A liquid-gas interface preparation method of metal halide perovskite ultrathin monocrystal nanosheet

Abstract

The application discloses a liquid-gas interface preparation method of metal halogen perovskite ultrathin monocrystal nanosheet, and belongs to the field of semiconductor photoelectric materials. The chemical general formula of the inorganic perovskite is A3B2I9, A is Cs, and B is Sb or Bi. A liquid-gas interface growth method is realized by additionally adding I2 to the solvent HI. The functions of I2 are as follows: (1) assisting the inorganic halogen perovskite to realize liquid-gas interface growth; (2) regulating the growth rate, size and aspect ratio of the thickness and lateral size of the material; (3) in-situ filling the internal defects of the perovskite, which can not only improve the stability of the material, but also optimize the fluorescent properties of the material, and improve the photoelectric response rate and detection rate. The method is simple in operation and low in cost, and realizes the unsupported preparation of the all-inorganic halogen perovskite ultrathin nanosheet for the first time. The product obtained by the method is extremely easy to transfer, and greatly simplifies the process flow of heterojunction stacking and micro-nano optoelectronic device construction.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of semiconductor optoelectronic materials, and relates to a liquid-gas interface preparation technology of metal halide perovskite ultrathin single crystal nanosheets. BACKGROUND

[0002] Metal halide perovskites have broad application prospects in high-performance optoelectronic devices due to their easy processing, excellent optical and electrical properties. Ultrathin single crystal nanosheets of metal halides, on the one hand, inherit the advantages of single-crystal-type perovskite materials, such as long balanced carrier diffusion path, high carrier mobility, and high light absorption efficiency, and on the other hand, have the advantages of two-dimensional semiconductor materials in the fields of heterostructure construction and micro-nano device integration, thus having more significant advantages in high-performance optoelectronic devices.

[0003] Although metal halide perovskite ultrathin nanosheets have so many advantages, at present, such materials are mostly obtained by high-temperature gas phase method [Adv. Optical Mater. 2018, 1800879, Nano-Micro Lett. 2021 13:165] or liquid phase confinement method [J. Am. Chem. Soc. 2016, 138, 16196-16199, Adv. Optical Mater. 2021, 9, 2001930]. The growth conditions of these two methods are harsh, the yield is low, and the obtained nanosheets are not easy to exfoliate. Only after a tedious transfer step, they can be applied to optoelectronic devices. Therefore, for the development of metal halide perovskites in high-performance optoelectronic devices, the best solution is to develop an effective preparation method suitable for high-quality, easy-to-exfoliate perovskite ultrathin nanosheets. A liquid-gas interface floating growth method brings opportunities for the preparation of high-quality perovskite single crystal nanosheets. SUMMARY

[0004] The technical problem to be solved by the application is to realize the lateral growth of ultrathin inorganic perovskite nanosheets, in-situ fill the internal defects of iodine-based perovskite, improve the stability of the material, optimize the fluorescence performance of the material, and improve the photoelectric response rate and detection rate of the material. The method is simple to operate and low in cost, and for the first time realizes the unsupported preparation of all-inorganic halide perovskite ultrathin nanosheets. At the same time, the product obtained by the method is easy to transfer, greatly simplifying the process flow of heterojunction stacking and micro-nano optoelectronic device construction.

[0005] In order to solve the technical problems of the present application, the technical scheme is proposed: the disclosed liquid-gas interface preparation method of metal halide perovskite ultrathin monocrystal nanosheet is suitable for pure inorganic perovskite of chemical general formula A3B2I9, wherein A is Cs, and B is Sb or Bi. The liquid-gas interface preparation method is that the perovskite nanosheet floats on the liquid surface, the thickness is effectively controlled, and rapid lateral growth is achieved.

[0006] The growth process is as follows:

[0007] Step one: prepare a precursor solution, add AI and BI3 raw materials to the HI solution according to the molar ratio, and stir and dissolve in the air environment at 60-80°C.

[0008] Step two: prepare a precursor solution with added I2, add I2 to the prepared precursor solution, and set the I2 content to 0.4-2.0 mol / L.

[0009] Step three: prepare metal halide perovskite ultrathin monocrystal nanosheet, apply a pipette to take 5-10 mL of the precursor solution, drop it onto the target substrate, and dry it in the air environment at 30-50°C. A large number of ultrathin monocrystal nanosheets are obtained on the substrate.

[0010] Preferably, the precursor solvent is HI, and additional additives I2 are required for assistance.

[0011] Preferably, the growth mechanism is that I2 spontaneously diffuses from bottom to top in the solution, delivering perovskite precursors to the liquid surface. The precursors float on the liquid surface under the combined action of surface tension and buoyancy. The surface tension reduces the nucleation and growth energy of the precursors at the interface, achieving rapid lateral growth of ultrathin inorganic perovskite nanosheets.

[0012] Preferably, the application of I2 assistance first realizes the unsupported preparation of all-inorganic halide perovskite ultrathin nanosheets. I2 plays multiple roles in the growth process: first, it assists inorganic halide perovskite to achieve liquid-gas interface growth; second, it controls the growth rate, size, and aspect ratio of the material thickness and lateral size; third, it fills in the defects in the perovskite in situ, which not only improves the material stability but also optimizes the fluorescence properties of the material, improving the photoelectric response rate and detection rate.

[0013] Preferably, the liquid-gas interface provides a natural confined space for inorganic perovskite growth, which is an effective platform for preparing atomically thin materials.

[0014] Preferably, the nanosheet floats on the solution surface and is easily peeled off from the solution surface, which is beneficial for heterojunction preparation and optoelectronic device construction.

[0015] Preferably, the thickness of the obtained perovskite single crystal nanosheet is 5-15 nm at the thinnest and 100-370 nm at the thickest; the lateral size is 6-10 mu m at the smallest and > 100 mu m at the largest.

[0016] Preferably, the method meets the ultrathin growth of inorganic perovskites with different lattice structures such as zero-dimensional and two-dimensional; the ultrathin growth of inorganic perovskites with different chemical components; and does not depend on any substrate.

[0017] Preferably, the required growth time is short, about 240s-420s, mainly controlled by the growth temperature, wherein the growth time becomes shorter as the temperature rises.

[0018] Beneficial effects

[0019] The present application provides a kind of liquid-gas interface preparation method of metal halogen perovskite ultrathin single crystal nanosheet, with inorganic halogen perovskite as research target, should be suitable for the preparation of all I base inorganic perovskite ultrathin single crystal nanosheet, it is not only suitable for a variety of chemical components, but also meets the growth of perovskite ultrathin nanosheet with different lattice structures, and does not depend on any growth substrate.The method can prepare inorganic perovskite into ultrathin single crystal nanosheet;A kind of liquid-gas interface growth method is realized by additionally adding I2 to solvent HI.Growth mechanism is, I2 spontaneously diffuses from bottom to top in solution, and perovskite precursor is sent to liquid surface, and precursor floats on liquid surface under the joint action of surface tension and buoyancy, and surface tension reduces the nucleation and growth energy of precursor at the interface, to realize the lateral growth of ultrathin inorganic perovskite nanosheet.The role of I2: (1) assist inorganic halogen perovskite to realize liquid-gas interface growth;(2) control the growth rate, size and aspect ratio of material thickness and lateral size;(3) in-situ fill the internal defects of iodine-based perovskite, improve the stability of material, optimize the fluorescence performance of material, improve the photoelectric response rate and detection rate of material.The method is simple in operation and low in cost, and first realizes the unsupported preparation of all-inorganic halogen perovskite ultrathin nanosheet.The product obtained by the method is easy to transfer, which greatly simplifies the process flow of heterojunction stacking and micro-nano optoelectronic device construction.

[0020] The present application provides a kind of liquid-gas interface preparation method of metal halogen perovskite ultrathin single crystal nanosheet, for the first time, I2 is used to assist, realize halogen perovskite ultrathin nanosheet liquid-gas interface growth.

[0021] The present application provides a kind of liquid-gas interface preparation method of metal halogen perovskite ultrathin single crystal nanosheet, embodies the multifaceted role of I2, not only can control the thickness and lateral size of material, but also can spontaneously fill the internal defects of material in the process of material.

[0022] The application provides a liquid-gas interface preparation method of metal halide perovskite ultrathin monocrystal nanosheets. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The growth flow chart of the metal halide perovskite ultrathin monocrystal nanosheets.

[0024] Figure 2 The optical and AFM pictures of the halide perovskite Cs3Bi2I9 ultrathin monocrystal nanosheets.

[0025] Figure 3 The XRD and Raman characterization of the halide perovskite Cs3Bi2I9 ultrathin nanosheets.

[0026] Figure 4 The optical and AFM pictures of the halide perovskite Cs3Bi2I9 large-size monocrystal nanosheets.

[0027] Figure 5 The optical and AFM pictures of the halide perovskite Cs3Bi2I9 thin monocrystal nanosheets.

[0028] Figure 6 The schematic diagram of the soft transfer process of picking up the floating nanosheets by PDMS and transferring to a target substrate and a target sample.

[0029] Figure 7 The preparation method used in the application is suitable for the preparation of various inorganic ultrathin perovskites, and the obtained ultrathin perovskites are easy to be transferred and assembled into vertical heterojunctions.(a) Cs3Bi2I9 nanosheets are extracted from the solution surface by PDMS.(b) Cs3Sb2I9 nanosheets are prepared on a SiO2 / Si substrate by using an HI+I2 solution.(c) Cs3Bi2I9 / Cs3Sb2I9 vertical heterojunction, Cs3Bi2I9 is transferred onto Cs3Sb2I9.

[0030] Figure 8 The growth of the halide perovskite ultrathin nanosheets on the liquid-gas interface.

[0031] Figure 9 The optical picture of the monocrystal nanosheets of the product obtained by using the pure HI precursor solution.

[0032] Figure 10 The fluorescence spectrum and fluorescence lifetime of the Cs3Bi2I9 monocrystal nanosheets obtained by using the HI and HI+I2 (1.0 mol / L) precursor solutions.

[0033] Figure 11 The photoelectric response and the function relationship between the photoelectric detection rate and the incident light power of the obtained Cs3Bi2I9 single crystal nanosheet from the HI precursor solution and the nanosheet treated by I2 vapor. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. The described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] Embodiment 1

[0036] The liquid-gas interface preparation method of the metal halide perovskite ultrathin single crystal nanosheet proposed in the embodiment can obtain high-quality zero-dimensional Cs3Bi2I9 ultrathin single crystal nanosheet at a liquid-gas interface.

[0037] The precursor solution is configured: CsI and BiI3 are added to the HI solution according to a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, and heating is performed at an environment of 60°C to promote mixing.

[0038] The precursor solution containing I2 is configured: after the above precursor solution is uniformly mixed, I2 is weighed, and a precursor solution containing I2 with an I2 amount of 0.8 mol / L is configured.

[0039] Preparation of nanosheet Figure 1 , and the specific steps are as follows:

[0040] Step one: cut the sapphire substrate into 1x1 cm 2 , ultrasonic clean the sapphire substrate with deionized water, alcohol, acetone and other solutions, and blow dry the substrate with nitrogen for standby;

[0041] Step two: apply O2 plasma to treat the sapphire substrate for 240 s to obtain a substrate with good hydrophilicity for standby;

[0042] Step three: use a pipette to take 10 mL of the precursor solution and drop it onto the surface of the substrate;

[0043] Step four: stand still at an environment of 40°C for 240 s, evaporate the solution, and obtain the nanosheet.

[0044] Characterization of nanosheet: the average lateral size of the nanosheet is about 10 μm confirmed by optical microscope, the thickness is about 6.9 nm Figure 2 confirmed by AFM characterization; and the lattice structure and molecular structure of the nanosheet are confirmed by XRD and Raman.Figure 3 )。

[0045] Example 2

[0046] The embodiment proposes a liquid-gas interface preparation method of a metal halide perovskite ultrathin single crystal nanosheet, which can obtain high-quality zero-dimensional Cs3Bi2I9 ultrathin single crystal nanosheet at a liquid-gas interface.

[0047] Prepare the precursor solution: add CsI and BiI3 to the HI solution according to a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, and heat in an environment of 60°C to promote mixing.

[0048] Prepare the precursor solution containing I2: after the above precursor solution is uniformly mixed, weigh I2 to prepare a precursor solution containing I2 with an I2 amount of 2.0 mol / L.

[0049] Prepare the nanosheet, and the specific steps are as follows:

[0050] Step one: cut the sapphire substrate into 1*1 cm 2 , ultrasonic clean the sapphire substrate with deionized water, alcohol, acetone and other solutions, and blow dry the substrate with nitrogen for standby;

[0051] Step two: apply O2 plasma to the sapphire substrate for 240s to obtain a substrate with good hydrophilicity for standby;

[0052] Step three: use a pipette to take 5mL of the precursor solution and drop it onto the surface of the substrate;

[0053] Step four: stand still at 50°C for 240s, evaporate the solution, and obtain the nanosheet.

[0054] Characterization of the nanosheet: use an optical microscope to confirm that the average lateral size of the nanosheet is about 120μm, and AFM characterization confirms that the thickness is about 112nm Figure 4 ).

[0055] Example 3

[0056] The embodiment proposes a liquid-gas interface preparation method of a metal halide perovskite ultrathin single crystal nanosheet, which can obtain high-quality zero-dimensional Cs3Bi2I9 ultrathin single crystal nanosheet at a liquid-gas interface.

[0057] Prepare the precursor solution: add CsI and BiI3 to the HI solution according to a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, and heat in an environment of 60°C to promote mixing.

[0058] Preparation of precursor solution containing I2: After the above-mentioned precursor solution is uniformly mixed, I2 is weighed, and a precursor solution containing I2 is prepared, in which the amount of I2 is 0.4 mol / L.

[0059] The preparation of nanosheets is as follows:

[0060] Step one: cutting the sapphire substrate into 1x1 cm 2 , ultrasonic cleaning the sapphire substrate with deionized water, alcohol, acetone and the like, and blowing the substrate dry with nitrogen for standby;

[0061] Step two: applying O2 plasma to the sapphire substrate for 240 s to obtain a substrate with good hydrophilicity for standby;

[0062] Step three: taking 10 mL of the precursor solution with a pipette and dropping it onto the surface of the substrate;

[0063] Step four: standing still at 50°C for 240 s, evaporating the solution, and obtaining nanosheets. The average lateral size of the nanosheets is about 15 μm confirmed by a microscope, and the thickness is about 61 nm confirmed by AFM. Figure 5

[0064] Example 4

[0065] The liquid-gas interface preparation method of the metal halide perovskite ultrathin single crystal nanosheet proposed in this embodiment can realize rapid preparation of heterojunction. Figure 6

[0066] Step one: preparation of three-dimensional Cs3Sb2I9 single crystal nanosheet

[0067] (1) Preparation of precursor solution: CsI and SbI3 are added to the HI solution according to a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, which is heated at an environment of 60°C to promote mixing.

[0068] (2) Preparation of precursor solution containing I2: After the above-mentioned precursor solution is uniformly mixed, I2 is weighed, and a precursor solution containing I2 is prepared, in which the amount of I2 is 1.0 mol / L.

[0069] (3) Cutting the SiO2 / Si substrate into 1x1 cm 2 , ultrasonic cleaning the sapphire substrate with deionized water, alcohol, acetone and the like, and blowing the substrate dry with nitrogen for standby;

[0070] (4) Applying O2 plasma to the sapphire substrate for 240 s to obtain a substrate with good hydrophilicity for standby;

[0071] (5) Taking 5 mL of the precursor solution with a pipette and dropping it onto the surface of the substrate; ​​

[0072] (6) 40 °C ambient static 240 s, the solution was evaporated to obtain Cs3Sb2I9 nanosheets Figure 7 b).

[0073] Step two: preparation of floating zero-dimensional Cs3Bi2I9 nanosheets

[0074] (1) Preparation of precursor solution: CsI and BiI3 were added to the HI solution in a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, and heated at 60 °C to promote mixing.

[0075] (2) Preparation of I2-containing precursor solution: After the above precursor solution was mixed uniformly, I2 was weighed to prepare an I2-containing precursor solution containing 1.0 mol / L of I2.

[0076] (3) The sapphire substrate was cut into 1 × 1 cm 2 , and the sapphire substrate was ultrasonically cleaned with deionized water, alcohol, acetone and other solutions, and the substrate was dried with nitrogen for standby;

[0077] (4) The sapphire substrate was treated with O2 plasma for 240 s to obtain a substrate with good hydrophilicity for standby;

[0078] (5) 10 mL of precursor solution was taken with a pipette and added dropwise to the surface of the substrate;

[0079] (6) 40 °C ambient static 100 s, observed and located under the microscope floating on the liquid surface and grown to the target size of the nanosheet.

[0080] Step three: heterojunction transfer

[0081] (1) The boundary of the nanosheet was gently contacted with a clean PDMS, and slowly pulled up, and the Cs3Bi2I9 nanosheet was adsorbed on the surface of the PDMS.

[0082] (2) The Cs3Sb2I9 nanosheet on the SiO2 / Si substrate was positioned under the microscope, and the Cs3Bi2I9 nanosheet on the PDMS was also positioned, wherein the SiO2 / Si substrate was fixed, and the Cs3Sb2I9 and Cs3Bi2I9 were opposite to each other. The specific transfer steps are shown in Figure 9 .

[0083] (3) After positioning, the Cs3Bi2I9 nanosheet attached to the surface of the PDMS was dropped and pressed onto the Cs3Sb2I9 below, and the softness of the PDMS was used to expel the air bubbles between the two nanosheets. Under the action of electrostatic adsorption, the Cs3Bi2I9 nanosheet fell on the Cs3Sb2I9 above to obtain a Cs3Bi2I9 / Cs3Sb2I9 heterojunctionFigure 7 )。

[0084] Example 5

[0085] The liquid-gas interface preparation method of the metal halide perovskite ultrathin single crystal nanosheet in Examples 1-4 can only achieve the ultrathin growth of the perovskite nanosheet in the I2-assisted precursor solution.

[0086] The growth process is observed in situ under a microscope. In order to confirm the growth position of the material, the rough back silicon is selected as the substrate, and it is found that the nucleation and remaining of the nanosheet can only be observed when the lens is focused on the liquid surface, and the nanosheet cannot be observed when the lens is focused on the rough back silicon. Therefore, the nanosheet of the system satisfies the liquid-gas interface growth process Figure 8 ), and the present application is a liquid-gas interface growth method, in which the perovskite nanosheet floats on the liquid surface, the thickness is effectively controlled, and the lateral growth is rapid.

[0087] Comparative Example 1

[0088] The liquid-gas interface preparation method of the metal halide perovskite ultrathin single crystal nanosheet proposed in the embodiment cannot achieve the ultrathin growth of the perovskite nanosheet in the I2-free precursor solution.

[0089] The precursor solution is configured: CsI and BiI3 are added to the HI solution in a molar ratio of 3:1 to obtain a precursor solution with a concentration of 0.02 mol / L, and the mixture is heated at 60°C to promote mixing.

[0090] The preparation of the nanosheet is as follows:

[0091] Step one: cut the sapphire substrate into 1*1 cm 2 , ultrasonic clean the sapphire substrate with deionized water, alcohol, acetone and other solutions, and blow dry the substrate with nitrogen for standby;

[0092] Step two: apply O2 plasma to the sapphire substrate for 240 s to obtain a substrate with good hydrophilicity for standby;

[0093] Step three: use a pipette to take 10 mL of the precursor solution and drop it onto the surface of the substrate;

[0094] Step four: wait for 200 s in a 40°C environment, evaporate the solution, and obtain the nanosheet. Characterization of the nanosheet: the average lateral size of the nanosheet is about 12 μm confirmed by a microscope, and the thickness is about 1.08 μm Figure 9 ) confirmed by AFM characterization.

[0095] Comparative Example 2

[0096] The embodiment provides a liquid-gas interface preparation method of a metal halide perovskite ultrathin single crystal nanosheet.

[0097] The solvent is a Cs3Bi2I9 precursor solution of pure HI solution and HI+I2 (1.0 mol / L), and fluorescence spectrum and fluorescence lifetime of obtained Cs3Bi2I9 nanosheets are tested. Figure 10 ).

[0098] The product added with I2 has stronger fluorescence spectrum intensity and longer fluorescence lifetime, which proves smaller defect concentration. The I2 has a regulating effect on the fluorescence spectrum and fluorescence lifetime of the product.

[0099] Comparative example 3

[0100] The embodiment provides a liquid-gas interface preparation method of a metal halide perovskite ultrathin single crystal nanosheet.

[0101] The solvent is a Cs3Bi2I9 precursor solution of pure HI solution, and the solution is transferred to an Au electrode (60 nm), photoelectric current of the device is tested, and photoresponse rate of the obtained device is calculated. Figure 11 ).

[0102] I2 vapor fumigation is performed on the same device, and it is found that the photoelectric response rate and the detection rate of the device are improved by one order of magnitude. The I2 has a regulating effect on the fluorescence spectrum and fluorescence lifetime of the product. ​ ).

Claims

1. A liquid-gas interface method for preparing metal halide perovskite ultrathin monocrystalline nanosheets, characterized in that: The perovskite satisfies a general chemical formula A3B2I9, wherein A is Cs, and B is Sb or Bi; and is a liquid-gas interface growth method, in which perovskite nanosheets float on the surface of a liquid, the thickness is effectively controlled, and rapid lateral growth is achieved; The specific steps are as follows: Step one: prepare a precursor solution, add AI and BI3 raw materials to the HI solution according to the molar ratio, and stir and dissolve at 60-80 DEG C in an air environment; Step two: prepare a precursor solution with I2 added, add I2 to the prepared precursor solution, and set the I2 content to 0.4-2.0mol / L; Step three: prepare metal halide perovskite ultrathin monocrystalline nanosheets, apply a pipette to take 5-10 mL of the precursor solution, drop it onto the target substrate, and air dry at 30-50 DEG C in an air environment, to obtain a large number of ultrathin monocrystalline nanosheets on the substrate; The solution required for material growth is HI, and additional additives I2 are required for assistance; The growth mechanism is that I2 spontaneously diffuses from bottom to top in the solution, and transports perovskite precursors to the liquid surface, the precursors float on the liquid surface under the combined action of surface tension and buoyancy, the surface tension reduces the nucleation and growth energy of the precursors at the interface, and rapid lateral growth of ultrathin inorganic perovskite nanosheets is achieved; The required growth time is short, between 240s and 420s, mainly controlled by the growth temperature, and the growth time becomes shorter as the temperature rises; The liquid-gas interface provides a natural confined space for inorganic perovskite growth, The nanosheets float on the surface of the solution, are peeled off from the surface of the solution, and are beneficial to the preparation of heterojunctions and the construction of optoelectronic devices.

2. The method of claim 1, wherein: The obtained perovskite monocrystalline nanosheets have a thickness of 5-15nm at the thinnest and 100-370nm at the thickest, a lateral size of 6-10mm at the smallest and >100mm at the largest.

3. The method of claim 1, wherein: The method meets the ultrathin growth of inorganic perovskites with different lattice structures and different chemical components, and does not depend on any substrate.

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