Quasi-two-dimensional perovskite thin film based on binary mixed solvent and preparation method and application of quasi-two-dimensional perovskite thin film

Abstract

The invention discloses a quasi-two-dimensional perovskite thin film based on a binary mixed solvent and a preparation method and application thereof, and belongs to the technical field of perovskite thin film and device preparation. A binary mixed solvent of dimethoxyethanol and propylene carbonate is used as a processing solvent of perovskite for the first time. Compared with pure dimethoxyethanol and propylene carbonate, the mixed use of dimethoxyethanol and propylene carbonate can improve the solubility of a single solvent to perovskite. The bromine-based two-dimensional perovskite is successfully dissolved by adopting the mixed solvent, the application range of dimethoxyethanol is widened, and meanwhile, the types of processing solvents available for perovskite are expanded. Based on the mixed solvent system, a high-quality quasi-two-dimensional perovskite thin film and a high-efficiency perovskite light-emitting diode can be prepared without an anti-solvent. The problem that an existing solvent depends on an anti-solvent is solved, and the experiment operation difficulty is lowered. The method has a huge potential application value in the field of perovskite photoelectric devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite device preparation, and particularly relates to a quasi-two-dimensional perovskite thin film based on a binary mixed solvent, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, perovskite materials have received extensive attention from the academic and industrial communities due to their excellent optoelectronic properties and low-cost solution processing, and great progress has been made in the fields of perovskite light-emitting diodes, perovskite solar cells, and photodetectors. Perovskite thin films are mostly prepared by a one-step solution method, that is, a perovskite precursor is dissolved in a corresponding solvent to prepare a precursor solution with a certain concentration, and then the thin film is prepared by spin coating or blade coating. However, during the solution preparation process, in order to ensure the solubility of the perovskite precursor, strongly coordinating solvents such as dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF) are mostly used. Therefore, in order to completely remove the solvent and regulate the nucleation and growth process of perovskite, toxic and harmful solvents such as chlorobenzene and chloroform are often used as anti-solvents during the spin coating process to prepare the thin film. The use of such solvents (anti-solvents) not only increases the difficulty of device preparation, but also poses a threat to the physical health of practitioners, which is not conducive to the large-scale processing and application of future perovskite devices. Therefore, the low-boiling-point and volatile solvent 2-methoxyethanol (2-ME) has been applied to the processing of perovskite thin films; however, limited by its relatively poor solubility in perovskite, 2-ME is currently mainly used to dissolve iodine-based perovskite, that is, mainly applied to the field of perovskite solar cells; but it has poor solubility in bromine-based perovskite, which limits its further application in the field of perovskite luminescence. Summary of the Invention

[0003] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for a quasi-two-dimensional perovskite thin film based on a binary mixed solvent.

[0006] To solve the above technical problems, the present invention provides the following technical solutions, including,

[0007] Mix dimethoxyethanol (2-ME) and propylene carbonate (PC) to prepare a mixed solvent, add a quasi-two-dimensional perovskite precursor to the mixed solvent to obtain a precursor solution; spin-coat the precursor solution into a film and then perform annealing treatment to obtain a quasi-two-dimensional perovskite film based on a binary mixed solvent.

[0008] Among them, the volume ratio of the 2-ME to the PC is (3-5):1.

[0009] As a preferred embodiment of the method for preparing the quasi-two-dimensional perovskite film based on a binary mixed solvent of the present invention, wherein: the quasi-two-dimensional perovskite precursor includes FABr, PbBr 2 , PBABr.

[0010] As a preferred embodiment of the method for preparing the quasi-two-dimensional perovskite film based on a binary mixed solvent of the present invention, wherein: the concentration of the precursor solution is 0.1-0.2 mol / L.

[0011] As a preferred embodiment of the method for preparing the quasi-two-dimensional perovskite film based on a binary mixed solvent of the present invention, wherein: the molar ratio of the FABr, PbBr 2 , PBABr is (0.67-1):1:(0.4-0.67).

[0012] As a preferred embodiment of the method for preparing the quasi-two-dimensional perovskite film based on a binary mixed solvent of the present invention, wherein: for the spin-coating, the rotation speed is 3000-5000 revolutions per minute and the time is 1-2 minutes.

[0013] As a preferred embodiment of the method for preparing the quasi-two-dimensional perovskite film based on a binary mixed solvent of the present invention, wherein: for the annealing, the annealing temperature is 60°C-90°C and the annealing time is 8-15 minutes.

[0014] Another object of the present invention is to overcome the deficiencies in the prior art and provide a quasi-two-dimensional perovskite film based on a binary mixed solvent.

[0015] The third object of the present invention is to overcome the deficiencies in the prior art and provide an application of a quasi-two-dimensional perovskite film based on a binary mixed solvent in the preparation of perovskite devices.

[0016] Advantages of the present invention:

[0017] (1) By introducing the second component solvent PC, the solubility of 2-ME in bromide-based perovskite is improved, the problem of low solubility of 2-ME in bromide-based perovskite is solved, and the application range of 2-ME is expanded.

[0018] (2) The 2-ME / PC mixed solvent is selected to prepare perovskite thin films and devices. Compared with traditional solvents such as DMSO and DMF, the use of antisolvents is avoided, the experimental operation difficulty is reduced, and the experimental repeatability is improved.

[0019] (3) The method of the present invention avoids the use of strong coordination solvents such as DMF and DMSO that are difficult to remove, and avoids the use of antisolvents. By using the 2-ME / PC mixed solvent, the quasi-two-dimensional perovskite light-emitting diode without antisolvent processing has a higher external quantum efficiency than the light-emitting diode prepared with DMSO under the same conditions. Brief Description of the Drawings

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0021] Figure 1 It is a dissolution photo of perovskite precursors by mixed solvents with different 2-ME / PC volume ratios;

[0022] Figure 2 It is a device structure diagram of a quasi-two-dimensional perovskite light-emitting diode;

[0023] Figure 3 It is a voltage-current density-luminance curve of a quasi-two-dimensional perovskite light-emitting diode;

[0024] Figure 4 It is a scanning electron microscope photo of quasi-two-dimensional perovskite thin films prepared with different 2-ME / PC ratios;

[0025] Figure 5 It is a dissolution photo of 2-ME and PC on perovskite precursors;

[0026] Figure 6 It is a dissolution photo of the mixed solutions of 2-ME and EC, PC, GVL, and DEC on perovskite precursors;

[0027] Figure 7 It is a scanning electron microscope photo of quasi-two-dimensional perovskite thin films prepared with different 2-ME / PC ratios;

[0028] Figure 8 It is an electron microscope photo of a quasi-two-dimensional perovskite thin film prepared with DMSO solvent;

[0029] Figure 9 It is a voltage-current density-luminance curve of a quasi-two-dimensional perovskite light-emitting diode prepared with DMSO solvent. Detailed Embodiments

[0030] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in combination with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0032] Secondly, the so - called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments.

[0033] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0034] The substances and their abbreviations are as follows:

[0035] 2 - methoxyethanol (2 - ME), propylene carbonate (PC), dimethyl sulfoxide (DMSO), formamidinium bromide (FABr), lead bromide (PbBr 2 ), phenylbutylammonium bromide (PBABr), indium tin oxide (ITO), poly(vinylcarbazole) (PVK), nickel oxide (NiO x ), 1,3,5 - tris[(3 - pyridyl)

[0036] -3 - phenyl]benzene (TmPyPb), lithium fluoride (LiF), ethylene carbonate (EC), γ - valerolactone (GVL), diethyl carbonate (DEC).

[0037] The prepared perovskite light - emitting diodes were subjected to performance tests:

[0038] The current density - voltage and luminance - voltage were measured in a nitrogen glove box using a Keithley 2400 source meter and a calibrated silicon photodiode. The voltage range was 0 - 9 V, the test step was 0.2 V, and the scanning rate was 0.2 V / s. The electroluminescence spectrum was recorded using a spectro - radiometer CS2000A. The external quantum efficiency was calculated based on the current density, luminance, and its electroluminescence spectrum on the premise that the light - emitting diode was assumed to be a Lambert source.

[0039] Example 1

[0040] This example compared the dissolution of quasi-two-dimensional perovskite precursors in 2-ME and PC mixed solvents with different volume ratios, as Figure 1 shown, specifically:

[0041] (1) Mix the two solvents, 2-ME and PC, in the ratios of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9.

[0042] (2) Take 4.69 mg of FABr, 18.4 mg of PbBr 2 and 5.8 mg of PBABr, mix them, and dissolve them in the above-mentioned mixed solvents with different ratios of 0.25 mL, 0.33 mL, and 0.5 mL. Stir for 3 hours and observe the dissolution situation.

[0043] The results show that the dissolution ability of the 2-ME / PC mixed solvent for perovskite changes with the volume change of the two. At the appropriate ratio, the solubility of the 2-ME / PC mixed solvent for perovskite exceeds 0.2 mol / L -1 .

[0044] Example 2

[0045] This example provides a method for preparing an efficient quasi-two-dimensional perovskite light-emitting diode based on a binary mixed solvent, specifically:

[0046] (1) Prepare a quasi-two-dimensional perovskite precursor solution based on the 2-ME / PC mixed solvent: Dissolve 15.0 mg of FABr, 55.1 mg of PbBr 2 and 17.3 mg of PBABr and 3 mg of a passivating agent in 1 mL of the 2-ME / PC (volume ratio 4:1) mixed solvent.

[0047] (2) Clean the ITO substrate: Clean the ITO substrate with a cleaning solution, then ultrasonically clean it with deionized water, acetone, and isopropanol for 10 minutes each, and then place it in an oven and dry it at 130 °C for later use.

[0048] (3) Prepare the NiO x hole transport layer: Place the above-mentioned ITO substrate on the chuck of a spin coater, and uniformly coat the 10 mg / mL NiO x aqueous solution on the substrate through a 0.22 μm filter head, spin coat it at a speed of 2000 rpm / min for 30 s, and then anneal it at 140 °C for 15 minutes to obtain the ITO / NiO x substrate.

[0049] (4) Prepare the PVK hole transport layer: Place the ITO / NiO xThe substrate is transferred into the glove box. After the substrate is cooled, it is placed on the chuck of a spin coater. Drop the prepared chlorobenzene solution of PVK with a concentration of 10 mg / mL onto the ITO / NiO x and spin coat it at a speed of 4000 rpm for 45 s, then anneal it at 150 °C for 30 min. -1 (5) Preparation of the quasi-two-dimensional perovskite thin film layer: Drop 120 μL of the quasi-two-dimensional perovskite precursor solution obtained in step (1) onto the prepared ITO / NiO

[0050] / PVK substrate and spin coat it at a speed of 4000 rpm for 1 min. After the spin coating is completed, place the substrate on a hot plate and anneal it at 70 °C for 10 min to obtain a thin film with high crystallinity. x (6) Preparation of the electron transport layer and the cathode: Transfer the substrate with the perovskite thin film layer prepared in step (5) into a vacuum coater, evacuate the air. When the pressure reaches 7×10

[0051] Pa, deposit a 60-nm-thick electron transport layer material TmPyPb, then deposit a 1-nm-thick LiF cathode modification layer and 100-nm Al as the cathode. Finally, a quasi-two-dimensional perovskite light-emitting diode is obtained. -5 (7) As shown in

[0052] the device structure is: ITO / NiO Figure 2 / PVK / Perovskite / TmPyPb / LiF / Al. The effective light-emitting area of this device is 0.14 cm x . The perovskite light-emitting layer in the figure is the quasi-two-dimensional perovskite thin film prepared based on the 2-ME / PC solvent described in the present invention. Its current density-luminance-voltage characteristic curve is as shown in 2 Figure 2 . Its performance parameters are shown in Table 1. The maximum luminance of the device exceeds 10000 cd / m 2 , and the maximum external quantum efficiency is 25.1%.

[0053] Example 3

[0054] The difference between this example and Example 2 is that the volume ratio of 2-ME and PC is adjusted to 5:1, and the rest of the preparation processes are the same as those in Example 2. A quasi-two-dimensional perovskite light-emitting diode is prepared, and its performance parameters are shown in Table 1.

[0055] Example 4

[0056] The difference between this example and Example 2 is that the volume ratio of 2-ME and PC is adjusted to 3:1, and the rest of the preparation processes are the same as those in Example 2. A quasi-two-dimensional perovskite light-emitting diode is prepared, and its performance parameters are shown in Table 1.

[0057] ​Figure 4 Scanning electron microscope photos of quasi-two-dimensional perovskite thin films prepared with different solvent ratios in Examples 1 to 3. It can be seen that continuous and dense thin films can be prepared at several solvent ratios.

[0058] Comparative Example 1

[0059] This comparative example compared the dissolution of the quasi-two-dimensional perovskite precursor based on 2-ME and PC solvents respectively. As Figure 5 shown, specifically:

[0060] Take 4.69 mg of FABr, 18.4 mg of PbBr 2 and 5.8 mg of PBABr, mix them and dissolve them in 0.25 mL, 0.33 mL and 0.5 mL of 2-ME solvent; similarly, dissolve the same amount of perovskite precursor in 0.25 mL, 0.33 mL and 0.5 mL of PC solvent respectively, and observe the dissolution situation.

[0061] The results show that the dissolution ability of single 2-ME and PC solvents for perovskite is poor, less than 0.1 mol L -1 . This result also fully shows that after the two are mixed, the dissolution ability of the mixed solvent for perovskite is greatly improved compared with that of the single solvent.

[0062] Comparative Example 2

[0063] This comparative example adjusted the types of solvents combined with 2-ME. Specifically:

[0064] (1) Mix 2-ME with EC, PC, GVL, and DEC respectively in a volume ratio of 4:1.

[0065] (2) Take the perovskite precursor and dissolve it in the above mixed solvent to prepare precursor solutions with concentrations of 0.1, 0.2, and 0.3 mol / L, stir for 3 hours, and observe the dissolution situation.

[0066] The results are as Figure 6 shown. It can be seen that the dissolution effect: 2-ME + EC > 2-ME + PC > 2-ME + GVL, and 2-ME + DEC is completely insoluble. EC is a solid at room temperature and will remain in the quasi-two-dimensional perovskite thin film in large amounts, resulting in poor performance of the quasi-two-dimensional perovskite light-emitting diode device.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 2 is that the volume ratio of 2-ME and PC is adjusted to 6:1, and the rest of the preparation processes are the same as those in Example 2. A quasi-two-dimensional perovskite light-emitting diode is prepared, and the performance parameters are shown in Table 1.

[0069] Comparative Example 4

[0070] This comparative example is different from Example 2 in that the volume ratio of 2-ME and PC is adjusted to 2:1, and the remaining preparation processes are the same as those in Example 2, obtaining a quasi-two-dimensional perovskite light-emitting diode, and the performance parameters are shown in Table 1.

[0071] Figure 7 Figure 6 is a scanning electron microscope photograph of quasi-two-dimensional perovskite thin films prepared with different 2-ME / PC ratios (6:1, 2:1, 1:1). The scanning electron microscope photographs of the thin films prepared based on the above solvent ratios show that their surface morphologies are worse than those of the thin films in Example 1, indicating that the solvent ratio not only affects its solubility in perovskite but also affects the crystallization of the subsequent perovskite thin film.

[0072] Comparative Example 5

[0073] This comparative example provides a method for preparing a quasi-two-dimensional perovskite light-emitting thin film and a light-emitting diode using the traditional solvent DMSO, specifically:

[0074] It is different from Example 2 in that the solvent 2-ME / PC is adjusted to DMSO, and the remaining preparation processes are the same as those in Example 2, obtaining a quasi-two-dimensional perovskite light-emitting diode, and its device structure is: ITO / NiO x / PVK / Perovskite / TmPyPb / LiF / Al. The effective light-emitting area of this device is 0.14 cm 2 .

[0075] Figure 8 Figure 7 is a scanning electron microscope photograph of the quasi-two-dimensional perovskite thin film prepared using DMSO as the solvent in this comparative example. It can be seen that there are many holes on the surface of the thin film prepared based on DMSO.

[0076] Figure 9 Figure 8 is its current density-luminance-voltage characteristic curve, and its performance parameters are shown in Table 1. The maximum luminance of the device is less than 2000 cd / m 2 , and the maximum external quantum efficiency is only 7.7%.

[0077] Table 1

[0078]

[0079] The present invention introduces a second-component PC solvent to construct a mixed solvent system with 2-ME, realizing the improvement of the solubility of bromine-based quasi-two-dimensional perovskite. Using a 2-ME and PC mixed solvent to prepare a quasi-two-dimensional perovskite precursor solution, a high-quality quasi-two-dimensional perovskite thin film is prepared, and then a highly efficient perovskite light-emitting diode is obtained. The preparation method avoids the use of strong coordination solvents such as DMF and DMSO that are difficult to remove and avoids the use of antisolvents.

[0080] In summary, by introducing the second component solvent PC, the present invention improves the solubility of 2-ME in bromine-based perovskite, solves the problem of low solubility of 2-ME in bromine-based perovskite, and expands the application range of 2-ME. The binary mixed solvent of 2-ME and PC is selected to prepare perovskite thin films and devices. Compared with traditional solvents such as DMSO and DMF, the use of anti-solvent is avoided, the experimental operation difficulty is reduced, and the experimental repeatability is improved. The quasi-two-dimensional perovskite light-emitting diode processed without anti-solvent using the 2-ME / PC mixed solvent has a higher external quantum efficiency than the light-emitting diode prepared with DMSO under the same conditions.

[0081] 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 by the scope of the claims of the present invention.

Claims

1. A method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent, characterized in that: include, Mixing dimethoxyethanol and propylene carbonate to prepare a mixed solvent, adding a quasi-two-dimensional perovskite precursor to the mixed solvent to obtain a precursor solution; The precursor solution is spin-coated into a film and then annealed to obtain a quasi-two-dimensional perovskite film based on a binary mixed solvent; Wherein, the volume ratio of dimethoxyethanol to propylene carbonate is (3-5):

1.

2. The method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent according to claim 1, characterized in that: The quasi-two-dimensional perovskite precursor includes formamidine bromide, lead bromide, and phenylbutylammonium bromide.

3. The method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent according to claim 1, characterized in that: The concentration of the precursor solution is 0.1-0.2 mol / L.

4. The method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent according to claim 2, characterized in that: The molar ratio of the formamidine bromide, lead bromide and phenylbutylammonium bromide is (0.67-1):1:(0.4-0.67).

5. The method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent according to claim 1, characterized in that: The spin coating has a rotation speed of 3000 to 5000 revolutions per minute and a time of 1 to 2 minutes.

6. The method for preparing a quasi-two-dimensional perovskite film based on a binary mixed solvent according to claim 1, characterized in that: The annealing process comprises an annealing temperature of 60° C. to 90° C. and an annealing time of 8 to 15 minutes.

7. A quasi-two-dimensional perovskite film based on a binary mixed solvent prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the quasi-two-dimensional perovskite film based on a binary mixed solvent as claimed in claim 7 in the preparation of a perovskite device.

9. The use of a quasi-two-dimensional perovskite film based on a binary mixed solvent as claimed in claim 8, characterized in that: The perovskite device includes a perovskite light emitting diode.

10. The use of the quasi-two-dimensional perovskite film based on a binary mixed solvent as claimed in claim 9, characterized in that: The method for preparing the perovskite light-emitting diode comprises the following steps: sequentially preparing a hole transport layer and a quasi-two-dimensional perovskite thin film layer by spin coating on a substrate, and then vacuum evaporating an electron transport layer and a cathode to obtain a perovskite light-emitting diode; Wherein, the substrate comprises ITO glass; the hole transport layer comprises NiOx / PVK, the electron transport layer comprises TmPyPb; and the cathode is a LiF / Al electrode.

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