Perovskite ink based on 3D printing and preparation method and application thereof

Abstract

The application discloses a kind of perovskite ink based on 3D printing and its preparation method and application, comprising, ammonium salt and lead iodide are dissolved in mixed organic solvent, after stirring, perovskite precursor liquid is obtained;Additive is added to perovskite precursor liquid, and perovskite ink is obtained after heating and stirring;Wherein, the ammonium salt includes one or two of methyl iodide ammonium and phenethyl amine iodide.This application further improves the crystallization quality and environmental stability of perovskite material by synergistically utilizing the defect passivation and in-situ encapsulation effect of PVP (polyvinylpyrrolidone), so that the obtained perovskite ink can be innovatively applied to 3D printing technology for the first time to prepare a perovskite direct X-ray detector, solves the practical situation that the viscosity of traditional perovskite solution is low and difficult to 3D print, and provides a new material preparation technology for the development of high-sensitivity, high-resolution perovskite direct X-ray imaging detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite-based direct X-ray detectors, and particularly relates to a 3D printing-based perovskite ink as well as a preparation method and application thereof. BACKGROUND

[0002] A direct X-ray detector is a device capable of converting X-ray photons directly into electrical signals, and has advantages of high spatial resolution and simple structure, and is widely applied in scientific research, medical imaging, security inspection and industrial non-destructive testing. Commercially used direct X-ray detectors are mainly based on amorphous selenium. Unfortunately, due to the low charge transport characteristics, weak X-ray absorption capacity and poor stability of amorphous selenium, the amorphous selenium X-ray detector has prominent bottlenecks such as dependence on ultra-high voltage, low sensitivity and application limited to soft X-ray detection imaging field. In recent years, metal halide perovskite (referred to as perovskite) has become the most promising star material in the field of X-ray detection due to its large X-ray attenuation coefficient, high carrier mobility-lifetime product and solution processability. Previous studies have shown that the sensitivity of the perovskite X-ray detector is at least two orders of magnitude higher than that of the traditional amorphous selenium X-ray detector, and its detection limit is only one hundredth of that of the amorphous selenium detector. At the same time, its solution processability gives the perovskite X-ray detector a greater cost advantage than existing commercial detectors. These all confirm the broad development prospects and great application potential of perovskite materials in the field of X-ray detection imaging.

[0003] It is worth noting that the thickness required for perovskite to effectively absorb X-rays is as high as hundreds of microns, while the most mature spin coating process of perovskite at present can only achieve a thickness of hundreds of nanometers per spin, and the solution for adjacent two spin coatings is required to have orthogonal polarity, but this is contrary to the dissolution rule that perovskite precursor salt can only be dissolved in aprotic polar solvents, so the traditional spin coating method is not applicable. At present, there are mainly three methods for preparing perovskite X-ray detectors by solution method:

[0004] (1) Doctor blade coating method: the perovskite precursor solution is coated on the substrate by using a blade, and then the solvent is evaporated at a certain temperature to form a perovskite film. This method has high raw material utilization rate, and at the same time, the thickness of the perovskite film can be controlled within a certain range by the concentration of the perovskite precursor and the distance between the blade and the substrate.

[0005] (2) Ultrasonic spraying: Ultrasonic technology is used to atomize the precursor solution, and the perovskite spray is shaped by an inert carrier gas, and uniformly deposited on a high-temperature substrate through a nozzle. This method effectively breaks through the orthogonal solvent polarity limitation faced by the traditional solution method for layer-by-layer preparation of perovskite thick films by finely controlling the perovskite nucleation-crystallization and redissolution process. At the same time, the thickness of the perovskite film can be controlled by controlling the number of cyclic spraying cycles.

[0006] (3) Single crystal growth method: Perovskite single crystals are prepared by dissolving the perovskite precursor salt in a specific solvent and controlling the supersaturation and number of nucleation centers of the perovskite solution.

[0007] However, the above-mentioned perovskite direct X-ray detector preparation method has the following disadvantages:

[0008] In terms of preparation methods, the thickness of the perovskite film formed by the doctor blade coating method is seriously dependent on the concentration of its precursor solution. At the same time, due to the poor controllability of the perovskite film formation process and the orthogonal solution polarity limitation faced by layer-by-layer preparation, it is difficult to achieve the preparation of high-quality perovskite thick films; the ultrasonic spraying method has low material utilization, is time-consuming, and the atomized solvent is prone to environmental pollution; the single crystal growth method is time-consuming, the size of the single crystal is difficult to control (the thickness is too large, the area is too small, the geometry is irregular), and subsequent polishing, cutting and other tedious processes are required, making it difficult to achieve large-scale practical application

[0009] In addition, none of the above methods have achieved the preparation of patterned perovskite detectors required for high-resolution X-ray imaging. In the future, achieving this goal will also require the use of auxiliary means such as masks.

[0010] To address the challenges of preparing thick perovskite films for X-ray detection and imaging, this patent proposes a low-cost, high-raw material utilization perovskite 3D printing technology. By adjusting the rheological properties of the perovskite printing ink, computer program control, and layer-by-layer printing, this method enables the preparation of thick perovskite films on various substrates, and is expected to enable the construction of patterned array structures. Summary of the Invention

[0011] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0012] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0013] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing perovskite ink based on 3D printing.

[0014] In order to solve the above technical problems, the present invention provides the following technical solution: ammonium salt and lead iodide are dissolved in a mixed organic solvent, and stirred to obtain a perovskite precursor solution;

[0015] Adding additives to the perovskite precursor solution, heating and stirring to obtain perovskite ink;

[0016] Wherein, the ammonium salt includes one or both of methylammonium iodide and phenethylammonium iodide.

[0017] As a preferred embodiment of the 3D printing-based perovskite ink of the present invention, the molar ratio of the ammonium salt to the lead iodide is 1:1-2.

[0018] As a preferred solution of the 3D printing-based perovskite ink described in the present invention, the mixed organic solvent includes any two of dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0019] As a preferred solution of the 3D printing-based perovskite ink described in the present invention, the volume ratio of any two solvents in the mixed organic solvent is 1:1.

[0020] As a preferred solution of the 3D printing-based perovskite ink described in the present invention, the temperature of the heating and stirring is 60°C to 90°C.

[0021] As a preferred solution of the 3D printing-based perovskite ink described in the present invention, the heating and stirring time is 6 to 8 hours.

[0022] As a preferred solution of the 3D printing-based perovskite ink described in the present invention, the additive includes one or two of PVP and PEO.

[0023] As a preferred embodiment of the 3D printing-based perovskite ink of the present invention, the mass ratio of the additive to the perovskite precursor solution is 1:25.

[0024] Another object of the present invention is to overcome the deficiencies in the prior art and provide a perovskite ink based on 3D printing.

[0025] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a 3D-printed perovskite ink in the preparation of a perovskite-based X-ray detector, specifically: using a 3D printer dispenser to print the perovskite ink on a substrate to obtain a perovskite thick film, and depositing a carbon electrode on the perovskite thick film to obtain a perovskite-based X-ray detector.

[0026] Beneficial effects of the present invention:

[0027] The present invention effectively regulates the rheological properties of perovskite ink by adding PVP (polyvinyl pyrrolidone), synergistically utilizes the defect passivation and in-situ encapsulation effects of PVP (polyvinyl pyrrolidone), and further improves the crystallization quality and environmental stability of the perovskite material. The obtained perovskite ink can be innovatively applied to 3D printing technology for the first time to prepare a perovskite direct X-ray detector, which solves the problem that traditional perovskite solutions have low viscosity and are difficult to 3D print. Through layer-by-layer printing, the thickness of the perovskite layer is effectively controlled to 60μm, and the raw material utilization rate is close to 100%, providing a new material preparation technology for the development of high-sensitivity, high-resolution perovskite direct X-ray imaging detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0029] Figure 1 Schematic diagram of the device for direct ink writing 3D printing according to the present invention.

[0030] Figure 2 It is a schematic structural diagram of the perovskite X-ray detector prepared by the present invention.

[0031] Figure 3 This is a schematic diagram of the preparation of perovskite materials based on the direct ink writing 3D printing method of the present invention, including printing a first layer of perovskite precursor solution (Figure i), annealing the first layer of perovskite precursor solution to form a perovskite film (Figure ii), printing a second layer of perovskite precursor solution on the first layer of perovskite film (Figure iii), and annealing the second layer of perovskite precursor solution to form a perovskite film (Figure iv).

[0032] Figure 4 This is a top view (Figure a) and a cross-sectional view (Figure b) of the perovskite thick film prepared in Example 1, taken using a scanning electron microscope.

[0033] Figure 5 is the photoresponse current of the X-ray detector prepared in Example 1 under different doses of X-rays.

[0034] Figure 6 The sensitivity of the X-ray detector prepared in Example 1 under different doses of X-rays.

[0035] Figure 7 This is a stability test of the X-ray detector prepared in Example 1 under different doses of X-rays.

[0036] Figure 8 These are optical images of the perovskite films prepared in Example 1 (Figure a) and Comparative Example 1 (Figure b).

[0037] Figure 9 These are the in-situ PL images of the perovskite thick film of Example 1 (Figure a) and Comparative Example 1 (Figure b). DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0041] Printing process:

[0042] 1) Place 1 ml of perovskite ink in a dispensing needle (needle inner diameter 0.21 mm) and fix the needle on the 3D printer dispenser; at the same time, place the glass substrate on a hot plate and heat it at a constant temperature of 90°C (e.g. Figure 1 a);

[0043] 2) Set up the 3D printing path program diagram, set the printing start point, printing spacing to 0.7mm, printing height (the vertical height of the dispensing needle from the heated substrate is about 2.5mm), adjust the pressure to 100KPa, and set the negative pressure to -1KPa (to prevent the precursor from dripping when the machine is not working). After all parameters are set, click Start Printing. The dispensing needle prints on the transparent conductive glass at a speed of 10mm / s according to the set program to obtain the first layer of liquid film;

[0044] 3) After the first layer of liquid film is printed, the liquid film is heated in situ on the substrate at 90°C for 5 minutes to evaporate the solvent. After the solvent is completely evaporated, the printing height is adjusted to 2.52mm, and the second layer is printed exactly according to the printing track of the first layer. After the solvent is completely evaporated, the printing height is adjusted to 2.54mm, and the third layer is printed exactly according to the printing track of the second layer.

[0045] 4) After printing, the conductive glass is transferred to another heating stage and heated at 120°C for one hour. The heating stage is then immediately lowered from 120°C to 30°C at a rate of 1°C / min to obtain a thick perovskite film.

[0046] The perovskites included in the present invention mainly include three-dimensional perovskites, two-dimensional perovskites and zero-dimensional perovskites. Among them, the chemical formula of three-dimensional perovskites is ABX3, A is cesium (Cs), MA, FA, etc., B is Pb, Sn, etc., and X is Cl, Br, I, etc.; the chemical formula of two-dimensional perovskites is A'2A n-1 Pb n X 3n+1 or A'A n-1 Pb n X 3n+1 , A' is CH3(CH2)3NH3(BA), C6H5CH2CH2NH3(PEA), 3HN-(CH2) n -NH3 (n = 2-4), B is Pb, Sn, etc., X is Cl, Br, I, etc.; the zero-dimensional perovskite is A3B2X9, A is cesium (Cs), MA, FA, etc., B is Bi, Ag, etc., X is Cl, Br, I, etc.; the additives are polymers such as PVP (polyvinyl pyrrolidone), ionic liquids such as MAAC, and other organic substances that can effectively increase the viscosity of perovskite ink.

[0047] The present invention uses SEM to characterize the morphology and thickness of the perovskite film, XRD to characterize the crystalline quality of the perovskite film, and Keithley Source Meter 2450 to characterize various basic parameters of the X-ray detector, such as dark current, X-ray current response characteristics, sensitivity, and irradiation stability under intermittent irradiation working conditions.

[0048] The 3D printer dispenser used in the present invention is: Japan Musashi coater 350pc.

[0049] The glass substrate used in the present invention is: FTO conductive glass is placed in a beaker of glass cleaner, deionized water, acetone, isopropyl alcohol, and anhydrous ethanol in sequence for ultrasonic cleaning, and then dried in an oven. The cleaned FTO glass is then placed in a plasma cleaner for 6 seconds to obtain a glass substrate.

[0050] Unless otherwise specified, the raw materials used in the present invention are commonly available in the market.

[0051] Example 1

[0052] This embodiment provides a method for preparing a perovskite-based direct X-ray detector using FTO conductive glass (1.5 cm×1.5 cm) as a substrate and direct ink writing 3D printing technology, specifically:

[0053] 1) dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) are mixed in a volume ratio of 1:1 to obtain a mixed organic solvent;

[0054] 2) dissolving methylammonium iodide (MAI) and lead iodide (PbI2) in a mixed organic solvent at a molar ratio of 1:1 and stirring for two hours to obtain a 2.5 mol / L MAPbI3 three-dimensional perovskite precursor solution;

[0055] 3) Mixing the MAPbI3 three-dimensional perovskite precursor solution and PVP in a mass ratio of 25:1, heating and stirring at 60°C for 6 hours to obtain MAPbI3@PVP perovskite ink;

[0056] 4) Printing MAPbI3@PVP perovskite ink on a glass substrate using a 3D printer dispenser to obtain a thick perovskite film;

[0057] 5) A carbon electrode is deposited on the perovskite thick film by blade coating to obtain a perovskite-based X-ray detector.

[0058] Example 2

[0059] The difference between this embodiment and embodiment 1 is that dimethyl sulfoxide (DMSO) in step 1) is replaced by N-methylpyrrolidone (NMP).

[0060] The rest of the preparation method is the same as that in Example 1 to obtain the perovskite-based X-ray detector of this embodiment.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 1 is that step 2) is adjusted as follows:

[0063] 2) Phenethylammonium iodide (PEAI) and lead iodide (PbI2) were dissolved in a mixed organic solvent at a molar ratio of 1:2 and stirred for two hours to obtain a PEA2PbI4 two-dimensional perovskite precursor solution with a concentration of 2.5 mol / L;

[0064] The rest of the preparation method is the same as that in Example 1 to obtain the perovskite-based X-ray detector of this embodiment.

[0065] Example 4

[0066] This embodiment differs from embodiment 1 in that PVP is replaced by polyethylene glycol (PEO).

[0067] The rest of the preparation method is the same as that in Example 1 to obtain the perovskite-based X-ray detector of this embodiment.

[0068] The performance parameters of the perovskite-based X-ray detector prepared in Example 1 were tested, and the results are shown in the attached figure. Figure 5~Attachment Figure 7 As shown in the figure, it can be seen that the perovskite-based X-ray detector has a good linear response at different X-ray dose rates. At a bias voltage of 2V, 1950Gy air / s dose rate, the dark current density is 4×10 -7 A cm -2 , the photocurrent density is 1.5×10 -5 A cm -2 , and its light-to-dark ratio is 37.5, which is also quite outstanding among the X-ray detectors currently prepared by other processes. In addition, the perovskite-based X-ray detector does not have a baseline problem, indicating that we have effectively suppressed the baseline drift. At the same time, after multiple switches, the response of the perovskite-based X-ray detector prepared by the present invention does not change at all, indicating good stability.

[0069] In particular, the sensitivity of the X-ray detector prepared in Example 1 exceeds 7000 μCGy air - 1 cm -2 , which is 350 times more sensitive than the commercially available amorphous selenium X-ray detector. This is because the perovskite ink prepared by the present invention has good printability and can form Figure 8 The uniform and dense perovskite film in (a) and the addition of PVP can effectively inhibit the formation of intermediate phases when the perovskite crystallizes in the air, thereby extending the storage time of the perovskite liquid film in the air. This is because PVP enhances stability, promotes the improvement of crystallization quality, and forms a perovskite polycrystalline film with good photoelectric properties. 3D printing technology has better precision and can be precisely combined with TFT thin-film transistor arrays, which is more in line with the commercial dark current requirements of TFT thin-film transistors, which is difficult to achieve with other technologies.

[0070] Comparative Example 1

[0071] Comparative Example 1 is based on Example 1. The difference between Comparative Example 1 and Example 1 is that PVP is not added, and the rest of the preparation methods are the same as those of Example 1.

[0072] When printing the perovskite thick film, a coffee ring effect occurs. This is because the low viscosity of the ink causes an imbalance in the evaporation rate of the printed ink edge and center. When printing and forming, the perovskite thick film is not distributed according to the specified pattern. This is because the ink with lower viscosity has stronger fluidity, which reduces the shaping effect.

[0073] According to the attached Figure 8It can be seen that the perovskite ink prepared in Example 1 has a smooth surface after film formation, while the perovskite ink prepared in Comparative Example 1 cannot form a film, and the ink contains larger-sized crystals visible to the naked eye. This is because the evaporation rates of the printed ink edge and center are unbalanced, thereby reducing the shaping effect. Ink with a certain viscosity can effectively inhibit the formation of the coffee ring effect and can be coated according to the designed pattern.

[0074] According to the attached Figure 9 It can be seen that the PL peak remains stable after adding PVP, while the PL peak of the film without PVP decreases rapidly after crystallization is completed. This is because PVP enhances the stability of the perovskite film, promotes the improvement of crystallization quality, and forms a perovskite polycrystalline film with good photoelectric properties. This is because PVP is a non-ionic high molecular long-chain polymer. As an additive to the perovskite solution, it can effectively inhibit the generation of intermediate phases during the crystallization of perovskite in the air and can prolong the storage time of the perovskite liquid film in the air.

[0075] Comparative Example 2

[0076] Comparative Example 2 is based on Example 1. The difference between Comparative Example 2 and Example 1 is that the mass ratio of MAPbI3 three-dimensional perovskite precursor solution and PVP in step 3) is adjusted to 10:1.

[0077] During the printing process, pinholes clog, preventing the formation of thick perovskite films. The inventors also adjusted various raw material formulations in their research, but found that none of the resulting perovskite inks could be successfully printed. This is because the presence of a large amount of long-chain insulating polymers in the ink severely affects the carrier transport properties of the perovskite film, making it impossible to produce a perovskite-based X-ray detector.

[0078] In summary, only under the conditions of Example 1, the MAPbI3 three-dimensional perovskite precursor solution and PVP are mixed in a mass ratio of 25:1, and heated and stirred at 60°C for 6 hours to obtain the MAPbI3@PVP perovskite ink, which has the best shaping effect and the most stable film formation, and the sensitivity and stability of the prepared perovskite-based X-ray detector are the best. This is because under this ratio and process conditions, the prepared perovskite ink can be applied to 3D printing technology to prepare a perovskite direct X-ray detector, and 3D printing technology has better precision and can be precisely combined with TFT thin-film transistor arrays, so that the sensitivity of the X-ray detector exceeds 7000μCGy air - 1 cm -2 , which is 350 times more sensitive than the commercially used amorphous selenium X-ray detectors.

[0079] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing perovskite ink based on 3D printing, characterized in that: include, The ammonium salt and lead iodide are dissolved in a mixed organic solvent and stirred to obtain a perovskite precursor solution; Adding additives to the perovskite precursor solution, heating and stirring to obtain perovskite ink; Wherein, the ammonium salt includes one or both of methylammonium iodide and phenethylammonium iodide; The additives include one or two of PVP and PEO; The mass ratio of the additive to the perovskite precursor solution is 1:25; The concentration of the perovskite precursor solution is 2.5 mol / L.

2. The method for preparing perovskite ink based on 3D printing according to claim 1, wherein: The molar ratio of the ammonium salt to the lead iodide is 1:1-2.

3. The method for preparing perovskite ink based on 3D printing according to claim 1, wherein: The mixed organic solvent includes any two of dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

4. The method for preparing perovskite ink based on 3D printing according to claim 1, wherein: The volume ratio of any two solvents in the mixed organic solvent is 1:

1.

5. The method for preparing perovskite ink based on 3D printing according to claim 1, wherein: The temperature of the heating and stirring is 60°C to 90°C.

6. The method for preparing perovskite ink based on 3D printing according to claim 5, characterized in that: The heating and stirring time is 6 to 8 hours.

7. Perovskite ink prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the perovskite ink according to claim 7 in the preparation of a perovskite-based X-ray detector, characterized in that :Use a 3D printer dispenser to print perovskite ink on a substrate to obtain a perovskite thick film, and deposit a carbon electrode on the perovskite thick film to obtain a perovskite-based X-ray detector.

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