Perovskite material solution, perovskite film and preparation method and application thereof

Abstract

The invention discloses a perovskite material solution, a perovskite film and a preparation method and application thereof, and the preparation method of the perovskite material solution uses a high-boiling-point solvent as an independent additive, specifically, after a perovskite precursor is completely dissolved and filtered, the high-boiling-point solvent (a single or composite system) is quantitatively added, and the perovskite material solution is prepared. Subsequent preparation of the perovskite film can achieve the following effects by accurately controlling the vacuumizing rate and the processing time: (1) the crystallization window period is prolonged due to the slow evaporation characteristic of the high-boiling-point solvent, perovskite crystal grains are promoted to grow orderly, a uniform and compact film microstructure is formed, internal stress accumulation caused by rapid crystallization is effectively relieved, and the performance of the perovskite film is improved; the cracking risk is obviously reduced; and (2) solvent molecules are preferentially enriched in a grain boundary region in a deposition process, and uncoordinated Pb < 2 + > defects are passivated through coordination, so that the defect density of the thin film is reduced, and the photoelectric conversion efficiency of a device is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite materials, and particularly relates to a perovskite material solution, a perovskite film and a preparation method and application thereof. BACKGROUND

[0002] At present, the highest certified efficiency of crystalline silicon solar cells has reached 27.1%, close to the theoretical efficiency limit of 29%. In order to further break through the efficiency bottleneck, reducing thermalization loss and efficiently utilizing photon energy become the key. For example, the efficiency of four-junction solar cells based on GaAs material has reached 47%, fully demonstrating the great potential of multi-junction solar cell technology in breaking through the efficiency limit. Perovskite material has become an extremely attractive light-absorbing material due to its wide band gap (1.2-2.0 eV), excellent stability, high efficiency, low cost, low-temperature processing and good compatibility with tandem structure. The theoretical limit efficiency of perovskite solar cells is 33%, and the laboratory efficiency has reached 26.95%. By combining wide-bandgap perovskite with narrow-bandgap solar cells, high-performance double-junction tandem solar cells can be constructed, such as perovskite-silicon tandem solar cells, whose highest efficiency has reached 34.85%, showing broad commercial application prospects.

[0003] Whether it is single-junction or tandem structure perovskite solar cells, the preparation of high-quality perovskite absorber layer is always the core element determining the performance of the device. However, the ubiquitous problem of film cracking not only significantly reduces the photoelectric conversion efficiency, but also seriously affects the industrial aesthetics and long-term reliability of the product. Solution coating, as the mainstream technology for the preparation of current perovskite solar cells, mainly includes spin coating, slot coating, blade coating, inkjet printing, roll-to-roll coating and other technologies. These methods have the remarkable advantages of simple process, low cost, flexibility, strong scalability and flexible component regulation. In a typical solution process, after the precursor solution is coated to form a wet film, Vacuum-Assisted Crystallization (VAC) technology is usually used for subsequent processing. This technology adjusts the solvent evaporation rate by precisely controlling the cavity pressure drop rate to optimize the crystallization process, especially suitable for the preparation of large-area perovskite films, which can significantly improve the film uniformity.

[0004] However, the film cracking problem in the VAC process has become the main bottleneck restricting the development of the technology, and the causes mainly include: the solvent evaporation rate is too fast, leading to stress concentration, imbalance of crystallization kinetics, thermal stress mismatch and improper vacuum control. Among them, the film cracking caused by thermal stress mismatch and improper vacuum control can be solved by process parameters such as solvent evaporation regulation, annealing process optimization, and vacuum equipment improvement. However, the film cracking problem caused by internal stress generated during the crystallization process is more complex and difficult to control by conventional methods. This cracking can seriously affect the performance of perovskite solar cells, leading to a decrease in efficiency and poor stability. Therefore, solving the film cracking problem caused by crystallization stress in the VAC process is a key challenge to improve the performance of perovskite cells or related stacked cells. SUMMARY

[0005] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a preparation method of a perovskite material solution. The second purpose of the present application is to provide a perovskite material solution prepared by the above preparation method. The third purpose of the present application is to provide a perovskite film. The fourth purpose of the present application is to provide a preparation method of the above perovskite film. The fifth purpose of the present application is to provide a perovskite cell.

[0006] The present application innovatively uses a high-boiling-point solvent as an independent additive, mainly through delaying the crystallization rate, optimizing stress release and improving film uniformity. This method can effectively reduce the risk of film cracking, improve the performance and stability of perovskite solar cells, and has important application value.

[0007] In order to achieve the above purposes, the technical scheme adopted by the present application is:

[0008] The first aspect of the present application provides a preparation method of a perovskite material solution, comprising the following steps:

[0009] S1, dissolving A halide-containing compound and B metal compound in a first solvent, and filtering after fully mixing to collect the filtrate;

[0010] The first solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide; A in the A halide-containing compound is Cs, methylamine or formamidine; B in the B metal compound is at least one of Pb, Sn and Mn;

[0011] S2, adding a high-boiling-point solvent to the filtrate of S1 to prepare the perovskite material solution;

[0012] The boiling point of the high-boiling-point solvent is 200-260℃ at 1 atm.

[0013] Preferably, the A-containing halide comprises at least one of CsI, MA Br, FAI, MACI.

[0014] Preferably, the molar ratio of the A-containing halide to the first solvent is 1:(6-12).

[0015] Preferably, the B metal compound is selected from at least one of BI2, BBr2, BCI2.

[0016] Preferably, the molar ratio of the B metal compound to the first solvent is 1:(6-12).

[0017] Preferably, in step S1, the first solvent comprises N,N-dimethylformamide (DMF) and dimethyl sulfoxide.

[0018] More preferably, the volume ratio of the N,N-dimethylformamide and dimethyl sulfoxide is (3-5):1.

[0019] Preferably, in step S1, the specific step of sufficient mixing comprises stirring at 15-40℃ for 3-6h.

[0020] Preferably, in step S1, the filtering is performed by using a filter membrane with a pore size of 0.10-0.45μm.

[0021] More preferably, the filter membrane is made of PTFE.

[0022] Preferably, the high-boiling-point solvent comprises at least one of γ-butyrolactone (GBL, Gamma-Butyrolactone), N-methyl-2-pyrrolidone (NMP, N-Methyl-2-pyrrolidone), N,N'-dimethylpropyleneurea (DMPU, N,N'-Dimethylpropyleneurea), diethylene glycol (DEG, Diethylene Glycol), 1,3-dimethyl-2-imidazolidinone (DMI, 1,3-Dimethyl-2-imidazolidinone).

[0023] The high-boiling-point solvent can meet the following requirements:

[0024] (1) high boiling point: the boiling point should be significantly higher than DMF (153℃) and DMSO (189℃), usually above 200℃; (2) good solubility: can effectively dissolve perovskite precursors (such as PbI2, MAI, FAI, etc.), and form a uniform mixed solution with DMF / DMSO; (3) chemical stability: no decomposition or side reactions occur during perovskite film preparation (such as high-temperature annealing or light conditions); (4) low volatility: moderate evaporation rate during deposition, can cooperate with DMF / DMSO to regulate the crystallization process; (5) compatibility with DMF / DMSO: can be completely miscible with DMF and DMSO, forming a stable homogeneous solution; (6) low toxicity: low toxicity, less harmful to the human body and the environment; (7) regulation ability of perovskite crystallization: can reduce internal stress accumulation by adjusting the crystallization rate and crystal growth direction; (8) influence on device performance: does not significantly reduce the photoelectric performance (such as carrier mobility, absorption coefficient, etc.) of perovskite thin film; (9) process compatibility: suitable for existing VCD or solution process (such as spin coating, blade coating); (10) cost and availability: moderate cost, easy to obtain.

[0025] The high-boiling-point solvent of the present application mainly functions in the step of vacuum extraction (prevents film cracking during vacuum extraction), preferentially extracts low-boiling-point solvents such as DMF (153℃) and DMSO (189℃), while retaining high-boiling-point solvents (such as DMI, 220℃), forming a gradient evaporation system. The subsequent annealing evaporates the residual high-boiling-point solvent. The perovskite material solution of the present application realizes gradient drying by combining vacuum extraction and annealing.

[0026] Preferably, the volume ratio of the high-boiling-point solvent to the filtrate is (0.003-0.03):1.

[0027] More preferably, the volume ratio of the high-boiling-point solvent to the filtrate is (0.005-0.02):1.

[0028] Preferably, the method of adding the high-boiling-point solvent in step S2 comprises the following steps: slowly adding the high-boiling-point solvent to the filtrate of S1, and accompanying ultrasonic-assisted dispersion.

[0029] More preferably, the high-boiling-point solvent is added dropwise to the filtrate of S1, and accompanied by ultrasonic-assisted dispersion.

[0030] The second aspect of the present application provides a perovskite material solution prepared by the preparation method of the first aspect.

[0031] The third aspect of the present application provides a perovskite film, which is prepared from the perovskite material solution of the second aspect.

[0032] The fourth aspect of the present application provides a preparation method of the perovskite film of the third aspect, comprising the following steps: coating the perovskite material solution on a substrate, evaporating the solvent in the solution, crystallizing the perovskite material, and forming the perovskite film.

[0033] Preferably, the coating method is spin coating, wherein the spin coating speed is 500-4000 rpm, and the spin coating time is 10-40 s.

[0034] More preferably, the coating method is two-step spin coating, wherein the first step spin coating speed is 500-1000 rpm, the spin coating time is 5-15 s; the second step spin coating speed is 3000-4000 rpm, and the spin coating time is 10-20 s.

[0035] Preferably, the solvent is further evaporated by vacuumizing continuously for a period of time and then annealing, wherein the annealing temperature is 70-110 ℃, and the annealing time is 10-60 min.

[0036] More preferably, the annealing temperature is 90-110 ℃, and the annealing time is 20-40 min.

[0037] More preferably, the vacuumizing specifically comprises the following steps: obtaining the perovskite wet film after coating, placing the perovskite wet film in a vacuum chamber, and vacuumizing the chamber.

[0038] The solvent in the perovskite wet film is extracted by vacuum treatment to form a supersaturated solution for crystallization.

[0039] Further preferably, the chamber pressure in the vacuum chamber is 1-10 Pa, and the treatment time is 30-80 s.

[0040] The fifth aspect of the present application provides a perovskite battery, which comprises the perovskite film of the third aspect.

[0041] Preferably, the perovskite battery comprises a conductive substrate, a hole transport layer, a perovskite layer, a passivation layer, an electron transport layer, a buffer layer, and an electrode which are sequentially stacked; and the perovskite layer uses the perovskite film of the third aspect.

[0042] More preferably, the material of the hole transport layer comprises a carbazole derivative.

[0043] More preferably, the material of the electron transport layer comprises at least one of fullerene (C60) and its derivative, PCBM, and 3TPYMB.

[0044] More preferably, the passivation layer uses a lithium fluoride layer (LiF) and an ethylenediamine iodine (EDAI) double-layer passivation film.

[0045] The present application has the following beneficial effects:

[0046] The application provides a perovskite material solution, a perovskite film and a preparation method and application thereof, in the preparation method of the perovskite material solution, a high-boiling-point solvent is used as an independent additive, specifically, after the perovskite precursor is completely dissolved and filtered, the high-boiling-point solvent (single or composite system) is quantitatively added, and then the perovskite film is prepared by accurately controlling the deposition temperature and pressure, so that the following synergistic effects are realized: (1) crystallization kinetics regulation: the high-boiling-point solvent prolongs the crystallization window period due to the slow evaporation characteristics, promotes the ordered growth of perovskite crystal grains, forms a uniform and dense film microstructure, effectively alleviates the internal stress accumulation caused by rapid crystallization, and significantly reduces the cracking risk; (2) defect passivation mechanism: solvent molecules preferentially accumulate in the grain boundary area during the deposition process, passivate uncoordinated Pb 2+ defects through coordination, reduce the defect density of the film, and improve the photoelectric conversion efficiency of the device; (3) process compatibility advantage: the additive strategy does not need to modify the existing VCD equipment, and can adapt to industrial production by optimizing the type and proportion of the solvent.

[0047] The perovskite film prepared by the application has the characteristics of uniformity and denseness, reduces the cracking risk and the defect density in the film body phase, and improves the overall quality of the perovskite film. The perovskite film of the application can significantly improve the open-circuit voltage and efficiency of the perovskite battery when applied to the perovskite battery, and has great application potential in perovskite-crystalline silicon stacked solar cell devices. DETAILED DESCRIPTION

[0048] The content of the application is further described in detail through specific examples. In the following examples, the raw materials used, unless otherwise specified, can be obtained from conventional commercial channels or prepared and separated by simple synthesis; the processes used, unless otherwise specified, are conventional processes in the art.

[0049] Example 1

[0050] The example provides a perovskite material solution, a perovskite and a perovskite solar cell, the structure of the perovskite solar cell is a conductive substrate, a hole transport layer, a perovskite layer, a passivation layer, an electron transport layer, a buffer layer and an electrode which are sequentially stacked, and the preparation steps are as follows:

[0051] Step one: place the silicon wafer substrate in isopropyl alcohol and ultrasonically clean for 3 minutes; before use, treat with UV-ozone for 30 minutes to enhance the hydrophilicity of the substrate surface;

[0052] Step two: prepare a 0.5 mg / mL DMF solution of the organic small molecule [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid, and spin-coat 30 μL of the solution prepared in step one on the silicon substrate at 3000 rpm, 1500 rpm / s (rpm / s is the unit of acceleration of rotation speed, here it means the rotation speed of the coating equipment is accelerated at 1500 rpm per second), a 30 s program, and anneal at 100°C for 10 min after spin-coating. The hole transport layer film is obtained after cooling;

[0053] Step three: prepare a perovskite solution, weigh 39.5 mg of CsI, 51.0 mg of MABr, 418 mg of FAI, 332 mg of PbBr2, and 1057 mg of PbI2 according to the stoichiometric ratio, and dissolve them in 2 mL of mixed solvent DMF:DMSO (V:V=4:1), and add 5% excess PbX2 (X=I, Br). Continuously stir the mixed solution at room temperature for 4 hours to ensure that the precursors are fully dissolved; use a 0.22 μm PTFE microporous filter to pressurize the filter, and collect the filtrate for use. Measure the amount of the filtrate, and accurately add 0.3% of high-boiling-point solvent DMI to the perovskite solution, and add it dropwise with ultrasonic-assisted dispersion;

[0054] Step four: Before spin-coating the perovskite, the glove box is cleaned for at least 10 minutes to eliminate possible residual organic atmosphere. Use a two-step spin-coating+VAC process, the first step spin-coating parameters are 500 rpm, 300 rpm / s, 7 s, and the second step spin-coating parameters are 3000 rpm, 1500 rpm / s, 13 s. After spin-coating, quickly place the perovskite wet film in a vacuum chamber, and perform vacuum operation on the chamber, and maintain the chamber pressure at 5 Pa, and keep the pressure in the vacuum environment for 50 seconds to obtain a brownish perovskite film, and then immediately transfer the film to a hot plate at 100°C for annealing for 30 min, and obtain the perovskite film after cooling;

[0055] Step five: post-processing optimization: use the thermal evaporation method to prepare ~1 nm of LiF. Use the ultrasonic method to dissolve the organic salt ethylenediamine dihydroiodide (EDAI) in IPA, and the optimal concentration is 0.3 mg / ml. The EDAI solution is spin-coated on the LiF-coated perovskite surface at 3000 rpm for 30 s, and then annealed at 100°C for 5 min. After cooling, drop the IPA solvent on the substrate at a rotation speed of 5000 rpm, and wash the possible residual EDAI material with water;

[0056] Step six: 25nm C60 is evaporated on the perovskite film prepared in step five and Sn02sputter buffer layer (12nm) is deposited by atomic layer deposition (ALD) for 100 cycles (100℃ for chamber, 70℃ for TDMASn source, 1.2s pulse, 5s purge, 20℃ for H2O, 1s pulse, 5s purge, 90sccm carrier gas N2);

[0057] Step seven: 40nm indium zinc oxide (IZO) transparent electrode is deposited by magnetron sputtering.

[0058] Step eight: 500nm Ag electrode is vacuum evaporated at an evaporation speed of

[0059] Step nine: 70nm MgF2 is thermally evaporated on the active area.

[0060] Example 2

[0061] This example provides a preparation method of perovskite-crystalline silicon laminated solar cell, which is basically the same as that of example 1, except that 0.5% high-boiling-point solvent DMI is accurately added to the perovskite solution according to the volume of the perovskite solution, and a composite solution is obtained after mixing.

[0062] Example 3

[0063] This example provides a preparation method of perovskite-crystalline silicon laminated solar cell, which is basically the same as that of example 1, except that 1% high-boiling-point solvent DMI is accurately added to the perovskite solution according to the volume of the perovskite solution, and a composite solution is obtained after mixing.

[0064] Example 4

[0065] This example provides a preparation method of perovskite-crystalline silicon laminated solar cell, which is basically the same as that of example 1, except that 1.5% high-boiling-point solvent DMI is accurately added to the perovskite solution according to the volume of the perovskite solution, and a composite solution is obtained after mixing.

[0066] Example 5

[0067] This example provides a preparation method of perovskite-crystalline silicon laminated solar cell, which is basically the same as that of example 1, except that 2% high-boiling-point solvent DMI is accurately added to the perovskite solution according to the volume of the perovskite solution, and a composite solution is obtained after mixing.

[0068] Example 6

[0069] This example provides a preparation method of perovskite-crystalline silicon laminated solar cell, which is basically the same as that of example 1, except that 2.5% high-boiling-point solvent DMI is accurately added to the perovskite solution according to the volume of the perovskite solution, and a composite solution is obtained after mixing.

[0070] Example 7

[0071] This example provides a preparation method of perovskite-crystalline silicon tandem solar cell, which is basically the same as that of Example 1, except that 3% of high-boiling solvent DMI is accurately added according to the volume of perovskite solution, and the composite solution is obtained after mixing.

[0072] Comparative Example 1

[0073] This comparative example provides a preparation method of perovskite-crystalline silicon tandem solar cell, which is basically the same as that of Example 1, except that no high-boiling reagent is added in step three of the preparation method.

[0074] Comparative Example 2

[0075] This comparative example uses a conventional solvent mixing process to prepare a perovskite precursor solution, which is different from Example 1 in that the specific method of step three is to dissolve the high-boiling solvent DMI (the same amount as in Example 1) and the perovskite precursor in the initial liquid preparation stage, i.e., in the DMF:DMSO (V:V=4:1) mixed solvent, and then use it after 4 hours of stirring and 0.22 μm PTFE filter membrane filtration. Except for the different introduction of the additive, the rest is the same as Example 1.

[0076] Application Test

[0077] Under the same conditions, the perovskite cells obtained in Examples 1-7 and Comparative Examples 1-2 were tested for photoelectric conversion efficiency and stability. The specific test method is as follows:

[0078] Photoelectric conversion efficiency test: under room temperature conditions, using a 3A solar simulator, the photoelectric conversion efficiency of the perovskite cell was tested under 100 mW / cm 2 light intensity, and the effective area of the cell was 1 cm 2 . Photoelectric conversion efficiency (PCE) = Pmax / Pin, where Pmax is the maximum power in the process of photoelectric conversion, and Pin is the input power of the light source. Fill factor (FF) = Pmax / Jsc·Voc, where Pmax is the maximum power in the process of photoelectric conversion, Jsc is the short-circuit current density, and Voc is the open-circuit voltage.

[0079] The test results are shown in Table 1:

[0080] Table 1

[0081] Sample PCE (%) JSC(mAcm -2 )]]> VOC (V) FF (%) Film cracking Example 1 29.17 21.09 1.916 72.19 Slightly cracked Example 2 30.49 21.29 1.895 75.58 No cracking Example 3 30.68 20.59 1.932 77.12 No cracking Example 4 31.30 20.85 1.954 76.83 No cracking Example 5 30.84 20.83 1.927 76.83 No cracking Example 6 28.65 20.75 1.915 72.10 No cracking Example 7 28.13 20.12 1.913 71.69 No cracking Comparative Example 1 29.34 21.24 1.888 73.13 Cracked Comparative Example 2 28.69 21.09 1.905 71.41 No cracking

[0082] From Table 1, we can see that:

[0083] (1) Through Examples 1-7 and Comparative Example 1, it can be obtained that the addition of high-boiling-point additive DMI can improve the performance of the device, and the optimal concentration range is 0.5-2%. Too low additive concentration (0-0.5%) cannot solve the problem of cracking of the perovskite film, and the solvent evaporation rate is not low enough, and the FF of the device is reduced; the content of 0.5-2% high-boiling-point solvent is the optimal crystallization window period, which promotes the ordered growth of perovskite grains, forms a uniform and dense film microstructure, effectively relieves the accumulation of internal stress caused by rapid crystallization, and the performance of the device reaches the peak; and the use of excessive high-boiling-point additive (>2%) delays crystallization, leading to phase separation, increasing the surface roughness of the perovskite film, and reducing the overall performance of the device.

[0084] (2) Through Examples 1-7 and Comparative Example 2, it can be obtained that the early introduction of high-boiling-point solvent additive in the perovskite precursor solution leads to a decrease in the performance of the device, and the conventional solvent (DMF / DMSO) and Pb 2 + exist a dynamic coordination balance (such as Pb←O=S=O). The early addition of high-boiling-point solvent (such as DMI) will compete for coordination sites, forming a metastable Pb←DMI complex, leading to coordination unsaturated defects in the subsequent perovskite crystallization process. In addition, the early presence of additives will prolong the solvent evaporation time, leading to overgrown grains.

[0085] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, which are all included in the protection scope of the present application.

Claims

1. A method for preparing a perovskite material solution, characterized in that, Includes the following steps: S1. Dissolve the halide containing A and the metal compound containing B in the first solvent, mix thoroughly, filter, and collect the filtrate; The first solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide; the A in the A-containing halide is Cs, methylamine, or formamidinium; the B in the B metal compound is at least one of Pb, Sn, and Mn. S2. Add a high-boiling-point solvent to the filtrate of S1 to obtain the perovskite material solution; The boiling point of the high-boiling solvent is 200–260 °C at 1 atm.

2. The method for preparing the perovskite material solution according to claim 1, characterized in that, The A-containing halide includes at least one of CsI, MABr, FAI, and MACl; The B metal compound is selected from at least one of BI2, BBr2, and BCl2.

3. The method for preparing the perovskite material solution according to claim 1, characterized in that, The high-boiling-point solvent includes at least one of γ-butyrolactone, N-methyl-2-pyrrolidone, N,N'-dimethylpropenylurea, diethylene glycol, and 1,3-dimethyl-2-imidazolinone.

4. The method for preparing the perovskite material solution according to claim 1, characterized in that, The volume ratio of the high-boiling-point solvent to the filtrate is (0.003~0.03):

1.

5. The method for preparing the perovskite material solution according to claim 1, characterized in that, The method for adding the high-boiling-point solvent in step S2 includes the following steps: slowly adding the high-boiling-point solvent to the filtrate of S1, accompanied by ultrasonic-assisted dispersion.

6. The perovskite material solution prepared by the preparation method according to any one of claims 1-5.

7. A perovskite film, characterized in that, The perovskite film is prepared from the perovskite material solution according to claim 5.

8. The method for preparing the perovskite film according to claim 7, characterized in that, The process includes the following steps: coating the perovskite material solution onto a substrate, allowing the solvent in the solution to evaporate, and allowing the perovskite material to crystallize to form a perovskite film.

9. The method for preparing a perovskite film according to claim 8, characterized in that, The solvent is further evaporated by continuously evacuating the vacuum for a period of time and then annealing. The annealing temperature is 70-110℃ and the annealing time is 10-60min.

10. A perovskite solar cell, characterized in that, The perovskite solar cell includes the perovskite membrane of claim 7.