Method for preparing perovskite single crystal thin film array with assistance of polymer

Abstract

The invention discloses a method for preparing a perovskite single crystal thin film array under the assistance of a polymer, which comprises the following steps of: preparing a groove with an adjustable periodic size on a silicon wafer cover plate by utilizing a photoetching process, dripping a perovskite precursor solution added with an oxygen-containing group polymer additive between the cover plate and a substrate, and putting the cover plate and the substrate into a self-made clamp, tightening the cover plate and the substrate by using screws to form a confinement space, regulating nucleation and growth of perovskite single crystals by using the oxygen-containing group polymer, and obtaining the size-controllable array perovskite single crystal thin film by using a space confinement method. According to the method for preparing the perovskite single crystal thin film array with the assistance of the polymer, the oxygen-containing group polymer is added into the perovskite precursor solvent, nucleation sites in the crystal growth process can be effectively reduced, crystal grain growth can be slowed down, the size-adjustable arrayed geometric confinement space is constructed in combination with the photoetching technology, and the perovskite single crystal thin film array can be obtained. Conformal growth of perovskite crystals is achieved, and the size-controllable array perovskite single crystal thin film is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic materials, and in particular to a method for preparing a perovskite single crystal thin film array with the assistance of a polymer. Background Art

[0002] The many excellent properties of perovskite materials, such as high absorption coefficient, excellent carrier transport characteristics, and tunable direct band gap, have had a wide and far-reaching impact in the field of optoelectronics. For example, in the photovoltaic field, the certified conversion efficiency of perovskite cells has reached 26.7%, which is competitive with traditional silicon-based photovoltaics. This has greatly encouraged researchers to apply this "dream material" to the development of other types of optoelectronic devices. In addition, hybrid perovskite materials can exhibit good bipolar properties and can be used as channel active layer materials for both n-type and p-type transistors, which is conducive to simplifying integrated circuit design and improving device integration. Therefore, perovskite thin-film transistor (TFT) technology is expected to become a supporting technology for the development of large-scale microelectronics on flexible substrates.

[0003] However, the perovskite semiconductor layers that make up optoelectronic devices are mostly polycrystalline films. The large number of surface defects and grain boundaries inherent in polycrystalline films will act as carrier capture and recombination centers, seriously hindering the transport of carriers and enhancing non-radiative recombination. In addition, the ion migration activation energy of the perovskite halogen site is low, which will cause TFTs based on polycrystalline films to be more susceptible to ion migration under the induction of the gate voltage electric field, thereby causing gate voltage shielding, and thus affecting the performance of the device. Compared with polycrystalline, the directional transmission properties and low defect state density of single crystal materials can effectively inhibit the occurrence of the above phenomena, reduce or even eliminate carrier scattering losses, and non-radiative recombination at grain boundaries. For example, Professor Luo Linbao's team produced lateral MAPbBr 3 Single crystal npn phototransistor for sensitive light detection, photocurrent amplification factor is 2.9×10 3 , the detection rate is as high as 4.67×10 13 The team led by Yongsheng Zhao from the Institute of Chemistry of the Chinese Academy of Sciences prepared MAPbBr by combining the spatially confined micropillar template-assisted capillary bridge rise method with the gas phase ion exchange method. 3 -MAPbBr 3-x I 3 Single crystal pn junction nanowire arrays have achieved 2.65×10 3 However, the perovskite single crystal thin film photodetector devices currently prepared by the confinement method still cannot meet the requirements of small integrated device design. Summary of the invention

[0004] The purpose of the present invention is to provide a method for polymer-assisted preparation of perovskite single crystal thin film arrays. By combining the spatial confinement method improved by photolithography process and polymer additive-assisted crystallization engineering, a universal method for long-chain polymers to be used in the growth of size-controllable perovskite single crystal thin film arrays is developed. The long-chain polymer containing oxygen groups and Pb in the perovskite material are used to form a perovskite single crystal thin film array. 2+ The Lewis acid-base interaction of ions improves the explosive nucleation problem in the process of growing perovskite single crystals by the spatial confinement method. While interacting with perovskite, the long polymer chain also plays a certain steric hindrance role in the crystal growth space, regulating the thermodynamic motion process of ions in the solution and promoting the large-scale growth of crystals. At the same time, the cover used in the spatial confinement method introduces a photolithography process, which can prepare a periodic groove surface with adjustable size, thereby successfully realizing a perovskite single crystal thin film array with adjustable thickness and controllable size, solving the problem of difficulty in balancing the thickness and lateral size of perovskite single crystal thin film, and providing an opportunity to explore the miniaturized integrated application of perovskite single crystal thin film devices.

[0005] To achieve the above object, the present invention provides a method for polymer-assisted preparation of perovskite single crystal thin film arrays, comprising the following steps:

[0006] The photolithography process is used to prepare periodic grooves with adjustable sizes on the silicon wafer cover. The perovskite precursor solution with oxygen-containing polymer additives is dripped between the cover and the substrate. The cover and the substrate are placed in a self-made fixture and tightened with screws to form a confined space. The oxygen-containing polymer regulates the nucleation and growth of the perovskite single crystal, and the size-controllable arrayed perovskite single crystal film is obtained by the spatial confinement method.

[0007] The specific preparation process of the perovskite precursor solution is as follows:

[0008] (a) dissolving perovskite powder in a polar solvent to prepare a growth solution;

[0009] (b) adding an oxygen-containing group polymer to the growth solution;

[0010] (c) stirring the mixed solution of step (b) and filtering.

[0011] Preferably, the molecular formula of the perovskite is A 1 BX 3 or (A 2 ) 2 (A 1 ) n-1 B n X 3n+1 , where A 1 for CH(NH 3 ) 2 + , CH 3NH 3 + , Cs + One of the 2 CH 3 (CH 2 ) 3 NH 3 + , CH 3 CH 2 NH 3 + , C 6 H 5 CH 2 CH 2 NH 3 + NH 3 C 4 H 8 NH 3 2+ One of the following; B is Pb 2+ ; X is Cl - Br - ,I - One of the following; the concentration of the perovskite solution is 0.5-1.5 mol / L.

[0012] Preferably, the polar solvent is a mixed solution of one or more of γ-butyrolactone, N,N-dimethylformamide and dimethyl sulfoxide.

[0013] Preferably, the polymer is an oxygen-containing functional group polymer, not limited to one of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyacrylic acid, sodium polyacrylate, and polymethyl methacrylate; the average molecular weight Mw of the polymer is 10,000-1.3 million, and the mass fraction ratio of the polymer addition amount to the perovskite powder is 0.5-10wt%.

[0014] Preferably, the mixed solution is stirred at a temperature of 25-50° C. until it becomes clear, and filtered using a filter with a pore size of 0.22 μm.

[0015] Preferably, the cover plate is a silicon wafer containing an oxide layer, and a periodic groove array is introduced on its surface by means of a traditional photolithography process, wherein the size of the square groove is Lμm×Lμm, L=20, 50, 100, 200, and the groove depth is Hnm, H=20, 50, 100, 200. The cover plate is hydrophobicized by OTS before use, and the substrate is a substrate with a flat surface that will not be corroded by the perovskite solution, and is not limited to silicon wafers, conductive glass, and ordinary glass.

[0016] Preferably, the cover plate and the substrate are stacked in an offset manner, 0.2-1.4 μL of the filtered perovskite mixed solution is dropped on the substrate, the perovskite mixed solution is introduced into the confined space by capillary action, and is placed in a homemade fixture and pressed tightly.

[0017] Preferably, the growth temperature range of the perovskite single crystal is 60-110° C., and the growth time is 24-72 hours.

[0018] The advantages and positive effects of the method for polymer-assisted preparation of perovskite single crystal thin film arrays described in the present invention are:

[0019] 1. The present invention utilizes oxygen-containing group polymers to effectively reduce the nucleation density of the crystal growth process and slow down the grain growth. At the same time, the long-chain repetitive oxygen-containing groups of the polymer anchor the lead ions in the crystal growth space, which can regulate the thermodynamic movement process of ions in the solution and promote the large-size growth of the crystal, thereby obtaining high-quality single crystals.

[0020] 2. The long-range ordered long-chain polymer of the present invention has a highly cross-linked structure and a large number of repeated oxygen-containing group units, which can be effectively paired with lead ions. Combined with the arrayed geometric confined space constructed by the photolithography process, it is possible to obtain an arrayed perovskite single crystal film with controllable size and adjustable thickness.

[0021] 3. The present invention has high utilization rate of raw materials, and the dosage used is slightly upgraded, which greatly reduces the cost. The growth process is easy to operate and has good repeatability. It has great application value in the growth of arrayed perovskite single crystal thin films.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A growth roadmap for the polymer-assisted preparation of size-controlled perovskite single crystal thin film arrays of the present invention;

[0024] Figure 2 (PEA) regulated by the PVP polymer additive of the present invention 2 PbI 4 Morphological characterization of perovskite single crystal array film, where (a) is an optical microscope photo and (b) is an AFM image;

[0025] Figure 3 (PEA) regulated by the PVP polymer additive of the present invention 2 PbI 4 TEM images of perovskite crystals, where (a) is (PEA) without PVP polymer additive 2 PbI 4TEM image of perovskite crystal, (b) is the HRTEM image of the perovskite crystal in the dashed box in (a), and (c) is the (PEA) image regulated by PVP polymer additive 2 PbI 4 TEM image of perovskite crystal, (d) is the HRTEM image of the perovskite crystal in the dashed box of (c);

[0026] Figure 4 (PEA) regulated by the PVP polymer additive of the present invention 2 PbI 4 Characterization of the crystalline quality of perovskite single crystals, where (a) is the XRD spectrum, (b) is the half-peak width of the (001) peak, (c) is the PL spectrum, and (d) is the TRPL spectrum;

[0027] Figure 5 (PEA) regulated by the PVP polymer additive of the present invention 2 PbI 4 FTIR spectrum of perovskite crystals;

[0028] Figure 6 is (BA) regulated by the PVP polymer additive of the present invention 2 (MA) 2 Pb 3 Br 10 Characterization of the crystalline quality of perovskite crystals, where (a) is the XRD pattern and (b) is the PL spectrum. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0030] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0031] A method for polymer-assisted preparation of a perovskite single crystal thin film array comprises the following steps:

[0032] The photolithography process is used to prepare periodic grooves with adjustable sizes on the silicon wafer cover. The perovskite precursor solution with oxygen-containing polymer additives is dripped between the cover and the substrate, and the cover and the substrate are placed in a homemade fixture and tightened with screws to form a confined space. The oxygen-containing polymer regulates the nucleation and growth of the perovskite single crystal. After the solution in the space confinement method slowly evaporates, a size-controllable arrayed perovskite single crystal film is obtained; the specific preparation process of the perovskite precursor solution is as follows:

[0033] (a) dissolving perovskite powder in a polar solvent to prepare a growth solution;

[0034] (b) adding an oxygen-containing group polymer to the growth solution;

[0035] (c) stirring the mixed solution of step (b) and filtering.

[0036] The molecular formula of perovskite is A 1 BX 3 or (A 2 ) 2 (A 1 ) n-1 B n X 3n+1 , where A 1 For FA + (CH(NH 3 ) 2 + )、MA + (CH 3 NH 3 + ), Cs + One of the 2 for BA + (CH 3 (CH 2 ) 3 NH 3 + ), EA + (CH 3 CH 2 NH 3 + )、PEA + (C 6 H 5 CH 2 CH 2 NH 3 + )、BDA 2+ (NH 3 C 4 H 8 NH 3 2+ ); B is Pb 2+ ; X is Cl - Br - ,I - One of the above; the concentration of the perovskite solution is 0.5-1.5 mol / L.

[0037] The polar solvent is a mixed solution of one or more of γ-butyrolactone (γ-GBL), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0038] The polymer is an oxygen-containing functional group polymer, not limited to one of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polypropylene glycol (PPG), polyacrylic acid (PAA), sodium polyacrylate (PAA-Na), and polymethyl methacrylate (PMMA); the average molecular weight of the polymer is M w The mass fraction ratio of the polymer addition amount to the perovskite powder is 0.5-10wt%.

[0039] The perovskite mixed solution was stirred at 25-50°C until it became clear and filtered with a filter with a pore size of 0.22 μm.

[0040] The upper cover plate used in the spatial confinement method has a periodic groove array introduced on its surface by means of a traditional photolithography process. The size of the square groove is Lμm×Lμm (L=20, 50, 100, 200) and the groove depth is Hnm (H=20, 50, 100, 200). The upper cover plate is treated with OTS for hydrophobicity before use. OTS treatment is to modify the substrate through a silanization reaction with octadecyltrichlorosilane (OTS) to reduce the surface energy and achieve the effect of hydrophobic treatment.

[0041] The upper cover plate and the lower substrate of the spatial confinement method are stacked in an offset manner, and 0.2-1.4 μL of the filtered perovskite mixed solution is dropped on the lower substrate. The perovskite mixed solution is introduced into the confined space by capillary action and placed in a fixture for compaction.

[0042] The growth temperature range of perovskite single crystal is 60-110°C and the growth time is 24-72 hours.

[0043] The spatial confinement method and the photolithography process belong to the prior art.

[0044] Example 1

[0045] A polymer-assisted preparation of perovskite (PEA) 2 PbI 4 The method of single crystal thin film array comprises the following steps:

[0046] (1) A periodic groove array is introduced on the surface of the upper cover plate of the spatial confinement method using a conventional photolithography process, wherein the size of the square groove is 100 μm × 100 μm and the depth of the groove is 100 nm.

[0047] (2) The cover plate and substrate of the spatial confinement method improved by the photolithography process were ultrasonically treated with deionized water, acetone, and ethanol for 30 minutes each, blown dry with nitrogen, and then placed in an oven to dry for 12 hours.

[0048] (3) The dried cover plate was placed in a vacuum oven and treated with OTS for 6 hours. After being taken out, it was ultrasonically treated with deionized water, acetone, and ethanol for 30 minutes each, dried with nitrogen, and then placed in an oven to dry for 12 hours.

[0049] (4) Weigh PEAI and PbI according to the stoichiometric ratio of 2:1 2 Powder, 1mL GBL solvent was used to dissolve the perovskite powder to prepare a 1mol / L perovskite solution, and 4wt% PVP polymer (M w =1.3 million), the mixed solution was stirred at 50°C for 12 h until it became clear and filtered through a 0.22 μm pore size polytetrafluoroethylene filter.

[0050] (5) The upper cover plate and the lower substrate are stacked in an offset manner, and 0.6 μL of the filtered perovskite mixed solution is dropped on the substrate. The perovskite mixed solution is introduced into the confined space by capillary action and placed in a homemade fixture for compaction.

[0051] (6) The homemade fixture was placed on a hot stage. The single crystal growth temperature range was 110°C and the growth time was 72 h.

[0052] After growth (PEA) 2 PbI 4 Optical microscope photos and SEM images of single crystal thin film arrays, such as Figure 2 As shown in (a), the optical microscope photo shows that the single crystal thin film array prepared under PVP-assisted regulation has excellent continuity. And the SEM image shows that the prepared single crystal array has a good morphology. PVP-(PEA) 2 PbI 4 AFM images of single crystal thin films (such as Figure 2 (b) shows that the surface roughness of the single crystal regulated by PVP is only 0.37nm, indicating that the single crystal has atomic-level surface flatness. TEM image of perovskite crystal regulated by PVP polymer additive (as shown in Figure 3 The results show that after adding PVP, the crystal size is larger and the nucleation density is effectively suppressed, indicating that PVP can effectively slow down the crystallization rate of perovskite and promote the growth of large-sized perovskite crystals. Original (PEA) 2 PbI 4 Single crystal and PVP-(PEA) 2 PbI 4 The XRD patterns and PL and TRPL spectra of the single crystal are shown in Figure 4 As shown in (a), (b), (c), and (d). PVP-(PEA) 2 PbI 4The narrower half-peak width, stronger PL peak position and longer carrier lifetime of the single crystal (001) plane indicate that the polymer-assisted preparation (PEA) 2 PbI 4 Single crystal has better crystal quality. Original PVP and PVP-(PEA) 2 PbI 4 Fourier transform infrared spectroscopy of powders (e.g. Figure 5 As shown in Figure 2, compared with pure PVP polymer at 1677.94 cm -1 C=O bond vibration at PVP-(PEA) 2 PbI 4 The C=O bond vibration peak shifted to 1643.92 cm -1 This indicates that the O of the C=O group of the PVP polymer provides a lone pair of electrons to bind to the Pb 2+ Pairing occurs to form a macromolecular intermediate phase, which slows down the crystallization rate of perovskite and thus improves the crystallization quality of perovskite single crystals.

[0053] Example 2

[0054] 2D Perovskite (BA) 2 (MA) 2 Pb 3 Br 10 The method for preparing a single crystal thin film array specifically comprises the following steps:

[0055] (1) A periodic groove array is introduced on the surface of the upper cover plate of the spatial confinement method using a conventional photolithography process. The size of the square groove is 100 μm × 100 μm and the depth of the groove is 50 nm.

[0056] (2) The cover plate and substrate of the spatial confinement method improved by the photolithography process were ultrasonically treated with deionized water, acetone, and ethanol for 30 minutes each, blown dry with nitrogen, and then placed in an oven to dry for 12 hours.

[0057] (3) The dried cover plate and substrate were placed in a vacuum oven and treated with OTS for 6 hours. After being taken out, they were ultrasonically treated with deionized water, acetone, and ethanol for 30 minutes each, dried with nitrogen, and then placed in an oven to dry for 12 hours.

[0058] (4) Weigh BABr, MABr and PbBr according to the stoichiometric ratio of 2:2:3 2 Powder, use 1 mL DMF solvent to dissolve the perovskite powder to prepare a 0.5 mol / L perovskite solution, and add 5 wt% PVP polymer (Mw = 58,000) thereto, heat and stir the mixed solution at room temperature for 12 h until it is clear and filter it with a polytetrafluoroethylene filter with a pore size of 0.22 μm.

[0059] (5) The upper cover plate and the lower substrate are stacked in an offset manner, 1.2 μL of the filtered perovskite mixed solution is dropped on the substrate, the perovskite mixed solution is introduced into the confined space by capillary action, and then placed in a homemade fixture and pressed tightly.

[0060] (6) The fixture is placed on a hot stage, the single crystal growth temperature range is 80°C, and the growth time is 48 hours. Based on the above Example 2, the grown (BA) 2 (MA) 2 Pb 3 Br 10 The XRD patterns and PL spectra of the single crystal thin film arrays are shown in Figure 6 Middle a, Figure 6 As shown in b, it can be seen that (BA) prepared with the assistance of polymer 2 (MA) 2 Pb 3 Br 10 The single crystal arrays also have good crystalline quality.

[0061] Therefore, the present invention adopts the above-mentioned polymer-assisted method for preparing perovskite single crystal thin film arrays, and develops a universal method for long-chain polymers to be used in the growth of size-controllable perovskite single crystal thin film arrays by combining the spatial confinement method improved by photolithography process and polymer additive-assisted crystallization engineering. 2+ The Lewis acid-base interaction of ions improves the explosive nucleation problem in the process of growing perovskite single crystals by the spatial confinement method. While interacting with perovskite, the long polymer chain also plays a certain steric hindrance role in the crystal growth space, regulating the thermodynamic motion process of ions in the solution and promoting the large-scale growth of crystals, thereby successfully realizing a thickness-adjustable and size-controllable perovskite single crystal film array, solving the problem of balancing the thickness and lateral size of perovskite single crystal films, and providing an opportunity to explore the miniaturized integrated application of perovskite single crystal thin film devices.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for polymer-assisted preparation of perovskite single crystal thin film arrays, characterized in that: The steps include: The photolithography process is used to prepare periodic grooves with adjustable sizes on the silicon wafer cover. The perovskite precursor solution with oxygen-containing polymer additives is dripped between the cover and the substrate. The cover and the substrate are placed in a self-made fixture and tightened with screws to form a confined space. The oxygen-containing polymer regulates the nucleation and growth of the perovskite single crystal, and the size-controllable arrayed perovskite single crystal film is obtained by the spatial confinement method. The specific preparation process of the perovskite precursor solution is as follows: (a) dissolving perovskite powder in a polar solvent to prepare a growth solution; (b) adding an oxygen-containing group polymer to the growth solution; (c) stirring the mixed solution of step (b) and filtering.

2. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The molecular formula of the perovskite is A1BX3 or (A2)2(A1) n-1 B n X 3n+1 , where A1 is CH(NH3)2 + 、CH3NH3 + , Cs + One of the following; A2 is CH3(CH2)3NH3 + 、CH3CH2NH3 + 、C6H5CH2CH2NH3 + 、NH3C4H8NH3 2+ One of the following; B is Pb 2+ ; X is Cl-, Br - , I-; the concentration of the perovskite solution is 0.5-1.5 mol / L.

3. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The polar solvent is a mixed solution of one or more of gamma-butyrolactone, N,N-dimethylformamide and dimethyl sulfoxide.

4. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The polymer is an oxygen-containing functional group polymer, and is not limited to one of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyacrylic acid, sodium polyacrylate, and polymethyl methacrylate; the average molecular weight of the polymer is w The mass fraction ratio of the polymer addition amount to the perovskite powder is 0.5-10wt%.

5. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The mixed solution was stirred at 25-50° C. until it became clear, and then filtered using a filter with a pore size of 0.22 μm.

6. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The cover plate is a silicon wafer containing an oxide layer, and a periodic groove array is introduced on its surface with the help of traditional photolithography technology. The size of the square groove is Lμm×Lμm, L=20, 50, 100, 200, and the groove depth is Hnm, H=20, 50, 100, 200. The cover plate is hydrophobic treated with OTS before use. The substrate is a substrate with a flat surface that will not be corroded by the perovskite solution, and is not limited to silicon wafers, conductive glass, and ordinary glass.

7. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The cover plate and substrate are stacked in an offset manner, and 0.2-1.4 μL of the filtered perovskite mixed solution is dropped on the substrate. The perovskite mixed solution is introduced into the confined space by capillary action and placed in a homemade fixture for compaction.

8. The method for polymer-assisted preparation of perovskite single crystal thin film array according to claim 1, characterized in that: The growth temperature range of perovskite single crystal is 60-110°C and the growth time is 24-72 hours.

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