared in Example 4 and Comparative Example 1.

[0051] Figure 10 It is the hysteresis scanning result of the wide-bandgap perovskite solar cells prepared in Example 1, Example 3 and Comparative Example 1.

[0052] Figure 11 It is the long-term stability comparison chart of the wide-bandgap perovskite solar cells prepared in Example 1, Example 3 and Comparative Example 1.

[0053] Figure 12 It is the J-V curve diagram of the tandem perovskite solar cell obtained in Example 5.

[0054] Figure 13 It is the long-term stability comparison chart of the wide-bandgap perovskite solar cells prepared in Example 1, Comparative Example 1 and Comparative Example 4. Detailed implementation manners

[0055] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention will be given in combination with the embodiments of the specification.

[0056] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0057] Secondly, as used herein, "an embodiment" or "embodiments" refer to specific features, structures, or characteristics that may be included in at least one implementation of the present invention. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0058] Unless otherwise specified, the raw materials used in the present invention are commercially available and commonly used in the art.

[0059] Unless otherwise specified, the method of stacking each layer of the perovskite solar cell of the present invention adopts the conventional magnetron sputtering method.

[0060] The performance test conditions of the present invention are as follows:

[0061] Photovoltaic conversion efficiency test:

[0062] Under illumination by a 100 mW cm -2 AM 1.5G solar simulator (SS-F5-3A, Enlitech), the light intensity measured using a Keithley 2400 source meter is calibrated by a standard silicon solar cell;

[0063] Steady-state power output:

[0064] Through maximum power point tracking test under constant illumination (100 mW cm -2 ) of an LED light source simulator, and the device is tested in an N 2 atmosphere without encapsulation and temperature control unit;

[0065] Carrier lifetime test:

[0066] Excited by a pulsed laser with a wavelength of 410 nm and an excitation frequency of 0.1 MHz, and the TRPL spectrum is fitted using double-exponential and triple-exponential functions.

[0067] Example 1

[0068] Referring to Figure 1 , this example provides a method for preparing a wide-bandgap perovskite solar cell doped with 2-chloroisonicotinic acid (2-CNA). Specifically:

[0069] 1) Using ITO conductive glass with a sheet resistance of 15 Ω, an average transmittance > 85%, and a thickness of 0.7 mm as the substrate material, it was successively cleaned with detergent, deionized water, acetone, and ethanol in an ultrasonic cleaner for 15 min, dried with a nitrogen gun, and then subjected to ultraviolet ozone treatment for 20 min to remove surface organic matter, obtaining a surface-clean ITO conductive glass layer, which is the pretreated ITO substrate with a thickness of approximately 0.7 mm.

[0070] 2) 4PADCB was dissolved in absolute ethanol to obtain a 4PADCB solution with a concentration of 0.5 mg / mL. The 4PADCB solution was dropped on the surface of the ITO substrate and spin-coated at a speed of 3000 rpm for 20 s. After spin-coating, it was annealed on a hot plate at 100 °C for 10 min to form a self-assembled molecular layer with a thickness of approximately 1 nm.

[0071] 3) 0.4 mmol of formamidinium iodide, 0.2 mmol of cesium iodide, 0.4 mmol of formamidinium bromide, 0.6 mmol of lead iodide, and 0.4 mmol of lead bromide were dissolved in 0.83 mL of a mixed solvent with a volume ratio of 3:1 of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Then, 3.2 mg of lead thiocyanate, 1 mg of potassium thiocyanate, and 1 mg of formamidinium thiocyanate were added to the solution to obtain a FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3 precursor solution;

[0072] Dissolve 2-CNA powder in the FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3 precursor solution to obtain a wide-bandgap perovskite precursor solution with a 2-CNA doping concentration of 1.0 mol%.

[0073] 4) 90 μL of the wide-bandgap perovskite precursor solution doped with 2-CNA was dropped on the SAM (self-assembled molecular layer) and spin-coated in two steps. The first spin-coating speed was 500 rpm for 2 s; the second spin-coating speed was 4000 rpm for 60 s. Among them, at the 23rd s of the second spin-coating, 750 μL of diethyl ether was added dropwise to the substrate as an antisolvent;

[0074] After spin-coating, the substrate was placed on a hot plate at 65 °C for annealing for 2 min, and then placed on a hot plate at 100 °C for annealing for 10 min to obtain a perovskite thin film, which is the wide-bandgap perovskite light-absorbing layer with a thickness of 450 nm.

[0075] 5) Ethylenediamine iodine powder was dissolved in an IPA solution to obtain a back passivation solution with a concentration of 1 mg / mL, stirred at 70 °C for 3 h, and filtered through a 0.22 μm PTFE filter to obtain an ethylenediamine iodine solution;

[0076] 80 μL of the ethylenediamine iodine solution was dropped onto the perovskite film, and then spun at 4000 rpm for 20 s, and immediately annealed at 100 °C for 5 min to achieve back passivation treatment.

[0077] 6) The product of step 5) was placed in a thermal evaporation chamber, and 20 nm of C -4 material was evaporated successively as the electron transport layer, 6 nm of BCP was evaporated as the hole blocking layer, and 100 nm of copper was evaporated as the metal electrode layer under a high vacuum of 4 × 10 60 Pa, thus preparing a wide-bandgap perovskite solar cell doped with 1.0 mol% 2-chloroisonicotinic acid.

[0078] Example 2

[0079] The difference between this example and Example 1 is that the doping concentration of 2-CNA in the wide-bandgap perovskite precursor solution in step 3) was adjusted to 0.5, 1, and 1.5 mol% respectively, and the processes of the remaining steps were all referred to Example 1, obtaining perovskite films and wide-bandgap perovskite solar cells with different 2-chloroisonicotinic acid doping concentrations in this example.

[0080] The performance of the wide-bandgap perovskite solar cell devices prepared in Example 2 was tested, and the results are shown in Table 1.

[0081] Table 1

[0082] 2-CNA concentration (mol%) <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF (%) PCE (%) 0.5 1.348 17.68 84.2 20.07 1 1.351 17.73 84.5 20.24 1.5 1.336 17.43 82.3 19.16

[0083] As can be seen from Table 1, adjusting the concentration of the additive in the wide-bandgap perovskite precursor solution has a significant impact on the performance of the solar cell. This is because the concentration of the additive itself will affect the passivation effect. Too high a concentration of the additive in the wide-bandgap perovskite precursor solution will lead to an increase in film defects and damage to the perovskite itself, while too low a concentration will result in insufficient passivation effect. According to the results in Table 1, the best technical effect can be obtained when the concentration of the wide-bandgap perovskite precursor solution in the present invention is 1.0 mol%.

[0084] Example 3

[0085] The difference between this example and Example 1 is that the doped 2-chloroisonicotinic acid (2-CNA) in step 3) was adjusted to isonicotinic acid, and the processes of the remaining steps were all referred to Example 1, obtaining a perovskite film and a wide-bandgap perovskite solar cell doped with 1 mol% isonicotinic acid in this example.

[0086] Example 4

[0087] The difference between this example and Example 3 lies in that the doping concentrations of isonicotinic acid in the wide-bandgap perovskite precursor solution in step 3) are adjusted to 0.5, 1, and 1.5 mol%, respectively. The processes of the remaining steps are all referred to Example 3 to obtain perovskite thin films and wide-bandgap perovskite solar cells with different isonicotinic acid doping concentrations in this example.

[0088] Performance tests were carried out on the wide-bandgap perovskite solar cell devices prepared in Example 4, and the results are shown in Table 2.

[0089] Table 2

[0090] Isonicotinic acid concentration (mol%) <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF (%) PCE (%) 0.5 1.339 17.51 83.1 19.48 1 1.345 17.54 83.6 19.72 1.5 1.325 17.47 82.7 19.14

[0091] As can be seen from Table 2, compared with Example 1, due to the subtraction of the chlorine group on the pyridine ring, there are certain deviations in different molecular configurations, resulting in different effects at the same concentration. Similarly, the influence of the concentration of INA on the wide-bandgap perovskite solar cell shows the same law as that of 2-CNA, thanks to the consistency of their main functional groups.

[0092] Figure 2 Scanning electron microscope images of the surfaces of the perovskite thin films prepared in Example 2 and Example 4 are shown. It can be seen that the surface of the perovskite thin film doped with 2-CNA is smoother and accompanied by some grain growth. After doping with INA / 2-CNA, the quality of the wide-bandgap thin film is improved, defects are passivated, and the introduction of chlorine elements optimizes the crystallization of perovskite.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 lies in that 2-CNA is not doped into the FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3 precursor solution. The processes of the remaining steps are all referred to Example 1 to obtain the wide-bandgap perovskite solar cell without 2-CNA doping in this comparative example.

[0095] Figure 3 X-ray photoelectron spectra of the perovskite thin films obtained in Example 1, Example 3, and Comparative Example 1 are shown. It can be seen that there is an obvious shift of the peak of lead in the wide-bandgap perovskite thin film doped with INA / 2-CNA towards the direction of lower binding energy, indicating that the doping of the additive passivates the uncoordinated lead ions and reduces the defect states.

[0096] Figure 4 X-ray diffraction patterns (XRD) of the perovskite thin films obtained in Example 2, Example 4, and Comparative Example 1 are shown. It can be seen that the (100) diffraction peak shifts towards a smaller angle, indicating that the chloride ions in 2-CNA can dissociate and incorporate into the perovskite lattice, thereby enhancing the lattice stability.

[0097] Figure 5 Time-resolved photoluminescence images of the perovskite thin films prepared in Example 1, Example 3, and Comparative Example 1 are shown. It can be seen that the carrier lifetime of the doped perovskite thin film is significantly increased, reaching more than 600 nanoseconds. This proves that INA / 2-CNA doping can effectively reduce the defect state density in the wide-bandgap perovskite thin film, thereby suppressing non-radiative recombination and increasing the carrier lifetime.

[0098] Figure 6 Statistical comparison charts of the photovoltaic performance of the wide-bandgap perovskite solar cells prepared in Example 2 and Comparative Example 1 are shown. It can be seen that the average values of the power conversion efficiency, open-circuit voltage, short-circuit current, and fill factor of the wide-bandgap device doped with 1.0 mol% 2-CNA are higher, and the device performance repeatability is better. Among them, the highest open-circuit voltage of the device can reach more than 1.35 V, and the open-circuit voltage loss is reduced to less than 0.42 V.

[0099] Figure 7 Statistical comparison charts of the photovoltaic performance of the wide-bandgap perovskite solar cells prepared in Example 4 and Comparative Example 1 are shown. It can be seen that the average values of the power conversion efficiency, open-circuit voltage, short-circuit current, and fill factor of the wide-bandgap device doped with 1.0 mol% INA are higher.

[0100] Figure 8 a and b are the EQE spectra and J-V curves of the wide-bandgap perovskite solar cells prepared in Example 2 and Comparative Example 1, respectively. It can be seen that as the doping concentration increases from 0.5 mol% to 1.5 mol%, the short-circuit current of the perovskite solar cell doped with 2-CNA shows a trend of first increasing and then decreasing, and it is most prominent at 1.0 mol%. At the same time, the increase and decrease of the current density can also be obtained from the EQE spectrum, which is the same as the trend shown in the J-V diagram. For the device doped with 2-CNA, the increase in current is mainly reflected in the wavelength band after 450 nm.

[0101] Figure 9 a and b are the EQE spectra and J-V curves of the wide-bandgap perovskite solar cells prepared in Example 4 and Comparative Example 1, respectively. It can be seen that as the doping concentration increases from 0.5 mol% to 1.5 mol%, the short-circuit current and current density of the perovskite solar cell doped with INA show a trend of first increasing and then decreasing, and it is most prominent at 1.0 mol%. The increase in current is similar to that of 2-CNA.

[0102] Figure 10 From the hysteresis scan results of the wide-bandgap perovskite solar cells prepared in Example 1, Example 3, and Comparative Example 1, it can be seen that INA / 2-CNA can effectively passivate the perovskite interface defects and improve the device performance and stability of the perovskite solar cell.

[0103] Figure 11 The wide-bandgap perovskite solar cells prepared in Example 1, Example 3, and Comparative Example 1 were stored in a nitrogen glove box, and the results of testing the photoelectric conversion efficiency of the wide-bandgap perovskite solar cells with the increase of storage time were obtained. It can be seen that the doping of 2-CNA / INA can effectively inhibit the decomposition of perovskite. Obviously, even after storing for more than 200 days, the efficiency of the wide-bandgap solar cell doped with 2-CNA still remains above 90% of the initial efficiency. However, after storing for 80 days, the photoelectric conversion efficiency of the device in Comparative Example 1 decreased significantly, less than 90% of the initial efficiency. It is proved that the stability of the perovskite solar cell doped with INA / 2-CNA has been greatly improved.

[0104] Example 5

[0105] This example provides a preparation method of a tandem perovskite solar cell applying the perovskite film of Example 1. Specifically:

[0106] 1) Referring to steps 1) - 5) of Example 1, a passivated wide-bandgap perovskite light-absorbing layer was prepared and placed in a thermal evaporation chamber. At a high vacuum of 4×10 -4 Pa, 20 nm of C 60 material was evaporated as the electron transport layer, and a 20 nm SnO2 layer was deposited on the surface of the electron transport layer by atomic layer deposition;

[0107] 2) The product obtained in step 2) was placed in a magnetron sputtering chamber. At a high vacuum of 4×10 -4 Pa, it was sputtered at 25 W for 22 min and then at 30 W for 22 min to obtain a 70 nm IZO layer;

[0108] 3) A 20 nm PEDOT:PSS layer was spin-coated on the product obtained in step 3) at a spin-coating speed of 6000 rpm for 40 s. After spin-coating, it was placed on a hot plate at 150 °C and annealed for 20 min to obtain a hole transport layer with a thickness of 20 nm;

[0109] 4) 1 mmol of stannous iodide, iodomethylammonium, and 5 mmol% of stannous fluoride were dissolved in a DMF / DMSO mixed solvent to prepare a FASnI3 solution with a concentration of 1.57 mmol / mL;

[0110] 1 mmol of lead iodide, iodomethylamine, and 3.5 mmol% of lead thiocyanate were dissolved in a DMF / DMSO mixed solvent to prepare a MAPbI3 solution of 1.57 mmol / mL;

[0111] The FASnI3 solution and the MAPbI3 solution were mixed in a ratio of 6:4 and stirred at room temperature to obtain a clear and transparent (FASnI3) 0.6(MAPbI3) 0.4 Narrow-bandgap perovskite precursor solution

[0112] 5) The product of step 3) is transferred to a glove box filled with N2 for the deposition of perovskite thin films.

[0113] 80 μL (FASnI3) 0.6 (MAPbI3) 0.4 The narrow-bandgap perovskite precursor solution is spin-coated on the PEDOT:PSS layer at 1000 rpm for 10 s and 4000 rpm for 60 s. During the spin-coating process, 700 μL of diethyl ether is dropped. After the spin-coating is completed, annealing is carried out at 65 °C for 3 min and 100 °C for 7 min to obtain a perovskite thin film;

[0114] Ethylenediamine iodide powder is dissolved in an IPA solution to obtain a back-passivation solution with a concentration of 1 mg / mL. 80 μL of the back-passivation solution is dropped on the perovskite thin film, and after spin-coating at 4000 rpm for 20 s, annealing is immediately carried out at 100 °C for 5 min to form a narrow-bandgap perovskite absorption layer;

[0115] 6) The product obtained in step 5) is placed in a thermal evaporation chamber, and 20 nm of C -4 material is evaporated in sequence under a high vacuum of 4 × 10 60 Pa as the electron transport layer, 6 nm of BCP is evaporated as the hole blocking layer, and 100 nm of copper is evaporated as the metal electrode layer, thus obtaining the tandem perovskite solar cell modified with 2-CNA in this Example 2.

[0116] Measure the performance of the tandem perovskite solar cell prepared in this Example. The results are as Figure 12 shown. It can be seen that the device has excellent performance, with a photoelectric conversion efficiency of 28.87% and an open-circuit voltage reaching 2.129 V.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that 2-chloroisonicotinic acid (2-CNA) doped in step 3) is adjusted to 2-chloro-5-aminopyridine, and the process of the remaining steps refers to Example 1, obtaining the perovskite thin film doped with 1 mol% of 2-chloro-5-aminopyridine and the wide-bandgap perovskite solar cell in this comparative example.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 1 is that 2-chloroisonicotinic acid (2-CNA) doped in step 3) is adjusted to triethanolamine phosphate, and the process of the remaining steps refers to Example 1, obtaining the perovskite thin film doped with 1 mol% of triethanolamine phosphate and the wide-bandgap perovskite solar cell in this comparative example.

[0121] The performance of the devices obtained in the above comparative examples was tested and compared with that of Example 1 and Comparative Example 1. The results are shown in Table 3.

[0122] Table 3

[0123] <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF (%) PCE (%) Example 1 1.351 17.73 84.5 20.24 Comparative Example 1 1.330 17.30 82.6 19.01 Comparative Example 2 1.323 17.32 82.8 18.97 Comparative Example 3 1.303 17.27 81.5 18.34

[0124] As can be seen from the above table, due to the absence of the doping of 2-chloroisonicotinic acid, the optoelectronic properties of Comparative Example 1 are inferior to those of Example 1, especially in terms of the short-circuit current. The current is increased from 17.30 mA / cm 2 to 17.73 mA / cm 2 , which proves that the doping of 2-CNA in Example 1 can enhance the interface connection, passivate the film defects, and reduce the transmission loss. The passivation effect of the additives doped in Comparative Examples 2 and 3 is far inferior to that of Example 1, which proves the particularity of 2-CNA.

[0125] Comparative Example 4

[0126] The difference between this comparative example and Example 1 is that 2-CNA doped in step 3) is adjusted to 2-FNA (2-fluoroisonicotinic acid), and the processes of the remaining steps are all referred to Example 1, obtaining the perovskite film doped with 1 mol% 2-chloro-5-aminopyridine and the wide-bandgap perovskite solar cell in this comparative example.

[0127] Comparative Example 5

[0128] The difference between this comparative example and Example 1 is that 2-chloroisonicotinic acid (2-CNA) doped in step 3) is adjusted to 2-chloro-5-fluoroisonicotinic acid, and the processes of the remaining steps are all referred to Example 1, obtaining the perovskite film doped with 1 mol% 2-chloro-5-fluoroisonicotinic acid and the wide-bandgap perovskite solar cell in this comparative example.

[0129] The performance of the devices obtained in the above comparative examples was tested and compared with that of Example 1 and Comparative Example 1. The results are shown in Table 4.

[0130] Table 4

[0131] <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF (%) PCE (%) Example 1 1.351 17.73 84.5 20.24 Comparative Example 1 1.330 17.30 82.6 19.01 Comparative Example 4 1.339 17.47 81.9 19.16 Comparative Example 5 1.346 17.58 79.3 18.76

[0132] As can be seen from the above table, due to the too small radius of the fluoride ion in 2-fluoroisonicotinic acid, the incorporation into the lattice leads to the collapse of the perovskite lattice. Although its optoelectronic performance is superior to that of Comparative Example 1, it is still weaker than that of Example 1, and there is a significant decrease in stability, such as Figure 13As shown. However, 2-chloro-5-fluoroisonicotinic acid causes a serious decrease in device filling, so the efficiency is greatly reduced, proving that doping 2-CNA in Example 1 can enhance lattice stability, passivate film defects, and reduce transport losses. The additives doped in Comparative Example 4 and Comparative Example 5 change specific functional groups, making their passivation effects far inferior to those in Example 1, proving the particularity of 2-CNA.

[0133] Comparative Example 6

[0134] The difference between this comparative example and Example 1 is that 2-chloroisonicotinic acid (2-CNA) doped in step 3) is adjusted to o-carboxyphenylacetic acid, and the processes of the remaining steps are all referred to Example 1 to obtain the perovskite film doped with 1 mol% o-carboxyphenylacetic acid and the wide-bandgap perovskite solar cell in this comparative example.

[0135] Perform performance tests on the devices prepared in the above comparative examples, and compare them with Example 1 and Comparative Example 1. The results are shown in Table 5.

[0136] Table 5

[0137] <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF (%) PCE (%) Example 1 1.351 17.73 84.5 20.24 Comparative Example 1 1.330 17.30 82.6 19.01 Comparative Example 6 1.336 17.43 82.8 19.28

[0138] It can be seen from the above table that due to the passivation effect of the carboxyl group, the device obtained in Comparative Example 6 is slightly better than Comparative Example 1, but lacks the additional passivation effect of chloride ions and the regulation of the lattice, and its performance is weaker than that of the device doped with 2-chloroisonicotinic acid, verifying the positive effect of chloride ions on perovskite crystallization and proving the particularity of 2-chloroisonicotinic acid.

[0139] In summary, in the present invention, INA / 2-CNA is first used to be incorporated into the wide-bandgap perovskite precursor solution, and then the perovskite solution is spin-coated to obtain a doped wide-bandgap perovskite light-absorbing layer film. When the precursor solution contacts the SAM, the carboxyl groups of INA / 2-CNA will be attracted to the front interface and connected to the SAM molecules to form a carboxyl skeleton, promoting the connection of the buried interface. Secondly, chloride ions can be incorporated into the lattice to stabilize the perovskite phase and improve the device stability.

[0140] The multi-functional group effect of INA / 2-CNA in the present invention promotes perovskite defect passivation, improves device stability and performance. It is mainly manifested as enhancing interface connection, improving film uniformity, reducing non-radiative recombination, increasing carrier lifetime, increasing fill factor and current density, and improving photoelectric conversion efficiency.

[0141] Applying the wide-bandgap perovskite prepared in the present invention to a tandem cell can improve the open-circuit voltage and efficiency of the tandem device and enhance the stability.

[0142] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a wide-bandgap perovskite thin film, characterized in that: including, Pyridine-based organic acids are soluble in FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 )3 A wide-bandgap perovskite precursor solution with a doping concentration of 0.5 - 1.5 mol% is obtained in the precursor solution; A wide-bandgap perovskite precursor solution is spin-coated on a substrate in two steps and then annealed in two steps to obtain a wide-bandgap perovskite thin film.

2. The preparation method of the wide-bandgap perovskite thin film according to claim 1, wherein: The pyridine-based organic acid includes one of 2-chloroisonicotinic acid or isonicotinic acid.

3. The preparation method of the wide-bandgap perovskite thin film according to claim 1, wherein: The rotation speed of the first spin-coating in the two-step spin-coating is 450 - 500 rpm, and the time is 2 - 3 s; the rotation speed of the second spin-coating is 4000 - 5000 rpm, and the time is 60 - 70 s.

4. The method for preparing the wide-bandgap perovskite thin film according to claim 3, wherein: At 22 - 25 s of the second spin-coating, diethyl ether is dropped as an anti-solvent.

5. The preparation method of the wide-bandgap perovskite thin film according to claim 4, characterized in that: The dropping amount of diethyl ether compared to the wide-bandgap perovskite precursor solution is 70 - 80:8 - 9 (μL).

6. The preparation method of the wide-bandgap perovskite thin film according to claim 1, wherein: The first annealing in the two-step annealing is annealing at 60 - 65 °C for 2 - 3 min, and the second annealing is annealing at 100 - 105 °C for 8 - 10 min.

7. A wide-bandgap perovskite thin film prepared by the preparation method according to any one of claims 1 - 6.

8. The application of the wide-bandgap perovskite thin film according to claim 6 in the preparation of a wide-bandgap perovskite solar cell.

9. A wide-bandgap perovskite solar cell, characterized in that: The structure from bottom to top sequentially includes, An ITO substrate layer with a thickness of 0.6 - 0.8 mm and the material of ITO conductive glass; A self-assembled molecular layer with a thickness of 0.1 - 1.5 nm and the material of 4PADCB; A wide-bandgap perovskite light-absorbing layer with a thickness of 400 - 500 nm and the material of the wide-bandgap perovskite thin film according to claim 6; The electron transport layer has a thickness of 10 to 30 nm and the material is C 60 ; A hole-blocking layer with a thickness of 6 - 8 nm or 10 - 20 nm and the material of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or atomic layer deposited SnO2; A metal electrode layer with a thickness of 100 - 200 nm and the material of silver or copper.

10. A laminated wide-bandgap perovskite solar cell, characterized in that: The structure from bottom to top sequentially includes, An ITO substrate layer with a thickness of 0.6 - 0.8 mm and the material of ITO conductive glass; A self-assembled molecular layer with a thickness of 0.1 - 1.5 nm and the material of 4PADCB; A wide-bandgap perovskite light-absorbing layer with a thickness of 400 - 500 nm and the material of the wide-bandgap perovskite thin film according to claim 6; The electron transport layer has a thickness of 10 to 30 nm and is made of material C 60 ; An intermediate connection layer with a thickness of 80 - 90 nm and the material of SnO2 and IZO, wherein the thickness of SnO2 is 15 - 20 nm and the thickness of IZO is 65 - 70 nm; A hole-transporting layer with a thickness of 20 - 25 nm and the material of PEDOT:PSS; Narrow-bandgap perovskite absorption layer, with a thickness of 800 - 900 nm and a material of (FASnI3) 0.6 (MAPbI3) 0.4 ; The electron transport layer has a thickness of 10 to 30 nm and is made of material C 60 ; A hole-blocking layer with a thickness of 6 - 8 nm or 10 - 20 nm and the material of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or atomic layer deposited SnO2; A metal electrode layer with a thickness of 100 - 200 nm and the material of silver or copper.

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