A centimeter-scale and thermodynamically stable FAPbI3 single crystal, its preparation method, and a pre-derivatization method for molecular-level recognition of the chemical environment of the mother liquor solution.

Abstract

This invention discloses a centimeter-scale and thermodynamically stable FAPbI3 single crystal, its preparation method, and a pre-derivatization method for molecular-level recognition of the chemical environment of the mother liquor solution. The preparation method includes: uniformly mixing formamidinium hydroiodate, lead iodide, and a single solvent containing a macrocyclic lactone structure compound to form a precursor liquid; forming crystal nuclei in the precursor liquid at a first temperature, and uniformly heating to a second temperature to maintain the cyclic structure of the macrocyclic lactone compound, resulting in centimeter-scale FAPbI3 single crystals; and isothermal treatment at the second temperature to promote ring-opening of the macrocyclic lactone compound to generate long-chain hydroxy acid molecules, resulting in centimeter-scale and stable FAPbI3 single crystals. This invention also provides a pre-derivatization method, using boron trifluoride methanol to perform methyl esterification derivatization on the target molecule, or silanized acetamide derivatization on the target molecule, followed by gas chromatography-mass spectrometry analysis, thereby achieving non-destructive recognition of the target molecule in the mother liquor solution chemistry.

Description

Technical Field

[0001] This invention belongs to the field of metal halide single crystal technology, specifically relating to a centimeter-scale and thermodynamically stable FAPbI3 single crystal, its preparation method, and a pre-derivation method for molecular-level recognition of the chemical environment of the mother liquor solution. Background Technology

[0002] All-formamidinium lead iodine (FAPbI3) has potential applications in high-energy X-ray photoelectron detection technology and solar cells due to its optimal optical band gap of 1.48 eV and thermal stability. However, its photoactive cubic phase α-FAPbI3 is thermodynamically unstable at room temperature and readily undergoes a phase transition to the non-photoactive hexagonal δ phase, i.e., the intrinsic thermodynamic phase transition. Currently studied polycrystalline thin films exhibit high densities of grain boundaries, point defects, dislocations, and residual stresses. These defects significantly lower the phase transition energy barrier and accelerate the phase transition kinetics. To accurately investigate the intrinsic thermodynamic phase transition trend, single-crystal phase transition behavior is closer to the intrinsic thermodynamic limit.

[0003] Currently, during the growth and aging of existing FAPbI3 crystals, the precursor solution for FAPbI3 single crystals involves complex multi-solvent mixing (such as a mixture of DMF, DMSO, and NMP solvents), and I3 inevitably forms in the mother liquor environment. - I3 - It will cause FA on the crystal surface through strong hydrogen bonding. + Deprotonation and decomposition ultimately lead to crystal phase transitions or dissociation. Furthermore, centimeter-scale FAPbI3 single crystals can be obtained using a single cyclic lactone solvent (such as γ-butyrolactone, GBL), or relatively stable millimeter-scale single crystals can be obtained using solvents with hydroxyl-carrying chains (such as 2-methoxyethanol, 2-ME). However, these methods cannot completely block phase transitions or degradation caused by the mother liquor chemical environment while maintaining centimeter-scale single crystal size. FAPbI3 single crystal growth solvents cannot simultaneously achieve centimeter-scale single crystal preparation and long-term thermodynamic phase stability. For example, Chinese patent CN119593051A discloses a method for preparing ultra-low defect perovskite single crystals based on steric hindrance control. However, this method only focuses on low defect density in the single crystal. The mixed solvent of DVL and GBL is only used as a coordination solvent, serving a physical dissolution function. Moreover, the mixed solvent is used to control crystallization temperature and defect density, and steric hindrance can only be controlled by changing the solvent ratio, lacking molecular-level chemical design. It does not address the thermodynamic phase stability and long-term environmental stability of the crystal.

[0004] Meanwhile, there is a lack of suitable molecular-level detection methods for the dynamic evolution of molecules in the chemical environment of perovskite mother liquor during crystal growth. Conventional gas chromatography-electron impact mass spectrometry (GC-EI-MS) encounters difficulties in detecting the reaction residue after single crystal growth because the target molecule, 5-hydroxyvalerate, has polar hydroxyl and carboxyl groups at both ends, which couple with the chromatographic column, resulting in poor volatility, no eluent phase, and difficulty in separation and detection. Therefore, existing analytical methods in GC-MS lack the ability to accurately identify the chemical environment of perovskite mother liquor, and cannot non-destructively identify and separate target molecules within the mother liquor chemical environment. This prevents accurate identification through the chromatographic column, and consequently, fails to address the phase transitions and degradation problems caused by the mother liquor chemical molecules at their source. Summary of the Invention

[0005] The main objective of this invention is to provide a centimeter-scale and thermodynamically stable FAPbI3 single crystal, its preparation method, and a pre-derivation method for molecular-level identification of the chemical environment of the mother liquor solution, thereby achieving molecular-level identification of the chemical environment of the perovskite mother liquor and overcoming the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: The first aspect of the present invention provides a method for preparing centimeter-scale and thermodynamically stable FAPbI3 single crystals, comprising: Formamidin hydroiodide, lead iodide, and a single solvent containing a compound with a macrocyclic lactone structure are mixed evenly to form a precursor fluid. The precursor liquid is allowed to form crystal nuclei at a first temperature, and then the temperature is raised at a constant rate to a second temperature to keep the macrocyclic lactone compound in a cyclic state, promote crystal growth, and obtain centimeter-sized FAPbI3 single crystals. The second temperature was used to promote the ring-opening of macrocyclic lactone compounds to generate long-chain hydroxy acid molecules, resulting in centimeter-scale and stable FAPbI3 single crystals.

[0007] The second aspect of the present invention provides centimeter-scale and stable FAPbI3 single crystals prepared by the above method, with a crystal diameter of 0.5 to 1.2 cm. The FAPbI3 single crystals can maintain thermodynamic phase stability for more than 11,520 hours under standard solar irradiation and 43% relative humidity.

[0008] A third aspect of the present invention provides a pre-derivatization method for molecular-level recognition of the chemical environment of a mother liquor solution, comprising: The reaction solution for the above-mentioned FAPbI3 single crystal growth process is provided, wherein the reaction solution contains the target molecule; The target molecule is derivatized by methyl esterification with boron trifluoride methanol or by silanization with acetamide derivatization reagent, followed by gas chromatography-mass spectrometry analysis, thereby achieving non-destructive separation and identification of the target molecule in the mother liquor chemical environment.

[0009] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The method for preparing centimeter-sized FAPbI3 single crystals provided by the present invention is to maintain the long-term stability of centimeter-sized FAPbI3 single crystals by in-situ ring opening of δ-valerol (DVL) to 5-hydroxyvaleric acid. It combines the dual advantages of "ring-shaped promotion of centimeter size" and "chain-shaped promotion of stability", and achieves the dual effect of macroscopic promotion of crystal size and microscopic promotion of lattice stability. It breaks through the bottleneck problem of size and thermodynamic phase stability. The obtained FAPbI3 single crystals have centimeter-sized size and can maintain ultra-long-term α phase thermodynamic stability for more than 11,520 hours under one solar irradiation (nitrogen atmosphere) and aging in air with 43% relative humidity. There is no non-photoactive δ phase and PbI2 generated, which far exceeds the current 4,400 hours of water / oxygen stability.

[0010] (2) The method for preparing centimeter-scale FAPbI3 single crystals provided by this invention cuts off the degradation pathway at its source. 5-Hydroxyvalerate is not related to the destructive substance I3. - Instead of direct competition, it uses the strong negative charge and hydrogen bonding of the carboxylic acid group of the organic molecule 5-hydroxyvalerate to lock the surface structure at the cost of sacrificing a single layer, thereby inhibiting the chain reaction degradation pathway from the surface to the interior. (3) The derivatization treatment method provided by the present invention realizes the non-destructive derivatization treatment of perovskite mother liquor. It adopts a mild precursor derivatization detection method, which eliminates the damage to the fragile chemical environment of the mother liquor caused by the detection and analysis method itself, and provides a highly reliable new method for the mechanism study of complex solvent systems. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The images show the X-ray diffraction (XRD) pattern of the FAPbI3 single crystal of Embodiment 1 of the present invention after continuous irradiation for 11520 hours under N2 atmosphere and 1 solar irradiance (AM1.5), as well as the appearance of the crystal at different aging times. Figure 2XRD pattern of FAPbI3 single crystal in Example 1 of this invention when stored in ambient air with relative humidity controlled at 43±1% and appearance of the crystal at different aging times; Figure 3 These are the photoluminescence (PL) emission spectra of the FAPbI3 single crystal of Example 1 of the present invention under one solar irradiation (N2 atmosphere) and in air with a relative humidity of 43±1%. Figure 4 This is the PL emission spectrum of the FAPbI3 single crystal of Example 1 of the present invention under continuous excitation at 469 nm for 280 minutes; Figure 5 This is the time-resolved photoluminescence (TRPL) spectrum of the FAPbI3 single crystal of Example 1 of the present invention under N2 atmosphere, one solar irradiation, and aged for 11520 hours in air with a relative humidity of 43±1%. Figure 6 This is the total ion chromatogram (TIC) of the perovskite mother liquor after methylation treatment in Example 2 of the present invention; Figure 7 This is the total ion chromatography (TIC) chromatogram of the perovskite mother liquor after silanization treatment in Example 2 of this invention; Figure 8 This is the EI-MS mass spectrum of the silanized 5-hydroxyvalerate derivative (M1) with a retention time of 4.5 minutes in electron impact mass spectrometry (EI-MS) of Example 2 of the present invention. Figure 9 This is a schematic diagram of the cleavage path and representative cationic fragments generated after the silanization treatment of the 5-hydroxyvalerate derivative in Example 2 of the present invention under electron bombardment ionization. Detailed Implementation

[0013] In view of the problems existing in the prior art, after in-depth research, a method for preparing centimeter-scale and thermodynamically stable FAPbI3 single crystals and a pre-derivatization method for molecular-level recognition of the chemical environment of the mother liquor solution is provided, thereby achieving molecular-level recognition of the evolution of the chemical environment of the mother liquor solution.

[0014] This invention provides a method for preparing FAPbI3 single crystals based on inverse temperature crystallization (ITC). This method achieves long-term thermodynamic phase stability while maintaining centimeter-sized (diameter > 1 cm) α-FAPbI3 single crystals. Using δ-valerol (DVL) as the sole solvent, the slow ring-opening release of 5-hydroxyvaleric acid by DVL during single crystal growth enhances phase stability while obtaining large-size single crystals. Test results show that the obtained α-FAPbI3 single crystals maintain phase stability for over 11520 hours under standard solar irradiation (AM1.5G) and 43% relative humidity, without undergoing phase transformation or decomposition.

[0015] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0016] The first aspect of the present invention provides a method for preparing centimeter-scale and thermodynamically stable FAPbI3 single crystals, comprising: Formamidin hydroiodide, lead iodide, and a single solvent containing a compound with a macrocyclic lactone structure are mixed evenly to form a precursor fluid. The precursor liquid forms crystal nuclei at the first temperature, which keeps the macrocyclic lactone structure compound in a cyclic state and promotes crystal growth to obtain centimeter-sized FAPbI3 single crystals. The macrocyclic lactone compound is kept at the second temperature to promote ring-opening and generate long-chain hydroxy acid molecules, thereby improving the stability of FAPbI3 single crystals and obtaining centimeter-sized and thermodynamically stable FAPbI3 single crystals.

[0017] In this invention, if the first temperature is too high, there will be too many nucleation sites, making it impossible to form centimeter-sized single crystals; if the temperature is too low, homogeneous nucleation will not be possible. If the second temperature is too high, too much lactone will open; if the temperature is too low, the amount of lactone opening will be insufficient, resulting in thermodynamic instability of the FAPbI3 single crystal.

[0018] In some embodiments, the molar concentrations of formamidinium hydroiodate and lead iodide in the macrolide compound are 0.8~1.8 mol / L and 0.8~1.8 mol / L, respectively.

[0019] In some embodiments, the macrocyclic lactone compound includes δ-valerolactone.

[0020] In some embodiments, the long-chain hydroxy acid molecule includes 5-hydroxyvalerate.

[0021] In some embodiments, the preparation method specifically includes: mixing the formamidin hydroiodide, lead iodide, and a single solvent containing a macrocyclic lactone structure uniformly at room temperature and pressure, followed by ultrasonic treatment for 10-20 minutes to obtain the precursor fluid.

[0022] In some embodiments, the preparation method specifically includes: heating the precursor liquid to a first temperature of 105~120℃ and holding it at that temperature for 0.5~2h to form crystal nuclei in the precursor liquid; then uniformly heating it to a second temperature of 170~190℃ at a heating rate of 5~15℃ / h, while maintaining the cyclic shape of the macrocyclic lactone compound during the uniform heating process, to obtain the centimeter-sized FAPbI3 single crystal.

[0023] In some embodiments, the preparation method specifically includes: maintaining a constant temperature at the second temperature for 0.5 to 2 hours to promote the ring-opening of the compound with the macrocyclic lactone structure to generate long-chain hydroxy acid molecules, followed by annealing at 170 to 190°C for 30 to 120 minutes and vacuum drying at 170 to 190°C for 1 to 3 hours to obtain the centimeter-sized and thermodynamically stable FAPbI3 single crystal.

[0024] In some more specific implementations, the manufacturing method specifically includes the following steps: (1) At room temperature (25 °C) and normal pressure (1 atm), formamidinium hydroiodide, lead iodide and δ-valerolactone (DVL) are mixed evenly to obtain the precursor body fluid, wherein the molar concentrations of formamidinium hydroiodide and lead iodide in δ-valerolactone are 0.8~1.8 mol / L and 0.8~1.8 mol / L, respectively.

[0025] (2) The precursor fluid was filtered using a PTFE needle filter with a pore size of 0.22 μm, and the filtrate was collected into a clean crystallization bottle.

[0026] (3) Place the crystallization bottle containing the filtered precursor liquid on a heating platform and heat it to the first temperature of 105~120℃. Hold the temperature for 0.5~2h to allow the precursor liquid to form stable crystal nuclei. Then, use a programmed heating mode to uniformly heat the liquid to the second temperature of 170~190℃ at a heating rate of 5~15℃ / h. During this process, the single crystal gradually grows. The uniform heating process keeps the δ-valerolactone in a ring shape, promotes crystal growth, and achieves the effect of "ring-promoting centimeter-level growth" to obtain the centimeter-level FAPbI3 single crystal.

[0027] (4) When the temperature is raised to the second temperature, it is kept constant for 0.5~2h to promote the rapid ring opening of the solvent δ-valerol to generate 5-hydroxyvaleric acid, thereby improving the stability of the single crystal and achieving the effect of "chain-like stabilization".

[0028] (5) Under the second temperature condition, the grown FAPbI3 single crystal is taken out from the solution, the residual solution on the surface is quickly removed, and then annealed at 170~190℃ for 30~120min and vacuum dried at 170~190℃ for 1~3h to obtain the centimeter-sized and stable FAPbI3 single crystal.

[0029] The second aspect of the present invention provides a centimeter-sized and thermodynamically stable FAPbI3 single crystal prepared by the above method, with a crystal diameter of 0.5~1.2cm. The FAPbI3 single crystal can maintain thermodynamic stability for more than 11520 hours under standard solar irradiation and 43% relative humidity.

[0030] In some embodiments, the crystal phase of the FAPbI3 single crystal includes an α phase. In this invention, 5-hydroxyvalerate achieves long-term thermodynamic phase stability by reducing the surface energy of the FAPbI3 single crystal. The specific mechanism is as follows: Iodide ion oxidation is unavoidable during the precursor solution and single crystal aging process. The organic cation A sites on the FAPbI3 single crystal surface react with I3... - Hydrogen bonds are formed, leading to deprotonation and decomposition. The carboxyl group carried by 5-hydroxyvalerate, with a strong negative charge, enters the decomposed A-site vacancy through hydrogen bonding, causing the single crystal surface to regain stability.

[0031] A third aspect of the present invention provides a pre-derivatization method for molecular-level recognition of the chemical environment of a mother liquor solution, comprising: The reaction solution for the above-mentioned FAPbI3 single crystal growth process is provided, wherein the reaction solution contains the target molecule; The target molecule is derivatized by methyl esterification with boron trifluoride methanol or by silanization with acetamide derivatization reagent, followed by gas chromatography-mass spectrometry analysis, thereby achieving non-destructive separation and identification of the target molecule in the mother liquor chemical environment.

[0032] In some embodiments, the target molecule includes 5-hydroxyvalerate.

[0033] In some embodiments, the volume ratio of boron trifluoride methanol to the reaction solution is 1:10~50.

[0034] In some embodiments, the silanized acetamide derivatizing agent includes N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide or N,O-bis(trimethylsilyl)trifluoroacetamide.

[0035] Preferably, the volume ratio of N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide to the reaction solution is 1:10~50.

[0036] Preferably, the volume ratio of N,O-bis(trimethylsilyl)trifluoroacetamide to the reaction solution is 1:10~50.

[0037] In some embodiments, the methyl esterification derivatization treatment is performed at a temperature of 50-70°C for a time of 20-40 minutes.

[0038] In some embodiments, the silanization derivatization treatment is performed at a temperature of 50-70°C for a time of 20-40 minutes.

[0039] In some embodiments, the pre-derivative treatment method specifically includes: using the boron trifluoride methanol to perform a methyl esterification derivatization treatment on the 5-hydroxyvalerate, converting the hydroxyl and carboxyl groups at both ends of the 5-hydroxyvalerate into methyl ether and methyl ester, respectively; Alternatively, the 5-hydroxyvalerate can be silanized and derivatized using the silanized acetamide derivatizing agent to convert the hydroxyl and carboxyl groups at both ends of the 5-hydroxyvalerate into trimethylsilyl ether and trimethylsilyl ester, respectively.

[0040] This invention significantly improves the volatility and thermal stability of the organic molecules being tested without disrupting the chemical equilibrium of the original solution by employing a pre-derivative treatment method.

[0041] The technical solution of the present invention will be further described below through embodiments. Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field.

[0042] Example 1 This embodiment provides a method for preparing FAPbI3 single crystal, and the specific steps are as follows: (1) Preparation of precursor solution: Under normal temperature (25 °C) and normal pressure (1 atm), weigh 3.2 mmol of formamidinium hydroiodate (FAI) and 3.2 mmol of lead iodide (PbI2). Measure 2 mL of δ-valerolactone (DVL) as solvent and add it to the above raw materials. Vigorously shake and stir, then sonicate for 30 minutes until the solid is completely dissolved.

[0043] (2) Solution filtration: The solution was filtered using a PTFE needle filter with a pore size of 0.22 μm, and the filtrate was collected into a clean crystallization bottle.

[0044] (3) Single crystal growth: The crystallization flask containing the precursor solution was placed on a heating platform, and the initial temperature was set to 115℃ and held for 2 hours to allow stable crystal nuclei to form in the solution. Subsequently, a programmed temperature rise mode was used to uniformly increase the temperature from 115℃ to 180℃ over 8 hours, during which the single crystals gradually grew. The slow temperature rise program ensured that most of the DVLs remained cyclic, achieving the effect of "cyclic growth promoting centimeter-level crystal growth".

[0045] (4) High temperature treatment: When the temperature rises to 180 ℃, it is kept constant for 1 hour to promote the rapid ring opening of the solvent δ-valerol (DVL) to generate 5-hydroxyvaleric acid, thereby improving the stability of the single crystal and achieving the effect of "chain-like stabilization".

[0046] (5) Single crystal harvesting and post-processing: The large-sized α-FAPbI3 single crystals were removed from the solution at 180 ℃, and the residual solution on the surface was quickly removed. The crystals were then annealed on a 150 ℃ heating plate for 30 minutes, and then dried in a 150 ℃ vacuum drying oven for 12 hours to obtain centimeter-sized and stable FAPbI3 single crystals. The crystal diameter was approximately 1 cm.

[0047] (6) Storage: After the FAPbI3 single crystal has cooled, transfer it to a container for storage.

[0048] Performance testing The FAPbI3 single crystals prepared in this embodiment were subjected to long-term phase stability tests under N2 atmosphere, at one solar irradiance intensity (AM1.5), or in ambient air with relative humidity controlled at 43±1%. The X-ray diffraction (XRD) pattern of FAPbI3 single crystal after continuous irradiation for 11520 hours under N2 atmosphere and 1 solar irradiance (AM1.5) is shown below. Figure 1 As shown in the bottom illustration, the appearance of the crystals at different aging times is illustrated.

[0049] The XRD pattern of FAPbI3 single crystals stored in ambient air with a relative humidity of 43±1% is shown below. Figure 2 As shown in the bottom illustration, the appearance of the crystals at different aging times is illustrated. Figure 1 and Figure 2 It can be seen that the FAPbI3 single crystal protected by 5-hydroxyvalerate exhibits long-term phase stability under the influence of water / oxygen and light irradiation.

[0050] The photoluminescence (PL) emission spectra of FAPbI3 single crystals under one solar irradiation (N2 atmosphere) and in air with 43±1% humidity are shown below. Figure 3 As shown; from Figure 3 It can be seen that both maintain the fluorescence emission peak at 825 nm at the band edge without drift.

[0051] The PL emission spectrum of FAPbI3 single crystal after continuous excitation at 469 nm for 280 minutes is shown in the figure. Figure 4 As shown; from Figure 4 It can be seen that the fluorescence emission peak at 825 nm in the crystal does not shift with aging time.

[0052] The time-resolved photoluminescence (TRPL) spectra of FAPbI3 single crystals aged for 11520 hours under N2 atmosphere, one day of sunlight irradiation, and 43±1% humidity are shown below. Figure 5 As shown; from Figure 5 It can be seen that the fluorescence lifetime did not decrease significantly after aging for 11,520 hours.

[0053] Example 2 This embodiment provides a pre-derivatization method for molecular-level recognition of the chemical environment of the mother liquor solution, and the specific steps are as follows: (1) Methylation or silanization treatment of mother liquor Take 2 mL of the mother liquor from the FAPbI3 single crystal growth in Example 1, and add 0.2 mL of excess boron trifluoride methanol (BF3-MA) ​​as a mild derivatizing agent to perform methyl esterification derivatization of 5-hydroxyvalerate. The treatment temperature is 60 °C and the time is 30 min, converting the polar hydroxyl and carboxyl groups at both ends of 5-hydroxyvalerate into methyl ether and methyl ester, respectively. Alternatively, add 0.2 mL of excess N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) as a mild derivatizing agent to perform silanization derivatization of 5-hydroxyvalerate. The treatment temperature is 60 °C and the time is 30 min, efficiently converting the hydroxyl and carboxyl groups at both ends of 5-hydroxyvalerate into trimethylsilyl (TMS) ether and TMS ester, respectively. This treatment significantly improves the volatility and thermal stability of the tested organic molecules without disrupting the original chemical equilibrium of the solution.

[0054] (2) Effective separation by gas chromatography (GC) The sample, after the mild silanization derivatization treatment, was injected into a GC-EI-MS system. In the obtained total ion chromatogram (TIC), clear retention peaks were achieved for each component. The retention time of the target monomer 5-hydroxyvalerate was determined to be 4.50 min; the retention time of the background solvent DVL was determined to be 7.45 min; the retention time of the 5-hydroxyvalerate dimer was determined to be 21.32 min; and the retention time of the 5-hydroxyvalerate trimer was determined to be 37.44 min.

[0055] (3) Fragmentation mechanism and qualitative confirmation by electron impact mass spectrometry (EI-MS) To further confirm that the chromatographic peak at retention time 4.50 min is indeed 5-hydroxyvalerate, mass spectrometry ion fragmentation and fragmentation pathway analysis and qualitative analysis of the target molecule were performed: Figure 6 This is the total ion chromatogram (TIC) of the perovskite mother liquor after methylation treatment in this embodiment, showing the retention peaks attributed to 5-hydroxyvalerate, DVL, and 5-hydroxyvalerate dimer and trimer derivatives.

[0056] Figure 7 The TIC diagram of the perovskite mother liquor after silanization treatment in this embodiment shows the retention peaks corresponding to 5-hydroxyvalerate, DVL, and 5-hydroxyvalerate dimer and trimer derivatives.

[0057] Figure 8 This is the EI-MS mass spectrum of the silanized 5-hydroxyvalerate derivative (M1) at a retention time of 4.5 minutes, obtained using electron impact mass spectrometry (EI-MS) in this embodiment. The mass spectrum shows the detection of the TMS-specific ionic fragment [(Si(CH3)3]. + Its precise mass-to-charge ratio (m / z) was 72.94, and an ionic fragment [M1-TMS] was detected in the derived molecule that had lost a TMS group. + The m / z value is 188.96. This fragment originates from the breaking of the Si-O bond at the TMS ether in the molecule, and a carboxylic acid TMS esterification fragment [(CH3)3Si-O(CH2)2] was detected. + The m / z value is 116.86, and the fragment originates from the breakage of the alkyl chain inside the molecule.

[0058] Core peak confirmation: A highly abundant base peak ion fragment [(CH3)3Si-O-Si(CH3)2] appeared in the mass spectrum. + The m / z value is 147.00. The core fragment consists of the breakage of the Si-O bond at the TMS ether, the CO bond at the TMS ester, and the Si-C bond in the target molecule, followed by the fragments [•Si(CH3)3] and [(CH3)2Si-O•]. + It is formed by structural rearrangement.

[0059] Figure 9 This is a schematic diagram of the cleavage pathway of the silanized 5-hydroxyvalerate derivative in this embodiment under electron bombardment ionization and the generated representative cationic fragments.

[0060] The precise fragment mass-to-charge ratio data and their fragmentation and rearrangement pathways not only confirm the success of the silanization derivatization process, but also conclusively demonstrate the formation and existence of 5-hydroxyvalerate and its oligomers in the perovskite mother liquor chemical environment.

[0061] Example 3 The difference between this embodiment and Embodiment 1 is: (1) Preparation of precursor solution: Weigh 2.0 mmol formamidin hydroiodate (FAI) and 2.0 mmol lead iodide (PbI2). Measure 1.85 mL δ-valerolactone as solvent. After mixing evenly, sonicate for 10 min to obtain the precursor solution.

[0062] (2) Solution filtration: Same as in Example 1.

[0063] (3) Single crystal growth: The precursor solution is heated to the first temperature of 105℃ and held at that temperature for 0.5h to form stable crystal nuclei in the solution. Then the temperature is uniformly increased to the second temperature of 170℃ at a heating rate of 5℃ / h.

[0064] (4) High temperature treatment: Keep at 170℃ for 0.5h to promote appropriate ring opening of solvent DVL.

[0065] (5) Post-treatment: After the single crystal was removed, it was annealed at 170℃ for 30 min and then vacuum dried at 170℃ for 1 h to obtain centimeter-sized FAPbI3 single crystals. The diameter of the single crystal obtained under these conditions was about 0.6 cm. Its stability was tested at 43% relative humidity. After aging for 10,000 hours, no obvious δ phase appeared in the single crystal.

[0066] Example 4 The difference between this embodiment and Embodiment 1 is that: (1) Preparation of precursor solution: Weigh 4.0 mmol FAI and 4.0 mmol PbI2. Measure 5 mL δ-valerolactone as solvent. Mix well and then sonicate for 20 min.

[0067] (2) Solution filtration: Same as in Example 1.

[0068] (3) Single crystal growth: Heat to the first temperature of 120℃, hold for 2 hours, and after nucleation, heat to the second temperature of 190℃ at a constant rate of 15℃ / h.

[0069] (4) High temperature treatment: keep at 190℃ for 2 hours to promote the full ring opening of macrolide.

[0070] (5) Post-treatment: After the single crystal is removed, it is annealed at 190℃ for 120 min and then vacuum dried at 190℃ for 3 h. The diameter of the single crystal obtained under these conditions can reach 1.2 cm. After aging for 10,000 hours, no obvious δ phase appears in the single crystal.

[0071] Example 5 The difference between this embodiment and Embodiment 1 is that: (1) Preparation of precursor solution: Weigh 4.0 mmol FAI and 4.0 mmol PbI2. Measure 5 mL δ-valerolactone as solvent. Mix well and then sonicate for 20 min.

[0072] (2) Solution filtration: Same as in Example 1.

[0073] (3) Single crystal growth: Heat to the first temperature of 120℃, hold for 2 hours, and after nucleation, heat to the second temperature of 190℃ at a constant rate of 15℃ / h.

[0074] (4) High temperature treatment: keep at 190℃ for 2 hours to promote the full ring opening of macrolide.

[0075] (5) Post-treatment: After the single crystal is removed, it is annealed at 190℃ for 120 min and then vacuum dried at 190℃ for 3 h. The diameter of the single crystal obtained under these conditions can reach 1.2 cm. After aging for 10,000 hours, no obvious δ phase appears in the single crystal.

[0076] Example 6 This embodiment provides a pre-derivation treatment method, which differs from Embodiment 2 in that it uses N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for silanization derivatization treatment. The specific steps are as follows: Take 2 mL of the reaction mother liquor after crystal growth in Example 1, and add 0.1 mL of excess N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), i.e., the volume ratio of derivatizing reagent to reaction solution is 1:20. Gently heat at 65 °C for 25 min to perform silanization derivatization treatment on the target molecule (5-hydroxyvalerate). The BSTFA reagent can efficiently and simultaneously convert the hydroxyl and carboxyl groups at both ends of 5-hydroxyvalerate into trimethylsilyl (TMS) ether and TMS ester.

[0077] Example 7 The difference between this embodiment and Embodiment 1 is only that the single solvent is γ. Valprolactone, (1) Preparation of precursor solution: Weigh 3.2 mmol of formamidin hydroiodate (FAI) and 3.2 mmol of lead iodide (PbI2). Measure 2 mL of γ-ray disulfide (PbI2). Valproic acid lactone was added to the above raw materials as a solvent, and the mixture was vigorously shaken and stirred until the solid was completely dissolved.

[0078] (2) The other steps are the same as in Example 1.

[0079] Example 8 The only difference between this embodiment and Example 1 is that the single solvent is γ-caprolactone. (1) Preparation of precursor solution: Weigh 3.2 mmol formamidin hydroiodide (FAI) and 3.2 mmol lead iodide (PbI2). Measure 2 mL of γ-caprolactone as a solvent and add it to the above raw materials. Shake and stir vigorously until the solid is completely dissolved.

[0080] (2) The other steps are the same as in Example 1.

[0081] Comparative Example 1 The difference between this comparative example and Example 1 is that conventional γ-butyrolactone (GBL) is used instead of δ-valerolactone (DVL) as the single solvent for crystal growth, while the remaining process steps and parameters are the same as in Example 1.

[0082] Because GBL possesses extremely high thermodynamic stability within its crystallization temperature range, it is difficult for it to undergo ring-opening reactions to generate the corresponding hydroxy acid chain molecules. Although the resulting FAPbI3 crystals can reach centimeter-scale sizes, after only 24 hours of exposure to ambient air with 43% relative humidity, the XRD pattern shows a distinct δ-phase characteristic peak at 11.8°, exhibiting extremely poor phase stability. This demonstrates that the ring-opening chain-releasing behavior of DVL plays an irreplaceable role in the long-term stability of the crystal.

[0083] Comparative Example 2 The difference between this comparative example and Example 1 is that during the single crystal growth and isothermal treatment stages, the maximum temperature is strictly controlled to not exceed 120°C, that is, the first temperature is 110°C, and then the temperature is only raised to 120°C and held for 2 hours before the reaction ends.

[0084] At temperatures below the ring-opening activation energy of DVL, very small amounts of 5-hydroxyvalerate were detected in the system. FAPbI3 crystals crystallized under these conditions, after aging in the same water-oxygen environment, underwent dissociation and phase transition in approximately 100 hours. This comparative example conversely confirms that long-term crystal stability cannot be achieved solely by relying on the DVL solvent itself; a specific high-temperature triggering of ring-opening is necessary for stabilization.

[0085] Comparative Example 3 The difference between this comparative example and Example 1 is that: the purified 5-hydroxyvalerate and N,N-dimethylformamide (DMF) mixed solution prepared in a volume ratio of 1:5 is used directly as the solvent, the in-situ heating ring-opening step (4) is eliminated, and crystallization is achieved by the solubility difference generated by cooling.

[0086] A high concentration of chain-like 5-hydroxyvalerate exists throughout the system. Due to the strong coordination ability and steric hindrance of the chain molecules, the number of nucleation sites in the solution is greatly increased. Ultimately, only a large number of tiny crystals, or even polycrystalline powders, with sizes ranging from 0.05 to 0.1 cm precipitate in the crystallization flask; centimeter-sized single crystals cannot be grown at all. This demonstrates that the "single chain morphology" severely hinders the macroscopic growth of single crystals.

[0087] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0088] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing centimeter-scale and thermodynamically stable FAPbI3 single crystals, characterized in that, include: Formamidin hydroiodide, lead iodide, and a single solvent containing a compound with a macrocyclic lactone structure are mixed evenly to form a precursor fluid. The precursor liquid is allowed to form crystal nuclei at a first temperature, and then the temperature is raised at a constant rate to a second temperature to keep the macrocyclic lactone compound in a cyclic state, promote crystal growth, and obtain centimeter-sized FAPbI3 single crystals. At the second temperature, isothermal stimulation was used to promote the ring-opening of macrocyclic lactone compounds to generate long-chain hydroxy acid molecules, resulting in centimeter-sized and thermodynamically stable FAPbI3 single crystals.

2. The manufacturing method according to claim 1, characterized in that: The molar concentrations of formamidin hydroiodate and lead iodide in the macrocyclic lactone structure were 0.8~1.8 mol / L and 0.8~1.8 mol / L, respectively. And / or, the macrocyclic lactone structure compound includes δ-valerolactone, γ-valerolactone, etc. At least one of valproic acid and γ-caprolactone; And / or, the long-chain hydroxy acid molecule includes at least one of 5-hydroxyvalerate, 4-hydroxyvalerate, and 4-hydroxyhexanoate.

3. The manufacturing method according to claim 1, characterized in that, Specifically, it includes: Under normal temperature and pressure, formamidin hydroiodide, lead iodide, and a single solvent containing a macrocyclic lactone structure are mixed evenly, and then subjected to ultrasonic treatment for 10-20 minutes to obtain the precursor fluid.

4. The manufacturing method according to claim 3, characterized in that, Specifically, it includes: The precursor liquid is heated to a first temperature of 105-120°C and held at that temperature for 0.5-2 hours to allow crystal nuclei to form. Then, the temperature is uniformly increased to a second temperature of 170-190°C at a rate of 5-15°C / hour. During the uniform heating process, the macrocyclic lactone compound is kept in a cyclic state to obtain the centimeter-sized FAPbI3 single crystal.

5. The manufacturing method according to claim 4, characterized in that, Specifically, it includes: The compound with the macrocyclic lactone structure is kept at the second temperature for 0.5 to 2 hours to promote the ring-opening of the compound to generate long-chain hydroxy acid molecules. Then, it is annealed at 170 to 190°C for 30 to 120 minutes and vacuum dried at 170 to 190°C for 1 to 3 hours to obtain the centimeter-sized and thermodynamically stable FAPbI3 single crystal.

6. A centimeter-sized, thermodynamically stable FAPbI3 single crystal prepared by any one of claims 1-5, characterized in that: The FAPbI3 single crystal has a crystal diameter of 0.5~1.2cm, and it can maintain phase stability for more than 11520 hours under standard solar irradiation and 43% relative humidity.

7. The FAPbI3 single crystal according to claim 6, characterized in that: The FAPbI3 single crystal includes an α phase.

8. A pre-derivatization method for molecular-level recognition of the chemical environment of a mother liquor solution, characterized in that, include: A reaction solution after FAPbI3 single crystal growth as described in claim 6 or 7 is provided, wherein the reaction solution contains the target molecule; The target molecule is derivatized by methylation with boron trifluoride methanol or by silanization with acetamide derivatization reagent, followed by gas chromatography-mass spectrometry analysis, thereby achieving non-destructive separation and identification of the target molecule in the mother liquor chemical environment.

9. The pre-derivation processing method according to claim 8, characterized in that: The target molecule includes 5-hydroxyvalerate; And / or, the volume ratio of the boron trifluoride methanol to the reaction solution is 1:10~50; And / or, the silanized acetamide derivatizing agent includes N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide or N,O-bis(trimethylsilyl)trifluoroacetamide; Preferably, the volume ratio of N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide to the reaction solution is 1:10~50; Preferably, the volume ratio of N,O-bis(trimethylsilyl)trifluoroacetamide to the reaction solution is 1:10~50; And / or, the methyl esterification derivatization treatment is performed at a temperature of 50~70℃ for a time of 20~40 min; And / or, the silanization derivatization treatment is performed at a temperature of 50~70℃ for a time of 20~40 min.

10. The pre-derivation processing method according to claim 9, characterized in that, Specifically, it includes: The 5-hydroxyvalerate is derivatized by using boron trifluoride methanol to convert the hydroxyl and carboxyl groups at both ends of the 5-hydroxyvalerate into methyl ether and methyl ester, respectively. Alternatively, the 5-hydroxyvalerate can be silanized and derivatized using the silanized acetamide derivatizing agent to convert the hydroxyl and carboxyl groups at both ends of the 5-hydroxyvalerate into trimethylsilyl ether and trimethylsilyl ester, respectively.

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