Highly stable full-spectrum perovskite nanocrystal and preparation method and device thereof

Abstract

The application relates to a high-stability full-spectrum perovskite nanocrystal and a preparation method and device thereof, the surface of nanometer titanium dioxide is modified by lead halide, the perovskite nanocrystal generated by the reaction of the lead halide and a cesium precursor is combined with the nanometer titanium dioxide in situ in a synthesis process, and the nanometer titanium dioxide coats the perovskite nanocrystal; the lead halide is selected from one or more of lead chloride, lead bromide and lead iodide, the molar ratio of the lead halide to the nanometer titanium dioxide is 1:(1-4), and the molar ratio of cesium to lead in the cesium precursor and the lead halide is 1:(2-7). Compared with the prior art, the application enhances the light emission intensity, water stability and thermal stability of the perovskite nanocrystal, and can realize full-spectrum regulation and continuous controllable preparation.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent material preparation technology, and relates to a highly stable full-spectrum perovskite nanocrystal and its preparation method and apparatus. Background Technology

[0002] All-inorganic lead halide perovskite nanocrystals (CsPbX3 NCs, X = Cl, Br, I) are widely used in displays, solar cells, and light-emitting diodes (LEDs) due to their unique luminescent properties, such as narrow full width at half maximum (FWHM), high photoluminescence quantum yield, tunable band gap, and high carrier mobility. However, the large-scale preparation and environmental stability issues of perovskite nanocrystals significantly hinder their practical application in the optoelectronic field. Traditional methods for preparing perovskite nanocrystals are based on batch processes using artificial flasks and beakers. These methods not only struggle to achieve rapid control of parameters such as reaction temperature and time but also suffer from uncontrollable and non-reproducible heat and mass transfer rates, limiting their reproducibility, homogeneous mixing, and large-scale, high-throughput preparation. This can lead to uneven distribution and poor reproducibility of the synthesized perovskite nanocrystal particles.

[0003] Inorganic lead halide perovskite nanocrystals exhibit extremely poor environmental stability, especially purple CsPbCl3 and red CsPbI3 nanocrystals, which are highly sensitive to environmental factors such as moisture, oxygen, radiation, and high temperatures, easily undergoing phase transitions, degradation, and aggregation, leading to fluorescence quenching. To improve the environmental stability of perovskite nanocrystals, composite with inorganic materials is a common approach. Existing research commonly utilizes inorganic materials such as alumina (Al2O3), silicon dioxide (SiO2), and calcium fluoride (CaF2), all of which possess high transparency, strong thermal stability, and chemical stability. Coating perovskite nanocrystals can, to some extent, isolate them from the influence of environmental factors, but it reduces the luminescence intensity of the perovskite nanocrystals. Therefore, a method is needed that can continuously and controllably prepare perovskite nanocrystals while simultaneously enhancing their stability.

[0004] Patent CN116590011A discloses a microfluidic-based method for preparing perovskite quantum dots. The microfluidic reactor used includes: an injection pump, a syringe, a polytetrafluoroethylene (PTFE) tube with an inner diameter of 0.5 mm, and a four-way connector, and a heating aluminum plate. The dotted lines represent the PTFE tubes, and A, B, and C are the PTFE tubes connected to the flow phases A, B, and C, respectively. The heating aluminum plate is separated by dotted lines, with the left side of the dotted lines representing the precursor preheating zone and the right side representing the quantum dot preparation zone. The heating aluminum plate has grooves for placing the PTFE tubes. The length of the PTFE tubes placed in the quantum dot preparation zone is adjustable, and the preparation time is controlled by adjusting the length of the PTFE tubes placed in the quantum dot preparation zone.

[0005] However, the patent combines an injection pump, a polytetrafluoroethylene tube, a four-way connector, and a heating aluminum plate to construct a fluid reaction device. The equipment assembly is complex, and it is difficult to tightly fit and fix the polytetrafluoroethylene tube to the heating aluminum plate. The reaction zone is not completely enclosed in a high-temperature environment.

[0006] The inner diameter of the PTFE tube is 0.5 mm, which means the cross-sectional area of ​​the reaction tube is 0.19625 mm². 2 The large cross-sectional area of ​​the flow channel results in a slow mixing rate of reactants, which is not conducive to the reaction.

[0007] The reaction apparatus is a three-phase flow, with phase A being a cesium precursor, phase B being a lead halide precursor, and phase C being fluorinated oil. The fluorinated oil acts as a carrier to divide the reaction phase into multiple small droplets, resulting in a discontinuous flow and a discontinuous reaction zone.

[0008] The device produces perovskite quantum dots, rather than perovskite nanocrystals.

[0009] Patent CN110607172A discloses a method for preparing perovskite / titanium dioxide composite nanocrystals, comprising: mixing cesium carbonate, octadecene solution, and oleic acid, and reacting to obtain a cesium oleate precursor solution; mixing lead halide, octadecene solution, oleic acid, and oleylamine, and reacting the resulting mixed solution rapidly with the cesium oleate precursor solution to obtain a perovskite quantum dot solution; purifying the perovskite quantum dot solution with toluene to obtain a perovskite toluene solution; and mixing the perovskite toluene solution with titanium dioxide nanotubes to obtain perovskite / titanium dioxide composite nanocrystals. However, the titanium dioxide used in this patent is in the form of titanium dioxide nanotubes. The composite method of perovskite quantum dots and titanium dioxide nanotubes is to first synthesize perovskite quantum dots and purify them with toluene, and then directly mix the reacted perovskite quantum dots with titanium dioxide nanotubes. The combination method is that the perovskite quantum dots are inside the titanium dioxide nanotubes. After the perovskite quantum dots and titanium dioxide nanotubes are combined, since the perovskite quantum dots are synthesized first, their luminescence performance will not be enhanced by directly mixing with titanium dioxide nanotubes. Furthermore, the stability changes before and after the combination of perovskite quantum dots and titanium dioxide nanotubes have not been studied. Summary of the Invention

[0010] The purpose of this invention is to overcome at least one defect of the prior art and provide a highly stable full-spectrum perovskite nanocrystal and its preparation method and apparatus. This invention enhances the luminescence intensity, water stability and thermal stability of perovskite nanocrystals, and can achieve full-spectrum regulation and continuous controllable preparation.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] One of the technical solutions of the present invention is to provide a highly stable full-spectrum perovskite nanocrystal, wherein the surface of nano-titanium dioxide (TiO2) is fully modified with lead halide (PbX2), and the perovskite (CsPbX3) nanocrystal generated by the reaction of the lead halide with the cesium precursor is combined with the nano-titanium dioxide in situ during the synthesis process. The nano-titanium dioxide coats the perovskite nanocrystal, thereby modifying the surface defects of the perovskite nanocrystal.

[0013] The lead halide is selected from one or more of lead chloride (PbCl2), lead bromide (PbBr2), and lead iodide (PbI2), the molar ratio of the lead halide to nano titanium dioxide is 1:(1-4), and the molar ratio of cesium to lead in the cesium precursor and lead halide is 1:(2-7).

[0014] As a preferred technical solution, the molar ratio between the two halogens is (0-3):(0-3), but not both are 0.

[0015] Furthermore, the cesium source of the cesium precursor includes cesium carbonate (Cs2CO3) or cesium acetate (CsOAc).

[0016] One of the technical solutions of the present invention is to provide a method for preparing the aforementioned highly stable full-spectrum perovskite nanocrystals, the method comprising the following steps:

[0017] S1. Preparation of precursor solution: Cesium source, oleic acid (OA) and octadecene (ODE) are mixed in an inert gas atmosphere, and then heated and mixed. The cesium source and oleic acid react completely to obtain cesium oleate (Cs-Oleate) solution. Octadecene is added to the cesium oleate solution for dilution. The mixture is stirred in an inert gas atmosphere until the solution is clear and then used as the first precursor solution.

[0018] S2. Lead halide, nano titanium dioxide, oleic acid, oleylamine (OAm) and octadecene are mixed in an inert gas atmosphere. The surface of nano titanium dioxide is fully modified by lead halide to form lead halide / nano titanium dioxide (PbX2 / TiO2). The lead halide / nano titanium dioxide reacts completely with oleic acid and oleylamine to obtain a lead halide / nano titanium dioxide solution as the second precursor solution.

[0019] S3. The first precursor solution and the second precursor solution are transferred to the first syringe and the second syringe, respectively. The microfluidic chip is placed on the heating stage, and the injection pump drives the precursor solutions in the first syringe and the second syringe to flow uniformly and mix in the microfluidic channel to obtain highly stable full-spectrum perovskite (CsPbX3 / TiO2) nanocrystals.

[0020] As a preferred technical solution, the inert gas in steps S1 and S2 includes nitrogen or argon.

[0021] Furthermore, in step S1, the molar / volume ratio of cesium, oleic acid and octadecene in the cesium source is 1 mol:(0.4-0.6 L):(6-9 L).

[0022] Furthermore, in step S2, the molar / volume ratio of lead halide, nano titanium dioxide, oleic acid, oleylamine and octadecene is 1 mol:(1-4 mol):(1-3 L):(1-3 L):(20-40 L).

[0023] Furthermore, the mixing temperature in step S1 is 110-130℃, and the time is 1-1.5h;

[0024] The heating and mixing temperature is 140-160℃, and the time is 0.5-1h;

[0025] The dilution ratio is 15-25 times, and the mixing temperature during dilution is 110-130℃, with a time of 10-15 minutes.

[0026] Furthermore, the mixing temperature in step S2 is 110-130℃, and the time is 0.5-1h.

[0027] Furthermore, in step S3, the reaction time is determined by the flow rate of the mixed precursor in the reaction zone and the width, depth and flow channel length of the microfluidic channel in the reaction zone. The reaction time is 3-8 s, the reaction temperature is 140-180 ℃, and the flow rate is 300-800 μL / min.

[0028] As a preferred technical solution, after step S3, the product solution is centrifuged, the supernatant is discarded, and a highly stable full-spectrum perovskite nanocrystal precipitate is obtained. After centrifugation and washing with solvent, the highly stable full-spectrum perovskite nanocrystal precipitate is dispersed in a solvent for storage.

[0029] As a preferred technical solution, the centrifugation speed is 8000-12000 r / min and the time is 5-10 min.

[0030] As a preferred technical solution, the solvent includes n-hexane, cyclohexane, or toluene.

[0031] One of the technical solutions of the present invention is to provide a device for preparing highly stable full-spectrum perovskite nanocrystals. The perovskite nanocrystals are continuously and controllably prepared by the method described in the device. The device includes an injection pump, a first syringe, a second syringe, a microfluidic chip, a heating stage, and a collection device. The microfluidic chip includes an upper plate, a gasket, a lower plate, a first microfluidic channel, a second microfluidic channel, and a third microfluidic channel.

[0032] The lower plate is provided with a first microfluidic channel, a second microfluidic channel and a third microfluidic channel. The first microfluidic channel, the second microfluidic channel and the third microfluidic channel are connected in a T-shaped channel. The first syringe is connected to the first microfluidic channel, the second syringe is connected to the second microfluidic channel, and the third microfluidic channel is connected to the collecting device.

[0033] The first syringe and the second syringe are connected to an injection pump, which is used to push the first syringe and the second syringe. An upper plate is provided on the lower plate, which is sealed to the lower plate by a gasket. A heating platform is provided under the lower plate, which is used to heat the lower plate.

[0034] As a preferred technical solution, the first syringe is connected to the first microfluidic channel through a transparent polytetrafluoroethylene (PTFE) tube and a high-temperature resistant polypropylene (PP) inverted conical connector, the second syringe is connected to the second microfluidic channel through a transparent polytetrafluoroethylene tube and a high-temperature resistant polypropylene inverted conical connector, and the third microfluidic channel is connected to the collection device through a transparent polytetrafluoroethylene tube and a high-temperature resistant polypropylene inverted conical connector.

[0035] As a preferred technical solution, the collection device uses a 50mL centrifuge tube or a 100mL conical flask to receive the material synthesized in the third microfluidic pipeline.

[0036] As a preferred technical solution, both the first syringe and the second syringe are syringes that are compatible with the injection pump, with a specification of 10-50mL.

[0037] As a preferred technical solution, both the upper plate and the lower plate are made of aluminum or copper, and the length and width of the upper plate and the lower plate are (90-110)×(60-80)mm, and the thickness is 5-10mm. The gasket is made of fluororubber or nitrile rubber, and the thickness of the gasket is 1-4mm.

[0038] Furthermore, the width of each microfluidic channel is 0.4-0.6 mm, the depth is 0.2-0.4 mm, the flow channel length of the first microfluidic channel and the second microfluidic tube is 150-250 mm, the third microfluidic channel is the precursor mixing reaction zone, and the flow channel length of the third microfluidic channel is 500-600 mm.

[0039] As a preferred technical solution, the microfluidic channels are all etched with a square cross-section using a photolithography machine.

[0040] As a preferred technical solution, the microfluidic chip can withstand a temperature range of 25-200℃.

[0041] As a preferred technical solution, the flow rate range of the injection pump is 50-1000 μL / min.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention provides a continuous and controllable preparation and application of highly stable full-spectrum perovskite nanocrystals. The preparation method is based on microfluidic chip to realize the synthesis of highly stable full-spectrum perovskite nanocrystals. Microfluidics refers to the science and technology involved in the system of using microfluidic channels to precisely process and manipulate tiny fluids. It has the characteristics of miniaturization and integration. The common design of existing microfluidic reaction methods is to combine polytetrafluoroethylene tubes with heating stages. However, the tubes and heating stages cannot be tightly combined to form a completely closed high-temperature reaction space, and it is difficult to fix the polytetrafluoroethylene tubes and heating stages. The microfluidic chip device of the present invention is simple, the aluminum chip has a fast heat transfer rate, and the reaction zone is completely sealed in a high-temperature space.

[0044] (2) The microfluidic chip in this invention uses a photolithography machine to directly etch channels on an aluminum plate and seals the channels with fluororubber gaskets, which makes up for the shortcomings of the complex design of existing microfluidic reaction devices. The microfluidic chip reaction method can enhance the heat and mass transfer rate of the reaction reagents and achieve uniform mixing of the reaction reagents within seconds. The rapid and efficient mixing can reduce the difference in residence time between the reaction reagents. At the same time, this invention can rapidly, continuously and controllably synthesize perovskite nanocrystal particles with good reproducibility, good dispersibility and uniform particle size by precisely controlling the preheating and reaction temperature of the reaction reagents in the microfluidic channel and the flow rate in the channel. It can also realize the large-scale preparation of perovskite nanocrystals. Moreover, the small cross-sectional area of ​​the channel allows for faster mixing of the reaction substances, which is more conducive to the reaction. The first fluid phase is a cesium precursor and the second fluid phase is a lead precursor. The reaction phase is not divided into small droplets by fluorinated oil, but flows continuously and the reaction zone is uninterrupted.

[0045] (3) Existing studies on the composite of perovskite nanocrystals with inorganic titanium dioxide generally reduce the luminescence intensity of perovskite nanocrystals. However, this invention utilizes nano-titanium dioxide to coat perovskite nanocrystals, which not only enhances the luminescence intensity of perovskite nanocrystals and promotes carrier migration, but also enhances the water stability and thermal stability of perovskite nanocrystals. According to the composition and ratio of lead halide, the full spectrum of highly stable perovskite nanocrystals can be regulated, which promotes the widespread application of perovskite nanocrystals in the field of optoelectronic materials. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the external structure of the apparatus for preparing highly stable full-spectrum perovskite nanocrystals in an embodiment of the present invention;

[0047] Figure 2This is a schematic diagram of the internal structure of the apparatus for preparing highly stable full-spectrum perovskite nanocrystals in an embodiment of the present invention;

[0048] Figure 3 The photoemission spectra of perovskite nanocrystals in Example 9 and Comparative Example 2 of this invention are shown below.

[0049] Figure 4 This is a field emission scanning electron microscope image of nano-titanium dioxide in Comparative Example 1 of the present invention;

[0050] Figure 5 This is a field emission scanning electron microscope image of the perovskite nanocrystals in Comparative Example 2 of this invention;

[0051] Figure 6 This is a field emission scanning electron microscope image of the highly stable full-spectrum perovskite nanocrystals in Example 9 of the present invention;

[0052] Figure 7 The thermal stability luminescence intensity graphs of perovskite nanocrystals in Example 9 and Comparative Example 2 of this invention are shown.

[0053] Figure 8 The following are line graphs showing the water stability luminescence intensity of perovskite nanocrystals in Example 9 and Comparative Example 2 of this invention.

[0054] Figure 9 This is the photoemission spectrum of the highly stable full-spectrum perovskite nanocrystals in an embodiment of the present invention.

[0055] Explanation of markings in the diagram:

[0056] 1—Injection pump, 2—First syringe, 3—Second syringe, 4—Upper plate, 5—Gasket, 6—Lower plate, 7—First microfluidic channel, 8—Second microfluidic channel, 9—Third microfluidic channel, 10—Heating platform, 11—Collection device. Detailed Implementation

[0057] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0058] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0059] Examples 1 to 9:

[0060] An apparatus for preparing highly stable full-spectrum perovskite nanocrystals, such as Figure 1 and Figure 2 As shown, it includes an injection pump 1, a first syringe 2, a second syringe 3, a microfluidic chip, a heating stage 10, and a collection device 11. The microfluidic chip includes an upper plate 4, a gasket 5, a lower plate 6, a first microfluidic channel 7, a second microfluidic channel 8, and a third microfluidic channel 9.

[0061] The lower plate 6 is provided with a first microfluidic channel 7, a second microfluidic channel 8, and a third microfluidic channel 9. The first microfluidic channel 7, the second microfluidic channel 8, and the third microfluidic channel 9 are connected in a T-shaped channel. The first syringe 2 is connected to the first microfluidic channel 7 through a transparent polytetrafluoroethylene (PTFE) tube and a high-temperature resistant polypropylene (PP) inverted cone connector. The second syringe 3 is connected to the second microfluidic channel 8 through a transparent PTFE tube and a high-temperature resistant PP inverted cone connector. The third microfluidic channel 9 is connected to the collecting device 11 through a transparent PTFE tube and a high-temperature resistant PP inverted cone connector.

[0062] The first syringe 2 and the second syringe 3 are connected to the injection pump 1. The injection pump 1 is used to push the first syringe 2 and the second syringe 3. An upper plate 4 is provided on the lower plate 6. The upper plate 4 is sealed to the lower plate 6 through a gasket 5. A heating table 10 is provided under the lower plate 6. The heating table 10 is used to heat the lower plate 6.

[0063] The collection device 11 is a 50mL centrifuge tube commonly used in laboratories, used to receive the materials synthesized in the third microfluidic pipeline 9;

[0064] The first syringe 2 and the second syringe 3 are both syringes that are matched with the injection pump 1, and the specifications are 10-50mL, preferably 10mL in this embodiment;

[0065] Both the upper plate 4 and the lower plate 6 are made of metal aluminum plates. The length and width of both the upper plate 4 and the lower plate 6 are 100×70mm, and the thickness is 8mm. The gasket 5 is a fluororubber gasket with a thickness of 2mm.

[0066] The microfluidic channels were all etched using a photolithography machine with a width of 0.5 mm, a depth of 0.3 mm, and a thickness of 0.15 mm. 2 The flow channel has a square cross-section, with the first microfluidic pipe 7 and the second microfluidic pipe 8 both having a flow channel length of 200 mm, and the third microfluidic pipe 9 being the precursor mixing reaction zone with a flow channel length of 530 mm.

[0067] The microfluidic chip can withstand a temperature range of 25-200℃;

[0068] The flow rate of the syringe pump 1 can be adjusted to a range of 50-1000 μL / min.

[0069] A highly stable full-spectrum perovskite nanocrystal is synthesized by fully modifying the surface of nano-titanium dioxide (TiO2) with lead halide (PbX2). The perovskite (CsPbX3) nanocrystals generated by the reaction of PbX2 with cesium precursor are combined in situ with nano-TiO2 during the synthesis process. The nano-TiO2 coats the CsPbX3 nanocrystals and modifies the surface defects of the CsPbX3 nanocrystals.

[0070] In Examples 1 to 9, different PbX2 components and ratios were used, namely Cl:Br = 3:0, Cl:Br = 2:1, Cl:Br = 1.5:1.5, Cl:Br = 1:2, Cl:Br = 0:3, Br:I = 2:1, Br:I = 1.5:1.5, Br:I = 1:2 and Br:I = 0:3.

[0071] The above-mentioned method for preparing highly stable full-spectrum perovskite nanocrystals, using the aforementioned apparatus, allows for the continuous and controllable preparation of perovskite nanocrystals. The specific steps are as follows:

[0072] S1. Preparation of precursor solution: Weigh 0.814 g of cesium carbonate (Cs2CO3), 2.5 mL of oleic acid (OA), and 40 mL of octadecene (ODE) into a 100 mL three-necked flask. Stir magnetically at 120 °C for 1 h under a nitrogen atmosphere, then raise the temperature to 150 °C and stir magnetically for 0.5 h. Cs2CO3 and OA react completely to obtain cesium oleate (Cs-Oleate) solution. Take 0.5 mL of Cs-Oleate solution into a 25 mL three-necked flask, add 9.5 mL of ODE to dilute, and stir magnetically at 120 °C for 10 min under a nitrogen atmosphere until the solution is clear. This solution is used as the first precursor solution.

[0073] S2. PbX2 was weighed with different halogen molar ratios, and the total molar amount of different halogens was 0.376 mmol. The molar ratios were Cl:Br = 3:0, Cl:Br = 2:1, Cl:Br = 1.5:1.5, Cl:Br = 1:2, Cl:Br = 0:3, Br:I = 2:1, Br:I = 1.5:1.5, Br:I = 1:2 and Br:I = 0:3. 0.1 g of nano TiO2, 1 mL of OA, 1 mL of oleylamine (OAm) and 10 mL of ODE were added to each of these components and placed in a 50 mL three-necked flask. The mixture was magnetically stirred at 120 °C for 0.5 h under a nitrogen atmosphere. The surface of the nano TiO2 was fully modified by PbX2 to form lead halide / nano titanium dioxide (PbX2 / TiO2). The PbX2 / TiO2 reacted completely with OA and OAm to obtain a PbX2 / TiO2 solution as the second precursor solution.

[0074] S3. Transfer 10 mL each of the first precursor solution and the second precursor solution to the first syringe 2 and the second syringe 3, respectively, wherein the ion molar ratio is Cs:Pb = 1:6; connect the first syringe 2 and the second syringe 3 to the microfluidic chip and the collecting device 11 through a transparent PTFE tube and a high-temperature resistant PP inverted conical connector; place the aluminum microfluidic chip on the heating stage 10, adjust the temperature of the heating stage 10 to 160℃, and adjust the flow rate of the injection pump 1 to 500 μL / min to drive the precursor solutions in the first syringe 2 and the second syringe 3 to... Uniform flow in the microfluidic channel; the reaction time is determined by the flow rate of the mixed precursor in the reaction zone and the width, depth and channel length of the microfluidic channel in the reaction zone, and the reaction time is 5s; the liquid in the collection device 11 is centrifuged at 10000 r / min for 5 min, the supernatant is discarded, and a highly stable full-spectrum perovskite (CsPbX3 / TiO2) nanocrystal precipitate is obtained. After washing twice with an appropriate amount of n-hexane at 10000 r / min for 5 min, the CsPbX3 / TiO2 nanocrystal precipitate is dispersed in n-hexane for characterization.

[0075] To ensure successful synthesis of CsPbX3 / TiO2 nanocrystals, the experimental temperature needs to be controlled between 140-180℃, preferably 160℃ in this embodiment; the experimental flow rate needs to be controlled between 300-800μL / min, preferably 500μL / min in this embodiment.

[0076] The raw material composition and process parameters for preparing the first precursor solution and the second precursor solution in the embodiments are shown in Table 1.

[0077] Table 1. Raw material composition and process parameters for the examples.

[0078]

[0079] Comparative Example 1:

[0080] Nano titanium dioxide.

[0081] Comparative Example 2:

[0082] An apparatus for preparing perovskite nanocrystals is the same as in the example.

[0083] A perovskite nanocrystal, essentially the same as in Example 9, except that PbI2 reacts directly with the cesium precursor to generate CsPbI3 nanocrystals.

[0084] The preparation method of the above perovskite nanocrystals is basically the same as that of Example 9, except that nano-TiO2 is not added to the second precursor solution in step S2 to obtain CsPbI3 nanocrystals.

[0085] The emission spectra of the highly stable full-spectrum perovskite nanocrystals in Example 9 and the perovskite nanocrystals in Comparative Example 2 were tested using a fluorescence spectrometer (HITACHI F-7500).

[0086] like Figure 3 As shown, under 577nm excitation, the luminescence intensity of CsPbX3 nanocrystals combined with nano-TiO2 in Example 9 is significantly higher than that of CsPbX3 nanocrystals in Comparative Example 2.

[0087] Field emission scanning electron microscope images of the highly stable full-spectrum perovskite nanocrystals in Example 9, as well as the nano-titanium dioxide in Comparative Example 1 and the perovskite nanocrystals in Comparative Example 2.

[0088] like Figure 4 As shown, the nano-TiO2 in Comparative Example 1 is mainly composed of spherical particles aggregated together.

[0089] like Figure 5 As shown, in Comparative Example 2, the CsPbX3 nanocrystals have a rod-shaped morphology and a relatively smooth surface, with the surface of the CsPbX3 nanocrystals being fully exposed.

[0090] like Figure 6 As shown, the CsPbX3 / TiO2 nanocrystals in Example 9 have a rod-like morphology and their surfaces are covered with a large amount of nano-TiO2, resulting in a reduced surface exposed area.

[0091] The highly stable full-spectrum perovskite nanocrystals dispersed in n-hexane in Example 9 and the nanocrystals dispersed in n-hexane in Comparative Example 2 were centrifuged at 10,000 r / min to obtain CsPbI3 / TiO2 nanocrystals and CsPbI3 nanocrystal precipitates. After being stored at room temperature in a vacuum drying oven for 4 h, the CsPbI3 / TiO2 nanocrystals and CsPbI3 nanocrystals were ground for 10 min and then tested for thermal stability at 30-110 °C.

[0092] like Figure 7 As shown, although the luminescence intensity of the nanocrystals in Example 9 and Comparative Example 2 decreased with increasing temperature, the decreasing trend of luminescence intensity of the CsPbX3 nanocrystals after being combined with nano-TiO2 in Example 9 was significantly weaker than that of the CsPbX3 nanocrystals in Comparative Example 2. The CsPbI3 nanocrystals in Comparative Example 2 experienced fluorescence quenching at 110°C, while the CsPbI3 nanocrystals after being combined with nano-TiO2 in Example 9 maintained a luminescence intensity of 52% of the initial value at 110°C. This indicates that combining with nano-TiO2 enhances the thermal stability of the CsPbX3 nanocrystals.

[0093] The highly stable full-spectrum perovskite nanocrystals dispersed in n-hexane in Example 9 and the nanocrystals dispersed in n-hexane in Comparative Example 2 were mixed with deionized water at a volume ratio of 1:1, and the spectral changes of CsPbI3 / TiO2 nanocrystals and CsPbI3 nanocrystals were recorded every 5 min.

[0094] like Figure 8 As shown, although the luminescence intensity of the nanocrystals in Example 9 and Comparative Example 2 decreased with time, the luminescence intensity of the CsPbX3 nanocrystals after being combined with nano TiO2 in Example 9 showed a significantly weaker decreasing trend than that of the CsPbX3 nanocrystals in Comparative Example 2. The CsPbI3 nanocrystals in Comparative Example 2 quenched their fluorescence after 0.5 h, while the luminescence intensity of the CsPbI3 nanocrystals after being combined with nano TiO2 in Example 9 remained at 38% of the initial value after 0.5 h. This indicates that combining with nano TiO2 enhances the water stability of the CsPbX3 nanocrystals.

[0095] The emission spectra of the highly stable full-spectrum perovskite nanocrystals in Examples 1 to 9 were tested at their respective optimal excitation wavelengths using a fluorescence spectrometer.

[0096] like Figure 9 As shown, the emission wavelength can be tuned in the 408-702nm band, and the full width at half maximum (FWHM) can be tuned in the 13.2-34.4nm range. This indicates that the full spectrum of highly stable perovskite nanocrystals can be tuned according to the composition and ratio of lead halide, which promotes the widespread application of perovskite nanocrystals in the field of optoelectronic materials.

[0097] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A highly stable full-spectrum perovskite nanocrystal, characterized in that, The surface of nano-titanium dioxide is modified with lead halide, which then reacts with cesium precursor to generate perovskite nanocrystals. During the synthesis process, the perovskite nanocrystals are combined with nano-titanium dioxide in situ, and the nano-titanium dioxide coats the perovskite nanocrystals. The lead halide is selected from one or more of lead chloride, lead bromide, and lead iodide, the molar ratio of the lead halide to nano titanium dioxide is 1:(1-4), and the molar ratio of cesium in the cesium precursor to lead in the lead halide is 1:(2-7). The preparation method of the perovskite nanocrystals includes the following steps: S1. Preparation of precursor solution: Cesium source, oleic acid and octadecene are mixed in an inert gas atmosphere, and then heated to obtain cesium oleate solution. Octadecene is added to the cesium oleate solution for dilution, and the mixture is then mixed in an inert gas atmosphere to obtain the first precursor solution. S2. Lead halide, nano titanium dioxide, oleic acid, oleylamine and octadecene are mixed in an inert gas atmosphere to obtain a lead halide / nano titanium dioxide solution as a second precursor solution. S3. The first precursor solution and the second precursor solution are transferred to the first syringe (2) and the second syringe (3) respectively. The microfluidic chip is placed on the heating stage (10), and the injection pump (1) drives the precursor solutions in the first syringe (2) and the second syringe (3) to flow uniformly and mix in the microfluidic channel to obtain highly stable full-spectrum perovskite nanocrystals.

2. The highly stable full-spectrum perovskite nanocrystals according to claim 1, characterized in that, The cesium precursor includes cesium carbonate or cesium acetate.

3. A method for preparing highly stable full-spectrum perovskite nanocrystals as described in claim 1 or 2, characterized in that, The method includes the following steps: S1. Preparation of precursor solution: Cesium source, oleic acid and octadecene are mixed in an inert gas atmosphere, and then heated to obtain cesium oleate solution. Octadecene is added to the cesium oleate solution for dilution, and the mixture is then mixed in an inert gas atmosphere to obtain the first precursor solution. S2. Lead halide, nano titanium dioxide, oleic acid, oleylamine and octadecene are mixed in an inert gas atmosphere to obtain a lead halide / nano titanium dioxide solution as a second precursor solution. S3. The first precursor solution and the second precursor solution are transferred to the first syringe (2) and the second syringe (3) respectively. The microfluidic chip is placed on the heating stage (10), and the injection pump (1) drives the precursor solutions in the first syringe (2) and the second syringe (3) to flow uniformly and mix in the microfluidic channel to obtain highly stable full-spectrum perovskite nanocrystals.

4. The method for preparing highly stable full-spectrum perovskite nanocrystals according to claim 3, characterized in that, In step S1, the molar / volume ratio of cesium, oleic acid and octadecene in the cesium source is 1 mol:(0.4-0.6 L):(6-9 L).

5. The method for preparing highly stable full-spectrum perovskite nanocrystals according to claim 3, characterized in that, In step S2, the molar / volume ratio of lead halide, nano titanium dioxide, oleic acid, oleylamine and octadecene is 1 mol:(1-4 mol):(1-3 L):(1-3 L):(20-40 L).

6. The method for preparing highly stable full-spectrum perovskite nanocrystals according to claim 3, characterized in that, The temperature for the first mixing in step S1 is 110-130 ℃, and the time is 1-1.5 h; The heating and mixing temperature is 140-160 ℃, and the time is 0.5-1 h; The dilution factor is 15-25 times, and the mixing temperature after dilution is 110-130 ℃, and the time is 10-15 min.

7. The method for preparing highly stable full-spectrum perovskite nanocrystals according to claim 3, characterized in that, In step S2, the mixing temperature is 110-130 ℃ and the time is 0.5-1 h.

8. The method for preparing highly stable full-spectrum perovskite nanocrystals according to claim 3, characterized in that, In step S3, the reaction time is 3-8 s, the reaction temperature is 140-180 ℃, and the flow rate is 300-800 μL / min.

Images